Glossary of acronyms
AAC Atmospheric Action Centres
ACSYS Arctic Climate System Study
AMAP Arctic Monitoring and Assessment Programme
BCC Basal Cell Carcinoma
BRE Building Research Establishment (Watford, UK)
CERN Chinese Ecological Research Network
CSM Climate System Monitoring (Project)
ECN Environmental Change Network (UK)
ENSO El Nino/Soudiern Oscillation
FAO Food and Agriculmre Organisation
FOE Friends of the Earth
GCM General Circulation Model
GCOS Global Climate Observing System
GEMS Global Environmental Monitoring System
GHG Greenhouse Gas(es)
GIS Global Information System
GISS Goddard Institute of Space Studies
GOOS Global Ocean Observing System
IBP International Biological Programme
ICSU • International Council of Scientific Unions
IGBP International Geosphere-Biosphere Programme
IGOSS Integrated Global Ocean Services System
IHP International Hydrological Program
nAASA International Institute for Applied Systems Analysis
ILO International Labour Office
INC Intergovernmental Negotiating Committee
IOC Intergovernmental Oceanographic Commission
IOC International Ozone Commission
IPCC Intergovernmental Panel on Climate Change
LICC Landscape-ecological Impact of Climate Change
MAB Man and the Bioshphere .
MINK Missouri-Iowa-Nebraska-Kansas
OECD Organization for Economic Cooperation and Development
SAT Surface Air Temperature
see Squamous Cell Carcinoma
TEMA Terrestrial Ecosystem Monitoring and Assessment
UNCED United Nations
UNEP United Nations Environment Programme
UNESCO United Nations Educational, Scientific and Cultural Organization
USDOE . United States Department of the Environment
US EPA United States Environmental Protection Authority
US NSF United States
WCDP World Climate Date Programme
WCI World Coal Institute
WCRP World Climate Research Programme
WMO World Meteorological OrganizationGlossary
Aerosols

Airborne particles. The term has also come to be associated, erroneously, with
the propellant used in "aerosol sprays".
Climate change (FCCC usage)
A change of climate which is attributed directly or indirectly to human activity
that alters the composition of the global atmosphere and which is in addition to
natural climate variability observed over comparable time periods.
Climate change (IPCC usage)
Climate change as referred to in the observational record of climate occurs
because of internal changes within the climate system or in the interaction
between its components, or because of changes in external forcing either for
natural reasons or because of human activities. It is generally not possible clearly
to make attribution between these causes. Projections of future climate change
reported by I P C C generally consider only the influence on climate of
anthropogenic increases in greenhouse gases and other human-related factors.
Climate sensitivity
In IPCC reports, climate sensitivity usually refers to the long-term (equilibrium)
change in global mean surface temperature following a doubling of atmospheric
C O j (or equivalent C O 2 ) concentration. More generally, it refers to the
equilibrium change in surface air temperature following a unit change in
radiative forcing (°CAVm~2).
Diurnal temperature range
The difference between maximum and minimum temperature over a period of 24
hours
Equilibrium climate experiment
An experiment where a step change is applied to the forcing of a climate model
and the model is then allowed to reach a new equilibrium. Such experiments
provide information on the difference between the initial and final states of the
model, but not on the time-dependent response.
Equivalent C O j
The concentration of CO^ that would cause the same amount of radiative forcing
as the given mixture of C O j and other greenhouse gases.
Evapotranspiration
The combined process of evaporation from the Earth's surface and transpiration
from vegetation.
Greenhouse gas
A gas that absorbs radiation at specific wavelengths within the spectrum of
radiation (infrared radiation) emitted by the Earth's surface and by clouds. The
gas in turn emits infrared radiation from a level where the temperature is colder
than the surface. The net effect is a local trapping of part of the absorbed energy
and a tendency to warm the planetary surface. Water vapour (HjO), carbon
dioxide (COj), nitrous oxide ( N 2 O ) , methane (CH^) and ozone ( O 3 ) are the
primary greenhouse gases in the Earth's atmosphere.
Ice-cap A dome-shaped glacier usually covering a highland near a water divide.
Ice sheet A glacier more than 50,000 km^ in area forming a continuous cover over a land
surface or resting on a continental shelf.
Radiative forcing A simple measure of the importance of a potential climate change mechanism.
Radiative forcing is the perturbation to the energy balance of the Earth-
atmosphere system (in Wm^^) following, for example, a change in the
concentration of carbon dioxide or a change in the output of the Sun; the climate
system responds to the radiative forcing so as to re-establish the energy balance.
A positive radiative forcing tends to warm the surface and a negative radiative
forcing tends to cool the surface. The radiative forcing is normally quoted as a
global and annual mean value. A more precise definition of radiative forcing, as
used in IPCC reports, is the perturbation of the energy balance of the surface-
troposphere system, after allowing for the sti'atosphere to re-adjust to a state of
global mean radiative equilibrium (see Chapter 4 of IPCC (1994)). Sometimes
called "climate forcing".
Spatial scales continental 10 - 100 million square kilometres (km^)
regional 100 thousand - 10 million km^
local less than 100 thousand km^
Soil moisture Water stored in or at the continental surface and available for evaporation. In
IPCC (1990) a single store (or "bucket") was commonly used in climate models.
Today's models which incorporate canopy and soil processes view soil moisture
as the amount held in excess of plant "wilting point".
Stratosphere The highly stratified and stable region of the atmosphere above the troposphere
{qv.) extending from about 10 km to about 50 km.
Thermohaline circulation Large scale density-driven circulation in the oceans, driven by differences in
temperature and salinity.
Transient climate experiment A n analysis of the time-dependent response of a climate model to a time-varying
change of forcing.
Troposphere The lowest part of the atmosphere from the surface to about 10 km in altitude in
mid-latitudes (ranging from 9 km in high latitudes to 16 km in the tropics on
average) where clouds and "weather" phenomena occur. The troposphere is
defined as the region where temperatures generally decrease with height.
B
Ablation
All processes by which snow and ice are lost from a glacier,
floating ice, or snow cover.
Acclimatization
The physiological adaptation to climatic variations.
Active Layer
The top layer of soil in permafrost that is subjected to
seasonal freezing and thawing.
Adaptability
See adaptive capacity.
Adaptation
Adjustment in natural or human systems in response to actual
or expected climatic s t i m u l i or their effects, which moderates
harm or exploits beneficial opportunities. Various types of
adaptation can be distinguished, including anticipatory and
reactive adaptation, private and public adaptation, and
autonomous and planned adaptation:
– Anticipatory Adaptation—Adaptation that takes
place before impacts of climate change are observed.
Also referred to as proactive adaptation.
– Autonomous Adaptation—Adaptation that does not
constitute a conscious response to climatic stimuli
but is triggered by ecological changes in natural
s y stems and by market or welfare changes in human
systems. Also referred to as spontaneous adaptation.
– Planned Adaptation—Adaptation that is the result of
a deliberate policy decision, based on an awareness
that conditions have changed or are about to change
and that action is required to return to, maintain, or
achieve a desired state.
– Private Adaptation—Adaptation that is initiated and
implemented by individuals, households or private
companies. Private adaptation is usually in the
actor’s rational self-interest.
– Public Adaptation—Adaptation that is initiated and
implemented by governments at all levels. Public
adaptation is usually directed at collective needs.
– Reactive Adaptation—Adaptation that takes place
after impacts of climate change have been observed.
See also adaptation assessment, adaptation benefits,
adaptation costs, adaptive capacity, and maladaptation.
Adaptation Assessment
The practice of identifying options to adapt to climate change
and evaluating them in terms of criteria such as availability,
benefits, costs, effectiveness, efficiency, and feasibility.
Adaptation Benefits
The avoided damage costs or the accrued benefits following
the adoption and implementation of adaptation measures.
Adaptation Costs
Costs of planning, preparing for, facilitating, and implementing
adaptation measures, including transition costs.
Adaptive Capacity
The ability of a system to adjust to climate change ( i n c l u d i n g
climate variability and extremes) to moderate potential
d a mages, to take advantage of opportunities, or to cope with
the consequences.
Aero-Allergens
Allergens present in the air.
Aerosols
Acollection of airborne solid or liquid particles, with a typical
size between 0.01 and 10 mm that reside in the atmosphere
for at least several hours. Aerosols may be of either natural
or anthropogenic origin. Aerosols may influence climate in
two ways: directly through scattering and absorbing radiation,
and indirectly through acting as condensation nuclei for
cloud formation or modifying the optical properties and
l i f etime of clouds.
Afforestation
Planting of new forests on lands that historically have not
contained forests. For a discussion of the term forest and
related terms such as afforestation, reforestation, and
deforestation, see the IPCC Special Report on Land Use,
Land-Use Change, and Forestry (IPCC, 2000).
Aggregate Impacts
Total impacts summed up across sectors and/or regions. The
aggregation of impacts requires knowledge of (or assumptions
about) the relative importance of impacts in different sectors
and regions. Measures of aggregate impacts include, for
example, the total number of people affected, change in net
primary productivity, number of systems undergoing change,
or total economic costs.
Agronomy
The branch of agriculture that deals with the theory and
practice of field-crop production and the scientific
management of soil.
Alases
Coalescing thaw depressions.
Albedo
The fraction of solar radiation reflected by a surface or
object, often expressed as a percentage. Snow-covered
s u rfaces have a high albedo; the albedo of soils ranges from
high to low; vegetation-covered surfaces and oceans have a
low albedo. The Earth’s albedo varies mainly through
v a r ying cloudiness, snow, ice, leaf area, and land-cover
changes.
Algal Blooms
A reproductive explosion of algae in a lake, river, or
ocean.
Alkalinity
A measure of the capacity of water to neutralize acids.

Allergens
Antigenic substances capable of producing immediate-type
hypersensitivity.
Alpine
The biogeographic zone made up of slopes above timberline
and characterized by the presence of rosette-forming herbaceous
plants and low shrubby slow-growing woody plants.
Alternative Risk Transfer
Capital-market alternatives to traditional insurance (e.g.,
c a tastrophe bonds).
Anadromous Species
A species of fish, such as salmon, that spawn in freshwater
then migrate into the ocean to grow to maturity.
Anaerobic
Living, active, or occurring in the absence of free oxygen.
Anoxia
A deficiency of oxygen, especially of such severity as to
result in permanent damage.
Antarctic Bottomwater
A type of water in the seas surrounding Antarctica with
t e mperatures ranging from 0 to -0.8°C, salinities from
.6 to 34.7 PSU, and a density near 27.88. This is the
densest water in the free ocean.
Antarctic Circumpolar Current
A Southern Ocean current that flows around the entire globe
driven by the circumpolar westerlies.
Antarctic Intermediate Water
Created through large-scale cooling and Ekman convergence
in the Southern Ocean.
Anthropogenic
Resulting from or produced by human beings.
AOGCM
See climate model.
Apex Consumers
Organisms at the top of food chains; top predators.
Aquaculture
Breeding and rearing fish, shellfish, etc., or growing plants
for food in special ponds.
Aquifer
Astratum of permeable rock that bears water. An unconfined
aquifer is recharged directly by local rainfall, rivers, and l a k e s ,
and the rate of recharge will be influenced by the permeability
of the overlying rocks and soils. A confined aquifer is
c h a racterized by an overlying bed that is impermeable and
the local rainfall does not influence the aquifer.
Arbovirus
Any of various viruses transmitted by arthropods and
including the causative agents of dengue fever, yellow fever,
and some types of encephalitis.
Arid Regions
Ecosystems with <250 mm precipitation per year.
Autotrophic
Organisms independent of external sources of organic
carbon (compounds) for provision of their own organic
constituents, which they can manufacture entirely from
i n o rganic material. Plants are autotrophic (photoautotrophs)
using the energy of sunlight to produce organic carbon
c o mpounds from inorganic carbon and water in the process
of photosynthesis.
Baseflow
Sustained flow in a river or stream that is primarily produced
by groundwater runoff, delayed subsurface runoff, and/or
lake outflow.
Baseline/Reference
The baseline (or reference) is any datum against which
change is measured. It might be a “current baseline,” in
which case it represents observable, present-day conditions.
It might also be a “future baseline,” which is a projected
future set of conditions excluding the driving factor of
i n t e rest. Alternative interpretations of the reference conditions
can give rise to multiple baselines.
Basin
The drainage area of a stream, river, or lake.
Benthic Organisms
The biota living on, or very near, the bottom of the sea,
river, or lake.
Biodiversity
The numbers and relative abundances of different
genes (genetic diversity), species, and ecosystems
(communities) in a particular area. See also functional
diversity.
Biodiversity Hot Spots
Areas with high concentrations of endemic species facing
extraordinary habitat destruction.
Biofuels
A fuel produced from dry organic matter or combustible oils
produced by plants. Examples of biofuel include alcohol (from
fermented sugar), black liquor from the paper manufacturing
process, wood, and soybean oil.
Biomass
The total mass of living organisms in a given area or
volume; recently dead plant material is often included as
dead biomass.

Biome
A grouping of similar plant and animal communities into
broad landscape units that occur under similar environmental
conditions.
Biosphere
The part of the Earth system comprising all ecosystems and
living organisms in the atmosphere, on land (terrestrial
b i o sphere), or in the oceans (marine biosphere), including
derived dead organic matter, such as litter, soil org a n i c
m a tter, and oceanic detritus.
Biota
All living organisms of an area; the flora and fauna considered
as a unit.
Bog
A poorly drained area rich in accumulated plant material,
frequently surrounding a body of open water and
having a characteristic flora (such as sedges, heaths, and
sphagnum).
Boreal Forest
Forests of pine, spruce, fir, and larch stretching from the
east coast of Canada westward to Alaska and continuing
from Siberia westward across the entire extent of Russia to
the European Plain.
Breakwater
An offshore structure (such as a wall or jetty) that, by
b r e a king the force of the wave, protects a harbor, anchorage,
beach, or shore area.
C3 Plants
Plants that produce a three-carbon compound during
photosynthesis, including most trees and agricultural
crops such as rice, wheat, soybeans, potatoes, and
vegetables.
C4 Plants
Plants that produce a four-carbon compound during
photosynthesis (mainly of tropical origin), including grasses
and the agriculturally important crops maize, sugar cane,
millet, and sorghum.
Carbon Cycle
The term used to describe the flow of carbon (in various
forms, e.g., as in carbon dioxide) through the atmosphere,
ocean, terrestrial biosphere, and lithosphere.
Carbon Dioxide (CO2)
A naturally occurring gas, also a by-product of burning
fossil fuels and biomass, as well as from land-use changes
and other industrial processes. It is the principal
anthropogenic greenhouse gas that affects the Earth’s
radiative balance. It is the reference gas against which other
greenhouse gases are measured and therefore has a Global
Warming Potential of 1.
Carbon Dioxide Fertilization
The enhancement of the growth of plants as a result of
increased atmospheric carbon dioxide concentration.
Depending on their mechanism of photosynthesis, certain
types of plants are more sensitive to changes in atmospheric
CO2 concentration. In particular, C3 plants generally show a
larger response to CO2 than C4 plants.
Carbon Flux
Transfer of carbon from one carbon pool to another in units
of measurement of mass per unit area and time (e.g., t C).
Carrying Capacity
The number of individuals in a population that the resources
of a habitat can support.
Catchment
An area that collects and drains rainwater.
Chagas’Disease
A parasitic disease caused by the Trypanosoma cruzi and
transmitted by triatomine bugs in the Americas, with two
clinical periods: acute (fever, swelling of the spleen, edemas) and
chronic (digestive syndrome, potentially fatal heart condition).
Cholera
An intestinal infection that results in frequent watery stools,
cramping abdominal pain, and eventual collapse from
dehydration.
Climate
Climate in a narrow sense is usually defined as the “average
weather,” or more rigorously, as the statistical description in
terms of the mean and variability of relevant quantities over
a period of time ranging from months to thousands of years.
The classical period is 3 decades, as defined by the World
Meteorological Organization (WMO). These quantities are
most often surface variables such as temperature,
precipitation, and wind. Climate in a wider sense is the s t a t e ,
including a statistical description, of the climate system.
Climate Change
Climate change refers to any change in climate over time,
whether due to natural variability or as a result of human
activity. This usage differs from that in the United Nations
Framework Convention on Climate Change (UNFCCC),
which defines “climate change” as: “a change of climate
which is attributed directly or indirectly to human activity
that alters the composition of the global atmosphere and
which is in addition to natural climate variability observed
over comparable time periods.” See also climate variability.
Climate Model (Hierarchy)
A numerical representation of the climate system based on
the physical, chemical, and biological properties of its
c o mponents, their interactions and feedback processes, and
accounting for all or some of its known properties. T h e
c l imate system can be represented by models of varying

complexity (i.e., for any one component or combination of
components a hierarchy of models can be identified, diff e ring
in such aspects as the number of spatial dimensions; the
extent to which physical, chemical, or biological processes
are explicitly represented; or the level at which empirical
parameterizations are involved. Coupled atmosphere/ocean/
sea-ice General Circulation Models (AOGCMs) provide a
comprehensive representation of the climate system. There
is an evolution towards more complex models with active
chemistry and biology. Climate models are applied, as a
research tool, to study and simulate the climate, but also for
operational purposes, including monthly, seasonal, and
i n t e rannual climate predictions.
Climate Prediction
A climate prediction or climate forecast is the result of an
attempt to produce a most likely description or estimate of
the actual evolution of the climate in the future (e.g., at
s e asonal, interannual, or long-term time scales. See also
c l imate projection and climate scenario.
Climate Projection
Aprojection of the response of the climate system to emission
or concentration scenarios of g reenhouse gases and a e ro s o l s,
or radiative forcing scenarios, often based upon simulations
by climate models. Climate projections are distinguished
from climate predictions in order to emphasize that climate
projections depend upon the emission/concentration/radiative
forcing scenario used, which are based on assumptions,
c o ncerning, for example, future socioeconomic and
technological developments that may or may not be realized
and are therefore subject to substantial uncertainty.
Climate Scenario
A plausible and often simplified representation of the future
c l i m a t e, based on an internally consistent set of climatological
relationships, that has been constructed for explicit use in
investigating the potential consequences of anthropogenic
climate change, often serving as input to impact models.
Climate projections often serve as the raw material for
c o nstructing climate scenarios, but climate scenarios usually
require additional information such as about the observed
current climate. A “climate change scenario” is the diff e rence
between a climate scenario and the current climate.
Climate System
The climate system is the highly complex system consisting
of five major components: the atmosphere, the hydrosphere,
the cryosphere, the land surface, and the biosphere, and the
interactions between them. The climate system evolves in
time under the influence of its own internal dynamics and
because of external forcings such as volcanic eruptions, solar
variations and human-induced forcings such as the changing
composition of the atmosphere and land use.
Climate Variability
Climate variability refers to variations in the mean state and
other statistics (such as standard deviations, the occurrence
of extremes, etc.) of the climate on all temporal and spatial
scales beyond that of individual weather events. Variability
may be due to natural internal processes within the climate
system (internal variability), or to variations in natural or
anthropogenic external forcing (external variability). See
also climate change.
CO2 Fertilization
See carbon dioxide fertilization.
Communicable Disease
An infectious disease caused by transmission of an infective
biological agent (virus, bacterium, protozoan, or multicellular
macroparasite).
Coping Range
The variation in climatic stimuli that a system can absorb
without producing significant impacts.
Coral Bleaching
The paling in color of corals resulting from a loss of symbiotic
algae. Bleaching occurs in response to physiological shock in
response to abrupt changes in temperature, salinity, and turbidity.
Cordillera
An individual mountain chain with closely connected,
distinct summits. In South America, “cordillera” refers to an
individual mountain range.
Cryosphere
The component of the climate system consisting of all snow,
ice, and permafrost on and beneath the surface of the earth
and ocean.
Cryptosporidiosis
An opportunistic infection caused by an intestinal parasite
common in animals. Transmission occurs through ingestion
of food or water contaminated with animal feces. The parasite
causes severe chronic diarrhea, especially in people with HIV.
Deepwater Formation
Occurs when seawater freezes to form sea ice. The local
release of salt and consequent increase in water density
leads to the formation of saline coldwater that sinks to the
ocean floor. See Antarctic bottomwater.
Deforestation
Conversion of forest to non-forest. For a discussion of the
term forest and related terms such as afforestation,
re f o re s t a t i o n, and d e f o re s t a t i o n, see the IPCC Special Report
on Land Use, Land-Use Change, and Fore s t ry (IPCC, 2000).
Dengue Fever
An infectious viral disease spread by mosquitoes, often
called breakbone fever because it is characterized by severe
pain in joints and back. Subsequent infections of the virus
may lead to dengue haemorrhagic fever (DHF) and dengue
shock syndrome (DSS), which may be fatal.

Desert
An ecosystem with <100 mm precipitation per year.
Desertification
Land degradation in arid, semi-arid, and dry sub-humid areas
resulting from various factors, including climatic variations
and human activities. Further, the United Nations
Convention to Combat Desertification (UNCCD) defines
land degradation as a reduction or loss in arid, semi-arid,
and dry sub-humid areas of the biological or economic
p r oductivity and complexity of rain-fed cropland, irrigated
cropland, or range, pasture, forest, and woodlands resulting
from land uses or from a process or combination of
p r o c e s ses, including those arising from human activities and
habitation patterns, such as: (i) soil erosion caused by wind
and/or water; (ii) deterioration of the physical, chemical,
and biological or economic properties of soil; and (iii) longterm
loss of natural vegetation.
Diatom
A class of unicellular algae (Bacillariophyceae) that are
widespread on soil surfaces and in freshwater and marine
systems, especially cold waters of relatively low salinity.
These have cell sizes ranging from 5 to 2000 μm.
Disturbance Regime
Frequency, intensity, and types of disturbances, such as
fires, inspect or pest outbreaks, floods, and droughts.
Diurnal Temperature Range
The difference between the maximum and minimum
temperature during a day.
Downscaling
Reducing the scale of a model from a global to regional level.
Drought
The phenomenon that exists when precipitation has been
significantly below normal recorded levels, causing serious
hydrological imbalances that adversely affect land resource
production systems.
Ecosystem
A distinct system of interacting living organisms, together
with their physical environment. The boundaries of what
could be called an ecosystem are somewhat arbitrary,
depending on the focus of interest or study. Thus the extent
of an ecosystem may range from very small spatial scales
to, ultimately, the entire Earth.
Ecosystem Services
Ecological processes or functions which have value to
individuals or society
Ecotone
Transition area between adjacent ecological communities
(e.g., between forests and grasslands), usually involving
competition between organisms common to both.
Edaphic
Of or relating to the soil; factors inherent in the soil.
Effective Rainfall
The portion of the total rainfall that becomes available for
plant growth.
El Niño-Southern Oscillation (ENSO)
El Niño, in its original sense, is a warmwater current that
periodically flows along the coast of Ecuador and Peru,
d i srupting the local fishery. This oceanic event is associated
with a fluctuation of the intertropical surface pressure pattern
and circulation in the Indian and Pacific Oceans, called the
Southern Oscillation. This coupled atmosphere-ocean
p h enomenon is collectively known as El Niño-Southern
Oscillation. During an El Niño event, the prevailing trade
winds weaken and the equatorial countercurrent strengthens,
causing warm surface waters in the Indonesian area to flow
eastward to overlie the cold waters of the Peru current. This
event has great impact on the wind, sea surface temperature,
and precipitation patterns in the tropical Pacific. It has climatic
effects throughout the Pacific region and in many other
parts of the world. The opposite of an El Niño event is
called La Niña.
Emission Scenario
A plausible representation of the future development of
emissions of substances that are potentially radiatively
active (e.g., g reenhouse gases, a e ro s o l s), based on a
c o h e rent and internally consistent set of assumptions about
driving forces (such as demographic and socioeconomic
development, technological change) and their key
r e l a t i o nships. In 1992, the IPCC presented a set of emission
scenarios that were used as a basis for the climate projections
in the Second Assessment Report (IPCC, 1996). These
emission scenarios are referred to as the IS92 scenarios. In
the IPCC Special Report on Emission Scenarios
(Nakicenovic et al., 2000), new emission scenarios—the
s o -called SRES scenarios—were published.
Endemic
Restricted or peculiar to a locality or region. With regard to
human health, endemic can refer to a disease or agent present
or usually prevalent in a population or geographical area at
all times.
Endorheic Lake
A lake with no outflow; also known as a closed lake.
Enzootic
A disease affecting the animals in an area. It corresponds to
an endemic disease among humans.
Epidemic
Occurring suddenly in numbers clearly in excess of normal
expectancy, said especially of infectious diseases but applied
also to any disease, injury, or other health-related event
occurring in such outbreaks.

Erosion
The process of removal and transport of soil and rock by
weathering, mass wasting, and the action of streams, glaciers,
waves, winds, and underground water.
Eustatic Sea-Level Rise
See sea-level rise.
Eutrophication
The process by which a body of water (often shallow)
becomes (either naturally or by pollution) rich in
dissolved nutrients with a seasonal deficiency in dissolved
oxygen.
Evaporation
The process by which a liquid becomes a gas.
Evapotranspiration
The combined process of e v a p o r a t i o n from the Earth’s surface
and transpiration from vegetation.
Exoheic Lake
A lake drained by outflowing rivers.
Exotic Species
See introduced species.
Exposure
The nature and degree to which a system is exposed to
s i gnificant climatic variations.
Exposure Unit
An activity, group, region, or resource that is subjected to
climatic stimuli.
Externalities
By-products of activities that affect the well-being of people
or the environment, where those impacts are not reflected in
market prices. The costs (or benefits) associated with
externalities do not enter cost-accounting schemes.
Extinction
The complete disappearance of an entire species.
Extirpation
The disappearance of a species from part of its range; local
extinction.
Extreme Weather Event
An event that is rare within its statistical reference distribution
at a particular place. Definitions of “rare” vary, but an
extreme weather event would normally be as rare as or
rarer than the 10th or 90th percentile. By definition, the
characteristics of what is called “extreme weather” may
vary from place to place. An “extreme climate event” is an
average of a number of weather events over a certain period
of time, an average which is itself extreme (e.g., rainfall
over a season).
Extrinsic Incubation Period
In blood-feeding anthropod vectors, the time between
a c q u isition of the infectious blood meal and the time when
the anthropod becomes capable of transmitting the agent. In
the case of malaria, the life stages of the plasmodium parasite
spent within the female mosquito vector (i.e., outside the
human host).
Feedback
A process that triggers changes in a second process that in
turn influences the original one; a positive feedback
i n t e n s ifies the original process, and a negative feedback
reduces it.
Fen
Low land covered wholly or partly with water unless
artificially drained.
Fiber
Wood, fuelwood (either woody or non-woody).
Food Insecurity
A situation that exists when people lack secure access to
sufficient amounts of safe and nutritious food for normal
growth and development and an active and healthy life. It
may be caused by the unavailability of food, insufficient
purchasing power, inappropriate distribution, or inadequate
use of food at the household level. Food insecurity may be
chronic, seasonal, or transitory.
Forecast
See climate prediction and climate projection.
Forest
A vegetation type dominated by trees. Many definitions of
the term forest are in use throughout the world, reflecting
wide differences in biogeophysical conditions, social structure,
and economics. For a discussion of the term f o re s t and related
terms such as afforestation, reforestation, and deforestation,
see the IPCC Special Report on Land Use, Land-Use
Change, and Forestry (IPCC, 2000).
Freshwater Lens
Alenticular fresh groundwater body that underlies an oceanic
island. It is underlain by saline water.
Functional Diversity
The number of functionally different organisms in an
ecosystem (also referred to as “functional types” and
“ f u n ctional groups”).
General Circulation Model (GCM)
See climate model.
General Equilibrium Analysis
An approach that considers simultaneously all the markets
in an economy, allowing for feedback effects between
i n d ividual markets.

Geomorphic
Pertaining to the form of the Earth or its surface features.
Glacier
Amass of land ice flowing downhill (by internal deformation
and sliding at the base) and constrained by the surrounding
topography (e.g., the sides of a valley or surrounding
peaks); the bedrock topography is the major influence on
the dynamics and surface slope of a glacier. A glacier is
maintained by accumulation of snow at high altitudes,
b a lanced by melting at low altitudes or discharge into the
sea.
Greenhouse Effect
Greenhouse gases effectively absorb infrared radiation
e m i tted by the Earth’s surface, by the atmosphere itself due
to the same gases, and by clouds. Atmospheric radiation is
emitted to all sides, including downward to the Earth’s
s u rface. Thus greenhouse gases trap heat within the surfacetroposphere
system. This is called the “natural greenhouse
effect.” Atmospheric radiation is strongly coupled to the
temperature of the level at which it is emitted. In the
troposphere, the temperature generally decreases with height.
Effectively, infrared radiation emitted to space originates
from an altitude with a temperature of on average -19°C,
in balance with the net incoming solar radiation, whereas
the Earth’s surface is kept at a much higher temperature of
on average 14°C. An increase in the concentration of
g r e e nhouse gases leads to an increased infrared opacity of
the atmosphere, and therefore to an effective radiation into
space from a higher altitude at a lower temperature. This
causes a radiative forcing, an imbalance that can only be
compensated for by an increase of the temperature of the
surface-troposphere system. This is called the “enhanced
greenhouse effect.”
Greenhouse Gas
Greenhouse gases are those gaseous constituents of the
atmosphere, both natural and anthropogenic, that absorb and
emit radiation at specific wavelengths within the spectrum
of infrared radiation emitted by the Earth’s surface, the
atmosphere, and clouds. This property causes the g re e nhouse
effect. Water vapor (H2O), carbon dioxide (CO2), nitrous
oxide (N2O), methane (CH4), and ozone (O3) are the primary
greenhouse gases in the Earth’s atmosphere. Moreover, there
are a number of entirely human-made greenhouse gases in
the atmosphere, such as the halocarbons and other chlorineand
bromine-containing substances which are dealt with
under the Montreal Protocol. Beside CO2, N2O, and CH4,
the Kyoto Protocol deals with the greenhouse gases sulfur
hexaflouride (SF6), hydrofluorocarbons (HFCs) and
perfluorocarbons (PFCs).
Groin
A l o w, narrow jetty, usually extending roughly perpendicular
to the shoreline, designed to protect the shore from erosion
by currents, tides, or waves, or to trap sand for the purpose
of building up or making a beach.
Gross Primary Production
The amount of carbon fixed from the atmosphere through
photosynthesis.
Groundwater Recharge
The process by which external water is added to the zone of
saturation of an aquifer, either directly into a formation or
indirectly by way of another formation.
Habitat
The particular environment or place where an organism or
species tends to live; a more locally circumscribed portion
of the total environment.
Halocline
Alayer in the ocean in which the rate of salinity variation with
depth is much larger than layers immediately above or below it.
Hantavirus
A virus in the family Bunyaviridae that causes a type of
haemorrhagic fever. It is thought that humans catch the
d i sease mainly from infected rodents, either through direct
contact with the animals or by inhaling or ingesting dust
that contains their dried urine.
Heath
Any of the various low-growing shrubby plants of open
wastelands, usually growing on acidic, poorly drained soils.
Heat Island
An area within an urban area characterized by ambient
t e mperatures higher than those of the surrounding area because
of the absorption of solar energy by materials like asphalt.
Herbaceous
Flowering, non-woody plants.
Heterotrophic Respiration
The release of CO2 from decomposition of organic matter.
Highland Malaria
Malaria that occurs around the altitudinal limits of its
distribution.
Human Settlement
A place or area occupied by settlers.
Human System
Any system in which human organizations play a major
role. Often, but not always, the term is synonymous with
“society” or “social system” (e.g., agricultural system, political
system, technological system, economic system); all are
human systems in the sense applied in the TAR.
Hypolimnion
The part of a lake below the thermocline made up of water
that is stagnant and of essentially uniform temperature
except during the period of overturn.

Ice Cap
A dome-shaped ice mass covering a highland area that is
considerably smaller in extent than ice sheets.
Ice Jam
An accumulation of broken river or sea ice caught in a narrow
channel.
Ice Sheet
A mass of land ice which is sufficiently deep to cover most
of the underlying bedrock topography, so that its shape is
mainly determined by its internal dynamics (the flow of the
ice as it deforms internally and slides at its base). An ice
sheet flows outwards from a high central plateau with a
small average surface slope. The margins slope steeply, and
the ice is discharged through fast-flowing ice streams or
outlet glaciers, in some cases into the sea or into ice shelves
floating on the sea. There are only two large ice sheets in
the modern world—on Greenland and Antarctica, the
Antarctic ice sheet being divided into east and west by the
Transantarctic Mountains; during glacial periods there were
others.
Ice Shelf
A floating ice sheet of considerable thickness attached to a
coast (usually of great horizontal extent with a level or
g e ntly undulating surface); often a seaward extension of ice
sheets.
Immunosuppression
Reduced functioning of an individual’s immune system.
(Climate) Impact Assessment
The practice of identifying and evaluating the detrimental
and beneficial consequences of climate change on natural
and human systems.
(Climate) Impacts
Consequences of climate change on natural and human
s y stems. Depending on the consideration of adaptation, one
can distinguish between potential impacts and residual impacts.
– Potential Impacts—All impacts that may occur given
a projected change in climate, without considering
adaptation.
– Residual Impacts—The impacts of climate change
that would occur after adaptation.
See also a g g regate impacts, market impacts, and n o n - m a rket
impacts.
Indigenous Peoples
People whose ancestors inhabited a place or a country when
persons from another culture or ethnic background arrived
on the scene and dominated them through conquest,
settlement, or other means and who today live more in
conformity with their own social, economic, and cultural
customs and traditions than those of the country of which they
now form a part (also referred to as “native,” “aboriginal,” or
“tribal” peoples)
Industrial Revolution
A period of rapid industrial growth with far-reaching social
and economic consequences, beginning in England during
the second half of the 18th century and spreading to Europe
and later to other countries including the United States. The
industrial revolution marks the beginning of a strong increase
in the use of fossil fuels and emission of in particular fossil
carbon dioxide. In the TAR, the terms “pre-industrial” and
“industrial” refer, somewhat arbitrarily, to the periods before
and after 1750, respectively.
Infectious Diseases
Any disease that can be transmitted from one person to
a n o t h e r. This may occur by direct physical contact, by
c o mmon handling of an object that has picked up infective
o rganisms, through a disease carrier, or by spread of infected
droplets coughed or exhaled into the air.
Infrastructure
The basic equipment, utilities, productive enterprises,
i n s t a llations, and services essential for the development,
operation, and growth of an organization, city, or nation.
Insolvency
Inability to meet financial obligations; bankruptcy.
Integrated Assessment
A method of analysis that combines results and models from
the physical, biological, economic, and social sciences, and
the interactions between these components, in a consistent
framework to evaluate the status and the consequences of
environmental change and the policy responses to it.
Introduced Species
A species occurring in an area outside its historically known
natural range as a result of accidental dispersal by humans
(also referred to as “exotic species” or “alien species”).
Invasive Species
An introduced species that invades natural habitats.
Keystone Species
A species that has a central servicing role affecting many
other organisms and whose demise is likely to result in the
loss of a number of species and lead to major changes in
ecosystem function.
Kyoto Protocol
The Kyoto Protocol was adopted at the Third Session of the
Conference of the Parties (COP) to the UN Framework
Convention on Climate Change (UNFCCC) in 1997 in
Kyoto, Japan. It contains legally binding commitments, in
addition to those included in the UNFCCC. Countries included
in Annex B of the Protocol (most OECD countries and
EITs) agreed to reduce their anthropogenic GHG emissions
( C O2, CH4, N2O, HFCs, PFCs, and SF6) by at least 5% below
levels in the commitment period 2008 to 2012. The
Kyoto Protocol has not yet entered into force (as of June 2001).

La Niña
See El Niño-Southern Oscillation (ENSO).
Land Use
The total of arrangements, activities, and inputs undertaken
in a certain land-cover type (a set of human actions). The
social and economic purposes for which land is managed
(e.g., grazing, timber extraction, conservation).
Landslide
A mass of material that has slipped downhill by gravity,
often assisted by water when the material is saturated; rapid
movement of a mass of soil, rock, or debris down a slope.
Large-Scale Singularities
Abrupt and dramatic changes in systems in response to
smooth changes in driving forces. For example, a gradual
increase in atmospheric greenhouse gas concentrations may
lead to such large-scale singularities as slowdown or collapse
of the thermohaline circulation or collapse of the West
Antarctic Ice Sheet. The occurrence, magnitude, and timing
of large-scale singularities are difficult to predict.
Leaching
The removal of soil elements or applied chemicals through
percolation.
Legume
Plants that are able to fix nitrogen from the air through a
symbiotic relationship with soil bacteria (e.g., peas, beans,
alfalfa, clovers).
Limnology
Study of lakes and their biota.
Littoral Zone
A coastal region; the shore zone between high and low
watermarks.
Local Agenda 21
Local Agenda 21s are the local plans for environment and
development that each local authority is meant to develop
through a consultative process with their populations, with
particular attention paid to involving women and youth.
Many local authorities have developed Local Agenda 21s
through consultative processes as a means of reorienting
their policies, plans, and operations towards the achievement
of sustainable development goals. The term comes from
Chapter 28 of Agenda 21—the document formally endorsed
by all government representatives attending the UN
Conference on Environment and Development (also known
as the Earth Summit) in Rio de Janeiro in 1992.
Maladaptation
Any changes in natural or human systems that inadvertently
increase vulnerability to climatic stimuli; an adaptation that
does not succeed in reducing vulnerability but increases it
instead.
Malaria
Endemic or epidemic parasitic disease caused by species of
the genus Plasmodium (protozoa) and transmitted by
mosquitoes of the genus Anopheles; produces high fever
attacks and systemic disorders, and kills approximately
million people every year.
Market Impacts
Impacts that are linked to market transactions and directly
affect gross domestic product (GDP, a country’s national
accounts)—for example, changes in the supply and price of
agricultural goods. See also non-market impacts.
Mass Movement
Applies to all unit movements of land material propelled
and controlled by gravity.
Meningitis
Inflammation of the meninges (part of the covering of the
brain).
Metazoan
An animal whose body consists of many cells. See also
protozoan
Microbial Loop
Complex food web involving bacteria, single-celled animals
and plants, viruses, and dissolved and particulate organic
material. Dissolved and particulate material, released from
o rganisms, is utilized by bacteria, which are grazed by
p r otozoa which in turn are grazed by metazoa. Around 50%
(often more) of primary production passes through the
microbial loop rather than along the classical food chain of
phytoplankton to herbivore.
Microclimate
Local climate at or near the Earth’s surface. See also
climate.
Mitigation
An anthropogenic intervention to reduce the sources or
enhance the sinks of greenhouse gases.
Mixed Layer
The upper region of the ocean well-mixed by interaction
with the overlying atmosphere.
Monsoon
Wind in the general atmospheric circulation typified
by a seasonal persistent wind direction and by a
pronounced change in direction from one season to the
next.
Montane
The biogeographic zone made up of relatively moist, cool
upland slopes below timberline and characterized by the
presence of large evergreen trees as a dominant life
form.

Montreal Protocol
The Montreal Protocol on Substances that Deplete the Ozone
Layer was adopted in Montreal in 1987, and subsequently
adjusted and amended in London (1990), Copenhagen
(1992), Vienna (1995), Montreal (1997), and Beijing (1999).
It controls the consumption and production of chlorine- and
bromine-containing chemicals that destroy stratospheric o z o n e,
such as CFCs, methyl chloroform, carbon tetrachloride, and
many others.
Morbidity
Rate of occurrence of disease or other health disorder within
a population, taking account of the age-specific morbidity
rates. Health outcomes include chronic disease incidence/
prevalence, rates of hospitalization, primary care consultations,
disability-days (i.e., days when absent from work), and
prevalence of symptoms.
Morphology
The form and structure of an organism or any of its parts.
Mortality
Rate of occurrence of death within a population within a
specified time period; calculation of mortality takes
account of age-specific death rates, and can thus yield
measures of life expectancy and the extent of premature
death.
Nanoplankton
Phytoplankton whose lengths range from 10-50 μm.
Net Biome Production (NBP)
Net gain or loss of carbon from a region. NBP is equal to
Net Ecosystem Production minus the carbon lost due to a
disturbance (e.g., a forest fire or a forest harvest).
Net Ecosystem Production (NEP)
Net gain or loss of carbon from an ecosystem. NEP is equal
to Net Primary Production minus the carbon lost through
heterotrophic respiration.
Net Primary Production (NPP)
The increase in plant biomass or carbon of a unit of a
l a n dscape. NPP is equal to Gross Primary Production minus
carbon lost through autotrophic respiration.
Nitrogen Oxides (NOx)
Any of several oxides of nitrogen.
Non-Linearity
A process is called “non-linear” when there is no simple
proportional relation between cause and effect.
Non-Market Impacts
Impacts that affect ecosystems or human welfare, but that
are not directly linked to market transactions—for example,
an increased risk of premature death. See also market
impacts.
Non-Point-Source Pollution
Pollution from sources that cannot be defined as discrete
points, such as areas of crop production, timber, surface
mining, disposal of refuse, and construction. See also pointsource
pollution.
No Regrets Policy
One that would generate net social benefits whether or not
there is anthropogenic climate change.
North Atlantic Oscillation (NAO)
The North Atlantic Oscillation consists of opposing variations
of barometric pressure near Iceland and near the Azores. It
is the dominant mode of winter climate variability in the
North Atlantic region ranging from central North America to
Europe.
Obligate Species
Species restricted to one particularly characteristic mode of
life.
Ocean Conveyor Belt
The theoretical route by which water circulates around the
entire global ocean, driven by wind and the thermohaline
circulation.
Ocean Ventilation
Downwelling of water from near the surface to the deep
ocean. See also deepwater formation.
Oligotrophic
Relatively unproductive areas of the sea, lakes, and rivers
with low nutrient content. See also eutrophic.
Opportunity Costs
The cost of an economic activity forgone by the choice of
another activity.
Orography
The study of the physical geography of mountains and
mountain systems.
Ozone
Ozone, the triatomic form of oxygen (O3), is a gaseous
atmospheric constituent. In the troposphere, it is created
both naturally and by photochemical reactions involving
gases resulting from human activities (photochemical
smog). In high concentrations, tropospheric ozone can be
harmful to a wide-range of living organisms. Tropospheric
ozone acts as a g reenhouse gas. In the stratosphere, ozone
is created by the interaction between solar ultraviolet
r a d i ation and molecular oxygen (O2). Stratospheric
ozone plays a decisive role in the stratospheric
radiative balance. Depletion of stratospheric
ozone, due to chemical reactions that may be enhanced
by climate change, results in an increased ground-level
flux of ultraviolet (UV-) B radiation. See also Montreal
Protocol.

Particulates
Very small solid exhaust particles emitted during the
combustion of fossil and biomass fuels. Particulates may
consist of a wide variety of substances. Of greatest concern
for health are particulates of less than or equal to 10 nm in
diameter, usually designated as PM10.
Peat
Unconsolidated soil material consisting largely of partially
decomposed organic matter accumulated under conditions
of excess moisture or other conditions that decrease
decomposition rates.
Pelagic
Of, relating to, or living or occurring in the open sea.
Permafrost
Perennially frozen ground that occurs wherever the
temperature remains below 0°C for several years.
Phenology
The study of natural phenomena that recur periodically
(e.g., blooming, migrating) and their relation to climate and
seasonal changes.
Photic Zone
The upper waters of lakes, rivers, and sea sufficiently
illuminated for photosynthesis to occur.
Photochemical Smog
A mix of photochemical oxidant air pollutants produced by
the reaction of sunlight with primary air pollutants, especially
hydrocarbons.
Photosynthate
The product of photosynthesis.
Photosynthesis
The process by which plants take carbon dioxide from the
air (or bicarbonate in water) to build carbohydrates,
releasing oxygen in the process. There are several pathways
of photosynthesis with different responses to atmospheric
CO2 concentrations. See also CO2 fertilization, C3 plants,
and C4 plants.
Physiographic
Of, relating to, or employing a description of nature or
n a tural phenomena.
Phytophagous Insects
Insects that feed on plants.
Phytoplankton
The plant forms of plankton (e.g., diatoms). Phytoplankton
are the dominant plants in the sea, and are the bast of the
entire marine food web. These single-celled organisms are
the principal agents for photosynthetic carbon fixation in the
ocean. See also zooplankton.
Plankton
Aquatic organisms that drift or swim weakly. See also
phytoplankton and zooplankton.
Point-Source Pollution
Pollution resulting from any confined, discrete source, such
as a pipe, ditch, tunnel, well, container, concentrated animalfeeding
operation, or floating craft. See also n o n - p o i n t - s o u rc e
pollution.
Polynyas
Areas of open water in pack ice or sea ice.
Pool
See reservoir.
Potential Production
Estimated production of a crop under conditions when
n u t r ients and water are available at optimum levels for plant
growth and development; other conditions such as day
length, temperature, soil characteristics, etc., determined by
site characteristics.
Pre-Industrial
See Industrial Revolution.
Primary Energy
Energy embodied in natural resources (e.g., coal, crude oil,
sunlight, uranium) that has not undergone any a n t h ropogenic
conversion or transformation.
Producer Surplus
Returns beyond the cost of production that provide
compensation for owners of skills or assets that are scarce
(e.g., agriculturally productive land).
Projection (Generic)
A projection is a potential future evolution of a quality or
set of quantities, often computed with the aid of a model.
Projections are distinguished from predictions in order to
emphasize that projections involve assumptions—concerning,
for example, future socioeconomic and technological
developments that may or may not be realized—and are
therefore subject to substantial uncertainty. See also climate
projection and climate prediction.
Protozoan
A single-celled animal.
Radiative Forcing
Radiative forcing is the change in the net vertical irradiance
[expressed in Watts per square meter (Wm-2)] at the
tropopause due to an internal change or a change in the
external forcing of the climate system, such as a change in
the concentration of CO2 or the output of the Sun. Usually
radiative forcing is computed after allowing for stratospheric
temperatures to readjust to radiative equilibrium, but with all
tropospheric properties held fixed at their unperturbed values.

Rangeland
Unimproved grasslands, shrublands, savannas, and tundra.
Reference Scenario
See baseline/reference.
Reforestation
Planting of forests on lands that have previously contained
forests but that have been converted to some other use. For
a discussion of the term forest and related terms such as
afforestation, reforestation, and deforestation, see the IPCC
Special Report on Land Use, Land-Use Change, and
Forestry (IPCC, 2000).
Regeneration
The renewal of a stand of trees through either natural means
(seeded onsite or adjacent stands or deposited by wind,
birds, or animals) or artificial means (by planting seedlings
or direct seeding).
Reinsurance
The transfer of a portion of primary insurance risks to a
s e condary tier of insurers (reinsurers); essentially “insurance
for insurers.”
Reservoir
Acomponent of the climate system, other than the atmosphere,
that has the capacity to store, accumulate, or release a substance
of concern (e.g., carbon, a greenhouse gas, or precursor).
Oceans, soils, and f o re s t s are examples of reservoirs of carbon.
“Pool” is an equivalent term (note that the definition of pool
often includes the atmosphere). The absolute quantity of
substances of concern held within a reservoir at a specified
time is called the “stock.” The term also means an artificial
or natural storage place for water, such as a lake, pond, or
aquifer, from which the water may be withdrawn for such
purposes as irrigation, water supply, or irrigation.
Reservoir Host
Any animal, plant, soil, or inanimate matter in which a
pathogen normally lives and multiplies, and on which it
depends primarily for survival (e.g., foxes are a reservoir for
rabies). Reservoir hosts may be asymptomatic.
Resilience
Amount of change a system can undergo without changing state.
Respiration
The process whereby living organisms convert organic matter
to carbon dioxide, releasing energy and consuming oxygen.
Riparian
Relating to or living or located on the bank of a natural
watercourse (as a river) or sometimes of a lake or a tidewater.
Runoff
That part of precipitation that does not evaporate. In some
countries, runoff implies surface runoff only.
Salinization
The accumulation of salts in soils.
Saltwater Intrusion/Encroachment
Displacement of fresh surface water or groundwater by the
advance of saltwater due to its greater density, usually in
coastal and estuarine areas.
Scenario (Generic)
A plausible and often simplified description of how the
future may develop, based on a coherent and internally
c o nsistent set of assumptions about driving forces and key
relationships. Scenarios may be derived from projections,
but are often based on additional information from other
sources, sometimes combined with a “narrative storyline.”
See also climate scenario and emissions scenario.
Sea-Level Rise
An increase in the mean level of the ocean. Eustatic sea-level
rise is a change in global average sea level brought about by
an alteration to the volume of the world ocean. Relative sealevel
rise occurs where there is a net increase in the level of
the ocean relative to local land movements. Climate modelers
largely concentrate on estimating eustatic sea-level change.
Impact researchers focus on relative sea-level change.
Seawall
Ahuman-made wall or embankment along a shore to prevent
wave erosion.
Semi-Arid Regions
Ecosystems that have >250 mm precipitation per year, but
are not highly productive; usually classified as rangelands.
Sensitivity
Sensitivity is the degree to which a system is affected, either
adversely or beneficially, by climate-related stimuli. The
effect may be direct (e.g., a change in crop yield in response
to a change in the mean, range, or variability of temperature)
or indirect (e.g., damages caused by an increase in the
frequency of coastal flooding due to sea level rise).
Sequestration
The process of increasing the carbon content of a carbon
pool other than the atmosphere.
Silt
Unconsolidated or loose sedimentary material whose
constituent rock particles are finer than grains of sand and
larger than clay particles.
Silviculture
Development and care of forests.
Sink
Any process, activity, or mechanism that removes a
greenhouse gas, an aerosol, or a precursor of a greenhouse
gas or aerosol from the atmosphere.

Snowpacks
A seasonal accumulation of slow-melting snow.
Soil Carbon Pool
Refers to the relevant carbon in the soil. It includes various
forms of soil organic carbon (humus) and inorganic soil
c a rbon and charcoat. It excludes soil biomass (e.g., roots,
bulbs, etc.) as well as the soil fauna (animals).
Source
Any process, activity, or mechanism that releases a
greenhouse gas, an aerosol, or a precursor of a greenhouse
gas or aerosol into the atmosphere.
Southern Oscillation
A l a rge-scale atmospheric and hydrospheric fluctuation
c e ntered in the equatorial Pacific Ocean, exhibiting a pressure
anomaly, alternatively high over the Indian Ocean and high
over the South Pacific. Its period is slightly variable, averaging
.33 years. The variation in pressure is accompanied by
variations in wind strengths, ocean currents, sea-surface
temperatures, and precipitation in the surrounding areas.
Stakeholders
Person or entity holding grants, concessions, or any other type
of value that would be affected by a particular action or policy.
Stimuli (Climate-Related)
All the elements of climate change, including mean climate
characteristics, climate variability, and the frequency and
magnitude of extremes.
Stochastic Events
Events involving a random variable, chance, or probability.
Stock
See reservoir.
Stratosphere
Highly stratified region of atmosphere above the t ro p o s p h e re
extending from about 10 km (ranging from 9 km in high
l a titudes to 16 km in the tropics on average) to about 50 km.
Streamflow
Water within a river channel, usually expressed in m3 sec-1.
Sub-Antarctic Mode Water (SAMW)
A type of water in the Sub-Antarctic Zone of the Southern
Ocean. The SAMW is the deep surface layer of water with
uniform temperature and salinity created by convective
processes in the winter. It can be identified by a temperature
of around -1.8°C and a salinity of around 34.4 PSU, and is
separated from the overlying surface water by a halocline at
around 50 m in the summer. Although it is not considered to
be a water mass, it contributes to the Central Water of the
Southern Hemisphere, and is additionally responsible for the
formation of Antarctic Intermediate Water in the eastern part
of the South Pacific Ocean. It is also known as Winter Wa t e r.
Submergence
A rise in the water level in relation to the land, so that areas
of formerly dry land become inundated; it results either
from a sinking of the land or from a rise of the water level.
Subsidence
The sudden sinking or gradual downward settling of the
Earth’s surface with little or no horizontal motion.
Succession
Transition in the composition of plant communities following
disturbance.
Surface Runoff
The water that travels over the soil surface to the nearest
surface stream; runoff of a drainage basin that has not
passed beneath the surface since precipitation.
Sustainable Development
Development that meets the needs of the present without
compromising the ability of future generations to meet their
own needs.
Synoptic
Relating to or displaying atmospheric and weather conditions
as they exist simultaneously over a broad area.
Taiga
Coniferous forests of northern North America and Eurasia.
Thermal Erosion
The erosion of ice-rich permafrost by the combined thermal
and mechanical action of moving water.
Thermal Expansion
In connection with sea-level rise, this refers to the increase
in volume (and decrease in density) that results from warming
water.A warming of the ocean leads to an expansion of the
ocean volume and hence an increase in sea level.
Thermocline
The region in the world’s ocean, typically at a depth of
km, where temperature decreases rapidly with depth and
which marks the boundary between the surface and the
ocean.
Thermohaline Circulation
Large-scale density-driven circulation in the ocean, caused
by differences in temperature and salinity. In the North
Atlantic, the thermohaline circulation consists of warm
s u rface water flowing northward and cold deepwater flowing
southward, resulting in a net poleward transport of heat. The
surface water sinks in highly restricted sinking regions
located in high latitudes.
Thermokarst
Irregular, hummocky topography in frozen ground caused
by melting of ice.

Timberline
The upper limit of tree growth in mountains or high latitudes.
Transpiration
The emission of water vapor from the surfaces of leaves or
other plant parts.
Troposphere
The lowest part of the atmosphere from the surface to about
km in altitude in mid-latitudes (ranging from 9 km in
high latitudes to 16 km in the tropics on average) where
clouds and “weather” phenomena occur. In the troposphere,
temperatures generally decrease with height.
Tsunami
A large tidal wave produced by a submarine earthquake,
landslide, or volcanic eruption.
Tundra
A treeless, level, or gently undulating plain characteristic of
arctic and subarctic regions.
Ultraviolet (UV)-B Radiation
Solar radiation within a wavelength range of 280–320 nm,
the greater part of which is absorbed by stratospheric ozone.
Enhanced UV-B radiation suppresses the immune system
and can have other adverse effects on living organisms.
Uncertainty
An expression of the degree to which a value (e.g., the
future state of the climate system) is unknown. Uncertainty
can result from lack of information or from disagreement
about what is known or even knowable. It may have many
types of sources, from quantifiable errors in the data to
ambiguously defined concepts or terminology, or uncertain
projections of human behavior. Uncertainty can therefore be
represented by quantitative measures (e.g., a range of values
calculated by various models) or by qualitative statements
(e.g., reflecting the judgment of a team of experts).
Undernutrition
The result of food intake that is insufficient to meet dietary
energy requirements continuously, poor absorption, and/or
poor biological use of nutrients consumed.
Unique and Threatened Systems
Entities that are confined to a relatively narrow geographical
range but can affect other, often larger entities beyond their
range; narrow geographical range points to sensitivity to
environmental variables, including climate, and therefore
attests to potential vulnerability to climate change.
United Nations Framework Convention
on Climate Change (UNFCCC)
The Convention was adopted on 9 May 1992, in New York,
and signed at the 1992 Earth Summit in Rio de Janeiro by
more than 150 countries and the European Community. Its
ultimate objective is the “stabilization of greenhouse gas
concentrations in the atmosphere at a level that would prevent
dangerous anthropogenic interference with the climate
system.” It contains commitments for all Parties. Under the
Convention, Parties included in Annex I aim to return
g r e e nhouse gas emissions not controlled by the Montreal
Protocol to 1990 levels by the year 2000. The Convention
entered in force in March 1994. See also Kyoto Protocol.
Ungulate
Ahoofed, typically herbivorous, quadruped mammal (such as
a ruminant, swine, camel, hippopotamus, horse, rhinoceros,
or elephant).
Upwelling
Transport of deeper water to the surface, usually caused by
horizontal movements of surface water.
Urbanization
The conversion of land from a natural state or managed
n a tural state (such as agriculture) to cities; a process driven
by net rural-to-urban migration through which an increasing
percentage of the population in any nation or region come to
live in settlements that are defined as “urban centers.”
Vector
An organism, such as an insect, that transmits a pathogen
from one host to another. See also vector-borne diseases and
vectorial capacity.
Vector-Borne Diseases
Disease that is transmitted between hosts by a v e c t o r o rg a nism
(such as a mosquito or tick— for example, malaria, dengue
fever, and leishmaniasis.
Vectorial Capacity
Quantitative term used in the study of the transmission
dynamics of malaria to express the average number of
potentially infective bites of all vectors feeding upon one
host in one day, or the number of new inoculations with a
vector-borne disease transmitted by one vector species from
one infective host in one day.
Vernalization
The act or process of hastening the flowering and fruiting of
plants by treating seeds, bulbs, or seedlings so as to induce a
shortening of the vegetative period.
Vulnerability
The degree to which a system is susceptible to, or unable to
cope with, adverse effects of climate change, including climate
variability and extremes. Vulnerability is a function of the
character, magnitude, and rate of climate variation to which
a system is exposed, its sensitivity, and its adaptive capacity.
Water Consumption
Amount of extracted water irretrievably lost at a given territory
during it’s use (evaporation and goods production). Water
consumption is equal to water withdrawal minus return flow.


Water Stress
Acountry is water stressed if the available freshwater supply
relative to water withdrawals acts as an important constraint
on development. Withdrawals exceeding 20% of renewable
water supply has been used as an indicator of water stress.
Water Withdrawal
Amount of water extracted from water bodies.
Water Use Efficiency
Carbon gain in photosynthesis per unit water lost in
evapotranspiration. It can be expressed on a short-term basis
as the ratio of photosynthetic carbon gain per unit
transpirational water loss, or on a seasonal basis as the ratio
of net primary production or agricultural yield to the
amount of available water.
Xeric
Requiring only a small amount of moisture.
Zoonosis
The transmission of a disease from an animal or nonhuman
species to humans. The natural reservoir is a nonhuman
a n imal.
Zooplankton
The animal forms of plankton. They consume phytoplankton
or other zooplankton. See also phytoplankton.

Annex B. Glossary of Terms
This Glossary is based on the glossaries published in the IPCC
Third Assessment Report (IPCC, 2001a,b,c); however, additional
work has been undertaken on consistency and refinement of
some of the terms. The terms that are independent entries in
this glossary are highlighted in italics.
Acclimatization
The physiological adaptation to climatic variations.
Activities Implemented Jointly (AIJ)
The pilot phase for Joint Implementation, as defined in Article
.2(a) of the United Nations Framework Convention on
Climate Change, that allows for project activity among
developed countries (and their companies) and between
developed and developing countries (and their companies).
AIJ is intended to allow Parties to the United Nations
Framework Convention on Climate Change to gain experience
in jointly implemented project activities. There is no crediting
for AIJ activity during the pilot phase. A decision remains to
be taken on the future of AIJ projects and how they may relate
to the Kyoto Mechanisms. As a simple form of tradable permits,
AIJ and other market-based schemes represent important
potential mechanisms for stimulating additional resource flows
for the global environmental good. See also Clean
Development Mechanism and emissions trading.
Adaptability
See Adaptive capacity.
Adaptation
Adjustment in natural or human systems to a new or changing
environment. Adaptation to climate change refers to
adjustment in natural or human systems in response to actual
or expected climatic stimuli or their effects, which moderates
harm or exploits beneficial opportunities. Various types of
adaptation can be distinguished, including anticipatory and
reactive adaptation, private and public adaptation, and
autonomous and planned adaptation.
Adaptation assessment
The practice of identifying options to adapt to climate change
and evaluating them in terms of criteria such as availability,
benefits, costs, effectiveness, efficiency, and feasibility.
Adaptation benefits
The avoided damage costs or the accrued benefits following
the adoption and implementation of adaptation measures.
Adaptation costs
Costs of planning, preparing for, facilitating, and implementing
adaptation measures, including transition costs.
Adaptive capacity
The ability of a system to adjust to climate change (including climate
variability and extremes) to moderate potential damages, to take
advantage of opportunities, or to cope with the consequences.
Additionality
Reduction in emissions by sources or enhancement of removals
by sinks that is additional to any that would occur in the absence
of a Joint Implementation or a Clean Development Mechanism
project activity as defined in the Kyoto Protocol Articles on Joint
Implementation and the Clean Development Mechanism. This
definition may be further broadened to include financial,
investment, and technology additionality. Under “financial
additionality,” the project activity funding shall be additional
to existing Global Environmental Facility, other financial
commitments of Parties included in Annex I, Official
Development Assistance, and other systems of cooperation.
Under “investment additionality,” the value of the Emissions
Reduction Unit/Certified Emission Reduction Unit shall
significantly improve the financial and/or commercial viability
of the project activity. Under “technology additionality,” the
technology used for the project activity shall be the best
available for the circumstances of the host Party.
Adjustment time
See Lifetime; see also Response time.
Aerosols
A collection of airborne solid or liquid particles, with a typical
size between 0.01 and 10 mm that reside in the atmosphere
for at least several hours. Aerosols may be of either natural or
anthropogenic origin. Aerosols may influence climate in two
ways: directly through scattering and absorbing radiation, and
indirectly through acting as condensation nuclei for cloud
formation or modifying the optical properties and lifetime of
clouds. See indirect aerosol effect.
Afforestation
Planting of new forests on lands that historically have not
contained forests. For a discussion of the term forest and related
terms such as afforestation, reforestation, and deforestation,
see the IPCC Special Report on Land Use, Land-Use Change,
and Forestry (IPCC, 2000b).
Aggregate impacts
Total impacts summed up across sectors and/or regions. The
aggregation of impacts requires knowledge of (or assumptions
about) the relative importance of impacts in different sectors and
regions. Measures of aggregate impacts include, for example, the
total number of people affected, change in net primary productivity,
number of systems undergoing change, or total economic costs.
Albedo
The fraction of solar radiation reflected by a surface or object,
often expressed as a percentage. Snow covered surfaces have

Climate Change 2001 Synthesis Report
IPCC Third Assessment Report
a high albedo; the albedo of soils ranges from high to low;
vegetation covered surfaces and oceans have a low albedo.
The Earth’s albedo varies mainly through varying cloudiness,
snow, ice, leaf area, and land cover changes.
Algal blooms
A reproductive explosion of algae in a lake, river, or ocean.
Alpine
The biogeographic zone made up of slopes above timberline
and characterized by the presence of rosette-forming
herbaceous plants and low shrubby slow-growing woody
plants.
Alternative development paths
Refer to a variety of possible scenarios for societal values
and consumption and production patterns in all countries,
including, but not limited to, a continuation of today’s trends.
In this report, these paths do not include additional climate
initiatives which means that no scenarios are included that
explicitly assume implementation of the United Nations
Framework Convention on Climate Change or the emission
targets of the Kyoto Protocol, but do include assumptions about
other policies that influence greenhouse gas emissions
indirectly.
Alternative energy
Energy derived from non-fossil-fuel sources.
Ancillary benefits
The ancillary, or side effects, of policies aimed exclusively at
climate change mitigation. Such policies have an impact not
only on greenhouse gas emissions, but also on resource use
efficiency, like reduction in emissions of local and regional
air pollutants associated with fossil-fuel use, and on issues
such as transportation, agriculture, land-use practices,
employment, and fuel security. Sometimes these benefits are
referred to as “ancillary impacts” to reflect that in some cases
the benefits may be negative. From the perspective of policies
directed at abating local air pollution, greenhouse gas
mitigation may also be considered an ancillary benefit, but
these relationships are not considered in this assessment.
Annex I countries/Parties
Group of countries included in Annex I (as amended in 1998)
to the United Nations Framework Convention on Climate
Change, including all the developed countries in the
Organisation for Economic Cooperation and Development,
and economies in transition. By default, the other countries
are referred to as non-Annex I countries. Under Articles 4.2(a)
and 4.2(b) of the Convention, Annex I countries commit
themselves specifically to the aim of returning individually or
jointly to their 1990 levels of greenhouse gas emissions by
the year 2000. See also Annex II, Annex B, and non-Annex B
countries.
Annex II countries
Group of countries included in Annex II to the United Nations
Framework Convention on Climate Change, including all
developed countries in the Organisation for Economic
Cooperation and Development. Under Article 4.2(g) of the
Convention, these countries are expected to provide financial
resources to assist developing countries to comply with their
obligations, such as preparing national reports. Annex II
countries are also expected to promote the transfer of
environmentally sound technologies to developing countries.
See also Annex I, Annex B, non-Annex I, and non-Annex B
countries/Parties.
Annex B countries/Parties
Group of countries included in Annex B in the Kyoto Protocol
that have agreed to a target for their greenhouse gas emissions,
including all the Annex I countries (as amended in 1998) but
Turkey and Belarus. See also Annex II, non-Annex I, and non-
Annex B countries/Parties.
Anthropogenic
Resulting from or produced by human beings.
Anthropogenic emissions
Emissions of greenhouse gases, greenhouse gas precursors,
and aerosols associated with human activities. These include
burning of fossil fuels for energy, deforestation, and land-use
changes that result in net increase in emissions.
Aquaculture
Breeding and rearing fish, shellfish, etc., or growing plants
for food in special ponds.
Aquifer
A stratum of permeable rock that bears water. An unconfined
aquifer is recharged directly by local rainfall, rivers, and lakes,
and the rate of recharge will be influenced by the permeability
of the overlying rocks and soils. A confined aquifer is
characterized by an overlying bed that is impermeable and
the local rainfall does not influence the aquifer.
Arid regions
Ecosystems with less than 250 mm precipitation per year.
Assigned amounts (AAs)
Under the Kyoto Protocol, the total amount of greenhouse
gas emissions that each Annex B country has agreed that its
emissions will not exceed in the first commitment period (2008
to 2012) is the assigned amount. This is calculated by
multiplying the country’s total greenhouse gas emissions in
by five (for the 5-year commitment period) and then by
the percentage it agreed to as listed in Annex B of the Kyoto
Protocol (e.g., 92% for the European Union, 93% for the USA).

Annex B Glossary of Terms
Assigned amount unit (AAU)
Equal to 1 tonne (metric ton) of CO2-equivalent emissions
calculated using the Global Warming Potential.
Atmosphere
The gaseous envelop surrounding the Earth. The dry atmosphere
consists almost entirely of nitrogen (78.1% volume mixing
ratio) and oxygen (20.9% volume mixing ratio), together with
a number of trace gases, such as argon (0.93% volume mixing
ratio), helium, and radiatively active greenhouse gases such
as carbon dioxide (0.035% volume mixing ratio) and ozone.
In addition, the atmosphere contains water vapor, whose
amount is highly variable but typically 1% volume mixing
ratio. The atmosphere also contains clouds and aerosols.
Attribution
See detection and attribution.
Banking
According to the Kyoto Protocol [Article 3(13)], Parties
included in Annex I to the United Nations Framework
Convention on Climate Change may save excess emissions
allowances or credits from the first commitment period for
use in subsequent commitment periods (post-2012).
Barrier
A barrier is any obstacle to reaching a potential that can be
overcome by a policy, program, or measure.
Baseline
The baseline (or reference) is any datum against which change
is measured. It might be a “current baseline,” in which case it
represents observable, present-day conditions. It might also
be a “future baseline,” which is a projected future set of
conditions excluding the driving factor of interest. Alternative
interpretations of the reference conditions can give rise to
multiple baselines.
Basin
The drainage area of a stream, river, or lake.
Biodiversity
The numbers and relative abundances of different genes
(genetic diversity), species, and ecosystems (communities) in
a particular area.
Biofuel
A fuel produced from dry organic matter or combustible oils
produced by plants. Examples of biofuel include alcohol (from
fermented sugar), black liquor from the paper manufacturing
process, wood, and soybean oil.
Biomass
The total mass of living organisms in a given area or volume;
recently dead plant material is often included as dead biomass.
Biome
A grouping of similar plant and animal communities into broad
landscape units that occur under similar environmental
conditions.
Biosphere (terrestrial and marine)
The part of the Earth system comprising all ecosystems and
living organisms in the atmosphere, on land (terrestrial
biosphere), or in the oceans (marine biosphere), including
derived dead organic matter such as litter, soil organic matter,
and oceanic detritus.
Biota
All living organisms of an area; the flora and fauna considered
as a unit.
Black carbon
Operationally defined species based on measurement of light
absorption and chemical reactivity and/or thermal stability;
consists of soot, charcoal, and/or possible light-absorbing
refractory organic matter (Charlson and Heintzenberg, 1995).
Bog
A poorly drained area rich in accumulated plant material,
frequently surrounding a body of open water and having a
characteristic flora (such as sedges, heaths, and sphagnum).
Boreal forest
Forests of pine, spruce, fir, and larch stretching from the east
coast of Canada westward to Alaska and continuing from
Siberia westward across the entire extent of Russia to the
European Plain.
Bottom-up models
A modeling approach that includes technological and
engineering details in the analysis. See also top-down models.
Burden
The total mass of a gaseous substance of concern in the
atmosphere.
Capacity building
In the context of climate change, capacity building is a process
of developing the technical skills and institutional capability
in developing countries and economies in transition to enable
them to participate in all aspects of adaptation to, mitigation
of, and research on climate change, and the implementation
of the Kyoto Mechanisms, etc.
Carbonaceous aerosol
Aerosol consisting predominantly of organic substances and
various forms of black carbon (Charlson and Heintzenberg,
).

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IPCC Third Assessment Report
Carbon cycle
The term used to describe the flow of carbon (in various forms
such as as carbon dioxide) through the atmosphere, ocean,
terrestrial biosphere, and lithosphere.
Carbon dioxide (CO2)
A naturally occurring gas, and also a by-product of burning
fossil fuels and biomass, as well as land-use changes and other
industrial processes. It is the principal anthropogenic
greenhouse gas that affects the Earth’s radiative balance. It
is the reference gas against which other greenhouse gases are
measured and therefore has a Global Warming Potential of 1.
Carbon dioxide (CO2) fertilization
The enhancement of the growth of plants as a result of increased
atmospheric carbon dioxide concentration. Depending on their
mechanism of photosynthesis, certain types of plants are more
sensitive to changes in atmospheric carbon dioxide concentration.
In particular, plants that produce a three-carbon compound (C3)
during photosynthesis—including most trees and agricultural
crops such as rice, wheat, soybeans, potatoes, and vegetables—
generally show a larger response than plants that produce a
four-carbon compound (C4) during photosynthesis—mainly
of tropical origin, including grasses and the agriculturally
important crops maize, sugar cane, millet, and sorghum.
Carbon leakage
See leakage.
Carbon taxes
See emissions tax.
Catchment
An area that collects and drains rainwater.
Certified Emission Reduction (CER) Unit
Equal to 1 tonne (metric ton) of CO2-equivalent emissions
reduced or sequestered through a Clean Development
Mechanism project, calculated using Global Warming
Potentials. See also Emissions Reduction Unit.
Chlorofluorocarbons (CFCs)
Greenhouse gases covered under the 1987 Montreal Protocol
and used for refrigeration, air conditioning, packaging,
insulation, solvents, or aerosol propellants. Since they are not
destroyed in the lower atmosphere, CFCs drift into the upper
atmosphere where, given suitable conditions, they break down
ozone. These gases are being replaced by other compounds,
including hydrochlorofluorocarbons and hydrofluorocarbons,
which are greenhouse gases covered under the Kyoto Protocol.
Cholera
An intestinal infection that results in frequent watery stools,
cramping abdominal pain, and eventual collapse from dehydration.
Clean Development Mechanism (CDM)
Defined in Article 12 of the Kyoto Protocol, the Clean
Development Mechanism is intended to meet two objectives:
(1) to assist Parties not included in Annex I in achieving
sustainable development and in contributing to the ultimate
objective of the convention; and (2) to assist Parties included
in Annex I in achieving compliance with their quantified
emission limitation and reduction commitments. Certified
Emission Reduction Units from Clean Development
Mechanism projects undertaken in non-Annex I countries that
limit or reduce greenhouse gas emissions, when certified by
operational entities designated by Conference of the Parties/
Meeting of the Parties, can be accrued to the investor
(government or industry) from Parties in Annex B. A share of
the proceeds from the certified project activities is used to
cover administrative expenses as well as to assist developing
country Parties that are particularly vulnerable to the adverse
effects of climate change to meet the costs of adaptation.
Climate
Climate in a narrow sense is usually defined as the “average
weather” or more rigorously as the statistical description in
terms of the mean and variability of relevant quantities over a
period of time ranging from months to thousands or millions
of years. The classical period is 30 years, as defined by the
World Meteorological Organization (WMO). These relevant
quantities are most often surface variables such as temperature,
precipitation, and wind. Climate in a wider sense is the state,
including a statistical description, of the climate system.
Climate change
Climate change refers to a statistically significant variation in
either the mean state of the climate or in its variability,
persisting for an extended period (typically decades or longer).
Climate change may be due to natural internal processes or
external forcings, or to persistent anthropogenic changes in
the composition of the atmosphere or in land use. Note that
the United Nations Framework Convention on Climate
Change (UNFCCC), in its Article 1, defines “climate change”
as: “a change of climate which is attributed directly or
indirectly to human activity that alters the composition of the
global atmosphere and which is in addition to natural climate
variability observed over comparable time periods.” The
UNFCCC thus makes a distinction between “climate change”
attributable to human activities altering the atmospheric
composition, and “climate variability” attributable to natural
causes. See also climate variability.
Climate feedback
An interaction mechanism between processes in the climate
system is called a climate feedback, when the result of an initial
process triggers changes in a second process that in turn
influences the initial one. A positive feedback intensifies the
original process, and a negative feedback reduces it.

Annex B Glossary of Terms
Climate model (hierarchy)
A numerical representation of the climate system based on the
physical, chemical, and biological properties of its components,
their interactions and feedback processes, and accounting for
all or some of its known properties. The climate system can be
represented by models of varying complexity—that is, for any
one component or combination of components a “hierarchy”
of models can be identified, differing in such aspects as the
number of spatial dimensions, the extent to which physical,
chemical or biological processes are explicitly represented,
or the level at which empirical parametrizations are involved.
Coupled atmosphere/ocean/sea-ice general circulation models
(AOGCMs) provide a comprehensive representation of the
climate system. There is an evolution towards more complex
models with active chemistry and biology. Climate models
are applied, as a research tool, to study and simulate the
climate, but also for operational purposes, including monthly,
seasonal, and interannual climate predictions.
Climate prediction
A climate prediction or climate forecast is the result of an
attempt to produce a most likely description or estimate of the
actual evolution of the climate in the future (e.g., at seasonal,
interannual, or long-term time-scales). See also climate
projection and climate (change) scenario.
Climate projection
A projection of the response of the climate system to emission or
concentration scenarios of greenhouse gases and aerosols, or
radiative forcing scenarios, often based upon simulations by
climate models. Climate projections are distinguished from climate
predictions in order to emphasize that climate projections depend
upon the emission/concentration/radiative forcing scenario used,
which are based on assumptions, concerning, for example, future
socio-economic and technological developments that may or may
not be realized, and are therefore subject to substantial uncertainty.
Climate scenario
A plausible and often simplified representation of the future
climate, based on an internally consistent set of climatological
relationships, that has been constructed for explicit use in
investigating the potential consequences of anthropogenic
climate change, often serving as input to impact models.
Climate projections often serve as the raw material for
constructing climate scenarios, but climate scenarios usually
require additional information such as about the observed
current climate. A “climate change scenario” is the difference
between a climate scenario and the current climate.
Climate sensitivity
In IPCC assessments, “equilibrium climate sensitivity” refers
to the equilibrium change in global mean surface temperature
following a doubling of the atmospheric (equivalent) CO2
concentration. More generally, equilibrium climate sensitivity
refers to the equilibrium change in surface air temperature
following a unit change in radiative forcing (°C/Wm-2). In
practice, the evaluation of the equilibrium climate sensitivity
requires very long simulations with coupled general circulation
models. The “effective climate sensitivity” is a related measure
that circumvents this requirement. It is evaluated from model
output for evolving non-equilibrium conditions. It is a measure
of the strengths of the feedbacks at a particular time and may
vary with forcing history and climate state. See climate model.
Climate system
The climate system is the highly complex system consisting
of five major components: the atmosphere, the hydrosphere,
the cryosphere, the land surface and the biosphere, and the
interactions between them. The climate system evolves in time
under the influence of its own internal dynamics and because
of external forcings such as volcanic eruptions, solar variations,
and human-induced forcings such as the changing composition
of the atmosphere and land-use change.
Climate variability
Climate variability refers to variations in the mean state and other
statistics (such as standard deviations, the occurrence of extremes,
etc.) of the climate on all temporal and spatial scales beyond
that of individual weather events. Variability may be due to
natural internal processes within the climate system (internal
variability), or to variations in natural or anthropogenic
external forcing (external variability). See also climate change.
CO2-equivalent
See equivalent CO2.
CO2 fertilization
See carbon dioxide (CO2) fertilization.
Co-benefits
The benefits of policies that are implemented for various reasons
at the same time—including climate change mitigation—
acknowledging that most policies designed to address
greenhouse gas mitigation also have other, often at least
equally important, rationales (e.g., related to objectives of
development, sustainability, and equity). The term co-impact
is also used in a more generic sense to cover both the positive
and negative sides of the benefits. See also ancillary benefits.
Co-generation
The use of waste heat from electric generation, such as exhaust
from gas turbines, for either industrial purposes or district heating.
Compliance
See implementation.
Conference of the Parties (COP)
The supreme body of the United Nations Framework Convention
on Climate Change (UNFCCC), comprising countries that have
ratified or acceded to the UNFCCC. The first session of the

Climate Change 2001 Synthesis Report
IPCC Third Assessment Report
Conference of the Parties (COP-1) was held in Berlin in 1995,
followed by COP-2 in Geneva 1996, COP-3 in Kyoto 1997,
COP-4 in Buenos Aires 1998, COP-5 in Bonn 1999, COP-6
Part 1 in The Hague 2000, and COP-6 Part 2 in Bonn 2001.
COP-7 is scheduled for November 2001 in Marrakech. See
also Meeting of the Parties (MOP).
Cooling degree days
The integral over a day of the temperature above 18°C (e.g., a
day with an average temperature of 20°C counts as 2 cooling
degree days). See also heating degree days.
Coping range
The variation in climatic stimuli that a system can absorb
without producing significant impacts.
Coral bleaching
The paling in color of corals resulting from a loss of symbiotic
algae. Bleaching occurs in response to physiological shock in
response to abrupt changes in temperature, salinity, and turbidity.
Cost-effective
A criterion that specifies that a technology or measure delivers
a good or service at equal or lower cost than current practice, or
the least-cost alternative for the achievement of a given target.
Cryosphere
The component of the climate system consisting of all snow,
ice, and permafrost on and beneath the surface of the earth
and ocean. See also glacier and ice sheet.
Deepwater formation
Occurs when seawater freezes to form sea ice. The local release
of salt and consequent increase in water density leads to the
formation of saline coldwater that sinks to the ocean floor.
Deforestation
Conversion of forest to non-forest. For a discussion of the
term forest and related terms such as afforestation,
reforestation, and deforestation, see the IPCC Special Report
on Land Use, Land-Use Change, and Forestry (IPCC, 2000b).
Demand-side management
Policies and programs designed for a specific purpose to
influence consumer demand for goods and/or services. In the
energy sector, for instance, it refers to policies and programs
designed to reduce consumer demand for electricity and other
energy sources. It helps to reduce greenhouse gas emissions.
Dengue Fever
An infectious viral disease spread by mosquitoes often called
breakbone fever because it is characterized by severe pain in
joints and back. Subsequent infections of the virus may lead
to dengue haemorrhagic fever (DHF) and dengue shock
syndrome (DSS), which may be fatal.
Deposit–refund system
Combines a deposit or fee (tax) on a commodity with a refund
or rebate (subsidy) for implementation of a specified action.
Se also emissions tax.
Desert
An ecosystem with less than 100 mm precipitation per year.
Desertification
Land degradation in arid, semi-arid, and dry sub-humid areas
resulting from various factors, including climatic variations
and human activities. Further, the United Nations Convention
to Combat Desertification defines land degradation as a
reduction or loss in arid, semi-arid, and dry sub-humid areas
of the biological or economic productivity and complexity of
rain-fed cropland, irrigated cropland, or range, pasture, forest,
and woodlands resulting from land uses or from a process or
combination of processes, including processes arising from
human activities and habitation patterns, such as: (i) soil
erosion caused by wind and/or water; (ii) deterioration of the
physical, chemical, and biological or economic properties of
soil; and (iii) long-term loss of natural vegetation.
Detection and attribution
Climate varies continually on all time scales. Detection of climate
change is the process of demonstrating that climate has
changed in some defined statistical sense, without providing
a reason for that change. Attribution of causes of climate
change is the process of establishing the most likely causes
for the detected change with some defined level of confidence.
Disturbance regime
Frequency, intensity, and types of disturbances, such as fires,
inspect or pest outbreaks, floods, and droughts.
Diurnal temperature range
The difference between the maximum and minimum
temperature during a day.
Double dividend
The effect that revenue-generating instruments, such as carbon
taxes or auctioned (tradable) carbon emission permits, can (i)
limit or reduce greenhouse gas emissions and (ii) offset at
least part of the potential welfare losses of climate policies
through recycling the revenue in the economy to reduce other
taxes likely to be distortionary. In a world with involuntary
unemployment, the climate change policy adopted may have an
effect (a positive or negative “third dividend”) on employment.
Weak double dividend occurs as long as there is a revenue
recycling effect—that is, as long as revenues are recycled
through reductions in the marginal rates of distortionary taxes.
Strong double dividend requires that the (beneficial) revenue
recycling effect more than offset the combination of the
primary cost and, in this case, the net cost of abatement is
negative.

Annex B Glossary of Terms
Drought
The phenomenon that exists when precipitation has been
significantly below normal recorded levels, causing serious
hydrological imbalances that adversely affect land resource
production systems.
Economic potential
Economic potential is the portion of technological potential
for greenhouse gas emissions reductions or energy efficiency
improvements that could be achieved cost-effectively through
the creation of markets, reduction of market failures, or increased
financial and technological transfers. The achievement of
economic potential requires additional policies and measures
to break down market barriers. See also market potential,
socio-economic potential, and technological potential.
Economies in transition (EITs)
Countries with national economies in the process of changing
from a planned economic system to a market economy.
Ecosystem
A system of interacting living organisms together with their
physical environment. The boundaries of what could be called
an ecosystem are somewhat arbitrary, depending on the focus
of interest or study. Thus, the extent of an ecosystem may range
from very small spatial scales to, ultimately, the entire Earth.
Ecosystem services
Ecological processes or functions that have value to individuals
or society.
El Niño Southern Oscillation (ENSO)
El Niño, in its original sense, is a warmwater current that periodically
flows along the coast of Ecuador and Peru, disrupting the local
fishery. This oceanic event is associated with a fluctuation of the
intertropical surface pressure pattern and circulation in the Indian
and Pacific Oceans, called the Southern Oscillation. This coupled
atmosphere-ocean phenomenon is collectively known as El Niño
Southern Oscillation, or ENSO. During an El Niño event, the
prevailing trade winds weaken and the equatorial countercurrent
strengthens, causing warm surface waters in the Indonesian area
to flow eastward to overlie the cold waters of the Peru current.
This event has great impact on the wind, sea surface temperature,
and precipitation patterns in the tropical Pacific. It has climatic
effects throughout the Pacific region and in many other parts of
the world. The opposite of an El Niño event is called La Niña.
Emissions
In the climate change context, emissions refer to the release
of greenhouse gases and/or their precursors and aerosols into
the atmosphere over a specified area and period of time.
Emissions permit
An emissions permit is the non-transferable or tradable
allocation of entitlements by an administrative authority
(intergovernmental organization, central or local government
agency) to a regional (country, sub-national) or a sectoral (an
individual firm) entity to emit a specified amount of a substance.
Emissions quota
The portion or share of total allowable emissions assigned to a
country or group of countries within a framework of maximum
total emissions and mandatory allocations of resources.
Emissions Reduction Unit (ERU)
Equal to 1 tonne (metric ton) of carbon dioxide emissions
reduced or sequestered arising from a Joint Implementation
(defined in Article 6 of the Kyoto Protocol) project calculated
using Global Warming Potential. See also Certified Emission
Reduction Unit and emissions trading.
Emissions tax
Levy imposed by a government on each unit of CO2-equivalent
emissions by a source subject to the tax. Since virtually all of
the carbon in fossil fuels is ultimately emitted as carbon dioxide,
a levy on the carbon content of fossil fuels—a carbon tax—is
equivalent to an emissions tax for emissions caused by fossilfuel
combustion. An energy tax—a levy on the energy content
of fuels—reduces demand for energy and so reduces carbon
dioxide emissions from fossil-fuel use. An ecotax is designated
for the purpose of influencing human behavior (specifically
economic behavior) to follow an ecologically benign path.
International emissions/carbon/energy tax is a tax imposed on
specified sources in participating countries by an international
agency. The revenue is distributed or used as specified by
participating countries or the international agency.
Emissions trading
A market-based approach to achieving environmental objectives
that allows, those reducing greenhouse gas emissions below
what is required, to use or trade the excess reductions to offset
emissions at another source inside or outside the country. In
general, trading can occur at the intracompany, domestic, and
international levels. The IPCC Second Assessment Report
adopted the convention of using “permits” for domestic trading
systems and “quotas” for international trading systems. Emissions
trading under Article 17 of the Kyoto Protocol is a tradable
quota system based on the assigned amounts calculated from
the emission reduction and limitation commitments listed in
Annex B of the Protocol. See also Certified Emission Reduction
Unit and Clean Development Mechanism.
Emissions scenario
A plausible representation of the future development of
emissions of substances that are potentially radiatively active
(e.g., greenhouse gases, aerosols), based on a coherent and
internally consistent set of assumptions about driving forces
(such as demographic and socio-economic development,
technological change) and their key relationships. Concentration
scenarios, derived from emissions scenarios, are used as input

Climate Change 2001 Synthesis Report
IPCC Third Assessment Report
into a climate model to compute climate projections. In IPCC
(1992), a set of emissions scenarios were used as a basis for
the climate projections in IPCC (1996). These emissions
scenarios are referred to as the IS92 scenarios. In the IPCC
Special Report on Emissions Scenarios (Nakicenovic et al.,
), new emissions scenarios—the so-called SRES
scenarios—were published. For the meaning of some terms
related to these scenarios, see SRES scenarios.
Endemic
Restricted or peculiar to a locality or region. With regard to human
health, endemic can refer to a disease or agent present or usually
prevalent in a population or geographical area at all times.
Energy balance
Averaged over the globe and over longer time periods, the
energy budget of the climate system must be in balance.
Because the climate system derives all its energy from the
Sun, this balance implies that, globally, the amount of incoming
solar radiation must on average be equal to the sum of the
outgoing reflected solar radiation and the outgoing infrared
radiation emitted by the climate system. A perturbation of
this global radiation balance, be it human-induced or natural,
is called radiative forcing.
Energy conversion
See energy transformation.
Energy efficiency
Ratio of energy output of a conversion process or of a system
to its energy input.
Energy intensity
Energy intensity is the ratio of energy consumption to economic
or physical output. At the national level, energy intensity is the
ratio of total domestic primary energy consumption or final energy
consumption to Gross Domestic Product or physical output.
Energy service
The application of useful energy to tasks desired by the
consumer such as transportation, a warm room, or light.
Energy tax
See emissions tax.
Energy transformation
The change from one form of energy, such as the energy
embodied in fossil fuels, to another, such as electricity.
Environmentally Sound Technologies (ESTs)
Technologies that protect the environment, are less polluting,
use all resources in a more sustainable manner, recycle more
of their wastes and products, and handle residual wastes in a
more acceptable manner than the technologies for which they
were substitutes and are compatible with nationally determined
socio-economic, cultural, and environmental priorities. ESTs
in this report imply mitigation and adaptation technologies, hard
and soft technologies.
Epidemic
Occurring suddenly in numbers clearly in excess of normal
expectancy, said especially of infectious diseases but applied also
to any disease, injury, or other health-related event occurring in
such outbreaks.
Equilibrium and transient climate experiment
An “equilibrium climate experiment” is an experiment in which
a climate model is allowed to fully adjust to a change in radiative
forcing. Such experiments provide information on the difference
between the initial and final states of the model, but not on the
time-dependent response. If the forcing is allowed to evolve
gradually according to a prescribed emission scenario, the timedependent
response of a climate model may be analyzed. Such
an experiment is called a “transient climate experiment.” See
also climate projection.
Equivalent CO2 (carbon dioxide)
The concentration of carbon dioxide that would cause the same
amount of radiative forcing as a given mixture of carbon dioxide
and other greenhouse gases.
Erosion
The process of removal and transport of soil and rock by
weathering, mass wasting, and the action of streams, glaciers,
waves, winds, and underground water.
Eustatic sea-level change
A change in global average sea level brought about by an
alteration to the volume of the world ocean. This may be caused
by changes in water density or in the total mass of water. In
discussions of changes on geological time scales, this term
sometimes also includes changes in global average sea level
caused by an alteration to the shape of the ocean basins. In this
report, the term is not used in that sense.
Eutrophication
The process by which a body of water (often shallow) becomes
(either naturally or by pollution) rich in dissolved nutrients with
a seasonal deficiency in dissolved oxygen.
Evaporation
The process by which a liquid becomes a gas.
Evapotranspiration
The combined process of evaporation from the Earth’s surface
and transpiration from vegetation.
Exotic species
See introduced species.

Annex B Glossary of Terms
Exposure
The nature and degree to which a system is exposed to
significant climatic variations.
Externality
See external cost.
External cost
Used to define the costs arising from any human activity, when
the agent responsible for the activity does not take full account
of the impacts on others of his or her actions. Equally, when
the impacts are positive and not accounted for in the actions
of the agent responsible they are referred to as external benefits.
Emissions of particulate pollution from a power station affect
the health of people in the vicinity, but this is not often
considered, or is given inadequate weight, in private decision
making and there is no market for such impacts. Such a
phenomenon is referred to as an “externality,” and the costs it
imposes are referred to as the external costs.
External forcing
See climate system.
Extinction
The complete disappearance of an entire species.
Extirpation
The disappearance of a species from part of its range; local
extinction.
Extreme weather event
An extreme weather event is an event that is rare within its
statistical reference distribution at a particular place.
Definitions of “rare” vary, but an extreme weather event would
normally be as rare as or rarer than the 10th or 90th percentile.
By definition, the characteristics of what is called extreme
weather may vary from place to place. An extreme climate
event is an average of a number of weather events over a certain
period of time, an average which is itself extreme (e.g., rainfall
over a season).
Feedback
See climate feedback.
Fiber
Wood, fuelwood (either woody or non-woody).
Final energy
Energy supplied that is available to the consumer to be converted
into usable energy (e.g., electricity at the wall outlet).
Flexibility mechanisms
See Kyoto Mechanisms.
Flux adjustment
To avoid the problem of coupled atmosphere-ocean general
circulation models drifting into some unrealistic climate state,
adjustment terms can be applied to the atmosphere-ocean fluxes
of heat and moisture (and sometimes the surface stresses resulting
from the effect of the wind on the ocean surface) before these
fluxes are imposed on the model ocean and atmosphere. Because
these adjustments are pre-computed and therefore independent
of the coupled model integration, they are uncorrelated to the
anomalies that develop during the integration.
Food insecurity
A situation that exists when people lack secure access to sufficient
amounts of safe and nutritious food for normal growth and
development and an active and healthy life. It may be caused
by the unavailability of food, insufficient purchasing power,
inappropriate distribution, or inadequate use of food at the
household level. Food insecurity may be chronic, seasonal, or
transitory.
Forest
A vegetation type dominated by trees. Many definitions of the
term forest are in use throughout the world, reflecting wide
differences in bio-geophysical conditions, social structure, and
economics. For a discussion of the term forest and related
terms such as afforestation, reforestation, and deforestation:
see the IPCC Special Report on Land Use, Land-Use Change,
and Forestry (IPCC, 2000b).
Fossil CO2 (carbon dioxide) emissions
Emissions of carbon dioxide resulting from the combustion
of fuels from fossil carbon deposits such as oil, natural gas,
and coal.
Fossil fuels
Carbon-based fuels from fossil carbon deposits, including coal,
oil, and natural gas.
Freshwater lens
A lenticular fresh groundwater body that underlies an oceanic
island. It is underlain by saline water.
Fuel switching
Policy designed to reduce carbon dioxide emissions by switching
to lower carbon-content fuels, such as from coal to natural gas.
Full-cost pricing
The pricing of commercial goods—such as electric power—
that includes in the final prices faced by the end user not only
the private costs of inputs, but also the costs of externalities
created by their production and use.
Framework Convention on Climate Change
See United Nations Framework Convention on Climate Change.

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General circulation
The large scale motions of the atmosphere and the ocean as a
consequence of differential heating on a rotating Earth, aiming
to restore the energy balance of the system through transport
of heat and momentum.
General Circulation Model (GCM)
See climate model.
Geo-engineering
Efforts to stabilize the climate system by directly managing
the energy balance of the Earth, thereby overcoming the
enhanced greenhouse effect.
Glacier
A mass of land ice flowing downhill (by internal deformation
and sliding at the base) and constrained by the surrounding
topography (e.g., the sides of a valley or surrounding peaks);
the bedrock topography is the major influence on the dynamics
and surface slope of a glacier. A glacier is maintained by
accumulation of snow at high altitudes, balanced by melting
at low altitudes or discharge into the sea.
Global surface temperature
The global surface temperature is the area-weighted global
average of (i) the sea surface temperature over the oceans (i.e.,
the sub-surface bulk temperature in the first few meters of the
ocean), and (ii) the surface air temperature over land at 1.5 m
above the ground.
Global Warming Potential (GWP)
An index, describing the radiative characteristics of well-mixed
greenhouse gases, that represents the combined effect of the
differing times these gases remain in the atmosphere and their
relative effectiveness in absorbing outgoing infrared radiation.
This index approximates the time-integrated warming effect
of a unit mass of a given greenhouse gas in today’s atmosphere,
relative to that of carbon dioxide.
Greenhouse effect
Greenhouse gases effectively absorb infrared radiation, emitted
by the Earth’s surface, by the atmosphere itself due to the same
gases, and by clouds. Atmospheric radiation is emitted to all sides,
including downward to the Earth’s surface. Thus greenhouse
gases trap heat within the surface-troposphere system. This is
called the “natural greenhouse effect.” Atmospheric radiation
is strongly coupled to the temperature of the level at which it
is emitted. In the troposphere, the temperature generally decreases
with height. Effectively, infrared radiation emitted to space
originates from an altitude with a temperature of, on average,
-19°C, in balance with the net incoming solar radiation, whereas
the Earth’s surface is kept at a much higher temperature of, on
average, +14°C. An increase in the concentration of greenhouse
gases leads to an increased infrared opacity of the atmosphere,
and therefore to an effective radiation into space from a higher
altitude at a lower temperature. This causes a radiative forcing,
an imbalance that can only be compensated for by an increase
of the temperature of the surface-troposphere system. This is
the “enhanced greenhouse effect.”
Greenhouse gas
Greenhouse gases are those gaseous constituents of the atmosphere,
both natural and anthropogenic, that absorb and emit radiation
at specific wavelengths within the spectrum of infrared radiation
emitted by the Earth’s surface, the atmosphere, and clouds. This
property causes the greenhouse effect. Water vapor (H2O), carbon
dioxide (CO2), nitrous oxide (N2O), methane (CH4), and ozone
(O3) are the primary greenhouse gases in the Earth’s atmosphere.
Moreover there are a number of entirely human-made greenhouse
gases in the atmosphere, such as the halocarbons and other
chlorine- and bromine-containing substances, dealt with under
the Montreal Protocol. Besides CO2, N2O, and CH4, the Kyoto
Protocol deals with the greenhouse gases sulfur hexafluoride (SF6),
hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs).
Groin
A low, narrow jetty, usually extending roughly perpendicular
to the shoreline, designed to protect the shore from erosion by
currents, tides, or waves, or to trap sand for the purpose of
building up or making a beach.
Gross Domestic Product (GDP)
The sum of gross value added, at purchasers’ prices, by all
resident and non-resident producers in the economy, plus any
taxes and minus any subsidies not included in the value of the
products in a country or a geographic region for a given period
of time, normally 1 year. It is calculated without deducting for
depreciation of fabricated assets or depletion and degradation
of natural resources. GDP is an often used but incomplete
measure of welfare.
Gross Primary Production (GPP)
The amount of carbon fixed from the atmosphere through
photosynthesis.
Groundwater recharge
The process by which external water is added to the zone of
saturation of an aquifer, either directly into a formation or
indirectly by way of another formation.
Habitat
The particular environment or place where an organism or
species tend to live; a more locally circumscribed portion of
the total environment.
Halocarbons
Compounds containing carbon and either chlorine, bromine,
or fluorine. Such compounds can act as powerful greenhouse
gases in the atmosphere. The chlorine- and bromine-containing
halocarbons are also involved in the depletion of the ozone layer.

Annex B Glossary of Terms
Harmonized emissions/carbon/energy tax
Commits participating countries to impose a tax at a common
rate on the same sources. Each country can retain the tax
revenue it collects. A harmonized tax would not necessarily
require countries to impose a tax at the same rate, but imposing
different rates across countries would not be cost-effective.
See also emissions tax.
Heat island
An area within an urban area characterized by ambient
temperatures higher than those of the surrounding area because
of the absorption of solar energy by materials like asphalt.
Heating degree days
The integral over a day of the temperature below 18°C (e.g., a
day with an average temperature of 16°C counts as 2 heating
degree days). See also cooling degree days.
Hedging
In the context of climate change mitigation, hedging is defined
as balancing the risks of acting too slowly against acting too
quickly, and it depends on society’s attitude towards risks.
Heterotrophic respiration
The conversion of organic matter to CO2 by organisms other
than plants.
Human settlement
A place or area occupied by settlers.
Human system
Any system in which human organizations play a major role.
Often, but not always, the term is synonymous with “society”
or “social system” (e.g., agricultural system, political system,
technological system, economic system).
Hydrofluorocarbons (HFCs)
Among the six greenhouse gases to be curbed under the Kyoto
Protocol. They are produced commercially as a substitute for
chlorofluorocarbons. HFCs largely are used in refrigeration
and semiconductor manufacturing. Their Global Warming
Potentials range from 1,300 to 11,700.
Hydrosphere
The component of the climate system composed of liquid
surface and subterranean water, such as oceans, seas, rivers,
freshwater lakes, underground water, etc.
Ice cap
A dome shaped ice mass covering a highland area that is
considerably smaller in extent than an ice sheet.
Ice sheet
A mass of land ice that is sufficiently deep to cover most of
the underlying bedrock topography, so that its shape is mainly
determined by its internal dynamics (the flow of the ice as it
deforms internally and slides at its base). An ice sheet flows
outward from a high central plateau with a small average
surface slope. The margins slope steeply, and the ice is
discharged through fast-flowing ice streams or outlet glaciers,
in some cases into the sea or into ice shelves floating on the
sea. There are only two large ice sheets in the modern world,
on Greenland and Antarctica, the Antarctic ice sheet being
divided into East and West by the Transantarctic Mountains;
during glacial periods there were others.
Ice shelf
A floating ice sheet of considerable thickness attached to a
coast (usually of great horizontal extent with a level or gently
undulating surface); often a seaward extension of ice sheets.
(Climate) Impact assessment
The practice of identifying and evaluating the detrimental and
beneficial consequences of climate change on natural and
human systems.
(Climate) Impacts
Consequences of climate change on natural and human
systems. Depending on the consideration of adaptation, one
can distinguish between potential impacts and residual impacts.
Potential impacts: All impacts that may occur given a
projected change in climate, without considering adaptation.
Residual impacts: The impacts of climate change that
would occur after adaptation.
See also aggregate impacts, market impacts, and non-market
impacts.
Implementation
Implementation refers to the actions (legislation or regulations,
judicial decrees, or other actions) that governments take to
translate international accords into domestic law and policy.
It includes those events and activities that occur after the
issuing of authoritative public policy directives, which include
the effort to administer and the substantive impacts on people
and events. It is important to distinguish between the legal
implementation of international commitments (in national law)
and the effective implementation (measures that induce
changes in the behavior of target groups). Compliance is a
matter of whether and to what extent countries do adhere to
the provisions of the accord. Compliance focuses on not only
whether implementing measures are in effect, but also on
whether there is compliance with the implementing actions.
Compliance measures the degree to which the actors whose
behavior is targeted by the agreement, whether they are local
government units, corporations, organizations, or individuals,
conform to the implementing measures and obligations.
Implementation costs
Costs involved in the implementation of mitigation options.
These costs are associated with the necessary institutional
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changes, information requirements, market size, opportunities
for technology gain and learning, and economic incentives
needed (grants, subsidies, and taxes).
Indigenous peoples
People whose ancestors inhabited a place or a country when
persons from another culture or ethnic background arrived on
the scene and dominated them through conquest, settlement,
or other means and who today live more in conformity with
their own social, economic, and cultural customs and traditions
than those of the country of which they now form a part (also
referred to as “native,” “aboriginal,” or “tribal” peoples).
Indirect aerosol effect
Aerosols may lead to an indirect radiative forcing of the climate
system through acting as condensation nuclei or modifying
the optical properties and lifetime of clouds. Two indirect
effects are distinguished:
First indirect effect: A radiative forcing induced by an increase
in anthropogenic aerosols which cause an initial increase
in droplet concentration and a decrease in droplet size for
fixed liquid water content, leading to an increase of cloud
albedo. This effect is also known as the “Twomey effect.”
This is sometimes referred to as the cloud albedo effect.
However this is highly misleading since the second indirect
effect also alters cloud albedo.
Second indirect effect: A radiative forcing induced by an
increase in anthropogenic aerosols which cause a decrease
in droplet size, reducing the precipitation efficiency, thereby
modifying the liquid water content, cloud thickness, and
cloud lifetime. This effect is also known as the “cloud
lifetime effect” or “Albrecht effect.”
Industrial Revolution
A period of rapid industrial growth with far-reaching social
and economic consequences, beginning in England during the
second half of the 18th century and spreading to Europe and
later to other countries including the United States. The
invention of the steam engine was an important trigger of this
development. The Industrial Revolution marks the beginning
of a strong increase in the use of fossil fuels and emission of,
in particular, fossil carbon dioxide. In this report, the terms
“pre-industrial” and “industrial” refer, somewhat arbitrarily,
to the periods before and after the year 1750, respectively.
Inertia
Delay, slowness, or resistance in the response of the climate,
biological, or human systems to factors that alter their rate of
change, including continuation of change in the system after
the cause of that change has been removed.
Infectious diseases
Any disease that can be transmitted from one person to another.
This may occur by direct physical contact, by common
handling of an object that has picked up infective organisms,
through a disease carrier, or by spread of infected droplets
coughed or exhaled into the air.
Infrared radiation
Radiation emitted by the Earth’s surface, the atmosphere, and
clouds. It is also known as terrestrial or long-wave radiation.
Infrared radiation has a distinctive range of wavelengths
(“spectrum”) longer than the wavelength of the red color in
the visible part of the spectrum. The spectrum of infrared
radiation is practically distinct from that of solar or short-wave
radiation because of the difference in temperature between
the Sun and the Earth-atmosphere system.
Infrastructure
The basic equipment, utilities, productive enterprises,
installations, institutions, and services essential for the
development, operation, and growth of an organization, city,
or nation. For example, roads; schools; electric, gas, and water
utilities; transportation; communication; and legal systems
would be all considered as infrastructure.
Integrated assessment
A method of analysis that combines results and models from
the physical, biological, economic, and social sciences, and
the interactions between these components, in a consistent
framework, to evaluate the status and the consequences of
environmental change and the policy responses to it.
Interaction effect
The result or consequence of the interaction of climate change
policy instruments with existing domestic tax systems, including
both cost-increasing tax interaction and cost-reducing revenuerecycling
effect. The former reflects the impact that greenhouse
gas policies can have on the functioning of labor and capital markets
through their effects on real wages and the real return to capital.
By restricting the allowable greenhouse gas emissions, permits,
regulations, or a carbon tax raise the costs of production and the
prices of output, thus reducing the real return to labor and capital.
For policies that raise revenue for the government—carbon taxes
and auctioned permits—the revenues can be recycled to reduce
existing distortionary taxes. See also double dividend.
Internal variability
See climate variability.
International emissions/carbon/energy tax
See emissions tax.
International Energy Agency (IEA)
Paris-based energy forum established in 1974. It is linked with
the Organisation for Economic Cooperation and Development
to enable member countries to take joint measures to meet oil
supply emergencies, to share energy information, to coordinate
their energy policies, and to cooperate in the development of
rational energy programs.
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Annex B Glossary of Terms
International product and/or technology standards
See standards.
Introduced species
A species occurring in an area outside its historically known
natural range as a result of accidental dispersal by humans
(also referred to as “exotic species” or “alien species”).
Invasive species
An introduced species that invades natural habitats.
Isostatic land movements
Isostasy refers to the way in which the lithosphere and mantle
respond to changes in surface loads. When the loading of the
lithosphere is changed by alterations in land ice mass, ocean
mass, sedimentation, erosion, or mountain building, vertical
isostatic adjustment results, in order to balance the new load.
Joint Implementation (JI)
A market-based implementation mechanism defined in Article
of the Kyoto Protocol, allowing Annex I countries or
companies from these countries to implement projects jointly
that limit or reduce emissions, or enhance sinks, and to share
the Emissions Reduction Units. JI activity is also permitted in
Article 4.2(a) of the United Nations Framework Convention
on Climate Change. See also Activities Implemented Jointly
and Kyoto Mechanisms.
Known technological options
Refer to technologies that exist in operation or pilot plant stage
today. It does not include any new technologies that will require
drastic technological breakthroughs.
Kyoto Mechanisms
Economic mechanisms based on market principles that Parties
to the Kyoto Protocol can use in an attempt to lessen the
potential economic impacts of greenhouse gas emissionreduction
requirements. They include Joint Implementation
(Article 6), the Clean Development Mechanism (Article 12),
and Emissions Trading (Article 17).
Kyoto Protocol
The Kyoto Protocol to the United Nations Framework Convention
on Climate Change (UNFCCC) was adopted at the Third Session
of the Conference of the Parties to the UNFCCC in 1997 in
Kyoto, Japan. It contains legally binding commitments, in addition
to those included in the UNFCCC. Countries included in Annex
B of the Protocol (most countries in the Organisation for
Economic Cooperation and Development, and countries with
economies in transition) agreed to reduce their anthropogenic
greenhouse gas emissions (carbon dioxide, methane, nitrous
oxide, hydrofluorocarbons, perfluorocarbons, and sulfur
hexafluoride) by at least 5% below 1990 levels in the
commitment period 2008 to 2012. The Kyoto Protocol has
not yet entered into force (September 2001).
La Niña
See El Niño Southern Oscillation.
Land use
The total of arrangements, activities, and inputs undertaken
in a certain land cover type (a set of human actions). The social
and economic purposes for which land is managed (e.g.,
grazing, timber extraction, and conservation).
Land-use change
A change in the use or management of land by humans, which
may lead to a change in land cover. Land cover and land-use
change may have an impact on the albedo, evapotranspiration,
sources, and sinks of greenhouse gases, or other properties of
the climate system, and may thus have an impact on climate,
locally or globally. See also the IPCC Special Report on Land
Use, Land-Use Change, and Forestry (IPCC, 2000b).
Landslide
A mass of material that has slipped downhill by gravity, often
assisted by water when the material is saturated; rapid
movement of a mass of soil, rock, or debris down a slope.
Leakage
The part of emissions reductions in Annex B countries that
may be offset by an increase of the emission in the nonconstrained
countries above their baseline levels. This can
occur through (i) relocation of energy-intensive production in
non-constrained regions; (ii) increased consumption of fossil
fuels in these regions through decline in the international price
of oil and gas triggered by lower demand for these energies;
and (iii) changes in incomes (thus in energy demand) because
of better terms of trade. Leakage also refers to the situation in
which a carbon sequestration activity (e.g., tree planting) on
one piece of land inadvertently, directly or indirectly, triggers
an activity, which in whole or part, counteracts the carbon
effects of the initial activity.
Lifetime
Lifetime is a general term used for various time scales
characterizing the rate of processes affecting the concentration
of trace gases. In general, lifetime denotes the average length
of time that an atom or molecule spends in a given reservoir,
such as the atmosphere or oceans. The following lifetimes
may be distinguished:
“Turnover time” (T) or “atmospheric lifetime” is the ratio
of the mass M of a reservoir (e.g., a gaseous compound in
the atmosphere) and the total rate of removal S from the
reservoir: T = M/S. For each removal process separate
turnover times can be defined. In soil carbon biology, this
is referred to as Mean Residence Time.
“Adjustment time,” “response time,” or “perturbation
lifetime” (Ta) is the time scale characterizing the decay of
an instantaneous pulse input into the reservoir. The term
adjustment time is also used to characterize the adjustment
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of the mass of a reservoir following a step change in the
source strength. Half-life or decay constant is used to quantify
a first-order exponential decay process. See response time
for a different definition pertinent to climate variations.
The term “lifetime” is sometimes used, for simplicity, as a
surrogate for “adjustment time.”
In simple cases, where the global removal of the compound is
directly proportional to the total mass of the reservoir, the
adjustment time equals the turnover time: T = Ta. An example
is CFC-11 which is removed from the atmosphere only by
photochemical processes in the stratosphere. In more complicated
cases, where several reservoirs are involved or where the removal
is not proportional to the total mass, the equality T = Ta no
longer holds. Carbon dioxide is an extreme example. Its turnover
time is only about 4 years because of the rapid exchange between
atmosphere and the ocean and terrestrial biota. However, a
large part of that CO2 is returned to the atmosphere within a
few years. Thus, the adjustment time of CO2 in the atmosphere
is actually determined by the rate of removal of carbon from
the surface layer of the oceans into its deeper layers. Although
an approximate value of 100 years may be given for the
adjustment time of CO2 in the atmosphere, the actual
adjustment is faster initially and slower later on. In the case of
methane, the adjustment time is different from the turnover
time, because the removal is mainly through a chemical
reaction with the hydroxyl radical OH, the concentration of
which itself depends on the CH4 concentration. Therefore the
CH4 removal S is not proportional to its total mass M.
Lithosphere
The upper layer of the solid Earth, both continental and
oceanic, which is composed of all crustal rocks and the cold,
mainly elastic, part of the uppermost mantle. Volcanic activity,
although part of the lithosphere, is not considered as part of
the climate system, but acts as an external forcing factor.
Leapfrogging
Leapfrogging (or technological leapfrogging) refers to the
opportunities in developing countries to bypass several stages
of technology development, historically observed in industrialized
countries, and apply the most advanced presently available
technologies in the energy and other economic sectors, through
investments in technological development and capacity
building.
Level of scientific understanding
This is an index on a 4-step scale (High, Medium, Low, and
Very Low) designed to characterize the degree of scientific
understanding of the radiative forcing agents that affect climate
change. For each agent, the index represents a subjective
judgement about the reliability of the estimate of its forcing,
involving such factors as the assumptions necessary to evaluate
the forcing, the degree of knowledge of the physical/chemical
mechanisms determining the forcing, and the uncertainties
surrounding the quantitative estimate.
Local Agenda 21
Local Agenda 21s are the local plans for environment and
development that each local authority is meant to develop
through a consultative process with their populations, with
particular attention paid to involving women and youth. Many
local authorities have developed Local Agenda 21s through
consultative processes as a means of reorienting their policies,
plans, and operations towards the achievement of sustainable
development goals. The term comes from Chapter 28 of
Agenda 21—the document formally endorsed by all
government representatives attending the United Nations
Conference on Environment and Development (also known
as the Earth Summit) in Rio de Janeiro in 1992.
Lock-in technologies and practices
Technologies and practices that have market advantages arising
from existing institutions, services, infrastructure, and available
resources; they are very difficult to change because of their
widespread use and the presence of associated infrastructure
and socio-cultural patterns.
Maladaptation
Any changes in natural or human systems that inadvertently
increase vulnerability to climatic stimuli; an adaptation that
does not succeed in reducing vulnerability but increases it
instead.
Malaria
Endemic or epidemic parasitic disease caused by species of
the genus Plasmodium (protozoa) and transmitted by mosquitoes
of the genus Anopheles; produces high fever attacks and
systemic disorders, and kills approximately 2 million people
every year.
Marginal cost pricing
The pricing of commercial goods and services such that the
price equals the additional cost that arises from the expansion
of production by one additional unit.
Market barriers
In the context of mitigation of climate change, conditions that
prevent or impede the diffusion of cost-effective technologies
or practices that would mitigate greenhouse gas emissions.
Market-based incentives
Measures intended to use price mechanisms (e.g., taxes and
tradable permits) to reduce greenhouse gas emissions.
Market impacts
Impacts that are linked to market transactions and directly
affect Gross Domestic Product (a country’s national
accounts)—for example, changes in the supply and price of
agricultural goods. See also non-market impacts.

Annex B Glossary of Terms
Market penetration
Market penetration is the share of a given market that is
provided by a particular good or service at a given time.
Market potential
The portion of the economic potential for greenhouse gas
emissions reductions or energy-efficiency improvements that
could be achieved under forecast market conditions, assuming
no new policies and measures. See also economic potential,
socio-economic potential, and technological potential.
Mass movement
Applies to all unit movements of land material propelled and
controlled by gravity.
Mean Sea Level (MSL)
Mean Sea Level is normally defined as the average relative
sea level over a period, such as a month or a year, long enough
to average out transients such as waves. See also sea-level
rise.
Methane (CH4)
A hydrocarbon that is a greenhouse gas produced through
anaerobic (without oxygen) decomposition of waste in
landfills, animal digestion, decomposition of animal wastes,
production and distribution of natural gas and oil, coal
production, and incomplete fossil-fuel combustion. Methane
is one of the six greenhouse gases to be mitigated under the
Kyoto Protocol.
Methane recovery
Method by which methane emissions (e.g., from coal mines
or waste sites) are captured and then reused either as a fuel or
for some other economic purpose (e.g., reinjection in oil or
gas reserves).
Meeting of the Parties (to the Kyoto Protocol) (MOP)
The Conference of the Parties of the United Nations Framework
Convention on Climate Change will serve as the Meeting of
the Parties (MOP), the supreme body of the Kyoto Protocol,
but only Parties to the Kyoto Protocol may participate in
deliberations and make decisions. Until the Protocol enters
into force, MOP cannot meet.
Mitigation
An anthropogenic intervention to reduce the sources or
enhance the sinks of greenhouse gases.
Mitigative capacity
The social, political, and economic structures and conditions
that are required for effective mitigation.
Mixed layer
The upper region of the ocean well-mixed by interaction with
the overlying atmosphere.
Mixing ratio
See mole fraction.
Model hierarchy
See climate model.
Mole fraction
Mole fraction, or mixing ratio, is the ratio of the number of
moles of a constituent in a given volume to the total number
of moles of all constituents in that volume. It is usually reported
for dry air. Typical values for long-lived greenhouse gases are
in the order of mmol/mol (parts per million: ppm), nmol/mol
(parts per billion: ppb), and fmol/mol (parts per trillion: ppt).
Mole fraction differs from volume mixing ratio, often expressed
in ppmv, etc., by the corrections for non-ideality of gases. This
correction is significant relative to measurement precision for
many greenhouse gases (Schwartz and Warneck, 1995).
Monsoon
Wind in the general atmospheric circulation typified by a
seasonal persistent wind direction and by a pronounced change
in direction from one season to the next.
Montane
The biogeographic zone made up of relatively moist, cool
upland slopes below timberline and characterized by the
presence of large evergreen trees as a dominant life form.
Montreal Protocol
The Montreal Protocol on substances that deplete the ozone
layer was adopted in Montreal in 1987, and subsequently
adjusted and amended in London (1990), Copenhagen (1992),
Vienna (1995), Montreal (1997), and Beijing (1999). It
controls the consumption and production of chlorine- and
bromine-containing chemicals that destroy stratospheric ozone,
such as chlorofluorocarbons (CFCs), methyl chloroform,
carbon tetrachloride, and many others.
Morbidity
Rate of occurrence of disease or other health disorder within a
population, taking account of the age-specific morbidity rates.
Health outcomes include chronic disease incidence/prevalence,
rates of hospitalization, primary care consultations, disability-days
(i.e., days when absent from work), and prevalence of symptoms.
Mortality
Rate of occurrence of death within a population within a
specified time period; calculation of mortality takes account
of age-specific death rates, and can thus yield measures of life
expectancy and the extent of premature death.
Net Biome Production (NBP)
Net gain or loss of carbon from a region. NBP is equal to the
Net Ecosystem Production minus the carbon lost due to a
disturbance (e.g., a forest fire or a forest harvest).

Climate Change 2001 Synthesis Report
IPCC Third Assessment Report
Net carbon dioxide emissions
Difference between sources and sinks of carbon dioxide in a
given period and specific area or region.
Net Ecosystem Production (NEP)
Net gain or loss of carbon from an ecosystem. NEP is equal to
the Net Primary Production minus the carbon lost through
heterotrophic respiration.
Net Primary Production (NPP)
The increase in plant biomass or carbon of a unit of a landscape.
NPP is equal to the Gross Primary Production minus carbon
lost through autotrophic respiration.
Nitrogen fertilization
Enhancement of plant growth through the addition of nitrogen
compounds. In IPCC assessments, this typically refers to
fertilization from anthropogenic sources of nitrogen such as
human-made fertilizers and nitrogen oxides released from
burning fossil fuels.
Nitrogen oxides (NOx)
Any of several oxides of nitrogen.
Nitrous oxide (N2O)
A powerful greenhouse gas emitted through soil cultivation
practices, especially the use of commercial and organic
fertilizers, fossil-fuel combustion, nitric acid production, and
biomass burning. One of the six greenhouse gases to be curbed
under the Kyoto Protocol.
Non-point-source pollution
Pollution from sources that cannot be defined as discrete
points, such as areas of crop production, timber, surface
mining, disposal of refuse, and construction. See also pointsource
pollution.
No-regrets opportunities
See no-regrets policy.
No-regret options
See no-regrets policy.
No-regrets policy
One that would generate net social benefits whether or not
there is climate change. No-regrets opportunities for
greenhouse gas emissions reduction are defined as those
options whose benefits such as reduced energy costs and
reduced emissions of local/regional pollutants equal or exceed
their costs to society, excluding the benefits of avoided climate
change. No-regrets potential is defined as the gap between
the market potential and the socio-economic potential.
No-regrets potential
See no-regrets policy.
Non-Annex B countries/Parties
The countries that are not included in Annex B in the Kyoto
Protocol. See also Annex B countries.
Non-Annex I countries/Parties
The countries that have ratified or acceded to the United
Nations Framework Convention on Climate Change that are
not included in Annex I of the Climate Convention. See also
Annex I countries.
Non-linearity
A process is called “non-linear” when there is no simple
proportional relation between cause and effect. The climate
system contains many such non-linear processes, resulting in
a system with a potentially very complex behavior. Such
complexity may lead to rapid climate change.
Non-market impacts
Impacts that affect ecosystems or human welfare, but that are
not directly linked to market transactions—for example, an
increased risk of premature death. See also market impacts.
North Atlantic Oscillation (NAO)
The North Atlantic Oscillation consists of opposing variations
of barometric pressure near Iceland and near the Azores. On
average, a westerly current, between the Icelandic low pressure
area and the Azores high pressure area, carries cyclones with
their associated frontal systems towards Europe. However,
the pressure difference between Iceland and the Azores fluctuates
on time scales of days to decades, and can be reversed at times.
It is the dominant mode of winter climate variability in the North
Atlantic region, ranging from central North America to Europe.
Ocean conveyor belt
The theoretical route by which water circulates around the entire
global ocean, driven by wind and the thermohaline circulation.
Opportunity
An opportunity is a situation or circumstance to decrease the
gap between the market potential of any technology or practice
and the economic potential, socio-economic potential, or
technological potential.
Opportunity costs
The cost of an economic activity forgone by the choice of
another activity.
Optimal policy
A policy is assumed to be “optimal” if marginal abatement costs
are equalized across countries, thereby minimizing total costs.
Organic aerosol
Aerosol particles consisting predominantly of organic compounds,
mainly C, H, and O, and lesser amounts of other elements
(Charlson and Heintzenberg, 1995). See carbonaceous aerosol.

Annex B Glossary of Terms
Ozone (O3)
Ozone, the triatomic form of oxygen (O3), is a gaseous atmospheric
constituent. In the troposphere it is created both naturally and by
photochemical reactions involving gases resulting from human
activities (photochemical “smog”). In high concentrations,
tropospheric ozone can be harmful to a wide-range of living
organisms. Tropospheric ozone acts as a greenhouse gas. In the
stratosphere, ozone is created by the interaction between solar
ultraviolet radiation and molecular oxygen (O2). Stratospheric
ozone plays a decisive role in the stratospheric radiative balance.
Its concentration is highest in the ozone layer. Depletion of
stratospheric ozone, due to chemical reactions that may be enhanced
by climate change, results in an increased ground-level flux of
ultraviolet-B radiation. See also Montreal Protocol and ozone layer.
Ozone hole
See ozone layer.
Ozone layer
The stratosphere contains a layer in which the concentration
of ozone is greatest, the so-called ozone layer. The layer
extends from about 12 to 40 km. The ozone concentration
reaches a maximum between about 20 and 25 km. This layer
is being depleted by human emissions of chlorine and bromine
compounds. Every year, during the Southern Hemisphere
spring, a very strong depletion of the ozone layer takes place
over the Antarctic region, also caused by human-made chlorine
and bromine compounds in combination with the specific
meteorological conditions of that region. This phenomenon is
called the ozone hole.
Parameterization
In climate models, this term refers to the technique of representing
processes, that cannot be explicitly resolved at the spatial or
temporal resolution of the model (sub-grid scale processes),
by relationships between the area- or time-averaged effect of
such sub-grid-scale processes and the larger scale flow.
Pareto criterion/Pareto optimum
A requirement or status that an individual’s welfare could not be
further improved without making others in the society worse off.
Perfluorocarbons (PFCs)
Among the six greenhouse gases to be abated under the Kyoto
Protocol. These are by-products of aluminum smelting and
uranium enrichment. They also replace chlorofluorocarbons
in manufacturing semiconductors. The Global Warming
Potential of PFCs is 6,500–9,200 times that of carbon dioxide.
Permafrost
Perennially frozen ground that occurs wherever the temperature
remains below 0°C for several years.
Perturbation lifetime
See lifetime.
Photosynthesis
The process by which plants take carbon dioxide (CO2) from
the air (or bicarbonate in water) to build carbohydrates, releasing
oxygen (O2) in the process. There are several pathways of
photosynthesis with different responses to atmospheric CO2
concentrations. See also carbon dioxide fertilization.
Phytoplankton
The plant forms of plankton (e.g., diatoms). Phytoplankton
are the dominant plants in the sea, and are the bast of the entire
marine food web. These single-celled organisms are the
principal agents for photosynthetic carbon fixation in the
ocean. See also zooplankton.
Plankton
Aquatic organisms that drift or swim weakly. See also
phytoplankton and zooplankton.
Point-source pollution
Pollution resulting from any confined, discrete source, such
as a pipe, ditch, tunnel, well, container, concentrated animalfeeding
operation, or floating craft. See also non-point-source
pollution.
Policies and measures
In United Nations Framework Convention on Climate Change
parlance, “policies” are actions that can be taken and/or mandated
by a government—often in conjunction with business and industry
within its own country, as well as with other countries—to
accelerate the application and use of measures to curb
greenhouse gas emissions. “Measures” are technologies,
processes, and practices used to implement policies, which, if
employed, would reduce greenhouse gas emissions below
anticipated future levels. Examples might include carbon or
other energy taxes, standardized fuel-efficiency standards for
automobiles, etc. “Common and coordinated” or “harmonized”
policies refer to those adopted jointly by Parties.
Pool
See reservoir.
Post-glacial rebound
The vertical movement of the continents and sea floor
following the disappearance and shrinking of ice sheets—for
example, since the Last Glacial Maximum (21 ky BP). The
rebound is an isostatic land movement.
Precursors
Atmospheric compounds which themselves are not greenhouse
gases or aerosols, but which have an effect on greenhouse gas
or aerosol concentrations by taking part in physical or chemical
processes regulating their production or destruction rates.
Pre-industrial
See Industrial Revolution.

Climate Change 2001 Synthesis Report
IPCC Third Assessment Report
Present value cost
The sum of all costs over all time periods, with future costs
discounted.
Primary energy
Energy embodied in natural resources (e.g., coal, crude oil,
sunlight, uranium) that has not undergone any anthropogenic
conversion or transformation.
Private cost
Categories of costs influencing an individual’s decision making
are referred to as private costs. See also social cost and total cost.
Profile
A smoothly changing set of concentrations representing a
possible pathway towards stabilization. The word “profile”is
used to distinguish such pathways from emissions pathways,
which are usually referred to as “scenarios.”
Projection (generic)
A projection is a potential future evolution of a quantity or set
of quantities, often computed with the aid of a model.
Projections are distinguished from “predictions” in order to
emphasize that projections involve assumptions concerning,
for example, future socio-economic and technological
developments that may or may not be realized, and are
therefore subject to substantial uncertainty. See also climate
projection and climate prediction.
Proxy
A proxy climate indicator is a local record that is interpreted,
using physical and biophysical principles, to represent some
combination of climate-related variations back in time.
Climate-related data derived in this way are referred to as proxy
data. Examples of proxies are tree ring records, characteristics
of corals, and various data derived from ice cores.
Purchasing Power Parity (PPP)
Estimates of Gross Domestic Product based on the purchasing
power of currencies rather than on current exchange rates. Such
estimates are a blend of extrapolated and regression-based
numbers, using the results of the International Comparison
Program. PPP estimates tend to lower per capita GDPs in
industrialized countries and raise per capita GDPs in developing
countries. PPP is also an acronym for polluter-pays-principle.
Radiative balance
See energy balance.
Radiative forcing
Radiative forcing is the change in the net vertical irradiance
(expressed in Wm-2) at the tropopause due to an internal change
or a change in the external forcing of the climate system, such as,
for example, a change in the concentration of carbon dioxide
or the output of the Sun. Usually radiative forcing is computed
after allowing for stratospheric temperatures to readjust to
radiative equilibrium, but with all tropospheric properties held
fixed at their unperturbed values.
Radiative forcing scenario
A plausible representation of the future development of
radiative forcing associated, for example, with changes in
atmospheric composition or land-use change, or with external
factors such as variations in solar activity. Radiative forcing
scenarios can be used as input into simplified climate models
to compute climate projections.
Rangeland
Unimproved grasslands, shrublands, savannahs, and tundra.
Regeneration
The renewal of a stand of trees through either natural means
(seeded onsite or adjacent stands or deposited by wind, birds,
or animals) or artificial means (by planting seedlings or direct
seeding).
Rapid climate change
The non-linearity of the climate system may lead to rapid
climate change, sometimes called abrupt events or even
surprises. Some such abrupt events may be imaginable, such
as a dramatic reorganization of the thermohaline circulation,
rapid deglaciation, or massive melting of permafrost leading
to fast changes in the carbon cycle. Others may be truly
unexpected, as a consequence of a strong, rapidly changing,
forcing of a non-linear system.
Rebound effect
Occurs because, for example, an improvement in motor
efficiency lowers the cost per kilometer driven; it has the
perverse effect of encouraging more trips.
Reference scenario
See baseline.
Reforestation
Planting of forests on lands that have previously contained
forests but that have been converted to some other use. For a
discussion of the term forest and related terms such as
afforestation, reforestation, and deforestation, see the IPCC
Special Report on Land Use, Land-Use Change, and Forestry
(IPCC, 2000b).
Regulatory measures
Rules or codes enacted by governments that mandate product
specifications or process performance characteristics. See also
standards.
Reinsurance
The transfer of a portion of primary insurance risks to a secondary
tier of insurers (reinsurers); essentially “insurance for insurers.”

Annex B Glossary of Terms
Relative sea level
Sea level measured by a tide gauge with respect to the land
upon which it is situated. See also Mean Sea Level.
(Relative) Sea level secular change
Long-term changes in relative sea level caused by either
eustatic changes (e.g., brought about by thermal expansion)
or changes in vertical land movements.
Renewables
Energy sources that are, within a short time frame relative to
the Earth’s natural cycles, sustainable, and include non-carbon
technologies such as solar energy, hydropower, and wind, as
well as carbon-neutral technologies such as biomass.
Research, development, and demonstration
Scientific and/or technical research and development of new
production processes or products, coupled with analysis and
measures that provide information to potential users regarding
the application of the new product or process; demonstration
tests; and feasibility of applying these products processes via
pilot plants and other pre-commercial applications.
Reserves
Refer to those occurrences that are identified and measured
as economically and technically recoverable with current
technologies and prices. See also resources.
Reservoir
A component of the climate system, other than the atmosphere,
which has the capacity to store, accumulate, or release a
substance of concern (e.g., carbon, a greenhouse gas, or a
precursor). Oceans, soils, and forests are examples of
reservoirs of carbon. Pool is an equivalent term (note that the
definition of pool often includes the atmosphere). The absolute
quantity of substance of concerns, held within a reservoir at a
specified time, is called the stock. The term also means an
artificial or natural storage place for water, such as a lake,
pond, or aquifer, from which the water may be withdrawn for
such purposes as irrigation, water supply, or irrigation.
Resilience
Amount of change a system can undergo without changing
state.
Resource base
Resource base includes both reserves and resources.
Resources
Resources are those occurrences with less certain geological
and/or economic characteristics, but which are considered
potentially recoverable with foreseeable technological and
economic developments.
Respiration
The process whereby living organisms converts organic matter
to carbon dioxide, releasing energy and consuming oxygen.
Response time
The response time or adjustment time is the time needed for
the climate system or its components to re-equilibrate to a new
state, following a forcing resulting from external and internal
processes or feedbacks. It is very different for various components
of the climate system. The response time of the troposphere is
relatively short, from days to weeks, whereas the stratosphere comes
into equilibrium on a time scale of typically a few months. Due
to their large heat capacity, the oceans have a much longer response
time, typically decades, but up to centuries or millennia. The
response time of the strongly coupled surface-troposphere system
is, therefore, slow compared to that of the stratosphere, and
mainly determined by the oceans. The biosphere may respond
fast (e.g., to droughts), but also very slowly to imposed changes.
See lifetime for a different definition of response time pertinent
to the rate of processes affecting the concentration of trace gases.
Revenue recycling
See interaction effect.
Runoff
That part of precipitation that does not evaporate. In some
countries, runoff implies surface runoff only.
S profiles
The carbon dioxide concentration profiles leading to stabilization
defined in the IPCC 1994 assessment (Enting et al., 1994;
Schimel et al., 1995). For any given stabilization level, these
profiles span a wide range of possibilities. The S stands for
“Stabilization.” See also WRE profiles.
Safe-landing approach
See tolerable windows approach.
Salinization
The accumulation of salts in soils.
Saltwater intrusion/encroachment
Displacement of fresh surfacewater or groundwater by the
advance of saltwater due to its greater density, usually in coastal
and estuarine areas.
Scenario (generic)
A plausible and often simplified description of how the future
may develop, based on a coherent and internally consistent set
of assumptions about key driving forces (e.g., rate of technology
change, prices) and relationships. Scenarios are neither predictions
nor forecasts and sometimes may be based on a “narrative
storyline.” Scenarios may be derived from projections, but are
often based on additional information from other sources. See
also SRES scenarios, climate scenario, and emission scenarios.

Climate Change 2001 Synthesis Report
IPCC Third Assessment Report
Sea-level rise
An increase in the mean level of the ocean. Eustatic sea-level
rise is a change in global average sea level brought about by
an alteration to the volume of the world ocean. Relative sealevel
rise occurs where there is a net increase in the level of
the ocean relative to local land movements. Climate modelers
largely concentrate on estimating eustatic sea-level change.
Impact researchers focus on relative sea-level change.
Seawall
A human-made wall or embankment along a shore to prevent
wave erosion.
Semi-arid regions
Ecosystems that have more than 250 mm precipitation per year
but are not highly productive; usually classified as rangelands.
Sensitivity
Sensitivity is the degree to which a system is affected, either
adversely or beneficially, by climate-related stimuli. The effect
may be direct (e.g., a change in crop yield in response to a change
in the mean, range, or variability of temperature) or indirect
(e.g., damages caused by an increase in the frequency of coastal
flooding due to sea-level rise). See also climate sensitivity.
Sequential decision making
Stepwise decision making aiming to identify short-term strategies
in the face of long-term uncertainties, by incorporating additional
information over time and making mid-course corrections.
Sequestration
The process of increasing the carbon content of a carbon
reservoir other than the atmosphere. Biological approaches
to sequestration include direct removal of carbon dioxide from
the atmosphere through land-use change, afforestation,
reforestation, and practices that enhance soil carbon in agriculture.
Physical approaches include separation and disposal of carbon
dioxide from flue gases or from processing fossil fuels to
produce hydrogen- and carbon dioxide-rich fractions and longterm
storage in underground in depleted oil and gas reservoirs,
coal seams, and saline aquifers. See also uptake.
Silt
Unconsolidated or loose sedimentary material whose constituent
rock particles are finer than grains of sand and larger than
clay particles.
Silviculture
Development and care of forests.
Sink
Any process, activity or mechanism that removes a greenhouse
gas, an aerosol, or a precursor of a greenhouse gas or aerosol
from the atmosphere.
Snowpacks
A seasonal accumulation of slow-melting snow.
Social cost
The social cost of an activity includes the value of all the resources
used in its provision. Some of these are priced and others are not.
Non-priced resources are referred to as externalities. It is the
sum of the costs of these externalities and the priced resources
that makes up the social cost. See also private cost and total cost.
Socio-economic potential
The socio-economic potential represents the level of greenhouse
gas mitigation that would be approached by overcoming social
and cultural obstacles to the use of technologies that are costeffective.
See also economic potential, market potential, and
technology potential.
Soil moisture
Water stored in or at the land surface and available for evaporation.
Solar activity
The Sun exhibits periods of high activity observed in numbers
of sunspots, as well as radiative output, magnetic activity, and
emission of high energy particles. These variations take place
on a range of time scales from millions of years to minutes.
See also solar cycle.
Solar (“11 year”) cycle
A quasi-regular modulation of solar activity with varying
amplitude and a period of between 9 and 13 years.
Solar radiation
Radiation emitted by the Sun. It is also referred to as shortwave
radiation. Solar radiation has a distinctive range of
wavelengths (spectrum) determined by the temperature of the
Sun. See also infrared radiation.
Soot particles
Particles formed during the quenching of gases at the outer edge
of flames of organic vapors, consisting predominantly of carbon,
with lesser amounts of oxygen and hydrogen present as carboxyl
and phenolic groups and exhibiting an imperfect graphitic structure
(Charlson and Heintzenberg, 1995). See also black carbon.
Source
Any process, activity, or mechanism that releases a greenhouse
gas, an aerosol, or a precursor of a greenhouse gas or aerosol
into the atmosphere.
Southern Oscillation
See El Niño Southern Oscillation.
Spatial and temporal scales
Climate may vary on a large range of spatial and temporal scales.
Spatial scales may range from local (less than 100,000 km2),

Annex B Glossary of Terms
through regional (100,000 to 10 million km2) to continental
(10 to 100 million km2). Temporal scales may range from
seasonal to geological (up to hundreds of millions of years).
Spill-over effect
The economic effects of domestic or sectoral mitigation measures
on other countries or sectors. In this report, no assessment is made
on environmental spillover effects. Spillover effects can be positive
or negative and include effects on trade, carbon leakage, transfer,
and diffusion of environmentally sound technology and other issues.
SRES scenarios
SRES scenarios are emissions scenarios developed by
Nakicenovic et al. (2000) and used, among others, as a basis
for the climate projections in the IPCC WGI contribution to
the Third Assessment Report (IPCC, 2001a). The following
terms are relevant for a better understanding of the structure
and use of the set of SRES scenarios:
(Scenario) Family: Scenarios that have a similar demographic,
societal, economic, and technical-change storyline. Four
scenario families comprise the SRES scenario set: A1, A2,
B1, and B2.
(Scenario) Group: Scenarios within a family that reflect a
consistent variation of the storyline. The A1 scenario family
includes four groups designated as A1T, A1C, A1G, and A1B
that explore alternative structures of future energy systems.
In the Summary for Policymakers of Nakicenovic et al.
(2000), the A1C and A1G groups have been combined into
one “Fossil-Intensive” A1FI scenario group. The other three
scenario families consist of one group each. The SRES scenario
set reflected in the Summary for Policymakers of Nakicenovic
et al. (2000) thus consist of six distinct scenario groups, all
of which are equally sound and together capture the range of
uncertainties associated with driving forces and emissions.
Illustrative Scenario: A scenario that is illustrative for each
of the six scenario groups reflected in the Summary for
Policymakers of Nakicenovic et al. (2000). They include
four revised scenario markers for the scenario groups A1B,
A2, B1, B2, and two additional scenarios for the A1FI and
A1T groups. All scenario groups are equally sound.
(Scenario) Marker: A scenario that was originally posted in
draft form on the SRES website to represent a given scenario
family. The choice of markers was based on which of the initial
quantifications best reflected the storyline, and the features
of specific models. Markers are no more likely than other
scenarios, but are considered by the SRES writing team as
illustrative of a particular storyline. They are included in
revised form in Nakicenovic et al. (2000). These scenarios
have received the closest scrutiny of the entire writing team
and via the SRES open process. Scenarios have also been
selected to illustrate the other two scenario groups.
(Scenario) Storyline: A narrative description of a scenario
(or family of scenarios) highlighting the main scenario
characteristics, relationships between key driving forces,
and the dynamics of their evolution.
Stabilization
The achievement of stabilization of atmospheric concentrations
of one or more greenhouse gases (e.g., carbon dioxide or a
CO2-equivalent basket of greenhouse gases).
Stabilization analysis
In this report, this refers to analyses or scenarios that address
the stabilization of the concentration of greenhouse gases.
Stabilization scenarios
See stabilization analysis.
Stakeholders
Person or entity holding grants, concessions, or any other type
of value that would be affected by a particular action or policy.
Standards
Set of rules or codes mandating or defining product performance
(e.g., grades, dimensions, characteristics, test methods, and
rules for use). International product and/or technology or
performance standards establish minimum requirements for
affected products and/or technologies in countries where they
are adopted. The standards reduce greenhouse gas emissions
associated with the manufacture or use of the products and/or
application of the technology. See also regulatory measures.
Stimuli (climate-related)
All the elements of climate change, including mean climate
characteristics, climate variability, and the frequency and
magnitude of extremes.
Stock
See reservoir.
Storm surge
The temporary increase, at a particular locality, in the height
of the sea due to extreme meteorological conditions (low
atmospheric pressure and/or strong winds). The storm surge
is defined as being the excess above the level expected from
the tidal variation alone at that time and place.
Storyline
See SRES scenarios.
Streamflow
Water within a river channel, usually expressed in m3 sec-1.
Stratosphere
The highly stratified region of the atmosphere above the
troposphere extending from about 10 km (ranging from 9 km in
high latitudes to 16 km in the tropics on average) to about 50 km.
Structural change
Changes, for example, in the relative share of Gross Domestic
Product produced by the industrial, agricultural, or services sectors
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Climate Change 2001 Synthesis Report
IPCC Third Assessment Report
of an economy; or more generally, systems transformations
whereby some components are either replaced or potentially
substituted by other ones.
Submergence
A rise in the water level in relation to the land, so that areas of
formerly dry land become inundated; it results either from a
sinking of the land or from a rise of the water level.
Subsidence
The sudden sinking or gradual downward settling of the Earth’s
surface with little or no horizontal motion.
Subsidy
Direct payment from the government to an entity, or a tax reduction
to that entity, for implementing a practice the government wishes
to encourage. Greenhouse gas emissions can be reduced by
lowering existing subsidies that have the effect of raising
emissions, such as subsidies to fossil-fuel use, or by providing
subsidies for practices that reduce emissions or enhance sinks
(e.g., for insulation of buildings or planting trees).
Sulfur hexafluoride (SF6)
One of the six greenhouse gases to be curbed under the Kyoto
Protocol. It is largely used in heavy industry to insulate highvoltage
equipment and to assist in the manufacturing of cablecooling
systems. Its Global Warming Potential is 23,900.
Sunspots
Small dark areas on the Sun. The number of sunspots is higher
during periods of high solar activity, and varies in particular
with the solar cycle.
Surface runoff
The water that travels over the soil surface to the nearest surface
stream; runoff of a drainage basin that has not passed beneath
the surface since precipitation.
Sustainable development
Development that meets the needs of the present without
compromising the ability of future generations to meet their
own needs.
Targets and time tables
A target is the reduction of a specific percentage of greenhouse
gas emissions from a baseline date (e.g., “below 1990 levels”)
to be achieved by a set date or time table (e.g., 2008 to 2012).
For example, under the Kyoto Protocol’s formula, the European
Union has agreed to reduce its greenhouse gas emissions by
% below 1990 levels by the 2008 to 2012 commitment period.
These targets and time tables are, in effect, an emissions cap
on the total amount of greenhouse gas emissions that can be
emitted by a country or region in a given time period.
Tax-interaction effect
See interaction effect.
Technological potential
The amount by which it is possible to reduce greenhouse gas
emissions or improve energy efficiency by implementing a technology
or practice that has already been demonstrated. See also economic
potential, market potential, and socio-economic potential.
Technology
A piece of equipment or a technique for performing a particular
activity.
Technology or performance standard
See standards.
Technology transfer
The broad set of processes that cover the exchange of knowledge,
money, and goods among different stakeholders that lead to the
spreading of technology for adapting to or mitigating climate
change. As a generic concept, the term is used to encompass
both diffusion of technologies and technological cooperation
across and within countries.
Thermal erosion
The erosion of ice-rich permafrost by the combined thermal
and mechanical action of moving water.
Thermal expansion
In connection with sea level, this refers to the increase in volume
(and decrease in density) that results from warming water. A
warming of the ocean leads to an expansion of the ocean
volume and hence an increase in sea level.
Thermohaline circulation
Large-scale density-driven circulation in the ocean, caused by
differences in temperature and salinity. In the North Atlantic, the
thermohaline circulation consists of warm surface water flowing
northward and cold deepwater flowing southward, resulting
in a net poleward transport of heat. The surface water sinks in
highly restricted sinking regions located in high latitudes.
Thermokarst
Irregular, hummocky topography in frozen ground caused by
melting of ice.
Tide gauge
A device at a coastal location (and some deep sea locations)
which continuously measures the level of the sea with respect
to the adjacent land. Time-averaging of the sea level so
recorded gives the observed relative sea level secular changes.
Time scale
Characteristic time for a process to be expressed. Since many
processes exibit most of their effects early, and then have a long

Annex B Glossary of Terms
period during which they gradually approach full expression,
for the purpose of this report the time scale is numerically defined
as the time required for a perturbation in a process to show at
least half of its final effect.
Tolerable-windows approach
These approaches analyze greenhouse gas emissions as they
would be constrained by adopting a long-term climate—rather
than greenhouse gas concentration stabilization—target (e.g.,
expressed in terms of temperature or sea level changes or the
rate of such changes). The main objective of these approaches
is to evaluate the implications of such long-term targets for shortor
medium-term “tolerable” ranges of global greenhouse gas
emissions. Also referred to as safe-landing approaches.
Top-down models
The terms “top” and “bottom” are shorthand for aggregate
and disaggregated models. The top-down label derives from
how modelers applied macro-economic theory and
econometric techniques to historical data on consumption,
prices, incomes, and factor costs to model final demand for
goods and services, and supply from main sectors, like the
energy sector, transportation, agriculture, and industry.
Therefore, top-down models evaluate the system from
aggregate economic variables, as compared to bottom-up
models that consider technological options or project specific
climate change mitigation policies. Some technology data
were, however, integrated into top-down analysis and so the
distinction is not that clear-cut.
Total cost
All items of cost added together. The total cost to society is
made up of both the external cost and the private cost, which
together are defined as social cost.
Trade effects
Economic impacts of changes in the purchasing power of a
bundle of exported goods of a country for bundles of goods
imported from its trade partners. Climate policies change the
relative production costs and may change terms of trade
substantially enough to change the ultimate economic balance.
Transient climate response
The globally averaged surface air temperature increase, averaged
over a 20-year period, centered at the time of CO2 doubling
(i.e., at year 70 in a 1% per year compound CO2 increase
experiment with a global coupled climate model).
Tropopause
The boundary between the troposphere and the stratosphere.
Troposphere
The lowest part of the atmosphere from the surface to about
km in altitude in mid-latitudes (ranging from 9 km in high
latitudes to 16 km in the tropics on average) where clouds and
“weather” phenomena occur. In the troposphere, temperatures
generally decrease with height.
Tundra
A treeless, level, or gently undulating plain characteristic of
arctic and subarctic regions.
Turnover time
See lifetime.
Ultraviolet (UV)-B radiation
Solar radiation within a wavelength range of 280-320 nm,
the greater part of which is absorbed by stratospheric ozone.
Enhanced UV-B radiation suppresses the immune system and
can have other adverse effects on living organisms.
Uncertainty
An expression of the degree to which a value (e.g., the future
state of the climate system) is unknown. Uncertainty can result
from lack of information or from disagreement about what is
known or even knowable. It may have many types of sources,
from quantifiable errors in the data to ambiguously defined
concepts or terminology, or uncertain projections of human
behavior. Uncertainty can therefore be represented by quantitative
measures (e.g., a range of values calculated by various models)
or by qualitative statements (e.g., reflecting the judgment of a
team of experts). See Moss and Schneider (2000).
Undernutrition
The result of food intake that is insufficient to meet dietary
energy requirements continuously, poor absorption, and/or
poor biological use of nutrients consumed.
Unique and threatened systems
Entities that are confined to a relatively narrow geographical
range but can affect other, often larger entities beyond their
range; narrow geographical range points to sensitivity to
environmental variables, including climate, and therefore
attests to potential vulnerability to climate change.
United Nations Framework Convention on Climate
Change (UNFCCC)
The Convention was adopted on 9 May 1992 in New York
and signed at the 1992 Earth Summit in Rio de Janeiro by
more than 150 countries and the European Community. Its
ultimate objective is the “stabilization of greenhouse gas
concentrations in the atmosphere at a level that would prevent
dangerous anthropogenic interference with the climate
system.” It contains commitments for all Parties. Under the
Convention, Parties included in Annex I aim to return
greenhouse gas emissions not controlled by the Montreal
Protocol to 1990 levels by the year 2000. The Convention
entered into force in March 1994. See also Kyoto Protocol
and Conference of the Parties (COP).

Climate Change 2001 Synthesis Report
IPCC Third Assessment Report
Uptake
The addition of a substance of concern to a reservoir. The
uptake of carbon-containing substances, in particular carbon
dioxide, is often called (carbon) sequestration. See also
sequestration.
Upwelling
Transport of deeper water to the surface, usually caused by
horizontal movements of surface water.
Urbanization
The conversion of land from a natural state or managed natural
state (such as agriculture) to cities; a process driven by net
rural-to-urban migration through which an increasing percentage
of the population in any nation or region come to live in
settlements that are defined as “urban centres.”
Value added
The net output of a sector after adding up all outputs and
subtracting intermediate inputs.
Values
Worth, desirability, or utility based on individual preferences.
The total value of any resource is the sum of the values of the
different individuals involved in the use of the resource. The
values, which are the foundation of the estimation of costs,
are measured in terms of the willingness to pay (WTP) by
individuals to receive the resource or by the willingness of
individuals to accept payment (WTA) to part with the resource.
Vector
An organism, such as an insect, that transmits a pathogen from
one host to another. See also vector-borne diseases.
Vector-borne diseases
Disease that is transmitted between hosts by a vector organism
such as a mosquito or tick (e.g., malaria, dengue fever, and
leishmaniasis).
Volume mixing ratio
See mole fraction.
Voluntary agreement
An agreement between a government authority and one or more
private parties, as well as a unilateral commitment that is
recognized by the public authority, to achieve environmental
objectives or to improve environmental performance beyond
compliance.
Vulnerability
The degree to which a system is susceptible to, or unable to
cope with, adverse effects of climate change, including climate
variability and extremes. Vulnerability is a function of the
character, magnitude, and rate of climate variation to which a
system is exposed, its sensitivity, and its adaptive capacity.
Water stress
A country is water-stressed if the available freshwater supply
relative to water withdrawals acts as an important constraint
on development. Withdrawals exceeding 20% of renewable
water supply has been used as an indicator of water stress.
Water-use efficiency
Carbon gain in photosynthesis per unit water lost in
evapotranspiration. It can be expressed on a short-term basis
as the ratio of photosynthetic carbon gain per unit transpirational
water loss, or on a seasonal basis as the ratio of net primary
production or agricultural yield to the amount of available water.
Water withdrawal
Amount of water extracted from water bodies.
WRE profiles
The carbon dioxide concentration profiles leading to stabilization
defined by Wigley, Richels, and Edmonds (1996) whose initials
provide the acronym. For any given stabilization level, these
profiles span a wide range of possibilities. See also S profiles.
Zooplankton
The animal forms of plankton. They consume phytoplankton
or other zooplankton. See also phytoplankton.Annex II
Glossary
Absorption (Refrigeration)
A process by which a material (the absorbent) extracts one or
more substances (absorbates) from a liquid or gaseous medium
that it is in contact with and changes chemically, physically
or both. The process is accompanied by a change in entropy,
which makes it a useful mechanism for a refrigeration cycle.
Water-lithium bromine and ammonia-water →chillers are examples
of absorption chillers.
Adjustment Time
See: →Lifetime in relation to atmospheric concentrations, or →
response time in relation to the climate system.
Aerosol
A suspension of very fine solid or liquid particles in a gas.
Aerosol is also used as a common name for a spray (or ‘aerosol’)
can, in which a container is filled with a product and a
propellant and is pressurized so as to release the product in a
fine spray.
Age of Air
The length of time that a stratospheric air mass has been out of
contact with the well-mixed →troposphere. The content of a
unit element of air at a particular location and particular time
of year in the →stratosphere can be thought of as a mixture of
different air parcels that have taken different routes from the →
tropopause to arrive at that location. The mean age of air at a
specific location is defined as the average transit times of the
elements since their last contact with the tropopause.
Alcohols
→Hydrocarbon derivatives in which at least one hydrogen atom
has been replaced by an -OH group. Alcohols are sometimes
used as solvents.
Annex B Countries/Parties (Kyoto Protocol)
The group of countries included in Annex B in the →Kyoto
Protocol that have agreed to a target for their →greenhouse-gas
emissions. It includes all the →Annex I countries (as amended
in 1998) except Turkey and Belarus. See also: →Non-Annex I
countries/parties.
Annex I Countries/Parties (Climate Convention)
The group of countries included in Annex I (as amended in 1998)
to the →United Nations Framework Convention on Climate
Change (UNFCCC). It includes all the developed countries in
the Organisation of Economic Co-operation and Development
(OECD), and →countries with economies in transition. By
default, the other countries are referred to as →Non-Annex I
countries. See also: →Annex B countries/parties.
Anthropogenic
Resulting from or produced by human beings.
Aqueous Cleaning
Cleaning parts of equipment with water, to which may be added
suitable detergents, saponifiers or other additives.
Article 5(1) Countries (Montreal Protocol)
Developing countries that are →Party to the →Montreal
Protocol. These countries are permitted a ten-year grace period
in the phase-out schedule in the →Montreal Protocol compared
with developed countries.
Note: The definitions in this glossary refer to the use of the terms in the context of this report. A ‘→’ indicates that the following
term is also contained in this glossary. The glossary provides an explanation of specific terms as the lead authors intend them to
be interpreted in this report.
450 IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System
Atmosphere
The gaseous envelope surrounding the Earth. The dry atmosphere
consists almost entirely of nitrogen (N2) (78.1% volume
→mixing ratio) and oxygen (O2) (20.9% volume mixing ratio).
The remaining 1% consists of trace gases, such as argon (Ar)
(0.93% volume mixing ratio), helium (He), and radiatively
active →greenhouse gases such as →carbon dioxide (CO2)
(0.037% volume mixing ratio in 2004) and →ozone (O3). In addition,
the atmosphere contains water vapour, whose amount is
highly variable, clouds and both liquid and particulate aerosols.
Most of the matter in the atmosphere occurs in the →troposphere
immediately above the Earth’s surface and the overlying
→stratosphere.
Atmospheric Lifetime
A measure of the average time that a molecule remains intact
once released into the →atmosphere. See also: →Lifetime.
Azeotrope (Refrigeration)
A →blend consisting of one or more →refrigerants of different
volatilities that does not appreciably change in composition or
temperature as it evaporates (boils) or condenses (liquefies) under
constant pressure. Refrigerant blends assigned an R-500 series
number designation by ANSI/ASHRAE 34 are azeotropes.
Compare with: →Zeotrope.
Banks
Banks are the total amount of substances contained in existing
equipment, chemical stockpiles, foams and other products not
yet released to the atmosphere.
Baseline
A non-intervention →scenario used as a base in the analysis of
intervention scenarios. See also: →Business-As-usual (BAU)
Scenario.
Best Practice
For this Report, best practice is considered the lowest achievable
value of halocarbon emission at a given date, using commercially
proven technologies in the production, use, substitution,
recovery and destruction of halocarbon or halocarbon-based
products.
Blends/Mixtures (Refrigeration)
A mixture of two or more pure fluids. Blends are used to achieve
properties that fit many refrigeration purposes. For example, a
mixture of flammable and nonflammable components can result
in a nonflammable blend. Blends can be divided into three
categories: →azeotropic, →non-azeotropic and near-azeotropic
blends.
Blowing Agent (Foams)
A gas, volatile liquid or chemical that generates gas during the
foaming process. The gas creates bubbles or cells in the plastic
structure of a foam.
Bottom-Up Models
A modelling approach that aggregates information from diverse
sources, often including technological and engineering details
in the analysis. Compare with: →Top-down models.
Business-As-Usual (BAU) Scenario (2015, This Report)
A →baseline scenario for the use of →halocarbons and their
alternatives, which assumes that all existing regulation and →
phase-out measures, including the →Montreal Protocol and relevant
national regulations, continue to 2015. The usual practices
(including end-of-life recovery) and emission rates are kept
unchanged up to 2015.
Capital Costs
Costs associated with capital or investment expenditure on land,
plant, equipment and inventories. Unlike labour and operating
costs, capital costs are independent of the level of output for a
given capacity of production.
Carbon Dioxide (CO2)
A naturally occurring gas which occurs as a byproduct of burning
→fossil fuels and biomass, as well as other industrial processes
and land-use changes. It is the principal →anthropogenic
→greenhouse gas that affects the Earth’s radiative balance and
is the reference gas against which other greenhouse gases are
generally measured.
Catalyst
A chemical that acts to speed up or facilitate a chemical reaction,
but is not physically changed or used up in the reaction.
Chiller
A cooling system that removes heat from one medium (water)
and deposits it into another (ambient air or water).
Chlorine Loading
The total amount of chlorine (generally expressed as a →mixing
ratio, or fraction of all air molecules), accounting for the
amount of all chlorine-bearing substances and the number of
atoms of chlorine in each substance.
Chlorocarbons
→Halocarbons containing carbon and chlorine atoms, but no
other →halogen atoms.
Chlorofluorocarbons (CFCs)
→Halocarbons containing only chlorine, fluorine and carbon
atoms. CFCs are both →ozone-depleting substances (ODSs)
and →greenhouse gases.
Class A Fire (Fire Protection)
Fire in ordinary combustible materials, such as wood, cloth, paper,
rubber and many plastics.
Annex II: Glossary 451
Class B Fire (Fire Protection)
Fire in flammable liquids, oils, greases, tars, oil-base paints,
lacquers and flammable gases.
Class C Fire (Fire Protection)
Fire that involves energized electrical equipment where the electrical
resistivity of the extinguishing media is of importance.
Clean Agent (Fire Protection)
An electrically non-conducting, volatile or gaseous fire-extinguishing
agent that does not leave a residue upon evaporation.
Clean Development Mechanism (CDM)
Defined in Article 12 of the →Kyoto Protocol, the Clean
Development Mechanism is intended to meet two objectives:
(1) to assist →non-Annex I Parties in achieving sustainable development
and in contributing to the ultimate objective of the
convention; and (2) to assist →Annex I Parties in achieving
compliance with their quantified emission limitation and reduction
commitments. Certified emission reductions from Clean
Development Mechanism projects undertaken in non-Annex I
countries that limit or reduce →greenhouse-gas emissions, when
certified by operational entities designated by the→Conference
of the Parties/Meeting of the Parties, can be accrued to the investor
(government or industry) from Parties in →Annex B. A
share of the proceeds from the certified project activities is used
to cover administrative expenses as well as to assist developing
country Parties that are particularly vulnerable to the adverse
effects of →climate change to meet the costs of adaptation.
Climate
Climate in a narrow sense is usually defined as the ‘average
weather’, or more rigorously, as the statistical description in
terms of the mean and variability of relevant quantities over a
period of time ranging from months to thousands or millions
of years. The classical period is 30 years, as defined by the →
World Meteorological Organization (WMO). These quantities
are most often surface variables such as temperature, precipitation,
and wind. Climate in a wider sense is the state, including a
statistical description, of the climate system.
Climate Change
Climate change refers to a statistically significant variation in
either the mean state of the →climate or in its variability, persisting
for an extended period (typically decades or longer).
Climate change may be due to natural internal processes or external
forcings, or to persistent →anthropogenic changes in the
composition of the atmosphere or in land use.
Note that Article 1 of the →Framework Convention on
Climate Change (UNFCCC) defines ‘climate change’ as ‘a
change of climate which is attributed directly or indirectly to
human activity that alters the composition of the global atmosphere
and which is in addition to natural climate variability,
observed over comparable time periods’. The UNFCCC thus
makes a distinction between ‘climate change’ attributable to human
activities altering the atmospheric composition, and ‘climate
variability’ attributable to natural causes.
Climate Feedback
An interaction mechanism between processes in the →climate
system occurring when the result of an initial process triggers
changes in a second process that in turn influences the initial
one. A positive feedback intensifies the original process, whereas
a negative feedback weakens it.
Climate Scenario
A plausible and often simplified representation of the future
climate, based on a coherent and internally consistent set of
driving forces and key relations, that has been constructed for
use in investigating the potential consequences of →anthropogenic
→climate change, and often serves as input to impact
models. Climate →projections often serve as the raw material
for constructing climate scenarios, but climate scenarios usually
require additional information, such as the baseline current
climate. A climate-change scenario is the difference between a
climate scenario and the current climate.
Climate Sensitivity
In IPCC Reports, equilibrium climate sensitivity refers to the
equilibrium change in global mean surface temperature following
a doubling of the atmospheric (→equivalent) →carbon
dioxide (CO2) concentrations. More generally, equilibrium climate
sensitivity refers to the equilibrium change in surface air
temperature following a unit change in →radiative forcing (in
units of °C per (W m–2)).
In practice, the evaluation of the equilibrium climate sensitivity
requires very long simulations with coupled general
circulation models. The effective climate sensitivity is a related
measure that circumvents this requirement. It is evaluated from
model output for evolving non-equilibrium conditions. It is a
measure of the strengths of the →feedbacks at a particular time
and may vary with forcing history and climate state.
Climate System
The highly complex system that consists of five major components:
the →atmosphere, the hydrosphere, the cryosphere, the
land surface and the biosphere, as well as of the interactions
between them. The climate system evolves over time under the
influence of its own internal dynamics and because of external
forcings, such as volcanic eruptions, solar variations and human-
induced forcings (such as the changing composition of the
atmosphere and land-use change).
Climate Variability
Variations in the mean state and other statistics (such as the
standard deviation and the occurrence of extremes) of the →
climate on all temporal and spatial scales beyond that of individual
weather events. Climate variability may be caused by
natural internal processes within the →climate system (internal
variability), or by variations in natural or anthropogenic external
forcings (external variability). See also: →Climate change.
452 IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System
CO2-Equivalent
The amount of →carbon dioxide (CO2) that would cause the
same amount of →radiative forcing as a given amount of another
→greenhouse gas. When used with concentrations this refers
to the instantaneous radiative forcing caused by the greenhouse
gas or the equivalent amount of CO2. When used with emissions
this refers to the time-integrated radiative forcing over a
specified time horizon caused by the change in concentration
produced by the emissions. See also: →Global warming potential.
Coefficient of Performance (COP) (Refrigeration)
A measure of the energy efficiency of a refrigerating system.
It is defined as the ratio between the refrigerating capacity and
the electric power consumed by the system. The COP is primarily
dependant on the working cycle and the temperature levels
(evaporating/condensing temperature) as well as on the properties
of the →refrigerant, system design and size.
Column Ozone
The total amount of →ozone in a vertical column above the
Earth’s surface. Column ozone is measured in →Dobson units
(DU).
Commercialization
A sequence of actions necessary to achieve market entry and
general market competitiveness of new technologies, processes
and products.
Compressor Discharge Temperature (Refrigeration)
The temperature of a gas at the high-pressure outlet from the
compressor (superheated gas). The gas temperature is typically
30°C to 40°C higher than the condensing temperature at saturation
pressure, mainly depending on the evaporating/condensing
temperature, →refrigerant properties and the compressor
energy efficiency.
Conference of the Parties (COP) (Climate Convention)
The supreme body of the →United Nations Framework
Convention on Climate Change (UNFCCC), comprising countries
that have ratified or acceded to the UNFCCC. See also: →
Conference of the Parties/Meeting of the Parties and →Meeting
of the Parties.
Conference of the Parties/Meeting of the Parties (COP/
MOP) (Climate Convention)
The →Conference of the Parties of the →United Nations
Framework Convention on Climate Change (UNFCCC) will
serve as the →Meeting of the Parties (MOP), the supreme body
of the →Kyoto Protocol, but only Parties to the Kyoto Protocol
may participate in deliberations and make decisions.
Containment (Refrigeration)
The application of service techniques or special equipment designed
to preclude or reduce loss of →refrigerant from equipment
during installation, operation, service or disposal of refrigeration
and air-conditioning equipment.
Controlled Substance
Under the →Montreal Protocol, any →ozone-depleting substance
(ODS) that is subject to control measures, such as a →
phase-out requirement.
Cost Effective
A criterion that specifies that a technology or measure delivers
a good or service at equal or lower cost than current practice, or
the least-cost alternative for the achievement of a given target.
Countries with Economies in Transition (CEITs)
Countries with national economies in the process of changing
from a planned economic system to a market economy.
Destruction
Destruction of →ozone-depleting substances (ODSs) by approved
destruction plants, in order to avoid their emissions.
Detergent
A product designed to render, for example, oils and greases
soluble in water; usually made from synthetic →surfactants.
Dobson Unit (DU)
A unit to measure total →column ozone. The number of Dobson
units is the thickness, in units of 10–5 m, that the ozone column
would occupy if compressed into a layer of uniform density at
a pressure of 1013 hPa and a temperature of 0°C. One DU corresponds
to a column of ozone containing 2.69 × 1020 molecules
per square meter. Although column ozone can vary greatly, 300
DU is a typical value.
Drop-In Replacement (Refrigeration)
The procedure for replacing →CFC refrigerants with non-CFC
refrigerants in existing refrigerating, air-conditioning and heatpump
plants without doing any plant modifications. However,
drop-in procedures are normally referred to as →retrofitting because
plants need minor modifications, such as the change of
lubricant, and the replacement of the expansion device and the
desiccant material.
Dry Powder Inhaler (DPI) (Medical Aerosols)
An alternate technology to →metered dose inhalers (MDIs) that
can be used if the medication being dispensed can be satisfactorily
formulated as microfine powder, thus eliminating the use
of a chemical propellant.
Emission Factor
The coefficient that relates actual →emissions to activity data
as a standard rate of emission per unit of activity.
Emissions
The release of gases or →aerosols into the →atmosphere over a
specified area and period of time.
Annex II: Glossary 453
Emission Scenario
A plausible representation of the future development of →emissions
of substances that are potentially radiatively active (e.g.,
→greenhouse gases and →aerosols), based on a coherent and
internally consistent set of assumptions about driving forces
(such as demographic and socio-economic development, and
technological change) and their key relationships. See also: →
Scenario (generic) and →climate scenario.
The IPCC Special Report on Emission Scenarios (2000)
presented emission scenarios, known as the →SRES scenarios,
which have been used as a basis for the climate projections in
the IPCC Third Assessment Report (2001) and in this report.
Energy Balance
Averaged over the globe and over long time periods, the energy
budget of the →climate system must be in balance. Because the
climate system derives all its energy from the Sun, this balance
implies that, globally, the amount of incoming →solar radiation
must on average be equal to the sum of the outgoing reflected
solar radiation and the outgoing →thermal infrared radiation
emitted by the climate system. A perturbation of this global radiation
balance, be it →anthropogenic or natural, is called →
radiative forcing.
Equivalent-CO2
See →CO2-Equivalent.
Equivalent Effective Stratospheric Chlorine (EESC)
An index of the amount of chlorine (Cl) and bromine (Br) that is
present in the →stratosphere in forms that can contribute to the
depletion of →ozone. The EESC value takes into account different
fractional releases of chlorine or bromine from different
halocarbons and the much higher efficiency of bromine in the
catalytic removal of ozone. See also: →Chlorine loading.
Ethers
Organic compounds with formula R-O-R, where O is an oxygen
atom and R is not a hydrogen atom (H).
Expansion Control Devices (Refrigeration)
A device, such as an expansion valve, expansion orifice, turbine
or capillary tube, that is used to control the mass flow of a →
refrigerant from the high-pressure side to the low-pressure side
of a refrigeration system.
External Costs
The costs arising from any human activity when the agent responsible
for the activity does not take full account of the negative
impacts on others of his or her actions. Similarly, when
the impacts are positive and not accounted for in the actions of
the agent responsible, they are referred to as external benefits.
Emissions of particulate pollution from an industrial installation
affect the health of people in the vicinity, but this is not
often considered, or is given inadequate weight, in private decision
making and there is no market for such impacts. Such
a phenomenon is referred to as an externality, and the costs it
imposes are referred to as the external costs.
External Forcing
See: →Climate system.
Externality
See: →External costs.
Feedback
See: →Climate feedback.
Fluorinated Ethers
→Ethers in which one or more hydrogen atoms have been replaced
by fluorine.
Fluorocarbons
→Halocarbons containing fluorine atoms, including →chlorofluorocarbons
(CFCs), →hydrochlorofluorocarbons (HCFCs),
→hydrofluorocarbons (HFCs), and →perfluorocarbons
(PFCs).
Fluoroketones (FKs)
Organic compounds in which two fully fluorinated alkyl
groups are attached to a carbonyl group (C=O).
Fossil Fuels
Carbon-based fuels derived from geological (fossil) carbon deposits.
Examples include coal, oil and natural gas.
Framework Convention on Climate Change
See:→United Nations Framework Convention on Climate
Change (UNFCCC).
Global Warming Potential (GWP)
An index comparing the climate impact of an emission of a
greenhouse gas relative to that of emitting the same amount of
→carbon dioxide. GWPs are determined as the ratio of the timeintegrated
→radiative forcing arising from a pulse emission of
1 kg of a substance relative to that of 1 kg of carbon dioxide,
over a fixed time horizon. See also: →Radiative forcing.
Greenhouse Effect
→Greenhouse gases in the →atmosphere effectively absorb the
→thermal infrared radiation that is emitted by the Earth’s surface,
by the atmosphere itself, and by clouds. The atmosphere
emits radiation in all directions, including downward to the
Earth’s surface. Greenhouse gases trap heat within the surfacetroposphere
system and raise the temperature of the Earth’s surface.
This is called the natural greenhouse effect.
An increase in the concentration of greenhouse gases leads to
increased absorption of infrared radiation and causes a →radiative
forcing, or energy imbalance, that is compensated for by an
increase in the temperature of the surface-troposphere system.
This is the enhanced greenhouse effect.
454 IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System
Greenhouse Gases (GHGs)
The gaseous constituents of the →atmosphere, both natural and
→anthropogenic, that absorb and emit radiation within the spectrum
of the →thermal infrared radiation that is emitted by the
Earth’s surface, by the atmosphere and by clouds. This property
causes the →greenhouse effect. The primary greenhouse gases
in the Earth’s atmosphere are water vapour (H2O), →carbon dioxide
(CO2), nitrous oxide (N2O), methane (CH4) and →ozone
(O3). Moreover, there are a number of entirely →anthropogenic
greenhouse gases in the atmosphere, such as the →halocarbons
and other chlorine- and bromine-containing substances that are
covered by the →Montreal Protocol. Some other trace gases,
such as sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs),
and perfluorocarbons (PFCs), are also greenhouse gases.
Halocarbons
Chemical compounds containing carbon atoms, and one or
more atoms of the →halogens chlorine (Cl), fluorine (F), bromine
(Br) or iodine (I). Fully halogenated halocarbons contain
only carbon and halogen atoms, whereas partially halogenated
halocarbons also contain hydrogen (H) atoms. Halocarbons
that release chlorine, bromine or iodine into the →stratosphere
cause →ozone depletion. Halocarbons are also →greenhouse
gases. Halocarbons include →chlorofluorocarbons (CFCs),
→hydrochlorofluorocarbons (HCFCs), →hydrofluorocarbons
(HFCs), →perfluorocarbons (PFCs) and →halons.
Halogens
A family of chemical elements with similar chemical properties
that includes fluorine (F), chlorine (Cl), bromine (Br) and
iodine (I).
Halons
Fully halogenated →halocarbons that contain bromine and fluorine
atoms.
Hermetic
An airtight sealed system.
Hermetic Compressors (Refrigeration)
Compressors whose motors are sealed within the →refrigerant
loop and are often cooled by the flow of the →refrigerant-lubricant
mixture directly over the motor windings.
Hydrocarbons (HCs)
Chemical compounds consisting of one or more carbon atoms
surrounded only by hydrogen atoms.
Hydrochlorofluorocarbons (HCFCs)
→Halocarbons containing only hydrogen, chlorine, fluorine and
carbon atoms. Because HCFCs contain chlorine, they contribute
to →ozone depletion. They are also →greenhouse gases.
Hydrofluorocarbons (HFCs)
→Halocarbons containing only carbon, hydrogen and fluorine
atoms. Because HFCs contain no chlorine, bromine or iodine,
they do not deplete the →ozone layer. Like other halocarbons
they are potent →greenhouse gases.
Hydrofluoroethers (HFEs)
Chemicals composed of hydrogen, fluorine and →ether, which
have similar performance characteristics to certain →ozone-depleting
substances (ODSs) that are used as solvents.
Implementation Costs
Costs involved in the implementation of →mitigation options.
These costs are associated with the necessary institutional
changes, information requirements, market size, opportunities
for technology gain and learning, and economic incentives
(grants, subsidies and taxes).
Intergovernmental Panel on Climate Change (IPCC)
The Intergovernmental Panel on Climate Change (IPCC) was
jointly established by the →World Meteorological Organization
(WMO) and the →United Nations Environment Programme
(UNEP) in 1988 to assess scientific, technical and socio-economic
information relevant for the understanding of climate
change, its potential impacts and options for adaptation and
mitigation. It is open to all Members of the UN and of WMO.
The IPCC provides, on request, scientific, technical and socioeconomic
advice to the →Conference of the Parties (COP) to the
→United Nations Framework Convention on Climate Change
(UNFCCC). The IPCC has produced a series of Assessment
Reports, Special Reports, Technical Papers, methodologies,
and other products that have become standard works of reference
and that are widely used by policymakers, scientists, and
other experts.
Kyoto Protocol
The Kyoto Protocol to the →United Nations Framework
Convention on Climate Change (UNFCCC) was adopted at the
Third Session of the →Conference of the Parties (COP) to the
UNFCCC in 1997 in Kyoto, Japan. It contains legally binding
commitments, in addition to those included in the UNFCCC.
Countries included in →Annex B of the Protocol (most OECD
countries and →countries with economies in transition) agreed
to reduce their →anthropogenic →greenhouse-gas emissions
(specifically →carbon dioxide (CO2), methane (CH4), nitrous
oxide (N2O), →hydrofluorocarbons (HFCs), →perfluorocarbons
(PFCs) and sulfur hexafluoride (SF6)) by at least 5% below
1990 levels in the commitment period 2008 to 2012. The
Kyoto Protocol entered into force on 16 February 2005.
Life Cycle Assessment (LCA)
An assessment of the overall environmental impact of a product
over its entire life cycle (manufacture, use and recycling or
disposal).
Life Cycle Climate Performance (LCCP)
A measure of the overall global-warming impact of equipment
based on the total related →emissions of →greenhouse gases
over its entire life cycle. LCCP is an extension of the →total
Annex II: Glossary 455
equivalent warming impact (TEWI). LCCP also takes into account
the direct fugitive emissions arising during manufacture,
and the greenhouse gas emissions associated with their embodied
energy.
Lifetime
Lifetime is a general term used for various time scales characterizing
the rates of processes affecting the concentration of
trace gases. The following lifetimes may be distinguished:
Turnover time (T) is the ratio of the mass (M) of a reservoir
(e.g., a gaseous compound in the →atmosphere) and the total
rate of removal (S) from the reservoir: T = M/S. Separate turnover
times can be defined for each removal process.
Adjustment time or response time (Ta) is a time scale characterizing
the decay of an instantaneous pulse input into the reservoir.
The term adjustment time is also used to characterize the
adjustment of the mass of a reservoir following a step change in
the source strength. Half-life or decay constant is used to quantify
a first-order exponential decay process. See: →Response
time, for a different definition pertinent to climate variations.
The term lifetime is sometimes used, for simplicity, as a surrogate
for adjustment time.
In simple cases, such as CFC-11, where the global removal
rate of the compound is proportional to the total mass of the
reservoir, the adjustment time equals the turnover time: T = Ta.
In more complex cases removal rates are not proportional to the
reservoir mass – for example because of feedback effects – and
this equality no longer holds.
Longwave Radiation
See: →Thermal infrared radiation.
Lower Flammability Limit (LFL)
‘The minimum concentration of a combustible substance that is
capable of propagating a flame through a homogeneous mixture
of the combustible and gaseous oxidizer under the specified
conditions of test’ (ASTM Standard E 681-85). The conditions
of test usually reported for →refrigerants are in dry air in ambient
temperature and pressure.
Lubricant
Typically a substance introduced between moving surfaces to
reduce the friction and wear between them.
Materials Safety Data Sheet (MSDS)
A safety advisory bulletin prepared by chemical producers for a
specific →refrigerant or compound.
Meeting of the Parties (to the Kyoto Protocol) (MOP)
→Conference of the Parties to the →United Nations Framework
Convention on Climate Change serving as the Meeting of the
Parties (MOP) to the →Kyoto Protocol. It is the supreme body
of the Kyoto Protocol. See also: →Conference of the Parties/
Meeting of the parties (COP/MOP).
Meeting of the Parties (to the Montreal Protocol) (MOP)
The supreme body of the Montreal Protocol.
Metered Dose Inhalers (MDIs) (Medical Aerosols)
A method of dispensing inhaled pulmonary drugs. See also: →
Dry powder inhaler (DPI).
Miscible
The ability of two liquids or gases to uniformly dissolve into
each other. Immiscible liquids will separate into two distinguishable
layers.
Mitigation
A human intervention to reduce the sources or enhance the sinks
of →greenhouse gases.
Mixing Ratio
Mixing ratio, or mole fraction, is the ratio of the number of
moles of a constituent in a given volume to the total number of
moles of all constituents in that volume. It is usually reported
for dry air. Typical values for long-lived →greenhouse gases
range from μmol/mol (parts per million: ppm), nmol/mol (parts
per billion: ppb), to fmol/mol (parts per trillion: ppt). Correcting
the mixing ratio for the non-ideality of gases gives the volume
mixing ratio (sometimes expressed in ppmv, etc.).
Mole Fraction
See: →Mixing ratio
Montreal Protocol
The Montreal Protocol on Substances that Deplete the Ozone
Layer was adopted in Montreal in 1987 and subsequently adjusted
and amended in London (1990), Copenhagen (1992),
Vienna (1995), Montreal (1997) and Beijing (1999). It controls
the consumption and production of chlorine- and bromine-containing
chemicals (known as →ozone-depleting substances,
ODSs) that destroy the stratospheric →ozone layer.
Multilateral Fund
Part of the financial mechanism under the →Montreal Protocol,
established by the →Parties to provide financial and technical
assistance to →Article 5 Parties.
Non-Annex I Parties/Countries (Climate Convention)
The countries that have ratified or acceded to the →United
Nations Framework Convention on Climate Change (UNFCCC)
that are not included in →Annex I of the Climate Convention.
Non-Azeotropic (Refrigeration)
A →blend or mixture where the compositions of coexisting liquid
and vapour differ and condensation and evaporation occur
over a range of temperatures. This effect can in some applications
give improved performance in plants with heating/cooling
demand with gliding temperatures. Heating of hot tap water is
one example. Equipment has to be modified to use a non-azeotropic
blend. See also: →zeotropic, →azeotropic.
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Non-Condensable Gases (Refrigeration)
Gases with very low temperature boiling points, which are not
easily condensed. Nitrogen and oxygen are the most common
ones found in →chillers.
Nonlinearity
A process is called ‘nonlinear’ when there is no simple proportional
relation between cause and effect. The →climate system
contains many nonlinear processes, resulting in a system with
potentially very complex behaviour. Such complexity may lead
to rapid climate change.
Normal Boiling Point (NBP)
The boiling point of a compound at atmospheric pressure (1013
hPa).
Not-in-Kind Technologies (NIK)
Not-in-kind technologies achieve the same product objective
without the use of →halocarbons, typically with an alternative
approach or unconventional technique. Examples include the
use of stick or spray pump deodorants to replace CFC-12 aerosol
deodorants; the use of mineral wool to replace CFC, HFC
or HCFC insulating foam; and the use of dry powder inhalers
(DPIs) to replace CFC or HFC metered dose inhalers (MDIs).
One-Component Foam (OCF)
A foam in which the →blowing agent acts both as a frothing
agent and as a propellant. These foams are primarily used for
gap filling (to prevent air infiltration) rather than for thermal insulation
per se. As such the use of blowing agent is fully emissive.
Open Drive (Refrigeration)
A compressor drive motor that is outside the →refrigerant loop
and therefore not directly exposed to the circulating refrigerant.
Ozone
The triatomic form of oxygen (O3), which is a gaseous →atmospheric
constituent. In the →troposphere it is created by
photochemical reactions involving gases occurring naturally
and resulting from →anthropogenic activities (→‘smog’).
Tropospheric ozone acts as a →greenhouse gas. In the →stratosphere
ozone is created by the interaction between solar →
ultraviolet radiation and molecular oxygen (O2). Stratospheric
ozone plays a major role in the stratospheric radiative balance.
Its concentration is highest in the →ozone layer.
Ozone-Depleting Substances (ODSs)
Substances known to deplete the stratospheric →ozone layer.
The ODSs controlled under the →Montreal Protocol and its
Amendments are →chlorofluorocarbons (CFCs), →hydrochlorofluorocarbons
(HCFCs), →halons, methyl bromide (CH3Br),
carbon tetrachloride (CCl4), methyl chloroform (CH3CCl3),
hydrobromofluorocarbons (HBFCs) and bromochloromethane
(CH2BrCl).
Ozone Depletion
Accelerated chemical destruction of the stratospheric →ozone
layer by the presence of substances produced by human activities.
Ozone Depletion Potential (ODP)
A relative index indicating the extent to which a chemical product
may cause →ozone depletion compared with the depletion
caused by CFC-11. Specifically, the ODP of an →ozone-depleting
substance (ODS) is defined as the integrated change in total
ozone per unit mass emission of that substance relative to
the integrated change in total ozone per unit mass emission of
CFC-11.
Ozone Layer
The layer in the →stratosphere where the concentration of →
ozone is greatest. The layer extends from about 12 to 40 km.
This layer is being depleted by →anthropogenic emissions
of chlorine and bromine compounds. Every year, during the
Southern Hemisphere spring, a very strong depletion of the
ozone layer takes place over the Antarctic region. This depletion
is caused by anthropogenic chlorine and bromine compounds in
combination with the specific meteorological conditions of that
region. This phenomenon is called the Antarctic ozone hole.
Party
A country that signs and/or ratifies an international legal instrument
(e.g., a protocol or an amendment to a protocol), indicating
that it agrees to be bound by the rules set out therein. Parties
to the →Montreal Protocol or →Kyoto Protocol are countries
that have signed and ratified these Protocols.
Perfluorocarbons (PFCs)
Synthetically produced →halocarbons containing only carbon
and fluorine atoms. They are characterized by extreme stability,
non-flammability, low toxicity, zero →ozone depleting potential
and high →global warming potential.
Phase-Out
The ending of all production and consumption of a chemical
controlled under the →Montreal Protocol.
Phase-Out Plan
The part of the Country Programme under the →Montreal
Protocol that describes the strategy statement of a government
defining the →phase-out time schedule for each controlled substance
and the government actions to be taken for achieving
phase-out. It contains a prioritized list of projects to be undertaken
and takes into account the specific industrial, political and
legislative situation in the country.
Polar Stratospheric Clouds (PSCs)
A class of clouds composed of particles, including nitric acid
hydrates and ice, that occur at high altitudes (of about 15 to 30
km) in the polar →stratosphere. They occur when the temperature
is very low (below about –95°C), such as in the Antarctic
→polar vortex, and have been observed mainly over Antarctica
Annex II: Glossary 457
in the winter and spring, and occasionally over the Arctic. PSCs
play a major role in →ozone depletion because chlorine is converted
to forms that are highly reactive with ozone through
chemical reactions on or within the cloud particles.
Polar Vortex
A dynamical structure that occurs during the polar winter in
which →stratospheric air acquires a cyclonic circulation about
the pole, with an area of relatively still air in its centre. The
vortex core air (above 16 km in altitude) becomes effectively
isolated from mid-latitude air. The polar vortex over Antarctica
is usually colder and lasts longer (throughout the austral spring)
than the polar vortex over the Arctic.
ppm, ppb, ppt
See: →Mixing ratio.
Precursors
Atmospheric compounds which themselves are not →greenhouse
gasses or →aerosols, but which have an effect on greenhouse-
gas or aerosol concentrations by taking part in physical
or chemical processes regulating their production or destruction
rates.
Present Value Cost
The sum of all costs over all time periods, with future costs
discounted.
Projection (Generic)
A potential future evolution of a quantity or set of quantities,
often computed with the aid of a model. Projections are distinguished
from predictions in order to emphasize that projections
involve assumptions concerning, for example, future socio-economic
and technological developments that may or may not be
realized, and are therefore subject to substantial uncertainty.
Propellant
The component of an →aerosol spray that acts as a forcing
agent to expel the product from the aerosol canister.
Purge System (Refrigeration)
A device used on low-pressure chillers to expel air and other
non-condensables from the circulating →refrigerant.
Push-Pull Method (Refrigeration)
A method for →recovering and →recycling →refrigerant from
a system using a negative pressure (suction) on one side to pull
the old refrigerant out and pumping recycled refrigerant vapour
to the other side to push the old refrigerant through the system.
Radiative Efficiency
A measure of the efficiency of a gas in changing →radiative
forcing. It is calculated as the marginal change in radiative forcing
per unit increase in gas concentration and typically given in
units of W m–2 ppb–1.
Radiative Forcing
Radiative forcing is the change in the net irradiance (expressed
in Watts per square meter: W m–2) at the →tropopause due to
an internal change or a change in the external forcing of the
→climate system, such as a change in the concentration of →
carbon dioxide (CO2) in the atmosphere or in the output of the
Sun. Usually radiative forcing is computed after allowing for
stratospheric temperatures to readjust to radiative equilibrium,
but with all tropospheric properties held fixed at their unperturbed
values. Radiative forcing is called instantaneous if no
change in stratospheric temperature is accounted for. See also:
→Global warming potential.
Radiative Forcing Scenario
A plausible representation of the future development of →radiative
forcing associated, for example, with →anthropogenic
changes in atmospheric composition or in land-use, or with
natural factors such as variations in →solar activity. Radiative
forcing scenarios can be used as input into simplified climate
models to compute climate projections.
Radical
A molecular entity possessing an unpaired electron.
Reclamation
Reprocessing and upgrading of a recovered controlled substance
through mechanisms such as filtering, drying, distillation
and chemical treatment in order to restore the substance to
a specified standard of performance. Chemical analysis is required
to determine that appropriate product specifications are
met. It often involves processing off-site at a central facility.
Recovery
The collection and storage of controlled substances from machinery,
equipment, containment vessels, etc., during servicing
or prior to disposal without necessarily testing or processing it
in any way.
Recycling
Reuse of a recovered controlled substance following a basic
cleaning process such as filtering and drying. For →refrigerants,
recycling normally involves recharge back into equipment
and it often occurs ‘on-site’.
Refrigerant (Refrigeration)
A heat transfer agent, usually a liquid, used in equipment such
as refrigerators, freezers and air conditioners.
Relief Valve (Refrigeration)
A device that vents refrigerant when the pressure in a →chiller
becomes dangerously high. Newer relief valves have a resealing
mechanism so that when the pressure of the chiller returns to a
normal level they reseal and prevent further refrigerant loss.
Research, Development and Demonstration
Scientific or technical research and development of new pro-
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duction processes or products, coupled with analysis and measures
that provide information to potential users regarding the
application of the new products or processes, such demonstration
tests and studies of the feasibility of pilot plants and other
pre-commercial applications.
Response Time (Climate System)
The response time or adjustment time is the time needed for
the →climate system or its components to re-equilibrate to a
new state, following a forcing resulting from external or internal
processes. Different components of the climate system can
have very different response times. The response time of the →
troposphere is relatively short, from days to weeks, whereas the
response time of the →stratosphere is typically a few months.
The oceans have much longer response times, of decades to
millennia, because of their large heat capacity. The response
time of the strongly coupled surface-troposphere system is
mainly determined by the oceans, and is therefore slow compared
with that of the stratosphere. The biosphere can respond
quickly, for example to droughts, but it can also respond very
slowly to other imposed changes.
See: →Lifetime, for the definition of response time in relation
to atmospheric concentrations.
Retrofit
The upgrading or adjustment of equipment so that it can be used
under altered conditions; for example, of refrigeration equipment
to be able to use a non-ozone depleting refrigerant in place
of a →chlorofluorocarbon (CFC).
Saturated Vapour Pressure
The maximum vapour pressure of a substance at a given temperature
when accumulated over its liquid or solid state in a
confined space.
Scenario (Generic)
A plausible and often simplified description of how the future
may develop, based on a coherent and internally consistent
set of driving forces and key relationships. Scenarios may be
derived from →projections, but are often based on additional
information from other sources, sometimes combined with a
‘narrative storyline’. See also: →SRES scenarios, →climate
scenario and →emission scenarios.
Semi-Aqueous Cleaning
Cleaning with a non-water-based cleaner, followed by a water
rinse.
Servicing (Refrigeration)
In the refrigeration sector, all kinds of work that may be performed
by a service technician, from installation, operations,
inspection, repair, retrofitting, redesign and decommissioning
of refrigeration systems to handling, storage, recovery and recycling
of refrigerants, as well as record-keeping.
Shortwave Radiation
See: →Solar radiation.
Smog
The buildup of high levels of pollution, generally in association
with urban areas. Photochemical smog occurs in the →troposphere
where sunlight causes chemical reactions in polluted air,
one effect of which is the generation of →ozone.
Solar Radiation
Radiation emitted by the Sun, most of which is shortwave radiation
at wavelengths less than about 1 μm and is determined
by the temperature of the Sun. See also: →Ultraviolet radiation;
compare with: →thermal infrared radiation.
Solvent
Any product (aqueous or organic) designed to clean a component
or assembly by dissolving the contaminants present on its
surface.
Specific Costs (of Abatement Options)
The difference in costs of an abatement option as compared
with a reference case, expressed in relevant specific units. In
this Report the specific costs of →greenhouse gas emission reduction
options are generally expressed in US$ per tonne of
avoided →CO2-equivalents (US$/tCO2-eq).
SRES Scenarios
→Emission scenarios developed by the IPCC Special Report
on Emission Scenarios (2000).
Stratosphere
The highly stratified region of the →atmosphere above the →
troposphere. It extends from an altitude of about 8 km in high
latitudes and 16 km in the tropics to an altitude of about 50
km. This region is characterized by increasing temperature with
altitude.
Stratospheric Polar Vortex
See: →Polar vortex
Surfactant
A product designed to reduce the surface tension of water. Also
referred to as a tension-active agent/tenside. Detergents are
made up principally from surfactants.
Technology and Economic Assessment Panel (TEAP)
A standing subsidiary body of the Parties to the →Montreal
Protocol, which was established in 1988 under Article 6 of the
Montreal Protocol and is coordinated by the →United Nations
Environment Programme (UNEP) Ozone Secretariat. It comprises
hundreds of experts from around the world. TEAP is responsible
for conducting assessments and for reporting to the
Parties on (a) the state of art of production and use technology,
options to →phase-out the use of →ozone-depleting substances
(ODSs), recycling, reuse and destruction techniques; and (b)
Annex II: Glossary 459
the economic effects of ozone layer modification and the economic
aspects of technology.
Thermal Infrared Radiation
Radiation emitted by the Earth’s surface, the →atmosphere and
the clouds, with wavelengths longer than the wavelength of the
red colour in the visible part of the spectrum. It is also known
as terrestrial or longwave radiation. The spectrum of infrared
radiation is distinct from that of →solar or shortwave radiation
because of the large difference in temperature between the surface
of the Sun and the Earth.
Thermoplastic
A material that can repeatedly become plastic on heating and
harden on cooling. Compare with: →Thermosetting.
Thermosetting
A material that sets permanently on heating. Compare with: →
Thermoplastic.
Threshold Limit Values (TLVs)
Exposure safety guidelines established by the American
Conference of Governmental and Industrial Hygienists
(ACGIH) based on an inhalation →time-weighted average.
TLVs ‘represent conditions under which it is believed that nearly
all workers can be repeatedly exposed day after day without
adverse effects.’ For volatile substances, such as →refrigerants,
TLVs are expressed as parts per million volume concentrations
in air (ppm).
Time-Weighted Average (TWA)
A technique used to measure the average exposure of workers
to a chemical over a given period of time.
Top-Down Models
A modelling approach that evaluates a system from aggregate
variables. An example of a top-down model is that of applied
macroeconomic theory and econometric techniques applied to
historical data on consumption, prices, incomes and factor costs
to model final demand for goods and services, and supply from
main sectors, like the energy sector, transportation, agriculture
and industry. Compare with: →Bottom-up models.
Total Equivalent Warming Impact (TEWI)
A measure of the overall global-warming impact of equipment
based on the total related →emissions of →greenhouse gases
during the operation of the equipment and the disposal of the
operating fluids at the end-of-life. TEWI takes into account
both direct fugitive emissions, and indirect emissions produced
through the energy consumed in operating the equipment. TEWI
is measured in units of mass of →CO2 equivalent. See also: →
Life cycle climate performance (LCCP).
Transitional Substance (Montreal Protocol)
Under the →Montreal Protocol, a chemical whose use is permitted
as a replacement for →ozone-depleting substances (ODSs),
but only temporarily because the substance’s →ozone depletion
potential (ODP) is non-zero.
Tropopause
The boundary between the →troposphere and the →stratosphere.
Troposphere
The lowest part of the →atmosphere above the Earth’s surface,
where clouds and ‘weather’ phenomena occur. The thickness
of the troposphere is on average 9 km in high latitudes, 10 km
in mid-latitudes, and 16 km in the tropics. Temperatures in the
troposphere generally decrease with height.
Ultraviolet Radiation (UV)
Radiation from the Sun with wavelengths between visible light
and X-rays. UV-B (280–320 nm), one of three bands of UV
radiation, is harmful to life on the Earth’s surface and is mostly
absorbed by the →ozone layer.
United Nations Environment Programme (UNEP)
Established in 1972, UNEP is the specialized agency of the
United Nations for environmental protection.
United Nations Framework Convention on Climate
Change (UNFCCC)
An international convention whose ultimate objective is the
‘stabilization of →greenhouse-gas concentrations in the atmosphere
at a level that would prevent dangerous →anthropogenic
interface with the →climate system’. The Convention was
adopted on 9 May 1992 in New York and signed at the 1992
Earth Summit in Rio de Janeiro by more than 150 countries and
the European Community. It contains commitments for all →
Parties and entered into force in March 1994. See also: →Kyoto
Protocol.
Venting (Refrigeration)
A service practice where the →refrigerant vapour is allowed
to escape into the →atmosphere after the refrigerant liquid has
been recovered.
Volatile Organic Compounds (VOCs)
Organic compounds that evaporate at their temperature of use.
Many VOCs contribute to the formation of →tropospheric →
ozone and →smog.
Voluntary Agreement
An agreement between a government authority and one or
more private parties, as well as a unilateral commitment that
is recognized by the public authority, to achieve environmental
objectives or to improve environmental performance beyond
compliance.
Voluntary Measures
Measures to reduce →greenhouse-gas emissions that are adopted
by firms or other actors in the absence of government man-
460 IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System
dates. Voluntary measures help make climate-friendly products
or processes more readily available or encourage consumers to
incorporate environmental values in their market choices.
Well-Mixed Greenhouse Gases
→Greenhouse gases with lifetimes that are long compared with
the mixing time between the two hemispheres (about 1 year),
so that their mixing ratios do not have large gradients except,
possibly, close to source regions.
World Meteorological Organization (WMO)
Established in 1950, WMO is the specialized agency of the
United Nations for meteorology (weather and climate), operational
hydrology and related geophysical sciences.
Zeotrope (Refrigeration)
A blend consisting of several →refrigerants of different volatilities
that appreciably changes in composition or temperature
as it evaporates (boils) or condenses (liquefies) at a given pressure.
A refrigerant blend assigned an R-400 series number designation
in ANSI/ASHRAE 34 is a zeotrope. Compare with: →
AzeotropePalaeoclimate
Coordinating Lead Authors:
Eystein Jansen (Norway), Jonathan Overpeck (USA)

This chapter should be cited as:
Jansen, E., J. Overpeck, K.R. Briffa, J.-C. Duplessy, F. Joos, V. Masson-Delmotte, D. Olago, B. Otto-Bliesner, W.R. Peltier, S. Rahmstorf, R. Ramesh, D. Raynaud, D. Rind, O. Solomina, R. Villalba and D. Zhang, 2007: Palaeoclimate. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
6
Supplementary Materials
SM.6-
Palaeoclimate Supplementary Material: Chapter 6
Appendix 6.A:
Glossary of Terms Specific to Chapter 6
Alkenones
Complex organic molecules found in fossil shells of plant plankton and used to reconstruct past sea surface temperatures.
Allerød
An abrupt warming event around 13,000 years ago seen in Greenland and elsewhere. See also the Bølling event; the two are often referred to together as the Bølling-Allerød Period: 14,500-12,900 years ago, characterized by warmer conditions in many places and for much of the time.
Bølling
An abrupt warming event around 14,500 years ago. See also the Allerød event.
Calendar-based time
Age determination in actual years, distinguished from 14C based time
Carbonate compensation depth
The level in the oceans at which the rate of supply of calcium carbonate (calcite and aragonite) equals the rate of dissolution, such that no calcium carbonate is preserved.
Diatom
Silt-sized algae that live in surface waters of lakes, rivers, and oceans and form shells of opal. Their species distribution in ocean cores is often related to past sea surface temperatures.
Eocene
The Eocene epoch (55-34 million years ago) is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era.
Foraminifera (planktonic)
Sand-sized organisms (protozoans) that live in ocean surface waters and form shells made out of CaCO3. Their species distribution in ocean cores is often used as an indication of sea surface temperatures in past climates.
Heinrich event
An interval of rapid flow of icebergs from the margins of ice sheets into the North Atlantic characterized by deposition of sediment eroded from the land.
Holocene
The latter of two Quaternary epochs, extending from about 11,600 years ago to and including the present.
Holocene Climate Optimum
The Holocene Climate Optimum is vague term used to denote a warm period during roughly the interval 9,000 to 5,000 years ago. This event has also been known by many other names, including: Hypisthermal, Altithermal, Climatic Optimum, Holocene Optimum, Holocene Thermal Maximum, and Holocene Megathermal. In reality the warming was primarily during Northern Hemisphere summer, and was not synchronous across the hemisphere.
Holocene Thermal Optimum (HTO)
See Holocene Climatic Optimum
Ice Age
An ice age or glacial period is characterized by a long-term reduction in the temperature of Earth’s climate, resulting in growth of continental ice sheets and mountain glaciers (“glaciation”).
Lake Agassiz
Once the largest proglacial lake in North America. Evidence of glacial Lake Agassiz occurs over an area of roughly 365,000 square miles, an area five times the size of the state of North Dakota, although at no single time did the lake ever cover this entire area. Ice margin positions and lowering of outlets by erosion combined to limit the size of the lake at any given time. Glacial Lake Agassiz was the latest in a series of proglacial lakes that must have formed in the Red River Valley many times during the Ice Age, each time north-draining rivers were impounded by ice sheets spreading south out of Canada and again as the glaciers receded.
Laurentide ice sheet
The largest of the Northern Hemisphere ice sheets that grow and shrink at orbital cycles, covering east-central Canada and the northern United States east of the Rockies.
Megadrought
Long-drawn out and pervasive drought much longer than normal, usually lasting a decade or more.
O-isotopes [oxygen isotope ratio]
Isotopes of Oxygen occur with molecular weights of 16, 17 and 18, of which 16 is the most abundant, and 18 the next. Their fractionation during phase changes is dependent on temperature, and so the ratio of oxygen-18 to oxygen-16 in forams, coral skeletons, ice layers of ice sheets, and other types of paleoclimatic samples can be related to temperature.
Ocean plankton
Organisms that live in the upper layers of oceans.

Paleocene
The Paleocene epoch (65-55 million years ago) is the first geologic epoch of the Palaeogene period in the modern Cenozoic era.
Paleocene-Eocene Thermal Maximum (PETM)
Beginning at the end of the Paleocene the PETM (55.5 to 54.8 million years before present), was one of the most rapid and extreme global warming events recorded in geologic history.
Paleosols
A soil horizon that formed on the surface during the geologic past, that is, an ancient soil. Also know as a buried soil; fossil soil.
Pliocene
The Pliocene epoch is the period in the geologic timescale that extends from 5.3 million to 1.8 million years before present.
Radiometric dating
A technique used to determine the absolute age of materials, such as organic materials or rocks, from the decay rates of naturally occurring radioactive isotopes. Examples are the decay of 14C with a half-life of about 5700 years, or the decay of 231Pa with a half-life of 32,000 years.
Sr/Ca ratios
The ratio between strontium and calcium in biologically-precipitated CaCO3 that has been successfully used as a temperature proxy (e.g., in corals and sclerosponges) to reconstruct past ocean temperature variations.
231Pa/230Th
As part of the uranium radioactive decay, Protactinium-231 decays to Thorium-230 with a half-life of 32,000 yrs; used for longer-term dating.
Annex I

Activities Implemented Jointly (AIJ)
The pilot phase for Joint Implementation, as defined in Article
.2(a) of the UNFCCC, which allows for project activity among
developed countries (and their companies) and between developed
and developing countries (and their companies). AIJ is intended
to allow parties to the UNFCCC to gain experience in jointly
implemented projects. AIJ under the pilot phase do not lead to any
credits. Decisions remain about the future of AIJ projects and how
they may relate to the Kyoto Mechanisms. As a simple form of
tradable permits, AIJ and other market-based schemes represent
potential mechanisms for stimulating additional resource flows for
reducing emissions. See also Clean Development Mechanism, and
Emissions Trading.
Actual net greenhouse gas removals by sinks
The sum of the verifiable changes in carbon stocks in the carbon
pools within the project boundary of an afforestation or reforestation
project, minus the increase in GHG emissions as a result of the
implementation of the project activity. The term stems from the Clean
Development Mechanism (CDM) afforestation and reforestation
modalities and procedures.
Adaptation
Initiatives and measures to reduce the vulnerability of natural and
human systems against actual or expected climate change effects.
Various types of adaptation exist, e.g. anticipatory and reactive,
private and public, and autonomous and planned. Examples are
raising river or coastal dikes, the substitution of more temperatureshock
resistant plants for sensitive ones, etc.
Adaptive capacity
The whole of capabilities, resources and institutions of a country or
region to implement effective adaptation measures.
Additionality
Reduction in emissions by sources or enhancement of removals by
sinks that is additional to any that would occur in the absence of
a Joint Implementation (JI) or a Clean Development Mechanism
(CDM) project activity as defined in the Kyoto Protocol Articles on
JI and CDM. This definition may be further broadened to include
financial, investment, technology, and environmental additionality.
Under financial additionality, the project activity funding is
additional to existing Global Environmental Facility, other financial
commitments of parties included in Annex I, Official Development
Assistance, and other systems of cooperation. Under investment
additionality, the value of the Emissions Reduction Unit/Certified
Emission Reduction Unit shall significantly improve the financial
or commercial viability of the project activity. Under technology
additionality, the technology used for the project activity shall
be the best available for the circumstances of the host party.
Environmental additionality refers to the environmental integrity
of the claimed amount by which greenhouse gas emissions are
reduced due to a project relative to its baseline. A project activity
is further additional, if the incentive from the sale of emission
allowances helps to overcome barriers to its implementation.
Aerosols
A collection of airborne solid or liquid particles, typically between
.01 and 10 μm in size and residing in the atmosphere for at least
several hours. Aerosols may be of either natural or anthropogenic
origin. Aerosols may influence climate in several ways: directly
through scattering and absorbing radiation, and indirectly through
acting as condensation nuclei for cloud formation or modifying the
optical properties and lifetime of clouds.
Afforestation
Direct human-induced conversion of land that has not been forested
for a period of at least 50 years to forested land through planting,
seeding and/or the human-induced promotion of natural seed
sources . See also Re- and Deforestation.
Agreement
In this Report, the degree of agreement is the relative level of
convergence of the literature as assessed by the authors.
Alliance of Small Island States (AOSIS)
Formed at the Second World Climate Conference (1990). AOSIS
comprises small-island and low-lying coastal developing countries
that are particularly vulnerable to the adverse consequences of
climate change, such as sea-level rise, coral bleaching, and the
increased frequency and intensity of tropical storms. With more than
states from the Atlantic, Caribbean, Indian Ocean, Mediterranean,
and Pacific, AOSIS share common objectives on environmental and
sustainable development matters in the UNFCCC process.
Ancillary benefits
Policies aimed at some target, e.g. climate change mitigation, may
be paired with positive side effects, such as increased resource-use
efficiency, reduced emissions of air pollutants associated with fossil
fuel use, improved transportation, agriculture, land-use practices,
employment, and fuel security. Ancillary impacts is also used
when the effects may be negative. Policies directed at abating air
pollution may consider greenhouse-gas mitigation an ancillary
benefit, but this perspective is not considered in this assessment.
See also co-benefits.
Annex I countries
The group of countries included in Annex I (as amended in 1998)
to the UNFCCC, including all the OECD countries and economies
in transition. Under Articles 4.2 (a) and 4.2 (b) of the Convention,
Annex I countries committed themselves specifically to the aim of
returning individually or jointly to their 1990 levels of greenhousegas
emissions by the year 2000. By default, the other countries are
referred to as Non-Annex I countries.
For a discussion of the term forest and related terms such as afforestation,
reforestation, and deforestation (ARD), see the IPCC Special Report on Land
Use, Land-Use Change and Forestry, Cambridge University Press, 2000.
Editor: Aviel Verbruggen (Belgium)
Notes:  entries (highlighted in bold) are by preference subjects; a main entry can contain subentries, also in bold,
e.g. Final Energy is defined under the entry Energy. Some definitions are adapted from Cleveland C.J. and C. Morris, 2006:
Dictionary of Energy, Elsevier, Amsterdam. The  is followed by a list of Acronyms/Abbreviations and by a list of Chemical
Compounds (Annex II).


Annex II countries
The group of countries included in Annex II to the UNFCCC,
including all OECD countries. Under Article 4.2 (g) of the
Convention, these countries are expected to provide financial
resources to assist developing countries to comply with their
obligations, such as preparing national reports. Annex II countries
are also expected to promote the transfer of environmentally sound
technologies to developing countries.
Annex B countries
The countries included in Annex B to the Kyoto Protocol that have
agreed to a target for their greenhouse-gas emissions, including all
the Annex I countries (as amended in 1998) except for Turkey and
Belarus.
Anthropogenic emissions
Emissions of greenhouse gases, greenhouse-gas precursors, and
aerosols associated with human activities. These include the
burning of fossil fuels, deforestation, land-use changes, livestock,
fertilization, etc. that result in a net increase in emissions.
Assigned Amount (AA)
Under the Kyoto Protocol, the assigned amount is the quantity of
greenhouse-gas emissions that an Annex B country has agreed to
as its ceiling for its emissions in the first commitment period (2008
to 2012). The AA is the country’s total greenhouse-gas emissions
in 1990 multiplied by five (for the five-year commitment period)
and by the percentage it agreed to as listed in Annex B of the Kyoto
Protocol (e.g. 92% for the EU; 93% for the USA).
Assigned Amount Unit (AAU)
An AAU equals 1 tonne (metric ton) of CO2-equivalent emissions
calculated using the Global Warming Potential.
Backstop technology
Models estimating mitigation often characterize an arbitrary carbonfree
technology (often for power generation) that becomes available
in the future in unlimited supply over the horizon of the model. This
allows models to explore the consequences and importance of a
generic solution technology without becoming enmeshed in picking
the technology. This “backstop” technology might be a nuclear
technology, fossil technology with capture and sequestration,
solar, or something as yet unimagined. The backstop technology is
typically assumed either not to currently exist, or to exist only at
higher costs relative to conventional alternatives.
Banking
According to the Kyoto Protocol [Article 3 (13)], parties included
in Annex I to the UNFCCC may save excess AAUs from the first
commitment period for compliance with their respective cap in
subsequent commitment periods (post-2012).
Barrier
Any obstacle to reaching a goal, adaptation or mitigation potential
that can be overcome or attenuated by a policy, programme, or
measure. Barrier removal includes correcting market failures
directly or reducing the transactions costs in the public and private
sectors by e.g. improving institutional capacity, reducing risk
and uncertainty, facilitating market transactions, and enforcing
regulatory policies.
Baseline
The reference for measurable quantities from which an alternative
outcome can be measured, e.g. a non-intervention scenario is used
as a reference in the analysis of intervention scenarios.
Benchmark
A measurable variable used as a baseline or reference in evaluating
the performance of an organization. Benchmarks may he drawn
from internal experience, that of other organizations or from legal
requirement and are often used to gauge changes in performance
over time.
Benefit transfer
An application of monetary values from one particular analysis to
another policy-decision setting, often in a geographic area other
than the one in which the original study was performed.
Biochemical Oxygen Demand (BOD)
The amount of dissolved oxygen consumed by micro-organisms
(bacteria) in the bio-chemical oxidation of organic and inorganic
matter in waste water.
Biocovers
Layers placed on top of landfills that are biologically active in
oxidizing methane into CO2.
Biofilters
Filters using biological material to filter or chemically process
pollutants like oxidizing methane into CO2.
Biodiversity
The variability among living organisms from all sources including,
inter alia, terrestrial, marine and other aquatic ecosystems and the
ecological complexes of which they are part; this includes diversity
within species, between species and of ecosystems.
Bioenergy
Energy derived from biomass.
Biofuel
Any liquid, gaseous, or solid fuel produced from plant or animal
organic matter. E.g. soybean oil, alcohol from fermented sugar,
black liquor from the paper manufacturing process, wood as fuel,
etc. Second-generation biofuels are products such as ethanol and
biodiesel derived from ligno-cellulosic biomass by chemical or
biological processes.
Biological options
Biological options for mitigation of climate change involve one or
more of the three strategies: conservation - conserving an existing
carbon pool, thereby preventing CO2 emissions to the atmosphere;
sequestration - increasing the size of existing carbon pools, thereby
extracting CO2 from the atmosphere; substitution - substituting
biomass for fossil fuels or energy-intensive products, thereby
reducing CO2 emissions.
Biomass
The total mass of living organisms in a given area or of a given
species usually expressed as dry weight. Organic matter consisting
of, or recently derived from, living organisms (especially regarded
as fuel) excluding peat. Biomass includes products, by-products and
waste derived from such material. Cellulosic biomass is biomass
from cellulose, the primary structural component of plants and
trees
Black Carbon
Particle matter in the atmosphere that consists of soot, charcoal
and/or possible light-absorbing refractory organic material. Black
carbon is operationally defined matter based on measurement of
light absorption and chemical reactivity and/or thermal stability.
Bottom-up models
Models represent reality by aggregating characteristics of specific
activities and processes, considering technological, engineering and
cost details. See also top-down models.


Bubble
Policy instrument for pollution abatement named for its treatment of
multiple emission points as if they were contained in an imaginary
bubble. Article 4 of the Kyoto Protocol allows a group of countries
to meet their target listed in Annex B jointly by aggregating their
total emissions under one ‘bubble’ and sharing the burden (e.g. the
EU).
Carbon Capture and Storage (CCS)
A process consisting of separation of CO2 from industrial and
energy-related sources, transport to a storage location, and longterm
isolation from the atmosphere.
Carbon cycle
The set of processes such as photosynthesis, respiration,
decomposition, and air-sea exchange, by which carbon continuously
cycles through various reservoirs, such as the atmosphere, living
organisms, soils, and oceans.
Carbon dioxide (CO2)
CO2 is a naturally occurring gas, and a by-product of burning fossil
fuels or biomass, of land-use changes and of industrial processes.
It is the principal anthropogenic greenhouse gas that affects
Earth’s radiative balance. It is the reference gas against which
other greenhouse gases are measured and therefore it has a Global
Warming Potential of 1.
Carbon dioxide fertilization
The enhancement of the growth of plants because of increased
atmospheric CO2 concentration. Depending on their mechanism of
photosynthesis, certain types of plants are more sensitive to changes
in atmospheric CO2 concentration than others.
Carbon intensity
The amount of emissions of CO2 per unit of GDP.
Carbon leakage
The part of emissions reductions in Annex B countries that may
be offset by an increase of the emissions in the non-constrained
countries above their baseline levels. This can occur through (1)
relocation of energy-intensive production in non-constrained
regions; (2) increased consumption of fossil fuels in these regions
through decline in the international price of oil and gas triggered
by lower demand for these energies; and (3) changes in incomes
(thus in energy demand) because of better terms of trade. Leakage
also refers to GHG-related effects of GHG-emission reduction or
CO2-sequestration project activities that occur outside the project
boundaries and that are measurable and attributable to the activity.
On most occasions, leakage is understood as counteracting the
initial activity. Nevertheless, there may be situations where effects
attributable to the activity outside the project area lead to GHGemission
reductions. These are commonly called spill-over. While
(negative) leakage leads to a discount of emission reductions as
verified, positive spill-over may not in all cases be accounted for.
Carbon pool
Carbon pools are: above-ground biomass, belowground biomass,
litter, dead wood and soil organic carbon. CDM project participants
may choose not to account one or more carbon pools if they provide
transparent and verifiable information showing that the choice will
not increase the expected net anthropogenic GHG removals by
sinks.
Carbon price
What has to be paid (to some public authority as a tax rate, or on
some emission permit exchange) for the emission of 1 tonne of CO2
into the atmosphere. In the models and this Report, the carbon price
is the social cost of avoiding an additional unit of CO2 equivalent
emission. In some models it is represented by the shadow price of
an additional unit of CO2 emitted, in others by the rate of carbon tax,
or the price of emission-permit allowances. It has also been used
in this Report as a cut-off rate for marginal abatement costs in the
assessment of economic mitigation potentials.
Cap
Mandated restraint as an upper limit on emissions. The Kyoto
Protocol mandates emissions caps in a scheduled timeframe on the
anthropogenic GHG emissions released by Annex B countries. By
-2012 the EU e.g. must reduce its CO2-equivalent emissions of
six greenhouse gases to a level 8% lower than the 1990-level.
Capacity building
In the context of climate change, capacity building is developing
technical skills and institutional capabilities in developing countries
and economies in transition to enable their participation in all aspects
of adaptation to, mitigation of, and research on climate change, and
in the implementation of the Kyoto Mechanisms, etc.
CCS-ready
If rapid deployment of CCS is desired, new power plants could be
designed and located to be ‘CCS-ready’ by reserving space for the
capture installation, designing the unit for optimal performance
when capture is added and siting the plant to enable access to
storage reservoirs.
Certified Emission Reduction Unit (CER)
Equal to one metric tonne of CO2-equivalent emissions reduced
or sequestered through a Clean Development Mechanism project,
calculated using Global Warming Potentials. In order to reflect
potential non-permanence of afforestation and reforestation project
activities, the use of temporary certificates for Net Anthropogenic
Greenhouse Gas Removal was decided by COP 9. See also
Emissions Reduction Units.
Chemical oxygen demand (COD)
The quantity of oxygen required for the complete oxidation of
organic chemical compounds in water; used as a measure of the
level of organic pollutants in natural and waste waters.
Chlorofluorocarbons (CFCs)
Greenhouse gases covered under the 1987 Montreal Protocol and used
for refrigeration, air conditioning, packaging, insulation, solvents,
or aerosol propellants. Because they are not destroyed in the lower
atmosphere, CFCs drift into the upper atmosphere where, given
suitable conditions, they break down ozone. These gases are being
replaced by other compounds, including hydrochlorofluorocarbons
and hydrofluorocarbons, which are greenhouse gases covered under
the Kyoto Protocol.
Clean Development Mechanism (CDM)
Defined in Article 12 of the Kyoto Protocol, the CDM is intended
to meet two objectives: (1) to assist parties not included in Annex
I in achieving sustainable development and in contributing to
the ultimate objective of the convention; and (2) to assist parties
included in Annex I in achieving compliance with their quantified
emission limitation and reduction commitments. Certified Emission
Reduction Units from CDM projects undertaken in Non-Annex
I countries that limit or reduce GHG emissions, when certified
by operational entities designated by Conference of the Parties/
Meeting of the Parties, can be accrued to the investor (government
or industry) from parties in Annex B. A share of the proceeds from
certified project activities is used to cover administrative expenses
as well as to assist developing country parties that are particularly
vulnerable to the adverse effects of climate change to meet the costs
of adaptation.


Climate Change (CC)
Climate change refers to a change in the state of the climate that can
be identified (e.g. using statistical tests) by changes in the mean and/
or the variability of its properties, and that persists for an extended
period, typically decades or longer. Climate change may be due
to natural internal processes or external forcings, or to persistent
anthropogenic changes in the composition of the atmosphere or in
land use.
Note that UNFCCC, in its Article 1, defines “climate change” as “a
change of climate which is attributed directly or indirectly to human
activity that alters the composition of the global atmosphere and
which is in addition to natural climate variability observed over
comparable time periods”. The UNFCCC thus makes a distinction
between “climate change” attributable to human activities altering
the atmospheric composition, and “climate variability” attributable
to natural causes.
Climate feedback
An interaction mechanism between processes in the climate system
is a climate feedback when the result of an initial process triggers
changes in secondary processes that in turn influence the initial
one. A positive feedback intensifies the initial process; a negative
feedback reduces the initial process. Example of a positive climate
feedback: higher temperatures as initial process cause melting of
the arctic ice leading to less reflection of solar radiation, what leads
to higher temperatures. Example of a negative feedback: higher
temperatures increase the amount of cloud cover (thickness or
extent) that could reduce incoming solar radiation and so limit the
increase in temperature.
Climate sensitivity
In IPCC Reports, equilibrium climate sensitivity refers to the
equilibrium change in annual mean global surface temperature
following a doubling of the atmospheric CO2-equivalent
concentration. The evaluation of the equilibrium climate sensitivity
is expensive and often hampered by computational constraints.
The effective climate sensitivity is a related measure that
circumvents the computational problem by avoiding the requirement
of equilibrium. It is evaluated from model output for evolving
non-equilibrium conditions. It is a measure of the strengths of the
feedbacks at a particular time and may vary with forcing history
and climate state. The climate sensitivity parameter refers to the
equilibrium change in the annual mean global surface temperature
following a unit change in radiative forcing (K/W/m2)
The transient climate response is the change in the global surface
temperature, averaged over a 20-year period, centred at the time
of CO2 doubling, i.e., at year 70 in a 1% per year compound CO2
increase experiment with a global coupled climate model. It is a
measure of the strength and rapidity of the surface temperature
response to greenhouse gas forcing.
Climate threshold
The point at which the atmospheric concentration of greenhouse
gases triggers a significant climatic or environmental event, which
is considered unalterable, such as widespread bleaching of corals or
a collapse of oceanic circulation systems.
CO2-equivalent concentration
The concentration of carbon dioxide that would cause the same
amount of radiative forcing as a given mixture of carbon dioxide
and other greenhouse gases.
CO2-equivalent emission
The amount of CO2 emission that would cause the same radiative
forcing as an emitted amount of a well mixed greenhouse gas, or a
mixture of well mixed greenhouse gases, all multiplied with their
respective Global Warming Potentials to take into account the
differing times they remain in the atmosphere.
Co-benefits
The benefits of policies implemented for various reasons at the
same time, acknowledging that most policies designed to address
greenhouse gas mitigation have other, often at least equally
important, rationales (e.g., related to objectives of development,
sustainability, and equity). The term co-impact is also used in a
more generic sense to cover both positive and negative side of the
benefits. See also ancillary benefits.
Co-generation
The use of waste heat from thermal electricity-generation plants.
The heat is e.g. condensing heat from steam turbines or hot flue
gases exhausted from gas turbines, for industrial use, buildings or
district heating. Synonym for Combined Heat and Power (CHP)
generation.
Combined-cycle Gas Turbine (CCGT)
Power plant that combines two processes for generating electricity.
First, gas or light fuel oil feeds a gas turbine that inevitably exhausts
hot flue gases (>800°C). Second, heat recovered from these gases,
with additional firing, is the source for producing steam that drives a
steam turbine. The turbines rotate separate alternators.
It becomes an integrated CCGT when the fuel is syngas from a
coal or biomass gasification reactor with exchange of energy flows
between the gasification and CCGT plants.
Compliance
Compliance is whether and to what extent countries do adhere to
the provisions of an accord. Compliance depends on implementing
policies ordered, and on whether measures follow up the policies.
Compliance is the degree to which the actors whose behaviour is
targeted by the agreement, local government units, corporations,
organizations or individuals, conform to the implementing
obligations. See also implementation.
Conference of the Parties (COP)
The supreme body of the UNFCCC, comprising countries with right
to vote that have ratified or acceded to the convention. The first
session of the Conference of the Parties (COP-1) was held in Berlin
(1995), followed by 2.Geneva (1996), 3.Kyoto (1997), 4.Buenos
Aires (1998), 5.Bonn (1999), 6.The Hague/Bonn (2000, 2001),
.Marrakech (2001), 8.Delhi (2002), 9.Milan (2003), 10.Buenos
Aires (2004), 11.Montreal (2005), 12.Nairobi (2006). See also
Meeting of the Parties (MOP).
Contingent Valuation Method (CVM)
CVM is an approach to quantitatively assess values assigned by people
in monetary (willingness to pay) and non monetary (willingness to
contribute with time, resources etc.) terms. It is a direct method to
estimate economic values for ecosystem and environmental services.
A survey of people are asked their willingness to pay for access
to, or their willingness to accept compensation for removal of, a
specific environmental service, based on a hypothetical scenario and
description of the environmental service. See also values.
Cost
The consumption of resources such as labor time, capital, materials,
fuels and so on as the consequence of an action. In economics all
resources are valued at their opportunity cost, being the value of
the most valuable alternative use of the resources. Costs are defined
in a variety of ways and under a variety of assumptions that affect
their value
Cost types include: administrative costs of planning, management,
monitoring, audits, accounting, reporting, clerical activities,
etc. associated with a project or programme; damage costs to
ecosystems, economies and people due to negative effects from
climate change; implementation costs of changing existing rules
and regulation, capacity building efforts, information, training and
education, etc. to put a policy into place; private costs are carried


by individuals, companies or other private entities that undertake the
action, where social costs include additionally the external costs on
the environment and on society as a whole.
Costs can be expressed as total, average (unit, specific) being the
total divided by the number of units of the item for which the cost
is being assessed, and marginal or incremental costs as the cost of
the last additional unit.
The perspectives adopted in this report are: Project level considers a
“standalone” activity that is assumed not to have significant indirect
economic impacts on markets and prices (both demand and supply)
beyond the activity itself. The activity can be the implementation of
specific technical facilities, infrastructure, demand-side regulations,
information efforts, technical standards, etc. Technology level
considers a specific greenhouse-gas mitigation technology, usually
with several applications in different projects and sectors. The
literature on technologies covers their technical characteristics,
especially evidence on learning curves as the technology diffuses
and matures. Sector level considers sector policies in a “partialequilibrium”
context, for which other sectors and the macroeconomic
variables are assumed to be as given. The policies can include
economic instruments related to prices, taxes, trade, and financing,
specific large-scale investment projects, and demand-side regulation
efforts. Macroeconomic level considers the impacts of policies on
real income and output, employment and economic welfare across
all sectors and markets. The policies include all sorts of economic
policies, such as taxes, subsidies, monetary policies, specific
investment programmes, and technology and innovation policies.
The negative of costs are benefits, and often both are considered
together.
Cost-benefit analysis
Monetary measurement of all negative and positive impacts
associated with a given action. Costs and benefits are compared in
terms of their difference and/or ratio as an indicator of how a given
investment or other policy effort pays off seen from the society’s
point of view.
Cost-effectiveness analysis
A special case of cost-benefit analysis in which all the costs of a
portfolio of projects are assessed in relation to a fixed policy goal.
The policy goal in this case represents the benefits of the projects
and all the other impacts are measured as costs or as negative costs
(co-benefits). The policy goal can be, for example, a specified goal
of emissions reductions of greenhouse gases.
Crediting period
The CDM crediting period is the time during which a project
activity is able to generate GHG-emission reduction or CO2 removal
certificates. Under certain conditions, the crediting period can be
renewed up to two times.
Deforestation
The natural or anthropogenic process that converts forest land to
non-forest. See afforestation and reforestation.
Demand-side management (DSM)
Policies and programmes for influencing the demand for goods and/
or services. In the energy sector, DSM aims at reducing the demand
for electricity and energy sources. DSM helps to reduce greenhouse
gas emissions.
Dematerialization
The process by which economic activity is decoupled from
matter–energy throughput, through processes such as eco-efficient
production or industrial ecology, allowing environmental impact to
fall per unit of economic activity.
Deposit-refund system
A deposit or fee (tax) is paid when acquiring a commodity and a
refund or rebate is received for implementation of a specified action
(mostly delivering the commodity at a particular place).
Desertification
This refers to land degradation in arid, semi-arid, and dry subhumid
areas resulting from various factors, including climatic
variations and human activities. The United Nations Convention to
Combat Desertification defines land degradation as a reduction or
loss, in arid, semi-arid, and dry sub-humid areas, of the biological
or economic productivity and complexity of rain-fed cropland,
irrigated cropland, or range, pasture, forest and woodlands
resulting from land uses or from a process or combination of
processes, including processes arising from human activities and
habitation patterns, such as soil erosion caused by wind and/or
water, deterioration of the physical, chemical and biological or
economic properties of soil and long-term loss of natural vegetation.
Devegetation
This is loss of vegetation density within one land-cover class.
Development path
An evolution based on an array of technological, economic, social,
institutional, cultural and biophysical characteristics that determine
the interactions between human and natural systems, including
production and consumption patterns in all countries, over time at a
particular scale. Alternative development paths refer to different
possible trajectories of development, the continuation of current
trends being just one of the many paths.
Discounting
A mathematical operation making monetary (or other) amounts
received or expended at different points in time (years) comparable
across time. The operator uses a fixed or possibly time-varying
discount rate (>0) from year to year that makes future value worth
less today. In a descriptive discounting approach one accepts the
discount rates people (savers and investors) actually apply in their
day-to-day decisions (private discount rate). In a prescriptive
(ethical or normative) discounting approach the discount rate is
fixed from a social perspective, e.g. based on an ethical judgement
about the interests of future generations (social discount rate).
District heating
Hot water (steam in old systems) is distributed from central stations
to buildings and industries in a densely occupied area (a district, a
city or an industrialized area such as the Ruhr or Saar in Germany).
The insulated two-pipe network functions like a water-based central
heating system in a building. The central heat sources can be wasteheat
recovery at industrial processes, waste-incineration plants,
cogeneration power plants or stand-alone boilers burning fossil
fuels or biomass.
Double dividend
The extent to which revenue-generating instruments, such as carbon
taxes or auctioned (tradable) carbon emission permits can (1) limit
or reduce GHG emissions and (2) offset at least part of the potential
welfare losses of climate policies through recycling the revenue in
the economy to reduce other taxes likely to cause distortions. In a
world with involuntary unemployment, the climate change policy
adopted may have an effect (a positive or negative ‘third dividend’)
on employment. Weak double dividend occurs as long as there is
a revenue-recycling effect. That is, revenues are recycled through
reductions in the marginal rates of distorting taxes. Strong double
dividend requires that the (beneficial) revenue-recycling effect more
than offsets the combination of the primary cost and in this case, the
net cost of abatement is negative. See also interaction effect.
Economies in Transition (EITs)
Countries with their economies changing from a planned economic
system to a market economy.


Economies of scale (scale economies)
The unit cost of an activity declines when the activity is extended
(e.g., more units are produced).
Ecosystem
A system of living organisms interacting with each other and their
physical environment. The boundaries of what could be called
an ecosystem are somewhat arbitrary, depending on the focus of
interest or study. Thus, the extent of an ecosystem may range from
very small spatial scales to the entire planet Earth ultimately.
Emissions Direct / Indirect
Direct emissions or “point of emission” are defined at the point
in the energy chain where they are released and are attributed to
that point in the energy chain, whether a sector, a technology or an
activity. E.g. emissions from coal-fired power plants are considered
direct emissions from the energy supply sector. Indirect emissions
or emissions “allocated to the end-use sector” refer to the energy
use in end-use sectors and account for the emissions associated
with the upstream production of the end-use energy. E.g. some
emissions associated with electricity generation can be attributed
to the buildings sector corresponding to the building sector’s use
of electricity.
Emission factor
An emission factor is the rate of emission per unit of activity, output
or input. E.g. a particular fossil fuel power plant has a CO2 emission
factor of 0.765 kg/kWh generated.
Emission permit
An emission permit is a non-transferable or tradable entitlement
allocated by a government to a legal entity (company or other
emitter) to emit a specified amount of a substance. A tradable
permit is an economic policy instrument under which rights to
discharge pollution - in this case an amount of greenhouse gas
emissions - can be exchanged through either a free or a controlled
permit-market.
Emission quota
The portion of total allowable emissions assigned to a country
or group of countries within a framework of maximum total
emissions.
Emissions Reduction Unit (ERU)
Equal to one metric tonne of CO2-equivalent emissions reduced or
sequestered arising from a Joint Implementation (defined in Article
of the Kyoto Protocol) project. See also Certified Emission
Reduction Unit and emissions trading.
Emission standard
A level of emission that by law or by voluntary agreement may not be
exceeded. Many standards use emission factors in their prescription
and therefore do not impose absolute limits on the emissions.
Emissions trading
A market-based approach to achieving environmental objectives.
It allows those reducing GHG emissions below their emission cap
to use or trade the excess reductions to offset emissions at another
source inside or outside the country. In general, trading can occur at
the intra-company, domestic, and international levels. The Second
Assessment Report by the IPCC adopted the convention of using
permits for domestic trading systems and quotas for international
trading systems. Emissions trading under Article 17 of the Kyoto
Protocol is a tradable quota system based on the assigned amounts
calculated from the emission reduction and limitation commitments
listed in Annex B of the Protocol.
Emission trajectories
These are projections of future emission pathways, or observed
emission patterns.
Energy
The amount of work or heat delivered. Energy is classified in a
variety of types and becomes useful to human ends when it flows
from one place to another or is converted from one type into another.
Primary energy (also referred to as energy sources) is the energy
embodied in natural resources (e.g., coal, crude oil, natural gas,
uranium) that has not undergone any anthropogenic conversion. It
is transformed into secondary energy by cleaning (natural gas),
refining (oil in oil products) or by conversion into electricity or heat.
When the secondary energy is delivered at the end-use facilities it
is called final energy (e.g., electricity at the wall outlet), where it
becomes usable energy (e.g., light). Daily, the sun supplies large
quantities of energy as rainfall, winds, radiation, etc. Some share
is stored in biomass or rivers that can be harvested by men. Some
share is directly usable such as daylight, ventilation or ambient heat.
Renewable energy is obtained from the continuing or repetitive
currents of energy occurring in the natural environment and includes
non-carbon technologies such as solar energy, hydropower, wind,
tide and waves and geothermal heat, as well as carbon-neutral
technologies such as biomass. Embodied energy is the energy used
to produce a material substance (such as processed metals or building
materials), taking into account energy used at the manufacturing
facility (zero order), energy used in producing the materials that are
used in the manufacturing facility (first order), and so on.
Energy efficiency
The ratio of useful energy output of a system, conversion process or
activity to its energy input.
Energy intensity
The ratio of energy use to economic output. At the national level,
energy intensity is the ratio of total domestic primary energy use
or final energy use to Gross Domestic Product. See also specific
energy use
Energy security
The various security measures that a given nation, or the global
community as a whole, must carry out to maintain an adequate
energy supply.
Energy Service Company (ESCO)
A company that offers energy services to end-users, guarantees the
energy savings to be achieved tying them directly to its remuneration,
as well as finances or assists in acquiring financing for the operation
of the energy system, and retains an on-going role in monitoring the
savings over the financing term.
Environmental effectiveness
The extent to which a measure, policy or instrument produces a
decided, decisive or desired environmental effect.
Environmentally sustainable technologies
Technologies that are less polluting, use resources in a more
sustainable manner, recycle more of their wastes and products,
and handle residual wastes in a more acceptable manner than the
technologies that they substitute. They are also more compatible with
nationally determined socio-economic, cultural and environmental
priorities.
Evidence
Information or signs indicating whether a belief or proposition is true
or valid. In this Report, the degree of evidence reflects the amount
of scientific/technical information on which the Lead Authors are
basing their findings.


Externality / External cost / External benefit
Externalities arise from a human activity, when agents responsible
for the activity do not take full account of the activity’s impact on
others’ production and consumption possibilities, while there exists
no compensation for such impact. When the impact is negative, so
are external costs. When positive they are referred to as external
benefits.
Feed-in tariff
The price per unit of electricity that a utility or power supplier has
to pay for distributed or renewable electricity fed into the grid by
non-utility generators. A public authority regulates the tariff.
Flaring
Open air burning of waste gases and volatile liquids, through a
chimney, at oil wells or rigs, in refineries or chemical plants and at
landfills.
Forecast
Projected outcome from established physical, technological,
economic, social, behavioral, etc. patterns.
Forest
Defined under the Kyoto Protocol as a minimum area of land of
.05-1.0 ha with tree-crown cover (or equivalent stocking level)
of more than 10-30 % with trees with the potential to reach a
minimum height of 2-5 m at maturity in situ. A forest may consist
either of closed forest formations where trees of various storey and
undergrowth cover a high proportion of the ground or of open forest.
Young natural stands and all plantations that have yet to reach a
crown density of 10-30 % or tree height of 2-5 m are included under
forest, as are areas normally forming part of the forest area that are
temporarily un-stocked as a result of human intervention such as
harvesting or natural causes but which are expected to revert to
forest. See also Afforestation, Deforestation and Reforestation.
Fossil fuels
Carbon-based fuels from fossil hydrocarbon deposits, including
coal, peat, oil and natural gas.
Free Rider
One who benefits from a common good without contributing to its
creation or preservation.
Fuel cell
A fuel cell generates electricity in a direct and continuous way from
the controlled electrochemical reaction of hydrogen or another fuel
and oxygen. With hydrogen as fuel it emits only water and heat (no
CO2) and the heat can be utilized (see cogeneration).
Fuel switching
In general, this is substituting fuel A for fuel B. In the climatechange
discussion it is implicit that fuel A has lower carbon content
than fuel B, e.g., natural gas for coal.
Full-cost pricing
Setting the final prices of goods and services to include both the
private costs of inputs and the external costs created by their
production and use.
G77/China. See Group of 77 and China.
General circulation (climate) model (GCM)
A numerical representation of the climate system based on the
physical, chemical and biological properties of its components, their
interactions and feedback processes, and accounting for all or some
of its known properties. The climate system can be represented
by models of varying complexity, i.e. for any one component or
combination of components a hierarchy of models can be identified,
differing in such aspects as the number of spatial dimensions, the
extent to which physical, chemical or biological processes are
explicitly represented, or the level at which the parameters are
assessed empirically. Coupled atmosphere/ocean/sea-ice General
Circulation Models provide a comprehensive representation of the
climate system. There is an evolution towards more complex models
with active chemistry and biology.
General equilibrium analysis
General equilibrium analysis considers simultaneously all the
markets and feedback effects among these markets in an economy
leading to market clearance. See also market equilibrium.
Geo-engineering
Technological efforts to stabilize the climate system by direct
intervention in the energy balance of the Earth for reducing global
warming
Global Environmental Facility (GEF)
The Global Environment Facility (GEF), established in 1991, helps
developing countries fund projects and programmes that protect
the global environment. GEF grants support projects related to
biodiversity, climate change, international waters, land degradation,
the ozone layer, and persistent organic pollutants
Global warming
Global warming refers to the gradual increase, observed or
projected, in global surface temperature, as one of the consequences
of radiative forcing caused by anthropogenic emissions.
Global Warming Potential (GWP)
An index, based upon radiative properties of well mixed greenhouse
gases, measuring the radiative forcing of a unit mass of a given
well mixed greenhouse gas in today’s atmosphere integrated over
a chosen time horizon, relative to that of CO2. The GWP represents
the combined effect of the differing lengths of time that these
gases remain in the atmosphere and their relative effectiveness in
absorbing outgoing infrared radiation. The Kyoto Protocol is based
on GWPs from pulse emissions over a 100-year time frame.
Green accounting
Attempts to integrate into macroeconomic studies a broader set of
social welfare measures, covering e.g., social, environmental, and
development oriented policy aspects. Green accounting includes
both monetary valuations that attempt to calculate a ‘green national
product’ with the economic damage by pollutants subtracted from the
national product, and accounting systems that include quantitative
non-monetary pollution, depletion and other data.
Greenhouse effect
Greenhouse gases effectively absorb infrared radiation, emitted
by the Earth’s surface, by the atmosphere itself due to the same
gases and by clouds. Atmospheric radiation is emitted to all sides,
including downward to the Earth’s surface. Thus, greenhouse gases
trap heat within the surface-troposphere system. This is called the
greenhouse effect.
Thermal infrared radiation in the troposphere is strongly coupled
to the temperature at the altitude at which it is emitted. In the
troposphere, the temperature generally decreases with height.
Effectively, infrared radiation emitted to space originates from an
altitude with a temperature of, on average, –19°C, in balance with
the net incoming solar radiation, whereas the Earth’s surface is kept
at a much higher temperature of, on average, +14°C.
An increase in the concentration of greenhouse gases leads to an
increased infrared opacity of the atmosphere and therefore to an
effective radiation into space from a higher altitude at a lower
temperature. This causes a radiative forcing that leads to an
enhancement of the greenhouse effect, the so-called enhanced
greenhouse effect.


Greenhouse gases (GHGs)
Greenhouse gases are those gaseous constituents of the atmosphere,
both natural and anthropogenic, that absorb and emit radiation at
specific wavelengths within the spectrum of infrared radiation
emitted by the Earth’s surface, the atmosphere and clouds. This
property causes the greenhouse effect. Water vapour (H2O), carbon
dioxide (CO2), nitrous oxide (N2O), methane (CH4) and ozone
(O3) are the primary greenhouse gases in the earth’s atmosphere.
Moreover, there are a number of entirely human-made greenhouse
gases in the atmosphere, such as the halocarbons and other chlorineand
bromine-containing substances, dealt with under the Montreal
Protocol. Besides carbon dioxide, nitrous oxide and methane, the
Kyoto Protocol deals with the greenhouse gases sulphur hexafluoride,
hydrofluorocarbons, and perfluorocarbons.
Gross Domestic Product (GDP)
The sum of gross value added, at purchasers’ prices, by all resident
and non-resident producers in the economy, plus any taxes and
minus any subsidies not included in the value of the products in
a country or a geographic region for a given period, normally one
year. It is calculated without deducting for depreciation of fabricated
assets or depletion and degradation of natural resources.
Gross National Product (GNP)
GNP is a measure of national income. It measures value added from
domestic and foreign sources claimed by residents. GNP comprises
Gross Domestic Product plus net receipts of primary income from
non-resident income.
Gross World Product
An aggregation of the individual country’s Gross Domestic Products
to obtain the sum for the world.
Group of 77 and China (G77/China)
Originally 77, now more than 130, developing countries that act
as a major negotiating bloc in the UNFCCC process. G77/China
is also referred to as Non-Annex I countries in the context of the
UNFCCC.
Governance
The way government is understood has changed in response to
social, economic and technological changes over recent decades.
There is a corresponding shift from government defined strictly
by the nation-state to a more inclusive concept of governance,
recognizing the contributions of various levels of government
(global, international, regional, local) and the roles of the private
sector, of non-governmental actors and of civil society.
Hot air
Under the terms of the 1997 Kyoto Protocol, national emission
targets in Annex B are expressed relative to emissions in the year
. For countries in the former Soviet Union and Eastern Europe
this target has proven to be higher than their current and projected
emissions for reasons unrelated to climate-change mitigation
activities. Russia and Ukraine, in particular, are expected to have
a substantial volume of excess emission allowances over the period
-2012 relative to their forecast emissions. These allowances
are sometimes referred to as hot air because, while they can be
traded under the Kyoto Protocol’s flexibility mechanisms, they did
not result from mitigation activities.
Hybrid vehicle
Any vehicle that employs two sources of propulsion, especially a
vehicle that combines an internal combustion engine with an electric
motor.
Hydrofluorocarbons (HFCs)
One of the six gases or groups of gases to be curbed under the
Kyoto Protocol. They are produced commercially as a substitute
for chlorofluorocarbons. HFCs are largely used in refrigeration and
semiconductor manufacturing. Their Global Warming Potentials
range from 1,300 to 11,700.
Implementation
Implementation describes the actions taken to meet commitments
under a treaty and encompasses legal and effective phases. Legal
implementation refers to legislation, regulations, judicial decrees,
including other actions such as efforts to administer progress, which
governments take to translate international accords into domestic
law and policy. Effective implementation needs policies and
programmes that induce changes in the behaviour and decisions
of target groups. Target groups then take effective measures of
mitigation and adaptation.
Income elasticity (of demand)
This is the ratio of the percentage change in quantity of demand for
a good or service to a one percentage change in income. For most
goods and services, demand goes up when income grows, making
income elasticity positive. When the elasticity is less than one,
goods and services are called necessities.
Industrial ecology
The relationship of a particular industry with its environment. It
often refers to the conscious planning of industrial processes to
minimize their negative externalities (e.g., by heat and materials
cascading).
Inertia
In the context of climate-change mitigation, inertia relates to the
difficulty of change resulting from pre-existing conditions within
society such as physical man-made capital, natural capital and social
non-physical capital, including institutions, regulations and norms.
Existing structures lock in societies, making change more difficult.
Integrated assessment
A method of analysis that combines results and models from
the physical, biological, economic and social sciences, and the
interactions between these components in a consistent framework to
evaluate the status and the consequences of environmental change
and the policy responses to it.
Integrated Design Process (IDP) of buildings
Optimizing the orientation and shape of buildings and providing
high-performance envelopes for minimizing heating and cooling
loads. Passive techniques for heat transfer control, ventilation and
daylight access reduce energy loads further. Properly sized and
controlled, efficient mechanical systems address the left-over loads.
IDP requires an iterative design process involving all the major
stakeholders from building users to equipment suppliers, and can
achieve 30-75% savings in energy use in new buildings at little or
no additional investment cost.
Intelligent controls
In this report, the notion of ‘intelligent control’ refers to the
application of information technology in buildings to control
heating, ventilation, air-conditioning, and electricity use effectively.
It requires effective monitoring of parameters such as temperature,
convection, moisture, etc., with appropriate control measurements
(‘smart metering’).
Interaction effect
The consequence of the interaction of climate-change policy
instruments with existing domestic tax systems, including both
cost-increasing tax interaction and cost-reducing revenue-recycling
effect. The former reflects the impact that greenhouse gas policies
can have on labour and capital markets through their effects on real
wages and the real return to capital. Restricting allowable GHG


emissions, raises the carbon price and so the costs of production
and the prices of output, thus reducing the real return to labour and
capital. With policies that raise revenue for the government, carbon
taxes and auctioned permits, the revenues can be recycled to reduce
existing distortional taxes. See also double dividend.
Intergovernmental Organization (IGO)
Organizations constituted of governments. Examples include the
World Bank, the Organization of Economic Co-operation and
Development (OECD), the International Civil Aviation Organization
(ICAO), the Intergovernmental Panel on Climate Change (IPCC),
and other UN and regional organizations. The Climate Convention
allows accreditation of these IGOs to attend negotiating sessions.
International Energy Agency (IEA)
Established in 1974, the agency is linked with the OECD. It enables
OECD member countries to take joint measures to meet oil supply
emergencies, to share energy information, to coordinate their
energy policies, and to cooperate in developing rational energy use
programmes.
Joint Implementation (JI)
A market-based implementation mechanism defined in Article 6 of
the Kyoto Protocol, allowing Annex I countries or companies from
these countries to implement projects jointly that limit or reduce
emissions or enhance sinks, and to share the Emissions Reduction
Units. JI activity is also permitted in Article 4.2(a) of the UNFCCC.
See also Activities Implemented Jointly and Kyoto Mechanisms.
Kyoto Mechanisms (also called Flexibility Mechanisms)
Economic mechanisms based on market principles that parties to the
Kyoto Protocol can use in an attempt to lessen the potential economic
impacts of greenhouse gas emission-reduction requirements. They
include Joint Implementation (Article 6), Clean Development
Mechanism (Article 12), and Emissions trading (Article 17).
Kyoto Protocol
The Kyoto Protocol to the UNFCCC was adopted at the Third
Session of the Conference of the Parties (COP) in 1997 in Kyoto. It
contains legally binding commitments, in addition to those included
in the FCCC. Annex B countries agreed to reduce their anthropogenic
GHG emissions (carbon dioxide, methane, nitrous oxide,
hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride) by
at least 5% below 1990 levels in the commitment period 2008-2012.
The Kyoto Protocol came into force on 16 February 2005.
Landfill
A landfill is a solid waste disposal site where waste is deposited
below, at or above ground level. Limited to engineered sites with
cover materials, controlled placement of waste and management of
liquids and gases. It excludes uncontrolled waste disposal.
Land-use
The total of arrangements, activities and inputs undertaken in a
certain land-cover type (a set of human actions). The social and
economic purposes for which land is managed (e.g., grazing, timber
extraction, and conservation). Land-use change occurs when, e.g.,
forest is converted to agricultural land or to urban areas.
Leapfrogging
The ability of developing countries to bypass intermediate
technologies and jump straight to advanced clean technologies.
Leapfrogging can enable developing countries to move to a lowemissions
development trajectory.
Learning by doing
As researchers and firms gain familiarity with a new technological
process, or acquire experience through expanded production they
can discover ways to improve processes and reduce cost. Learning
by doing is a type of experience-based technological change.
Levelized cost price
The unique price of the outputs of a project that makes the present
value of the revenues (benefits) equal to the present value of the
costs over the lifetime of the project. See also discounting and
present value.
Likelihood
The likelihood of an occurrence, outcome or result, where this can
be estimated probabilistically, is expressed in IPCC reports using a
standard terminology:
Particular, or a range
of, occurrences/outcomes
of an uncertain
event owning a
probability of
are said
>99% to be: Virtually certain
>90% Very likely
>66% Likely
to 66% About as likely as not
<33% Unlikely
<10% Very unlikely
<1% Exceptionally unlikely
Lock-in effect
Technologies that cover large market shares continue to be used
due to factors such as sunk investment costs, related infrastructure
development, use of complementary technologies and associated
social and institutional habits and structures.
Low-carbon technology
A technology that over its life cycle causes less CO2-eq. emissions
than other technological options do. See also Environmentally
sustainable technologies.
Macroeconomic costs
These costs are usually measured as changes in Gross Domestic
Product or changes in the growth of Gross Domestic Product, or as
loss of welfare or consumption.
Marginal cost pricing
The pricing of goods and services such that the price equals the
additional cost arising when production is expanded by one unit.
Economic theory shows that this way of pricing maximizes social
welfare in a first-best economy.
Market barriers
In the context of climate change mitigation, market barriers are
conditions that prevent or impede the diffusion of cost-effective
technologies or practices that would mitigate GHG emissions.
Market-based regulation
Regulatory approaches using price mechanisms (e.g., taxes and
auctioned tradable permits), among other instruments, to reduce
GHG emissions.
Market distortions and imperfections
In practice, markets will always exhibit distortions and imperfections
such as lack of information, distorted price signals, lack of
competition, and/or institutional failures related to regulation,
inadequate delineation of property rights, distortion-inducing fiscal
systems, and limited financial markets
Market equilibrium
The point at which the demand for goods and services equals the
supply; often described in terms of price levels, determined in a
competitive market, ‘clearing’ the market.
Market Exchange Rate (MER)
This is the rate at which foreign currencies are exchanged. Most
economies post such rates daily and they vary little across all the
exchanges. For some developing economies official rates and blackmarket
rates may differ significantly and the MER is difficult to pin
down.


Material efficiency options
In this report, options to reduce GHG emissions by decreasing the
volume of materials needed for a certain product or service
Measures
Measures are technologies, processes, and practices that reduce
GHG emissions or effects below anticipated future levels. Examples
of measures are renewable energy technologies, waste minimization
processes and public transport commuting practices, etc. See also
policies.
Methane (CH4)
Methane is one of the six greenhouse gases to be mitigated under
the Kyoto Protocol. It is the major component of natural gas and
associated with all hydrocarbon fuels, animal husbandry and
agriculture. Coal-bed methane is the gas found in coal seams.
Methane recovery
Methane emissions, e.g., from oil or gas wells, coal beds, peat bogs,
gas transmission pipelines, landfills, or anaerobic digesters, are
captured and used as a fuel or for some other economic purpose
(e.g., chemical feedstock).
Meeting of the Parties (to the Kyoto Protocol) (MOP)
The Conference of the Parties (COP) of the UNFCCC serves as
the Meeting of the Parties (MOP), the supreme body of the Kyoto
Protocol, since the latter entered into force on 16 February 2005.
Only parties to the Kyoto Protocol may participate in deliberations
and make decisions.
Millennium Development Goals (MDG)
A set of time-bound and measurable goals for combating poverty,
hunger, disease, illiteracy, discrimination against women and
environmental degradation, agreed at the UN Millennium Summit
in 2000.
Mitigation
Technological change and substitution that reduce resource inputs
and emissions per unit of output. Although several social, economic
and technological policies would produce an emission reduction,
with respect to climate change, mitigation means implementing
policies to reduce GHG emissions and enhance sinks.
Mitigative capacity
This is a country’s ability to reduce anthropogenic GHG emissions or
to enhance natural sinks, where ability refers to skills, competencies,
fitness and proficiencies that a country has attained and depends
on technology, institutions, wealth, equity, infrastructure and
information. Mitigative capacity is rooted in a country’s sustainable
development path.
Montreal Protocol
The Montreal Protocol on Substances that Deplete the Ozone Layer
was adopted in Montreal in 1987, and subsequently adjusted and
amended in London (1990), Copenhagen (1992), Vienna (1995),
Montreal (1997) and Beijing (1999). It controls the consumption
and production of chlorine- and bromine-containing chemicals that
destroy stratospheric ozone, such as chlorofluorocarbons, methyl
chloroform, carbon tetrachloride, and many others.
Multi-attribute analysis.
Integrates different decision parameters and values in a quantitative
analysis without assigning monetary values to all parameters.
Multi-attribute analysis can combine quantitative and qualitative
information.
Multi-gas
Next to CO2 also the other greenhouse gases (methane, nitrous
oxide and fluorinated gases) are taken into account in e.g. achieving
reduction of emissions (multi-gas reduction) or stabilization of
concentrations (multi-gas stabilization).
National Action Plans
Plans submitted to the COP by parties outlining the steps that
they have adopted to limit their anthropogenic GHG emissions.
Countries must submit these plans as a condition of participating in
the UNFCCC and, subsequently, must communicate their progress
to the COP regularly. The National Action Plans form part of the
National Communications, which include the national inventory of
GHG sources and sinks.
Net anthropogenic greenhouse gas removals by sinks
For CDM afforestation and reforestation projects, ‘net anthropogenic
GHG removals by sinks’ equals the actual net GHG removals
by sinks minus the baseline net GHG removals by sinks minus
leakage.
Nitrous oxide (N2O)
One of the six types of greenhouse gases to be curbed under the
Kyoto Protocol.
Non-Annex I Countries/Parties
The countries that have ratified or acceded to the UNFCCC but are
not included in Annex I.
Non-Annex B Countries/Parties
The countries not included in Annex B of the Kyoto Protocol.
No-regret policy (options / potential)
Such policy would generate net social benefits whether or not
there is climate change associated with anthropogenic emissions of
greenhouse gases. No-regret options for GHG emissions reduction
refer to options whose benefits (such as reduced energy costs and
reduced emissions of local/regional pollutants) equal or exceed their
costs to society, excluding the benefits of avoided climate change.
Normative analysis
Economic analysis in which judgments about the desirability of
various policies are made. The conclusions rest on value judgments
as well as on facts and theories.
Oil sands and oil shale
Unconsolidated porous sands, sandstone rock and shales containing
bituminous material that can be mined and converted to a liquid
fuel.
Opportunities
Circumstances to decrease the gap between the market potential of
any technology or practice and the economic potential or technical
potential.
Ozone (O3)
Ozone, the tri-atomic form of oxygen, is a gaseous atmospheric
constituent. In the troposphere, ozone is created both naturally
and by photochemical reactions involving gases resulting from
human activities. Troposphere ozone acts as a greenhouse gas. In
the stratosphere, ozone is created by the interaction between solar
ultraviolet radiation and molecular oxygen (O2). Stratospheric
ozone plays a dominant role in the stratospheric radiative balance.
Its concentration is highest in the ozone layer.
Pareto criterion
A criterion testing whether an individual’s welfare can be
increased without making others in the society worse off. A Pareto
improvement occurs when an individual’s welfare is improved
without making the welfare of the rest of society worse off. A


Pareto optimum is reached when no one’s welfare can be increased
without making the welfare of the rest of society worse off, given
a particular distribution of income. Different income distributions
lead to different Pareto optima.
Passive solar design
Structural design and construction techniques that enable a building
to utilize solar energy for heating, cooling, and lighting by nonmechanical
means.
Perfluorocarbons (PFCs)
Among the six greenhouse gases to be abated under the Kyoto
Protocol. These are by-products of aluminium smelting and
uranium enrichment. They also replace chlorofluorocarbons in
manufacturing semiconductors. The Global Warming Potential of
PFCs is 6500–9200.
Policies
In UNFCCC parlance, policies are taken and/or mandated by a
government - often in conjunction with business and industry within
its own country, or with other countries - to accelerate mitigation
and adaptation measures. Examples of policies are carbon or
other energy taxes, fuel efficiency standards for automobiles, etc.
Common and co-ordinated or harmonised policies refer to those
adopted jointly by parties. See also measures.
Portfolio analysis
Deals with a portfolio of assets or policies that are characterized
by different risks and pay-offs. The objective function is built up
around the variability of returns and their risks, leading up to the
decision rule to choose the portfolio with highest expected return.
Post-consumer waste
Waste from consumption activities, e.g. packaging materials, paper,
glass, rests from fruits and vegetables, etc.
Potential
In the context of climate change, potential is the amount of
mitigation or adaptation that could be - but is not yet – realized over
time. As potential levels are identified: market, economic, technical
and physical.
• Market potential indicates the amount of GHG mitigation that
might be expected to occur under forecast market conditions
including policies and measures in place at the time.. It is based
on private unit costs and discount rates, as they appear in the
base year and as they are expected to change in the absence of
any additional policies and measures.
• Economic potential is in most studies used as the amount of
GHG mitigation that is cost-effective for a given carbon price,
based on social cost pricing and discount rates, including
energy savings, but without most externalities. Theoretically,
it is defined as the potential for cost-effective GHG mitigation
when non-market social costs and benefits are included with
market costs and benefits in assessing the options for particular
levels of carbon prices (as affected by mitigation policies) and
when using social discount rates instead of private ones. This
includes externalities, i.e., non-market costs and benefits such
as environmental co-benefits
• Technical potential is the amount by which it is possible
to reduce GHG emissions or improve energy efficiency by
implementing a technology or practice that has already been
demonstrated. No explicit reference to costs is made but
adopting ‘practical constraints’ may take into account implicit
economic considerations.
• Physical potential is the theoretical (thermodynamic)
and sometimes, in practice, rather uncertain upper limit to
mitigation.
Precautionary Principle
A provision under Article 3 of the UNFCCC, stipulating that the
parties should take precautionary measures to anticipate, prevent
or minimize the causes of climate change and mitigate its adverse
effects. Where there are threats of serious or irreversible damage,
lack of full scientific certainty should not be used as a reason to
postpone such measures, taking into account that policies and
measures to deal with climate change should be cost-effective in
order to ensure global benefits at the lowest possible cost.
Precursors
Atmospheric compounds which themselves are not greenhouse
gases or aerosols, but which have an effect on greenhouse gas
or aerosol concentrations by taking part in physical or chemical
processes regulating their production or destruction rates.
Pre-industrial
The era before the industrial revolution of the late 18th and 19th
centuries, after which the use of fossil fuel for mechanization started
to increase.
Present value
The value of a money amount differs when the amount is available
at different moments in time (years). To make amounts at differing
times comparable and additive, a date is fixed as the ‘present’.
Amounts available at different dates in the future are discounted
back to a present value, and summed to get the present value of
a series of future cash flows. Net present value is the difference
between the present value of the revenues (benefits) with the present
value of the costs. See also discounting.
Price elasticity of demand
The ratio of the percentage change in the quantity of demand for a
good or service to one percentage change in the price of that good or
service. When the absolute value of the elasticity is between 0 and
, demand is called inelastic; when it is greater than one, demand is
called elastic.
‘Primary market’ and ‘secondary market’ trading
In commodities and financial exchanges, buyers and sellers who
trade directly with each other constitute the ‘primary market’,
while buying and selling through exchange facilities represent the
‘secondary market’.
Production frontier
The maximum outputs attainable with the optimal uses of available
inputs (natural resources, labour, capital, information).
Public sector leadership programmes in energy efficiency
Government purchasing and procurement of energy-efficient
products and services. Government agencies are responsible for
a wide range of energy-consuming facilities and services such as
government office buildings, schools, and health care facilities.
The government is often a country’s largest consumer of energy
and largest buyer of energy-using equipment. Indirect beneficial
impacts occur when governments act effectively as market leaders.
First, government buying power can create or expand demand for
energy-efficient products and services. Second, visible government
energy-saving actions can serve as an example for others.
Purchasing Power Parity (PPP)
The purchasing power of a currency is expressed using a basket of
goods and services that can be bought with a given amount in the
home country. International comparison of, e.g., Gross Domestic
Products of countries can be based on the purchasing power of
currencies rather than on current exchange rates. PPP estimates tend
to lower per capita GDPs in industrialized countries and raise per
capita GDPs in developing countries. (PPP is also an acronym for
polluter-pays-principle).


Radiative forcing
Radiative forcing is the change in the net vertical irradiance
(expressed in Watts per square metre: W/m2) at the tropopause
due to an internal change or a change in the external forcing of the
climate system, such as, for example, a change in the concentration
of CO2 or in the output of the sun.
Rebound effect
After implementation of efficient technologies and practices, part of
the savings is taken back for more intensive or other consumption,
e.g., improvements in car-engine efficiency lower the cost per
kilometre driven, encouraging more car trips or the purchase of a
more powerful vehicle.
Reforestation
Direct human-induced conversion of non-forested land to forested
land through planting, seeding and/or the human-induced promotion
of natural seed sources, on land that was previously forested but
converted to non-forested land. For the first commitment period
of the Kyoto Protocol, reforestation activities will be limited to
reforestation occurring on those lands that did not contain forest on
December 1989. See also afforestation and deforestation.
Reservoir
A component of the climate system, other than the atmosphere,
which has the capacity to store, accumulate or release a substance
of concern, e.g., carbon, a greenhouse gas or a precursor. Oceans,
soils, and forests are examples of reservoirs of carbon. Stock is the
absolute quantity of substance of concerns, held within a reservoir
at a specified time. See also Carbon pool.
Safe landing approach. See tolerable windows approach.
Scenario
A plausible description of how the future may develop based on
a coherent and internally consistent set of assumptions about
key driving forces (e.g., rate of technological change, prices)
and relationships. Note that scenarios are neither predictions nor
forecasts, but are useful to provide a view of the implications of
developments and actions.
Sequestration
Carbon storage in terrestrial or marine reservoirs. Biological
sequestration includes direct removal of CO2 from the atmosphere
through land-use change, afforestation, reforestation, carbon storage
in landfills and practices that enhance soil carbon in agriculture.
Shadow pricing
Setting prices of goods and services that are not, or incompletely,
priced by market forces or by administrative regulation, at the height
of their social marginal value. This technique is used in cost-benefit
analysis.
Sinks
Any process, activity or mechanism that removes a greenhouse gas
or aerosol, or a precursor of a greenhouse gas or aerosol from the
atmosphere.
Smart metering. See Intelligent control.
Social cost of carbon (SCC)
The discounted monetized sum (e.g. expressed as a price of
carbon in $/tCO2) of the annual net losses from impacts triggered
by an additional ton of carbon emitted today. According to usage
in economic theory, the social cost of carbon establishes an
economically optimal price of carbon at which the associated
marginal costs of mitigation would equal the marginal benefits of
mitigation.
Social unit costs of mitigation
Carbon prices in US$/tCO2 and US$/tC-eq (as affected by
mitigation policies and using social discount rates) required to
achieve a particular level of mitigation (economic potential) in
the form of a reduction below a baseline for GHG emissions. The
reduction is usually associated with a policy target, such as a cap
in an emissions trading scheme or a given level of stabilization of
GHG concentrations in the atmosphere.
Source
Source mostly refers to any process, activity or mechanism that
releases a greenhouse gas, aerosol or a precursor of a greenhouse
gas or aerosol into the atmosphere. Source can also refer to, e.g., an
energy source.
Specific energy use
The energy used in the production of a unit material, product or
service.
Spill-over effect
The effects of domestic or sector mitigation measures on other
countries or sectors. Spill-over effects can be positive or negative and
include effects on trade, carbon leakage, transfer of innovations, and
diffusion of environmentally sound technology and other issues.
Stabilization
Keeping constant the atmospheric concentrations of one or more
GHG (e.g., CO2) or of a CO2-equivalent basket of GHG. Stabilization
analyses or scenarios address the stabilization of the concentration
of GHG in the atmosphere.
Standards
Set of rules or codes mandating or defining product performance
(e.g., grades, dimensions, characteristics, test methods, and rules for
use). Product, technology or performance standards establish
minimum requirements for affected products or technologies.
Standards impose reductions in GHG emissions associated with
the manufacture or use of the products and/or application of the
technology.
Storyline
A narrative description of a scenario (or a family of scenarios) that
highlights the scenario’s main characteristics, relationships between
key driving forces, and the dynamics of the scenarios.
Structural change
Changes, for example, in the relative share of Gross Domestic
Product produced by the industrial, agricultural, or services sectors
of an economy; or more generally, systems transformations whereby
some components are either replaced or potentially substituted by
other ones.
Subsidy
Direct payment from the government or a tax reduction to a
private party for implementing a practice the government wishes
to encourage. The reduction of GHG emissions is stimulated by
lowering existing subsidies that have the effect of raising emissions
(such as subsidies to fossil fuel use) or by providing subsidies for
practices that reduce emissions or enhance sinks (e.g. for insulation
of buildings or for planting trees).
Sulphur hexafluoride (SF6)
One of the six greenhouse gases to be curbed under the Kyoto
Protocol. It is largely used in heavy industry to insulate high-voltage
equipment and to assist in the manufacturing of cable-cooling
systems and semi-conductors. Its Global Warming Potential is
,900.


Supplementarity
The Kyoto Protocol states that emissions trading and Joint
Implementation activities are to be supplemental to domestic
policies (e.g. energy taxes, fuel efficiency standards) taken by
developed countries to reduce their GHG emissions. Under some
proposed definitions of supplementarity (e.g., a concrete ceiling on
level of use), developed countries could be restricted in their use of
the Kyoto Mechanisms to achieve their reduction targets. This is a
subject for further negotiation and clarification by the parties.
Sustainable Development (SD)
The concept of sustainable development was introduced in the
World Conservation Strategy (IUCN 1980) and had its roots
in the concept of a sustainable society and in the management
of renewable resources. Adopted by the WCED in 1987 and
by the Rio Conference in 1992 as a process of change in which
the exploitation of resources, the direction of investments, the
orientation of technological development and institutional change
are all in harmony and enhance both current and future potential
to meet human needs and aspirations. SD integrates the political,
social, economic and environmental dimensions.
Targets and timetables
A target is the reduction of a specific percentage of GHG emissions
from a baseline date (e.g., below 1990 levels) to be achieved by a set
date or timetable (e.g., 2008-2012). Under the Kyoto Protocol the
EU agreed to reduce its GHG emissions by 8% below 1990 levels
by the 2008-2012 commitment period. Targets and timetables are
an emissions cap on the total amount of GHG emissions that can be
emitted by a country or region in a given time period.
Tax
A carbon tax is a levy on the carbon content of fossil fuels. Because
virtually all of the carbon in fossil fuels is ultimately emitted as
CO2, a carbon tax is equivalent to an emission tax on each unit of
CO2-equivalent emissions. An energy tax - a levy on the energy
content of fuels - reduces demand for energy and so reduces CO2
emissions from fossil fuel use. An eco-tax is designed to influence
human behaviour (specifically economic behaviour) to follow an
ecologically benign path.
An international carbon/emission/energy tax is a tax imposed
on specified sources in participating countries by an international
authority. The revenue is distributed or used as specified by this
authority or by participating countries. A harmonized tax commits
participating countries to impose a tax at a common rate on the same
sources, because imposing different rates across countries would
not be cost-effective. A tax credit is a reduction of tax in order
to stimulate purchasing of or investment in a certain product, like
GHG emission reducing technologies. A carbon charge is the same
as a carbon tax. See also Interaction effect
Technological change
Mostly considered as technological improvement, i.e., more or
better goods and services can be provided from a given amount
of resources (production factors). Economic models distinguish
autonomous (exogenous), endogenous and induced technological
change.
Autonomous (exogenous) technological change is imposed from
outside the model, usually in the form of a time trend affecting
energy demand or world output growth. Endogenous technological
change is the outcome of economic activity within the model, i.e.,
the choice of technologies is included within the model and affects
energy demand and/or economic growth. Induced technological
change implies endogenous technological change but adds further
changes induced by policies and measures, such as carbon taxes
triggering R&D efforts.
Technology
The practical application of knowledge to achieve particular tasks
that employs both technical artefacts (hardware, equipment) and
(social) information (‘software’, know-how for production and use
of artefacts).
Technology transfer
The exchange of knowledge, hardware and associated software,
money and goods among stakeholders, which leads to the spreading
of technology for adaptation or mitigation The term encompasses
both diffusion of technologies and technological cooperation across
and within countries.
Tolerable windows approach (TWA)
This approach seeks to identify the set of all climate-protection
strategies that are simultaneously compatible with 1) prescribed
long-term climate-protection goals, and 2) normative restrictions on
the emissions mitigation burden. The constraints may include limits
on the magnitude and rate of global mean temperature change, on
the weakening of the thermohaline circulation, on ecosystem losses
and on economic welfare losses resulting from selected climate
damages, adaptation costs and mitigation efforts. For a given set
of constraints, and given a solution exists, the TWA delineates an
emission corridor of complying emission paths.
Top-down models
Models applying macroeconomic theory, econometric and
optimization techniques to aggregate economic variables. Using
historical data on consumption, prices, incomes, and factor costs,
top-down models assess final demand for goods and services, and
supply from main sectors, such as the energy sector, transportation,
agriculture, and industry. Some top-down models incorporate
technology data, narrowing the gap to bottom-up models.
Trace gas
A minor constituent of the atmosphere, next to nitrogen and oxygen
that together make up 99% of all volume. The most important trace
gases contributing to the greenhouse effect are carbon dioxide, ozone,
methane, nitrous oxide, perfluorocarbons,
chlorofluorocarbons,
hydrofluorocarbons, sulphur hexafluoride and water vapour.
Tradable permit. See emission permit
Tradable quota system. See emissions trading.
Uncertainty
An expression of the degree to which a value is unknown (e.g. the
future state of the climate system). Uncertainty can result from lack
of information or from disagreement about what is known or even
knowable. It may have many types of sources, from quantifiable
errors in the data to ambiguously defined concepts or terminology, or
uncertain projections of human behavior. Uncertainty can therefore
be represented by quantitative measures (e.g., a range of values
calculated by various models) or by qualitative statements (e.g.,
reflecting the judgment of a team of experts). See also likelihood.
United Nations Framework Convention on Climate Change (UNFCCC)
The Convention was adopted on 9 May 1992 in New York and
signed at the 1992 Earth Summit in Rio de Janeiro by more than
countries and the European Economic Community. Its ultimate
objective is the ‘stabilization of greenhouse gas concentrations in the
atmosphere at a level that would prevent dangerous anthropogenic
interference with the climate system’. It contains commitments for
all parties. Under the Convention parties included in Annex I aimed
to return greenhouse gas emission not controlled by the Montreal
Protocol to 1990 levels by the year 2000. The convention came into
force in March 1994.


Value added
The net output of a sector or activity after adding up all outputs and
subtracting intermediate inputs.
Values
Worth, desirability or utility based on individual preferences. Most
social science disciplines use several definitions of value. Related
to nature and environment, there is a distinction between intrinsic
and instrumental values, the latter assigned by humans. Within
instrumental values, there is an unsettled catalogue of different
values, such as (direct and indirect) use, option, conservation,
serendipity, bequest, existence, etc.
Mainstream economics define the total value of any resource as the
sum of the values of the different individuals involved in the use
of the resource. The economic values, which are the foundation of
the estimation of costs, are measured in terms of the willingness to
pay by individuals to receive the resource or by the willingness of
individuals to accept payment to part with the resource. See also
contingent valuation method.
Voluntary action
Informal programmes, self-commitments and declarations, where
the parties (individual companies or groups of companies) entering
into the action set their own targets and often do their own monitoring
and reporting.
Voluntary agreement
An agreement between a government authority and one or more
private parties to achieve environmental objectives or to improve
environmental performance beyond compliance to regulated
obligations. Not all voluntary agreements are truly voluntary;
some include rewards and/or penalties associated with joining or
achieving commitments.
Acclimatisation
The physiological adaptation to climatic variations.
Active layer
The top layer of soil or rock in permafrost that is subjected to
seasonal freezing and thawing.
Adaptability
See adaptive capacity.
Adaptation
Adjustment in natural or human systems in response to actual or
expected climatic stimuli or their effects, which moderates harm
or exploits beneficial opportunities. Various types of adaptation
can be distinguished, including anticipatory, autonomous and
planned adaptation:
Anticipatory adaptation – Adaptation that takes place before
impacts of climate change are observed.Also referred
to as proactive adaptation.
Autonomous adaptation – Adaptation that does not constitute
a conscious response to climatic stimuli but is
triggered by ecological changes in natural systems
and by market or welfare changes in human systems.
Also referred to as spontaneous adaptation.
Planned adaptation – Adaptation that is the result of a deliberate
policy decision, based on an awareness that
conditions have changed or are about to change and
that action is required to return to, maintain, or
achieve a desired state.
Adaptation assessment
The practice of identifying options to adapt to climate change
and evaluating them in terms of criteria such as availability, benefits,
costs, effectiveness, efficiency and feasibility.
Adaptation benefits
The avoided damage costs or the accrued benefits following the
adoption and implementation of adaptation measures.
Adaptation costs
Costs of planning, preparing for, facilitating, and implementing
adaptation measures, including transition costs.
Adaptive capacity (in relation to climate change impacts)
The ability of a system to adjust to climate change (including
climate variability and extremes) to moderate potential damages,
to take advantage of opportunities, or to cope with the consequences.
Aerosols
A collection of air-borne solid or liquid particles, with a typical
size between 0.01 and 10 μm, that reside in the atmosphere for
at least several hours. Aerosols may be of either natural or anthropogenic
origin.Aerosols may influence climate in two ways:
directly through scattering and absorbing radiation, and indirectly
through acting as condensation nuclei for cloud formation
or modifying the optical properties and lifetime of clouds.
Afforestation
Direct human-induced conversion of land that has not been
forested for a period of at least 50 years to forested land through
planting, seeding and/or the human-induced promotion of natural
seed sources. See also reforestation and deforestation. For a
discussion of the term forest and related terms such as afforestation,
reforestation and deforestation, see the IPCC Special
Report on Land Use, Land-Use Change, and Forestry (IPCC,
).
Aggregate impacts
Total impacts integrated across sectors and/or regions. The aggregation
of impacts requires knowledge of (or assumptions
about) the relative importance of impacts in different sectors and
regions. Measures of aggregate impacts include, for example,
the total number of people affected, or the total economic costs.
Albedo
The fraction of solar radiation reflected by a surface or object,
often expressed as a percentage. Snow-covered surfaces have a
Appendix I: Glossary
Notes:
. This glossary defines some specific terms as the lead authors intend them to be interpreted in the context of this Report.
.Words in italic indicate that the following term is also contained in this glossary.
high albedo; the albedo of soils ranges from high to low; vegetation-
covered surfaces and oceans have a low albedo. The
Earth’s albedo varies mainly through varying cloudiness, snow,
ice, leaf area, and land-cover changes.
Algae
Photosynthetic, often microscopic and planktonic, organisms occurring
in marine and freshwater ecosystems.
Algal bloom
A reproductive explosion of algae in a lake, river or ocean.
Alpine
The biogeographic zone made up of slopes above the tree line
characterised by the presence of rosette-forming herbaceous
plants and low, shrubby, slow-growing woody plants.
Anthropogenic
Resulting from or produced by human beings.
AOGCM
See climate model.
Aquaculture
The managed cultivation of aquatic plants or animals such as
salmon or shellfish held in captivity for the purpose of harvesting.
Aquifer
A stratum of permeable rock that bears water. An unconfined
aquifer is recharged directly by local rainfall, rivers and lakes,
and the rate of recharge will be influenced by the permeability
of the overlying rocks and soils.
Aragonite
Acalcium carbonate (limestone) mineral, used by shell- or skeleton-
forming, calcifying organisms such as corals (warm- and coldwater
corals), some macroalgae, pteropods (marine snails) and
non-pteropod molluscs such as bivalves (e.g., clams, oysters),
cephalopods (e.g., squids, octopuses).Aragonite is more sensitive
to ocean acidification than calcite, also used by many marine organisms.
See also calcite and ocean acidification.
Arbovirus
Any of various viruses transmitted by blood-sucking arthropods
(e.g., mosquitoes, ticks, etc.) and including the causative agents
of dengue fever, yellow fever, and some types of encephalitis.
Arid region
A land region of low rainfall, where ‘low’ is widely accepted to
be <250 mm precipitation per year.
Atmosphere
The gaseous envelope surrounding the Earth. The dry atmosphere
consists almost entirely of nitrogen and oxygen, together
with trace gases including carbon dioxide and ozone.
Attribution
See Detection and attribution
Baseline/reference
The baseline (or reference) is the state against which change is
measured. It might be a ‘current baseline’, in which case it represents
observable, present-day conditions. It might also be a
‘future baseline’, which is a projected future set of conditions
excluding the driving factor of interest. Alternative interpretations
of the reference conditions can give rise to multiple baselines.
Basin
The drainage area of a stream, river or lake.
Benthic community
The community of organisms living on or near the bottom of a
water body such as a river, a lake or an ocean.
Biodiversity
The total diversity of all organisms and ecosystems at various
spatial scales (from genes to entire biomes).
Biofuel
A fuel produced from organic matter or combustible oils produced
by plants. Examples of biofuel include alcohol, black
liquor from the paper-manufacturing process, wood, and soybean
oil.
Biomass
The total mass of living organisms in a given area or volume; recently
dead plant material is often included as dead biomass.
The quantity of biomass is expressed as a dry weight or as the
energy, carbon or nitrogen content.
Biome
Major and distinct regional element of the biosphere, typically
consisting of several ecosystems (e.g., forests, rivers, ponds,
swamps) within a region of similar climate. Biomes are characterised
by typical communities of plants and animals.
Biosphere
The part of the Earth system comprising all ecosystems and living
organisms in the atmosphere, on land (terrestrial biosphere),
or in the oceans (marine biosphere), including derived dead organic
matter, such as litter, soil organic matter, and oceanic detritus.
Biota
All living organisms of an area; the flora and fauna considered
as a unit.
Bog
Peat-accumulating acidic wetland.
Boreal forest
Forests of pine, spruce, fir and larch stretching from the east
coast of Canada westward toAlaska and continuing from Siberia
Appendix I: Glossary

westward across the entire extent of Russia to the European
Plain. The climate is continental, with long, very cold winters
(up to 6 months with mean temperatures below freezing), and
short, cool summers (50 to 100 frost-free days). Precipitation increases
during summer months, although annual precipitation is
still small. Low evaporation rates can make this a humid climate.
See taiga.
Breakwater
Ahard engineering structure built in the sea which, by breaking
waves, protects a harbour, anchorage, beach or shore area. A
breakwater can be attached to the coast or lie offshore.
C3 plants
Plants that produce a three-carbon compound during photosynthesis,
including most trees and agricultural crops such as rice,
wheat, soybeans, potatoes and vegetables.
C4 plants
Plants, mainly of tropical origin, that produce a four-carbon compound
during photosynthesis, includingmany grasses and the agriculturally
important cropsmaize, sugar cane,millet and sorghum.
Calcareous organisms
A large and diverse group of organisms, many marine, that use
calcite or aragonite to form shells or skeletons. See calcite,
aragonite and ocean acidification.
Calcite
A calcium carbonate (limestone) mineral, used by shell- or
skeleton-forming, calcifying organisms such as foraminifera,
some macroalgae, lobsters, crabs, sea urchins and starfish. Calcite
is less sensitive to ocean acidification than aragonite, also
used by many marine organisms. See also aragonite and ocean
acidification.
Capacity building
In the context of climate change, capacity building is developing
the technical skills and institutional capabilities in developing
countries and economies in transition to enable their
participation in all aspects of adaptation to, mitigation of, and research
on climate change, and in the implementation of the
Kyoto Mechanisms, etc.
Carbon cycle
The term used to describe the flow of carbon (in various forms,
e.g., carbon dioxide) through the atmosphere, ocean, terrestrial
biosphere and lithosphere.
Carbon dioxide (CO2)
A naturally occurring gas fixed by photosynthesis into organic
matter. A by-product of fossil fuel combustion and biomass
burning, it is also emitted from land-use changes and other industrial
processes. It is the principal anthropogenic greenhouse
gas that affects the Earth’s radiative balance. It is the reference
gas against which other greenhouse gases are measured, thus
having a GlobalWarming Potential of 1.
Carbon dioxide fertilisation
The stimulation of plant photosynthesis due to elevated CO2 concentrations, leading to either enhanced productivity and/or
efficiency of primary production. In general, C3 plants show a
larger response to elevated CO2 than C4 plants.
Carbon sequestration
The process of increasing the carbon content of a reservoir/pool
other than the atmosphere.
Catchment
An area that collects and drains rainwater.
CDM (Clean Development Mechanism)
The CDM allows greenhouse gas emission reduction projects
to take place in countries that have no emission targets under the
United Nations Framework Convention on Climate Change
(UNFCCC) Kyoto Protocol, yet are signatories.
Chagas’ disease
A parasitic disease caused by the Trypanosoma cruzi and transmitted
by triatomine bugs in the Americas, with two clinical periods:
acute (fever, swelling of the spleen, oedemas) and chronic
(digestive syndrome, potentially fatal heart condition).
Cholera
A water-borne intestinal infection caused by a bacterium (Vibrio
cholerae) that results in frequent watery stools, cramping abdominal
pain, and eventual collapse from dehydration and
shock.
Climate
Climate in a narrow sense is usually defined as the ‘average
weather’, or more rigorously, as the statistical description in
terms of the mean and variability of relevant quantities over a
period of time ranging from months to thousands or millions of
years. These quantities are most often surface variables such as
temperature, precipitation, and wind. Climate in a wider sense is
the state, including a statistical description, of the climate system.
The classical period of time is 30 years, as defined by the
World Meteorological Organization (WMO).
Climate change
Climate change refers to any change in climate over time,
whether due to natural variability or as a result of human activity.
This usage differs from that in the United Nations Framework
Convention on Climate Change (UNFCCC), which defines
‘climate change’ as: ‘a change of climate which is attributed directly
or indirectly to human activity that alters the composition
of the global atmosphere and which is in addition to natural climate
variability observed over comparable time periods’. See
also climate variability.
Climate change commitment
Due to the thermal inertia of the ocean and slow processes in the
biosphere, the cryosphere and land surfaces, the climate would
continue to change even if the atmospheric composition was
held fixed at today’s values. Past change in atmospheric com-
Appendix I: Glossary

Appendix I: Glossary

position leads to a ‘committed’ climate change which continues
for as long as a radiative imbalance persists and until all components
of the climate system have adjusted to a new state. The
further change in temperature after the composition of the atmosphere
is held constant is referred to as the committed warming
or warming commitment. Climate change commitment
includes other future changes, for example in the hydrological
cycle, in extreme weather events, and in sea-level rise.
Climate model
A numerical representation of the climate system based on the
physical, chemical, and biological properties of its components,
their interactions and feedback processes, and accounting for all
or some of its known properties. The climate system can be represented
by models of varying complexity (i.e., for any one component
or combination of components a hierarchy of models can
be identified, differing in such aspects as the number of spatial
dimensions, the extent to which physical, chemical, or biological
processes are explicitly represented, or the level at which
empirical parameterisations are involved. Coupled atmosphere/
ocean/sea-ice General Circulation Models (AOGCMs)
provide a comprehensive representation of the climate system.
More complex models include active chemistry and biology. Climate
models are applied, as a research tool, to study and simulate
the climate, but also for operational purposes, including
monthly, seasonal, and interannual climate predictions.
Climate prediction
A climate prediction or climate forecast is the result of an attempt
to produce an estimate of the actual evolution of the climate
in the future, e.g., at seasonal, interannual or long-term
time scales. See also climate projection and climate (change)
scenario.
Climate projection
The calculated response of the climate system to emissions or
concentration scenarios of greenhouse gases and aerosols, or
radiative forcing scenarios, often based on simulations by climate
models. Climate projections are distinguished from climate
predictions, in that the former critically depend on the emissions/
concentration/radiative forcing scenario used, and therefore
on highly uncertain assumptions of future socio-economic
and technological development.
Climate (change) scenario
Aplausible and often simplified representation of the future climate,
based on an internally consistent set of climatological relationships
and assumptions of radiative forcing, typically
constructed for explicit use as input to climate change impact
models.A‘climate change scenario’ is the difference between a
climate scenario and the current climate.
Climate sensitivity
The equilibrium temperature rise that would occur for a doubling
of CO2 concentration above pre-industrial levels.
Climate system
The climate system is defined by the dynamics and interactions
of five major components: atmosphere, hydrosphere, cryosphere,
land surface, and biosphere. Climate system dynamics
are driven by both internal and external forcing, such as volcanic
eruptions, solar variations, or human-induced modifications to
the planetary radiative balance, for instance via anthropogenic
emissions of greenhouse gases and/or land-use changes.
Climate threshold
The point at which external forcing of the climate system, such
as the increasing atmospheric concentration of greenhouse
gases, triggers a significant climatic or environmental event
which is considered unalterable, or recoverable only on very
long time-scales, such as widespread bleaching of corals or a
collapse of oceanic circulation systems.
Climate variability
Climate variability refers to variations in the mean state and
other statistics (such as standard deviations, statistics of extremes,
etc.) of the climate on all temporal and spatial scales beyond
that of individual weather events. Variability may be due
to natural internal processes within the climate system (internal
variability), or to variations in natural or anthropogenic external
forcing (external variability). See also climate change.
CO2 fertilisation
See carbon dioxide fertilisation.
Coastal squeeze
The squeeze of coastal ecosystems (e.g., salt marshes, mangroves
and mud and sand flats) between rising sea levels and
naturally or artificially fixed shorelines, including hard engineering
defences (see Chapter 6).
Coccolithophores
Single-celled microscopic phytoplankton algae which construct
shell-like structures from calcite (a form of calcium carbonate).
See also calcite and ocean acidification.
Committed to extinction
This term describes a species with dwindling population that is
in the process of inescapably becoming extinct in the absence
of human intervention. See also extinction.
Communicable disease
An infectious disease caused by transmission of an infective biological
agent (virus, bacterium, protozoan, or multicellular
macroparasite).
Confidence
In this Report, the level of confidence in a statement is expressed
using a standard terminology defined in the Introduction. See
also uncertainty.
Control run
A model run carried out to provide a ‘baseline’ for comparison
with climate-change experiments. The control run uses constant
values for the radiative forcing due to greenhouse gases and anthropogenic
aerosols appropriate to pre-industrial conditions.
Appendix I: Glossary

Coral
The term ‘coral’ has several meanings, but is usually the common
name for the Order Scleractinia, all members of which have
hard limestone skeletons, and which are divided into reef-building
and non-reef-building, or cold- and warm-water corals.
Coral bleaching
The paling in colour which results if a coral loses its symbiotic,
energy-providing, organisms.
Coral reefs
Rock-like limestone (calcium carbonate) structures built by
corals along ocean coasts (fringing reefs) or on top of shallow,
submerged banks or shelves (barrier reefs, atolls), most conspicuous
in tropical and sub-tropical oceans.
Cryosphere
The component of the climate system consisting of all snow and
ice (including permafrost) on and beneath the surface of the
Earth and ocean.
Cryptogams
An outdated but still-used term, denoting a group of diverse and
taxonomically unrelated organisms, including fungi and lower
plants such as algae, lichens, hornworts, liverworts, mosses and
ferns.
Deforestation
Natural or anthropogenic process that converts forest land to
non-forest. See afforestation and reforestation.
Dengue fever
An infectious viral disease spread by mosquitoes, often called
breakbone fever because it is characterised by severe pain in the
joints and back. Subsequent infections of the virus may lead to
dengue haemorrhagic fever (DHF) and dengue shock syndrome
(DSS), which may be fatal.
Desert
A region of very low rainfall, where ‘very low’ is widely accepted
to be <100 mm per year.
Desertification
Land degradation in arid, semi-arid, and dry sub-humid areas
resulting from various factors, including climatic variations and
human activities. Further, the United Nations Convention to
Combat Desertification (UNCCD) defines land degradation as a
reduction or loss in arid, semi-arid, and dry sub-humid areas of
the biological or economic productivity and complexity of rainfed
cropland, irrigated cropland, or range, pasture, forest and
woodlands resulting from land uses or from a process or combination
of processes, including those arising from human activities
and habitation patterns, such as: (i) soil erosion caused by
wind and/or water; (ii) deterioration of the physical, chemical,
and biological or economic properties of soil; and (iii) long-term
loss of natural vegetation.
Detection and attribution
Detection of change in a system (natural or human) is the
process of demonstrating that the system has changed in some
defined statistical sense, without providing a reason for that
change.
Attribution of such an observed change in a system to anthropogenic
climate change is usually a two-stage process. First, the
observed change in the system must be demonstrated to be associated
with an observed regional climate change with a specified
degree of confidence. Second, a measurable portion of the
observed regional climate change, or the associated observed
change in the system, must be attributed to anthropogenic climate
forcing with a similar degree of confidence.
Confidence in such joint attribution statements must be lower
than the confidence in either of the individual attribution steps
alone due to the combination of two separate statistical assessments.
Diadromous
Fish that travel between salt water and freshwater.
Discount rate
The degree to which consumption now is preferred to consumption
one year hence, with prices held constant, but average
incomes rising in line with GDP per capita.
Disturbance regime
Frequency, intensity, and types of disturbances, such as fires, insect
or pest outbreaks, floods and droughts.
Downscaling
A method that derives local- to regional-scale (10 to 100 km)
information from larger-scale models or data analyses.
Drought
The phenomenon that exists when precipitation is significantly
below normal recorded levels, causing serious hydrological imbalances
that often adversely affect land resources and production
systems.
Dyke
A human-made wall or embankment along a shore to prevent
flooding of low-lying land.
Dynamic global vegetation model (DGVM)
Models that simulate vegetation development and dynamics
through space and time, as driven by climate and other environmental
changes.
Ecological community
Acommunity of plants and animals characterised by a typical assemblage
of species and their abundances. See also ecosystem.
Ecological corridor
A thin strip of vegetation used by wildlife, potentially allowing
movement of biotic factors between two areas.
Ecophysiological process
Individual organisms respond to environmental variability, such
as climate change, through ecophysiological processes which
operate continuously, generally at a microscopic or sub-organ
scale. Ecophysiological mechanisms underpin individual organism’s
tolerance to environmental stress, and comprise a
broad range of responses defining the absolute tolerance limits
of individuals to environmental conditions. Ecophysiological responses
may scale up to control species geographic ranges.
Ecosystem
The interactive system formed from all living organisms and
their abiotic (physical and chemical) environment within a given
area. Ecosystems cover a hierarchy of spatial scales and can
comprise the entire globe, biomes at the continental scale or
small, well-circumscribed systems such as a small pond.
Ecosystem approach
The ecosystem approach is a strategy for the integrated management
of land, water and living resources that promotes conservation
and sustainable use in an equitable way.An ecosystem
approach is based on the application of appropriate scientific
methodologies focused on levels of biological organisation,
which encompass the essential structure, processes, functions
and interactions among organisms and their environment. It
recognises that humans, with their cultural diversity, are an integral
component of many ecosystems. The ecosystem approach
requires adaptive management to deal with the complex and dynamic
nature of ecosystems and the absence of complete knowledge
or understanding of their functioning. Priority targets are
conservation of biodiversity and of the ecosystem structure and
functioning, in order to maintain ecosystem services.
Ecosystem services
Ecological processes or functions having monetary or non-monetary
value to individuals or society at large. There are (i) supporting
services such as productivity or biodiversity
maintenance, (ii) provisioning services such as food, fibre, or
fish, (iii) regulating services such as climate regulation or carbon
sequestration, and (iv) cultural services such as tourism or
spiritual and aesthetic appreciation.
Ecotone
Transition area between adjacent ecological communities (e.g.,
between forests and grasslands).
El Niño-Southern Oscillation (ENSO)
El Niño, in its original sense, is a warm-water current that periodically
flows along the coast of Ecuador and Peru, disrupting the
local fishery. This oceanic event is associated with a fluctuation of
the inter-tropical surface pressure pattern and circulation in the Indian
and PacificOceans, called the SouthernOscillation. This coupled
atmosphere-ocean phenomenon is collectively known as El
Niño-Southern Oscillation. During an El Niño event, the prevailing
tradewindsweaken and the equatorial countercurrent strengthens,
causing warm surface waters in the Indonesian area to flow
eastward to overlie the cold waters of the Peru current. This event
has great impact on the wind, sea surface temperature, and precipitation
patterns in the tropical Pacific. It has climatic effects
throughout the Pacific region and inmany other parts of theworld.
The opposite of an El Niño event is called La Niña.
Emissions scenario
A plausible representation of the future development of emissions
of substances that are potentially radiatively active (e.g.,
greenhouse gases, aerosols), based on a coherent and internally
consistent set of assumptions about driving forces (such as demographic
and socio-economic development, technological
change) and their key relationships. In 1992, the IPCC presented
a set of emissions scenarios that were used as a basis for the climate
projections in the SecondAssessment Report. These emissions
scenarios are referred to as the IS92 scenarios. In the IPCC
Special Report on Emissions Scenarios (SRES) (Nakićenović et
al., 2000), new emissions scenarios – the so-called SRES scenarios
– were published.
Endemic
Restricted or peculiar to a locality or region. With regard to
human health, endemic can refer to a disease or agent present
or usually prevalent in a population or geographical area at all
times.
Ensemble
A group of parallel model simulations used for climate projections.
Variation of the results across the ensemble members gives
an estimate of uncertainty. Ensembles made with the same
model but different initial conditions only characterise the uncertainty
associated with internal climate variability, whereas
multi-model ensembles including simulations by several models
also include the impact of model differences.
Epidemic
Occurring suddenly in incidence rates clearly in excess of normal
expectancy, applied especially to infectious diseases but
may also refer to any disease, injury, or other health-related
event occurring in such outbreaks.
Erosion
The process of removal and transport of soil and rock by weathering,
mass wasting, and the action of streams, glaciers, waves,
winds and underground water.
Eustatic sea-level rise
See sea-level rise.
Eutrophication
The process by which a body of water (often shallow) becomes
(either naturally or by pollution) rich in dissolved nutrients, with
a seasonal deficiency in dissolved oxygen.
Evaporation
The transition process from liquid to gaseous state.
Evapotranspiration
The combined process of water evaporation from the Earth’s
surface and transpiration from vegetation.
Appendix I: Glossary

Externalities
Occur when a change in the production or consumption of one
individual or firm affects indirectly the well-being of another individual
or firm. Externalities can be positive or negative. The
impacts of pollution on ecosystems, water courses or air quality
represent classic cases of negative externality.
Extinction
The global disappearance of an entire species.
Extirpation
The disappearance of a species from part of its range; local extinction.
Extreme weather event
An event that is rare within its statistical reference distribution
at a particular place. Definitions of ‘rare’ vary, but an extreme
weather event would normally be as rare as or rarer than the 10th
or 90th percentile. By definition, the characteristics of what is
called ‘extreme weather’may vary from place to place. Extreme
weather events may typically include floods and droughts.
Feedback
An interaction mechanism between processes is called a feedback.
When the result of an initial process triggers changes in a
second process and that in turn influences the initial one.Apositive
feedback intensifies the original process, and a negative
feedback reduces it.
Food chain
The chain of trophic relationships formed if several species feed
on each other. See food web and trophic level.
Food security
A situation that exists when people have secure access to sufficient
amounts of safe and nutritious food for normal growth, development
and an active and healthy life. Food insecurity may
be caused by the unavailability of food, insufficient purchasing
power, inappropriate distribution, or inadequate use of food at
the household level.
Food web
The network of trophic relationships within an ecological community
involving several interconnected food chains.
Forecast
See climate prediction and climate projection.
Forest limit/line
The upper elevational or latitudinal limit beyond which natural
tree regeneration cannot develop into a closed forest stand. It is
typically at a lower elevation or more distant from the poles than
the tree line.
Freshwater lens
A lenticular fresh groundwater body that underlies an oceanic
island. It is underlain by saline water.
Functional extinction
This term defines a species which has lost its capacity to persist
and to recover because its populations have declined to below a
minimum size. See committed to extinction.
General Circulation Model (GCM)
See climate model.
Generalist
A species that can tolerate a wide range of environmental conditions.
Glacier
A mass of land ice flowing downhill (by internal deformation
and sliding at the base) and constrained by the surrounding topography
(e.g., the sides of a valley or surrounding peaks). A
glacier is maintained by accumulation of snow at high altitudes,
balanced by melting at low altitudes or discharge into the sea.
Globalisation
The growing integration and interdependence of countries
worldwide through the increasing volume and variety of crossborder
transactions in goods and services, free international capital
flows, and the more rapid and widespread diffusion of
technology, information and culture.
Greenhouse effect
The process in which the absorption of infrared radiation by the
atmosphere warms the Earth.
In common parlance, the term ‘greenhouse effect’ may be used
to refer either to the natural greenhouse effect, due to naturally
occurring greenhouse gases, or to the enhanced (anthropogenic)
greenhouse effect, which results from gases emitted as a result
of human activities.
Greenhouse gas
Greenhouse gases are those gaseous constituents of the atmosphere,
both natural and anthropogenic, that absorb and emit radiation
at specific wavelengths within the spectrum of infrared
radiation emitted by the Earth’s surface, the atmosphere, and
clouds. This property causes the greenhouse effect.Water vapour
(H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane
(CH4) and ozone (O3) are the primary greenhouse gases in the
Earth’s atmosphere. As well as CO2, N2O, and CH4, the Kyoto
Protocol deals with the greenhouse gases sulphur hexafluoride
(SF6), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs).
Gross Domestic Product
Gross Domestic Product (GDP) is the monetary value of all
goods and services produced within a nation.
Gross National Product
Gross National Product (GNP) is the monetary value of all goods
and services produced in a nation’s economy, including income
generated abroad by domestic residents, but without income
generated by foreigners.
Appendix I: Glossary

Gross primary production
The total carbon fixed by plant through photosynthesis.
Groundwater recharge
The process by which external water is added to the zone of saturation
of an aquifer, either directly into a formation or indirectly
by way of another formation.
Groyne
Alow, narrow jetty, usually extending roughly perpendicular to
the shoreline, designed to protect the shore from erosion by currents,
tides or waves, by trapping sand for the purpose of replenishing
or making a beach.
Habitat
The locality or natural home in which a particular plant, animal,
or group of closely associated organisms lives.
Hantavirus
A virus in the family Bunyaviridae that causes a type of haemorrhagic
fever. It is thought that humans catch the disease mainly
from infected rodents, either through direct contact with the animals
or by inhaling or ingesting dust that contains aerosolised
viral particles from their dried urine and other secretions.
Heat island
An urban area characterised by ambient temperatures higher
than those of the surrounding non-urban area. The cause is a
higher absorption of solar energy by materials of the urban fabric
such as asphalt.
Herbaceous
Flowering, non-woody.
Human system
Any system in which human organisations play a major role.
Often, but not always, the term is synonymous with ‘society’ or
‘social system’ e.g., agricultural system, political system, technological
system, economic system; all are human systems in
the sense applied in the AR4.
Hydrographic events
Events that alter the state or current of waters in oceans, rivers
or lakes.
Hydrological systems
The systems involved in movement, distribution, and quality of
water throughout the Earth, including both the hydrologic cycle
and water resources.
Hypolimnetic
Referring to the part of a lake below the thermocline made up of
water that is stagnant and of essentially uniform temperature except
during the period of overturn.
Hypoxic events
Events that lead to a deficiency of oxygen.
Ice cap
A dome-shaped ice mass covering a highland area that is considerably
smaller in extent than an ice sheet.
Ice sheet
A mass of land ice that is sufficiently deep to cover most of the
underlying bedrock topography. An ice sheet flows outwards
from a high central plateau with a small average surface slope.
The margins slope steeply, and the ice is discharged through fastflowing
ice streams or outlet glaciers, in some cases into the sea
or into ice shelves floating on the sea. There are only two large
ice sheets in the modern world – on Greenland and Antarctica,
the Antarctic ice sheet being divided into east and west by the
TransantarcticMountains; during glacial periods there were others.
Ice shelf
Afloating ice sheet of considerable thickness attached to a coast
(usually of great horizontal extent with a level or gently undulating
surface); often a seaward extension of ice sheets. Nearly
all ice shelves are in Antarctica.
(climate change) Impact assessment
The practice of identifying and evaluating, in monetary and/or
non-monetary terms, the effects of climate change on natural
and human systems.
(climate change) Impacts
The effects of climate change on natural and human systems.
Depending on the consideration of adaptation, one can distinguish
between potential impacts and residual impacts:
Potential impacts: all impacts that may occur given a projected
change in climate, without considering adaptation.
Residual impacts: the impacts of climate change that would
occur after adaptation. See also aggregate impacts, market
impacts, and non-market impacts.
Indigenous peoples
No internationally accepted definition of indigenous peoples exists.
Common characteristics often applied under international
law, and by United Nations agencies to distinguish indigenous
peoples include: residence within or attachment to geographically
distinct traditional habitats, ancestral territories, and their
natural resources; maintenance of cultural and social identities,
and social, economic, cultural and political institutions separate
from mainstream or dominant societies and cultures; descent
from population groups present in a given area, most frequently
before modern states or territories were created and current borders
defined; and self-identification as being part of a distinct
indigenous cultural group, and the desire to preserve that cultural
identity.
Industrial revolution
Aperiod of rapid industrial growth with far-reaching social and
economic consequences, beginning in England during the second
half of the 18th century and spreading to Europe and later
to other countries including the USA. The industrial revolution
marks the beginning of a strong increase in combustion of fos-
Appendix I: Glossary

sil fuels and related emissions of carbon dioxide. In the AR4,
the term ‘pre-industrial’ refers, somewhat arbitrarily, to the period
before 1750.
Infectious disease
Any disease caused by microbial agents that can be transmitted
from one person to another or from animals to people. This may
occur by direct physical contact, by handling of an object that
has picked up infective organisms, through a disease carrier, via
contaminated water, or by the spread of infected droplets
coughed or exhaled into the air.
Infrastructure
The basic equipment, utilities, productive enterprises, installations
and services essential for the development, operation and
growth of an organisation, city or nation.
Integrated assessment
An interdisciplinary process of combining, interpreting and
communicating knowledge from diverse scientific disciplines
so that all relevant aspects of a complex societal issue can be
evaluated and considered for the benefit of decision-making.
Integrated water resources management (IWRM)
The prevailing concept for water management which, however,
has not been defined unambiguously. IWRM is based on four
principles that were formulated by the International Conference
onWater and the Environment in Dublin, 1992: (1) fresh water
is a finite and vulnerable resource, essential to sustain life, development
and the environment; (2) water development and
management should be based on a participatory approach, involving
users, planners and policy-makers at all levels; (3)
women play a central part in the provision, management and
safeguarding of water; (4) water has an economic value in all its
competing uses and should be recognised as an economic good.
Invasive species and invasive alien species (IAS)
Aspecies aggressively expanding its range and population density
into a region in which it is not native, often through outcompeting
or otherwise dominating native species.
Irrigation water-use efficiency
Irrigation water-use efficiency is the amount of biomass or seed
yield produced per unit irrigation water applied, typically about
tonne of dry matter per 100 mm water applied.
Isohyet
A line on a map connecting locations that receive the same
amount of rainfall.
Joint attribution
Involves both attribution of observed changes to regional climate
change and attribution of a measurable portion of either
regional climate change or the associated observed changes in
the system to anthropogenic causes, beyond natural variability.
This process involves statistically linking climate-change simulations
from climate models with the observed responses in the
natural or managed system. Confidence in joint attribution statements
must be lower than the confidence in either of the individual
attribution steps alone due to the combination of two separate
statistical assessments.
Keystone species
A species that has a central servicing role affecting many other
organisms and whose demise is likely to result in the loss of a
number of species and lead to major changes in ecosystem function.
Kyoto Protocol
The Kyoto Protocol was adopted at the Third Session of the
Conference of the Parties (COP) to the UN Framework Convention
on Climate Change (UNFCCC) in 1997 in Kyoto, Japan.
It contains legally binding commitments, in addition to those included
in the UNFCCC. Countries included in Annex B of the
Protocol (most member countries of the Organisation for Economic
Cooperation and Development (OECD) and those with
economies in transition) agreed to reduce their anthropogenic
greenhouse gas emissions (CO2, CH4, N2O, HFCs, PFCs, and
SF6) by at least 5% below 1990 levels in the commitment period
to 2012. The Kyoto Protocol entered into force on 16 February
.
La Niña
See El Niño-Southern Oscillation (ENSO).
Landslide
Amass of material that has slipped downhill by gravity, often assisted
by water when the material is saturated; the rapid movement
of a mass of soil, rock or debris down a slope.
Large-scale singularities
Abrupt and dramatic changes in the state of given systems, in
response to gradual changes in driving forces. For example, a
gradual increase in atmospheric greenhouse gas concentrations
may lead to such large-scale singularities as slowdown or collapse
of the thermohaline circulation or collapse of the West
Antarctic ice sheet. The occurrence, magnitude, and timing of
large-scale singularities are difficult to predict.
Last Glacial Maximum
The Last Glacial Maximum refers to the time of maximum extent
of the ice sheets during the last glaciation, approximately
,000 years ago.
Leaching
The removal of soil elements or applied chemicals by water
movement through the soil.
Leaf area index (LAI)
The ratio between the total leaf surface area of a plant and the
ground area covered by its leaves.
Legume
Plants that fix nitrogen from the air through a symbiotic relationship
with bacteria in their soil and root systems (e.g., soybean,
peas, beans, lucerne, clovers).
Appendix I: Glossary

Likelihood
The likelihood of an occurrence, an outcome or a result, where
this can be estimated probabilistically, is expressed in this Report
using a standard terminology, defined in the Introduction. See
also uncertainty and confidence.
Limnology
Study of lakes and their biota.
Littoral zone
A coastal region; the zone between high and low watermarks.
Malaria
Endemic or epidemic parasitic disease caused by species of the
genus Plasmodium (Protozoa) and transmitted by mosquitoes of
the genus Anopheles; produces bouts of high fever and systemic
disorders, affects about 300 million and kills approximately
million people worldwide every year.
Market impacts
Impacts that can be quantified in monetary terms, and directly
affect Gross Domestic Product – e.g., changes in the price of
agricultural inputs and/or goods. See also non-market impacts.
Meningitis
Inflammation of the meninges (part of the covering of the brain),
usually caused by bacteria, viruses or fungi.
Meridional overturning circulation (MOC)
See thermohaline circulation (THC).
Microclimate
Local climate at or near the Earth’s surface. See also climate.
Millennium Development Goals (MDGs)
A list of ten goals, including eradicating extreme poverty and
hunger, improving maternal health, and ensuring environmental
sustainability, adopted in 2000 by the UN General Assembly,
i.e., 191 States, to be reached by 2015. The MDGs commit the
international community to an expanded vision of development,
and have been commonly accepted as a framework for measuring
development progress.
Mires
Peat-accumulating wetlands. See bog.
Mitigation
An anthropogenic intervention to reduce the anthropogenic forcing
of the climate system; it includes strategies to reduce greenhouse
gas sources and emissions and enhancing greenhouse gas
sinks.
Mixed layer
The upper region of the ocean, well mixed by interaction with
the overlying atmosphere.
Monsoon
A monsoon is a tropical and sub-tropical seasonal reversal in
both the surface winds and associated precipitation.
Montane
The biogeographic zone made up of relatively moist, cool upland
slopes below the sub-alpine zone that is characterised by
the presence of mixed deciduous at lower and coniferous evergreen
forests at higher elevations.
Morbidity
Rate of occurrence of disease or other health disorders within a
population, taking account of the age-specific morbidity rates.
Morbidity indicators include chronic disease incidence/prevalence,
rates of hospitalisation, primary care consultations, disability-
days (i.e., days of absence from work), and prevalence
of symptoms.
Morphology
The form and structure of an organism or land-form, or any of
its parts.
Mortality
Rate of occurrence of deathwithin a population; calculation ofmortality
takes account of age-specific death rates, and can thus yield
measures of life expectancy and the extent of premature death.
Net biome production (NBP)
Net biome production is the net ecosystem production (NEP)
minus carbon losses resulting from disturbances such as fire or
insect defoliation.
Net ecosystem production (NEP)
Net ecosystem production is the difference between net primary
production (NPP) and heterotrophic respiration (mostly decomposition
of dead organic matter) of that ecosystem over the
same area (see also net biome production (NBP).
Net primary production (NPP)
Net primary production is the gross primary production minus
autotrophic respiration, i.e., the sum of metabolic processes for
plant growth and maintenance, over the same area.
Nitrogen oxides (NOx)
Any of several oxides of nitrogen.
No regrets policy
A policy that would generate net social and/or economic benefits
irrespective of whether or not anthropogenic climate change
occurs.
Non-linearity
Aprocess is called ‘non-linear’ when there is no simple proportional
relation between cause and effect.
Non-market impacts
Impacts that affect ecosystems or human welfare, but that are
not easily expressed in monetary terms, e.g., an increased risk of
premature death, or increases in the number of people at risk of
hunger. See also market impacts.
Appendix I: Glossary

Normalised difference vegetation index (NDVI)
Asatellite-based remotely sensed measure of the ‘greenness’ of
the vegetation cover.
North Atlantic Oscillation (NAO)
The NorthAtlantic Oscillation (NAO) consists of opposing variations
of barometric pressure near Iceland and near the Azores.
It is the dominant mode of winter climate variability in the North
Atlantic region.
Ocean acidification
Increased concentrations of CO2 in sea water causing a measurable
increase in acidity (i.e., a reduction in ocean pH). This may
lead to reduced calcification rates of calcifying organisms such
as corals, molluscs, algae and crustacea.
Ombrotrophic bog
An acidic peat-accumulating wetland that is rainwater (instead
of groundwater) fed and thus particularly poor in nutrients.
Opportunity costs
The cost of an economic activity forgone through the choice of
another activity.
Ozone
The triatomic form of oxygen (O3), a gaseous atmospheric constituent.
In the troposphere, it is created both naturally and by
photochemical reactions involving gases resulting from human
activities (photochemical smog). In high concentrations, tropospheric
ozone can be harmful to many living organisms. Tropospheric
ozone acts as a greenhouse gas. In the stratosphere,
ozone is created by the interaction between solar ultraviolet radiation
and molecular oxygen (O2). Depletion of stratospheric
ozone, due to chemical reactions that may be enhanced by climate
change, results in an increased ground-level flux of ultraviolet
(UV) B radiation.
Paludification
he process of transforming land into a wetland such as a marsh,
a swamp or a bog.
Particulates
Very small solid exhaust particles emitted during the combustion
of fossil and biomass fuels. Particulates may consist of a wide
variety of substances. Of greatest concern for health are particulates
of less than or equal to 10 nm in diameter, usually designated
as PM10.
Peat
Peat is formed from dead plants, typically Sphagnum mosses,
which are only partially decomposed due to the permanent submergence
in water and the presence of conserving substances
such as humic acids.
Peatland
Typically a wetland such as a mire slowly accumulating peat.
Pelagic community
The community of organisms living in the open waters of a river,
a lake or an ocean (in contrast to benthic communities living on
or near the bottom of a water body).
Permafrost
Perennially frozen ground that occurs where the temperature remains
below 0°C for several years.
Phenology
The study of natural phenomena that recur periodically (e.g., development
stages, migration) and their relation to climate and
seasonal changes.
Photochemical smog
A mix of photochemical oxidant air pollutants produced by the
reaction of sunlight with primary air pollutants, especially hydrocarbons.
Photosynthesis
The synthesis by plants, algae and some bacteria of sugar from
sunlight, carbon dioxide and water, with oxygen as the waste
product. See also carbon dioxide fertilisation, C3 plants and C4
plants.
Physiographic
Of, relating to, or employing a description of nature or natural
phenomena.
Phytoplankton
The plant forms of plankton. Phytoplankton are the dominant
plants in the sea, and are the basis of the entire marine food web.
These single-celled organisms are the principal agents of photosynthetic
carbon fixation in the ocean. See also zooplankton.
Plankton
Microscopic aquatic organisms that drift or swim weakly. See
also phytoplankton and zooplankton.
Plant functional type (PFT)
An idealised vegetation class typically used in dynamic global
vegetation models (DGVM).
Polynya
Areas of permanently unfrozen sea water resulting from warmer
local water currents in otherwise sea-ice covered oceans. They
are biological hotspots, since they serve as breathing holes or
refuges for marine mammals such as whales and seals, and fishhunting
birds.
Population system
An ecological system (not ecosystem) determined by the dynamics
of a particular vagile species that typically cuts across
several ecological communities and even entire biomes. An example
is migratory birds that seasonally inhabit forests as well
as grasslands and visit wetlands on their migratory routes.
Appendix I: Glossary

Potential production
Estimated crop productivity under non-limiting soil, nutrient and
water conditions.
Pre-industrial
See industrial revolution.
Primary production
All forms of production accomplished by plants, also called primary
producers. See GPP, NPP, NEP and NBP.
Projection
The potential evolution of a quality or set of quantities, often
computed with the aid of a model. Projections are distinguished
from predictions in order to emphasise that projections involve
assumptions – concerning, for example, future socio-economic
and technological developments, that may or may not be realised
– and are therefore subject to substantial uncertainty. See also
climate projection and climate prediction.
Pteropods
Planktonic, small marine snails with swimming organs resembling
wings.
Pure rate of time preference
The degree to which consumption now is preferred to consumption
one year later, with prices and incomes held constant,
which is one component of the discount rate.
Radiative forcing
Radiative forcing is the change in the net vertical irradiance (expressed
inWatts per square metre;Wm−2) at the tropopause due
to an internal or external change in the forcing of the climate
system, such as a change in the concentration of CO2 or the output
of the Sun.
Rangeland
Unmanaged grasslands, shrublands, savannas and tundra.
Recalcitrant
Recalcitrant organic material or recalcitrant carbon stocks resist
decomposition.
Reference scenario
See baseline/reference.
Reforestation
Planting of forests on lands that have previously contained
forests but that have been converted to some other use. For a
discussion of the term forest and related terms such as afforestation,
reforestation and deforestation, see the IPCC Special
Report on Land Use, Land-Use Change, and Forestry (IPCC,
).
Reid’s paradox
This refers to the apparent contradiction between inferences of
high plant migration rates as suggested in the palaeo-record (particularly
after the last Ice Age), and the low potential rates of
migration that can be inferred through studying the seed dispersal
of the plants involved, e.g., in wind-tunnel experiments.
Reinsurance
The transfer of a portion of primary insurance risks to a secondary
tier of insurers (reinsurers); essentially ‘insurance for insurers’.
Relative sea-level rise
See sea-level rise.
Reservoir
A component of the climate system, other than the atmosphere,
that has the capacity to store, accumulate or release a substance
of concern (e.g., carbon or a greenhouse gas). Oceans, soils, and
forests are examples of carbon reservoirs. The term also means
an artificial or natural storage place for water, such as a lake,
pond or aquifer, from which the water may be withdrawn for
such purposes as irrigation or water supply.
Resilience
The ability of a social or ecological system to absorb disturbances
while retaining the same basic structure and ways of
functioning, the capacity for self-organisation, and the capacity
to adapt to stress and change.
Respiration
The process whereby living organisms convert organic matter
to carbon dioxide, releasing energy and consuming oxygen.
Riparian
Relating to or living or located on the bank of a natural watercourse
(such as a river) or sometimes of a lake or a tidewater.
River discharge
Water flow within a river channel, for example expressed in
m3/s. A synonym for streamflow.
Runoff
That part of precipitation that does not evaporate and is not transpired.
Salinisation
The accumulation of salts in soils.
Salt-water intrusion / encroachment
Displacement of fresh surface water or groundwater by the advance
of salt water due to its greater density. This usually occurs
in coastal and estuarine areas due to reducing land-based
influence (e.g., either from reduced runoff and associated
groundwater recharge, or from excessive water withdrawals
from aquifers) or increasing marine influence (e.g., relative sealevel
rise).
Savanna
Tropical or sub-tropical grassland or woodland biomes with scattered
shrubs, individual trees or a very open canopy of trees, all
characterised by a dry (arid, semi-arid or semi-humid) climate.
Appendix I: Glossary

Scenario
A plausible and often simplified description of how the future
may develop, based on a coherent and internally consistent set
of assumptions about driving forces and key relationships. Scenarios
may be derived from projections, but are often based on
additional information from other sources, sometimes combined
with a ‘narrative storyline’. See also climate (change) scenario,
emissions scenario and SRES.
Sea-ice biome
The biome formed by all marine organisms living within or on
the floating sea ice (frozen sea water) of the polar oceans.)
Sea-level rise
An increase in the mean level of the ocean. Eustatic sea-level
rise is a change in global average sea level brought about by an
increase in the volume of the world ocean. Relative sea-level
rise occurs where there is a local increase in the level of the
ocean relative to the land, which might be due to ocean rise
and/or land level subsidence. In areas subject to rapid land-level
uplift, relative sea level can fall.
Sea wall
A human-made wall or embankment along a shore to prevent
wave erosion.
Semi-arid regions
Regions of moderately low rainfall, which are not highly productive
and are usually classified as rangelands. ‘Moderately
low’ is widely accepted as between 100 and 250 mm precipitation
per year. See also arid region.
Sensitivity
Sensitivity is the degree to which a system is affected, either adversely
or beneficially, by climate variability or change. The effect
may be direct (e.g., a change in crop yield in response to a
change in the mean, range or variability of temperature) or indirect
(e.g., damages caused by an increase in the frequency of
coastal flooding due to sea-level rise).
Sequestration
See carbon sequestration.
Silviculture
Cultivation, development and care of forests.
Sink
Any process, activity, or mechanism that removes a greenhouse
gas, an aerosol, or a precursor of a greenhouse gas or aerosol
from the atmosphere.
Snow water equivalent
The equivalent volume/mass of water that would be produced if
a particular body of snow or ice was melted.
Snowpack
A seasonal accumulation of slow-melting snow.
Social cost of carbon
The value of the climate change impacts from 1 tonne of carbon
emitted today as CO2, aggregated over time and discounted
back to the present day; sometimes also expressed as value per
tonne of carbon dioxide.
Socio-economic scenarios
Scenarios concerning future conditions in terms of population,
Gross Domestic Product and other socio-economic factors relevant
to understanding the implications of climate change. See
SRES (source: Chapter 6).
SRES
The storylines and associated population, GDP and emissions
scenarios associated with the Special Report on Emissions Scenarios
(SRES) (Nakićenović et al., 2000), and the resulting climate
change and sea-level rise scenarios. Four families of
socio-economic scenario (A1, A2, B1 and B2) represent different
world futures in two distinct dimensions: a focus on economic
versus environmental concerns, and global versus
regional development patterns.
Stakeholder
A person or an organisation that has a legitimate interest in a
project or entity, or would be affected by a particular action or
policy.
Stock
See reservoir.
Stratosphere
Highly stratified region of atmosphere above the troposphere
extending from about 10 km (ranging from 9 km in high latitudes
to 16 km in the tropics) to about 50 km.
Streamflow
Water flow within a river channel, for example, expressed in
m3/s. A synonym for river discharge.
Sub-alpine
The biogeographic zone below the tree line and above the montane
zone that is characterised by the presence of coniferous forest
and trees.
Succulent
Succulent plants, e.g., cactuses, possessing organs that store
water, thus facilitating survival during drought conditions.
Surface runoff
The water that travels over the land surface to the nearest surface
stream; runoff of a drainage basin that has not passed beneath the
surface since precipitation.
Sustainable development
Development that meets the cultural, social, political and economic
needs of the present generation without compromising
the ability of future generations to meet their own needs.
Appendix I: Glossary

Taiga
The northernmost belt of boreal forest adjacent to theArctic tundra.
Thermal expansion
In connection with sea-level rise, this refers to the increase in
volume (and decrease in density) that results from warming
water. A warming of the ocean leads to an expansion of the
ocean volume and hence an increase in sea level.
Thermocline
The region in the world’s ocean, typically at a depth of 1 km,
where temperature decreases rapidly with depth and which
marks the boundary between the surface and the ocean.
Thermohaline circulation (THC)
Large-scale, density-driven circulation in the ocean, caused by
differences in temperature and salinity. In the NorthAtlantic, the
thermohaline circulation consists of warm surface water flowing
northward and cold deepwater flowing southward, resulting in a
net poleward transport of heat. The surface water sinks in highly
restricted regions located in high latitudes. Also called meridional
overturning circulation (MOC).
Thermokarst
Aragged landscape full of shallow pits, hummocks and depressions
often filled with water (ponds), which results from thawing
of ground ice or permafrost. Thermokarst processes are the
processes driven by warming that lead to the formation of
thermokarst.
Threshold
The level of magnitude of a system process at which sudden or
rapid change occurs. A point or level at which new properties
emerge in an ecological, economic or other system, invalidating
predictions based on mathematical relationships that apply at
lower levels.
Transpiration
The evaporation of water vapour from the surfaces of leaves
through stomata.
Tree line
The upper limit of tree growth in mountains or high latitudes. It
is more elevated or more poleward than the forest line.
Trophic level
The position that an organism occupies in a food chain.
Trophic relationship
The ecological relationship which results when one species feeds
on another.
Troposphere
The lowest part of the atmosphere from the surface to about
km in altitude in mid-latitudes (ranging from 9 km in high
latitudes to 16 km in the tropics on average) where clouds and
‘weather’ phenomena occur. In the troposphere, temperatures
generally decrease with height.
Tsunami
Alarge wave produced by a submarine earthquake, landslide or
volcanic eruption.
Tundra
Atreeless, level, or gently undulating plain characteristic of the
Arctic and sub-Arctic regions characterised by low temperatures
and short growing seasons.
Uncertainty
An expression of the degree to which a value (e.g., the future
state of the climate system) is unknown. Uncertainty can result
from lack of information or from disagreement about what is
known or even knowable. It may have many types of sources,
from quantifiable errors in the data to ambiguously defined concepts
or terminology, or uncertain projections of human behaviour.
Uncertainty can therefore be represented by quantitative
measures (e.g., a range of values calculated by various models)
or by qualitative statements (e.g., reflecting the judgement of a
team of experts). See also confidence and likelihood.
Undernutrition
The temporary or chronic state resulting from intake of lower
than recommended daily dietary energy and/or protein requirements,
through either insufficient food intake, poor absorption,
and/or poor biological use of nutrients consumed.
Ungulate
Ahoofed, typically herbivorous, quadruped mammal (including
ruminants, swine, camel, hippopotamus, horse, rhinoceros and
elephant).
United Nations Framework Convention on Climate
Change (UNFCCC)
The Convention was adopted on 9 May 1992, in New York, and
signed at the 1992 Earth Summit in Rio de Janeiro by more than
countries and the European Community. Its ultimate objective
is the ‘stabilisation of greenhouse gas concentrations in the
atmosphere at a level that would prevent dangerous anthropogenic
interference with the climate system’. It contains commitments
for all Parties. Under the Convention, Parties included
inAnnex I aim to return greenhouse gas emissions not controlled
by the Montreal Protocol to 1990 levels by the year 2000. The
Convention entered in force inMarch 1994. See also Kyoto Protocol.
Upwelling region
Aregion of an ocean where cold, typically nutrient-rich watersfrom
the bottom of the ocean surface.
Urbanisation
The conversion of land from a natural state or managed natural
state (such as agriculture) to cities; a process driven by net ruralto-
urban migration through which an increasing percentage of
the population in any nation or region come to live in settlements
that are defined as ‘urban centres’.
Appendix I: Glossary

Appendix I: Glossary

Vagile
Able to migrate.
Vascular plants
Higher plants with vascular, i.e., sap-transporting, tissues.
Vector
A blood-sucking organism, such as an insect, that transmits a
pathogen from one host to another. See also vector-borne diseases.
Vector-borne diseases
Disease that are transmitted between hosts by a vector organism
(such as a mosquito or tick); e.g., malaria, dengue fever and
leishmaniasis.
Vernalisation
The biological requirements of certain crops, such as winter cereals,
which need periods of extreme cold temperatures before
emergence and/or during early vegetative stages, in order to
flower and produce seeds. By extension, the act or process of
hastening the flowering and fruiting of plants by treating seeds,
bulbs or seedlings with cold temperatures, so as to induce a
shortening of the vegetative period.
Vulnerability
Vulnerability is the degree to which a system is susceptible to,
and unable to cope with, adverse effects of climate change, including
climate variability and extremes. Vulnerability is a function
of the character, magnitude, and rate of climate change and
variation to which a system is exposed, its sensitivity, and its
adaptive capacity.
Water consumption
Amount of extracted water irretrievably lost during its use (by
evaporation and goods production).Water consumption is equal
to water withdrawal minus return flow.
Water productivity
The ratio of crop seed produced per unit water applied. In the
case of irrigation, see irrigation water-use efficiency. For rainfed
crops, water productivity is typically 1 t/100 mm.
Water stress
A country is water-stressed if the available freshwater supply
relative to water withdrawals acts as an important constraint on
development. Withdrawals exceeding 20% of renewable water
supply have been used as an indicator of water stress. A crop is
water-stressed if soil-available water, and thus actual evapotranspiration,
is less than potential evapotranspiration demands.
Water-use efficiency
Carbon gain in photosynthesis per unit water lost in evapotranspiration.
It can be expressed on a short-term basis as the ratio
of photosynthetic carbon gain per unit transpirational water loss,
or on a seasonal basis as the ratio of net primary production or
agricultural yield to the amount of available water.
Welfare
An economic term used to describe the state of well-being of
humans on an individual or collective basis. The constituents of
well-being are commonly considered to include materials to satisfy
basic needs, freedom and choice, health, good social relations,
and security.
Wetland
A transitional, regularly waterlogged area of poorly drained
soils, often between an aquatic and a terrestrial ecosystem, fed
from rain, surface water or groundwater. Wetlands are characterised
by a prevalence of vegetation adapted for life in saturated
soil conditions.
Yedoma
Ancient organic material trapped in permafrost that is hardly decomposed.
Zoonoses
Diseases and infections which are naturally transmitted between
vertebrate animals and people.
Zooplankton
The animal forms of plankton. They consume phytoplankton or
other zooplankton.


[CO2] Concentration of carbon dioxide
AAO Antarctic Oscillation
ABM Agent-based models
AC Air-conditioning
ACIA Arctic Climate ImpactAssessment
AEJ African Easterly Jet
AEZ Agro-ecological zone
AGCM Atmospheric General Circulation Model
AGO Australian Greenhouse Office
AIACC Assessments of Impacts andAdaptations to
Climate Change in Multiple Regions and
Sectors
AIDS Acquired Immune Deficiency Syndrome
AO Arctic Oscillation
AOGCM Atmosphere-Ocean General Circulation
Model
APF Adaptation Policy Framework
AR4 FourthAssessment Report
Aus Australia
AVHRR Advanced Very High Resolution
Radiometer
BAU Business-as-usual scenario
BSATs Brazilian semi-arid tropics
CAA CanadianArctic archipelago
CAPRADE ComitéAndino para la Prevención y
Atención de Desastres (Andean Committee
for Disaster Prevention andAssistance)
CBA Cost-benefit analysis
CBD Convention on Biological Diversity
CC Climate change
CCAMLR Commission for the Conservation of
Antarctic Marine Living Resources
CCD (United Nations) Convention to Combat
Desertification
CCIAV Climate change impacts, adaptation and
vulnerability
CCN Cloud condensation nuclei
CDF Conditional damage function
CDM Clean Development Mechanism
CEE Central and Eastern Europe
CFP Common Fisheries Policy
CGE Computable general equilibrium (model)
CIESIN Center for International Earth Science
Information Network
CITES Convention on International Trade in
Endangered Species ofWild Flora and
Fauna
CMAQ Community multiscale air quality (model)
COP Conference of the Parties (to the
UNFCCC)
CPPS Comisión Permanente del Pacífico Sur
(Permanent Commission of the South
Pacific)
CRID Centro Regional de Información sobre
Desastres (Regional Disaster Information
Centre – LatinAmerica and the Caribbean)
CSIRO Commonwealth Scientific and Industrial
Research Organisation
DAC DevelopmentAssistance Committee
DAI Dangerous anthropogenic interference
DALY Disability adjusted life year
DDC Data Distribution Centre (of the IPCC)
Defra Department for Environment, Food and
RuralAffairs (of the UK Government)
DGVM Dynamic global vegetation model
DIC Dissolved inorganic carbon
DJF December, January, February
DMS Dimethyl sulphide
DOC Dissolved organic carbon
DPSIR Drivers-pressures-state-impacts-response
DWC Dialogue onWater and Climate
ECCP European Climate Change Programme
ECLAC Economic Commission for LatinAmerica
and the Caribbean
EF Ecological footprint
EIA Environmental ImpactAssessment
EMIC Earth-system model of intermediate
complexity
ENSO El Niño-Southern Oscillation
EPA Environmental ProtectionAgency
EPOC Environment Policy Committee
EPPA Anthropogenic emission prediction and
policy analysis
Appendix IV: Acronyms
EPPA-HHL The EPPAhigh-emissions scenario
EPPA-LLH The EPPAlow-emissions scenario
ET Evapotranspiration
EU European Union
EU15 The 15 countries in the European Union
before the expansion on 1 May 2004
EU25 The 25 countries in the European Union
after the expansion on 1 May 2004, but
prior to 1 January 2007
EWS Early-warning systems
FACE Free-air carbon dioxide enrichment
FAO Food andAgriculture Organization
FFF Food, fibre and forestry
FFFF Food, fibre, forestry and fishery
GBR Great Barrier Reef
GCM General Circulation Model
GDP Gross domestic product
GEF Global Environment Facility
GEOSS Global Earth Observation System of
Systems
GHG Greenhouse gas(es)
GIMMS Global Inventory Modeling and Mapping
Studies
GIS Geographic information system
GISS Goddard Institute for Space Studies
GLOF Glacial lake outburst flood
GMAT Global mean annual temperature
GMT Global mean temperature
GNP Gross national product
GPP Gross primary production
GPS Global Positioning System
GWP GlobalWater Partnership
HABs Harmful algal blooms
HANPP Human appropriation of net primary
productivity
HIV Human immunodeficiency virus
HPS Hantavirus pulmonary syndrome
HYV High-yield varieties
IAM Integrated assessment model
IAS Invasive alien species
ICLIPS IntegratedAssessment of Climate
Protection Strategies
ICM Integrated coastal management
ICZM Integrated coastal zone management
IFRCRC International Federation of Red Cross and
Red Crescent Societies
IGBP International Geosphere-Biosphere
Programme
IHDP International Human Dimensions
Programme
IIASA International Institute forApplied Systems
Analysis
INAP Integrated National PilotAdaptation Plan
IOCARIBE-GOOS Intergovernmental Oceanographic
Commission Regional Sub-Commission
for the Caribbean andAdjacent Regions
Global Ocean Observing System
IOD Indian Ocean Dipole
IPCC Intergovernmental Panel on Climate
Change
IPO Inter-decadal Pacific Oscillation
IRRI International Rice Research Institute
ITCZ Intertropical Convergence Zone
ITTO International Tropical Timber Organization
IUCN International Union for the Conservation of
Nature and Natural Resources (World
Conservation Union)
JFM January, February, March
JJA June, July,August
LA LatinAmerica
LAI Leaf-area index
LBA Large Scale Biosphere-Atmosphere
(experiment)
LDC Less/Least Developed Countries
LGA Local government authority (Chapter 11)
LGM Last Glacial Maximum
LGP Length of growing period
LIA Little IceAge
LPJ Lund-Potsdam-Jena (model)
LULUCF Land use, land-use change and forestry
M&E Monitoring and evaluation
MA Millennium EcosystemAssessment
MACC MainstreamingAdaptation to Climate
Change in the Caribbean
MAMJ March,April, May, June
MARA/ARMA Mapping Malaria Risk inAfrica/Atlas du
Risque de la Malaria enAfrique
MASL Metres above sea level
MDB Murray-Darling Basin
MDGs Millennium Development Goals
MEA Multilateral environmental agreement
MER Market exchange rates
MJO Madden-Julian Oscillation
MOC Meridional overturning circulation
MTE Mediterranean-type ecosystems
NAH NorthAtlantic Sub-tropical High
NAO NorthAtlantic Oscillation
NAPA NationalAdaptation Programme ofAction
NBP Net biome productivity
NC National Communication
NCAR PCM National Center forAtmospheric Research
Parallel Climate Model
NDVI Normalised Difference Vegetation Index
NEP Net ecosystem productivity
NEPAD New Partnership forAfrica’s Development
NGO Non-governmental organisation
Appendix IV: Acronyms

NHT Northern Hemisphere temperature
NPP Net primary productivity
NSW New SouthWales
NT Northern Territory
NTFP Non-timber forest products
NWMP NationalWater Management Plan
NZ New Zealand
ODA Official DevelopmentAssistance
OECD Organisation for Economic Co-operation
and Development
OND October, November, December
PAHO Pan-American Health Organization
PAL PathfinderAVHRR Land
PDF Probability density function
PDI Power dissipation index
PDO Pacific Decadal Oscillation
PDSI Palmer Drought Severity Index
P-E Precipitation-evaporation
PEAC Pacific ENSOApplications Center
PFT Plant functional types
PIA Participatory integrated assessment
PI-GCOS Pacific Islands Global Climate Observing
System
P-IND Pre-industrial
PM Particulate matter
ppb Parts per billion
ppm Parts per million
PPP Purchasing power parity
PRA Participatory rural appraisal
Qld Queensland
RCM Regional Climate Model
RRA Rapid rural appraisal
RSLR Relative sea-level rise
SACZ SouthAtlantic Convergence Zone
SAP Structural adjustment programme
SAS Storyline and simulation
SBW Spruce bud worm
SCAPE Soft Cliff and Platform Erosion (model)
SD Statistical downscaling
SDSM Statistical downscaling model
SEAFRAME Sea-level fine resolution acoustic
measuring equipment
SIDS Small Island Developing States
SLR Sea-level rise
SM Supplementary material
SoCAB South CoastAir Basin (California)
SON September, October, November
SPCZ South Pacific Convergence Zone
SRES Special Report on Emissions Scenarios
SST Sea surface temperature
SWE Snow water equivalent
TAR ThirdAssessment Report (of the IPCC)
TBE Tick-borne encephalitis
TEJ Tropical Easterly Jet
TEK Traditional ecological knowledge
TGICA Task Group on Data and Scenario Support
for Impact and ClimateAnalysis
THC Thermohaline circulation
TOGA Tropical Ocean-GlobalAtmosphere
TOPEX Ocean Topography Experiment
TWA Tolerable windows approach
UHI Urban heat-island
UK United Kingdom
UKCIP United Kingdom Climate Impacts
Programme
UNDP United Nations Development Programme
UNFCCC United Nations Framework Convention on
Climate Change
US United States (ofAmerica)
USEPA United States Environmental Protection
Agency
UVR Ultraviolet radiation
VBD Vector-borne disease
VOC Volatile organic compound
WA WesternAustralia
WAIS WestAntarctic ice sheet
WAMU WestAfrican Monetary Union
WBD Water-borne disease
WCRP World Climate Research Programme
WE Western Europe
WG Working Group (of the IPCC)
WHO World Health Organization
WMO World Meteorological Organization
WNV West Nile virus
WTO World Trade Organization
WWW WorldWeatherWatch
I Glossary, Acronyms, Chemical Symbols and Prefi xes Editors: Aviel Verbruggen (Belgium), William Moomaw (USA), John Nyboer (Canada) This annex should be cited as: Verbruggen, A., W. Moomaw, J. Nyboer, 2011: Annex I: Glossary, Acronyms, Chemical Symbols and Prefi xes. In IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation [O. Edenhofer, R. Pichs- Madruga, Y. Sokona, K. Seyboth, P. Matschoss, S. Kadner, T. Zwickel, P. Eickemeier, G. Hansen, S. Schlömer, C. von Stechow (eds)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. ANNEX

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I Glossary, Acronyms, Chemical Symbols and Prefi xes Glossary entries (highlighted in bold) are by preference subjects; a main entry can contain subentries, in bold italic, for example, Final Energy is defi ned under the entry Energy. The Glossary is followed by a list of acronyms/abbreviations, a list of chemical names and symbols, and a list of prefi xes (international standard units). Some defi nitions are adapted from C.J. Cleveland and C. Morris, 2006: Dictionary of Energy, Elsevier, Amsterdam. Defi nitions of regions and country groupings are given in Section A.II.6 of Annex II of this report. Glossary Adaptation: Initiatives and measures to reduce the vulnerability or increase the resilience of natural and human systems to actual or expected climate change impacts. Various types of adaptation exist, for example, anticipatory and reactive, private and public, and autonomous and planned. Examples are raising river or coastal dikes, retreating from coastal areas subject to fl ooding from sea level rise or introducing alternative temperature-appropriate or drought-adapted crops for conventional ones. Aerosols: A collection of airborne solid or liquid particles, typically between 0.01 and 10 μm in size and residing in the atmosphere for at least several hours. Aerosols may be of natural or anthropogenic origin. See also black carbon. Afforestation: Direct human-induced conversion of land that has not been forested historically to forested land through planting, seeding and/or the human-induced promotion of natural seed sources.1 See also deforestation, reforestation, land use. Annex I countries: The group of countries included in Annex I (as amended since Malta was added after that date) to the UNFCCC, including developed countries and some countries with economies in transition. Under Articles 4.2 (a) and 4.2 (b) of the Convention, Annex I countries were encouraged to return individually or jointly to their 1990 levels of greenhouse gas emissions by 2000. The group is largely similar to the Annex B countries to the Kyoto Protocol. By default, the other countries are referred to as Non-Annex I countries. See also UNFCCC, Kyoto Protocol. Annex B countries: This is the subset of Annex I countries that have specifi ed greenhouse gas reduction commitments under the Kyoto Protocol. The group is largely similar to the Annex I countries to the UNFCCC. By default, the other countries are referred to as Non-Annex I countries. See also UNFCCC, Kyoto Protocol. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see IPCC 2000: Land Use, Land-Use Change, and Forestry, A Special Report of the IPCC [R.T. Watson, I.A. Noble, B. Bolin, N.H. Ravindranath, D.J. Verardo, D.J. Dokken (eds.)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Anthropogenic: Related to or resulting from the infl uence of human beings on nature. Anthropogenic emissions of greenhouse gases, greenhouse gas precursors and aerosols result from burning fossil fuels, deforestation, land use changes, livestock, fertilization, industrial, commercial and other activities that result in a net increase in emissions. Availability (of a production plant): The percentage of time a plant is ready to produce, measured as uptime to total time (total time = uptime + downtime due to maintenance and outages). Balancing power/reserves: Due to instantaneous and short-term fl uctuations in electric loads and uncertain availability of power plants there is a constant need for spinning and quick-start generators that balance demand and supply at the imposed quality levels for frequency and voltage. Barrier: Any obstacle to developing and deploying a renewable energy (RE) potential that can be overcome or attenuated by a policy, programme or measure. Barriers to RE deployment are unintentional or intentionally constructed impediments made by man (e.g., badly oriented buildings or power grid access criteria that discriminate against independent RE generators). Distinct from barriers are issues like intrinsically natural properties impeding the application of some RE sources at some place or time (e.g., fl at land impedes hydropower and night the collection of direct solar energy). Barrier removal includes correcting market failures directly or reducing the transactions costs in the public and private sectors by, for example, improving institutional capacity, reducing risk and uncertainty, facilitating market transactions and enforcing regulatory policies. Baseline: The reference scenario for measurable quantities from which an alternative outcome can be measured, for example, a non-intervention scenario is used as a reference in the analysis of intervention scenarios. A baseline may be an extrapolation of recent trends, or it may assume frozen technology or costs. See also business as usual, models, scenario.

Benchmark: A measurable variable used as a baseline or reference in evaluating the performance of a technology, a system or an organization. Benchmarks may be drawn from internal experience, from external correspondences or from legal requirements and are often used to gauge changes in performance over time. Biodiversity: The variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, among species and of ecosystems. Bioenergy: Energy derived from any form of biomass. Biofuel: Any liquid, gaseous or solid fuel produced from biomass, for example, soybean oil, alcohol from fermented sugar, black liquor from the paper manufacturing process, wood as fuel, etc. Traditional biofuels include wood, dung, grass and agricultural residues. First-generation manufactured biofuel is derived from grains, oilseeds, animal fats and waste vegetable oils with mature conversion technologies. Second-generation biofuel uses non-traditional biochemical and thermochemical conversion processes and feedstock mostly derived from the lignocellulosic fractions of, for example, agricultural and forestry residues, municipal solid waste, etc. Third-generation biofuel would be derived from feedstocks like algae and energy crops by advanced processes still under development. These second- and third-generation biofuels produced through new processes are also referred to as next-generation or advanced biofuels or advanced biofuel technologies. Biomass: Material of biological origin (plants or animal matter), excluding material embedded in geological formations and transformed to fossil fuels or peat. The International Energy Agency (World Energy Outlook 2010) defi nes traditional biomass as biomass consumption in the residential sector in developing countries that refers to the often unsustainable use of wood, charcoal, agricultural residues and animal dung for cooking and heating. All other biomass use is defi ned as modern biomass, differentiated further by this report into two groups. Modern bioenergy encompasses electricity generation and combined heat and power (CHP) from biomass and municipal solid waste (MSW), biogas, residential space and hot water in buildings and commercial applications from biomass, MSW, and biogas, and liquid transport fuels. Industrial bioenergy applications include heating through steam generation and self generation of electricity and CHP in the pulp and paper industry, forest products, food and related industries. Black carbon: Operationally defi ned aerosol species based on measurement of light absorption and chemical reactivity and/or thermal stability; consists of soot, charcoal and/or light-absorbing refractory organic matter. Business as usual (BAU): The future is projected or predicted on the assumption that operating conditions and applied policies remain what they are at present. See also baseline, models, scenario. Capacity: In general, the facility to produce, perform, deploy or contain. Generation capacity of a renewable energy installation is the maximum power, that is, the maximum quantity of energy delivered per unit of time. Capacity credit is the share of the capacity of a renewable energy unit counted as guaranteed available during particular time periods and accepted as a ‘fi rm’ contribution to total system generation capacity. Capacity factor is the ratio of the actual output of a generating unit over a period of time (typically a year) to the theoretical output that would be produced if the unit were operating uninterruptedly at its nameplate capacity during the same period of time. Also known as rated capacity or nominal capacity, nameplate capacity is the facility’s intended output level for a sustained period under normal circumstances. Capacity building: In the context of climate change policies, the development of technical skills and institutional capability (the art of doing) and capacity (suffi cient means) of countries to enable their participation in all aspects of adaptation to, mitigation of and research on climate change. See also mitigation capacity. Carbon cycle: Describes the fl ow of carbon (in various forms, e.g., carbon dioxide, methane, etc) through the atmosphere, oceans, terrestrial biosphere and lithosphere. Carbon dioxide (CO2): CO2 is a naturally occurring gas and a by-product of burning fossil fuels or biomass, of land use changes and of industrial processes. It is the principal anthropogenic greenhouse gas that affects Earth’s radiative balance. It is the reference gas against which other greenhouse gases are measured and therefore it has a global warming potential of 1. Carbon dioxide capture and storage (CCS): CO2 from industrial and energy-related sources is separated, compressed and transported to a storage location for long-term isolation from the atmosphere. Cellulose: The principal chemical constituent of the cell walls of plants and the source of fi brous materials for the manufacturing of various

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I goods like paper, rayon, cellophane, etc. It is the main input for manufacturing second-generation biofuels. Clean Development Mechanism (CDM): A mechanism under the Kyoto Protocol through which developed (Annex B) countries may fi nance greenhouse gas emission reduction or removal projects in developing (Non-Annex B) countries, and receive credits for doing so which they may apply for meeting mandatory limits on their own emissions. Climate Change: Climate change refers to a change in the state of the climate that can be identifi ed (e.g. using statistical tests) by changes in the mean and/or the variability of these properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use. Note that Article 1 of the UNFCCC defi nes ‘climate change’ as “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”. The UNFCCC thus makes a distinction between ‘climate change’ attributable to human activities altering atmospheric composition, and ‘climate variability’ attributable to natural causes. CO2-equivalent emission (CO2eq): The amount of CO2 emission that would cause the same radiative forcing as an emitted amount of a greenhouse gas or of a mixture of greenhouse gases, all multiplied by their respective global warming potentials, which take into account the differing times they remain in the atmosphere. See also global warming potential. Co-benefi ts: The ancillary benefi ts of targeted policies that accrue to non-targeted, valuable objectives, for example, a wider use of renewable energy may also reduce air pollutants while lowering CO2 emissions. Different defi nitions exist in the literature with co-benefi ts either being addressed intentionally (character of an opportunity) or gained unintentionally (character of a windfall profi t). The term co-impact is more generic in covering both benefi ts and costs. See also drivers and opportunities. Cogeneration: At thermal electricity generation plants otherwise wasted heat is utilized. The heat from steam turbines or hot fl ue gases exhausted from gas turbines may be used for industrial purposes, heating water or buildings or for district heating. Also referred to as combined heat and power (CHP). Combined-cycle gas turbine (CCGT): A power plant that combines two processes for generating electricity. First, gas or light fuel oil feeds a gas turbine that exhausts hot fl ue gases (> 600°C). Second, heat recovered from these gases, with additional fi ring, is the source for producing steam that drives a steam turbine. The turbines rotate separate alternators. It becomes an integrated CCGT when the fuel is syngas from a coal or biomass gasifi cation reactor with exchange of energy fl ows between the gasifi cation and CCGT plants. Compliance: Compliance is whether and to what extent countries adhere to the provisions of an accord or individuals or fi rms adhere to regulations. Compliance depends on implementing policies ordered, and on whether measures follow up the policies. Conversion: Energy shows itself in numerous ways, with transformations from one type to another called energy conversions. For example, kinetic energy in wind fl ows is captured as rotating shaft work further converted to electricity; solar light is converted into electricity by photovoltaic cells. Also, electric currents of given characteristics (e.g., direct/ alternating, voltage level) are converted to currents with other characteristics. A converter is the equipment used to realize the conversion. Cost: The consumption of resources such as labour time, capital, materials, fuels, etc. as the consequence of an action. In economics, all resources are valued at their opportunity cost, which is the value of the most valuable alternative use of the resources. Costs are defi ned in a variety of ways and under a variety of assumptions that affect their value. The negative of costs are benefi ts and often both are considered together, for example, net cost is the difference between gross costs and benefi ts. Private costs are carried by individuals, companies or other entities that undertake the action. Social costs include additionally the external costs for the environment and for society as a whole, for example, damage costs of impacts on ecosystems, economies and people due to climate change. Total cost includes all costs due to a specifi c activity; average (unit, specifi c) cost is total costs divided by the number of units generated; marginal or incremental cost is the cost of the last additional unit. Project costs of a renewable energy project include investment cost (costs, discounted to the starting year of the project, of making the renewable energy device ready to commence production); operation and maintenance (O&M) costs (which occur during operation of the renewable energy facility); and decommissioning costs (which occur once the device has ceased production to restore the state of the site of production). Lifecycle costs include all of the above discounted to the starting year of a project. Levelized cost of energy (see Annex II) is the unique cost price of the outputs (US cent/kWh or USD/GJ) of a project that makes the

present value of the revenues (benefi ts) equal to the present value of the costs over the lifetime of the project. See also discounting and present value. There are many more categories of costs labelled with names that are often unclear and confusing, for example, installation costs may refer to the hardware equipment installed, or to the activities to put the equipment in place. Cost–benefi t analysis: Monetary measurement of all negative and positive impacts associated with a given action. Costs and benefi ts are compared in terms of their difference and/or ratio as an indicator of how a given investment or other policy effort pays off seen from the society’s point of view. Cost-effectiveness analysis: A reduction of cost–benefi t analysis in which all the costs of a portfolio of projects are assessed in relation to a fi xed policy goal. The policy goal in this case represents the benefi ts of the projects and all the other impacts are measured as costs or as negative costs (benefi ts). The policy goal can be, for example, realizing particular renewable energy potentials. Deforestation: The natural or anthropogenic process that converts forest land to non-forest. See also afforestation, reforestation and land use. Demand-side management: Policies and programmes for infl uencing the demand for goods and/or services. In the energy sector, demandside management aims at reducing the demand for electricity and other forms of energy required to deliver energy services. Density: Quantity or mass per unit volume, unit area or unit length. Energy density is the amount of energy per unit volume or mass (for example, the heating value of a litre of oil). Power density is typically understood as the capacity deliverable of solar, wind, biomass, hydropower or ocean power per unit area (watts/m2). For batteries the capacity per unit weight (watts/kg) is used. Direct solar energy - See solar energy Discounting: A mathematical operation making monetary (or other) amounts received or expended at different points in time (years) comparable across time (see Annex II). The operator uses a fi xed or possibly time-varying discount rate (>0) from year to year that makes future value worth less today. A descriptive discounting approach accepts the discount rates that people (savers and investors) actually apply in their day-to-day decisions (private discount rate). In a prescriptive (ethical or normative) discounting approach, the discount rate is fi xed from a social perspective, for example, based on an ethical judgement about the interests of future generations (social discount rate). In this report, potentials of renewable energy supplies are assessed using discount rates of 3, 7 and 10%. Dispatch (power dispatching / dispatchable): Electrical power systems that consist of many power supply units and grids are governed by system operators. They allow generators to supply power to the system for balancing demand and supply in a reliable and economical way. Generation units are fully dispatchable when they can be loaded from zero to their nameplate capacity without signifi cant delay. Not fully dispatchable are variable renewable sources that depend on natural currents, but also large-scale thermal plants with shallow ramping rates in changing their output. See also balancing, capacity, grid. District heating (DH): Hot water (steam in old systems) is distributed from central stations to buildings and industries in a densely occupied area (a district, a city or an industrialized area). The insulated two-pipe network functions like a water-based central heating system in a building. The central heat sources can be waste heat recovery from industrial processes, waste incineration plants, geothermal sources, cogeneration power plants or stand-alone boilers burning fossil fuels or biomass. More and more DH systems also provide cooling via cold water or slurries (district heating and cooling - DHC). Drivers: In a policy context, drivers provide an impetus and direction for initiating and supporting policy actions. The deployment of renewable energy is, for example, driven by concerns about climate change or energy security. In a more general sense, a driver is the leverage to bring about a reaction, for example, emissions are caused by fossil fuel consumption and/or economic growth. See also opportunities. Economies of scale (scale economies): The unit cost of an activity declines when the activity is extended, for example, more units are produced. Ecosystem: An open system of living organisms, interacting with each other and with their abiotic environment, that is capable of selfregulation to a certain degree. Depending on the focus of interest or study the extent of an ecosystem may range from very small spatial scales to the entire planet. Electricity: The fl ow of passing charge through a conductor, driven by a difference in voltage between the ends of the conductor. Electrical power is generated by work from heat in a gas or steam turbine or from wind, oceans or falling water, or produced directly from sunlight using a photovoltaic device or chemically in a fuel cell. Being a current, electricity cannot be stored and requires wires and cables for its transmission (see grid). Because electric current fl ows immediately, the demand for electricity must be matched by production in real time. Emissions: Dir ect emissions are released and attributed at points in a specifi c renewable energy chain, whether a sector, a technology or an activity. For example, methane emissions from decomposing submerged

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I organic materials in hydropower reservoirs, or the release of CO2 dissolved in hot water from geothermal plants, or CO2 from biomass combustion. Indirect emissions are due to activities outside the considered renewable energy chain but which are required to realize the renewable energy deployment. For example, emissions from increased production of fertilizers used in the cultivation of biofuel crops or emissions from displaced crop production or deforestation as the result of biofuel crops. Avoided emissions are emission reductions arising from mitigation measures like renewable energy deployment. Emission factor: An emission factor is the rate of emission per unit of activity, output or input. Emissions trading: A market-based instrument to reduce greenhouse gas or other emissions. The environmental objective or sum of total allowed emissions is expressed as an emissions cap. The cap is divided in tradable emission permits that are allocated—either by auctioning or handing out for free (grandfathering)—to entities within the jurisdiction of the trading scheme. Entities need to surrender emission permits equal to the amount of their emissions (e.g., tonnes of CO2 ). An entity may sell excess permits. Trading schemes may occur at the intra-company, domestic or international level and may apply to CO2 , other greenhouse gases or other substances. Emissions trading is also one of the mechanisms under the Kyoto Protocol. Energy: The amount of work or heat delivered. Energy is classifi ed in a variety of types and becomes available to human ends when it fl ows from one place to another or is converted from one type into another. Daily, the sun supplies large fl ows of radiation energy. Part of that energy is used directly, while part undergoes several conversions creating water evaporation, winds, etc. Some share is stored in biomass or rivers that can be harvested. Some share is directly usable such as daylight, ventilation or ambient heat. Primary energy (also referred to as energy sources) is the energy embodied in natural resources (e.g., coal, crude oil, natural gas, uranium, and renewable sources). It is defi ned in several alternative ways. The International Energy Agency utilizes the physical energy content method, which defi nes primary energy as energy that has not undergone any anthropogenic conversion. The method used in this report is the direct equivalent method (see Annex II), which counts one unit of secondary energy provided from non-combustible sources as one unit of primary energy, but treats combustion energy as the energy potential contained in fuels prior to treatment or combustion. Primary energy is transformed into secondary energy by cleaning (natural gas), refi ning (crude oil to oil products) or by conversion into electricity or heat. When the secondary energy is delivered at the end-use facilities it is called fi nal energy (e.g., electricity at the wall outlet), where it becomes usable energy in supplying services (e.g., light). Embodied energy is the energy used to produce a material substance (such as processed metals or building materials), taking into account energy used at the manufacturing facility (zero order), energy used in producing the materials that are used in the manufacturing facility (fi rst order), and so on. Renewable energy (RE) is any form of energy from solar, geophysical or biological sources that is replenished by natural processes at a rate that equals or exceeds its rate of use. Renewable energy is obtained from the continuing or repetitive fl ows of energy occurring in the natural environment and includes low-carbon technologies such as solar energy, hydropower, wind, tide and waves and ocean thermal energy, as well as renewable fuels such as biomass. For a more detailed description see specifi c renewable energy types in this glossary, for example, biomass, solar, hydropower, ocean, geothermal and wind. Energy access: People are provided the ability to benefi t from affordable, clean and reliable energy services for basic human needs (cooking and heating, lighting, communication, mobility) and productive uses. Energy carrier: A substance for delivering mechanical work or transfer of heat. Examples of energy carriers include: solid, liquid or gaseous fuels (e.g., biomass, coal, oil, natural gas, hydrogen); pressurized/heated/ cooled fl uids (air, water, steam); and electric current. Energy effi ciency: The ratio of useful energy or other useful physical outputs obtained from a system, conversion process, transmission or storage activity to the input of energy (measured as kWh/kWh, tonnes/ kWh or any other physical measure of useful output like tonne-km transported, etc.). Energy effi ciency is a component of energy intensity. Energy intensity: The ratio of energy inputs (in Joules) to the economic output (in dollars) that absorbed the energy input. Energy intensity is the reciprocal of energy productivity. At the national level, energy intensity is the ratio of total domestic primary (or fi nal) energy use to gross domestic product (GDP). The energy intensity of an economy is the weighted sum of the energy intensities of particular activities with the activities’ shares in GDP as weights. Energy intensities are obtained from available statistics (International Energy Agency, International Monetary Fund) and published annually for most countries in the world. Energy intensity is also used as a name for the ratio of energy inputs to output or performance in physical terms (e.g., tonnes of steel output, tonne-km transported, etc.) and in such cases, is the reciprocal of energy effi ciency. Energy productivity: The reciprocal of energy intensity. Energy savings: Decreasing energy intensity by changing the activities that demand energy inputs. Energy savings can be realized by technical,

organizational, institutional and structural actions and by changed behaviour. Energy security: The goal of a given country, or the global community as a whole, to maintain an adequate energy supply. Measures encompass safeguarding access to energy resources; enabling development and deployment of technologies; building suffi cient infrastructure to generate, store and transmit energy supplies; ensuring enforceable contracts of delivery; and access to energy at affordable prices for a specifi c society or groups in society. Energy services: Energy services are the tasks to be performed using energy. A specifi c energy service such as lighting may be supplied by a number of different means from daylighting to oil lamps to incandescent, fl uorescent or light-emitting diode devices. The amount of energy used to provide a service may vary over a factor of 10 or more, and the corresponding greenhouse gas emissions may vary from zero to a very high value depending on the source of energy and the type of end-use device. Energy transfer: Energy is transferred as work, light or heat. Heat transfer spontaneously occurs from objects at higher temperature to objects at lower temperature and is classifi ed as conduction (when the objects have contact), convection (when a fl uid like air or water takes the heat from the warmer object and is moved to the colder object to deliver the heat) and radiation (when heat travels through space in the form of electromagnetic waves). Externality / external cost / external benefi t: Externalities arise from a human activity, when agents responsible for the activity do not take full account of the activity’s impact on others’ production and consumption possibilities, and no compensation exists for such impacts. When the impact is negative, they are external costs. When positive they are referred to as external benefi ts. Feed-in tariff: The price per unit of electricity that a utility or power supplier has to pay for distributed or renewable electricity fed into the grid by non-utility generators. A public authority regulates the tariff. There may also be a tariff for supporting renewable heat supplies. Financing: Raising or providing money or capital by individuals, businesses, banks, venture funds, public instances, etc. for realizing a project or continuing an activity. Depending on the fi nancier the money is raised and is provided differently. For example, businesses may raise money from internal company profi ts, debt or equity (shares). Project fi nancing of renewable energy may be provided by fi nanciers to distinct, single-purpose companies, whose renewable energy sales are usually guaranteed by power purchase agreements. Non-recourse fi nancing is known as off-balance sheet since the fi nanciers rely on the certainty of project cash fl ows to pay back the loan, not on the creditworthiness of the project developer. Public equity fi nancing is capital provided for publicly listed companies. Private equity fi nancing is capital provided directly to private companies. Corporate fi nancing by banks via debt obligations uses ‘onbalance sheet’ assets as collateral and is therefore limited by the debt ratio of companies that must rationalize each additional loan with other capital needs. Fiscal incentive: Actors (individuals, households, companies) are granted a reduction of their contribution to the public treasury via income or other taxes. Fuel cell: A fuel cell generates electricity in a direct and continuous way from the controlled electrochemical reaction of hydrogen or another fuel and oxygen. With hydrogen as fuel it emits only water and heat (no CO2) and the heat can be utilized (see cogeneration). General equilibrium models: General equilibrium models consider simultaneously all the markets and feedback effects among them in an economy leading to market clearance. Generation control: Generation of electricity at a renewable energy plant may be subject to various controls. Active control is a deliberate intervention in the functioning of a system (for example, wind turbine pitch control: changing the orientation of the blades for varying a wind turbine’s output). Passive control is when natural forces adjust the functioning of a system (for example, wind turbine stall control: the design of the blade shape such that at a desired speed the blade spills the wind in order to automatically control the wind turbine’s output). Geothermal energy: Accessible thermal energy stored in the Earth’s interior, in both rock and trapped steam or liquid water (hydrothermal resources), which may be used to generate electric energy in a thermal power plant, or to supply heat to any process requiring it. The main sources of geothermal energy are the residual energy available from planet formation and the energy continuously generated from radionuclide decay. Geothermal gradient: Rate at which the Earth’s temperature increases with depth, indicating heat fl owing from the Earth’s warm interior to its colder parts. Global warming potential (GWP): GWP is an index, based upon radiative properties of well-mixed greenhouse gases, measuring the radiative forcing of a unit mass of a given well-mixed greenhouse gas in today’s atmosphere integrated over a chosen time horizon, relative

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I to that of CO2. The GWP represents the combined effect of the differing lengths of time that these gases remain in the atmosphere and their relative effectiveness in absorbing outgoing infrared radiation. The Kyoto Protocol ranks greenhouse gases on the basis of GWPs from single pulse emissions over subsequent 100-year time frames. See also climate change and CO2- equivalent emission. Governance: Governance is a comprehensive and inclusive concept of the full range of means for deciding, managing and implementing policies and measures. Whereas government is defi ned strictly in terms of the nation-state, the more inclusive concept of governance, recognizes the contributions of various levels of government (global, international, regional, local) and the contributing roles of the private sector, of nongovernmental actors and of civil society to addressing the many types of issues facing the global community. Greenhouse gases (GHGs): Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specifi c wavelengths within the spectrum of thermal infrared radiation emitted by the Earth’s surface, the atmosphere and clouds. This property causes the greenhouse effect. Water vapour (H2O), carbon dioxide (CO2 ), nitrous oxide (N2O), methane (CH4 ) and ozone (O3) are the primary greenhouse gases in the Earth’s atmosphere. Moreover, there are a number of entirely human-made greenhouse gases in the atmosphere, such as the halocarbons and other chlorine- and bromine-containing substances, dealt with under the Montreal Protocol. Besides CO2 , N2O and CH4 , the Kyoto Protocol deals with the greenhouse gases sulphur hexafl uoride (SF6 ), hydrofl uorocarbons (HFCs) and perfl uorocarbons (PFCs). Grid (electric grid, electricity grid, power grid): A network consisting of wires, switches and transformers to transmit electricity from power sources to power users. A large network is layered from low-voltage (110-240 V) distribution, over intermediate voltage (1-50 kV) to high-voltage (above 50 kV to MV) transport subsystems. Interconnected grids cover large areas up to continents. The grid is a power exchange platform enhancing supply reliability and economies of scale. Grid connection for a power producer is mostly crucial for economical operation. Grid codes are technical conditions for equipment and operation that a power producer must obey for getting supply access to the grid; also consumer connections must respect technical rules. Grid access refers to the acceptance of power producers to deliver to the grid. Grid integration accommodates power production from a portfolio of diverse and some variable generation sources in a balanced power system. See also transmission and distribution. Gross Domestic Product (GDP): The sum of gross value added, at purchasers’ prices, by all resident and non-resident producers in the economy, plus any taxes and minus any subsidies not included in the value of the products in a country or a geographic region for a given period, normally one year. It is calculated without deducting for depreciation of fabricated assets or depletion and degradation of natural resources. Heat exchanger: Devices for effi cient heat transfer from one medium to another without mixing the hot and cold fl ows, for example, radiators, boilers, steam generators, condensers. Heat pump: Installation that transfers heat from a colder to a hotter place, opposite to the natural direction of heat fl ows (see energy transfer). Technically similar to a refrigerator, heat pumps are used to extract heat from ambient environments like the ground (geothermal or ground source), water or air. Heat pumps can be inverted to provide cooling in summer. Human Development Index (HDI): The HDI allows the assessment of countries’ progress regarding social and economic development as a composite index of three indicators: 1) health measured by life expectancy at birth; 2) knowledge as measured by a combination of the adult literacy rate and the combined primary, secondary and tertiary school enrolment ratio; and 3) standard of living as gross domestic product per capita (in purchasing power parity). The HDI only acts as a broad proxy for some of the key issues of human development; for instance, it does not refl ect issues such as political participation or gender inequalities. Hybrid vehicle: Any vehicle that employs two sources of propulsion, most commonly a vehicle that combines an internal combustion engine with an electric motor and storage batteries. Hydropower: The energy of water moving from higher to lower elevations that is converted into mechanical energy through a turbine or other device that is either used directly for mechanical work or more commonly to operate a generator that produces electricity. The term is also used to describe the kinetic energy of stream fl ow that may also be converted into mechanical energy of a generator through an in-stream turbine to produce electricity. Informal sector/economy: The informal sector/economy is broadly characterized as comprising production units that operate at a small scale and at a low level of organization, with little or no division between labour and capital as factors of production, and with the primary objective of generating income and employment for the persons concerned. The economic activity of the informal sector is not accounted for in determining sectoral or national economic activity. Institution: A structure, a mechanism of social order or cooperation, which governs the behaviour of a group of individuals within a human

community. Institutions are intended to be functionally relevant for an extended period, able to help transcend individual interests and help govern cooperative human behaviour. The term can be extended to also cover regulations, technology standards, certifi cation and the like. Integrated assessment: A method of analysis that combines results and models from the physical, biological, economic and social sciences, and the interactions between these components in a consistent framework to evaluate the status and the consequences of environmental change and the policy responses to it. See also models. Kyoto Protocol: The Kyoto Protocol to the UNFCCC was adopted at the Third Session of the Conference of the Parties in 1997 in Kyoto. It contains legally binding commitments, in addition to those included in the UNFCCC. Annex B countries agreed to reduce their anthropogenic greenhouse gas emissions (CO2, methane, nitrous oxide, hydrofl uorocarbons, perfl uorocarbons and sulphur hexafl uoride) by at least 5% below levels in the commitment period 2008 to 2012. The Kyoto Protocol came into force on 16 February 2005. See also UNFCCC. Land use (change; direct and indirect): The total of arrangements, activities and inputs undertaken in a certain land cover type. The social and economic purposes for which land is managed (e.g., grazing, timber extraction and conservation). Land use change occurs whenever land is transformed from one use to another, for example, from forest to agricultural land or to urban areas. Since different land types have different carbon storage potential (e.g., higher for forests than for agricultural or urban areas), land use changes may lead to net emissions or to carbon uptake. Indirect land use change refers to market-mediated or policydriven shifts in land use that cannot be directly attributed to land use management decisions of individuals or groups. For example, if agricultural land is diverted to fuel production, forest clearance may occur elsewhere to replace the former agricultural production. See also afforestation, deforestation and reforestation. Landfi ll: A solid waste disposal site where waste is deposited below, at or above ground level. Limited to engineered sites with cover materials, controlled placement of waste and management of liquids and gases. It excludes uncontrolled waste disposal. Landfi lls often release methane, CO2 and other gases as organic materials decay. Leapfrogging: The ability of developing countries to bypass intermediate technologies and jump straight to advanced clean technologies. Leapfrogging can enable developing countries to move to a low-emissions development trajectory. Learning curve / rate: Decreasing cost-prices of renewable energy supplies shown as a function of increasing (total or yearly) supplies. Learning improves technologies and processes over time due to experience, as production increases and/or with increasing research and development. The learning rate is the percent decrease of the cost-price for every doubling of the cumulative supplies (also called progress ratio). Levelized cost of energy – See Cost. Lifecycle analysis (LCA): LCA aims to compare the full range of environmental damages of any given product, technology, or service (see Annex II). LCA usually includes raw material input, energy requirements, and waste and emissions production. This includes operation of the technology/facility/ product as well as all upstream processes (i.e., those occurring prior to when the technology/facility/product commences operation) and downstream processes (i.e., those occurring after the useful lifetime of the technology/ facility/product), as in the ‘cradle to grave’ approach. Load (electrical): The demand for electricity by (thousands to millions) power users at the same moment aggregated and raised by the losses in transport and delivery, and to be supplied by the integrated power supply system. Load levelling reduces the amplitude of the load fl uctuations over time. Load shedding occurs when available generation or transmission capacity is insuffi cient to meet the aggregated loads. Peak load is the maximum load observed over a given period of time (day, week, year) and of short duration. Base load is power continuously demanded over the period. Loans: Loans are money that public or private lenders provide to borrowers mandated to pay back the nominal sum increased with interest payments. Soft loans (also called soft fi nancing or concessional funding) offer fl exible or lenient terms for repayment, usually at lower than market interest rates or no interest. Soft loans are provided customarily by government agencies and not by fi nancial institutions. Convertible loans entitle the lender to convert the loan to common or preferred stock (ordinary or preference shares) at a specifi ed conversion rate and within a specifi ed time frame. Lock-in: Technologies that cover large market shares continue to be used due to factors such as sunk investment costs, related infrastructure development, use of complementary technologies and associated social and institutional habits and structures. Carbon lock-in means that the established technologies and practices are carbon intensive.

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I Low-carbon technology: A technology that over its lifecycle causes very low to zero CO2eq emissions. See emissions. Market failure: When private decisions are based on market prices that do not refl ect the real scarcity of goods and services, they do not generate an effi cient allocation of resources but cause welfare losses. Factors causing market prices to deviate from real economic scarcity are environmental externalities, public goods and monopoly power. Measures: In climate policy, measures are technologies, processes or practices that reduce greenhouse gas emissions or impacts below anticipated future levels, for example renewable energy technologies, waste minimization processes, public transport commuting practices, etc. See also policies. Merit order (of power plants): Ranking of all available power generating units in an integrated power system, being the sequence of their short-run marginal cost per kWh starting with the cheapest for delivering electricity to the grid. Millennium Development Goals (MDG): A set of eight time-bound and measurable goals for combating poverty, hunger, disease, illiteracy, discrimination against women and environmental degradation. These were agreed to at the UN Millennium Summit in 2000 together with an action plan to reach these goals. Mitigation: Technological change and changes in activities that reduce resource inputs and emissions per unit of output. Although several social, economic and technological policies would produce an emission reduction, with respect to climate change, mitigation means implementing policies to reduce greenhouse gas emissions and enhance sinks. Renewable energy deployment is a mitigation option when avoided greenhouse gas emissions exceed the sum of direct and indirect emissions (see emissions). Mitigation capacity is a country’s ability to reduce anthropogenic greenhouse gas emissions or to enhance natural sinks, where ability refers to skills, competencies, fi tness and profi ciencies that a country has attained and depends on technology, institutions, wealth, equity, infrastructure and information. Mitigation capacity is rooted in a country’s sustainable development path. Models: Models are structured imitations of a system’s attributes and mechanisms to mimic appearance or functioning of systems, for example, the climate, the economy of a country, or a crop. Mathematical models assemble (many) variables and relations (often in a computer code) to simulate system functioning and performance for variations in parameters and inputs. Bottom-up models aggregate technological, engineering and cost details of specifi c activities and processes. Top-down models apply macroeconomic theory, econometric and optimization techniques to aggregate economic variables, like total consumption, prices, incomes and factor costs. Hybrid models integrate bottom-up and top-down models to some degree. Non-Annex I countries – See Annex I countries. Non-Annex B countries – See Annex B countries. Ocean energy: Energy obtained from the ocean via waves, tidal ranges, tidal and ocean currents, and thermal and saline gradients (note: submarine geothermal energy is covered under geothermal energy and marine biomass is covered under biomass energy). Offset (in climate policy): A unit of CO2-equivalent (CO2eq) that is reduced, avoided or sequestered to compensate for emissions occurring elsewhere. Opportunities: In general: conditions that allow for advancement, progress or profi t. In the policy context, circumstances for action with the attribute of a chance character. For example, the anticipation of additional benefi ts that may go along with the deployment of renewable energy (enhanced energy access and energy security, reduced local air pollution) but are not intentionally targeted. See also co-benefi ts and drivers. Path dependence: Outcomes of a process are conditioned by previous decisions, events and outcomes, rather than only by current actions. Choices based on transitory conditions can exert a persistent impact long after those conditions have changed. Payback: Mostly used in investment appraisal as fi nancial payback, which is the time needed to repay the initial investment by the returns of a project. A payback gap exists when, for example, private investors and micro-fi nancing schemes require higher profi tability rates from renewable energy projects than from fossil-fi red ones. Imposing an x-times higher fi nancial return on renewable energy investments is equivalent to imposing an x-times higher technical performance hurdle on delivery by novel renewable solutions compared to incumbent energy expansion. Energy payback is the time an energy project needs to deliver as much energy as had been used for setting the project online. Carbon payback is the time a renewable energy project needs to deliver as much net greenhouse gas savings (with respect to the fossil reference energy system) as its realization has caused greenhouse gas emissions from a perspective of lifecycle analysis (including land use changes and loss of terrestrial carbon stocks). Photosynthesis: The production of carbohydrates in plants, algae and some bacteria using the energy of light. CO2 is used as the carbon source.

Photovoltaics (PV): The technology of converting light energy directly into electricity by mobilizing electrons in solid state devices. The specially prepared thin sheet semiconductors are called PV cells. See solar energy. Policies: Policies are taken and/or mandated by a government—often in conjunction with business and industry within a single country, or collectively with other countries—to accelerate mitigation and adaptation measures. Examples of policies are support mechanisms for renewable energy supplies, carbon or energy taxes, fuel effi ciency standards for automobiles, etc. Common and co-ordinated or harmonized policies refer to those adopted jointly by parties. See also measures. Policy criteria: General: a standard on which a judgment or decision may be based. In the context of policies and policy instruments to support renewable energy, four inclusive criteria are common: Effectiveness (effi cacy) is the extent to which intended objectives are met, for instance the actual increase in the output of renewable electricity generated or shares of renewable energy in total energy supplies within a specifi ed time period. Beyond quantitative targets, this may include factors such as achieved degrees of technological diversity (promotion of different renewable energy technologies) or of spatial diversity (geographical distribution of renewable energy supplies). Effi ciency is the ratio of outcomes to inputs, for example, renewable energy targets realized for economic resources spent, mostly measured at one point of time (static effi ciency), also called costeffectiveness. Dynamic effi ciency adds a future time dimension by including how much innovation is triggered to improve the ratio of outcomes to inputs. Equity covers the incidence and distributional consequences of a policy, including fairness, justice and respect for the rights of indigenous peoples. The equity criterion looks at the distribution of costs and benefi ts of a policy and at the inclusion and participation of wide ranges of different stakeholders (e.g., local populations, independent power producers). Institutional feasibility is the extent to which a policy or policy instrument is seen as legitimate, able to gain acceptance, and able to be adopted and implemented. It covers administrative feasibility when compatible with the available information base and administrative capacity, legal structure and economic realities. Political feasibility needs acceptance and support by stakeholders, organizations and constituencies, and compatibility with prevailing cultures and traditions. Polluter pays principle: In 1972 the OECD agreed that polluters should pay the costs of abating the own environmental pollution, for example by installation of fi lters, sanitation plants and other add-on techniques. This is the narrow defi nition. The extended defi nition is when polluters would additionally pay for the damage caused by their residual pollution (eventually also historical pollution). Another extension is the precautionary polluter pays principle where potential polluters are mandated to take insurance or preventive measures for pollution that may occur in the future. The acronym PPP has also other meanings, such as Preventing Pollution Pays-off, Public Private Partnership, or Purchasing Power Parity. Portfolio analysis: Examination of a collection of assets or policies that are characterized by different risks and payoffs. The objective function is built up around the variability of returns and their risks, leading up to the decision rule to choose the portfolio with highest expected return. Potential: Several levels of renewable energy supply potentials can be identifi ed, although every level may span a broad range. In this report, resource potential encompasses all levels for a specifi c renewable energy resource. Market potential is the amount of renewable energy output expected to occur under forecast market conditions, shaped by private economic agents and regulated by public authorities. Private economic agents realize private objectives within given, perceived and expected conditions. Market potentials are based on expected private revenues and expenditures, calculated at private prices (incorporating subsidies, levies and rents) and with private discount rates. The private context is partly shaped by public authority policies. Economic potential is the amount of renewable energy output projected when all social costs and benefi ts related to that output are included, there is full transparency of information, and assuming exchanges in the economy install a general equilibrium characterized by spatial and temporal effi ciency. Negative externalities and co-benefi ts of all energy uses and of other economic activities are priced. Social discount rates balance the interests of consecutive human generations. Sustainable development potential is the amount of renewable energy output that would be obtained in an ideal setting of perfect economic markets, optimal social (institutional and governance) systems and achievement of the sustainable fl ow of environmental goods and services. This is distinct from economic potential because it explicitly addresses inter- and intra-generational equity (distribution) and governance issues. Technical potential is the amount of renewable energy output obtainable by full implementation of demonstrated technologies or practices. No explicit reference to costs, barriers or policies is made.

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I Technical potentials reported in the literature being assessed in this report, however, may have taken into account practical constraints and when explicitly stated there, they are generally indicated in the underlying report. Theoretical potential is derived from natural and climatic (physical) parameters (e.g., total solar irradiation on a continent’s surface). The theoretical potential can be quantifi ed with reasonable accuracy, but the information is of limited practical relevance. It represents the upper limit of what can be produced from an energy resource based on physical principles and current scientifi c knowledge. It does not take into account energy losses during the conversion process necessary to make use of the resource, nor any kind of barriers. Power: Power is the rate in which energy is transferred or converted per unit of time or the rate at which work is done. It is expressed in watts (joules/second). Present value: The value of a money amount differs when the amount is available at different moments in time (years). To make amounts at differing times comparable and additive, a date is fi xed as the ‘present.’ Amounts available at different dates in the future are discounted back to a present value, and summed to get the present value of a series of future cash fl ows. Net present value is the difference between the present value of the revenues (benefi ts) and the present value of the costs. See also discounting. Project cost – see Cost. Progress ratio – see Learning curve / rate. Public fi nance: Public support for which a fi nancial return is expected (loans, equity) or fi nancial liability is incurred (guarantee). Public good: Public goods are simultaneously used by several parties (opposite to private goods). Some public goods are fully free from rivalry in use; for others the use by some subtract from the availability for others, creating congestion. Access to public goods may be restricted dependent on whether public goods are commons, state-owned or res nullius (no one’s case). The atmosphere and climate are the ultimate public goods of mankind. Many renewable energy sources are also public goods. Public-private partnerships: Arrangements typifi ed by joint working between the public and private sector. In the broadest sense, they cover all types of collaboration across the interface between the public and private sectors to deliver services or infrastructure. Quota (on renewable electricity/energy): Established quotas obligate designated parties (generators or suppliers) to meet minimum (often gradually increasing) renewable energy targets, generally expressed as percentages of total supplies or as an amount of renewable energy capacity, with costs borne by consumers. Various countries use different names for quotas, for example, Renewable Portfolio Standards, Renewable Obligations. See also tradable certifi cates Reactive power: The part of instantaneous power that does no real work. Its function is to establish and sustain the electric and magnetic fi elds required to let active power perform useful work. Rebound effect: After implementation of effi cient technologies and practices, part of the expected energy savings is not realized because the accompanying savings in energy bills may be used to acquire more energy services. For example, improvements in car engine effi ciency lower the cost per kilometre driven, encouraging consumers to drive more often or longer distances, or to spend the saved money on other energy-consuming activities. Successful energy effi ciency policies may lead to lower economy-wide energy demand and if so to lower energy prices with the possibility of the fi nancial savings stimulating rebound effects. The rebound effect is the ratio of non-realized energy and resource savings compared to the potential savings in case consumption would have remained constant as before the effi ciency measures were implemented. For climate change, the main concern about rebound effects is their impact on CO2 emissions (carbon rebound). Reforestation: Direct human-induced conversion of non-forested land to forested land through planting, seeding and/or the human-induced promotion of natural seed sources, on land that was previously forested but converted to non-forested land. See also afforestation, deforestation and land use. Regulation: A rule or order issued by governmental executive authorities or regulatory agencies and having the force of law. Regulations implement policies and are mostly specifi c for particular groups of people, legal entities or targeted activities. Regulation is also the act of designing and imposing rules or orders. Informational, transactional, administrative and political constraints in practice limit the regulator’s capability for implementing preferred policies. Reliability: In general: reliability is the degree of performance according to imposed standards or expectations. Electrical reliability is the absence of unplanned interruptions of the current by, for example, shortage of supply capacity or by failures in parts of the grid. Reliability differs from security and from fl uctuations in power quality due to impulses or harmonics. Renewable energy – see Energy Scenario: A plausible description of how the future may develop based on a coherent and internally consistent set of assumptions about key relationships and driving forces (e.g., rate of technological change, prices) on social and economic development, energy use, etc. Note that scenarios are neither predictions nor forecasts, but are useful to provide a view of the implications of alternative developments and actions. See also baseline, business as usual, models.

Seismicity: The distribution and frequency of earthquakes in time, magnitude and space, for example, the yearly number of earthquakes of magnitude between 5 and 6 per 100 km2 or in some region. Sink: Any process, activity or mechanism that removes a greenhouse gas or aerosol, or a precursor of a greenhouse gas or aerosol, from the atmosphere. Solar collector: A device for converting solar energy to thermal energy (heat) of a fl owing fl uid. Solar energy: Energy from the Sun that is captured either as heat, as light that is converted into chemical energy by natural or artifi cial photosynthesis, or by photovoltaic panels and converted directly into electricity. Concentrating solar power (CSP) systems use either lenses or mirrors to capture large amounts of solar energy and focus it down to a smaller region of space. The higher temperatures produced can operate a thermal steam turbine or be used in high-temperature industrial processes. Direct solar energy refers to the use of solar energy as it arrives at the Earth’s surface before it is stored in water or soils. Solar thermal is the use of direct solar energy for heat end-uses, excluding CSP. Active solar needs equipment like panels, pumps and fans to collect and distribute the energy. Passive solar is based on structural design and construction techniques that enable buildings to utilize solar energy for heating, cooling and lighting by non-mechanical means. Solar irradiance: The rate of solar power incidence on a surface (W/ m2). Irradiance depends on the orientation of the surface, with as special orientations: (a) surfaces perpendicular to the beam solar radiation; (b) surfaces horizontal with or on the ground. Full sun is solar irradiance that is approximately 1,000 W/m2. Solar radiation: The sun radiates light and heat energy in wavelengths from ultraviolet to infrared. Radiation arriving at surfaces may be absorbed, refl ected or transmitted. Global solar radiation consists of beam (arriving on Earth in a straight line) and diffuse radiation (arriving on Earth after being scattered by the atmosphere and by clouds). Standards: Set of rules or codes mandating or defi ning product performance (e.g., grades, dimensions, characteristics, test methods and rules for use). Product, technology or performance standards establish minimum requirements for affected products or technologies. Subsidy: Direct payment from the government or a tax reduction to a private party for implementing a practice the government wishes to encourage. The reduction of greenhouse gas emissions is stimulated by lowering existing subsidies that have the effect of raising emissions (such as subsidies for fossil fuel use) or by providing subsidies for practices that reduce emissions or enhance sinks (e.g., renewable energy projects, insulation of buildings or planting trees). Sustainable development (SD): The concept of sustainable development was introduced in the World Conservation Strategy of the International Union for Conservation of Nature in 1980 and had its roots in the concept of a sustainable society and in the management of renewable resources. Adopted by the World Council for Environment and Development in 1987 and by the Rio Conference in 1992 as a process of change in which the exploitation of resources, the direction of investments, the orientation of technological development and institutional change are all in harmony and enhance both current and future potential to meet human needs and aspirations. SD integrates the political, social, economic and environmental dimensions, and respects resource and sink constraints. Tax: A carbon tax is a levy on the carbon content of fossil fuels. Because virtually all of the carbon in fossil fuels is ultimately emitted as CO2, a carbon tax is equivalent to an emission tax on CO2 emissions. An energy tax—a levy on the energy content of fuels—reduces demand for energy and so reduces CO2 emissions from fossil fuel use. An ecotax is a carbon, emissions or energy tax designed to infl uence human behaviour (specifi cally economic behaviour) to follow an ecologically benign path. A tax credit is a reduction of tax in order to stimulate purchasing of or investment in a certain product, like greenhouse gas emission-reducing technologies. A levy or charge is used as synonymous for tax. Technological change: Mostly considered as technological improvement, that is, more or better goods and services can be provided from a given amount of resources (production factors). Economic models distinguish autonomous (exogenous), endogenous and induced technological change. Autonomous (exogenous) technological change is imposed from outside the model (i.e., as a parameter), usually in the form of a time trend affecting factor or/and energy productivity and therefore energy demand or output growth. Endogenous technological change is the outcome of economic activity within the model (i.e., as a variable) so that factor productivity or the choice of technologies is included within the model and affects energy demand and/or economic growth.

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I Induced technological change implies endogenous technological change but adds further changes induced by policies and measures, such as carbon taxes triggering research and development efforts. Technology: The practical application of knowledge to achieve particular tasks that employs both technical artefacts (hardware, equipment) and (social) information (‘software’, know-how for production and use of artefacts). Supply push aims at developing specifi c technologies through support for research, development and demonstration. Demand pull is the practice of creating market and other incentives to induce the introduction of particular sets of technologies (e.g., low-carbon technologies through carbon pricing) or single technologies (e.g., through technology-specifi c feed-in tariffs). Technology transfer: The exchange of knowledge, hardware and associated software, money and goods among stakeholders, which leads to the spread of technology for adaptation or mitigation. The term encompasses both diffusion of technologies and technological cooperation across and within countries. Tradable certifi cates (tradable green certifi cates): Parties subject to a renewable energy quota meet the annual obligation by delivering the appropriate amount of tradable certifi cates to a regulatory offi ce. The certifi cates are created by the offi ce and assigned to the renewable energy producers to sell or for their own use in fulfi lling their quota. See quota. Transmission and distribution (electricity): The network that transmits electricity through wires from where it is generated to where it is used. The distribution system refers to the lower-voltage system that actually delivers the electricity to the end user. See also grid. Turbine: Equipment that converts the kinetic energy of a fl ow of air, water, hot gas or steam into rotary mechanical power, used for direct drive or electricity generation (see wind, hydro, gas or steam turbines). Condensing steam turbines exhaust depleted steam in a heat exchanger (called condenser) using ambient cooling from water (river, lake, sea) or air sources (cooling towers). A backpressure steam turbine has no condenser at ambient temperature conditions, but exhausts all steam at higher temperatures for use in particular heat end-uses. United Nations Framework Convention on Climate Change (UNFCCC): The Convention was adopted on 9 May 1992 in New York and signed at the 1992 Earth Summit in Rio de Janeiro by more than 150 countries and the European Economic Community. Its ultimate objective is the “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system”. It contains commitments for all parties. Under the Convention, parties included in Annex I aimed to return greenhouse gas emissions not controlled by the Montreal Protocol to 1990 levels by the year 2000. The convention came into force in March 1994. In 1997, the UNFCCC adopted the Kyoto Protocol. See also Annex I countries, Annex B countries and Kyoto Protocol. Valley of death: Expression for a phase in the development of some technology when it is generating a large and negative cash fl ow because development costs increase but the risks associated with the technology are not reduced enough to entice private investors to take on the fi nancing burden. Value added: The net output of a sector or activity after adding up all outputs and subtracting intermediate inputs. Values: Worth, desirability or utility based on individual preferences. Most social science disciplines use several defi nitions of value. Related to nature and environment, there is a distinction between intrinsic and instrumental values, the latter assigned by humans. Within instrumental values, there is an unsettled catalogue of different values, such as (direct and indirect) use, option, conservation, serendipity, bequest, existence, etc. Mainstream economics defi ne the total value of any resource as the sum of the values of the different individuals involved in the use of the resource. The economic values, which are the foundation of the estimation of costs, are measured in terms of the willingness to pay by individuals to receive the resource or by the willingness of individuals to accept payment to part with the resource. Vent (geothermal/hydrothermal/submarine): An opening at the surface of the Earth (terrestrial or submarine) through which materials and energy fl ow. Venture capital: A type of private equity capital typically provided for early-stage, high-potential technology companies in the interest of generating a return on investment through a trade sale of the company or an eventual listing on a public stock exchange. Well-to-tank (WTT): WTT includes activities from resource extraction through fuel production to delivery of the fuel to vehicle. Compared to WTW, WTT does not take into consideration fuel use in vehicle operations. Well-to-wheel (WTW): WTW analysis refers to specifi c lifecycle analysis applied to transportation fuels and their use in vehicles. The WTW stage includes resource extraction, fuel production, delivery of the fuel

to vehicle, and end use of fuel in vehicle operations. Although feedstocks for alternative fuels do not necessarily come from a well, the WTW terminology is adopted for transportation fuel analysis. Wind energy: Kinetic energy from air currents arising from uneven heating of the Earth’s surface. A wind turbine is a rotating machine including its support structure for converting the kinetic energy to mechanical shaft energy to generate electricity. A windmill has oblique vanes or sails and the mechanical power obtained is mostly used directly, for example, for water pumping. A wind farm, wind project or wind power plant is a group of wind turbines interconnected to a common utility system through a system of transformers, distribution lines, and (usually) one substation.

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I Acronyms AA-CAES Advanced adiabatic compressed air energy storage AC Alternating current AEM Anion exchange membrane AEPC Alternative Energy Promotion Centre AFEX Ammonia fi bre expansion APU Auxiliary power unit AR4 4th assessment report (of the IPCC) AR5 5th assessment report (of the IPCC) BC Black carbon BCCS Biological carbon sequestration Bio-CCS Biomass with carbon capture and storage BIPV Building-integrated photovoltaic BMU Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit (German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety) BNEF Bloomberg New Energy Finance BOS Balance of systems BSI Better Sugarcane Initiative CAES Compressed air energy storage CBP Consolidated bioprocessing CC Combined cycle CCIY China Coal Industry Yearbook CCS Carbon dioxide capture and storage CDM Clean Development Mechanism CEM Cation exchange membrane CER Certifi ed Emissions Reduction CF Capacity factor CFB Circulating fl uid bed CFD Computational fl uid dynamics CFL Compact fl uorescent lightbulb CHP Combined heat and power CIGSS Copper indium/gallium disulfi de/(di)selenide CIS Commonwealth of Independent States CMA China’s Meteorological Administration CNG Compressed natural gas CoC Chain of custody COP Coeffi cient of performance CPP Captive power plant CPV Concentrating photovoltaics CREZ Competitive renewable energy zone CRF Capital recovery factor CSIRO Commonwealth Scientifi c and Industrial Research Organisation CSP Concentrating solar power CPV Concentrating photovoltaics CSTD Commission on Science and Technology (UN) DALY Disability-adjusted life year dBA A-weighted decibels DC Direct current or district cooling DDG Distillers dried grains DDGS Distillers dried grains plus solubles DH District heating DHC District heating or cooling DHW Domestic hot water DLR Deutsches Zentrum für Luft- und Raumfahrt (German Aerospace Centre) DLUC Direct land use change DME Dimethyl ether DNI Direct-normal irradiance DPH Domestic pellet heating DSSC Dye-sensitized solar cell EGS Enhanced geothermal systems EGTT Expert Group on Technology Transfer EIA Energy Information Administration (USA) EIT EMEC Economy In Transition European Marine Energy Centre EMF Energy Modelling Form EMI Electromagnetic interference ENSAD Energy-Related Severe Accident Database EPRI Electric Power Research Institute (USA) EPT Energy payback time E[R] Energy [R]evolution ER Energy ratio ERCOT Electric Reliability Council of Texas EREC European Renewable Energy Council EROEI Energy return on energy investment ESMAP Energy Sector Management Program (World Bank) ETBE Ethyl tert-butyl ether ETP Energy Technology Perspectives EU European Union EV Electric vehicle FACTS Flexible AC transmission system FASOM Forest and Agricultural Sector Optimization Model FAO Food and Agriculture Organization (of the UN) FFV Flexible fuel vehicle FQD Fuel quality directive FIT Feed-in tariff FOGIME Crediting System in Favour of Energy Management FRT Fault ride through FSU Former Soviet Union FTD Fischer-Tropsch diesel GBD Global burden of disease GBEP Global Bioenergy Partnership GCAM Global Change Assessment Model GCM Global climate model; General circulation model GDP GEF GHG GHP Gross domestic product Global Environment Facility Greenhouse gas Geothermal heat pump

GIS Geographic information system GM Genetically modifi ed GMO Genetically modifi ed organism GO Guarantee of origin GPI Genuine progress indicator GPS Global positioning system GSHP Ground source heat pump HANPP Human appropriation of terrestrial NPP HCE Heat collection element HDI Human Development Index HDR Hot dry rock HDV Heavy duty vehicle HFCV Hydrogen fuel cell electric vehicle HFR Hot fractured rock HHV Higher heating value HPP Hydropower plant HRV Heat recovery ventilator HEV Hybrid electric vehicle HVAC Heating, ventilation and air-conditioning HVDC High voltage direct current HWR Hot wet rock IA Impact assessment IAP Indoor air pollution IBC interdigitated back-contact ICE Internal combustion engine ICEV Internal combustion engine vehicle ICLEI Local Governments for Sustainability ICOLD International Commission on Large Dams ICS Improved cookstove or Integral collector storage (Ch 3) ICTSD International Centre for Trade and Sustainable Development IEA International Energy Agency IEC International Electrotechnical Commission IEEE Institute of Electrical and Electronics Engineers IHA International Hydropower Association ILUC Indirect land use change IGCC Integrated gasifi cation combined cycle IPCC Intergovernmental Panel on Climate Change IPR Intellectual property rights IQR Inter-quartile range IREDA Indian Renewable Energy Development Agency IRENA International Renewable Energy Agency IRM Inorganic mineral raw materials ISCC Integrated solar combined-cycle ISES International Solar Energy Society ISEW Index of sustainable economic welfare ISO International Organization for Standardization J Joule JI Joint implementation LCA Lifecycle assessment LCOE Levelized cost of energy (or of electricity) LCOF Levelized cost of fuel LCOH Levelized cost of heat LDV Light duty vehicle LED Light-emitting diode LHV Lower heating value LNG Liquefi ed natural gas LPG Liquefi ed petroleum gas LR Learning rate LUC Land use change M&A Mergers and acquisitions MDG Millennium Development Goals MEH Multiple-effect humidifi cation MHS Micro-hydropower systems MITI Ministry of International Trade and Industry (Japan) MSW Municipal solid waste NASA National Aeronautics and Space Administration (USA) NDRC National Development and Reform Commission (China) NFFO Non Fossil Fuel Obligation NG Natural gas NGO Nongovernmental organization Nm3 Normal cubic metre (of gas) at standard temperature and pressure NMVOC Non-methane volatile organic compounds NPP Net primary production NPV Net present value NRC National Research Council (USA) NREL National Renewable Energy Laboratory (USA) NSDS National Sustainable Development Strategies O&M Operation and maintenance OB Oscillating-body OC Organic carbon OECD Organisation for Economic Co-operation and Development OM Organic matter OPV Organic photovoltaic ORC Organic Rankine Cycle OTEC Ocean thermal energy conversion OWC Oscillating water column PACE Property Assessed Clean Energy PBR Photobioreactor PCM Phase-change material PDI Power density index PEC Photoelectrochemical PHEV Plug-in hybrid electric vehicle PM Particulate matter POME Palm oil mill effl uent PPA Purchase power agreement PRO PROALCOOL PSA PSI Pressure-retarded osmosis Brazilian Alcohol Program Probabilistic safety assessment Paul Scherrer Institute PSP Pumped storage plants PTC Production tax credit PV Photovoltaic

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I PV/T Photovoltaic/thermal PWR Pressurized water reactor R&D Research and development RBMK Reaktor bolshoy moshchnosty kanalny RCM Regional climate model RD&D Research, development and demonstration R/P Reserves to current production (ratio) RD Renewable diesel RE Renewable energy RE-C Renewable energy cooling RE-H Renewable energy heating RE-H/C Renewable energy heating/cooling REC Renewable energy certifi cate RED Reversed electro dialysis REN21 Renewable Energy Policy Network for the 21st Century RES Renewable electricity standard RM&U Renovation, modernization and upgrading RMS Root mean square RNA Rotor nacelle assembly RO Renewables obligation RoR Run of river RPS Renewable portfolio standard RSB Roundtable for Sustainable Biofuels SCADA Supervisory control and data acquisition SCC Stress corrosion cracking SD Sustainable development SEGS Solar Electric Generating Station (California) SHC Solar heating and cooling SHP Small-scale hydropower plant SI Suitability index SME Small and medium sized enterprises SNG Synthesis gas SNV Netherlands Development Organization SPF Seasonal performance factor SPM Summary for Policymakers SPP Small power producer SPS Sanitary and phytosanitary SR Short rotation SRES Special Report on Emission Scenarios (of the IPCC) SRREN Special Report on Renewable Energy Sources and Climate Change Mitigation (of the IPCC) SSCF Simultaneous saccharifi cation and co-fermentation SSF Simultaneous saccharifi cation and fermentation SSP Space-based solar power STP Standard temperature and pressure SWH Solar water heating TBM Tunnel-boring machines TERM Tonga Energy Roadmap TGC Tradable green certifi cate TPA Third-party access TPES Total primary energy supply TPWind European Wind Energy Technology Platform TS Technical Summary or thermosyphon US United States of America (adjective) USA United States of America (noun) UN United Nations UNCED United Nations Conference on Environment and Development UNCTAD United Nations Conference on Trade and Development UNDP United Nations Development Programme UNEP United Nations Environment Programme UNFCCC United Nations Framework Convention on Climate Change USD US dollar USDOE US Department of Energy V Volt VKT Vehicle kilometres travelled VRB Vanadium redox battery W Watt We Watt of electricity Wp Watt peak of PV installation WBG World Bank Group WCD World Commission on Dams WCED World Commission on Environment and Development WEA World Energy Assessment WEO World Energy Outlook WindPACT Wind Partnership for Advanced Component Technologies WTO World Trade Organization WTW Well to wheel

Prefi xes (International Standard Units) Symbol Multiplier Prefi x Symbol Multiplier Prefi x Z 10 21 zetta d 10 -1 deci E 1018 exa c 10 -2 centi P 1015 peta m 10 -3 milli T 1012 tera μ 10 -6 micro G 10 9 giga n 10 -9 nano M 10 6 mega p 10 -12 pico k 10 3 kilo f 10 -15 femto h 10 2 hecto a 10 -18 atto da 10 deca Chemical Symbols a-Si Amorphous silicon C Carbon CdS Cadmium sulphide CdTe Cadmium telluride CH4 Methane CH3CH2OH Ethanol CH3OCH3 Dimethyl ether (DME) CH3OH Methanol CIGS(S) Copper indium gallium diselenide (disulfi de) Cl Chlorine CO Carbon monoxide CO2 Carbon dioxide CO2eq Carbon dioxide equivalent c-Si Crystalline silicon Cu Copper CuInSe2 Copper indium diselenide DME Dimethyl ether Fe Iron GaAs Gallium arsenide H2 Hydrogen gas H2O Water H2S Hydrogen sulphide HFC Hydrofl uorocarbons K Potassium Mg Magnesium N Nitrogen N2 Nitrogen gas N2O Nitrous oxide Na Sodium NaS Sodium-sulfur NH3 Ammonia Ni Nickel NiCd Nickel-cadmium NOX Nitrous oxides O3 Ozone P Phosphorus PFC Perfl uorocarbon SF6 Sulfur hexafl uoride Si Silicon SiC Silicon carbide SO2 Sulfur dioxide ZnO Zinc oxide

Glossary, Acronyms, Chemical Symbols and Prefi xes Annex I
IPCC, 2012: Glossary of terms. In: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation [Field, C.B., V. Barros, T.F. Stocker, D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M. Midgley (eds.)]. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change (IPCC). Cambridge University Press, Cambridge, UK, and New York, NY, USA, pp. 555-564. Glossary of Terms II ANNEX

Abrupt climate change The nonlinearity of the climate system may lead to abrupt climate change, sometimes called rapid climate change, abrupt events, or even surprises. The term abrupt often refers to time scales faster than the typical time scale of the responsible forcing. However, not all abrupt climate changes need be externally forced. Some changes may be truly unexpected, resulting from a strong, rapidly changing forcing of a nonlinear system. Adaptation In human systems, the process of adjustment to actual or expected climate and its effects, in order to moderate harm or exploit beneficial opportunities. In natural systems, the process of adjustment to actual climate and its effects; human intervention may facilitate adjustment to expected climate. Adaptation assessment The practice of identifying options to adapt to climate change and evaluating them in terms of criteria such as availability, benefits, costs, effectiveness, efficiency, and feasibility. Adaptive capacity The combination of the strengths, attributes, and resources available to an individual, community, society, or organization that can be used to prepare for and undertake actions to reduce adverse impacts, moderate harm, or exploit beneficial opportunities. Aerosols A collection of airborne solid or liquid particles, with a typical size between 0.01 and 10 μm, that reside in the atmosphere for at least several hours. Aerosols may be of either natural or anthropogenic origin. Aerosols may influence climate in several ways: directly through scattering and absorbing radiation, and indirectly by acting as cloud condensation nuclei or modifying the optical properties and lifetime of clouds. Albedo The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. Snow-covered surfaces have a high albedo, the surface albedo of soils ranges from high to low, and vegetation-covered surfaces and oceans have a low albedo. The Earth’s planetary albedo varies mainly through varying cloudiness, snow, ice, leaf area, and land cover changes. Anthropogenic Resulting from or produced by human beings. Anthropogenic emissions Emissions of greenhouse gases, greenhouse gas precursors, and aerosols associated with human activities. These activities include the burning of fossil fuels, deforestation, land use changes, livestock, fertilization, etc., that result in a net increase in emissions. Atlantic Multi-decadal Oscillation (AMO) A multi-decadal (65- to 75-year) fluctuation in the North Atlantic, in which sea surface temperatures showed warm phases during roughly to 1880 and 1930 to 1960 and cool phases during 1905 to 1925 and 1970 to 1990 with a range of the order of 0.4°C. Atmosphere The gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1% volume mixing ratio) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93% volume mixing ratio), helium, and radiatively active greenhouse gases such as carbon dioxide (0.035% volume mixing ratio) and ozone. In addition, the atmosphere contains the greenhouse gas water vapor, whose amounts are highly variable but typically around 1% volume mixing ratio. The atmosphere also contains clouds and aerosols. Available potential energy That portion of the total potential energy that may be converted to kinetic energy in an adiabatically enclosed system. Baseline/reference The baseline (or reference) is the state against which change is measured. It might be a ‘current baseline,’ in which case it represents observable, present-day conditions. It might also be a ‘future baseline,’ which is a projected future set of conditions excluding the driving factor of interest. Alternative interpretations of the reference conditions can give rise to multiple baselines. Capacity The combination of all the strengths, attributes, and resources available to an individual, community, society, or organization, which can be used to achieve established goals. Carbon cycle The term used to describe the flow of carbon (in various forms, e.g., as carbon dioxide) through the atmosphere, ocean, terrestrial biosphere, and lithosphere. Carbon dioxide (CO2) A naturally occurring gas fixed by photosynthesis into organic matter. A byproduct of fossil fuel combustion and biomass burning, it is also emitted from land use changes and other industrial processes. It is the principal anthropogenic greenhouse gas that affects the Earth’s radiative balance. It is the reference gas against which other greenhouse gases are measured, thus having a Global Warming Potential of 1. Catchment An area that collects and drains precipitation. Clausius-Clapeyron relationship (or equation) The differential equation relating the pressure of a substance (usually


water vapor) to temperature in a system in which two phases of the substance (water) are in equilibrium. Climate Climate in a narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. In various chapters in this report different averaging periods, such as a period of 20 years, are also used. Climate change A change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.1 See also Climate variability and Detection and attribution. Climate extreme (extreme weather or climate event) The occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends of the range of observed values of the variable. For simplicity, both extreme weather events and extreme climate events are referred to collectively as ‘climate extremes.’ The full definition is provided in Section 3.1.2. Climate feedback An interaction mechanism between processes in the climate system is called a climate feedback when the result of an initial process triggers changes in a second process that in turn influences the initial one. A positive feedback intensifies the original process, and a negative feedback reduces it. Climate model A numerical representation of the climate system that is based on the physical, chemical, and biological properties of its components, their interactions, and feedback processes, and that accounts for all or some of its known properties. The climate system can be represented by models of varying complexity, that is, for any one component or combination of components a spectrum or hierarchy of models can be identified, differing in such aspects as the number of spatial dimensions, the extent to which physical, chemical, or biological processes are explicitly represented, or the level at which empirical parameterizations are involved. Coupled Atmosphere-Ocean Global Climate Models (AOGCMs), also referred to as Atmosphere-Ocean General Circulation Models, provide a representation of the climate system that is near the most comprehensive end of the spectrum currently available. There is an evolution toward more complex models with interactive chemistry and biology. Climate models are applied as a research tool to study and simulate the climate, and for operational purposes, including monthly, seasonal, and interannual climate predictions. Climate projection A projection of the response of the climate system to emissions or concentration scenarios of greenhouse gases and aerosols, or radiative forcing scenarios, often based upon simulations by climate models. Climate projections are distinguished from climate predictions in order to emphasize that climate projections depend upon the emission/ concentration/radiative-forcing scenario used, which are based on assumptions concerning, e.g., future socioeconomic and technological developments that may or may not be realized and are therefore subject to substantial uncertainty. Climate scenario A plausible and often simplified representation of the future climate, based on an internally consistent set of climatological relationships that has been constructed for explicit use in investigating the potential consequences of anthropogenic climate change, often serving as input to impact models. Climate projections often serve as the raw material for constructing climate scenarios, but climate scenarios usually require additional information such as about the observed current climate. Climate system The climate system is the highly complex system consisting of five major components: the atmosphere, the oceans, the cryosphere, the land surface, the biosphere, and the interactions between them. The climate system evolves in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations, and anthropogenic forcings such as the changing composition of the atmosphere and land use change. Climate threshold A critical limit within the climate system that induces a non-linear response to a given forcing. See also Abrupt climate change. Climate variability Climate variability refers to variations in the mean state and other statistics (such as standard deviations, the occurrence of extremes, etc.) of the climate at all spatial and temporal scales beyond that of individual weather events. Variability may be due to natural internal processes within the climate system (internal variability), or to variations in natural


or anthropogenic external forcing (external variability). See also Climate change. Cold days/cold nights Days where maximum temperature, or nights where minimum temperature, falls below the 10th percentile, where the respective temperature distributions are generally defined with respect to the -1990 reference period. Community-based disaster risk management See Local disaster risk management. Confidence Confidence in the validity of a finding, based on the type, amount, quality, and consistency of evidence and on the degree of agreement. Confidence is expressed qualitatively. Control run A model run carried out to provide a ‘baseline’ for comparison with climate change experiments. The control run uses constant values for the radiative forcing due to greenhouse gases and anthropogenic aerosols appropriate to pre-industrial conditions. Convection Vertical motion driven by buoyancy forces arising from static instability, usually caused by near-surface cooling or increases in salinity in the case of the ocean and near-surface warming in the case of the atmosphere. At the location of convection, the horizontal scale is approximately the same as the vertical scale, as opposed to the large contrast between these scales in the general circulation. The net vertical mass transport is usually much smaller than the upward and downward exchange. Coping The use of available skills, resources, and opportunities to address, manage, and overcome adverse conditions, with the aim of achieving basic functioning in the short to medium term. Coping capacity The ability of people, organizations, and systems, using available skills, resources, and opportunities, to address, manage, and overcome adverse conditions. Detection and attribution Climate varies continually on all time scales. Detection of climate change is the process of demonstrating that climate has changed in some defined statistical sense, without providing a reason for that change. Attribution of causes of climate change is the process of establishing the most likely causes for the detected change with some defined level of confidence. Diabatic A process in which external heat is gained or lost by the system. Disaster Severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting with vulnerable social conditions, leading to widespread adverse human, material, economic, or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery. Disaster management Social processes for designing, implementing, and evaluating strategies, policies, and measures that promote and improve disaster preparedness, response, and recovery practices at different organizational and societal levels. Disaster risk The likelihood over a specified time period of severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting with vulnerable social conditions, leading to widespread adverse human, material, economic, or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery. Disaster risk management (DRM) Processes for designing, implementing, and evaluating strategies, policies, and measures to improve the understanding of disaster risk, foster disaster risk reduction and transfer, and promote continuous improvement in disaster preparedness, response, and recovery practices, with the explicit purpose of increasing human security, well-being, quality of life, and sustainable development. Disaster risk reduction (DRR) Denotes both a policy goal or objective, and the strategic and instrumental measures employed for anticipating future disaster risk; reducing existing exposure, hazard, or vulnerability; and improving resilience. Diurnal temperature range The difference between the maximum and minimum temperature during a 24-hour period. Downscaling Downscaling is a method that derives local- to regional-scale (up to km) information from larger-scale models or data analyses. The full definition is provided in Section 3.2.3. Drought A period of abnormally dry weather long enough to cause a serious hydrological imbalance. Drought is a relative term (see Box 3-3), therefore any discussion in terms of precipitation deficit must refer to the particular precipitation-related activity that is under discussion. For example, shortage of precipitation during the growing season impinges on crop production or ecosystem function in general (due to soil moisture


drought, also termed agricultural drought), and during the runoff and percolation season primarily affects water supplies (hydrological drought). Storage changes in soil moisture and groundwater are also affected by increases in actual evapotranspiration in addition to reductions in precipitation. A period with an abnormal precipitation deficit is defined as a meteorological drought. A megadrought is a very lengthy and pervasive drought, lasting much longer than normal, usually a decade or more. Early warning system The set of capacities needed to generate and disseminate timely and meaningful warning information to enable individuals, communities, and organizations threatened by a hazard to prepare and to act appropriately and in sufficient time to reduce the possibility of harm or loss. El Niño-Southern Oscillation (ENSO) The term El Niño was initially used to describe a warm-water current that periodically flows along the coast of Ecuador and Peru, disrupting the local fishery. It has since become identified with a basin-wide warming of the tropical Pacific Ocean east of the dateline. This oceanic event is associated with a fluctuation of a global-scale tropical and subtropical surface pressure pattern called the Southern Oscillation. This coupled atmosphere-ocean phenomenon, with preferred time scales of 2 to about 7 years, is collectively known as the El Niño-Southern Oscillation. It is often measured by the surface pressure anomaly difference between Darwin and Tahiti and the sea surface temperatures in the central and eastern equatorial Pacific. During an ENSO event, the prevailing trade winds weaken, reducing upwelling and altering ocean currents such that the sea surface temperatures warm, further weakening the trade winds. This event has a great impact on the wind, sea surface temperature, and precipitation patterns in the tropical Pacific. It has climatic effects throughout the Pacific region and in many other parts of the world, through global teleconnections. The cold phase of ENSO is called La Niña. Emissions scenario A plausible representation of the future development of emissions of substances that are potentially radiatively active (e.g., greenhouse gases, aerosols), based on a coherent and internally consistent set of assumptions about driving forces (such as technological change, demographic and socioeconomic development) and their key relationships. Concentration scenarios, derived from emissions scenarios, are used as input to a climate model to compute climate projections. In the IPCC 1992 Supplementary Report, a set of emissions scenarios was presented, which were used as a basis for the climate projections in the IPCC Second Assessment Report. These emissions scenarios are referred to as the IS92 scenarios. In the IPCC Special Report on Emissions Scenarios, new emissions scenarios, the so-called SRES scenarios, were published. SRES scenarios (e.g., A1B, A1FI, A2, B1, B2) are used as a basis for some of the climate projections shown in Chapter 3 of this report. Ensemble A group of parallel model simulations used for climate projections. Variation of the results across the ensemble members gives an estimate of uncertainty. Ensembles made with the same model but different initial conditions only characterize the uncertainty associated with internal climate variability, whereas multi-model ensembles including simulations by several models also include the impact of model differences. Perturbed parameter ensembles, in which model parameters are varied in a systematic manner, aim to produce a more objective estimate of modeling uncertainty than is possible with traditional multimodel ensembles. Evapotranspiration The combined process of evaporation from the Earth’s surface and transpiration from vegetation. Exposure The presence of people; livelihoods; environmental services and resources; infrastructure; or economic, social, or cultural assets in places that could be adversely affected. External forcing External forcing refers to a forcing agent outside the climate system causing a change in the climate system. Volcanic eruptions, solar variations, and anthropogenic changes in the composition of the atmosphere and land use change are external forcings. Extratropical cyclone Any cyclonic-scale storm that is not a tropical cyclone. Usually refers to a middle- or high-latitude migratory storm system formed in regions of large horizontal temperature variations. Sometimes called extratropical storm or extratropical low. Extreme coastal high water (also referred to as extreme sea level) Extreme coastal high water depends on average sea level, tides, and regional weather systems. Extreme coastal high water events are usually defined in terms of the higher percentiles (e.g., 90th to 99.9th) of a distribution of hourly values of observed sea level at a station for a given reference period. Extreme weather or climate event See Climate extreme. Famine Scarcity of food over an extended period and over a large geographical area, such as a country. Famines may be triggered by extreme climate events such as drought or floods, but can also be caused by disease, war, or other factors. Flood The overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas that are not normally submerged. Floods include river (fluvial) floods, flash floods, urban floods, pluvial floods, sewer floods, coastal floods, and glacial lake outburst floods.

Frozen ground Soil or rock in which part or all of the pore water is frozen. Perennially frozen ground is called permafrost. Ground that freezes and thaws annually is called seasonally frozen ground. Glacial lake outburst flood (GLOF) Flood associated with outburst of glacial lake. Glacial lake outburst floods are typically a result of cumulative developments and occur (i) only once (e.g., full breach failure of moraine-dammed lakes), (ii) for the first time (e.g., new formation and outburst of glacial lakes), and/or (iii) repeatedly (e.g., ice-dammed lakes with drainage cycles, or ice fall). Glacier A mass of land ice that flows downhill under gravity (through internal deformation and/or sliding at the base) and is constrained by internal stress and friction at the base and sides. A glacier is maintained by accumulation of snow at high altitudes, balanced by melting at low altitudes or discharge into the sea. Global climate model (also referred to as general circulation model, both abbreviated as GCM) See Climate model. Global surface temperature The global surface temperature is an estimate of the global mean surface air temperature. However, for changes over time, only anomalies, as departures from a climatology, are used, most commonly based on the area-weighted global average of the sea surface temperature anomaly and land surface air temperature anomaly. Governance The way government is understood has changed in response to social, economic, and technological changes over recent decades. There is a corresponding shift from government defined strictly by the nation-state to a more inclusive concept of governance, recognizing the contributions of various levels of government (global, international, regional, local) and the roles of the private sector, of nongovernmental actors, and of civil society. Greenhouse effect Greenhouse gases effectively absorb thermal infrared radiation, emitted by the Earth’s surface, by the atmosphere itself due to the same gases, and by clouds. Atmospheric radiation is emitted to all sides, including downward to the Earth’s surface. Thus, greenhouse gases trap heat within the surface-troposphere system. This is called the greenhouse effect. Thermal infrared radiation in the troposphere is strongly coupled to the temperature of the atmosphere at the altitude at which it is emitted. In the troposphere, the temperature generally decreases with height. Effectively, infrared radiation emitted to space originates from an altitude with a temperature of, on average, -19°C, in balance with the net incoming solar radiation, whereas the Earth’s surface is kept at a much higher temperature of, on average, 14°C. An increase in the concentration of greenhouse gases leads to an increased infrared opacity of the atmosphere and therefore to an effective radiation into space from a higher altitude at a lower temperature. This causes a radiative forcing that leads to an enhancement of the greenhouse effect, the so-called enhanced greenhouse effect. Greenhouse gas Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic, which absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. This property causes the greenhouse effect. Water vapor (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and ozone (O3) are the primary greenhouse gases in the Earth’s atmosphere. Moreover, there are a number of entirely human-made greenhouse gases in the atmosphere, such as the halocarbons and other chlorine- and brominecontaining substances, dealt with under the Montreal Protocol. Besides CO2, N2O, and CH4, the Kyoto Protocol deals with the greenhouse gases sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs). Hazard The potential occurrence of a natural or human-induced physical event that may cause loss of life, injury, or other health impacts, as well as damage and loss to property, infrastructure, livelihoods, service provision, and environmental resources. Heat wave (also referred to as extreme heat event) A period of abnormally hot weather. Heat waves and warm spells have various and in some cases overlapping definitions. See also Warm spell. Holocene The Holocene geological epoch is the latter of two Quaternary epochs, extending from about 11.6 thousand years before present to and including the present. Human security Human security can be said to have two main aspects. It means, first, safety from such chronic threats as hunger, disease, and repression. And second, it means protection from sudden and hurtful disruptions in the patterns of daily life – whether in homes, in jobs, or in communities. Such threats can exist at all levels of national income and development. Hydrological cycle (also referred to as water cycle) The cycle in which water evaporates from the oceans and the land surface, is carried over the Earth in atmospheric circulation as water vapor, condenses to form clouds, precipitates again as rain or snow, is intercepted by trees and vegetation, provides runoff on the land surface, infiltrates into soils, recharges groundwater, and/or discharges into streams and flows out into the oceans, and ultimately evaporates again from the oceans or land surface. The various systems involved in the hydrological cycle are usually referred to as hydrological systems.


Impacts Effects on natural and human systems. In this report, the term ‘impacts’ is used to refer to the effects on natural and human systems of physical events, of disasters, and of climate change. Indian Ocean Dipole (IOD) Large-scale interannual variability of sea surface temperature in the Indian Ocean. This pattern manifests through a zonal gradient of tropical sea surface temperature, which in one extreme phase in boreal autumn shows cooling off Sumatra and warming off Somalia in the west, combined with anomalous easterlies along the equator. Insurance/reinsurance A family of financial instruments for sharing and transferring risk among a pool of at-risk households, businesses, and/or governments. See Risk transfer. Landslide A mass of material that has moved downhill by gravity, often assisted by water when the material is saturated. The movement of soil, rock, or debris down a slope can occur rapidly, or may involve slow, gradual failure. Land surface air temperature The air temperature as measured in well-ventilated screens over land at .5 to 2 m above the ground. Land use and land use change Land use refers to the total of arrangements, activities, and inputs undertaken in a certain land cover type (a set of human actions). The term land use is also used in the sense of the social and economic purposes for which land is managed (e.g., grazing, timber extraction, and conservation). Land use change refers to a change in the use or management of land by humans, which may lead to a change in land cover. Land cover and land use change may have an impact on the surface albedo, evapotranspiration, sources and sinks of greenhouse gases, or other properties of the climate system and may thus have radiative forcing and/or other impacts on climate, locally or globally. Lapse rate The rate of change of an atmospheric variable, usually temperature, with height. The lapse rate is considered positive when the variable decreases with height. Latent heat flux The flux of heat from the Earth’s surface to the atmosphere that is associated with evaporation or condensation of water vapor at the surface; a component of the surface energy budget. Likelihood A probabilistic estimate of the occurrence of a single event or of an outcome, for example, a climate parameter, observed trend, or projected change lying in a given range. Likelihood may be based on statistical or modeling analyses, elicitation of expert views, or other quantitative analyses. Local disaster risk management (LDRM) The process in which local actors (citizens, communities, government, non-profit organizations, institutions, and businesses) engage in and have ownership of the identification, analysis, evaluation, monitoring, and treatment of disaster risk and disasters, through measures that reduce or anticipate hazard, exposure, or vulnerability; transfer risk; improve disaster response and recovery; and promote an overall increase in capacities. LDRM normally requires coordination with and support from external actors at the regional, national, or international levels. Community-based disaster risk management is a subset of LDRM where community members and organizations are in the center of decisionmaking. Mass movement Mass movement in the context of mountainous phenomena refers to different types of mass transport processes including landslides, avalanches, rock fall, or debris flows. Mean sea level Sea level measured by a tide gauge with respect to the land upon which it is situated. Mean sea level is normally defined as the average relative sea level over a period, such as a month or a year, long enough to average out transients such as waves and tides. See Sea level change. Meridional overturning circulation (MOC) Meridional (north-south) overturning circulation in the ocean quantified by zonal (east-west) sums of mass transports in depth or density layers. In the North Atlantic, away from the subpolar regions, the MOC (which is in principle an observable quantity) is often identified with the thermohaline circulation, which is a conceptual interpretation. However, it must be borne in mind that MOC can also include shallower, winddriven overturning cells such as occur in the upper ocean in the tropics and subtropics, in which warm (less dense) waters moving poleward are transformed to slightly denser waters and subducted equatorward at deeper levels. Mitigation (of disaster risk and disaster) The lessening of the potential adverse impacts of physical hazards (including those that are human-induced) through actions that reduce hazard, exposure, and vulnerability. Mitigation (of climate change) A human intervention to reduce the sources or enhance the sinks of greenhouse gases. Modes of climate variability Natural variability of the climate system, in particular on seasonal and longer time scales, predominantly occurs with preferred spatial patterns

and time scales, through the dynamical characteristics of the atmospheric circulation and through interactions with the land and ocean surfaces. Such patterns are often called regimes, modes, or teleconnections. Examples are the North Atlantic Oscillation (NAO), the Pacific-North American pattern (PNA), the El Niño-Southern Oscillation (ENSO), the Northern Annular Mode (NAM; previously called the Arctic Oscillation, AO), and the Southern Annular Mode (SAM; previously called the Antarctic Oscillation, AAO). Monsoon A monsoon is a tropical and subtropical seasonal reversal in both the surface winds and associated precipitation, caused by differential heating between a continental-scale land mass and the adjacent ocean. Monsoon rains occur mainly over land in summer. Nonlinearity A process is called nonlinear when there is no simple proportional relation between cause and effect. The climate system contains many such nonlinear processes, resulting in a system with a potentially very complex behavior. Such complexity may lead to abrupt climate change. See also Predictability. North Atlantic Oscillation (NAO) The North Atlantic Oscillation consists of opposing variations in barometric pressure near Iceland and near the Azores. It therefore corresponds to fluctuations in the strength of the main westerly winds across the Atlantic into Europe, and thus to fluctuations in the embedded cyclones with their associated frontal systems. Northern Annular Mode (NAM) A winter fluctuation in the amplitude of a pattern characterized by low surface pressure in the Arctic and strong mid-latitude westerlies. NAM has links with the northern polar vortex into the stratosphere. Its pattern has a bias to the North Atlantic and has a large correlation with the North Atlantic Oscillation. Pacific Decadal Oscillation (PDO) The pattern and time series of the first empirical orthogonal function of sea surface temperature over the North Pacific north of 20°N. PDO broadened to cover the whole Pacific Basin is known as the Inter-decadal Pacific Oscillation (IPO). The PDO and IPO exhibit virtually identical temporal evolution. Parameterization In climate models, this term refers to the technique of representing processes that cannot be explicitly resolved at the spatial or temporal resolution of the model (sub-grid scale processes) by relationships between model-resolved larger-scale flow and the area- or time-averaged effect of such sub-grid scale processes. Percentile A percentile is a value on a scale of 100 that indicates the percentage of the data set values that is equal to or below it. The percentile is often used to estimate the extremes of a distribution. For example, the 90th (10th) percentile may be used to refer to the threshold for the upper (lower) extremes. Permafrost Ground (soil or rock and included ice and organic material) that remains at or below 0°C for at least 2 consecutive years. Predictability The extent to which future states of a system may be predicted based on knowledge of current and past states of the system. Probability density function (PDF) A probability density function is a function that indicates the relative chances of occurrence of different outcomes of a variable. The function integrates to unity over the domain for which it is defined and has the property that the integral over a sub-domain equals the probability that the outcome of the variable lies within that sub-domain. For example, the probability that a temperature anomaly defined in a particular way is greater than zero is obtained from its PDF by integrating the PDF over all possible temperature anomalies greater than zero. Probability density functions that describe two or more variables simultaneously are similarly defined. Projection A projection is a potential future evolution of a quantity or set of quantities, often computed with the aid of a model. Projections are distinguished from predictions in order to emphasize that projections involve assumptions concerning, for example, future socioeconomic and technological developments that may or may not be realized, and are therefore subject to substantial uncertainty. See also Climate projection and Climate prediction. Proxy climate indicator A proxy climate indicator is a local record that is interpreted, using physical and biophysical principles, to represent some combination of climate-related variations back in time. Climate-related data derived in this way are referred to as proxy data. Examples of proxies include pollen analysis, tree ring records, characteristics of corals, and various data derived from ice cores. The term ‘proxy’ can also be used to refer to indirect estimates of present-day conditions, for example, in the absence of observations. Radiative forcing Radiative forcing is the change in the net, downward minus upward, irradiance (expressed in W m–2) at the tropopause due to a change in an external driver of climate change, such as, for example, a change in the concentration of carbon dioxide or the output of the Sun. Radiative forcing is computed with all tropospheric properties held fixed at their unperturbed values, and after allowing for stratospheric temperatures, if perturbed, to readjust to radiative-dynamical equilibrium. Radiative


forcing is called instantaneous if no change in stratospheric temperature is accounted for. For the purposes of this report, radiative forcing is further defined as the change relative to the year 1750 and, unless otherwise noted, refers to a global and annual average value. Radiative forcing is not to be confused with cloud radiative forcing, a similar terminology for describing an unrelated measure of the impact of clouds on the irradiance at the top of the atmosphere. Reanalysis Reanalyses are atmospheric and oceanic analyses of temperature, wind, current, and other meteorological and oceanographic quantities, created by processing past meteorological and oceanographic data using fixed state-of-the-art weather forecasting models and data assimilation techniques. Using fixed data assimilation avoids effects from the changing analysis system that occur in operational analyses. Although continuity is improved, global reanalyses still suffer from changing coverage and biases in the observing systems. Relative sea level See Mean sea level. Resilience The ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of a hazardous event in a timely and efficient manner, including through ensuring the preservation, restoration, or improvement of its essential basic structures and functions. Return period An estimate of the average time interval between occurrences of an event (e.g., flood or extreme rainfall) of (or below/above) a defined size or intensity. Return value The highest (or, alternatively, lowest) value of a given variable, on average occurring once in a given period of time (e.g., in 10 years). Risk transfer The process of formally or informally shifting the financial consequences of particular risks from one party to another whereby a household, community, enterprise, or state authority will obtain resources from the other party after a disaster occurs, in exchange for ongoing or compensatory social or financial benefits provided to that other party. Runoff That part of precipitation that does not evaporate and is not transpired, but flows through the ground or over the ground surface and returns to bodies of water. See Hydrological cycle. Scenario A plausible and often simplified description of how the future may develop based on a coherent and internally consistent set of assumptions about driving forces and key relationships. Scenarios may be derived from projections, but are often based on additional information from other sources, sometimes combined with a narrative storyline. See also Climate scenario and Emissions scenario. Sea level change Changes in sea level, globally or locally, due to (i) changes in the shape of the ocean basins, (ii) changes in the total mass and distribution of water and land ice, (iii) changes in water density, and (iv) changes in ocean circulation. Sea level changes induced by changes in water density are called steric. Density changes induced by temperature changes only are called thermosteric, while density changes induced by salinity changes are called halosteric. See also Mean sea level. Sea surface temperature (SST) The sea surface temperature is the temperature of the subsurface bulk temperature in the top few meters of the ocean, measured by ships, buoys, and drifters. From ships, measurements of water samples in buckets were mostly switched in the 1940s to samples from engine intake water. Satellite measurements of skin temperature (uppermost layer; a fraction of a millimeter thick) in the infrared or the top centimeter or so in the microwave are also used, but must be adjusted to be compatible with the bulk temperature. Sensible heat flux The flux of heat from the Earth’s surface to the atmosphere that is not associated with phase changes of water; a component of the surface energy budget. Significant wave height The average height of the highest one-third of the wave heights (trough to peak) from sea and swell occurring in a particular time period. Soil moisture Water stored in or at the land surface and available for evapotranspiration. Southern Annular Mode (SAM) The fluctuation of a pattern like the Northern Annular Mode, but in the Southern Hemisphere. SRES scenarios See Emissions scenario. Storm surge The temporary increase, at a particular locality, in the height of the sea due to extreme meteorological conditions (low atmospheric pressure and/or strong winds). The storm surge is defined as being the excess above the level expected from the tidal variation alone at that time and place. Storm tracks Originally, a term referring to the tracks of individual cyclonic weather systems, but now often generalized to refer to the regions where the

main tracks of extratropical disturbances occur as sequences of low (cyclonic) and high (anticyclonic) pressure systems. Streamflow Water flow within a river channel, for example, expressed in m3 s-1. A synonym for river discharge. Subsidiarity The principle that decisions of government (other things being equal) are best made and implemented, if possible, at the lowest most decentralized level closest to the citizen. Subsidiarity is designed to strengthen accountability and reduce the dangers of making decisions in places remote from their point of application. The principle does not necessarily limit or constrain the action of higher orders of government, it merely counsels against the unnecessary assumption of responsibilities at a higher level. Surface temperature See Global surface temperature, Land surface air temperature, and Sea surface temperature. Sustainable development Development that meets the needs of the present without compromising the ability of future generations to meet their own needs. Transpiration The evaporation of water vapor from the surfaces of leaves through stomata. Transformation The altering of fundamental attributes of a system (including value systems; regulatory, legislative, or bureaucratic regimes; financial institutions; and technological or biological systems). Tropical cyclone The general term for a strong, cyclonic-scale disturbance that originates over tropical oceans. Distinguished from weaker systems (often named tropical disturbances or depressions) by exceeding a threshold wind speed. A tropical storm is a tropical cyclone with one-minute average surface winds between 18 and 32 m s-1. Beyond 32 m s-1, a tropical cyclone is called a hurricane, typhoon, or cyclone, depending on geographic location. Uncertainty An expression of the degree to which a value or relationship is unknown. Uncertainty can result from lack of information or from disagreement about what is known or even knowable. Uncertainty may originate from many sources, such as quantifiable errors in the data, ambiguously defined concepts or terminology, or uncertain projections of human behavior. Uncertainty can therefore be represented by quantitative measures, for example, a range of values calculated by various models, or by qualitative statements, for example, reflecting the judgment of a team of experts. See also Likelihood and Confidence. Urban heat island The relative warmth of a city compared with surrounding rural areas, associated with changes in runoff, the concrete jungle effects on heat retention, changes in surface albedo, changes in pollution and aerosols, and so on. Vulnerability The propensity or predisposition to be adversely affected. Warm days/warm nights Days where maximum temperature, or nights where minimum temperature, exceeds the 90th percentile, where the respective temperature distributions are generally defined with respect to the -1990 reference period. Warm spell A period of abnormally warm weather. Heat waves and warm spells have various and in some cases overlapping definitions. See also Heat wave.


Acronyms III ANNEX

AAO Antarctic Oscillation ADAPT Assessment & Design for Adaptation to Climate Change: A Prototype Tool AMO Atlantic Multi-decadal Oscillation AO Arctic Oscillation AR5 Fifth Assessment Report CAPE Convective Available Potential Energy CAT catastrophic risk CBA cost-benefit analysis or community-based adaptation CBD Convention on Biological Diversity CBDR common but differentiated responsibilities and respective capabilities CBO community-based organization CCA climate change adaptation CCRIF Caribbean Catastrophe Risk Insurance Facility CCSP Climate Change Science Program (US) CDD Consecutive Dry Days CDM Clean Development Mechanism CEE Centre for Environment Education CEI Climate Extremes Index C-ERA-40 Corrected ERA-40 reanalysis CFR case fatality rate CH4 methane CMIP3 Coupled Model Intercomparison Project 3 CO2 carbon dioxide COP Conference of the Parties CPP cyclone preparedness program CRED Centre for Research on the Epidemiology of Disasters CSA Canadian Standards Association CSO civil society organization CSR corporate social responsibility DDI Disaster Deficit Index DFID Department for International Development (UK) DJF December-January-February DRM disaster risk management DRR disaster risk reduction DRRM disaster risk reduction management EbA ecosystem-based adaptation EBRD European Bank for Reconstruction and Development EDI Ethiopia Drought Index ELF Emergency Liquidity Facility EM-DAT Emergency Events Database ENSO El Niño-Southern Oscillation ERA-40 European Centre for Medium Range Weather Forecasts -year reanalysis EVT extreme value theory EWS early warning system FAO Food and Agriculture Organization FONDEN Fund for Natural Disasters GAR Global Assessment Report on Disaster Risk Reduction GCM global climate model GDP gross domestic product GEC global environmental change GEF Global Environment Facility GFCS Global Framework on Climate Services GFDRR Global Facility for Disaster Reduction and Recovery GHG greenhouse gas GIS geographic information system GLOF glacial lake outburst flood GNCSODR Global Network of Civil Society Organisations for Disaster Reduction GPS Global Positioning System GSDI Global Spatial Data Infrastructure H2O water HARS Heat Action Response System HDI Human Development Index HEP hydroelectric power HFA Hyogo Framework for Action HFC hydrofluorocarbon HWDI Heat Wave Duration Index HWS Heat Warning System IADB Inter-American Development Bank IAM integrated assessment model ICSU International Council for Science ICT information and communication technology ICZM integrated coastal zone management IDMC Internal Displacement Monitoring Centre IDNDR International Decade for Natural Disaster Reduction IDP internally displaced person IDRL International Disaster Response Law IHL international humanitarian law IOD Indian Ocean Dipole IPO Inter-decadal Pacific Oscillation IRDR Integrated Research on Disaster Risk program ISSC International Social Science Council ITCZ Inter-Tropical Convergence Zone IWRM integrated water resource management JJA June-July-August LA RED Red de Estudios Sociales en Prevención de Desastres en América Latina LDC least-developed country LDCF Least Developed Countries Fund LDRM local disaster risk management LEED Leadership in Energy and Environmental Design LIDAR Light Detection and Ranging MDGs Millennium Development Goals MFI micro-finance institution MJO Madden-Julian Oscillation MLP multi-level perspective MME Multi-Model Ensemble (CMIP3) MOC meridional overturning circulation MPBI Indonesian Society for Disaster Management MSLP mean sea level pressure N2O nitrous oxide Acronyms Annex III

NAM Northern Annular Mode NAO North Atlantic Oscillation NAPA National Adaptation Programme of Action NaTech Natural Hazard Triggering a Technological Disaster NDMO National Disaster Management Office NECJOGHA Network of Climate Journalists of the Greater Horn of Africa NGO nongovernmental organization NHC National Hurricane Committee NIDM National Disaster Management Institute NMHS national meteorological and hydrological service NTR non-tide residuals NU Nunavut NWP Nairobi Work Programme NWT Northwest Territories O3 ozone OCHA United Nations Office for the Coordination of Humanitarian Affairs ODA official development assistance OECD Organisation for Economic Co-operation and Development OFDA Office of Foreign Disaster Assistance OLR outgoing longwave radiation PAR pressure and release PDF probability density function PDO Pacific Decadal Oscillation PDSI Palmer Drought Severity Index PESETA Projection of Economic impacts of climate change in Sectors of the European Union based on boTtom-up Analysis PFC perfluorocarbon PICs Pacific Island Countries and Territories PNA Pacific North American pattern POPs persistent organic pollutants PPEA Precipitation Potential Evaporation Anomaly PPP public-private partnership Pr precipitation PSNP Productive Safety Net Programme PTSD post-traumatic stress disorder PVI Prevalent Vulnerability Index RAC Regional Adaptation Collaborative RANET RAdio and InterNET RCM regional climate model REDD reduced carbon emissions from deforestation and forest degradation REDD+ reduced carbon emissions from deforestation and forest degradation, maintaining/enhancing carbon stocks, and promoting sustainable forest management RMI Republic of the Marshall Islands SAM Southern Annular Mode SAMS South American Monsoon System SCCF Special Climate Change Fund SDLE Prepare, Stay and Defend, or Leave Early SDMP School Disaster Management Plans SECO Swiss State Secretariat for Economic Affairs SF6 sulfur hexafluoride SHELDUS Spatial Hazard Events and Losses Database for the United States SIDS small island developing states SIS small island states SMA soil moisture anomaly SMEs small- and medium-sized enterprises SOI Southern Oscillation Index SPA Strategic Priority ‘Piloting an Operational Approach to Adaptation’ SPEI Standardized Precipitation-Evapotranspiration Index SPI Standard Precipitation Index SRES Special Report on Emissions Scenarios SST sea surface temperature SWH significant wave height UN United Nations UNCCD United Nations Convention to Combat Desertification UNDP United Nations Development Programme UNFCCC United Nations Framework Convention on Climate Change UNISDR United Nations International Strategy for Disaster Reduction WDSI Warm Spell Duration Index WFP World Food Programme WHO World Health Organization WMO World Meteorological Organization YT Yukon Territory Annex III Acronyms
AIII
Editor:
Serge Planton (France)
Annex III: Glossary
This annex should be cited as:
IPCC, 2013: Annex III: Glossary [Planton, S. (ed.)]. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.


This glossary defines some specific terms as the Lead Authors intend
them to be interpreted in the context of this report. Red, italicized
words indicate that the term is defined in the Glossary.
Abrupt climate change A large-scale change in the climate system
that takes place over a few decades or less, persists (or is anticipated to
persist) for at least a few decades and causes substantial disruptions in
human and natural systems.
Active layer The layer of ground that is subject to annual thawing and
freezing in areas underlain by permafrost.
Adjustment time See Lifetime. See also Response time.
Advection Transport of water or air along with its properties (e.g., temperature,
chemical tracers) by winds or currents. Regarding the general
distinction between advection and convection, the former describes transport
by large-scale motions of the atmosphere or ocean, while convection
describes the predominantly vertical, locally induced motions.
Aerosol A suspension of airborne solid or liquid particles, with a typical
size between a few nanometres and 10 μm that reside in the atmosphere
for at least several hours. For convenience the term aerosol, which includes
both the particles and the suspending gas, is often used in this report in
its plural form to mean aerosol particles. Aerosols may be of either natural
or anthropogenic origin. Aerosols may influence climate in several ways:
directly through scattering and absorbing radiation (see Aerosol–radiation
interaction) and indirectly by acting as cloud condensation nuclei or ice
nuclei, modifying the optical properties and lifetime of clouds (see Aerosol–
cloud interaction).
Aerosol–cloud interaction A process by which a perturbation to
aerosol affects the microphysical properties and evolution of clouds
through the aerosol role as cloud condensation nuclei or ice nuclei, particularly
in ways that affect radiation or precipitation; such processes can
also include the effect of clouds and precipitation on aerosol. The aerosol
perturbation can be anthropogenic or come from some natural source. The
radiative forcing from such interactions has traditionally been attributed
to numerous indirect aerosol effects, but in this report, only two levels of
radiative forcing (or effect) are distinguished:
Radiative forcing (or effect) due to aerosol–cloud interactions
(RFaci) The radiative forcing (or radiative effect, if the perturbation is
internally generated) due to the change in number or size distribution
of cloud droplets or ice crystals that is the proximate result of an aerosol
perturbation, with other variables (in particular total cloud water
content) remaining equal. In liquid clouds, an increase in cloud droplet
concentration and surface area would increase the cloud albedo. This
effect is also known as the cloud albedo effect, first indirect effect, or
Twomey effect. It is a largely theoretical concept that cannot readily be
isolated in observations or comprehensive process models due to the
rapidity and ubiquity of rapid adjustments.
Effective radiative forcing (or effect) due to aerosol–cloud interactions
(ERFaci) The final radiative forcing (or effect) from the aerosol
perturbation including the rapid adjustments to the initial change
in droplet or crystal formation rate. These adjustments include changes
in the strength of convection, precipitation efficiency, cloud fraction,
lifetime or water content of clouds, and the formation or suppression
of clouds in remote areas due to altered circulations.
The total effective radiative forcing due to both aerosol–cloud and
aerosol–radiation interactions is denoted aerosol effective radiative
forcing (ERFari+aci). See also Aerosol–radiation interaction.
Aerosol–radiation interaction An interaction of aerosol directly
with radiation produce radiative effects. In this report two levels of radiative
forcing (or effect) are distinguished:
Radiative forcing (or effect) due to aerosol–radiation interactions
(RFari) The radiative forcing (or radiative effect, if the perturbation
is internally generated) of an aerosol perturbation due directly
to aerosol–radiation interactions, with all environmental variables
remaining unaffected. Traditionally known in the literature as the direct
aerosol forcing (or effect).
Effective radiative forcing (or effect) due to aerosol-radiation
interactions (ERFari) The final radiative forcing (or effect) from
the aerosol perturbation including the rapid adjustments to the initial
change in radiation. These adjustments include changes in cloud
caused by the impact of the radiative heating on convective or largerscale
atmospheric circulations, traditionally known as semi-direct aerosol
forcing (or effect).
The total effective radiative forcing due to both aerosol–cloud and
aerosol–radiation interactions is denoted aerosol effective radiative
forcing (ERFari+aci). See also Aerosol–cloud interaction.
Afforestation Planting of new forests on lands that historically have
not contained forests. For a discussion of the term forest and related terms
such as afforestation, reforestation and deforestation, see the IPCC Special
Report on Land Use, Land-Use Change and Forestry (IPCC, 2000). See also
the report on Definitions and Methodological Options to Inventory Emissions
from Direct Human-induced Degradation of Forests and Devegetation
of Other Vegetation Types (IPCC, 2003).
Airborne fraction The fraction of total CO2 emissions (from fossil fuel
and land use change) remaining in the atmosphere.
Air mass A widespread body of air, the approximately homogeneous
properties of which (1) have been established while that air was situated
over a particular region of the Earth’s surface, and (2) undergo specific
modifications while in transit away from the source region (AMS, 2000).
Albedo The fraction of solar radiation reflected by a surface or object,
often expressed as a percentage. Snow-covered surfaces have a high
albedo, the albedo of soils ranges from high to low, and vegetation-covered
surfaces and oceans have a low albedo. The Earth’s planetary albedo
varies mainly through varying cloudiness, snow, ice, leaf area and and
cover changes.
Alkalinity A measure of the capacity of an aqueous solution to neutralize
acids.
Altimetry A technique for measuring the height of the Earth’s surface
with respect to the geocentre of the Earth within a defined terrestrial reference
frame (geocentric sea level).
Annular modes See Northern Annular Mode (NAM) and Southern
Annular Mode (SAM).
Anthropogenic Resulting from or produced by human activities.
Atlantic Multi-decadal Oscillation/Variability (AMO/AMV) A
multi-decadal (65- to 75-year) fluctuation in the North Atlantic, in which
sea surface temperatures showed warm phases during roughly 1860 to
and 1930 to 1960 and cool phases during 1905 to 1925 and 1970 to
with a range of approximately 0.4°C. See AMO Index, Box 2.5.
Atmosphere The gaseous envelope surrounding the Earth. The dry
atmosphere consists almost entirely of nitrogen (78.1% volume mixing
ratio) and oxygen (20.9% volume mixing ratio), together with a number
of trace gases, such as argon (0.93% volume mixing ratio), helium and
radiatively active greenhouse gases such as carbon dioxide (0.035%


volume mixing ratio) and ozone. In addition, the atmosphere contains the
greenhouse
gas water vapour, whose amounts are highly variable but typically
around 1% volume mixing ratio. The atmosphere also contains clouds
and aerosols.
Atmosphere–Ocean General Circulation Model (AOGCM) See
Climate model.
Atmospheric boundary layer The atmospheric layer adjacent to the
Earth’s surface that is affected by friction against that boundary surface,
and possibly by transport of heat and other variables across that surface
(AMS, 2000). The lowest 100 m of the boundary layer (about 10% of the
boundary layer thickness), where mechanical generation of turbulence is
dominant, is called the surface boundary layer or surface layer.
Atmospheric lifetime See Lifetime.
Attribution See Detection and attribution.
Autotrophic respiration Respiration by photosynthetic (see photosynthesis)
organisms (e.g., plants and algaes).
Basal lubrication Reduction of friction at the base of an ice sheet
or glacier due to lubrication by meltwater. This can allow the glacier or
ice sheet to slide over its base. Meltwater may be produced by pressureinduced
melting, friction or geothermal heat, or surface melt may drain to
the base through holes in the ice.
Baseline/reference The baseline (or reference) is the state against
which change is measured. A baseline period is the period relative to which
anomalies are computed. The baseline concentration of a trace gas is that
measured at a location not influenced by local anthropogenic emissions.
Bayesian method/approach A Bayesian method is a method by
which a statistical analysis of an unknown or uncertain quantity(ies) is carried
out in two steps. First, a prior probability distribution for the uncertain
quantity(ies) is formulated on the basis of existing knowledge (either by
eliciting expert opinion or by using existing data and studies). At this first
stage, an element of subjectivity may influence the choice, but in many
cases, the prior probability distribution can be chosen as neutrally as possible,
in order not to influence the final outcome of the analysis. In the
second step, newly acquired data are used to update the prior distribution
into a posterior distribution. The update is carried out either through an
analytic computation or though numeric approximation, using a theorem
formulated by and named after the British mathematician Thomas Bayes
(1702–1761).
Biological pump The process of transporting carbon from the ocean’s
surface layers to the deep ocean by the primary production of marine phytoplankton,
which converts dissolved inorganic carbon (DIC) and nutrients
into organic matter through photosynthesis. This natural cycle is limited
primarily by the availability of light and nutrients such as phosphate, nitrate
and silicic acid, and micronutrients, such as iron. See also Solubility pump.
Biomass The total mass of living organisms in a given area or volume;
dead plant material can be included as dead biomass. Biomass burning is
the burning of living and dead vegetation.
Biome A biome is a major and distinct regional element of the biosphere,
typically consisting of several ecosystems (e.g., forests, rivers,
ponds, swamps within a region). Biomes are characterized by typical communities
of plants and animals.
Biosphere (terrestrial and marine) The part of the Earth system
comprising all ecosystems and living organisms, in the atmosphere, on
land (terrestrial biosphere) or in the oceans (marine biosphere), including
derived dead organic matter, such as litter, soil organic matter and oceanic
detritus.
Black carbon (BC) Operationally defined aerosol species based on
measurement of light absorption and chemical reactivity and/or thermal
stability. It is sometimes referred to as soot.
Blocking Associated with persistent, slow-moving high-pressure systems
that obstruct the prevailing westerly winds in the middle and high
latitudes and the normal eastward progress of extratropical transient
storm systems. It is an important component of the intraseasonal climate
variability in the extratropics and can cause long-lived weather conditions
such as cold spells in winter and summer heat waves.
Brewer–Dobson circulation The meridional overturning circulation
of the stratosphere transporting air upward in the tropics, poleward to the
winter hemisphere, and downward at polar and subpolar latitudes. The
Brewer–Dobson circulation is driven by the interaction between upward
propagating planetary waves and the mean flow.
Burden The total mass of a gaseous substance of concern in the atmosphere.
C Stable isotope of carbon having an atomic weight of approximately
. Measurements of the ratio of 13C/12C in carbon dioxide molecules are
used to infer the importance of different carbon cycle and climate processes
and the size of the terrestrial carbon reservoir.
C Unstable isotope of carbon having an atomic weight of approximately
, and a half-life of about 5700 years. It is often used for dating
purposes going back some 40 kyr. Its variation in time is affected by the
magnetic fields of the Sun and Earth, which influence its production from
cosmic rays (see Cosmogenic radioisotopes).
Calving The breaking off of discrete pieces of ice from a glacier, ice
sheet or an ice shelf into lake or seawater, producing icebergs. This is a
form of mass loss from an ice body. See also Mass balance/budget (of
glaciers or ice sheets).
Carbonaceous aerosol Aerosol consisting predominantly of organic
substances and black carbon.
Carbon cycle The term used to describe the flow of carbon (in various
forms, e.g., as carbon dioxide) through the atmosphere, ocean, terrestrial
and marine biosphere and lithosphere. In this report, the reference unit for
the global carbon cycle is GtC or equivalently PgC (1015g).
Carbon dioxide (CO2) A naturally occurring gas, also a by-product of
burning fossil fuels from fossil carbon deposits, such as oil, gas and coal,
of burning biomass, of land use changes and of industrial processes (e.g.,
cement production). It is the principal anthropogenic greenhouse gas that
affects the Earth’s radiative balance. It is the reference gas against which
other greenhouse gases are measured and therefore has a Global Warming
Potential of 1.
Carbon dioxide (CO2) fertilization The enhancement of the growth
of plants as a result of increased atmospheric carbon dioxide (CO2) concentration.
Carbon Dioxide Removal (CDR) Carbon Dioxide Removal methods
refer to a set of techniques that aim to remove CO2 directly from the
atmosphere by either (1) increasing natural sinks for carbon or (2) using
chemical engineering to remove the CO2, with the intent of reducing the
atmospheric CO2 concentration. CDR methods involve the ocean, land and
technical systems, including such methods as iron fertilization, large-scale
afforestation and direct capture of CO2 from the atmosphere using engineered
chemical means. Some CDR methods fall under the category of
geoengineering, though this may not be the case for others, with the distinction
being based on the magnitude, scale, and impact of the particular
CDR activities. The boundary between CDR and mitigation is not clear and


there could be some overlap between the two given current definitions
(IPCC, 2012, p. 2). See also Solar Radiation Management (SRM).
CFC See Halocarbons.
Chaotic A dynamical system such as the climate system, governed by
nonlinear deterministic equations (see Nonlinearity), may exhibit erratic or
chaotic behaviour in the sense that very small changes in the initial state
of the system in time lead to large and apparently unpredictable changes
in its temporal evolution. Such chaotic behaviour limits the predictability
of the state of a nonlinear dynamical system at specific future times,
although changes in its statistics may still be predictable given changes in
the system parameters or boundary conditions.
Charcoal Material resulting from charring of biomass, usually retaining
some of the microscopic texture typical of plant tissues; chemically it
consists mainly of carbon with a disturbed graphitic structure, with lesser
amounts of oxygen and hydrogen.
Chronology Arrangement of events according to dates or times of
occurrence.
Clathrate (methane) A partly frozen slushy mix of methane gas and
ice, usually found in sediments.
Clausius–Clapeyron equation/relationship The thermodynamic
relationship between small changes in temperature and vapour pressure
in an equilibrium system with condensed phases present. For trace gases
such as water vapour, this relation gives the increase in equilibrium (or
saturation) water vapour pressure per unit change in air temperature.
Climate Climate in a narrow sense is usually defined as the average
weather, or more rigorously, as the statistical description in terms of the
mean and variability of relevant quantities over a period of time ranging
from months to thousands or millions of years. The classical period for
averaging these variables is 30 years, as defined by the World Meteorological
Organization. The relevant quantities are most often surface variables
such as temperature, precipitation and wind. Climate in a wider sense is
the state, including a statistical description, of the climate system.
Climate–carbon cycle feedback A climate feedback involving
changes in the properties of land and ocean carbon cycle in response to climate
change. In the ocean, changes in oceanic temperature and circulation
could affect the atmosphere–ocean CO2 flux; on the continents, climate
change could affect plant photosynthesis and soil microbial respiration
and hence the flux of CO2 between the atmosphere and the land biosphere.
Climate change Climate change refers to a change in the state of the
climate that can be identified (e.g., by using statistical tests) by changes
in the mean and/or the variability of its properties, and that persists for an
extended period, typically decades or longer. Climate change may be due
to natural internal processes or external forcings such as modulations of
the solar cycles, volcanic eruptions and persistent anthropogenic changes
in the composition of the atmosphere or in land use. Note that the Framework
Convention on Climate Change (UNFCCC), in its Article 1, defines
climate change as: ‘a change of climate which is attributed directly or indirectly
to human activity that alters the composition of the global atmosphere
and which is in addition to natural climate variability observed over
comparable time periods’. The UNFCCC thus makes a distinction between
climate change attributable to human activities altering the atmospheric
composition, and climate variability attributable to natural causes. See also
Climate change commitment, Detection and Attribution.
Climate change commitment Due to the thermal inertia of the
ocean and slow processes in the cryosphere and land surfaces, the climate
would continue to change even if the atmospheric composition were held
fixed at today’s values. Past change in atmospheric composition leads to
a committed climate change, which continues for as long as a radiative
imbalance persists and until all components of the climate system have
adjusted to a new state. The further change in temperature after the composition
of the atmosphere is held constant is referred to as the constant
composition temperature commitment or simply committed warming or
warming commitment. Climate change commitment includes other future
changes, for example, in the hydrological cycle, in extreme weather events,
in extreme climate events, and in sea level change. The constant emission
commitment is the committed climate change that would result from keeping
anthropogenic emissions constant and the zero emission commitment
is the climate change commitment when emissions are set to zero. See also
Climate change.
Climate feedback An interaction in which a perturbation in one
climate quantity causes a change in a second, and the change in the
second quantity ultimately leads to an additional change in the first. A
negative feedback is one in which the initial perturbation is weakened
by the changes it causes; a positive feedback is one in which the initial
perturbation is enhanced. In this Assessment Report, a somewhat narrower
definition is often used in which the climate quantity that is perturbed is
the global mean surface temperature, which in turn causes changes in the
global radiation budget. In either case, the initial perturbation can either
be externally forced or arise as part of internal variability. See also Climate
Feedback Parameter.
Climate Feedback Parameter A way to quantify the radiative
response of the climate system to a global mean surface temperature
change induced by a radiative forcing. It varies as the inverse of the effective
climate sensitivity. Formally, the Climate Feedback Parameter (a; units:
W m–2 °C–1) is defined as: a = (ΔQ – ΔF)/ΔT, where Q is the global mean
radiative forcing, T is the global mean air surface temperature, F is the
heat flux into the ocean and Δ represents a change with respect to an
unperturbed climate.
Climate forecast See Climate prediction.
Climate index A time series constructed from climate variables that
provides an aggregate summary of the state of the climate system. For
example, the difference between sea level pressure in Iceland and the
Azores provides a simple yet useful historical NAO index. Because of their
optimal properties, climate indices are often defined using principal components—
linear combinations of climate variables at different locations
that have maximum variance subject to certain normalisation constraints
(e.g., the NAM and SAM indices which are principal components of Northern
Hemisphere and Southern Hemisphere gridded pressure anomalies,
respectively). See Box 2.5 for a summary of definitions for established
observational indices. See also Climate pattern.
Climate model (spectrum or hierarchy) A numerical representation
of the climate system based on the physical, chemical and biological
properties of its components, their interactions and feedback processes,
and accounting for some of its known properties. The climate system can
be represented by models of varying complexity, that is, for any one component
or combination of components a spectrum or hierarchy of models
can be identified, differing in such aspects as the number of spatial dimensions,
the extent to which physical, chemical or biological processes are
explicitly represented or the level at which empirical parametrizations
are involved. Coupled Atmosphere–Ocean General Circulation Models
(AOGCMs) provide a representation of the climate system that is near or
at the most comprehensive end of the spectrum currently available. There
is an evolution towards more complex models with interactive chemistry
and biology. Climate models are applied as a research tool to study and
simulate the climate, and for operational purposes, including monthly, seasonal
and interannual climate predictions. See also Earth System Model,
Earth-System Model of Intermediate Complexity, Energy Balance Model,
Process-based Model, Regional Climate Model and Semi-empirical model.


Climate pattern A set of spatially varying coefficients obtained by
“projection” (regression) of climate variables onto a climate index time
series. When the climate index is a principal component, the climate pattern
is an eigenvector of the covariance matrix, referred to as an Empirical
Orthogonal Function (EOF) in climate science.
Climate prediction A climate prediction or climate forecast is the
result of an attempt to produce (starting from a particular state of the
climate system) an estimate of the actual evolution of the climate in
the future, for example, at seasonal, interannual or decadal time scales.
Because the future evolution of the climate system may be highly sensitive
to initial conditions, such predictions are usually probabilistic in nature. See
also Climate projection, Climate scenario, Model initialization and Predictability.
Climate projection A climate projection is the simulated response of
the climate system to a scenario of future emission or concentration of
greenhouse gases and aerosols, generally derived using climate models.
Climate projections are distinguished from climate predictions by their
dependence on the emission/concentration/radiative forcing scenario
used, which is in turn based on assumptions concerning, for example,
future socioeconomic and technological developments that may or may
not be realized. See also Climate scenario.
Climate regime A state of the climate system that occurs more frequently
than nearby states due to either more persistence or more frequent
recurrence. In other words, a cluster in climate state space associated with
a local maximum in the probability density function.
Climate response See Climate sensitivity.
Climate scenario A plausible and often simplified representation of
the future climate, based on an internally consistent set of climatological
relationships that has been constructed for explicit use in investigating
the potential consequences of anthropogenic climate change, often serving
as input to impact models. Climate projections often serve as the raw
material for constructing climate scenarios, but climate scenarios usually
require additional information such as the observed current climate. A climate
change scenario is the difference between a climate scenario and the
current climate. See also Emission scenario, scenario.
Climate sensitivity In IPCC reports, equilibrium climate sensitivity
(units: °C) refers to the equilibrium (steady state) change in the annual
global mean surface temperature following a doubling of the atmospheric
equivalent carbon dioxide concentration. Owing to computational constraints,
the equilibrium climate sensitivity in a climate model is sometimes
estimated by running an atmospheric general circulation model coupled
to a mixed-layer ocean model, because equilibrium climate sensitivity is
largely determined by atmospheric processes. Efficient models can be run
to equilibrium with a dynamic ocean. The climate sensitivity parameter
(units: °C (W m–2)–1) refers to the equilibrium change in the annual global
mean surface temperature following a unit change in radiative forcing.
The effective climate sensitivity (units: °C) is an estimate of the global
mean surface temperature response to doubled carbon dioxide concentration
that is evaluated from model output or observations for evolving
non-equilibrium conditions. It is a measure of the strengths of the
climate feedbacks at a particular time and may vary with forcing history
and climate state, and therefore may differ from equilibrium climate
sensitivity.
The transient climate response (units: °C) is the change in the global
mean surface temperature, averaged over a 20-year period, centred at
the time of atmospheric carbon dioxide doubling, in a climate model
simulation in which CO2 increases at 1% yr–1. It is a measure of the
strength and rapidity of the surface temperature response to greenhouse
gas forcing.
Climate sensitivity parameter See climate sensitivity.
Climate system The climate system is the highly complex system
consisting of five major components: the atmosphere, the hydrosphere,
the cryosphere, the lithosphere and the biosphere, and the interactions
between them. The climate system evolves in time under the influence of
its own internal dynamics and because of external forcings such as volcanic
eruptions, solar variations and anthropogenic forcings such as the
changing composition of the atmosphere and land use change.
Climate variability Climate variability refers to variations in the mean
state and other statistics (such as standard deviations, the occurrence of
extremes, etc.) of the climate on all spatial and temporal scales beyond
that of individual weather events. Variability may be due to natural internal
processes within the climate system (internal variability), or to variations
in natural or anthropogenic external forcing (external variability). See also
Climate change.
Cloud condensation nuclei (CCN) The subset of aerosol particles
that serve as an initial site for the condensation of liquid water, which can
lead to the formation of cloud droplets, under typical cloud formation conditions.
The main factor that determines which aerosol particles are CCN at
a given supersaturation is their size.
Cloud feedback A climate feedback involving changes in any of the
properties of clouds as a response to a change in the local or global mean
surface temperature. Understanding cloud feedbacks and determining
their magnitude and sign require an understanding of how a change in climate
may affect the spectrum of cloud types, the cloud fraction and height,
the radiative properties of clouds, and finally the Earth’s radiation budget.
At present, cloud feedbacks remain the largest source of uncertainty in
climate sensitivity estimates. See also Cloud radiative effect.
Cloud radiative effect The radiative effect of clouds relative to the
identical situation without clouds. In previous IPCC reports this was called
cloud radiative forcing, but that terminology is inconsistent with other uses
of the forcing term and is not maintained in this report. See also Cloud
feedback.
CO2-equivalent See Equivalent carbon dioxide.
Cold days/cold nights Days where maximum temperature, or nights
where minimum temperature, falls below the 10th percentile, where the
respective temperature distributions are generally defined with respect to
the 1961–1990 reference period. For the corresponding indices, see Box
.4.
Compatible emissions Earth System Models that simulate the land
and ocean carbon cycle can calculate CO2 emissions that are compatible
with a given atmospheric CO2 concentration trajectory. The compatible
emissions over a given period of time are equal to the increase of carbon
over that same period of time in the sum of the three active reservoirs: the
atmosphere, the land and the ocean.
Confidence The validity of a finding based on the type, amount, quality,
and consistency of evidence (e.g., mechanistic understanding, theory, data,
models, expert judgment) and on the degree of agreement. Confidence is
expressed qualitatively (Mastrandrea et al., 2010). See Figure 1.11 for the
levels of confidence and Table 1.1 for the list of likelihood qualifiers. See
also Uncertainty.
Convection Vertical motion driven by buoyancy forces arising from
static instability, usually caused by near-surface cooling or increases in
salinity in the case of the ocean and near-surface warming or cloud-top
radiative cooling in the case of the atmosphere. In the atmosphere convection
gives rise to cumulus clouds and precipitation and is effective at
both scavenging and vertically transporting chemical species. In the ocean
convection can carry surface waters to deep within the ocean.


Cosmogenic radioisotopes Rare radioactive isotopes that are created
by the interaction of a high-energy cosmic ray particles with atoms
nuclei. They are often used as indicator of solar activity which modulates
the cosmic rays intensity or as tracers of atmospheric transport processes,
and are also called cosmogenic radionuclides.
Cryosphere All regions on and beneath the surface of the Earth and
ocean where water is in solid form, including sea ice, lake ice, river ice,
snow cover, glaciers and ice sheets, and frozen ground (which includes
permafrost).
Dansgaard–Oeschger events Abrupt events characterized in Greenland
ice cores and in palaeoclimate records from the nearby North Atlantic
by a cold glacial state, followed by a rapid transition to a warmer phase,
and a slow cooling back to glacial conditions. Counterparts of Dansgaard–
Oeschger events are observed in other regions as well.
Deforestation Conversion of forest to non-forest. For a discussion of
the term forest and related terms such as afforestation, reforestation, and
deforestation see the IPCC Special Report on Land Use, Land-Use Change
and Forestry (IPCC, 2000). See also the report on Definitions and Methodological
Options to Inventory Emissions from Direct Human-induced
Degradation of Forests and Devegetation of Other Vegetation Types (IPCC,
).
Deglaciation/glacial termination Transitions from full glacial conditions
(ice age) to warm interglacials characterized by global warming
and sea level rise due to change in continental ice volume.
Detection and attribution Detection of change is defined as the
process of demonstrating that climate or a system affected by climate has
changed in some defined statistical sense, without providing a reason for
that change. An identified change is detected in observations if its likelihood
of occurrence by chance due to internal variability alone is determined
to be small, for example, <10%. Attribution is defined as the process
of evaluating the relative contributions of multiple causal factors to
a change or event with an assignment of statistical confidence (Hegerl et
al., 2010).
Diatoms Silt-sized algae that live in surface waters of lakes, rivers and
oceans and form shells of opal. Their species distribution in ocean cores is
often related to past sea surface temperatures.
Direct (aerosol) effect See Aerosol–radiation interaction.
Direct Air Capture Chemical process by which a pure CO2 stream is
produced by capturing CO2 from the ambient air.
Diurnal temperature range The difference between the maximum
and minimum temperature during a 24-hour period.
Dobson Unit (DU) A unit to measure the total amount of ozone in a
vertical column above the Earth’s surface (total column ozone). The number
of Dobson Units is the thickness in units of 10–5 m that the ozone column
would occupy if compressed into a layer of uniform density at a pressure
of 1013 hPa and a temperature of 0°C. One DU corresponds to a column of
ozone containing 2.69 × 1020 molecules per square metre. A typical value
for the amount of ozone in a column of the Earth’s atmosphere, although
very variable, is 300 DU.
Downscaling Downscaling is a method that derives local- to regionalscale
(10 to 100 km) information from larger-scale models or data analyses.
Two main methods exist: dynamical downscaling and empirical/statistical
downscaling. The dynamical method uses the output of regional climate
models, global models with variable spatial resolution or high-resolution
global models. The empirical/statistical methods develop statistical relationships
that link the large-scale atmospheric variables with local/
regional
climate variables. In all cases, the quality of the driving model remains an
important limitation on the quality of the downscaled information.
Drought A period of abnormally dry weather long enough to cause a
serious hydrological imbalance. Drought is a relative term; therefore any
discussion in terms of precipitation deficit must refer to the particular
precipitation-related activity that is under discussion. For example, shortage
of precipitation during the growing season impinges on crop production
or ecosystem function in general (due to soil moisture drought, also
termed agricultural drought), and during the runoff and percolation season
primarily affects water supplies (hydrological drought). Storage changes
in soil moisture and groundwater are also affected by increases in actual
evapotranspiration in addition to reductions in precipitation. A period with
an abnormal precipitation deficit is defined as a meteorological drought. A
megadrought is a very lengthy and pervasive drought, lasting much longer
than normal, usually a decade or more. For the corresponding indices, see
Box 2.4.
Dynamical system A process or set of processes whose evolution in
time is governed by a set of deterministic physical laws. The climate system
is a dynamical system. See also Abrupt climate change, Chaotic, Nonlinearity
and Predictability.
Earth System Model (ESM) A coupled atmosphere–ocean general
circulation model in which a representation of the carbon cycle is included,
allowing for interactive calculation of atmospheric CO2 or compatible
emissions. Additional components (e.g., atmospheric chemistry, ice sheets,
dynamic vegetation, nitrogen cycle, but also urban or crop models) may be
included. See also Climate model.
Earth System Model of Intermediate Complexity (EMIC) A climate
model attempting to include all the most important earth system
processes as in ESMs but at a lower resolution or in a simpler, more idealized
fashion.
Earth System sensitivity The equilibrium temperature response of
the coupled atmosphere–ocean–cryosphere–vegetation–carbon cycle
system to a doubling of the atmospheric CO2 concentration is referred to
as Earth System sensitivity. Because it allows slow components (e.g., ice
sheets, vegetation) of the climate system to adjust to the external perturbation,
it may differ substantially from the climate sensitivity derived from
coupled atmosphere–ocean models.
Ecosystem An ecosystem is a functional unit consisting of living
organisms, their non-living environment, and the interactions within and
between them. The components included in a given ecosystem and its spatial
boundaries depend on the purpose for which the ecosystem is defined:
in some cases they are relatively sharp, while in others they are diffuse.
Ecosystem boundaries can change over time. Ecosystems are nested within
other ecosystems, and their scale can range from very small to the entire
biosphere. In the current era, most ecosystems either contain people as
key organisms, or are influenced by the effects of human activities in their
environment.
Effective climate sensitivity See Climate sensitivity.
Effective radiative forcing See Radiative forcing.
Efficacy A measure of how effective a radiative forcing from a given
anthropogenic or natural mechanism is at changing the equilibrium global
mean surface temperature compared to an equivalent radiative forcing
from carbon dioxide. A carbon dioxide increase by definition has an
efficacy
of 1.0. Variations in climate efficacy may result from rapid adjustments
to the applied forcing, which differ with different forcings.
Ekman pumping Frictional stress at the surface between two fluids
(atmosphere and ocean) or between a fluid and the adjacent solid surface
(the Earth’s surface) forces a circulation. When the resulting mass


transport
is converging, mass conservation requires a vertical flow away
from the surface. This is called Ekman pumping. The opposite effect, in case
of divergence, is called Ekman suction. The effect is important in both the
atmosphere and the ocean.
Ekman transport The total transport resulting from a balance between
the Coriolis force and the frictional stress due to the action of the wind on
the ocean surface. See also Ekman pumping.
Electromagnetic spectrum Wavelength or energy range of all electromagnetic
radiation. In terms of solar radiation, the spectral irradiance is
the power arriving at the Earth per unit area, per unit wavelength.
El Niño-Southern Oscillation (ENSO) The term El Niño was initially
used to describe a warm-water current that periodically flows along the
coast of Ecuador and Peru, disrupting the local fishery. It has since become
identified with a basin-wide warming of the tropical Pacific Ocean east of
the dateline. This oceanic event is associated with a fluctuation of a globalscale
tropical and subtropical surface pressure pattern called the Southern
Oscillation. This coupled atmosphere–ocean phenomenon, with preferred
time scales of two to about seven years, is known as the El Niño-Southern
Oscillation (ENSO). It is often measured by the surface pressure anomaly
difference between Tahiti and Darwin or the sea surface temperatures in
the central and eastern equatorial Pacific. During an ENSO event, the prevailing
trade winds weaken, reducing upwelling and altering ocean currents
such that the sea surface temperatures warm, further weakening the
trade winds. This event has a great impact on the wind, sea surface temperature
and precipitation patterns in the tropical Pacific. It has climatic
effects throughout the Pacific region and in many other parts of the world,
through global teleconnections. The cold phase of ENSO is called La Niña.
For the corresponding indices, see Box 2.5.
Emission scenario A plausible representation of the future development
of emissions of substances that are potentially radiatively active
(e.g., greenhouse gases, aerosols) based on a coherent and internally consistent
set of assumptions about driving forces (such as demographic and
socioeconomic development, technological change) and their key relationships.
Concentration scenarios, derived from emission scenarios, are used
as input to a climate model to compute climate projections. In IPCC (1992)
a set of emission scenarios was presented which were used as a basis
for the climate projections in IPCC (1996). These emission scenarios are
referred to as the IS92 scenarios. In the IPCC Special Report on Emission
Scenarios (Nakićenović and Swart, 2000) emission scenarios, the so-called
SRES scenarios, were published, some of which were used, among others,
as a basis for the climate projections presented in Chapters 9 to 11 of IPCC
(2001) and Chapters 10 and 11 of IPCC (2007). New emission scenarios
for climate change, the four Representative Concentration Pathways, were
developed for, but independently of, the present IPCC assessment. See also
Climate scenario and Scenario.
Energy balance The difference between the total incoming and total
outgoing energy. If this balance is positive, warming occurs; if it is negative,
cooling occurs. Averaged over the globe and over long time periods,
this balance must be zero. Because the climate system derives virtually all
its energy from the Sun, zero balance implies that, globally, the absorbed
solar radiation, that is, incoming solar radiation minus reflected solar radiation
at the top of the atmosphere and outgoing longwave radiation emitted
by the climate system are equal. See also Energy budget.
Energy Balance Model (EBM) An energy balance model is a simplified
model that analyses the energy budget of the Earth to compute
changes in the climate. In its simplest form, there is no explicit spatial
dimension and the model then provides an estimate of the changes in
globally averaged temperature computed from the changes in radiation.
This zero-dimensional energy balance model can be extended to a onedimensional
or two-dimensional model if changes to the energy budget
with respect to latitude, or both latitude and longitude, are explicitly considered.
See also Climate model.
Energy budget (of the Earth) The Earth is a physical system with
an energy budget that includes all gains of incoming energy and all losses
of outgoing energy. The Earth’s energy budget is determined by measuring
how much energy comes into the Earth system from the Sun, how
much energy is lost to space, and accounting for the remainder on Earth
and its atmosphere. Solar radiation is the dominant source of energy into
the Earth system. Incoming solar energy may be scattered and reflected
by clouds and aerosols or absorbed in the atmosphere. The transmitted
radiation is then either absorbed or reflected at the Earth’s surface. The
average albedo of the Earth is about 0.3, which means that 30% of the
incident solar energy is reflected into space, while 70% is absorbed by
the Earth. Radiant solar or shortwave energy is transformed into sensible
heat, latent energy (involving different water states), potential energy, and
kinetic energy before being emitted as infrared radiation. With the average
surface temperature of the Earth of about 15°C (288 K), the main outgoing
energy flux is in the infrared part of the spectrum. See also Energy balance,
Latent heat flux, Sensible heat flux.
Ensemble A collection of model simulations characterizing a climate
prediction or projection. Differences in initial conditions and model formulation
result in different evolutions of the modelled system and may give
information on uncertainty associated with model error and error in initial
conditions in the case of climate forecasts and on uncertainty associated
with model error and with internally generated climate variability in the
case of climate projections.
Equilibrium and transient climate experiment An equilibrium
climate experiment is a climate model experiment in which the model is
allowed to fully adjust to a change in radiative forcing. Such experiments
provide information on the difference between the initial and final states
of the model, but not on the time-dependent response. If the forcing is
allowed to evolve gradually according to a prescribed emission scenario,
the time-dependent response of a climate model may be analysed. Such
an experiment is called a transient climate experiment. See also Climate
projection.
Equilibrium climate sensitivity See Climate sensitivity.
Equilibrium line The spatially averaged boundary at a given moment,
usually chosen as the seasonal mass budget minimum at the end of
summer, between the region on a glacier where there is a net annual loss
of ice mass (ablation area) and that where there is a net annual gain (accumulation
area). The altitude of this boundary is referred to as equilibrium
line altitude (ELA).
Equivalent carbon dioxide (CO2) concentration The concentration
of carbon dioxide that would cause the same radiative forcing as
a given mixture of carbon dioxide and other forcing components. Those
values may consider only greenhouse gases, or a combination of greenhouse
gases and aerosols. Equivalent carbon dioxide concentration is a
metric for comparing radiative forcing of a mix of different greenhouse
gases at a particular time but does not imply equivalence of the corresponding
climate change responses nor future forcing. There is generally
no connection between equivalent carbon dioxide emissions and resulting
equivalent carbon dioxide concentrations.
Equivalent carbon dioxide (CO2) emission The amount of carbon
dioxide emission that would cause the same integrated radiative forcing,
over a given time horizon, as an emitted amount of a greenhouse gas or
a mixture of greenhouse gases. The equivalent carbon dioxide emission is
obtained by multiplying the emission of a greenhouse gas by its Global
Warming Potential for the given time horizon. For a mix of greenhouse


gases it is obtained by summing the equivalent carbon dioxide emissions
of each gas. Equivalent carbon dioxide emission is a common scale for
comparing emissions of different greenhouse gases but does not imply
equivalence of the corresponding climate change responses. See also
Equivalent carbon dioxide concentration.
Evapotranspiration The combined process of evaporation from the
Earth’s surface and transpiration from vegetation.
Extended Concentration Pathways See Representative Concentration
Pathways.
External forcing External forcing refers to a forcing agent outside the
climate system causing a change in the climate system. Volcanic eruptions,
solar variations and anthropogenic changes in the composition of the
atmosphere and land use change are external forcings. Orbital forcing is
also an external forcing as the insolation changes with orbital parameters
eccentricity, tilt and precession of the equinox.
Extratropical cyclone A large-scale (of order 1000 km) storm in
the middle or high latitudes having low central pressure and fronts with
strong horizontal gradients in temperature and humidity. A major cause
of extreme wind speeds and heavy precipitation especially in wintertime.
Extreme climate event See Extreme weather event.
Extreme sea level See Storm surge.
Extreme weather event An extreme weather event is an event that
is rare at a particular place and time of year. Definitions of rare vary, but
an extreme weather event would normally be as rare as or rarer than the
th or 90th percentile of a probability density function estimated from
observations. By definition, the characteristics of what is called extreme
weather may vary from place to place in an absolute sense. When a pattern
of extreme weather persists for some time, such as a season, it may
be classed as an extreme climate event, especially if it yields an average or
total that is itself extreme (e.g., drought or heavy rainfall over a season).
Faculae Bright patches on the Sun. The area covered by faculae is greater
during periods of high solar activity.
Feedback See Climate feedback.
Fingerprint The climate response pattern in space and/or time to a specific
forcing is commonly referred to as a fingerprint. The spatial patterns of
sea level response to melting of glaciers or ice sheets (or other changes in
surface loading) are also referred to as fingerprints. Fingerprints are used
to detect the presence of this response in observations and are typically
estimated using forced climate model simulations.
Flux adjustment To avoid the problem of coupled Atmosphere–Ocean
General Circulation Models (AOGCMs) drifting into some unrealistic climate
state, adjustment terms can be applied to the atmosphere-ocean
fluxes of heat and moisture (and sometimes the surface stresses resulting
from the effect of the wind on the ocean surface) before these fluxes are
imposed on the model ocean and atmosphere. Because these adjustments
are pre-computed and therefore independent of the coupled model integration,
they are uncorrelated with the anomalies that develop during the
integration.
Forest A vegetation type dominated by trees. Many definitions of the
term forest are in use throughout the world, reflecting wide differences in
biogeophysical conditions, social structure and economics. For a discussion
of the term forest and related terms such as afforestation, reforestation and
deforestation see the IPCC Report on Land Use, Land-Use Change and Forestry
(IPCC, 2000). See also the Report on Definitions and Methodological
Options to Inventory Emissions from Direct Human-induced Degradation of
Forests and Devegetation of Other Vegetation Types (IPCC, 2003).
Fossil fuel emissions Emissions of greenhouse gases (in particular
carbon dioxide), other trace gases and aerosols resulting from the combustion
of fuels from fossil carbon deposits such as oil, gas and coal.
Framework Convention on Climate Change See United Nations
Framework Convention on Climate Change (UNFCCC).
Free atmosphere The atmospheric layer that is negligibly affected by
friction against the Earth’s surface, and which is above the atmospheric
boundary layer.
Frozen ground Soil or rock in which part or all of the pore water is
frozen. Frozen ground includes permafrost. Ground that freezes and thaws
annually is called seasonally frozen ground.
General circulation The large-scale motions of the atmosphere and
the ocean as a consequence of differential heating on a rotating Earth.
General circulation contributes to the energy balance of the system
through transport of heat and momentum.
General Circulation Model (GCM) See Climate model.
Geoengineering Geoengineering refers to a broad set of methods and
technologies that aim to deliberately alter the climate system in order to
alleviate the impacts of climate change. Most, but not all, methods seek
to either (1) reduce the amount of absorbed solar energy in the climate
system (Solar Radiation Management) or (2) increase net carbon sinks
from the atmosphere at a scale sufficiently large to alter climate (Carbon
Dioxide Removal). Scale and intent are of central importance. Two key
characteristics of geoengineering methods of particular concern are that
they use or affect the climate system (e.g., atmosphere, land or ocean)
globally or regionally and/or could have substantive unintended effects
that cross national boundaries. Geoengineering is different from weather
modification and ecological engineering, but the boundary can be fuzzy
(IPCC, 2012, p. 2).
Geoid The equipotential surface having the same geopotential at each
latitude and longitude around the world (geodesists denoting this potential
W0) that best approximates the mean sea level. It is the surface of
reference for measurement of altitude. In practice, several variations of
definitions of the geoid exist depending on the way the permanent tide
(the zero-frequency gravitational tide due to the Sun and Moon) is considered
in geodetic studies.
Geostrophic winds or currents A wind or current that is in balance
with the horizontal pressure gradient and the Coriolis force, and thus is outside
of the influence of friction. Thus, the wind or current is directly parallel
to isobars and its speed is proportional to the horizontal pressure gradient.
Glacial–interglacial cycles Phase of the Earth’s history marked by
large changes in continental ice volume and global sea level. See also Ice
age and Interglacials.
Glacial isostatic adjustment (GIA) The deformation of the Earth
and its gravity field due to the response of the earth–ocean system to
changes in ice and associated water loads. It is sometimes referred to as
glacio-hydro isostasy. It includes vertical and horizontal deformations of
the Earth’s surface and changes in geoid due to the redistribution of mass
during the ice–ocean mass exchange.
Glacier A perennial mass of land ice that originates from compressed
snow, shows evidence of past or present flow (through internal deformation
and/or sliding at the base) and is constrained by internal stress and
friction at the base and sides. A glacier is maintained by accumulation of
snow at high altitudes, balanced by melting at low altitudes and/or discharge
into the sea. An ice mass of the same origin as glaciers, but of
continental size, is called an ice sheet. For the purpose of simplicity in this
Assessment Report, all ice masses other than ice sheets are referred to as


glaciers. See also Equilibrium line and Mass balance/budget (of glaciers or
ice sheets).
Global dimming Global dimming refers to a widespread reduction of
solar radiation received at the surface of the Earth from about the year
to around 1990.
Global mean surface temperature An estimate of the global mean
surface air temperature. However, for changes over time, only anomalies,
as departures from a climatology, are used, most commonly based on the
area-weighted global average of the sea surface temperature anomaly and
land surface air temperature anomaly.
Global Warming Potential (GWP) An index, based on radiative
properties of greenhouse gases, measuring the radiative forcing following
a pulse emission of a unit mass of a given greenhouse gas in the presentday
atmosphere integrated over a chosen time horizon, relative to that of
carbon dioxide. The GWP represents the combined effect of the differing
times these gases remain in the atmosphere and their relative effectiveness
in causing radiative forcing. The Kyoto Protocol is based on GWPs
from pulse emissions over a 100-year time frame.
Greenhouse effect The infrared radiative effect of all infrared-absorbing
constituents in the atmosphere. Greenhouse gases, clouds, and (to a
small extent) aerosols absorb terrestrial radiation emitted by the Earth’s
surface and elsewhere in the atmosphere. These substances emit infrared
radiation in all directions, but, everything else being equal, the net
amount emitted to space is normally less than would have been emitted
in the absence of these absorbers because of the decline of temperature
with altitude in the troposphere and the consequent weakening of emission.
An increase in the concentration of greenhouse gases increases the
magnitude of this effect; the difference is sometimes called the enhanced
greenhouse effect. The change in a greenhouse gas concentration because
of anthropogenic emissions contributes to an instantaneous radiative forcing.
Surface temperature and troposphere warm in response to this forcing,
gradually restoring the radiative balance at the top of the atmosphere.
Greenhouse gas (GHG) Greenhouse gases are those gaseous constituents
of the atmosphere, both natural and anthropogenic, that absorb
and emit radiation at specific wavelengths within the spectrum of terrestrial
radiation emitted by the Earth’s surface, the atmosphere itself, and by
clouds. This property causes the greenhouse effect. Water vapour (H2O),
carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and ozone (O3)
are the primary greenhouse gases in the Earth’s atmosphere. Moreover,
there are a number of entirely human-made greenhouse gases in the
atmosphere, such as the halocarbons and other chlorine- and brominecontaining
substances, dealt with under the Montreal Protocol. Beside CO2,
N2O and CH4, the Kyoto Protocol deals with the greenhouse gases sulphur
hexafluoride (SF6), hydrofluorocarbons (HFCs) and perfluorocarbons
(PFCs). For a list of well-mixed greenhouse gases, see Table 2.A.1.
Gross Primary Production (GPP) The amount of carbon fixed by the
autotrophs (e.g. plants and algaes).
Grounding line The junction between a glacier or ice sheet and ice
shelf; the place where ice starts to float. This junction normally occurs over
a finite zone, rather than at a line.
Gyre Basin-scale ocean horizontal circulation pattern with slow flow
circulating around the ocean basin, closed by a strong and narrow (100 to
km wide) boundary current on the western side. The subtropical gyres
in each ocean are associated with high pressure in the centre of the gyres;
the subpolar gyres are associated with low pressure.
Hadley Circulation A direct, thermally driven overturning cell in the
atmosphere consisting of poleward flow in the upper troposphere, subsiding
air into the subtropical anticyclones, return flow as part of the trade
winds near the surface, and with rising air near the equator in the so-called
Inter-Tropical Convergence Zone.
Halocarbons A collective term for the group of partially halogenated
organic species, which includes the chlorofluorocarbons (CFCs), hydrochlorofluorocarbons
(HCFCs), hydrofluorocarbons (HFCs), halons, methyl
chloride and methyl bromide. Many of the halocarbons have large Global
Warming Potentials. The chlorine and bromine-containing halocarbons are
also involved in the depletion of the ozone layer.
Halocline A layer in the oceanic water column in which salinity changes
rapidly with depth. Generally saltier water is denser and lies below less
salty water. In some high latitude oceans the surface waters may be colder
than the deep waters and the halocline is responsible for maintaining
water column stability and isolating the surface waters from the deep
waters. See also Thermocline.
Halosteric See Sea level change.
HCFC See Halocarbons.
Heat wave A period of abnormally and uncomfortably hot weather. See
also Warm spell.
Heterotrophic respiration The conversion of organic matter to
carbon dioxide by organisms other than autotrophs.
HFC See Halocarbons.
Hindcast or retrospective forecast A forecast made for a period in
the past using only information available before the beginning of the forecast.
A sequence of hindcasts can be used to calibrate the forecast system
and/or provide a measure of the average skill that the forecast system has
exhibited in the past as a guide to the skill that might be expected in the
future.
Holocene The Holocene Epoch is the latter of two epochs in the Quaternary
System, extending from 11.65 ka (thousand years before 1950) to
the present. It is also known as Marine Isotopic Stage (MIS) 1 or current
interglacial.
Hydroclimate Part of the climate pertaining to the hydrology of a
region.
Hydrological cycle The cycle in which water evaporates from the
oceans and the land surface, is carried over the Earth in atmospheric
circulation as water vapour, condenses to form clouds, precipitates over
ocean and land as rain or snow, which on land can be intercepted by trees
and vegetation, provides runoff on the land surface, infiltrates into soils,
recharges groundwater, discharges into streams and ultimately flows out
into the oceans, from which it will eventually evaporate again. The various
systems involved in the hydrological cycle are usually referred to as
hydrological systems.
Hydrosphere The component of the climate system comprising liquid
surface and subterranean water, such as oceans, seas, rivers, fresh water
lakes, underground water, etc.
Hypsometry The distribution of land or ice surface as a function of
altitude.
Ice age An ice age or glacial period is characterized by a long-term
reduction in the temperature of the Earth’s climate, resulting in growth of
ice sheets and glaciers.
Ice–albedo feedback A climate feedback involving changes in the
Earth’s surface albedo. Snow and ice have an albedo much higher (up to
~0.8) than the average planetary albedo (~0.3). With increasing temperatures,
it is anticipated that snow and ice extent will decrease, the Earth’s
overall albedo will decrease and more solar radiation will be absorbed,
warming the Earth further.


Ice core A cylinder of ice drilled out of a glacier or ice sheet.
Ice sheet A mass of land ice of continental size that is sufficiently thick
to cover most of the underlying bed, so that its shape is mainly determined
by its dynamics (the flow of the ice as it deforms internally and/or slides at
its base). An ice sheet flows outward from a high central ice plateau with
a small average surface slope. The margins usually slope more steeply, and
most ice is discharged through fast flowing ice streams or outlet glaciers,
in some cases into the sea or into ice shelves floating on the sea. There are
only two ice sheets in the modern world, one on Greenland and one on
Antarctica. During glacial periods there were others.
Ice shelf A floating slab of ice of considerable thickness extending from
the coast (usually of great horizontal extent with a very gently sloping
surface), often filling embayments in the coastline of an ice sheet. Nearly
all ice shelves are in Antarctica, where most of the ice discharged into the
ocean flows via ice shelves.
Ice stream A stream of ice with strongly enhanced flow that is part of
an ice sheet. It is often separated from surrounding ice by strongly sheared,
crevassed margins. See also Outlet glacier.
Incoming solar radiation See Insolation.
Indian Ocean Dipole (IOD) Large–scale mode of interannual variability
of sea surface temperature in the Indian Ocean. This pattern manifests
through a zonal gradient of tropical sea surface temperature, which in one
extreme phase in boreal autumn shows cooling off Sumatra and warming
off Somalia in the west, combined with anomalous easterlies along the
equator.
Indirect aerosol effect See Aerosol-cloud interaction.
Industrial Revolution A period of rapid industrial growth with farreaching
social and economic consequences, beginning in Britain during
the second half of the 18th century and spreading to Europe and later to
other countries including the United States. The invention of the steam
engine was an important trigger of this development. The industrial revolution
marks the beginning of a strong increase in the use of fossil fuels and
emission of, in particular, fossil carbon dioxide. In this report the terms preindustrial
and industrial refer, somewhat arbitrarily, to the periods before
and after 1750, respectively.
Infrared radiation See Terrestrial radiation.
Insolation The amount of solar radiation reaching the Earth by latitude
and by season measured in W m–2. Usually insolation refers to the
radiation arriving at the top of the atmosphere. Sometimes it is specified
as referring to the radiation arriving at the Earth’s surface. See also Total
Solar Irradiance.
Interglacials or interglaciations The warm periods between ice age
glaciations. Often defined as the periods at which sea levels were close
to present sea level. For the Last Interglacial (LIG) this occurred between
about 129 and 116 ka (thousand years) before present (defined as 1950)
although the warm period started in some areas a few thousand years
earlier. In terms of the oxygen isotope record interglaciations are defined
as the interval between the midpoint of the preceding termination and
the onset of the next glaciation. The present interglaciation, the Holocene,
started at 11.65 ka before present although globally sea levels did not
approach their present position until about 7 ka before present.
Internal variability See Climate variability.
Inter-Tropical Convergence Zone (ITCZ) The Inter-Tropical Convergence
Zone is an equatorial zonal belt of low pressure, strong convection
and heavy precipitation near the equator where the northeast trade winds
meet the southeast trade winds. This band moves seasonally.
Iron fertilization Deliberate introduction of iron to the upper ocean
intended to enhance biological productivity which can sequester additional
atmospheric carbon dioxide into the oceans.
Irreversibility A perturbed state of a dynamical system is defined as
irreversible on a given timescale, if the recovery timescale from this state
due to natural processes is significantly longer than the time it takes for the
system to reach this perturbed state. In the context of WGI, the time scale
of interest is centennial to millennial. See also Tipping point.
Isostatic or Isostasy Isostasy refers to the response of the earth to
changes in surface load. It includes the deformational and gravitational
response. This response is elastic on short time scales, as in the earth–
ocean response to recent changes in mountain glaciation, or viscoelastic
on longer time scales, as in the response to the last deglaciation following
the Last Glacial Maximum. See also Glacial Isostatic Adjustment (GIA).
Isotopes Atoms of the same chemical element that have the same the
number of protons but differ in the number of neutrons. Some proton–
neutron configurations are stable (stable isotopes), others are unstable
undergoing spontaneous radioactive decay (radioisotopes). Most elements
have more than one stable isotope. Isotopes can be used to trace transport
processes or to study processes that change the isotopic ratio. Radioisotopes
provide in addition time information that can be used for radiometric
dating.
Kyoto Protocol The Kyoto Protocol to the United Nations Framework
Convention on Climate Change (UNFCCC) was adopted in 1997 in Kyoto,
Japan, at the Third Session of the Conference of the Parties (COP) to the
UNFCCC. It contains legally binding commitments, in addition to those
included in the UNFCCC. Countries included in Annex B of the Protocol
(most Organisation for Economic Cooperation and Development countries
and countries with economies in transition) agreed to reduce their anthropogenic
greenhouse gas emissions (carbon dioxide, methane, nitrous
oxide, hydrofluorocarbons, perfluorocarbons, and sulphur hexafluoride) by
at least 5% below 1990 levels in the commitment period 2008–2012. The
Kyoto Protocol entered into force on 16 February 2005.
Land surface air temperature The surface air temperature as measured
in well-ventilated screens over land at 1.5 m above the ground.
Land use and Land use change Land use refers to the total of
arrangements, activities and inputs undertaken in a certain land cover type
(a set of human actions). The term land use is also used in the sense of the
social and economic purposes for which land is managed (e.g., grazing,
timber extraction and conservation). Land use change refers to a change
in the use or management of land by humans, which may lead to a change
in land cover. Land cover and land use change may have an impact on
the surface albedo, evapotranspiration, sources and sinks of greenhouse
gases, or other properties of the climate system and may thus give rise to
radiative forcing and/or other impacts on climate, locally or globally. See
also the IPCC Report on Land Use, Land-Use Change, and Forestry (IPCC,
).
Land water storage Water stored on land other than in glaciers and
ice sheets (that is water stored in rivers, lakes, wetlands, the vadose zone,
aquifers, reservoirs, snow and permafrost). Changes in land water storage
driven by climate and human activities contribute to sea level change.
La Niña See El Niño-Southern Oscillation.
Lapse rate The rate of change of an atmospheric variable, usually temperature,
with height. The lapse rate is considered positive when the variable
decreases with height.
Last Glacial Maximum (LGM) The period during the last ice age when
the glaciers and ice sheets reached their maximum extent, approximately


ka ago. This period has been widely studied because the radiative forcings
and boundary conditions are relatively well known.
Last Interglacial (LIG) See Interglacials.
Latent heat flux The turbulent flux of heat from the Earth’s surface
to the atmosphere that is associated with evaporation or condensation of
water vapour at the surface; a component of the surface energy budget.
Lifetime Lifetime is a general term used for various time scales characterizing
the rate of processes affecting the concentration of trace gases.
The following lifetimes may be distinguished:
Turnover time (T) (also called global atmospheric lifetime) is the
ratio of the mass M of a reservoir (e.g., a gaseous compound in the
atmosphere) and the total rate of removal S from the reservoir: T = M/S.
For each removal process, separate turnover times can be defined. In
soil carbon biology, this is referred to as Mean Residence Time.
Adjustment time or response time (Ta) is the time scale characterizing
the decay of an instantaneous pulse input into the reservoir. The
term adjustment time is also used to characterize the adjustment of
the mass of a reservoir following a step change in the source strength.
Half-life or decay constant is used to quantify a first-order exponential
decay process. See Response time for a different definition pertinent to
climate variations.
The term lifetime is sometimes used, for simplicity, as a surrogate for
adjustment time.
In simple cases, where the global removal of the compound is directly
proportional to the total mass of the reservoir, the adjustment time
equals the turnover time: T = Ta. An example is CFC-11, which is
removed from the atmosphere only by photochemical processes in the
stratosphere. In more complicated cases, where several reservoirs are
involved or where the removal is not proportional to the total mass,
the equality T = Ta no longer holds. Carbon dioxide (CO2) is an extreme
example. Its turnover time is only about 4 years because of the rapid
exchange between the atmosphere and the ocean and terrestrial biota.
However, a large part of that CO2 is returned to the atmosphere within
a few years. Thus, the adjustment time of CO2 in the atmosphere is
actually determined by the rate of removal of carbon from the surface
layer of the oceans into its deeper layers. Although an approximate
value of 100 years may be given for the adjustment time of CO2 in the
atmosphere, the actual adjustment is faster initially and slower later
on. In the case of methane (CH4), the adjustment time is different from
the turnover time because the removal is mainly through a chemical
reaction with the hydroxyl radical (OH), the concentration of which
itself depends on the CH4 concentration. Therefore, the CH4 removal
rate S is not proportional to its total mass M.
Likelihood The chance of a specific outcome occurring, where this
might be estimated probabilistically. This is expressed in this report using a
standard terminology, defined in Table 1.1. See also Confidence and Uncertainty.
Lithosphere The upper layer of the solid Earth, both continental and
oceanic, which comprises all crustal rocks and the cold, mainly elastic
part of the uppermost mantle. Volcanic activity, although part of the lithosphere,
is not considered as part of the climate system, but acts as an
external forcing factor. See also Isostatic.
Little Ice Age (LIA) An interval during the last millennium characterized
by a number of extensive expansions of mountain glaciers and
moderate retreats in between them, both in the Northern and Southern
Hemispheres. The timing of glacial advances differs between regions and
the LIA is, therefore, not clearly defined in time. Most definitions lie in the
period 1400 CE and 1900 CE. Currently available reconstructions of average
Northern Hemisphere temperature indicate that the coolest periods at
the hemispheric scale may have occurred from 1450 to 1850 CE.
Longwave radiation See Terrestrial radiation.
Madden–Julian Oscillation (MJO) The largest single component of
tropical atmospheric intraseasonal variability (periods from 30 to 90 days).
The MJO propagates eastwards at around 5 m s–1 in the form of a largescale
coupling between atmospheric circulation and deep convection. As it
progresses, it is associated with large regions of both enhanced and suppressed
rainfall, mainly over the Indian and western Pacific Oceans. Each
MJO event lasts approximately 30 to 60 days, hence the MJO is also known
as the 30- to 60-day wave, or the intraseasonal oscillation.
Marine-based ice sheet An ice sheet containing a substantial region
that rests on a bed lying below sea level and whose perimeter is in contact
with the ocean. The best known example is the West Antarctic ice sheet.
Mass balance/budget (of glaciers or ice sheets) The balance
between the mass input to the ice body (accumulation) and the mass loss
(ablation and iceberg calving) over a stated period of time, which is often
a year or a season. Point mass balance refers to the mass balance at a
particular location on the glacier or ice sheet. Surface mass balance is the
difference between surface accumulation and surface ablation. The input
and output terms for mass balance are:
Accumulation All processes that add to the mass of a glacier. The
main contribution to accumulation is snowfall. Accumulation also
includes deposition of hoar, freezing rain, other types of solid precipitation,
gain of wind-blown snow, and avalanching.
Ablation Surface processes that reduce the mass of a glacier. The
main contributor to ablation is melting with runoff but on some glaciers
sublimation, loss of wind-blown snow and avalanching are also
significant processes of ablation.
Discharge/outflow Mass loss by iceberg calving or ice discharge
across the grounding line of a floating ice shelf. Although often treated
as an ablation term, in this report iceberg calving and discharge is considered
separately from surface ablation.
Mean sea level The surface level of the ocean at a particular point
averaged over an extended period of time such as a month or year. Mean
sea level is often used as a national datum to which heights on land are
referred.
Medieval Climate Anomaly (MCA) See Medieval Warm Period.
Medieval Warm Period (MWP) An interval of relatively warm conditions
and other notable climate anomalies such as more extensive
drought in some continental regions. The timing of this interval is not
clearly defined, with different records showing onset and termination of
the warmth at different times, and some showing intermittent warmth.
Most definitions lie within the period 900 to 1400 CE. Currently available
reconstructions of average Northern Hemisphere temperature indicate that
the warmest period at the hemispheric scale may have occurred from 950
to 1250 CE. Currently available records and temperature reconstructions
indicate that average temperatures during parts of the MWP were indeed
warmer in the context of the last 2 kyr, though the warmth may not have
been as ubiquitous across seasons and geographical regions as the 20th
century warming. It is also called Medieval Climate Anomaly.
Meridional Overturning Circulation (MOC) Meridional (north–
south) overturning circulation in the ocean quantified by zonal (east–west)
sums of mass transports in depth or density layers. In the North Atlantic,
away from the subpolar regions, the MOC (which is in principle an observable
quantity) is often identified with the thermohaline circulation (THC),


which is a conceptual and incomplete interpretation. It must be borne in
mind that the MOC is also driven by wind, and can also include shallower
overturning cells such as occur in the upper ocean in the tropics and subtropics,
in which warm (light) waters moving poleward are transformed to
slightly denser waters and subducted equatorward at deeper levels.
Metadata Information about meteorological and climatological data
concerning how and when they were measured, their quality, known problems
and other characteristics.
Methane (CH4) Methane is one of the six greenhouse gases to be mitigated
under the Kyoto Protocol and is the major component of natural gas
and associated with all hydrocarbon fuels, animal husbandry and agriculture.
Metric A consistent measurement of a characteristic of an object or
activity that is otherwise difficult to quantify. Within the context of the
evaluation of climate models, this is a quantitative measure of agreement
between a simulated and observed quantity which can be used to assess
the performance of individual models.
Microwave Sounding Unit (MSU) A microwave sounder on National
Oceanic and Atmospheric Administration (NOAA) polar orbiter satellites,
that estimates the temperature of thick layers of the atmosphere by measuring
the thermal emission of oxygen molecules from a complex of emission
lines near 60 GHz. A series of nine MSUs began making this kind
of measurement in late 1978. Beginning in mid 1998, a follow-on series
of instruments, the Advanced Microwave Sounding Units (AMSUs), began
operation.
Mineralization/Remineralization The conversion of an element
from its organic form to an inorganic form as a result of microbial decomposition.
In nitrogen mineralization, organic nitrogen from decaying plant
and animal residues (proteins, nucleic acids, amino sugars and urea) is
converted to ammonia (NH3) and ammonium (NH4
+) by biological activity.
Mitigation A human intervention to reduce the sources or enhance the
sinks of greenhouse gases.
Mixing ratio See Mole fraction.
Model drift Since model climate differs to some extent from observed
climate, climate forecasts will typically ‘drift’ from the initial observationbased
state towards the model’s climate. This drift occurs at different time
scales for different variables, can obscure the initial-condition forecast
information and is usually removed a posteriori by an empirical, usually
linear, adjustment.
Model hierarchy See Climate model (spectrum or hierarchy).
Model initialization A climate forecast typically proceeds by integrating
a climate model forward in time from an initial state that is intended
to reflect the actual state of the climate system. Available observations of
the climate system are ‘assimilated’ into the model. Initialization is a complex
process that is limited by available observations, observational errors
and, depending on the procedure used, may be affected by uncertainty in
the history of climate forcing. The initial conditions will contain errors that
grow as the forecast progresses, thereby limiting the time for which the
forecast will be useful. See also Climate prediction.
Model spread The range or spread in results from climate models,
such as those assembled for Coupled Model Intercomparison Project
Phase 5 (CMIP5). Does not necessarily provide an exhaustive and formal
estimate
of the uncertainty in feedbacks, forcing or projections even when
expressed numerically, for example, by computing a standard deviation of
the models’ responses. In order to quantify uncertainty, information from
observations, physical constraints and expert judgement must be combined,
using a statistical framework.
Mode of climate variability Underlying space–time structure with
preferred spatial pattern and temporal variation that helps account for the
gross features in variance and for teleconnections. A mode of variability
is often considered to be the product of a spatial climate pattern and an
associated climate index time series.
Mole fraction Mole fraction, or mixing ratio, is the ratio of the number
of moles of a constituent in a given volume to the total number of moles
of all constituents in that volume. It is usually reported for dry air. Typical
values for well-mixed greenhouse gases are in the order of μmol mol–1
(parts per million: ppm), nmol mol–1 (parts per billion: ppb), and fmol mol–1
(parts per trillion: ppt). Mole fraction differs from volume mixing ratio,
often expressed in ppmv etc., by the corrections for non-ideality of gases.
This correction is significant relative to measurement precision for many
greenhouse gases (Schwartz and Warneck, 1995).
Monsoon A monsoon is a tropical and subtropical seasonal reversal in
both the surface winds and associated precipitation, caused by differential
heating between a continental-scale land mass and the adjacent ocean.
Monsoon rains occur mainly over land in summer.
Montreal Protocol The Montreal Protocol on Substances that Deplete
the Ozone Layer was adopted in Montreal in 1987, and subsequently
adjusted and amended in London (1990), Copenhagen (1992), Vienna
(1995), Montreal (1997) and Beijing (1999). It controls the consumption
and production of chlorine- and bromine-containing chemicals that
destroy stratospheric ozone, such as chlorofluorocarbons, methyl chloroform,
carbon tetrachloride and many others.
Near-surface permafrost A term frequently used in climate model
applications to refer to permafrost at depths close to the ground surface
(typically down to 3.5 m). In modelling studies, near-surface permafrost
is usually diagnosed from 20 or 30 year climate averages, which is different
from the conventional definition of permafrost. Disappearance of
near-surface permafrost in a location does not preclude the longer-term
persistence of permafrost at greater depth. See also Active layer, Frozen
ground and Thermokarst.
Near-term climate forcers (NTCF) Near-term climate forcers (NTCF)
refer to those compounds whose impact on climate occurs primarily within
the first decade after their emission. This set of compounds is primarily
composed of those with short lifetimes in the atmosphere compared to
well-mixed greenhouse gases, and has been sometimes referred to as
short lived climate forcers or short-lived climate pollutants. However, the
common property that is of greatest interest to a climate assessment is
the timescale over which their impact on climate is felt. This set of compounds
includes methane, which is also a well-mixed greenhouse gas, as
well as ozone and aerosols, or their precursors, and some halogenated
species that are not well-mixed greenhouse gases. These compounds do
not accumulate in the atmosphere at decadal to centennial timescales,
and so their effect on climate is predominantly in the near term following
their emission.
Nitrogen deposition Nitrogen deposition is defined as the nitrogen
transferred from the atmosphere to the Earth’s surface by the processes of
wet deposition and dry deposition.
Nitrous oxide (N2O) One of the six greenhouse gases to be mitigated
under the Kyoto Protocol. The main anthropogenic source of nitrous
oxide is agriculture (soil and animal manure management), but important
contributions
also come from sewage treatment, combustion of fossil fuel,
and chemical industrial processes. Nitrous oxide is also produced naturally
from a wide variety of biological sources in soil and water, particularly
microbial action in wet tropical forests.


Nonlinearity A process is called nonlinear when there is no simple proportional
relation between cause and effect. The climate system contains
many such nonlinear processes, resulting in a system with potentially very
complex behaviour. Such complexity may lead to abrupt climate change.
See also Chaotic and Predictability.
North Atlantic Oscillation (NAO) The North Atlantic Oscillation consists
of opposing variations of surface pressure near Iceland and near the
Azores. It therefore corresponds to fluctuations in the strength of the main
westerly winds across the Atlantic into Europe, and thus to fluctuations in
the embedded extratropical cyclones with their associated frontal systems.
See NAO Index, Box 2.5.
Northern Annular Mode (NAM) A winter fluctuation in the amplitude
of a pattern characterized by low surface pressure in the Arctic and
strong mid-latitude westerlies. The NAM has links with the northern polar
vortex into the stratosphere. Its pattern has a bias to the North Atlantic and
its index has a large correlation with the North Atlantic Oscillation index.
See NAM Index, Box 2.5.
Ocean acidification Ocean acidification refers to a reduction in the pH
of the ocean over an extended period, typically decades or longer, which
is caused primarily by uptake of carbon dioxide from the atmosphere, but
can also be caused by other chemical additions or subtractions from the
ocean. Anthropogenic ocean acidification refers to the component of pH
reduction that is caused by human activity (IPCC, 2011, p. 37).
Ocean heat uptake efficiency This is a measure (W m–2 °C–1) of
the rate at which heat storage by the global ocean increases as global
mean surface temperature rises. It is a useful parameter for climate change
experiments in which the radiative forcing is changing monotonically,
when it can be compared with the Climate Feedback Parameter to gauge
the relative importance of climate response and ocean heat uptake in
determining the rate of climate change. It can be estimated from such an
experiment as the ratio of the rate of increase of ocean heat content to the
global mean surface air temperature change.
Organic aerosol Component of the aerosol that consists of organic
compounds, mainly carbon, hydrogen, oxygen and lesser amounts of other
elements. See also Carbonaceous aerosol.
Outgoing longwave radiation Net outgoing radiation in the infrared
part of the spectrum at the top of the atmosphere. See also Terrestrial
radiation.
Outlet glacier A glacier, usually between rock walls, that is part of, and
drains an ice sheet. See also Ice stream.
Ozone Ozone, the triatomic form of oxygen (O3), is a gaseous atmospheric
constituent. In the troposphere, it is created both naturally and by photochemical
reactions involving gases resulting from human activities (smog).
Tropospheric ozone acts as a greenhouse gas. In the stratosphere, it is created
by the interaction between solar ultraviolet radiation and molecular
oxygen (O2). Stratospheric ozone plays a dominant role in the stratospheric
radiative balance. Its concentration is highest in the ozone layer.
Ozone hole See Ozone layer.
Ozone layer The stratosphere contains a layer in which the concentration
of ozone is greatest, the so-called ozone layer. The layer extends from
about 12 to 40 km above the Earth’s surface. The ozone concentration
reaches a maximum between about 20 and 25 km. This layer has been
depleted by human emissions of chlorine and bromine compounds. Every
year, during the Southern Hemisphere spring, a very strong depletion of
the ozone layer takes place over the Antarctic, caused by anthropogenic
chlorine and bromine compounds in combination with the specific meteorological
conditions of that region. This phenomenon is called the Ozone
hole. See also Montreal Protocol.
Pacific Decadal Oscillation (PDO) The pattern and time series of
the first empirical orthogonal function of sea surface temperature over the
North Pacific north of 20°N. The PDO broadened to cover the whole Pacific
Basin is known as the Inter-decadal Pacific Oscillation. The PDO and IPO
exhibit similar temporal evolution. See also Pacific Decadal Variability.
Pacific decadal variability Coupled decadal-to-inter-decadal variability
of the atmospheric circulation and underlying ocean in the Pacific
Basin. It is most prominent in the North Pacific, where fluctuations in the
strength of the winter Aleutian Low pressure system co-vary with North
Pacific sea surface temperatures, and are linked to decadal variations in
atmospheric circulation, sea surface temperatures and ocean circulation
throughout the whole Pacific Basin. Such fluctuations have the effect of
modulating the El Niño-Southern Oscillation cycle. Key measures of Pacific
decadal variability are the North Pacific Index (NPI), the Pacific Decadal
Oscillation (PDO) index and the Inter-decadal Pacific Oscillation (IPO)
index, all defined in Box 2.5.
Pacific–North American (PNA) pattern An atmospheric large-scale
wave pattern featuring a sequence of tropospheric high and low pressure
anomalies stretching from the subtropical west Pacific to the east coast of
North America. See PNA pattern index, Box 2.5.
Paleoclimate Climate during periods prior to the development of measuring
instruments, including historic and geologic time, for which only
proxy climate records are available.
Parameterization In climate models, this term refers to the technique
of representing processes that cannot be explicitly resolved at the spatial
or temporal resolution of the model (sub-grid scale processes) by relationships
between model-resolved larger-scale variables and the area- or timeaveraged
effect of such subgrid scale processes.
Percentiles The set of partition values which divides the total population
of a distribution into 100 equal parts, the 50th percentile corresponding
to the median of the population.
Permafrost Ground (soil or rock and included ice and organic material)
that remains at or below 0°C for at least two consecutive years. See also
Near-surface permafrost.
pH pH is a dimensionless measure of the acidity of water (or any solution)
given by its concentration of hydrogen ions (H+). pH is measured on
a logarithmic scale where pH = –log10(H+). Thus, a pH decrease of 1 unit
corresponds to a 10-fold increase in the concentration of H+, or acidity.
Photosynthesis The process by which plants take carbon dioxide from
the air (or bicarbonate in water) to build carbohydrates, releasing oxygen
in the process. There are several pathways of photosynthesis with different
responses to atmospheric carbon dioxide concentrations. See also Carbon
dioxide fertilization.
Plankton Microorganisms living in the upper layers of aquatic systems.
A distinction is made between phytoplankton, which depend on photosynthesis
for their energy supply, and zooplankton, which feed on phytoplankton.
Pleistocene The Pleistocene Epoch is the earlier of two epochs in the
Quaternary System, extending from 2.59 Ma to the beginning of the Holocene
at 11.65 ka.
Pliocene The Plionece Epoch is the last epoch of the Neogene System
and extends from 5.33 Ma to the beginning of the Pleistocene at 2.59 Ma.
Pollen analysis A technique of both relative dating and environmental
reconstruction, consisting of the identification and counting of pollen types
preserved in peat, lake sediments and other deposits. See also Proxy.


Precipitable water The total amount of atmospheric water vapour in
a vertical column of unit cross-sectional area. It is commonly expressed in
terms of the height of the water if completely condensed and collected in
a vessel of the same unit cross section.
Precursors Atmospheric compounds that are not greenhouse gases or
aerosols, but that have an effect on greenhouse gas or aerosol concentrations
by taking part in physical or chemical processes regulating their
production or destruction rates.
Predictability The extent to which future states of a system may be
predicted based on knowledge of current and past states of the system.
Because knowledge of the climate system’s past and current states is generally
imperfect, as are the models that utilize this knowledge to produce a
climate prediction, and because the climate system is inherently nonlinear
and chaotic, predictability of the climate system is inherently limited. Even
with arbitrarily accurate models and observations, there may still be limits
to the predictability of such a nonlinear system (AMS, 2000).
Prediction quality/skill Measures of the success of a prediction
against observationally based information. No single measure can summarize
all aspects of forecast quality and a suite of metrics is considered.
Metrics will differ for forecasts given in deterministic and probabilistic
form. See also Climate prediction.
Pre-industrial See Industrial Revolution.
Probability Density Function (PDF) A probability density function
is a function that indicates the relative chances of occurrence of different
outcomes of a variable. The function integrates to unity over the domain
for which it is defined and has the property that the integral over a subdomain
equals the probability that the outcome of the variable lies within
that sub-domain. For example, the probability that a temperature anomaly
defined in a particular way is greater than zero is obtained from its PDF
by integrating the PDF over all possible temperature anomalies greater
than zero. Probability density functions that describe two or more variables
simultaneously are similarly defined.
Process-based Model Theoretical concepts and computational methods
that represent and simulate the behaviour of real-world systems
derived from a set of functional components and their interactions with
each other and the system environment, through physical and mechanistic
processes occurring over time. See also Climate model.
Projection A projection is a potential future evolution of a quantity or
set of quantities, often computed with the aid of a model. Unlike predictions,
projections are conditional on assumptions concerning, for example,
future socioeconomic and technological developments that may or may
not be realized. See also Climate prediction and Climate projection.
Proxy A proxy climate indicator is a record that is interpreted, using
physical and biophysical principles, to represent some combination of
climate-related variations back in time. Climate-related data derived in
this way are referred to as proxy data. Examples of proxies include pollen
analysis, tree ring records, speleothems, characteristics of corals and various
data derived from marine sediments and ice cores. Proxy-data can be
calibrated to provide quantitative climate information.
Quasi-Biennal Oscillation (QBO) A near-periodic oscillation of the
equatorial zonal wind between easterlies and westerlies in the tropical
stratosphere with a mean period of around 28 months. The alternating
wind maxima descend from the base of the mesosphere down to the tropopause,
and are driven by wave energy that propagates up from the troposphere.
Quaternary The Quaternary System is the latter of three systems that
make up the Cenozoic Era (65 Ma to present), extending from 2.59 Ma to
the present, and includes the Pleistocene and Holocene epochs.
Radiative effect The impact on a radiation flux or heating rate (most
commonly, on the downward flux at the top of atmosphere) caused by
the interaction of a particular constituent with either the infrared or solar
radiation fields through absorption, scattering and emission, relative to
an otherwise identical atmosphere free of that constituent. This quantifies
the impact of the constituent on the climate system. Examples include
the aerosol–radiation interactions, cloud radiative effect, and greenhouse
effect. In this report, the portion of any top-of-atmosphere radiative effect
that is due to anthropogenic or other external influences (e.g., volcanic
eruptions or changes in the sun) is termed the instantaneous radiative forcing.
Radiative forcing Radiative forcing is the change in the net, downward
minus upward, radiative flux (expressed in W m–2) at the tropopause
or top of atmosphere due to a change in an external driver of climate
change, such as, for example, a change in the concentration of carbon dioxide
or the output of the Sun. Sometimes internal drivers are still treated as
forcings even though they result from the alteration in climate, for example
aerosol or greenhouse gas changes in paleoclimates. The traditional radiative
forcing is computed with all tropospheric properties held fixed at their
unperturbed values, and after allowing for stratospheric temperatures, if
perturbed, to readjust to radiative-dynamical equilibrium. Radiative forcing
is called instantaneous if no change in stratospheric temperature is
accounted for. The radiative forcing once rapid adjustments are accounted
for is termed the effective radiative forcing. For the purposes of this report,
radiative forcing is further defined as the change relative to the year 1750
and, unless otherwise noted, refers to a global and annual average value.
Radiative forcing is not to be confused with cloud radiative forcing, which
describes an unrelated measure of the impact of clouds on the radiative
flux at the top of the atmosphere.
Rapid adjustment The response to an agent perturbing the climate
system that is driven directly by the agent, independently of any change
in the global mean surface temperature. For example, carbon dioxide and
aerosols, by altering internal heating and cooling rates within the atmosphere,
can each cause changes to cloud cover and other variables thereby
producing a radiative effect even in the absence of any surface warming or
cooling. Adjustments are rapid in the sense that they begin to occur right
away, before climate feedbacks which are driven by warming (although
some adjustments may still take significant time to proceed to completion,
for example those involving vegetation or ice sheets). It is also called the
rapid response or fast adjustment. For further explanation on the concept,
see Sections 7.1 and 8.1.
Rapid climate change See Abrupt climate change.
Rapid dynamical change (of glaciers or ice sheets) Changes in
glacier or ice sheet mass controlled by changes in flow speed and discharge
rather than by accumulation or ablation. This can result in a rate
of mass change larger than that due to any imbalance between accumulation
and ablation. Rapid dynamical change may be initiated by a climatic
trigger,
such as incursion of warm ocean water beneath an ice shelf, or
thinning of a grounded tidewater terminus, which may lead to reactions
within the glacier system, that may result in rapid ice loss. See also Mass
balance/budget (of glaciers or ice sheets).
Reanalysis Reanalyses are estimates of historical atmospheric temperature
and wind or oceanographic temperature and current, and other
quantities, created by processing past meteorological or oceanographic
data using fixed state-of-the-art weather forecasting or ocean circulation
models with data assimilation techniques. Using fixed data assimilation
avoids effects from the changing analysis system that occur in operational
analyses. Although continuity is improved, global reanalyses still suffer
from changing coverage and biases in the observing systems.


Rebound effect When CO2 is removed from the atmosphere, the CO2
concentration gradient between atmospheric and land/ocean carbon reservoirs
is reduced. This leads to a reduction or reversal in subsequent inherent
rate of removal of CO2 from the atmosphere by natural carbon cycle
processes on land and ocean.
Reconstruction (of climate variable) Approach to reconstructing
the past temporal and spatial characteristics of a climate variable from
predictors. The predictors can be instrumental data if the reconstruction is
used to infill missing data or proxy data if it is used to develop paleoclimate
reconstructions. Various techniques have been developed for this purpose:
linear multivariate regression based methods and nonlinear Bayesian and
analog methods.
Reforestation Planting of forests on lands that have previously
contained forests but that have been converted to some other use. For
a discussion of the term forest and related terms such as afforestation,
reforestation and deforestation, see the IPCC Report on Land Use, Land-
Use Change and Forestry (IPCC, 2000). See also the Report on Definitions
and Methodological Options to Inventory Emissions from Direct Humaninduced
Degradation of Forests and Devegetation of Other Vegetation
Types (IPCC, 2003).
Region A region is a territory characterized by specific geographical
and climatological features. The climate of a region is affected by regional
and local scale features like topography, land use characteristics and lakes,
as well as remote influences from other regions. See also Teleconnection.
Regional Climate Model (RCM) A climate model at higher resolution
over a limited area. Such models are used in downscaling global climate
results over specific regional domains.
Relative humidity The relative humidity specifies the ratio of actual
water vapour pressure to that at saturation with respect to liquid water or
ice at the same temperature. See also Specific humidity.
Relative sea level Sea level measured by a tide gauge with respect to
the land upon which it is situated. See also Mean sea level and Sea level
change.
Representative Concentration Pathways (RCPs) Scenarios that
include time series of emissions and concentrations of the full suite of
greenhouse gases and aerosols and chemically active gases, as well as land
use/land cover (Moss et al., 2008). The word representative signifies that
each RCP provides only one of many possible scenarios that would lead to
the specific radiative forcing characteristics. The term pathway emphasizes
that not only the long-term concentration levels are of interest, but also
the trajectory taken over time to reach that outcome. (Moss et al., 2010).
RCPs usually refer to the portion of the concentration pathway extending
up to 2100, for which Integrated Assessment Models produced
corresponding emission scenarios. Extended Concentration Pathways
(ECPs) describe extensions of the RCPs from 2100 to 2500 that were
calculated using simple rules generated by stakeholder consultations,
and do not represent fully consistent scenarios.
Four RCPs produced from Integrated Assessment Models were selected
from the published literature and are used in the present IPCC Assessment
as a basis for the climate predictions and projections presented
in Chapters 11 to 14:
RCP2.6 One pathway where radiative forcing peaks at approximately
W m–2 before 2100 and then declines (the corresponding ECP
assuming constant emissions after 2100)
RCP4.5 and RCP6.0 Two intermediate stabilization pathways in
which radiative forcing is stabilized at approximately 4.5 W m–2 and
.0 W m–2 after 2100 (the corresponding ECPs assuming constant concentrations
after 2150)
RCP8.5 One high pathway for which radiative forcing reaches greater
than 8.5 W m–2 by 2100 and continues to rise for some amount of
time (the corresponding ECP assuming constant emissions after 2100
and constant concentrations after 2250)
For further description of future scenarios, see Box 1.1.
Reservoir A component of the climate system, other than the atmosphere,
which has the capacity to store, accumulate or release a substance
of concern, for example, carbon, a greenhouse gas or a precursor. Oceans,
soils and forests are examples of reservoirs of carbon. Pool is an equivalent
term (note that the definition of pool often includes the atmosphere). The
absolute quantity of the substance of concern held within a reservoir at a
specified time is called the stock.
Resolution In climate models, this term refers to the physical distance
(metres or degrees) between each point on the grid used to compute the
equations. Temporal resolution refers to the time step or time elapsed
between each model computation of the equations.
Respiration The process whereby living organisms convert organic
matter to carbon dioxide, releasing energy and consuming molecular
oxygen.
Response time The response time or adjustment time is the time
needed for the climate system or its components to re-equilibrate to a
new state, following a forcing resulting from external processes. It is very
different for various components of the climate system. The response time
of the troposphere is relatively short, from days to weeks, whereas the
stratosphere reaches equilibrium on a time scale of typically a few months.
Due to their large heat capacity, the oceans have a much longer response
time: typically decades, but up to centuries or millennia. The response
time of the strongly coupled surface–troposphere system is, therefore,
slow compared to that of the stratosphere, and mainly determined by the
oceans. The biosphere may respond quickly (e.g., to droughts), but also
very slowly to imposed changes. See lifetime for a different definition of
response time pertinent to the rate of processes affecting the concentration
of trace gases.
Return period An estimate of the average time interval between
occurrences of an event (e.g., flood or extreme rainfall) of (or below/above)
a defined size or intensity. See also Return value.
Return value The highest (or, alternatively, lowest) value of a given
variable, on average occurring once in a given period of time (e.g., in 10
years). See also Return period.
River discharge See Streamflow.
Runoff That part of precipitation that does not evaporate and is not
transpired, but flows through the ground or over the ground surface and
returns to bodies of water. See also Hydrological cycle.
Scenario A plausible description of how the future may develop based
on a coherent and internally consistent set of assumptions about key driving
forces (e.g., rate of technological change, prices) and relationships.
Note that scenarios are neither predictions nor forecasts, but are useful to
provide a view of the implications of developments and actions. See also
Climate scenario, Emission scenario, Representative Concentration Pathways
and SRES scenarios.
Sea ice Ice found at the sea surface that has originated from the freezing
of seawater. Sea ice may be discontinuous pieces (ice floes) moved on
the ocean surface by wind and currents (pack ice), or a motionless sheet
attached to the coast (land-fast ice). Sea ice concentration is the fraction
of the ocean covered by ice. Sea ice less than one year old is called firstyear
ice. Perennial ice is sea ice that survives at least one summer. It may
be subdivided into second-year ice and multi-year ice, where multiyear ice
has survived at least two summers.


Sea level change Sea level can change, both globally and locally due
to (1) changes in the shape of the ocean basins, (2) a change in ocean
volume as a result of a change in the mass of water in the ocean, and (3)
changes in ocean volume as a result of changes in ocean water density.
Global mean sea level change resulting from change in the mass of the
ocean is called barystatic. The amount of barystatic sea level change due to
the addition or removal of a mass of water is called its sea level equivalent
(SLE). Sea level changes, both globally and locally, resulting from changes
in water density are called steric. Density changes induced by temperature
changes only are called thermosteric, while density changes induced
by salinity changes are called halosteric. Barystatic and steric sea level
changes do not include the effect of changes in the shape of ocean basins
induced by the change in the ocean mass and its distribution. See also
Relative Sea Level and Thermal expansion.
Sea level equivalent (SLE) The sea level equivalent of a mass of
water (ice, liquid or vapour) is that mass, converted to a volume using a
density of 1000 kg m–3, and divided by the present-day ocean surface area
of 3.625 × 1014 m2. Thus, 362.5 Gt of water mass added to the ocean will
cause 1 mm of global mean sea level rise. See also Sea level change.
Seasonally frozen ground See Frozen ground.
Sea surface temperature (SST) The sea surface temperature is the
subsurface bulk temperature in the top few metres of the ocean, measured
by ships, buoys and drifters. From ships, measurements of water samples in
buckets were mostly switched in the 1940s to samples from engine intake
water. Satellite measurements of skin temperature (uppermost layer; a
fraction of a millimetre thick) in the infrared or the top centimetre or so in
the microwave are also used, but must be adjusted to be compatible with
the bulk temperature.
Semi-direct (aerosol) effect See Aerosol–radiation interaction.
Semi-empirical model Model in which calculations are based on a
combination of observed associations between variables and theoretical
considerations relating variables through fundamental principles (e.g.,
conservation of energy). For example, in sea level studies, semi-empirical
models refer specifically to transfer functions formulated to project future
global mean sea level change, or contributions to it, from future global
mean surface temperature change or radiative forcing.
Sensible heat flux The turbulent or conductive flux of heat from the
Earth’s surface to the atmosphere that is not associated with phase changes
of water; a component of the surface energy budget.
Sequestration See Uptake.
Shortwave radiation See Solar radiation.
Significant wave height The average trough-to-crest height of the
highest one third of the wave heights (sea and swell) occurring in a particular
time period.
Sink Any process, activity or mechanism that removes a greenhouse
gas, an aerosol or a precursor of a greenhouse gas or aerosol from the
atmosphere.
Slab-ocean model A simplified representation in a climate model of
the ocean as a motionless layer of water with a depth of 50 to 100 m.
Climate models with a slab ocean can be used only for estimating the equilibrium
response of climate to a given forcing, not the transient evolution
of climate. See also Equilibrium and transient climate experiment.
Snow cover extent The areal extent of snow covered ground.
Snow water equivalent (SWE) The depth of liquid water that would
result if a mass of snow melted completely.
Soil moisture Water stored in the soil in liquid or frozen form.
Soil temperature The temperature of the soil. This can be measured or
modelled at multiple levels within the depth of the soil.
Solar activity General term describing a variety of magnetic phenomena
on the Sun such as sunspots, faculae (bright areas), and flares (emission
of high-energy particles). It varies on time scales from minutes to millions
of years. See also Solar cycle.
Solar (‘11-year’) cycle A quasi-regular modulation of solar activity
with varying amplitude and a period of between 8 and 14 years.
Solar radiation Electromagnetic radiation emitted by the Sun with a
spectrum close to the one of a black body with a temperature of 5770 K.
The radiation peaks in visible wavelengths. When compared to the terrestrial
radiation it is often referred to as shortwave radiation. See also
Insolation and Total solar irradiance (TSI).
Solar Radiation Management (SRM) Solar Radiation Management
refers to the intentional modification of the Earth’s shortwave radiative
budget with the aim to reduce climate change according to a given metric
(e.g., surface temperature, precipitation, regional impacts, etc). Artificial
injection of stratospheric aerosols and cloud brightening are two examples
of SRM techniques. Methods to modify some fast-responding elements of
the longwave radiative budget (such as cirrus clouds), although not strictly
speaking SRM, can be related to SRM. SRM techniques do not fall within
the usual definitions of mitigation and adaptation (IPCC, 2012, p. 2). See
also Solar radiation, Carbon Dioxide Removal (CDR) and Geoengineering.
Solubility pump Solubility pump is an important physicochemical process
that transports dissolved inorganic carbon from the ocean’s surface
to its interior. This process controls the inventory of carbon in the ocean.
The solubility of gaseous carbon dioxide can alter carbon dioxide concentrations
in the oceans and the overlying atmosphere. See also Biological
pump.
Source Any process, activity or mechanism that releases a greenhouse
gas, an aerosol or a precursor of a greenhouse gas or aerosol into the
atmosphere.
Southern Annular Mode (SAM) The leading mode of variability of
Southern Hemisphere geopotential height, which is associated with shifts
in the latitude of the midlatitude jet. See SAM Index, Box 2.5.
Southern Oscillation See El Niño-Southern Oscillation (ENSO).
South Pacific Convergence Zone (SPCZ) A band of low-level convergence,
cloudiness and precipitation ranging from the west Pacific warm
pool south-eastwards towards French Polynesia, which is one of the most
significant features of subtropical Southern Hemisphere climate. It shares
some characteristics with the ITCZ, but is more extratropical in nature,
especially east of the Dateline.
Spatial and temporal scales Climate may vary on a large range of
spatial and temporal scales. Spatial scales may range from local (less than
000 km2), through regional (100 000 to 10 million km2) to continental
(10 to 100 million km2). Temporal scales may range from seasonal to geological
(up to hundreds of millions of years).
Specific humidity The specific humidity specifies the ratio of the mass
of water vapour to the total mass of moist air. See also Relative humidity.
SRES scenarios SRES scenarios are emission scenarios developed by
Nakićenović and Swart (2000) and used, among others, as a basis for some
of the climate projections shown in Chapters 9 to 11 of IPCC (2001) and
Chapters 10 and 11 of IPCC (2007). The following terms are relevant for a
better understanding of the structure and use of the set of SRES scenarios:
Scenario family Scenarios that have a similar demographic, societal,
economic and technical change storyline. Four scenario families
comprise the SRES scenario set: A1, A2, B1 and B2.


Illustrative Scenario A scenario that is illustrative for each of
the six scenario groups reflected in the Summary for Policymakers of
Nakićenović and Swart (2000). They include four revised marker scenarios
for the scenario groups A1B, A2, B1, B2 and two additional scenarios
for the A1FI and A1T groups. All scenario groups are equally sound.
Marker Scenario A scenario that was originally posted in draft form
on the SRES website to represent a given scenario family. The choice of
markers was based on which of the initial quantifications best reflected
the storyline, and the features of specific models. Markers are no more
likely than other scenarios, but are considered by the SRES writing team
as illustrative of a particular storyline. They are included in revised form
in Nakićenović and Swart (2000). These scenarios received the closest
scrutiny of the entire writing team and via the SRES open process. Scenarios
were also selected to illustrate the other two scenario groups.
Storyline A narrative description of a scenario (or family of scenarios),
highlighting the main scenario characteristics, relationships
between key driving forces and the dynamics of their evolution.
Steric See Sea level change.
Stock See Reservoir.
Storm surge The temporary increase, at a particular locality, in the
height of the sea due to extreme meteorological conditions (low atmospheric
pressure and/or strong winds). The storm surge is defined as being
the excess above the level expected from the tidal variation alone at that
time and place.
Storm tracks Originally, a term referring to the tracks of individual
cyclonic weather systems, but now often generalized to refer to the main
regions where the tracks of extratropical disturbances occur as sequences
of low (cyclonic) and high (anticyclonic) pressure systems.
Stratosphere The highly stratified region of the atmosphere above the
troposphere extending from about 10 km (ranging from 9 km at high latitudes
to 16 km in the tropics on average) to about 50 km altitude.
Streamflow Water flow within a river channel, for example expressed
in m3 s–1. A synonym for river discharge.
Subduction Ocean process in which surface waters enter the ocean
interior from the surface mixed layer through Ekman pumping and lateral
advection. The latter occurs when surface waters are advected to a region
where the local surface layer is less dense and therefore must slide below
the surface layer, usually with no change in density.
Sunspots Dark areas on the Sun where strong magnetic fields reduce
the convection causing a temperature reduction of about 1500 K compared
to the surrounding regions. The number of sunspots is higher during
periods of higher solar activity, and varies in particular with the solar cycle.
Surface layer See Atmospheric boundary layer.
Surface temperature See Global mean surface temperature, Land
surface air temperature and Sea surface temperature.
Talik A layer of year-round unfrozen ground that lies in permafrost
areas.
Teleconnection A statistical association between climate variables at
widely separated, geographically-fixed spatial locations. Teleconnections
are caused by large spatial structures such as basin-wide coupled modes
of ocean–atmosphere variability, Rossby wave-trains, mid-latitude jets and
storm tracks, etc. See also Teleconnection pattern.
Teleconnection pattern A correlation map obtained by calculating
the correlation between variables at different spatial locations and a climate
index. It is the special case of a climate pattern obtained for standardized
variables and a standardized climate index, that is, the variables
and index are each centred and scaled to have zero mean and unit variance.
One-point teleconnection maps are made by choosing a variable at
one of the locations to be the climate index. See also Teleconnection.
Terrestrial radiation Radiation emitted by the Earth’s surface, the
atmosphere and the clouds. It is also known as thermal infrared or longwave
radiation, and is to be distinguished from the near-infrared radiation
that is part of the solar spectrum. Infrared radiation, in general, has a
distinctive range of wavelengths (spectrum) longer than the wavelength of
the red light in the visible part of the spectrum. The spectrum of terrestrial
radiation is almost entirely distinct from that of shortwave or solar radiation
because of the difference in temperature between the Sun and the
Earth–atmosphere system. See also Outgoing longwave radiation.
Thermal expansion In connection with sea level, this refers to the
increase in volume (and decrease in density) that results from warming
water. A warming of the ocean leads to an expansion of the ocean volume
and hence an increase in sea level. See also Sea level change.
Thermocline The layer of maximum vertical temperature gradient in
the ocean, lying between the surface ocean and the abyssal ocean. In subtropical
regions, its source waters are typically surface waters at higher
latitudes that have subducted (see Subduction) and moved equatorward.
At high latitudes, it is sometimes absent, replaced by a halocline, which is
a layer of maximum vertical salinity gradient.
Thermohaline circulation (THC) Large-scale circulation in the ocean
that transforms low-density upper ocean waters to higher-density intermediate
and deep waters and returns those waters back to the upper ocean.
The circulation is asymmetric, with conversion to dense waters in restricted
regions at high latitudes and the return to the surface involving slow
upwelling and diffusive processes over much larger geographic regions.
The THC is driven by high densities at or near the surface, caused by cold
temperatures and/or high salinities, but despite its suggestive though
common name, is also driven by mechanical forces such as wind and tides.
Frequently, the name THC has been used synonymously with Meridional
Overturning Circulation.
Thermokarst The process by which characteristic landforms result from
the thawing of ice-rich permafrost or the melting of massive ground ice.
Thermosteric See Sea level change.
Tide gauge A device at a coastal or deep-sea location that continuously
measures the level of the sea with respect to the adjacent land. Time
averaging of the sea level so recorded gives the observed secular changes
of the relative sea level.
Tipping point In climate, a hypothesized critical threshold when global
or regional climate changes from one stable state to another stable state.
The tipping point event may be irreversible. See also Irreversibility.
Total solar irradiance (TSI) The total amount of solar radiation in
watts per square metre received outside the Earth’s atmosphere on a
surface
normal to the incident radiation, and at the Earth’s mean distance
from the Sun.
Reliable measurements of solar radiation can only be made from space
and the precise record extends back only to 1978. The generally accepted
value is 1368 W m−2 with an accuracy of about 0.2%. It has recently
been estimated to 1360.8 ± 0.5 W m–2 for the solar minimum of 2008.
Variations of a few tenths of a percent are common, usually associated
with the passage of sunspots across the solar disk. The solar cycle
variation of TSI is of the order of 0.1% (AMS, 2000). Changes in the
ultraviolet part of the spectrum during a solar cycle are comparatively
larger (percent) than in TSI. See also Insolation.


Transient climate response See Climate sensitivity.
Transient climate response to cumulative CO2 emissions (TCRE)
The transient global average surface temperature change per unit cumulated
CO2 emissions, usually 1000 PgC. TCRE combines both information
on the airborne fraction of cumulated CO2 emissions (the fraction of the
total CO2 emitted that remains in the atmosphere), and on the transient
climate response (TCR).
Tree rings Concentric rings of secondary wood evident in a cross section
of the stem of a woody plant. The difference between the dense, smallcelled
late wood of one season and the wide-celled early wood of the
following spring enables the age of a tree to be estimated, and the ring
widths or density can be related to climate parameters such as temperature
and precipitation. See also Proxy.
Trend In this report, the word trend designates a change, generally
monotonic in time, in the value of a variable.
Tropopause The boundary between the troposphere and the stratosphere.
Troposphere The lowest part of the atmosphere, from the surface to
about 10 km in altitude at mid-latitudes (ranging from 9 km at high latitudes
to 16 km in the tropics on average), where clouds and weather phenomena
occur. In the troposphere, temperatures generally decrease with
height. See also Stratosphere.
Turnover time See Lifetime.
Uncertainty A state of incomplete knowledge that can result from a
lack of information or from disagreement about what is known or even
knowable. It may have many types of sources, from imprecision in the data
to ambiguously defined concepts or terminology, or uncertain projections
of human behaviour. Uncertainty can therefore be represented by quantitative
measures (e.g., a probability density function) or by qualitative statements
(e.g., reflecting the judgment of a team of experts) (see Moss and
Schneider, 2000; Manning et al., 2004; Mastrandrea et al., 2010). See also
Confidence and Likelihood.
United Nations Framework Convention on Climate Change
(UNFCCC) The Convention was adopted on 9 May 1992 in New York
and signed at the 1992 Earth Summit in Rio de Janeiro by more than 150
countries and the European Community. Its ultimate objective is the ‘stabilisation
of greenhouse gas concentrations in the atmosphere at a level
that would prevent dangerous anthropogenic interference with the climate
system’. It contains commitments for all Parties. Under the Convention,
Parties included in Annex I (all OECD countries and countries with economies
in transition) aim to return greenhouse gas emissions not controlled
by the Montreal Protocol to 1990 levels by the year 2000. The convention
entered in force in March 1994. In 1997, the UNFCCC adopted the Kyoto
Protocol.
Uptake The addition of a substance of concern to a reservoir. The
uptake of carbon containing substances, in particular carbon dioxide, is
often called (carbon) sequestration.
Urban heat island (UHI) The relative warmth of a city compared with
surrounding rural areas, associated with changes in runoff, effects on heat
retention, and changes in surface albedo.
Ventilation The exchange of ocean properties with the atmospheric
surface layer such that property concentrations are brought closer to equilibrium
values with the atmosphere (AMS, 2000), and the processes that
propagate these properties into the ocean interior.
Volatile Organic Compounds (VOC) Important class of organic
chemical air pollutants that are volatile at ambient air conditions. Other
terms used to represent VOCs are hydrocarbons (HCs), reactive organic
gases (ROGs) and non-methane volatile organic compounds (NMVOCs).
NMVOCs are major contributors (together with NOx and CO) to the formation
of photochemical oxidants such as ozone.
Walker Circulation Direct thermally driven zonal overturning circulation
in the atmosphere over the tropical Pacific Ocean, with rising air in the
western and sinking air in the eastern Pacific.
Warm days/warm nights Days where maximum temperature, or
nights where minimum temperature, exceeds the 90th percentile, where
the respective temperature distributions are generally defined with respect
to the 1961–1990 reference period. For the corresponding indices, see Box
.4.
Warm spell A period of abnormally hot weather. For the corresponding
indices, see Box 2.4. See also Heat wave.
Water cycle See Hydrological cycle.
Water mass A body of ocean water with identifiable properties (temperature,
salinity, density, chemical tracers) resulting from its unique formation
process. Water masses are often identified through a vertical or
horizontal extremum of a property such as salinity. North Pacific Intermediate
Water (NPIW) and Antarctic Intermediate Water (AAIW) are examples
of water masses.
Weathering The gradual removal of atmospheric CO2 through dissolution
of silicate and carbonate rocks. Weathering may involve physical
processes (mechanical weathering) or chemical activity (chemical weathering).
Well-mixed greenhouse gas See Greenhouse gas.
Younger Dryas A period 12.85 to 11.65 ka (thousand years before
), during the deglaciation, characterized by a temporary return to
colder conditions in many locations, especially around the North Atlantic.
Annexes


I
ANNEX


Glossary
This glossary defines some specific terms as the Lead Authors
intend them to be interpreted in the context of this report. Glossary
entries (highlighted in bold) are by preference subjects; a
main entry can contain subentries, in bold and italic, for example,
Primary Energy is defined under the entry Energy. Blue, italicized
words indicate that the term is defined in the Glossary. The
glossary is followed by a list of acronyms and chemical symbols.
Please refer to Annex II for standard units, prefixes, and unit conversion
(Section A.II.1) and for regions and country groupings
(Section A.II.2).
Abrupt climate change: A large-scale change in the climate system
that takes place over a few decades or less, persists (or is anticipated
to persist) for at least a few decades, and causes substantial disruptions
in human and natural systems. See also Climate threshold.
Adaptability: See Adaptive capacity.
Adaptation: The process of adjustment to actual or expected climate
and its effects. In human systems, adaptation seeks to moderate or
avoid harm or exploit beneficial opportunities. In some natural systems,
human intervention may facilitate adjustment to expected climate
and its effects.1
Adaptation Fund: A Fund established under the Kyoto Protocol in
and officially launched in 2007. The Fund finances adaptation
projects and programmes in developing countries that are Parties to
the Kyoto Protocol. Financing comes mainly from sales of Certified
Emissions Reductions (CERs) and a share of proceeds amounting to
% of the value of CERs issued each year for Clean Development
Mechanism (CDM) projects. The Adaptation Fund can also receive
funds from government, private sector, and individuals.
Adaptive capacity: The ability of systems, institutions, humans, and
other organisms to adjust to potential damage, to take advantage of
opportunities, or to respond to consequences.2
Additionality: Mitigation projects (e. g., under the Kyoto Mechanisms),
mitigation policies, or climate finance are additional if they go
beyond a business-as-usual level, or baseline. Additionality is required
to guarantee the environmental integrity of project-based offset mechanisms,
but difficult to establish in practice due to the counterfactual
nature of the baseline.
Reflecting progress in science, this glossary entry differs in breadth and focus from
the entry used in the Fourth Assessment Report and other IPCC reports.
This glossary entry builds from definitions used in previous IPCC reports and the
Millennium Ecosystem Assessment (MEA, 2005).
Adverse side-effects: The negative effects that a policy or measure
aimed at one objective might have on other objectives, without yet
evaluating the net effect on overall social welfare. Adverse side-effects
are often subject to uncertainty and depend on, among others, local
circumstances and implementation practices. See also Co-benefits,
Risk, and Risk tradeoff.
Aerosol: A suspension of airborne solid or liquid particles, with a
typical size between a few nanometres and 10 μm that reside in the
atmosphere for at least several hours. For convenience the term aerosol,
which includes both the particles and the suspending gas, is often
used in this report in its plural form to mean aerosol particles. Aerosols
may be of either natural or anthropogenic origin. Aerosols may influence
climate in several ways: directly through scattering and absorbing
radiation, and indirectly by acting as cloud condensation nuclei or ice
nuclei, modifying the optical properties and lifetime of clouds. Atmospheric
aerosols, whether natural or anthropogenic, originate from two
different pathways: emissions of primary particulate matter (PM), and
formation of secondary PM from gaseous precursors. The bulk of aerosols
are of natural origin. Some scientists use group labels that refer
to the chemical composition, namely: sea salt, organic carbon, black
carbon (BC), mineral species (mainly desert dust), sulphate, nitrate, and
ammonium. These labels are, however, imperfect as aerosols combine
particles to create complex mixtures. See also Short-lived climate pollutants
(SLCPs).
Afforestation: Planting of new forests on lands that historically have
not contained forests. Afforestation projects are eligible under a number
of schemes including, among others, Joint Implementation (JI) and
the Clean Development Mechanism (CDM) under the Kyoto Protocol
for which particular criteria apply (e. g., proof must be given that the
land was not forested for at least 50 years or converted to alternative
uses before 31 December 1989).
For a discussion of the term forest and related terms such as afforestation,
reforestation and deforestation, see the IPCC Special Report on
Land Use, Land-Use Change and Forestry (IPCC, 2000). See also the
report on Definitions and Methodological Options to Inventory Emissions
from Direct Human-induced Degradation of Forests and Devegetation
of Other Vegetation Types (IPCC, 2003).
Agreement: In this report, the degree of agreement is the level of concurrence
in the literature on a particular finding as assessed by the
authors. See also Evidence, Confidence, Likelihood, and Uncertainty.
Agricultural emissions: See Emissions.
Agriculture, Forestry and Other Land Use (AFOLU): Agriculture,
Forestry and Other Land Use plays a central role for food security and
sustainable development (SD). The main mitigation options within
AFOLU involve one or more of three strategies: prevention of emissions
to the atmosphere by conserving existing carbon pools in soils
or vegetation or by reducing emissions of methane (CH4) and nitrous


oxide (N2O); sequestration — increasing the size of existing carbon
pools, and thereby extracting carbon dioxide (CO2) from the atmosphere;
and substitution — substituting biological products for fossil
fuels or energy-intensive products, thereby reducing CO2 emissions.
Demand-side measures (e. g., by reducing losses and wastes of food,
changes in human diet, or changes in wood consumption) may also
play a role. FOLU (Forestry and Other Land Use) — also referred to as
LULUCF (Land use, land-use change, and forestry) — is the subset of
AFOLU emissions and removals of greenhouse gases (GHGs) resulting
from direct human-induced land use, land-use change and forestry
activities excluding agricultural emissions.
Albedo: The fraction of solar radiation reflected by a surface or object,
often expressed as a percentage. Snow-covered surfaces have a high
albedo, the albedo of soils ranges from high to low, and vegetationcovered
surfaces and oceans have a low albedo. The earth’s planetary
albedo varies mainly through varying cloudiness, snow, ice, leaf area
and land cover changes.
Alliance of Small Island States (AOSIS): The Alliance of Small Island
States (AOSIS) is a coalition of small islands and low-lying coastal
countries with a membership of 44 states and observers that share
and are active in global debates and negotiations on the environment,
especially those related to their vulnerability to the adverse effects of
climate change. Established in 1990, AOSIS acts as an ad-hoc lobby and
negotiating voice for small island development states (SIDS) within the
United Nations including the United Nations Framework Convention
on Climate Change (UNFCCC) climate change negotiations.
Ancillary benefits: See Co-benefits.
Annex I Parties / countries: The group of countries listed in Annex
I to the United Nations Framework Convention on Climate Change
(UNFCCC). Under Articles 4.2 (a) and 4.2 (b) of the UNFCCC, Annex
I Parties were committed to adopting national policies and measures
with the non-legally binding aim to return their greenhouse gas (GHG)
emissions to 1990 levels by 2000. The group is largely similar to the
Annex B Parties to the Kyoto Protocol that also adopted emissions
reduction targets for 2008 – 2012. By default, the other countries are
referred to as Non-Annex I Parties.
Annex II Parties / countries: The group of countries listed in Annex
II to the United Nations Framework Convention on Climate Change
(UNFCCC). Under Article 4 of the UNFCCC, these countries have a special
obligation to provide financial resources to meet the agreed full
incremental costs of implementing measures mentioned under Article
, paragraph 1. They are also obliged to provide financial resources,
including for the transfer of technology, to meet the agreed incremental
costs of implementing measures covered by Article 12, paragraph
and agreed between developing country Parties and international
entities referred to in Article 11 of the UNFCCC. This group of countries
shall also assist countries that are particularly vulnerable to the
adverse effects of climate change.
Annex B Parties / countries: The subset of Annex I Parties that have
accepted greenhouse gas (GHG) emission reduction targets for the
period 2008 – 2012 under Article 3 of the Kyoto Protocol. By default,
the other countries are referred to as Non-Annex I Parties.
Anthropogenic emissions: See Emissions.
Assigned Amount (AA): Under the Kyoto Protocol, the AA is the
quantity of greenhouse gas (GHG) emissions that an Annex B country
has agreed to as its cap on its emissions in the first five-year commitment
period (2008 – 2012). The AA is the country’s total GHG emissions
in 1990 multiplied by five (for the five-year commitment period) and by
the percentage it agreed to as listed in Annex B of the Kyoto Protocol
(e. g., 92 % for the EU). See also Assigned Amount Unit (AAU).
Assigned Amount Unit (AAU): An AAU equals 1 tonne (metric ton) of
CO2-equivalent emissions calculated using the Global Warming Potential
(GWP). See also Assigned Amount (AA).
Atmosphere: The gaseous envelope surrounding the earth, divided
into five layers — the troposphere which contains half of the earth’s
atmosphere, the stratosphere, the mesosphere, the thermosphere,
and the exosphere, which is the outer limit of the atmosphere. The
dry atmosphere consists almost entirely of nitrogen (78.1 % volume
mixing ratio) and oxygen (20.9 % volume mixing ratio), together
with a number of trace gases, such as argon (0.93 % volume mixing
ratio), helium and radiatively active greenhouse gases (GHGs) such
as carbon dioxide (CO2) (0.035 % volume mixing ratio) and ozone
(O3). In addition, the atmosphere contains the GHG water vapour
(H2O), whose amounts are highly variable but typically around 1 %
volume mixing ratio. The atmosphere also contains clouds and aerosols.
Backstop technology: Models estimating mitigation often use an
arbitrary carbon-free technology (often for power generation) that
might become available in the future in unlimited supply over the horizon
of the model. This allows modellers to explore the consequences
and importance of a generic solution technology without becoming
enmeshed in picking the actual technology. This ‘backstop’ technology
might be a nuclear technology, fossil technology with Carbon Dioxide
Capture and Storage (CCS), solar energy, or something as yet unimagined.
The backstop technology is typically assumed either not to currently
exist, or to exist only at higher costs relative to conventional
alternatives.
Banking (of Assigned Amount Units) : Any transfer of Assigned
Amount Units (AAUs) from an existing period into a future commitment
period. According to the Kyoto Protocol [Article 3 (13)], Parties
included in Annex I to the United Nations Framework Convention on
Climate Change (UNFCCC) may save excess AAUs from the first commitment
period for compliance with their respective cap in subsequent
commitment periods (post-2012).


Baseline / reference: The state against which change is measured.
In the context of transformation pathways, the term ‘baseline scenarios’
refers to scenarios that are based on the assumption that no
mitigation policies or measures will be implemented beyond those that
are already in force and / or are legislated or planned to be adopted.
Baseline scenarios are not intended to be predictions of the future,
but rather counterfactual constructions that can serve to highlight
the level of emissions that would occur without further policy effort.
Typically, baseline scenarios are then compared to mitigation scenarios
that are constructed to meet different goals for greenhouse gas
(GHG) emissions, atmospheric concentrations, or temperature change.
The term ‘baseline scenario’ is used interchangeably with ‘reference
scenario’ and ‘no policy scenario’. In much of the literature the term
is also synonymous with the term ‘business-as-usual (BAU) scenario,’
although the term ‘BAU’ has fallen out of favour because the idea of
‘business-as-usual’ in century-long socioeconomic projections is hard
to fathom. See also Climate scenario, Emission scenario, Representative
concentration pathways (RCPs), Shared socio-economic pathways,
Socio-economic scenarios, SRES scenarios, and Stabilization.
Behaviour: In this report, behaviour refers to human decisions and
actions (and the perceptions and judgments on which they are based)
that directly or indirectly influence mitigation or the effects of potential
climate change impacts (adaptation). Human decisions and actions
are relevant at different levels, from international, national, and subnational
actors, to NGO, tribe, or firm-level decision makers, to communities,
households, and individual citizens and consumers. See also
Behavioural change and Drivers of behaviour.
Behavioural change: In this report, behavioural change refers to
alteration of human decisions and actions in ways that mitigate climate
change and / or reduce negative consequences of climate change
impacts. See also Drivers of behaviour.
Biochar: Biomass stabilization can be an alternative or enhancement
to bioenergy in a land-based mitigation strategy. Heating biomass
with exclusion of air produces a stable carbon-rich co-product (char).
When added to soil a system, char creates a system that has greater
abatement potential than typical bioenergy. The relative benefit of biochar
systems is increased if changes in crop yield and soil emissions of
methane (CH4) and nitrous oxide (N2O) are taken into account.
Biochemical oxygen demand (BOD): The amount of dissolved oxygen
consumed by micro-organisms (bacteria) in the bio-chemical oxidation
of organic and inorganic matter in wastewater. See also Chemical
oxygen demand (COD).
Biodiversity: The variability among living organisms from terrestrial,
marine, and other ecosystems. Biodiversity includes variability at the
genetic, species, and ecosystem levels.3
This glossary entry builds from definitions used in the Global Biodiversity Assessment
(Heywood, 1995) and the Millennium Ecosystem Assessment (MEA, 2005).
Bioenergy: Energy derived from any form of biomass such as recently
living organisms or their metabolic by-products.
Bioenergy and Carbon Dioxide Capture and Storage (BECCS):
The application of Carbon Dioxide Capture and Storage (CCS) technology
to bioenergy conversion processes. Depending on the total lifecycle
emissions, including total marginal consequential effects (from
indirect land use change (iLUC) and other processes), BECCS has the
potential for net carbon dioxide (CO2) removal from the atmosphere.
See also Sequestration.
Bioethanol: Ethanol produced from biomass (e. g., sugar cane or
corn). See also Biofuel.
Biofuel: A fuel, generally in liquid form, produced from organic matter
or combustible oils produced by living or recently living plants.
Examples of biofuel include alcohol (bioethanol), black liquor from the
paper-manufacturing process, and soybean oil.
First-generation manufactured biofuel: First-generation manufactured
biofuel is derived from grains, oilseeds, animal fats, and
waste vegetable oils with mature conversion technologies.
Second-generation biofuel: Second-generation biofuel uses
non-traditional biochemical and thermochemical conversion processes
and feedstock mostly derived from the lignocellulosic fractions
of, for example, agricultural and forestry residues, municipal
solid waste, etc.
Third-generation biofuel: Third-generation biofuel would
be derived from feedstocks such as algae and energy crops by
advanced processes still under development.
These second- and third-generation biofuels produced through new
processes are also referred to as next-generation or advanced biofuels,
or advanced biofuel technologies.
Biomass: The total mass of living organisms in a given area or volume;
dead plant material can be included as dead biomass. In the context of
this report, biomass includes products, by-products, and waste of biological
origin (plants or animal matter), excluding material embedded
in geological formations and transformed to fossil fuels or peat.
Traditional biomass: Traditional biomass refers to the biomass
— fuelwood, charcoal, agricultural residues, and animal
dung — used with the so-called traditional technologies such as
open fires for cooking, rustic kilns and ovens for small industries.
Widely used in developing countries, where about 2.6 billion people
cook with open wood fires, and hundreds of thousands smallindustries.
The use of these rustic technologies leads to high pollution
levels and, in specific circumstances, to forest degradation
and deforestation. There are many successful initiatives around
the world to make traditional biomass burned more efficiently


and cleanly using efficient cookstoves and kilns. This last use of
traditional biomass is sustainable and provides large health and
economic benefits to local populations in developing countries,
particularly in rural and peri-urban areas.
Modern biomass: All biomass used in high efficiency conversion
systems.
Biomass burning: Biomass burning is the burning of living and dead
vegetation.
Biosphere (terrestrial and marine): The part of the earth system
comprising all ecosystems and living organisms, in the atmosphere, on
land (terrestrial biosphere) or in the oceans (marine biosphere), including
derived dead organic matter, such as litter, soil organic matter and
oceanic detritus.
Black carbon (BC): Operationally defined aerosol species based on
measurement of light absorption and chemical reactivity and / or thermal
stability. It is sometimes referred to as soot. BC is mostly formed
by the incomplete combustion of fossil fuels, biofuels, and biomass
but it also occurs naturally. It stays in the atmosphere only for days or
weeks. It is the most strongly light-absorbing component of particulate
matter (PM) and has a warming effect by absorbing heat into the
atmosphere and reducing the albedo when deposited on ice or snow.
Burden sharing (also referred to as Effort sharing): In the context
of mitigation, burden sharing refers to sharing the effort of reducing
the sources or enhancing the sinks of greenhouse gases (GHGs) from
historical or projected levels, usually allocated by some criteria, as well
as sharing the cost burden across countries.
Business-as-usual (BAU): See Baseline / reference.
Cancún Agreements: A set of decisions adopted at the 16th Session
of the Conference of the Parties (COP) to the United Nations Framework
Convention on Climate Change (UNFCCC), including the following,
among others: the newly established Green Climate Fund (GCF),
a newly established technology mechanism, a process for advancing
discussions on adaptation, a formal process for reporting mitigation
commitments, a goal of limiting global mean surface temperature
increase to 2 °C, and an agreement on MRV — Measuring, Reporting
and Verifying for those countries that receive international support for
their mitigation efforts.
Cancún Pledges: During 2010, many countries submitted their existing
plans for controlling greenhouse gas (GHG) emissions to the Climate
Change Secretariat and these proposals have now been formally
acknowledged under the United Nations Framework Convention on
Climate Change (UNFCCC). Developed countries presented their plans
in the shape of economy-wide targets to reduce emissions, mainly
up to 2020, while developing countries proposed ways to limit their
growth of emissions in the shape of plans of action.
Cap, on emissions: Mandated restraint as an upper limit on emissions
within a given period. For example, the Kyoto Protocol mandates
emissions caps in a scheduled timeframe on the anthropogenic greenhouse
gas (GHG) emissions released by Annex B countries.
Carbon budget: The area under a greenhouse gas (GHG) emissions
trajectory that satisfies assumptions about limits on cumulative emissions
estimated to avoid a certain level of global mean surface temperature
rise. Carbon budgets may be defined at the global level, national,
or sub-national levels.
Carbon credit: See Emission allowance.
Carbon cycle: The term used to describe the flow of carbon (in various
forms, e. g., as carbon dioxide) through the atmosphere, ocean, terrestrial
and marine biosphere and lithosphere. In this report, the reference
unit for the global carbon cycle is GtC or GtCO2 (1 GtC corresponds
to 3.667 GtCO2). Carbon is the major chemical constituent of most
organic matter and is stored in the following major reservoirs: organic
molecules in the biosphere, carbon dioxide (CO2) in the atmosphere,
organic matter in the soils, in the lithosphere, and in the oceans.
Carbon dioxide (CO2): A naturally occurring gas, also a by-product
of burning fossil fuels from fossil carbon deposits, such as oil, gas and
coal, of burning biomass, of land use changes (LUC) and of industrial
processes (e. g., cement production). It is the principal anthropogenic
greenhouse gas (GHG) that affects the earth’s radiative balance. It is
the reference gas against which other GHGs are measured and therefore
has a Global Warming Potential (GWP) of 1. See Annex II.9.1 for
GWP values for other GHGs.
Carbon Dioxide Capture and Storage (CCS): A process in which
a relatively pure stream of carbon dioxide (CO2) from industrial and
energy-related sources is separated (captured), conditioned, compressed,
and transported to a storage location for long-term isolation
from the atmosphere. See also Bioenergy and carbon capture and storage
(BECCS), CCS-ready, and Sequestration.
Carbon dioxide fertilization: The enhancement of the growth of
plants as a result of increased atmospheric carbon dioxide (CO2) concentration.
Carbon Dioxide Removal (CDR): Carbon Dioxide Removal methods
refer to a set of techniques that aim to remove carbon dioxide (CO2)
directly from the atmosphere by either (1) increasing natural sinks for
carbon or (2) using chemical engineering to remove the CO2, with the
intent of reducing the atmospheric CO2 concentration. CDR methods
involve the ocean, land, and technical systems, including such methods
as iron fertilization, large-scale afforestation, and direct capture
of CO2 from the atmosphere using engineered chemical means. Some
CDR methods fall under the category of geoengineering, though this
may not be the case for others, with the distinction being based on
the magnitude, scale, and impact of the particular CDR activities. The


boundary between CDR and mitigation is not clear and there could be
some overlap between the two given current definitions (IPCC, 2012,
p. 2). See also Solar Radiation Management (SRM).
Carbon footprint: Measure of the exclusive total amount of emissions
of carbon dioxide (CO2) that is directly and indirectly caused by
an activity or is accumulated over the life stages of a product (Wiedmann
and Minx, 2008).
Carbon intensity: The amount of emissions of carbon dioxide (CO2)
released per unit of another variable such as gross domestic product
(GDP), output energy use, or transport.
Carbon leakage: See Leakage.
Carbon pool: See Reservoir.
Carbon price: The price for avoided or released carbon dioxide (CO2)
or CO2-equivalent emissions. This may refer to the rate of a carbon
tax, or the price of emission permits. In many models that are used to
assess the economic costs of mitigation, carbon prices are used as a
proxy to represent the level of effort in mitigation policies.
Carbon sequestration: See Sequestration.
Carbon tax: A levy on the carbon content of fossil fuels. Because virtually
all of the carbon in fossil fuels is ultimately emitted as carbon
dioxide (CO2), a carbon tax is equivalent to an emission tax on CO2
emissions.
CCS-ready: New large-scale, stationary carbon dioxide (CO2) point
sources intended to be retrofitted with Carbon Dioxide Capture and
Storage (CCS) could be designed and located to be ‘CCS-ready’ by
reserving space for the capture installation, designing the unit for optimal
performance when capture is added, and siting the plant to enable
access to storage locations. See also Bioenergy and Carbon Dioxide
Capture and Storage (BECCS).
Certified Emission Reduction Unit (CER): Equal to one metric
tonne of CO2-equivalent emissions reduced or of carbon dioxide (CO2)
removed from the atmosphere through the Clean Development Mechanism
(CDM) (defined in Article 12 of the Kyoto Protocol) project, calculated
using Global Warming Potentials (GWP). See also Emissions
Reduction Units (ERU) and Emissions trading.
Chemical oxygen demand (COD): The quantity of oxygen required
for the complete oxidation of organic chemical compounds in water;
used as a measure of the level of organic pollutants in natural and
waste waters. See also Biochemical oxygen demand (BOD).
Chlorofluorocarbons (CFCs): A chlorofluorocarbon is an organic
compound that contains chlorine, carbon, hydrogen, and fluorine and
is used for refrigeration, air conditioning, packaging, plastic foam,
insulation, solvents, or aerosol propellants. Because they are not
destroyed in the lower atmosphere, CFCs drift into the upper atmosphere
where, given suitable conditions, they break down ozone (O3).
It is one of the greenhouse gases (GHGs) covered under the 1987
Montreal Protocol as a result of which manufacturing of these gases
has been phased out and they are being replaced by other compounds,
including hydrofluorocarbons (HFCs) which are GHGs covered under
the Kyoto Protocol.
Clean Development Mechanism (CDM): A mechanism defined
under Article 12 of the Kyoto Protocol through which investors (governments
or companies) from developed (Annex B) countries may
finance greenhouse gas (GHG) emission reduction or removal projects
in developing (Non-Annex B) countries, and receive Certified Emission
Reduction Units (CERs) for doing so. The CERs can be credited towards
the commitments of the respective developed countries. The CDM is
intended to facilitate the two objectives of promoting sustainable
development (SD) in developing countries and of helping industrialized
countries to reach their emissions commitments in a cost-effective
way. See also Kyoto Mechanisms.
Climate: Climate in a narrow sense is usually defined as the average
weather, or more rigorously, as the statistical description in terms of
the mean and variability of relevant quantities over a period of time
ranging from months to thousands or millions of years. The classical
period for averaging these variables is 30 years, as defined by the
World Meteorological Organization. The relevant quantities are most
often surface variables such as temperature, precipitation and wind.
Climate in a wider sense is the state, including a statistical description,
of the climate system.
Climate change: Climate change refers to a change in the state of
the climate that can be identified (e. g., by using statistical tests) by
changes in the mean and / or the variability of its properties, and that
persists for an extended period, typically decades or longer. Climate
change may be due to natural internal processes or external forcings
such as modulations of the solar cycles, volcanic eruptions and persistent
anthropogenic changes in the composition of the atmosphere or
in land use. Note that the United Nations Framework Convention on
Climate Change (UNFCCC), in its Article 1, defines climate change as:
‘a change of climate which is attributed directly or indirectly to human
activity that alters the composition of the global atmosphere and which
is in addition to natural climate variability observed over comparable
time periods’. The UNFCCC thus makes a distinction between climate
change attributable to human activities altering the atmospheric composition,
and climate variability attributable to natural causes. See also
Climate change commitment.
Climate change commitment: Due to the thermal inertia of the
ocean and slow processes in the cryosphere and land surfaces, the climate
would continue to change even if the atmospheric composition
were held fixed at today’s values. Past change in atmospheric composition
leads to a committed climate change, which continues for


as long as a radiative imbalance persists and until all components of
the climate system have adjusted to a new state. The further change
in temperature after the composition of the atmosphere is held constant
is referred to as the constant composition temperature commitment
or simply committed warming or warming commitment. Climate
change commitment includes other future changes, for example in
the hydrological cycle, in extreme weather events, in extreme climate
events, and in sea level change. The constant emission commitment is
the committed climate change that would result from keeping anthropogenic
emissions constant and the zero emission commitment is the
climate change commitment when emissions are set to zero. See also
Climate change.
Climate (change) feedback: An interaction in which a perturbation
in one climate quantity causes a change in a second, and the change
in the second quantity ultimately leads to an additional change in
the first. A negative feedback is one in which the initial perturbation
is weakened by the changes it causes; a positive feedback is one in
which the initial perturbation is enhanced. In this Assessment Report, a
somewhat narrower definition is often used in which the climate quantity
that is perturbed is the global mean surface temperature, which in
turn causes changes in the global radiation budget. In either case, the
initial perturbation can either be externally forced or arise as part of
internal variability.
Climate engineering: See Geoengineering.
Climate finance: There is no agreed definition of climate finance.
The term ‘climate finance’ is applied both to the financial resources
devoted to addressing climate change globally and to financial flows
to developing countries to assist them in addressing climate change.
The literature includes several concepts in these categories, among
which the most commonly used include:
Incremental costs: The cost of capital of the incremental investment
and the change of operating and maintenance costs for a
mitigation or adaptation project in comparison to a reference project.
It can be calculated as the difference of the net present values
of the two projects. See also Additionality.
Incremental investment: The extra capital required for the initial
investment for a mitigation or adaptation project in comparison to
a reference project. See also Additionality.
Total climate finance: All financial flows whose expected effect is
to reduce net greenhouse gas (GHG) emissions and / or to enhance
resilience to the impacts of climate variability and the projected
climate change. This covers private and public funds, domestic and
international flows, expenditures for mitigation and adaptation to
current climate variability as well as future climate change.
Total climate finance flowing to developing countries:The
amount of the total climate finance invested in developing countries
that comes from developed countries. This covers private and
public funds.
Private climate finance flowing to developing countries:
Finance and investment by private actors in / from developed countries
for mitigation and adaptation activities in developing countries.
Public climate finance flowing to developing countries:
Finance provided by developed countries’ governments and bilateral
institutions as well as by multilateral institutions for mitigation
and adaptation activities in developing countries. Most of the
funds provided are concessional loans and grants.
Climate model (spectrum or hierarchy): A numerical representation
of the climate system based on the physical, chemical and biological
properties of its components, their interactions and feedback processes,
and accounting for some of its known properties. The climate
system can be represented by models of varying complexity, that is,
for any one component or combination of components a spectrum or
hierarchy of models can be identified, differing in such aspects as the
number of spatial dimensions, the extent to which physical, chemical
or biological processes are explicitly represented, or the level at which
empirical parametrizations are involved. Coupled Atmosphere-Ocean
General Circulation Models (AOGCMs) provide a representation of the
climate system that is near or at the most comprehensive end of the
spectrum currently available. There is an evolution towards more complex
models with interactive chemistry and biology. Climate models
are applied as a research tool to study and simulate the climate, and
for operational purposes, including monthly, seasonal and interannual
climate predictions.
Climate prediction: A climate prediction or climate forecast is the
result of an attempt to produce (starting from a particular state of the
climate system) an estimate of the actual evolution of the climate in
the future, for example, at seasonal, interannual, or decadal time scales.
Because the future evolution of the climate system may be highly sensitive
to initial conditions, such predictions are usually probabilistic in
nature. See also Climate projection, and Climate scenario.
Climate projection: A climate projection is the simulated response of
the climate system to a scenario of future emission or concentration of
greenhouse gases (GHGs) and aerosols, generally derived using climate
models. Climate projections are distinguished from climate predictions
by their dependence on the emission / concentration / radiative forcing
scenario used, which is in turn based on assumptions concerning, for
example, future socioeconomic and technological developments that
may or may not be realized. See also Climate scenario.
Climate scenario: A plausible and often simplified representation
of the future climate, based on an internally consistent set of climatological
relationships that has been constructed for explicit use in
investigating the potential consequences of anthropogenic climate


change, often serving as input to impact models. Climate projections
often serve as the raw material for constructing climate scenarios,
but climate scenarios usually require additional information such as
the observed current climate. See also Baseline / reference, Emission
scenario, Mitigation scenario, Representative concentration pathways
(RCPs), Scenario, Shared socio-economic pathways, Socio-economic
scenario, SRES scenarios, Stabilization, and Transformation pathway.
Climate sensitivity: In IPCC reports, equilibrium climate sensitivity
(units: °C) refers to the equilibrium (steady state) change in the annual
global mean surface temperature following a doubling of the atmospheric
CO2-equivalent concentration. Owing to computational constraints,
the equilibrium climate sensitivity in a climate model is sometimes
estimated by running an atmospheric general circulation model
(GCM) coupled to a mixed-layer ocean model, because equilibrium
climate sensitivity is largely determined by atmospheric processes.
Efficient models can be run to equilibrium with a dynamic ocean. The
climate sensitivity parameter (units: °C (W m – 2) – 1) refers to the equilibrium
change in the annual global mean surface temperature following
a unit change in radiative forcing.
The effective climate sensitivity (units: °C) is an estimate of the global
mean surface temperature response to doubled carbon dioxide (CO2)
concentration that is evaluated from model output or observations for
evolving non-equilibrium conditions. It is a measure of the strengths of
the climate feedbacks at a particular time and may vary with forcing
history and climate state, and therefore may differ from equilibrium
climate sensitivity.
The transient climate response (units: °C) is the change in the global
mean surface temperature, averaged over a 20-year period, centred at
the time of atmospheric CO2 doubling, in a climate model simulation
in which CO2 increases at 1 % yr – 1. It is a measure of the strength and
rapidity of the surface temperature response to greenhouse gas (GHG)
forcing.
Climate system: The climate system is the highly complex system
consisting of five major components: the atmosphere, the hydrosphere,
the cryosphere, the lithosphere and the biosphere, and the interactions
between them. The climate system evolves in time under the influence
of its own internal dynamics and because of external forcings such as
volcanic eruptions, solar variations and anthropogenic forcings such
as the changing composition of the atmosphere and land use change
(LUC).
Climate threshold: A limit within the climate system that, when
crossed, induces a non-linear response to a given forcing. See also
Abrupt climate change.
Climate variability: Climate variability refers to variations in the
mean state and other statistics (such as standard deviations, the occurrence
of extremes, etc.) of the climate on all spatial and temporal
scales beyond that of individual weather events. Variability may be due
to natural internal processes within the climate system (internal variability),
or to variations in natural or anthropogenic external forcing
(external variability). See also Climate change.
CO2-equivalent concentration: The concentration of carbon dioxide
(CO2) that would cause the same radiative forcing as a given mixture
of CO2 and other forcing components. Those values may consider only
greenhouse gases (GHGs), or a combination of GHGs, aerosols, and
surface albedo changes. CO2-equivalent concentration is a metric for
comparing radiative forcing of a mix of different forcing components
at a particular time but does not imply equivalence of the corresponding
climate change responses nor future forcing. There is generally
no connection between CO2-equivalent emissions and resulting CO2-
equivalent concentrations.
CO2-equivalent emission: The amount of carbon dioxide (CO2) emission
that would cause the same integrated radiative forcing, over a
given time horizon, as an emitted amount of a greenhouse gas (GHG)
or a mixture of GHGs. The CO2-equivalent emission is obtained by multiplying
the emission of a GHG by its Global Warming Potential (GWP)
for the given time horizon (see Annex II.9.1 and WGI AR5 Table 8.A.1
for GWP values of the different GHGs). For a mix of GHGs it is obtained
by summing the CO2-equivalent emissions of each gas. CO2-equivalent
emission is a common scale for comparing emissions of different GHGs
but does not imply equivalence of the corresponding climate change
responses. See also CO2-equivalent concentration.
Co-benefits: The positive effects that a policy or measure aimed at
one objective might have on other objectives, without yet evaluating
the net effect on overall social welfare. Co-benefits are often subject
to uncertainty and depend on, among others, local circumstances and
implementation practices. Co-benefits are often referred to as ancillary
benefits. See also Adverse side-effect, Risk, and Risk tradeoff.
Cogeneration: Cogeneration (also referred to as combined heat and
power, or CHP) is the simultaneous generation and useful application
of electricity and useful heat.
Combined-cycle gas turbine: A power plant that combines two processes
for generating electricity. First, fuel combustion drives a gas turbine.
Second, exhaust gases from the turbine are used to heat water to
drive a steam turbine.
Combined heat and power (CHP): See Cogeneration.
Computable General Equilibrium (CGE) Model: See Models.
Conference of the Parties (COP): The supreme body of the United
Nations Framework Convention on Climate Change (UNFCCC), comprising
countries with a right to vote that have ratified or acceded to
the convention. See also Meeting of the Parties (CMP).


Confidence: The validity of a finding based on the type, amount,
quality, and consistency of evidence (e. g., mechanistic understanding,
theory, data, models, expert judgment) and on the degree of agreement.
In this report, confidence is expressed qualitatively (Mastrandrea
et al., 2010). See WGI AR5 Figure 1.11 for the levels of confidence
and WGI AR5 Table 1.2 for the list of likelihood qualifiers. See also
Uncertainty.
Consumption-based accounting: Consumption-based accounting
provides a measure of emissions released to the atmosphere in order
to generate the goods and services consumed by a certain entity (e. g.,
person, firm, country, or region). See also Production-based accounting.
Contingent valuation method: An approach to quantitatively
assess values assigned by people in monetary (willingness to pay)
and non-monetary (willingness to contribute with time, resources
etc.) terms. It is a direct method to estimate economic values for
ecosystem and environmental services. In a survey, people are asked
their willingness to pay / contribute for access to, or their willingness
to accept compensation for removal of, a specific environmental service,
based on a hypothetical scenario and description of the environmental
service.
Conventional fuels: See Fossil fuels.
Copenhagen Accord: The political (as opposed to legal) agreement
that emerged at the 15th Session of the Conference of the Parties
(COP) at which delegates ‘agreed to take note’ due to a lack of consensus
that an agreement would require. Some of the key elements
include: recognition of the importance of the scientific view on the
need to limit the increase in global mean surface temperature to 2°
C; commitment by Annex I Parties to implement economy-wide emissions
targets by 2020 and non-Annex I Parties to implement mitigation
actions; agreement to have emission targets of Annex I Parties
and their delivery of finance for developing countries subject to Measurement,
Reporting and Verification (MRV) and actions by developing
countries to be subject to domestic MRV; calls for scaled up financing
including a fast track financing of USD 30 billion and USD 100 billion
by 2020; the establishment of a new Green Climate Fund (GCF); and
the establishment of a new technology mechanism. Some of these elements
were later adopted in the Cancún Agreements.
Cost-benefit analysis (CBA): Monetary measurement of all negative
and positive impacts associated with a given action. Costs and benefits
are compared in terms of their difference and / or ratio as an indicator
of how a given investment or other policy effort pays off seen from the
society’s point of view.
Cost of conserved energy (CCE): See Levelized cost of conserved
energy (LCCE).
Cost-effectiveness: A policy is more cost-effective if it achieves a
goal, such as a given pollution abatement level, at lower cost. A critical
condition for cost-effectiveness is that marginal abatement costs
be equal among obliged parties. Integrated models approximate costeffective
solutions, unless they are specifically constrained to behave
otherwise. Cost-effective mitigation scenarios are those based on a
stylized implementation approach in which a single price on carbon
dioxide (CO2) and other greenhouse gases (GHGs) is applied across the
globe in every sector of every country and that rises over time in a way
that achieves lowest global discounted costs.
Cost-effectiveness analysis (CEA): A tool based on constrained
optimization for comparing policies designed to meet a prespecified
target.
Crediting period, Clean Development Mechanism (CDM): The
time during which a project activity is able to generate Certified Emission
Reduction Units (CERs). Under certain conditions, the crediting
period can be renewed up to two times.
Cropland management: The system of practices on land on which
agricultural crops are grown and on land that is set aside or temporarily
not being used for crop production (UNFCCC, 2002).
Decarbonization: The process by which countries or other entities
aim to achieve a low-carbon economy, or by which individuals aim to
reduce their carbon consumption.
Decomposition approach: Decomposition methods disaggregate the
total amount of historical changes of a policy variable into contributions
made by its various determinants.
Deforestation: Conversion of forest to non-forest is one of the major
sources of greenhouse gas (GHG) emissions. Under Article 3.3 of the
Kyoto Protocol, “the net changes in greenhouse gas emissions by
sources and removals by sinks resulting from direct human-induced
land-use change and forestry activities, limited to afforestation,
reforestation and deforestation since 1990, measured as verifiable
changes in carbon stocks in each commitment period, shall be sued
to meet the commitments under this Article of each Party included in
Annex I”. Reducing emissions from deforestation is not eligible for
Joint Implementation (JI) or Clean Development Mechanism (CDM)
projects but has been introduced in the program of work under REDD
(Reducing Emissions from Deforestation and Forest Degradation)
under the United Nations Framework Convention on Climate Change
(UNFCCC).
For a discussion of the term forest and related terms such as afforestation,
reforestation, and deforestation see the IPCC Special Report on
Land Use, Land-Use Change and Forestry (IPCC, 2000). See also the
report on Definitions and Methodological Options to Inventory Emissions
from Direct Human-induced Degradation of Forests and Devegetation
of Other Vegetation Types (IPCC, 2003).


Dematerialization: The ambition to reduce the total material inputs
required to deliver a final service.
Descriptive analysis: Descriptive (also termed positive) approaches to
analysis focus on how the world works or actors behave, not how they
should behave in some idealized world. See also Normative analysis.
Desertification: Land degradation in arid, semi-arid, and dry subhumid
areas resulting from various factors, including climatic variations
and human activities. Land degradation in arid, semi-arid, and
dry sub-humid areas is a reduction or loss of the biological or economic
productivity and complexity of rainfed cropland, irrigated cropland,
or range, pasture, forest, and woodlands resulting from land uses
or from a process or combination of processes, including processes
arising from human activities and habitation patterns, such as (1) soil
erosion caused by wind and / or water; (2) deterioration of the physical,
chemical, biological, or economic properties of soil; and (3) long-term
loss of natural vegetation (UNCCD, 1994).
Designated national authority (DNA): A designated national
authority is a national institution that authorizes and approves Clean
Development Mechansim (CDM) projects in that country. In CDM host
countries, the DNA assesses whether proposed projects assist the host
country in achieving its sustainable development (SD) goals, certification
of which is a prerequisite for registration of the project by the
CDM Executive Board.
Developed / developing countries: See Industrialized / developing
countries.
Development pathway: An evolution based on an array of technological,
economic, social, institutional, cultural, and biophysical characteristics
that determine the interactions between human and natural
systems, including consumption and production patterns in all countries,
over time at a particular scale.
Direct Air Capture (DAC): Chemical process by which a pure carbon
dioxide (CO2) stream is produced by capturing CO2 from the ambient
air.
Direct emissions: See Emissions.
Discounting: A mathematical operation making monetary (or other)
amounts received or expended at different times (years) comparable
across time. The discounter uses a fixed or possibly time-varying discount
rate (> 0) from year to year that makes future value worth less
today. See also Present value.
Double dividend: The extent to which revenue-generating instruments,
such as carbon taxes or auctioned (tradable) emission permits
can (1) contribute to mitigation and (2) offset at least part of the
potential welfare losses of climate policies through recycling the revenue
in the economy to reduce other taxes likely to cause distortions.
Drivers of behaviour: Determinants of human decisions and actions,
including peoples’ values and goals and the factors that constrain
action, including economic factors and incentives, information access,
regulatory and technological constraints, cognitive and emotional
processing capacity, and social norms. See also Behaviour and Behavioural
change.
Drivers of emissions: Drivers of emissions refer to the processes,
mechanisms and properties that influence emissions through factors.
Factors comprise the terms in a decomposition of emissions. Factors
and drivers may in return affect policies, measures and other drivers.
Economic efficiency: Economic efficiency refers to an economy’s allocation
of resources (goods, services, inputs, productive activities). An
allocation is efficient if it is not possible to reallocate resources so as
to make at least one person better off without making someone else
worse off. An allocation is inefficient if such a reallocation is possible.
This is also known as the Pareto Criterion for efficiency. See also Pareto
optimum.
Economies in Transition (EITs): Countries with their economies
changing from a planned economic system to a market economy. See
Annex II.2.1.
Ecosystem: A functional unit consisting of living organisms, their nonliving
environment, and the interactions within and between them. The
components included in a given ecosystem and its spatial boundaries
depend on the purpose for which the ecosystem is defined: in some
cases they are relatively sharp, while in others they are diffuse. Ecosystem
boundaries can change over time. Ecosystems are nested within
other ecosystems, and their scale can range from very small to the
entire biosphere. In the current era, most ecosystems either contain
people as key organisms, or are influenced by the effects of human
activities in their environment.
Ecosystem services: Ecological processes or functions having monetary
or non-monetary value to individuals or society at large. These
are frequently classified as (1) supporting services such as productivity
or biodiversity maintenance, (2) provisioning services such as food,
fiber, or fish, (3) regulating services such as climate regulation or carbon
sequestration, and (4) cultural services such as tourism or spiritual
and aesthetic appreciation.
Embodied emissions: See Emissions.
Embodied energy: See Energy.
Emission allowance: See Emission permit.
Emission factor / Emissions intensity: The emissions released per
unit of activity. See also Carbon intensity.


Emission permit: An entitlement allocated by a government to a
legal entity (company or other emitter) to emit a specified amount of a
substance. Emission permits are often used as part of emissions trading
schemes.
Emission quota: The portion of total allowable emissions assigned to
a country or group of countries within a framework of maximum total
emissions.
Emission scenario: A plausible representation of the future development
of emissions of substances that are potentially radiatively
active (e. g., greenhouse gases, aerosols) based on a coherent and
internally consistent set of assumptions about driving forces (such
as demographic and socioeconomic development, technological
change, energy and land use) and their key relationships. Concentration
scenarios, derived from emission scenarios, are used as input to
a climate model to compute climate projections. In IPCC (1992) a set
of emission scenarios was presented which were used as a basis for
the climate projections in IPCC (1996). These emission scenarios are
referred to as the IS92 scenarios. In the IPCC Special Report on Emission
Scenarios (Nakićenović and Swart, 2000) emission scenarios,
the so-called SRES scenarios, were published, some of which were
used, among others, as a basis for the climate projections presented
in Chapters 9 to 11 of IPCC (2001) and Chapters 10 and 11 of IPCC
(2007). New emission scenarios for climate change, the four Representative
Concentration Pathways (RCPs), were developed for, but
independently of, the present IPCC assessment. See also Baseline / reference,
Climate scenario, Mitigation scenario, Shared socio-economic
pathways, Scenario, Socio-economic scenario, Stabilization, and
Transformation pathway.
Emission trajectories: A projected development in time of the emission
of a greenhouse gas (GHG) or group of GHGs, aerosols, and GHG
precursors.
Emissions:
Agricultural emissions: Emissions associated with agricultural
systems — predominantly methane (CH4) or nitrous oxide (N2O).
These include emissions from enteric fermentation in domestic
livestock, manure management, rice cultivation, prescribed burning
of savannas and grassland, and from soils (IPCC, 2006).
Anthropogenic emissions: Emissions of greenhouse gases
(GHGs), aerosols, and precursors of a GHG or aerosol caused by
human activities. These activities include the burning of fossil fuels,
deforestation, land use changes (LUC), livestock production, fertilization,
waste management, and industrial processes.
Direct emissions: Emissions that physically arise from activities
within well-defined boundaries of, for instance, a region, an economic
sector, a company, or a process.
Embodied emissions: Emissions that arise from the production
and delivery of a good or service or the build-up of infrastructure.
Depending on the chosen system boundaries, upstream emissions
are often included (e. g., emissions resulting from the extraction of
raw materials). See also Lifecycle assessment (LCA).
Indirect emissions: Emissions that are a consequence of the
activities within well-defined boundaries of, for instance, a region,
an economic sector, a company or process, but which occur outside
the specified boundaries. For example, emissions are described as
indirect if they relate to the use of heat but physically arise outside
the boundaries of the heat user, or to electricity production
but physically arise outside of the boundaries of the power supply
sector.
Scope 1, Scope 2, and Scope 3 emissions: Emissions responsibility
as defined by the GHG Protocol, a private sector initiative.
‘Scope 1’ indicates direct greenhouse gas (GHG) emissions that are
from sources owned or controlled by the reporting entity. ‘Scope
’ indicates indirect GHG emissions associated with the production
of electricity, heat, or steam purchased by the reporting entity.
‘Scope 3’ indicates all other indirect emissions, i. e., emissions associated
with the extraction and production of purchased materials,
fuels, and services, including transport in vehicles not owned or
controlled by the reporting entity, outsourced activities, waste disposal,
etc. (WBCSD and WRI, 2004).
Territorial emissions: Emissions that take place within the territories
of a particular jurisdiction.
Emissions Reduction Unit (ERU): Equal to one metric tonne of CO2-
equivalent emissions reduced or of carbon dioxide (CO2) removed from
the atmosphere through a Joint Implementation (JI) (defined in Article
of the Kyoto Protocol) project, calculated using Global Warming
Potentials (GWPs). See also Certified Emission Reduction Unit (CER)
and Emissions trading.
Emission standard: An emission level that, by law or by voluntary
agreement, may not be exceeded. Many standards use emission factors
in their prescription and therefore do not impose absolute limits
on the emissions.
Emissions trading: A market-based instrument used to limit emissions.
The environmental objective or sum of total allowed emissions is
expressed as an emissions cap. The cap is divided in tradable emission
permits that are allocated — either by auctioning or handing out for
free (grandfathering) — to entities within the jurisdiction of the trading
scheme. Entities need to surrender emission permits equal to the
amount of their emissions (e. g., tonnes of carbon dioxide). An entity
may sell excess permits. Trading schemes may occur at the intra-company,
domestic, or international level and may apply to carbon dioxide
(CO2), other greenhouse gases (GHGs), or other substances. Emissions


trading is also one of the mechanisms under the Kyoto Protocol. See
also Kyoto Mechanisms.
Energy: The power of ‘doing work’ possessed at any instant by a
body or system of bodies. Energy is classified in a variety of types and
becomes available to human ends when it flows from one place to
another or is converted from one type into another.
Embodied energy: The energy used to produce a material substance
or product (such as processed metals or building materials),
taking into account energy used at the manufacturing facility,
energy used in producing the materials that are used in the manufacturing
facility, and so on.
Final energy: See Primary energy.
Primary energy: Primary energy (also referred to as energy
sources) is the energy stored in natural resources (e. g., coal, crude
oil, natural gas, uranium, and renewable sources). It is defined in
several alternative ways. The International Energy Agency (IEA)
utilizes the physical energy content method, which defines primary
energy as energy that has not undergone any anthropogenic
conversion. The method used in this report is the direct equivalent
method (see Annex II.4), which counts one unit of secondary
energy provided from non-combustible sources as one unit of primary
energy, but treats combustion energy as the energy potential
contained in fuels prior to treatment or combustion. Primary
energy is transformed into secondary energy by cleaning (natural
gas), refining (crude oil to oil products) or by conversion into electricity
or heat. When the secondary energy is delivered at the enduse
facilities it is called final energy (e. g., electricity at the wall
outlet), where it becomes usable energy in supplying energy services
(e. g., light).
Renewable energy (RE): Any form of energy from solar, geophysical,
or biological sources that is replenished by natural processes
at a rate that equals or exceeds its rate of use. For a more detailed
description see Bioenergy, Solar energy, Hydropower, Ocean, Geothermal,
and Wind energy.
Secondary energy: See Primary energy.
Energy access: Access to clean, reliable and affordable energy services
for cooking and heating, lighting, communications, and productive
uses (AGECC, 2010).
Energy carrier: A substance for delivering mechanical work or transfer
of heat. Examples of energy carriers include: solid, liquid, or gaseous
fuels (e. g., biomass, coal, oil, natural gas, hydrogen); pressurized
/ heated / cooled fluids (air, water, steam); and electric current.
Energy density: The ratio of stored energy to the volume or mass of
a fuel or battery.
Energy efficiency (EE): The ratio of useful energy output of a system,
conversion process, or activity to its energy input. In economics, the
term may describe the ratio of economic output to energy input. See
also Energy intensity.
Energy intensity: The ratio of energy use to economic or physical output.
Energy poverty: A lack of access to modern energy services. See also
Energy access.
Energy security: The goal of a given country, or the global community
as a whole, to maintain an adequate, stable, and predictable energy
supply. Measures encompass safeguarding the sufficiency of energy
resources to meet national energy demand at competitive and stable
prices and the resilience of the energy supply; enabling development
and deployment of technologies; building sufficient infrastructure to
generate, store and transmit energy supplies; and ensuring enforceable
contracts of delivery.
Energy services: An energy service is the benefit received as a result
of energy use.
Energy system: The energy system comprises all components related
to the production, conversion, delivery, and use of energy.
Environmental effectiveness: A policy is environmentally effective
to the extent by which it achieves its expected environmental target
(e. g., greenhouse gas (GHG) emission reduction).
Environmental input-output analysis: An analytical method used
to allocate environmental impacts arising in production to categories
of final consumption, by means of the Leontief inverse of a country’s
economic input-output tables. See also Annex II.6.2.
Environmental Kuznets Curve: The hypothesis that various environmental
impacts first increase and then eventually decrease as income
per capita increases.
Evidence: Information indicating the degree to which a belief or proposition
is true or valid. In this report, the degree of evidence reflects
the amount, quality, and consistency of scientific / technical information
on which the Lead Authors are basing their findings. See also Agreement,
Confidence, Likelihood and Uncertainty.
Externality / external cost / external benefit: Externalities arise from
a human activity when agents responsible for the activity do not take
full account of the activity’s impacts on others’ production and consumption
possibilities, and no compensation exists for such impacts.
When the impacts are negative, they are external costs. When the
impacts are positive, they are external benefits. See also Social costs.


Feed-in tariff (FIT): The price per unit of electricity (heat) that a utility
or power (heat) supplier has to pay for distributed or renewable electricity
(heat) fed into the power grid (heat supply system) by non-utility
generators. A public authority regulates the tariff.
Final energy: See Primary energy.
Flaring: Open air burning of waste gases and volatile liquids, through
a chimney, at oil wells or rigs, in refineries or chemical plants, and at
landfills.
Flexibility Mechanisms: See Kyoto Mechanisms.
Food security: A state that prevails when people have secure access
to sufficient amounts of safe and nutritious food for normal growth,
development, and an active and healthy life.4
Forest: A vegetation type dominated by trees. Many definitions of the
term forest are in use throughout the world, reflecting wide differences
in biogeophysical conditions, social structure and economics. According
to the 2005 United Nations Framework Convention on Climate Change
(UNFCCC) definition a forest is an area of land of at least 0.05 – 1 hectare,
of which more than 10 – 30 % is covered by tree canopy. Trees must
have a potential to reach a minimum of 25 meters at maturity in situ.
Parties to the Convention can choose to define a forest from within
those ranges. Currently, the definition does not recognize different
biomes, nor do they distinguish natural forests from plantations, an
anomaly being pointed out by many as in need of rectification.
For a discussion of the term forest and related terms such as afforestation,
reforestation and deforestation see the IPCC Report on Land Use,
Land-Use Change and Forestry (IPCC, 2000). See also the Report on
Definitions and Methodological Options to Inventory Emissions from
Direct Human-induced Degradation of Forests and Devegetation of
Other Vegetation Types (IPCC, 2003).
Forest management: A system of practices for stewardship and use
of forest land aimed at fulfilling relevant ecological (including biological
diversity), economic and social functions of the forest in a sustainable
manner (UNFCCC, 2002).
Forestry and Other Land Use (FOLU): See Agriculture, Forestry and
Other Land Use (AFOLU).
Fossil fuels: Carbon-based fuels from fossil hydrocarbon deposits,
including coal, peat, oil, and natural gas.
Free Rider: One who benefits from a common good without contributing
to its creation or preservation.
This glossary entry builds on definitions used in FAO (2000) and previous IPCC
reports.
Fuel cell: A fuel cell generates electricity in a direct and continuous
way from the controlled electrochemical reaction of hydrogen or
another fuel and oxygen. With hydrogen as fuel the cell emits only
water and heat (no carbon dioxide) and the heat can be utilized (see
also Cogeneration).
Fuel poverty: A condition in which a household is unable to guarantee
a certain level of consumption of domestic energy services (especially
heating) or suffers disproportionate expenditure burdens to meet
these needs.
Fuel switching: In general, fuel switching refers to substituting fuel A
for fuel B. In the context of mitigation it is implicit that fuel A has lower
carbon content than fuel B, e. g., switching from natural gas to coal.
General circulation (climate) model (GCM): See Climate model.
General equilibrium analysis: General equilibrium analysis considers
simultaneously all the markets and feedback effects among these
markets in an economy leading to market clearance. (Computable)
general equilibrium (CGE) models are the operational tools used to
perform this type of analysis.
Geoengineering: Geoengineering refers to a broad set of methods
and technologies that aim to deliberately alter the climate system
in order to alleviate the impacts of climate change. Most, but not
all, methods seek to either (1) reduce the amount of absorbed solar
energy in the climate system (Solar Radiation Management) or (2)
increase net carbon sinks from the atmosphere at a scale sufficiently
large to alter climate (Carbon Dioxide Removal). Scale and intent
are of central importance. Two key characteristics of geoengineering
methods of particular concern are that they use or affect the climate
system (e. g., atmosphere, land or ocean) globally or regionally
and / or could have substantive unintended effects that cross national
boundaries. Geoengineering is different from weather modification
and ecological engineering, but the boundary can be fuzzy (IPCC,
, p. 2).
Geothermal energy: Accessible thermal energy stored in the earth’s
interior.
Global Environment Facility (GEF): The Global Environment Facility,
established in 1991, helps developing countries fund projects and
programmes that protect the global environment. GEF grants support
projects related to biodiversity, climate change, international waters,
land degradation, the ozone (O3) layer, and persistent organic pollutants.
Global mean surface temperature: An estimate of the global mean
surface air temperature. However, for changes over time, only anomalies,
as departures from a climatology, are used, most commonly based
on the area-weighted global average of the sea surface temperature
anomaly and land surface air temperature anomaly.


Global warming: Global warming refers to the gradual increase,
observed or projected, in global surface temperature, as one of the
consequences of radiative forcing caused by anthropogenic emissions.
Global Warming Potential (GWP): An index, based on radiative
properties of greenhouse gases (GHGs), measuring the radiative forcing
following a pulse emission of a unit mass of a given GHG in the
present-day atmosphere integrated over a chosen time horizon, relative
to that of carbon dioxide (CO2). The GWP represents the combined
effect of the differing times these gases remain in the atmosphere and
their relative effectiveness in causing radiative forcing. The Kyoto Protocol
is based on GWPs from pulse emissions over a 100-year time
frame. Unless stated otherwise, this report uses GWP values calculated
with a 100-year time horizon which are often derived from the IPCC
Second Assessment Report (see Annex II.9.1 for the GWP values of the
different GHGs).
Governance: A comprehensive and inclusive concept of the full range
of means for deciding, managing, and implementing policies and measures.
Whereas government is defined strictly in terms of the nationstate,
the more inclusive concept of governance recognizes the contributions
of various levels of government (global, international, regional,
local) and the contributing roles of the private sector, of nongovernmental
actors, and of civil society to addressing the many types of
issues facing the global community.
Grazing land management: The system of practices on land used for
livestock production aimed at manipulating the amount and type of
vegetation and livestock produced (UNFCCC, 2002).
Green Climate Fund (GCF): The Green Climate Fund was established
by the 16th Session of the Conference of the Parties (COP) in 2010 as
an operating entity of the financial mechanism of the United Nations
Framework Convention on Climate Change (UNFCCC), in accordance
with Article 11 of the Convention, to support projects, programmes
and policies and other activities in developing country Parties. The
Fund is governed by a Board and will receive guidance of the COP. The
Fund is headquartered in Songdo, Republic of Korea.
Greenhouse effect: The infrared radiative effect of all infraredabsorbing
constituents in the atmosphere. Greenhouse gases (GHGs),
clouds, and (to a small extent) aerosols absorb terrestrial radiation
emitted by the earth’s surface and elsewhere in the atmosphere. These
substances emit infrared radiation in all directions, but, everything else
being equal, the net amount emitted to space is normally less than
would have been emitted in the absence of these absorbers because
of the decline of temperature with altitude in the troposphere and the
consequent weakening of emission. An increase in the concentration
of GHGs increases the magnitude of this effect; the difference is sometimes
called the enhanced greenhouse effect. The change in a GHG
concentration because of anthropogenic emissions contributes to an
instantaneous radiative forcing. Surface temperature and troposphere
warm in response to this forcing, gradually restoring the radiative balance
at the top of the atmosphere.
Greenhouse gas (GHG): Greenhouse gases are those gaseous constituents
of the atmosphere, both natural and anthropogenic, that
absorb and emit radiation at specific wavelengths within the spectrum
of terrestrial radiation emitted by the earth’s surface, the atmosphere
itself, and by clouds. This property causes the greenhouse effect. Water
vapour (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane
(CH4) and ozone (O3) are the primary GHGs in the earth’s atmosphere.
Moreover, there are a number of entirely human-made GHGs in the
atmosphere, such as the halocarbons and other chlorine- and brominecontaining
substances, dealt with under the Montreal Protocol. Beside
CO2, N2O and CH4, the Kyoto Protocol deals with the GHGs sulphur
hexafluoride (SF6), hydrofluorocarbons (HFCs) and perfluorocarbons
(PFCs). For a list of well-mixed GHGs, see WGI AR5 Table 2.A.1.
Gross domestic product (GDP): The sum of gross value added, at
purchasers’ prices, by all resident and non-resident producers in the
economy, plus any taxes and minus any subsidies not included in the
value of the products in a country or a geographic region for a given
period, normally one year. GDP is calculated without deducting for
depreciation of fabricated assets or depletion and degradation of natural
resources.
Gross national expenditure (GNE): The total amount of public and
private consumption and capital expenditures of a nation. In general,
national account is balanced such that gross domestic product (GDP) +
import = GNE + export.
Gross national product: The value added from domestic and foreign
sources claimed by residents. GNP comprises gross domestic product
(GDP) plus net receipts of primary income from non-resident income.
Gross world product: An aggregation of the individual country’s
gross domestic products (GDP) to obtain the world or global GDP.
Heat island: The relative warmth of a city compared with surrounding
rural areas, associated with changes in runoff, effects on heat retention,
and changes in surface albedo.
Human Development Index (HDI): The Human Development Index
allows the assessment of countries’ progress regarding social and economic
development as a composite index of three indicators: (1) health
measured by life expectancy at birth; (2) knowledge as measured by
a combination of the adult literacy rate and the combined primary,
secondary and tertiary school enrolment ratio; and (3) standard of living
as gross domestic product (GDP) per capita (in purchasing power
parity). The HDI sets a minimum and a maximum for each dimension,
called goalposts, and then shows where each country stands in relation
to these goalposts, expressed as a value between 0 and 1. The
HDI only acts as a broad proxy for some of the key issues of human


development; for instance, it does not reflect issues such as political
participation or gender inequalities.
Hybrid vehicle: Any vehicle that employs two sources of propulsion,
particularly a vehicle that combines an internal combustion engine
with an electric motor.
Hydrofluorocarbons (HFCs): One of the six types of greenhouse
gases (GHGs) or groups of GHGs to be mitigated under the Kyoto Protocol.
They are produced commercially as a substitute for chlorofluorocarbons
(CFCs). HFCs largely are used in refrigeration and semiconductor
manufacturing. See also Global Warming Potential (GWP) and
Annex II.9.1 for GWP values.
Hydropower: Power harnessed from the flow of water.
Incremental costs: See Climate finance.
Incremental investment: See Climate finance.
Indigenous peoples: Indigenous peoples and nations are those that,
having a historical continuity with pre-invasion and pre-colonial societies
that developed on their territories, consider themselves distinct
from other sectors of the societies now prevailing on those territories,
or parts of them. They form at present principally non-dominant sectors
of society and are often determined to preserve, develop, and transmit
to future generations their ancestral territories, and their ethnic identity,
as the basis of their continued existence as peoples, in accordance
with their own cultural patterns, social institutions, and common law
system.5
Indirect emissions: See Emissions.
Indirect land use change (iLUC): See Land use.
Industrial Revolution: A period of rapid industrial growth with farreaching
social and economic consequences, beginning in Britain during
the second half of the 18th century and spreading to Europe and
later to other countries including the United States. The invention of
the steam engine was an important trigger of this development. The
industrial revolution marks the beginning of a strong increase in the
use of fossil fuels and emission of, in particular, fossil carbon dioxide.
In this report the terms pre-industrial and industrial refer, somewhat
arbitrarily, to the periods before and after 1750, respectively.
Industrialized countries / developing countries: There are a diversity
of approaches for categorizing countries on the basis of their level
of development, and for defining terms such as industrialized, developed,
or developing. Several categorizations are used in this report. (1)
This glossary entry builds on the definitions used in Cobo (1987) and previous
IPCC reports.
In the United Nations system, there is no established convention for
designating of developed and developing countries or areas. (2) The
United Nations Statistics Division specifies developed and developing
regions based on common practice. In addition, specific countries are
designated as Least Developed Countries (LCD), landlocked developing
countries, small island developing states, and transition economies.
Many countries appear in more than one of these categories. (3) The
World Bank uses income as the main criterion for classifying countries
as low, lower middle, upper middle, and high income. (4) The UNDP
aggregates indicators for life expectancy, educational attainment, and
income into a single composite Human Development Index (HDI) to
classify countries as low, medium, high, or very high human development.
See WGII AR5 Box 1 – 2.
Input-output analysis: See Environmental input-output analysis.
Institution: Institutions are rules and norms held in common by social
actors that guide, constrain and shape human interaction. Institutions
can be formal, such as laws and policies, or informal, such as
norms and conventions. Organizations — such as parliaments, regulatory
agencies, private firms, and community bodies — develop and act
in response to institutional frameworks and the incentives they frame.
Institutions can guide, constrain and shape human interaction through
direct control, through incentives, and through processes of socialization.
Institutional feasibility: Institutional feasibility has two key parts: (1)
the extent of administrative workload, both for public authorities and
for regulated entities, and (2) the extent to which the policy is viewed
as legitimate, gains acceptance, is adopted, and is implemented.
Integrated assessment: A method of analysis that combines results
and models from the physical, biological, economic, and social sciences,
and the interactions among these components in a consistent framework
to evaluate the status and the consequences of environmental
change and the policy responses to it. See also Integrated Models.
Integrated models: See Models.
IPAT identity: IPAT is the lettering of a formula put forward to describe
the impact of human activity on the environment. Impact (I) is viewed
as the product of population size (P), affluence (A=GDP / person) and
technology (T= impact per GDP unit). In this conceptualization, population
growth by definition leads to greater environmental impact if A
and T are constant, and likewise higher income leads to more impact
(Ehrlich and Holdren, 1971).
Iron fertilization: Deliberate introduction of iron to the upper ocean
intended to enhance biological productivity which can sequester additional
atmospheric carbon dioxide (CO2) into the oceans. See also Geoengineering
and Carbon Dioxide Removal (CDR).
Jevon’s paradox: See Rebound effect.


Joint Implementation (JI): A mechanism defined in Article 6 of the
Kyoto Protocol, through which investors (governments or companies)
from developed (Annex B) countries may implement projects jointly
that limit or reduce emissions or enhance sinks, and to share the Emissions
Reduction Units (ERU). See also Kyoto Mechanisms.
Kaya identity: In this identity global emissions are equal to the population
size, multiplied by per capita output (gross world product), multiplied
by the energy intensity of production, multiplied by the carbon
intensity of energy.
Kyoto Mechanisms (also referred to as Flexibility Mechanisms):
Market-based mechanisms that Parties to the Kyoto Protocol can use in
an attempt to lessen the potential economic impacts of their commitment
to limit or reduce greenhouse gas (GHG) emissions. They include
Joint Implementation (JI) (Article 6), Clean Development Mechanism
(CDM) (Article 12), and Emissions trading (Article 17).
Kyoto Protocol: The Kyoto Protocol to the United Nations Framework
Convention on Climate Change (UNFCCC) was adopted in 1997 in
Kyoto, Japan, at the Third Session of the Conference of the Parties (COP)
to the UNFCCC. It contains legally binding commitments, in addition to
those included in the UNFCCC. Countries included in Annex B of the
Protocol (most Organisation for Economic Cooperation and Development
countries and countries with economies in transition) agreed to
reduce their anthropogenic greenhouse gas (GHG) emissions (carbon
dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons
(HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6)) by at
least 5 % below 1990 levels in the commitment period 2008 – 2012.
The Kyoto Protocol entered into force on 16 February 2005.
Land use (change, direct and indirect): Land use refers to the total
of arrangements, activities and inputs undertaken in a certain land
cover type (a set of human actions). The term land use is also used
in the sense of the social and economic purposes for which land is
managed (e. g., grazing, timber extraction and conservation). In urban
settlements it is related to land uses within cities and their hinterlands.
Urban land use has implications on city management, structure, and
form and thus on energy demand, greenhouse gas (GHG) emissions,
and mobility, among other aspects.
Land use change (LUC): Land use change refers to a change in
the use or management of land by humans, which may lead to a
change in land cover. Land cover and LUC may have an impact on
the surface albedo, evapotranspiration, sources and sinks of GHGs,
or other properties of the climate system and may thus give rise to
radiative forcing and / or other impacts on climate, locally or globally.
See also the IPCC Report on Land Use, Land-Use Change, and
Forestry (IPCC, 2000).
Indirect land use change (iLUC): Indirect land use change refers
to shifts in land use induced by a change in the production level of
an agricultural product elsewhere, often mediated by markets or
driven by policies. For example, if agricultural land is diverted to
fuel production, forest clearance may occur elsewhere to replace
the former agricultural production. See also Afforestation, Deforestation
and Reforestation.
Land use, land use change and forestry (LULUCF): A greenhouse
gas (GHG) inventory sector that covers emissions and removals of
GHGs resulting from direct human-induced land use, land use change
and forestry activities excluding agricultural emissions. See also Agriculture,
Forestry and Other Land Use (AFOLU).
Land value capture: A financing mechanism usually based around
transit systems, or other infrastructure and services, that captures the
increased value of land due to improved accessibility.
Leakage: Phenomena whereby the reduction in emissions (relative to
a baseline) in a jurisdiction / sector associated with the implementation
of mitigation policy is offset to some degree by an increase outside
the jurisdiction / sector through induced changes in consumption, production,
prices, land use and / or trade across the jurisdictions / sectors.
Leakage can occur at a number of levels, be it a project, state, province,
nation, or world region. See also Rebound effect.
In the context of Carbon Dioxide Capture and Storage (CCS), ‘CO2 leakage’
refers to the escape of injected carbon dioxide (CO2) from the
storage location and eventual release to the atmosphere. In the context
of other substances, the term is used more generically, such as
for ‘methane (CH4) leakage’ (e. g., from fossil fuel extraction activities),
and ‘hydrofluorocarbon (HFC) leakage’ (e. g., from refrigeration and
air-conditioning systems).
Learning curve / rate: Decreasing cost-prices of technologies shown
as a function of increasing (total or yearly) supplies. The learning rate is
the percent decrease of the cost-price for every doubling of the cumulative
supplies (also called progress ratio).
Least Developed Countries (LDCs): A list of countries designated
by the Economic and Social Council of the United Nations (ECOSOC)
as meeting three criteria: (1) a low income criterion below a certain
threshold of gross national income per capita of between USD 750
and USD 900, (2) a human resource weakness based on indicators
of health, education, adult literacy, and (3) an economic vulnerability
weakness based on indicators on instability of agricultural production,
instability of export of goods and services, economic importance of
non-traditional activities, merchandise export concentration, and the
handicap of economic smallness. Countries in this category are eligible
for a number of programmes focused on assisting countries most in
need. These privileges include certain benefits under the articles of the
United Nations Framework Convention on Climate Change (UNFCCC).
See also Industrialized / developing countries.
Levelized cost of conserved carbon (LCCC): See Annex II.3.1.3 for
concepts and definition.


Levelized cost of conserved energy (LCCE): See Annex II.3.1.2 for
concepts and definition.
Levelized cost of energy (LCOE): See Annex II.3.1.1 for concepts
and definition.
Lifecycle assessment (LCA): A widely used technique defined by ISO
as a “compilation and evaluation of the inputs, outputs and the
potential environmental impacts of a product system throughout its
life cycle”. The results of LCA studies are strongly dependent on the
system boundaries within which they are conducted. The technique is
intended for relative comparison of two similar means to complete a
product. See also Annex II.6.3.
Likelihood: The chance of a specific outcome occurring, where this
might be estimated probabilistically. This is expressed in this report
using a standard terminology (Mastrandrea et al., 2010): virtually certain
– 100 % probability, very likely 90 – 100 %, likely 66 – 100 %,
about as likely as not 33 – 66 %, unlikely 0 – 33 %, very unlikely 0 – 10
%, exceptionally unlikely 0 – 1 %. Additional terms (more likely than
not > 50 – 100 %, and more unlikely than likely 0 – < 50 %) may also be
used when appropriate. Assessed likelihood is typeset in italics, e. g.,
very likely. See also Agreement, Confidence, Evidence and Uncertainty.
Lock-in: Lock-in occurs when a market is stuck with a standard even
though participants would be better off with an alternative.
Marginal abatement cost (MAC): The cost of one unit of additional
mitigation.
Market barriers: In the context of climate change mitigation, market
barriers are conditions that prevent or impede the diffusion of costeffective
technologies or practices that would mitigate greenhouse gas
(GHG) emissions.
Market-based mechanisms, GHG emissions: Regulatory approaches
using price mechanisms (e. g., taxes and auctioned emission permits),
among other instruments, to reduce the sources or enhance the sinks
of greenhouse gases (GHGs).
Market exchange rate (MER): The rate at which foreign currencies
are exchanged. Most economies post such rates daily and they vary
little across all the exchanges. For some developing economies, official
rates and black-market rates may differ significantly and the MER
is difficult to pin down. See also Purchasing power parity (PPP) and
Annex II.1.3 for the monetary conversion process applied throughout
this report.
Market failure: When private decisions are based on market prices
that do not reflect the real scarcity of goods and services but rather
reflect market distortions, they do not generate an efficient allocation
of resources but cause welfare losses. A market distortion is any event
in which a market reaches a market clearing price that is substantially
different from the price that a market would achieve while operating
under conditions of perfect competition and state enforcement of legal
contracts and the ownership of private property. Examples of factors
causing market prices to deviate from real economic scarcity are environmental
externalities, public goods, monopoly power, information
asymmetry, transaction costs, and non-rational behaviour. See also
Economic efficiency.
Material flow analysis (MFA): A systematic assessment of the flows
and stocks of materials within a system defined in space and time
(Brunner and Rechberger, 2004). See also Annex II.6.1.
Measures: In climate policy, measures are technologies, processes or
practices that contribute to mitigation, for example renewable energy
(RE) technologies, waste minimization processes, public transport commuting
practices.
Meeting of the Parties (CMP): The Conference of the Parties (COP)
to the United Nations Framework Convention on Climate Change
(UNFCCC) serves as the CMP, the supreme body of the Kyoto Protocol,
since the latter entered into force on 16 February 2005. Only Parties
to the Kyoto Protocol may participate in deliberations and make decisions.
Methane (CH4): One of the six greenhouse gases (GHGs) to be mitigated
under the Kyoto Protocol and is the major component of natural
gas and associated with all hydrocarbon fuels. Significant emissions
occur as a result of animal husbandry and agriculture and their management
represents a major mitigation option. See also Global Warming
Potential (GWP) and Annex II.9.1 for GWP values.
Methane recovery: Any process by which methane (CH4) emissions
(e. g., from oil or gas wells, coal beds, peat bogs, gas transmission pipelines,
landfills, or anaerobic digesters) are captured and used as a fuel
or for some other economic purpose (e. g., chemical feedstock).
Millennium Development Goals (MDGs): A set of eight time-bound
and measurable goals for combating poverty, hunger, disease, illiteracy,
discrimination against women and environmental degradation.
These goals were agreed to at the UN Millennium Summit in 2000
together with an action plan to reach the goals.
Mitigation (of climate change): A human intervention to reduce the
sources or enhance the sinks of greenhouse gases (GHGs). This report
also assesses human interventions to reduce the sources of other
substances which may contribute directly or indirectly to limiting climate
change, including, for example, the reduction of particulate matter
(PM) emissions that can directly alter the radiation balance (e. g.,
black carbon) or measures that control emissions of carbon monoxide,
nitrogen oxides (NOx), Volatile Organic Compounds (VOCs) and other


pollutants that can alter the concentration of tropospheric ozone (O3)
which has an indirect effect on the climate.
Mitigation capacity: A country’s ability to reduce anthropogenic
greenhouse gas (GHG) emissions or to enhance natural sinks, where
ability refers to skills, competencies, fitness, and proficiencies that a
country has attained and depends on technology, institutions, wealth,
equity, infrastructure, and information. Mitigative capacity is rooted in
a country’s sustainable development (SD) path.
Mitigation scenario: A plausible description of the future that
describes how the (studied) system responds to the implementation
of mitigation policies and measures. See also Baseline / reference,
Climate scenario, Emission scenario, Representative Concentration
Pathways (RCPs), Scenario, Shared socio-economic pathways, Socioeconomic
scenarios, SRES scenarios, Stabilization, and Transformation
pathways.
Models: Structured imitations of a system’s attributes and mechanisms
to mimic appearance or functioning of systems, for example, the
climate, the economy of a country, or a crop. Mathematical models
assemble (many) variables and relations (often in a computer code) to
simulate system functioning and performance for variations in parameters
and inputs.
Computable General Equilibrium (CGE) Model: A class of
economic models that use actual economic data (i. e., input / output
data), simplify the characterization of economic behaviour,
and solve the whole system numerically. CGE models specify all
economic relationships in mathematical terms and predict the
changes in variables such as prices, output and economic welfare
resulting from a change in economic policies, given information
about technologies and consumer preferences (Hertel, 1997). See
also General equilibrium analysis.
Integrated Model: Integrated models explore the interactions
between multiple sectors of the economy or components of particular
systems, such as the energy system. In the context of transformation
pathways, they refer to models that, at a minimum,
include full and disaggregated representations of the energy
system and its linkage to the overall economy that will allow for
consideration of interactions among different elements of that
system. Integrated models may also include representations of the
full economy, land use and land use change (LUC), and the climate
system. See also Integrated assessment.
Sectoral Model: In the context of this report, sectoral models
address only one of the core sectors that are discussed in this
report, such as buildings, industry, transport, energy supply, and
Agriculture, Forestry and Other Land Use (AFOLU).
Montreal Protocol: The Montreal Protocol on Substances that
Deplete the Ozone Layer was adopted in Montreal in 1987, and subsequently
adjusted and amended in London (1990), Copenhagen (1992),
Vienna (1995), Montreal (1997) and Beijing (1999). It controls the consumption
and production of chlorine- and bromine- containing chemicals
that destroy stratospheric ozone (O3), such as chlorofluorocarbons
(CFCs), methyl chloroform, carbon tetrachloride and many others.
Multi-criteria analysis (MCA): Integrates different decision parameters
and values without assigning monetary values to all parameters.
Multi-criteria analysis can combine quantitative and qualitative information.
Also referred to as multi-attribute analysis.
Multi-attribute analysis: See Multi-criteria analysis (MCA).
Multi-gas: Next to carbon dioxide (CO2), there are other forcing components
taken into account in, e. g., achieving reduction for a basket of
greenhouse gas (GHG) emissions (CO2, methane (CH4), nitrous oxide
(N2O), and fluorinated gases) or stabilization of CO2-equivalent concentrations
(multi-gas stabilization, including GHGs and aerosols).
Nationally Appropriate Mitigation Action (NAMA): Nationally
Appropriate Mitigation Actions are a concept for recognizing and
financing emission reductions by developing countries in a post-2012
climate regime achieved through action considered appropriate in a
given national context. The concept was first introduced in the Bali
Action Plan in 2007 and is contained in the Cancún Agreements.
Nitrogen oxides (NOX): Any of several oxides of nitrogen.
Nitrous oxide (N2O): One of the six greenhouse gases (GHGs) to be
mitigated under the Kyoto Protocol. The main anthropogenic source
of N2O is agriculture (soil and animal manure management), but
important contributions also come from sewage treatment, fossil fuel
combustion, and chemical industrial processes. N2O is also produced
naturally from a wide variety of biological sources in soil and water,
particularly microbial action in wet tropical forests. See also Global
Warming Potential (GWP) and Annex II.9.1 for GWP values.
Non-Annex I Parties / countries: Non-Annex I Parties are mostly
developing countries. Certain groups of developing countries are
recognized by the Convention as being especially vulnerable to the
adverse impacts of climate change, including countries with low-lying
coastal areas and those prone to desertification and drought. Others,
such as countries that rely heavily on income from fossil fuel production
and commerce, feel more vulnerable to the potential economic
impacts of climate change response measures. The Convention emphasizes
activities that promise to answer the special needs and concerns
of these vulnerable countries, such as investment, insurance, and technology
transfer. See also Annex I Parties / countries.
Normative analysis: Analysis in which judgments about the desirability
of various policies are made. The conclusions rest on value judgments
as well as on facts and theories. See also Descriptive analysis.


Ocean energy: Energy obtained from the ocean via waves, tidal
ranges, tidal and ocean currents, and thermal and saline gradients.
Offset (in climate policy): A unit of CO2-equivalent emissions that is
reduced, avoided, or sequestered to compensate for emissions occurring
elsewhere.
Oil sands and oil shale: Unconsolidated porous sands, sandstone
rock, and shales containing bituminous material that can be mined
and converted to a liquid fuel. See also Unconventional fuels.
Overshoot pathways: Emissions, concentration, or temperature
pathways in which the metric of interest temporarily exceeds, or ‘overshoots’,
the long-term goal.
Ozone (O3): Ozone, the triatomic form of oxygen (O3), is a gaseous
atmospheric constituent. In the troposphere, it is created both naturally
and by photochemical reactions involving gases resulting from human
activities (smog). Tropospheric O3 acts as a greenhouse gas (GHG). In
the stratosphere, it is created by the interaction between solar ultraviolet
radiation and molecular oxygen (O2). Stratospheric O3 plays a
dominant role in the stratospheric radiative balance. Its concentration
is highest in the O3 layer.
Paratransit: Denotes flexible passenger transportation, often but not
only in areas with low population density, that does not follow fixed
routes or schedules. Options include minibuses (matatus, marshrutka),
shared taxis and jitneys. Sometimes paratransit is also called community
transit.
Pareto optimum: A state in which no one’s welfare can be increased
without reducing someone else’s welfare. See also Economic efficiency.
Particulate matter (PM): Very small solid particles emitted during
the combustion of biomass and fossil fuels. PM may consist of a wide
variety of substances. Of greatest concern for health are particulates of
diameter less than or equal to 10 nanometers, usually designated as
PM10. See also Aerosol.
Passive design: The word ‘passive’ in this context implies the ideal
target that the only energy required to use the designed product or
service comes from renewable sources.
Path dependence: The generic situation where decisions, events, or
outcomes at one point in time constrain adaptation, mitigation, or
other actions or options at a later point in time.
Payback period: Mostly used in investment appraisal as financial
payback, which is the time needed to repay the initial investment by
the returns of a project. A payback gap exists when, for example, private
investors and micro-financing schemes require higher profitability
rates from renewable energy (RE) projects than from fossil-fired projects.
Energy payback is the time an energy project needs to deliver as
much energy as had been used for setting the project online. Carbon
payback is the time a renewable energy (RE) project needs to deliver
as much net greenhouse gas (GHG) savings (with respect to the fossil
reference energy system) as its realization has caused GHG emissions
from a perspective of lifecycle assessment (LCA) (including land use
changes (LUC) and loss of terrestrial carbon stocks).
Perfluorocarbons (PFCs): One of the six types of greenhouse gases
(GHGs) or groups of GHGs to be mitigated under the Kyoto Protocol.
PFCs are by-products of aluminium smelting and uranium enrichment.
They also replace chlorofluorocarbons (CFCs) in manufacturing semiconductors.
See also Global Warming Potential (GWP) and Annex II.9.1
for GWP values.
Photovoltaic cells (PV): Electronic devices that generate electricity
from light energy. See also Solar energy.
Policies (for mitigation of or adaptation to climate change): Policies
are a course of action taken and / or mandated by a government,
e. g., to enhance mitigation and adaptation. Examples of policies aimed
at mitigation are support mechanisms for renewable energy (RE) supplies,
carbon or energy taxes, fuel efficiency standards for automobiles.
See also Measures.
Polluter pays principle (PPP): The party causing the pollution is
responsible for paying for remediation or for compensating the damage.
Positive analysis: See Descriptive analysis.
Potential: The possibility of something happening, or of someone
doing something in the future. Different metrics are used throughout
this report for the quantification of different types of potentials, including
the following:
Technical potential: Technical potential is the amount by which
it is possible to pursue a specific objective through an increase in
deployment of technologies or implementation of processes and
practices that were not previously used or implemented. Quantification
of technical potentials may take into account other than
technical considerations, including social, economic and / or environmental
considerations.
Precautionary principle: A provision under Article 3 of the United
Nations Framework Convention on Climate Change (UNFCCC), stipulating
that the Parties should take precautionary measures to anticipate,
prevent, or minimize the causes of climate change and mitigate
its adverse effects. Where there are threats of serious or irreversible
damage, lack of full scientific certainty should not be used as a reason
to postpone such measures, taking into account that policies and measures
to deal with climate change should be cost-effective in order to
ensure global benefits at the lowest possible cost.


Precursors: Atmospheric compounds that are not greenhouse gases
(GHGs) or aerosols, but that have an effect on GHG or aerosol concentrations
by taking part in physical or chemical processes regulating
their production or destruction rates.
Pre-industrial: See Industrial Revolution.
Present value: Amounts of money available at different dates in the
future are discounted back to a present value, and summed to get the
present value of a series of future cash flows. See also Discounting.
Primary production: All forms of production accomplished by plants,
also called primary producers.
Primary energy: See Energy.
Private costs: Private costs are carried by individuals, companies or
other private entities that undertake an action, whereas social costs
include additionally the external costs on the environment and on society
as a whole. Quantitative estimates of both private and social costs
may be incomplete, because of difficulties in measuring all relevant
effects.
Production-based accounting: Production-based accounting provides
a measure of emissions released to the atmosphere for the production
of goods and services by a certain entity (e. g., person, firm,
country, or region). See also Consumption-based accounting.
Public good: Public goods are non-rivalrous (goods whose consumption
by one consumer does not prevent simultaneous consumption by
other consumers) and non-excludable (goods for which it is not possible
to prevent people who have not paid for it from having access
to it).
Purchasing power parity (PPP): The purchasing power of a currency
is expressed using a basket of goods and services that can be bought
with a given amount in the home country. International comparison
of, for example, gross domestic products (GDP) of countries can be
based on the purchasing power of currencies rather than on current
exchange rates. PPP estimates tend to lower per capita GDP in industrialized
countries and raise per capita GDP in developing countries.
(PPP is also an acronym for polluter pays principle). See also Market
exchange rate (MER) and Annex II.1.3 for the monetary conversion
process applied throughout this report.
Radiation management: See Solar Radiation Management.
Radiative forcing: Radiative forcing is the change in the net, downward
minus upward, radiative flux (expressed in W m – 2) at the tropopause
or top of atmosphere due to a change in an external driver of
climate change, such as, for example, a change in the concentration of
carbon dioxide (CO2) or the output of the sun. For the purposes of this
report, radiative forcing is further defined as the change relative to the
year 1750 and refers to a global and annual average value.
Rebound effect: Phenomena whereby the reduction in energy consumption
or emissions (relative to a baseline) associated with the
implementation of mitigation measures in a jurisdiction is offset to
some degree through induced changes in consumption, production,
and prices within the same jurisdiction. The rebound effect is most typically
ascribed to technological energy efficiency (EE) improvements.
See also Leakage.
Reducing Emissions from Deforestation and Forest Degradation
(REDD): An effort to create financial value for the carbon stored
in forests, offering incentives for developing countries to reduce
emissions from forested lands and invest in low-carbon paths to sustainable
development (SD). It is therefore a mechanism for mitigation
that results from avoiding deforestation. REDD+ goes beyond
reforestation and forest degradation, and includes the role of conservation,
sustainable management of forests and enhancement of
forest carbon stocks. The concept was first introduced in 2005 in the
th Session of the Conference of the Parties (COP) in Montreal and
later given greater recognition in the 13th Session of the COP in 2007
at Bali and inclusion in the Bali Action Plan which called for “policy
approaches and positive incentives on issues relating to reducing
emissions to deforestation and forest degradation in developing
countries (REDD) and the role of conservation, sustainable management
of forests and enhancement of forest carbon stock in developing
countries”. Since then, support for REDD has increased and has
slowly become a framework for action supported by a number of
countries.
Reference scenario: See Baseline / reference.
Reforestation: Planting of forests on lands that have previously
sustained forests but that have been converted to some other use.
Under the United Nations Framework Convention on Climate Change
(UNFCCC) and the Kyoto Protocol, reforestation is the direct humaninduced
conversion of non-forested land to forested land through
planting, seeding, and / or human-induced promotion of natural seed
sources, on land that was previously forested but converted to nonforested
land. For the first commitment period of the Kyoto Protocol,
reforestation activities will be limited to reforestation occurring on
those lands that did not contain forest on 31 December 1989.
For a discussion of the term forest and related terms such as afforestation,
reforestation and deforestation, see the IPCC Report on Land Use,
Land-Use Change and Forestry (IPCC, 2000). See also the Report on
Definitions and Methodological Options to Inventory Emissions from
Direct Human-induced Degradation of Forests and Devegetation of
Other Vegetation Types (IPCC, 2003).
Renewable energy (RE): See Energy.


Representative Concentration Pathways (RCPs): Scenarios that
include time series of emissions and concentrations of the full suite of
greenhouse gases (GHGs) and aerosols and chemically active gases, as
well as land use / land cover (Moss et al., 2008). The word representative
signifies that each RCP provides only one of many possible scenarios
that would lead to the specific radiative forcing characteristics. The
term pathway emphasizes that not only the long-term concentration
levels are of interest, but also the trajectory taken over time to reach
that outcome (Moss et al., 2010).
RCPs usually refer to the portion of the concentration pathway extending
up to 2100, for which Integrated Assessment Models produced
corresponding emission scenarios. Extended Concentration Pathways
(ECPs) describe extensions of the RCPs from 2100 to 2500 that were
calculated using simple rules generated by stakeholder consultations,
and do not represent fully consistent scenarios.
Four RCPs produced from Integrated Assessment Models were selected
from the published literature and are used in the present IPCC Assessment
as a basis for the climate predictions and projections presented
in WGI AR5 Chapters 11 to 14:
RCP2.6 One pathway where radiative forcing peaks at approximately
W m – 2 before 2100 and then declines (the corresponding
ECP assuming constant emissions after 2100);
RCP4.5 and RCP6.0 Two intermediate stabilization pathways in
which radiative forcing is stabilized at approximately 4.5 W m – 2
and 6.0 W m – 2 after 2100 (the corresponding ECPs assuming constant
concentrations after 2150);
RCP8.5 One high pathway for which radiative forcing reaches
greater than 8.5 W m – 2 by 2100 and continues to rise for some
amount of time (the corresponding ECP assuming constant emissions
after 2100 and constant concentrations after 2250).
For further description of future scenarios, see WGI AR5 Box 1.1. See
also Baseline / reference, Climate prediction, Climate projection, Climate
scenario, Shared socio-economic pathways, Socio-economic scenario,
SRES scenarios, and Transformation pathway.
Reservoir: A component of the climate system, other than the atmosphere,
which has the capacity to store, accumulate or release a substance
of concern, for example, carbon, a greenhouse gas (GHG) or a
precursor. Oceans, soils and forests are examples of reservoirs of carbon.
Pool is an equivalent term (note that the definition of pool often
includes the atmosphere). The absolute quantity of the substance of
concern held within a reservoir at a specified time is called the stock.
In the context of Carbon Dioxide Capture and Storage (CCS), this term
is sometimes used to refer to a geological carbon dioxide (CO2) storage
location. See also Sequestration.
Resilience: The capacity of social, economic, and environmental systems
to cope with a hazardous event or trend or disturbance, responding
or reorganizing in ways that maintain their essential function, identity,
and structure, while also maintaining the capacity for adaptation,
learning, and transformation (Arctic Council, 2013).
Revegetation: A direct human-induced activity to increase carbon
stocks on sites through the establishment of vegetation that covers a
minimum area of 0.05 hectares and does not meet the definitions of
afforestation and reforestation contained here (UNFCCC, 2002).
Risk: In this report, the term risk is often used to refer to the potential,
when the outcome is uncertain, for adverse consequences on lives,
livelihoods, health, ecosystems and species, economic, social and cultural
assets, services (including environmental services), and infrastructure.
Risk assessment: The qualitative and / or quantitative scientific
estimation of risks.
Risk management: The plans, actions, or policies to reduce the
likelihood and / or consequences of a given risk.
Risk perception: The subjective judgment that people make
about the characteristics and severity of a risk.
Risk tradeoff: The change in the portfolio of risks that occurs
when a countervailing risk is generated (knowingly or inadvertently)
by an intervention to reduce the target risk (Wiener and
Graham, 2009). See also Adverse side-effect, and Co-benefit.
Risk transfer: The practice of formally or informally shifting the
risk of financial consequences for particular negative events from
one party to another.
Scenario: A plausible description of how the future may develop
based on a coherent and internally consistent set of assumptions about
key driving forces (e. g., rate of technological change (TC), prices) and
relationships. Note that scenarios are neither predictions nor forecasts,
but are useful to provide a view of the implications of developments
and actions. See also Baseline / reference, Climate scenario, Emission
scenario, Mitigation scenario, Representative Concentration Pathways
(RCPs), Shared socio-economic pathways, Socioeconomic scenarios,
SRES scenarios, Stabilization, and Transformation pathway.
Scope 1, Scope 2, and Scope 3 emissions: See Emissions.
Secondary energy: See Primary energy.
Sectoral Models: See Models.
Sensitivity analysis: Sensitivity analysis with respect to quantitative
analysis assesses how changing assumptions alters the outcomes. For


example, one chooses different values for specific parameters and reruns
a given model to assess the impact of these changes on model
output.
Sequestration: The uptake (i. e., the addition of a substance of concern
to a reservoir) of carbon containing substances, in particular carbon
dioxide (CO2), in terrestrial or marine reservoirs. Biological sequestration
includes direct removal of CO2 from the atmosphere through
land-use change (LUC), afforestation, reforestation, revegetation, carbon
storage in landfills, and practices that enhance soil carbon in agriculture
(cropland management, grazing land management). In parts of
the literature, but not in this report, (carbon) sequestration is used to
refer to Carbon Dioxide Capture and Storage (CCS).
Shadow pricing: Setting prices of goods and services that are not, or
are incompletely, priced by market forces or by administrative regulation,
at the height of their social marginal value. This technique is used
in cost-benefit analysis (CBA).
Shared socio-economic pathways (SSPs): Currently, the idea of
SSPs is developed as a basis for new emissions and socio-economic
scenarios. An SSP is one of a collection of pathways that describe
alternative futures of socio-economic development in the absence of
climate policy intervention. The combination of SSP-based socio-economic
scenarios and Representative Concentration Pathway (RCP)-
based climate projections should provide a useful integrative frame
for climate impact and policy analysis. See also Baseline / reference, Climate
scenario, Emission scenario, Mitigation scenario, Scenario, SRES
scenarios, Stabilization, and Transformation pathway.
Short-lived climate pollutant (SLCP): Pollutant emissions that have
a warming influence on climate and have a relatively short lifetime in
the atmosphere (a few days to a few decades). The main SLCPs are
black carbon (BC) (‘soot’), methane (CH4) and some hydroflurorcarbons
(HFCs) some of which are regulated under the Kyoto Protocol.
Some pollutants of this type, including CH4, are also precursors to the
formation of tropospheric ozone (O3), a strong warming agent. These
pollutants are of interest for at least two reasons. First, because they
are short-lived, efforts to control them will have prompt effects on
global warming — unlike long-lived pollutants that build up in the
atmosphere and respond to changes in emissions at a more sluggish
pace. Second, many of these pollutants also have adverse local impacts
such as on human health.
Sink: Any process, activity or mechanism that removes a greenhouse
gas (GHG), an aerosol, or a precursor of a GHG or aerosol from the
atmosphere.
Smart grids: A smart grid uses information and communications technology
to gather data on the behaviours of suppliers and consumers in
the production, distribution, and use of electricity. Through automated
responses or the provision of price signals, this information can then
be used to improve the efficiency, reliability, economics, and sustainability
of the electricity network.
Smart meter: A meter that communicates consumption of electricity
or gas back to the utility provider.
Social cost of carbon (SCC): The net present value of climate damages
(with harmful damages expressed as a positive number) from one
more tonne of carbon in the form of carbon dioxide (CO2), conditional
on a global emissions trajectory over time.
Social costs: See Private costs.
Socio-economic scenario: A scenario that describes a possible future
in terms of population, gross domestic product (GDP), and other socioeconomic
factors relevant to understanding the implications of climate
change. See also Baseline / reference, Climate scenario, Emission scenario,
Mitigation scenario, Representative Concentration Pathways
(RCPs), Scenario, Shared socio-economic pathways, SRES scenarios,
Stabilization, and Transformation pathway.
Solar energy: Energy from the sun. Often the phrase is used to mean
energy that is captured from solar radiation either as heat, as light that
is converted into chemical energy by natural or artificial photosynthesis,
or by photovoltaic panels and converted directly into electricity.
Solar Radiation Management (SRM): Solar Radiation Management
refers to the intentional modification of the earth’s shortwave
radiative budget with the aim to reduce climate change according to a
given metric (e. g., surface temperature, precipitation, regional impacts,
etc.). Artificial injection of stratospheric aerosols and cloud brightening
are two examples of SRM techniques. Methods to modify some fastresponding
elements of the longwave radiative budget (such as cirrus
clouds), although not strictly speaking SRM, can be related to SRM.
SRM techniques do not fall within the usual definitions of mitigation
and adaptation (IPCC, 2012, p. 2). See also Carbon Dioxide Removal
(CDR) and Geoengineering.
Source: Any process, activity or mechanism that releases a greenhouse
gas (GHG), an aerosol or a precursor of a GHG or aerosol into
the atmosphere. Source can also refer to, e. g., an energy source.
Spill-over effect: The effects of domestic or sector mitigation measures
on other countries or sectors. Spill-over effects can be positive
or negative and include effects on trade, (carbon) leakage, transfer of
innovations, and diffusion of environmentally sound technology and
other issues.
SRES scenarios: SRES scenarios are emission scenarios developed by
Nakićenović and Swart (2000) and used, among others, as a basis for
some of the climate projections shown in Chapters 9 to 11 of IPCC
(2001) and Chapters 10 and 11 of IPCC (2007) as well as WGI AR5. The


following terms are relevant for a better understanding of the structure
and use of the set of SRES scenarios:
Scenario family: Scenarios that have a similar demographic, societal,
economic and technical change storyline. Four scenario families
comprise the SRES scenario set: A1, A2, B1, and B2.
Illustrative Scenario: A scenario that is illustrative for each of the
six scenario groups reflected in the Summary for Policymakers of
Nakićenović and Swart (2000). They include four revised marker
scenarios for the scenario groups A1B, A2, B1, B2, and two additional
scenarios for the A1FI and A1T groups. All scenario groups
are equally sound.
Marker Scenario: A scenario that was originally posted in draft
form on the SRES website to represent a given scenario family. The
choice of markers was based on which of the initial quantifications
best reflected the storyline, and the features of specific models.
Markers are no more likely than other scenarios, but are considered
by the SRES writing team as illustrative of a particular storyline.
They are included in revised form in Nakićenović and Swart
(2000). These scenarios received the closest scrutiny of the entire
writing team and via the SRES open process. Scenarios were also
selected to illustrate the other two scenario groups.
Storyline: A narrative description of a scenario (or family of scenarios),
highlighting the main scenario characteristics, relationships
between key driving forces and the dynamics of their evolution.
See also Baseline / reference, Climate scenario, Emission scenario,
Mitigation scenario, Representative Concentration Pathways (RCPs),
Shared socio-economic pathways, Socio-economic scenario, Stabilization,
and Transformation pathway.
Stabilization (of GHG or CO2-equivalent concentration): A state
in which the atmospheric concentrations of one greenhouse gas (GHG)
(e. g., carbon dioxide) or of a CO2-equivalent basket of GHGs (or a combination
of GHGs and aerosols) remains constant over time.
Standards: Set of rules or codes mandating or defining product performance
(e. g., grades, dimensions, characteristics, test methods, and
rules for use). Product, technology or performance standards establish
minimum requirements for affected products or technologies. Standards
impose reductions in greenhouse gas (GHG) emissions associated
with the manufacture or use of the products and / or application
of the technology.
Stratosphere: The highly stratified region of the atmosphere above the
troposphere extending from about 10 km (ranging from 9 km at high
latitudes to 16 km in the tropics on average) to about 50 km altitude.
Structural change: Changes, for example, in the relative share of
gross domestic product (GDP) produced by the industrial, agricultural,
or services sectors of an economy, or more generally, systems transformations
whereby some components are either replaced or potentially
substituted by other components.
Subsidiarity: The principle that decisions of government (other things
being equal) are best made and implemented, if possible, at the lowest
most decentralized level, that is, closest to the citizen. Subsidiarity is
designed to strengthen accountability and reduce the dangers of making
decisions in places remote from their point of application. The principle
does not necessarily limit or constrain the action of higher orders
of government, but merely counsels against the unnecessary assumption
of responsibilities at a higher level.
Sulphur hexafluoride (SF6): One of the six types of greenhouse gases
(GHGs) to be mitigated under the Kyoto Protocol. SF6 is largely used
in heavy industry to insulate high-voltage equipment and to assist in
the manufacturing of cable-cooling systems and semi-conductors. See
Global Warming Potential (GWP) and Annex II.9.1 for GWP values.
Sustainability: A dynamic process that guarantees the persistence of
natural and human systems in an equitable manner.
Sustainable development (SD): Development that meets the needs
of the present without compromising the ability of future generations
to meet their own needs (WCED, 1987).
Technical potential: See Potential.
Technological change (TC): Economic models distinguish autonomous
(exogenous), endogenous, and induced TC.
Autonomous (exogenous) technological change: Autonomous
(exogenous) technological change is imposed from outside the
model (i. e., as a parameter), usually in the form of a time trend
affecting factor and / or energy productivity and therefore energy
demand and / or economic growth.
Endogenous technological change: Endogenous technological
change is the outcome of economic activity within the model
(i. e., as a variable) so that factor productivity or the choice of technologies
is included within the model and affects energy demand
and / or economic growth.
Induced technological change: Induced technological change
implies endogenous technological change but adds further
changes induced by policies and measures, such as carbon taxes
triggering research and development efforts.
Technological learning: See Learning curve / rate.
Technological / knowledge spillovers: Any positive externality that
results from purposeful investment in technological innovation or
development (Weyant and Olavson, 1999).


Territorial emissions: See Emissions.
Trace gas: A minor constituent of the atmosphere, next to nitrogen
and oxygen that together make up 99 % of all volume. The most important
trace gases contributing to the greenhouse effect are carbon
dioxide (CO2), ozone (O3), methane (CH4), nitrous oxide (N2O), perfluorocarbons
(PFCs), chlorofluorocarbons (CFCs), hydrofluorocarbons
(HFCs), sulphur hexafluoride (SF6) and water vapour (H2O).
Tradable (green) certificates scheme: A market-based mechanism
to achieve an environmentally desirable outcome (renewable energy
(RE) generation, energy efficiency (EE) requirements) in a cost-effective
way by allowing purchase and sale of certificates representing under
and over-compliance respectively with a quota.
Tradable (emission) permit: See Emission permit.
Tradable quota system: See Emissions trading.
Transaction costs: The costs that arise from initiating and completing
transactions, such as finding partners, holding negotiations, consulting
with lawyers or other experts, monitoring agreements, or opportunity
costs, such as lost time or resources (Michaelowa et al., 2003).
Transformation pathway: The trajectory taken over time to meet
different goals for greenhouse gas (GHG) emissions, atmospheric concentrations,
or global mean surface temperature change that implies
a set of economic, technological, and behavioural changes. This can
encompass changes in the way energy and infrastructure is used and
produced, natural resources are managed, institutions are set up,
and in the pace and direction of technological change (TC). See also
Baseline / reference, Climate scenario, Emission scenario, Mitigation
scenario, Representative Concentration Pathways (RCPs), Scenario,
Shared socio-economic pathways, Socio-economic scenarios, SRES scenarios,
and Stabilization.
Transient climate response: See Climate sensitivity.
Transit oriented development (TOD): Urban development within
walking distance of a transit station, usually dense and mixed with the
character of a walkable environment.
Troposphere: The lowest part of the atmosphere, from the surface
to about 10 km in altitude at mid-latitudes (ranging from 9 km at
high latitudes to 16 km in the tropics on average), where clouds and
weather phenomena occur. In the troposphere, temperatures generally
decrease with height. See also Stratosphere.
Uncertainty: A cognitive state of incomplete knowledge that can
result from a lack of information or from disagreement about what
is known or even knowable. It may have many types of sources, from
imprecision in the data to ambiguously defined concepts or terminology,
or uncertain projections of human behaviour. Uncertainty can
therefore be represented by quantitative measures (e. g., a probability
density function) or by qualitative statements (e. g., reflecting the judgment
of a team of experts) (see Moss and Schneider, 2000; Manning
et al., 2004; Mastrandrea et al., 2010). See also Agreement, Evidence,
Confidence and Likelihood.
Unconventional resources: A loose term to describe fossil fuel
reserves that cannot be extracted by the well-established drilling
and mining processes that dominated extraction of coal, gas, and oil
throughout the 20th century. The boundary between conventional and
unconventional resources is not clearly defined. Unconventional oils
include oil shales, tar sands / bitumen, heavy and extra heavy crude oils,
and deep-sea oil occurrences. Unconventional natural gas includes gas
in Devonian shales, tight sandstone formations, geopressured aquifers,
coal-bed gas, and methane (CH4) in clathrate structures (gas hydrates)
(Rogner, 1997).
United Nations Framework Convention on Climate Change
(UNFCCC): The Convention was adopted on 9 May 1992 in New York
and signed at the 1992 Earth Summit in Rio de Janeiro by more than
countries and the European Community. Its ultimate objective is
the ‘stabilisation of greenhouse gas concentrations in the atmosphere
at a level that would prevent dangerous anthropogenic interference
with the climate system’. It contains commitments for all Parties under
the principle of ‘common but differentiated responsibilities’. Under the
Convention, Parties included in Annex I aimed to return greenhouse
gas (GHG) emissions not controlled by the Montreal Protocol to 1990
levels by the year 2000. The convention entered in force in March
. In 1997, the UNFCCC adopted the Kyoto Protocol.
Urban heat island: See Heat island.
Verified Emissions Reductions: Emission reductions that are verified
by an independent third party outside the framework of the United
Nations Framework Convention on Climate Change (UNFCCC) and its
Kyoto Protocol. Also called ‘Voluntary Emission Reductions’.
Volatile Organic Compounds (VOCs): Important class of organic
chemical air pollutants that are volatile at ambient air conditions.
Other terms used to represent VOCs are hydrocarbons (HCs), reactive
organic gases (ROGs) and non-methane volatile organic compounds
(NMVOCs). NMVOCs are major contributors — together with nitrogen
oxides (NOX), and carbon monoxide (CO) — to the formation of photochemical
oxidants such as ozone (O3).
Voluntary action: Informal programmes, self-commitments, and declarations,
where the parties (individual companies or groups of companies)
entering into the action set their own targets and often do their
own monitoring and reporting.


Voluntary agreement (VA): An agreement between a government
authority and one or more private parties to achieve environmental
objectives or to improve environmental performance beyond compliance
with regulated obligations. Not all voluntary agreements are truly
voluntary; some include rewards and / or penalties associated with joining
or achieving commitments.
Voluntary Emission Reductions: See Verified Emissions Reductions.
Watts per square meter (W m-2): See Radiative forcing.
Wind energy: Kinetic energy from air currents arising from uneven
heating of the earth’s surface. A wind turbine is a rotating machine for
converting the kinetic energy of the wind to mechanical shaft energy
to generate electricity. A windmill has oblique vanes or sails and the
mechanical power obtained is mostly used directly, for example, for
water pumping. A wind farm, wind project, or wind power plant is a
group of wind turbines interconnected to a common utility system
through a system of transformers, distribution lines, and (usually) one
substation.


Acronyms and chemical symbols
AAU Assigned Amount Unit
ADB Asian Development Bank
AfDB African Development Bank
AFOLU Agriculture, Forestry and Other Land Use
AME Asian Modeling Exercise
AMPERE Assessment of Climate Change Mitigation Pathways
and Evaluation of the Robustness of Mitigation Cost
Estimates
AOSIS Alliance of Small Island States
APEC Asia-Pacific Economic Cooperation
AR4 IPCC Fourth Assessment Report
ASEAN Association of Southeast Asian Nations
ASIA Non-OECD Asia
BAMs Border adjustment measures
BAT Best available technology
BAU Business-as-usual
BC Black carbon
BECCS Bioenergy with carbon dioxide capture and storage
BEVs Battery electric vehicles
BNDES Brazilian Development Bank
BOD Biochemical Oxygen Demand
BRT Bus rapid transit
C Carbon
C40 C40 Cities Climate Leadership Group
CBA Cost-benefit analysis
CBD Convention on Biological Diversity
CBD Central business district
CCA Climate Change Agreement
CCE Cost of conserved energy
CCL Climate Change Levy
CCS Carbon dioxide capture and storage
CDM Clean Development Mechanism
CDR Carbon dioxide removal
CEA Cost-effectiveness analysis
CERs Certified Emissions Reductions
CFCs Chlorofluorocarbons
CGE Computable general equilibrium
CH4 Methane
CHP Combined heat and power
CIFs Climate Investment Funds
CMIP Coupled Model Intercomparison Project
CNG Compressed natural gas
CO Carbon monoxide
CO2 Carbon dioxide
CO2eq Carbon dioxide-equivalent, CO2-equivalent
COD Chemical oxygen demand
COP Conference of the Parties
CRF Capital recovery factor
CSP Concentrated solar power
CTCN Climate Technology Centre and Network
DAC Direct air capture
DAC Development Assistance Committee
DALYs Disability-adjusted life years
DANN Designated National Authority
DCs Developing countries
DRI Direct reduced iron
DSM Demand-side management
EAF Electric arc furnace
EAS East Asia
ECA Economic Commission for Africa
ECN Energy Research Center of the Netherlands
ECOWAS Economic Community of West African States
EDGAR Emissions Database for Global Atmospheric Research
EE Energy efficiency
EIA U. S. Energy Information Administration
EITs Economies in Transition
EMF Energy Modeling Forum
EPA U. S. Environmental Protection Agency
EPC Energy performance contracting
ERU Emissions reduction unit
ESCOs Energy service companies
ETS Emissions Trading System
EU European Union
EU ETS European Union Emissions Trading Scheme
EVs Electric vehicles
F-gases Fluorinated gases
FAO Food and Agriculture Organization of the United
Nations
FAQ Frequently asked questions
FAR IPCC First Assessment Report
FCVs Fuel cell vehicles
FDI Foreign Direct Investment
FE Final energy
FEEM Fondazione Eni Enrico Mattei
FF&I Fossil fuel and industrial
FIT Feed-in tariff
FOLU Forestry and Other Land Use
FSF Fast-start Finance
G20 Group of Twenty Finance Ministers
G8 Group of Eight Finance Ministers
GATT General Agreement on Tariffs and Trade
GCAM Global Change Assessment Model
GCF Green Climate Fund
GCM General Circulation Model
GDP Gross domestic product
GEA Global Energy Assessment
GEF Global Environment Facility
GHG Greenhouse gas
GNE Gross national expenditure
GSEP Global Superior Energy Performance Partnership
GTM Global Timber Model
GTP Global Temperature Change Potential
GWP Global Warming Potential


H2 Hydrogen
HCFCs Hydrochlorofluorocarbons
HDI Human Development Index
HDVs Heavy-duty vehicles
HFCs Hydrofluorocarbon
HFC-23 Trifluoromethane
Hg Mercury
HHV Higher heating value
HIC High-income countries
HVAC Heating, ventilation and air conditioning
IAEA International Atomic Energy Agency
IAMC Integrated Assessment Modelling Consortium
ICAO International Civil Aviation Organization
ICE Internal combustion engine
ICLEI International Council for Local Environmental Initiatives
ICT Information and communication technology
IDB Inter-American Development Bank
IDP Integrated Design Process
IEA International Energy Agency
IET International Emissions Trading
IGCC Integrated gasification combined cycle
IIASA International Institute for Applied Systems Analysis
iLUC Indirect land-use change
IMF International Monetary Fund
IMO International Maritime Organization
INT TRA International transport
IO International organization
IP Intellectual property
IPAT Income-Population-Affluence-Technology
IPCC Intergovernmental Panel on Climate Change
IRENA International Renewable Energy Agency
IRR Internal rate of return
ISO International Organization for Standardization
JI Joint Implementation
JICA Japan International Cooperation Agency
KfW Kreditanstalt für Wiederaufbau
LAM Latin America
LCA Lifecycle Assessment
LCCC Levelized costs of conserved carbon
LCD Liquid crystal display
LCCE Levelized cost of conserved energy
LCOE Levelized costs of energy
LDCs Least Developed Countries
LDCF Least Developed Countries Fund
LDVs Light-duty vehicles
LED Light-emitting diode
LHV Lower heating value
LIC Low-income countries
LIMITS Low Climate Impact Scenarios and Implications of
Required Tight Emission Control Strategies
LMC Lower-middle income countries
LNG Liquefied natural gas
LPG Liquefied petroleum gas
LUC Land-use change
LULUCF Land Use, Land-Use Change and Forestry
MAC Marginal abatement cost
MAF Middle East and Africa
MAGICC Model for the Assessment of Greenhouse Gas Induced
Climate Change
MCA Multi-criteria analysis
MDB Multilateral Development Bank
MDGs Millennium Development Goals
MEF Major Economies Forum on Energy and Climate
MER Market exchange rate
MFA Material flow analysis
MNA Middle East and North Africa
MRIO Multi-Regional Input-Output Analysis
MRV Measurement, reporting, and verification
MSW Municipal solid waste
N Nitrogen
N2O Nitrous oxide
NAM North America
NAMA Nationally Appropriate Mitigation Action
NAPA National Adaptation Programmes of Action
NAS U. S. National Academy of Science
NF3 Nitrogen trifluoride
NGCC Natural gas combined cycle
NGO Non-governmental organization
NH3 Ammonia
NOx Nitrogen oxides
NPV Net present value
NRC U. S. National Research Council
NREL U. S. National Renewable Energy Laboratory
NZEB Net zero energy buildings
O3 Ozone
O&M Operation and maintenance
OC Organic carbon
ODA Official development assistance
ODS Ozone-depleting substances
OECD Organisation for Economic Co-operation and Development
OPEC Organization of Petroleum Exporting Countries
PACE Property Assessed Clean Energy
PAS South-East Asia and Pacific
PBL Netherlands Environmental Assessment Agency
PC Pulverized Coal
PDF Probability density function
PEVs Plug-in electric vehicles
PFC Perfluorocarbons
PHEVs Plug-in hybrid electric vehicles
PIK Potsdam Institute for Climate Impact Research
PM Particulate Matter
PNNL Pacific Northwest National Laboratories
POEDC Pacific OECD 1990 members (Japan, Aus, NZ)
PPP Polluter pays principle


PPP Purchasing power parity
PV Photovoltaic
R&D Research and development
RCPs Representative Concentration Pathways
RD&D Research, Development and Demonstration
RE Renewable energy
RECIPE Report on Energy and Climate Policy in Europe
REDD Reducing Emissions From Deforestation and Forest
Degradation
REEEP Renewable Energy and Energy Efficiency Partnership
RES Renewable energy sources
RGGI Regional Greenhouse Gas Initiative
RoSE Roadmaps towards Sustainable Energy futures
ROW Rest of the World
RPS Renewable portfolio standards
SAR IPCC Second Assessment Report
SAS South Asia
SCC Social cost of carbon
SCCF Special Climate Change Fund
SCP Sustainable consumption and production
SD Sustainable development
SF6 Sulphur hexafluoride
SLCP Short-lived climate pollutant
SMEs Small and Medium Enterprises
SO2 Sulphur dioxide
SPM Summary for Policymakers
SRES IPCC Special Report on Emission Scenarios
SREX IPCC Special Report on Managing the Risks of Extreme
Events and Disasters to Advance Climate Change
Adaptation
SRM Solar radiation management
SRREN IPCC Special Report on Renewable Energy Sources and
Climate Change Mitigation
SRCSS IPCC Special Report on Carbon dioxide Capture and
Storage
SSA Sub-Saharan Africa
SUVs Sport Utility Vehicles
SWF Social welfare function
TAR IPCC Third Assessment Report
TC Technological change
TCR Transient climate response
Th Thorium
TNAs Technology Needs Assessments
TOD Transit-oriented development
TPES Total primary energy supply
TRIPs Trade Related Intellectual Property Rights
TT Technology transfer
U Uranium
UHI Urban heat island
UMC Upper-middle income countries
UN United Nations
UN DESA United Nations Department for Economic and Social
Affairs
UNCCD United Nations Convention to Combat Desertification
UNCSD United Nations Conference on Sustainable Development
UNDP United Nations Development Programme
UNEP United Nations Environment Programme
UNESCO United Nations Educational, Scientific and Cultural
Organization
UNFCCC United Nations Framework Convention on Climate
Change
UNIDO United Nations Industrial Development Organization
USD U. S. Dollars
VAs Voluntary agreements
VOCs Volatile Organic Compounds
VKT Vehicle kilometers travelled
WACC Weighted costs of capital
WBCSD World Business Council on Sustainable Development
WCED World Commission on Environment and Development
WCI Western Climate Initiative
WEU Western Europe
WGI IPCC Working Group I
WGII IPCC Working Group II
WGIII IPCC Working Group III
WHO World Health Organization
WTP Willingness to pay
WWTP Wastewater plant
WTO World Trade Organization



II Glossary
Editorial Board Co-Chairs:
John Agard (Trinidad and Tobago), E. Lisa F. Schipper (Sweden)
Editorial Board:
Joern Birkmann (Germany), Maximiliano Campos (Costa Rica), Carolina Dubeux (Brazil),
Yukihiro Nojiri (Japan), Lennart Olsson (Sweden), Balgis Osman-Elasha (Sudan), Mark Pelling
(UK), Michael J. Prather (USA), Marta G. Rivera-Ferre (Spain), Oliver C. Ruppel (Namibia),
Asbury Sallenger (USA), Kirk R. Smith (USA), Asuncion L. St. Clair (Norway)
TSU Facilitation:
Katharine J. Mach (USA), Michael D. Mastrandrea (USA), T. Eren Bilir (USA)
ANNEX

Annex II Glossary
II
Abrupt climate change
A large-scale change in the climate system that takes place over a few
decades or less, persists (or is anticipated to persist) for at least a few
decades, and causes substantial disruptions in human and natural systems.
Access to food
One of the three components underpinning food security, the other two
being availability and utilization. Access to food is dependent on (1) the
affordability of food (i.e., people have income or other resources to
exchange for food); (2) satisfactory allocation within the household or
society; and (3) preference (i.e., it is what people want to eat, influenced
by socio-cultural norms). See also Food security.
Acclimatization
A change in functional or morphological traits occurring once or repeatedly
(e.g., seasonally) during the lifetime of an individual organism in its
natural environment. Through acclimatization the individual maintains
performance across a range of environmental conditions. For a clear
differentiation between findings in laboratory and field studies, the term
acclimation is used in ecophysiology for the respective phenomena
when observed in well-defined experimental settings. The term
(adaptive) plasticity characterizes the generally limited scope of changes
in phenotype that an individual can reach through the process of
acclimatization.
Adaptability
See Adaptive capacity.
Adaptation1
The process of adjustment to actual or expected climate and its effects.
In human systems, adaptation seeks to moderate or avoid harm or exploit
beneficial opportunities. In some natural systems, human intervention
may facilitate adjustment to expected climate and its effects.
Incremental adaptation Adaptation actions where the central
aim is to maintain the essence and integrity of a system or process
at a given scale.2
Transformational adaptation Adaptation that changes the
fundamental attributes of a system in response to climate and its
effects.
See also Autonomous adaptation, Evolutionary adaptation, and
Transformation.
Adaptation assessment
The practice of identifying options to adapt to climate change and
evaluating them in terms of criteria such as availability, benefits, costs,
effectiveness, efficiency, and feasibility.
Adaptation constraint
Factors that make it harder to plan and implement adaptation actions
or that restrict options.
Adaptation deficit
The gap between the current state of a system and a state that
minimizes adverse impacts from existing climate conditions and
variability.
Adaptation limit
The point at which an actor’s objectives (or system needs) cannot be
secured from intolerable risks through adaptive actions.
Hard adaptation limit No adaptive actions are possible to avoid
intolerable risks.
Soft adaptation limit Options are currently not available to avoid
intolerable risks through adaptive action.
Adaptation needs
The circumstances requiring action to ensure safety of populations and
security of assets in response to climate impacts.
Adaptation opportunity
Factors that make it easier to plan and implement adaptation actions,
that expand adaptation options, or that provide ancillary co-benefits.
Adaptation options
The array of strategies and measures that are available and appropriate
for addressing adaptation needs. They include a wide range of actions
that can be categorized as structural, institutional, or social.
Adaptive capacity
The ability of systems, institutions, humans, and other organisms to
adjust to potential damage, to take advantage of opportunities, or to
respond to consequences.3
Adaptive management
A process of iteratively planning, implementing, and modifying strategies
for managing resources in the face of uncertainty and change. Adaptive
management involves adjusting approaches in response to observations
of their effect and changes in the system brought on by resulting
feedback effects and other variables.
Aggregate impacts
Total impacts integrated across sectors and/or regions. The aggregation
of impacts requires knowledge of (or assumptions about) the relative
importance of different impacts. Measures of aggregate impacts include,
for example, the total number of people affected, or the total economic
costs, and are usually bound by time, place, and/or sector.
Ancillary benefits
See Co-benefits.
Anomaly
The deviation of a variable from its value averaged over a reference
period.
Reflecting progress in science, this glossary entry differs in breadth and focus from the entry used in the Fourth Assessment Report and other IPCC reports.
This definition builds from the definition used in Park et al. (2012).
This glossary entry builds from definitions used in previous IPCC reports and the Millennium Ecosystem Assessment (MEA, 2005).


Anthropogenic
Resulting from or produced by human activities.
Anthropogenic emissions
Emissions of greenhouse gases, greenhouse gas precursors, and
aerosols caused by human activities. These activities include the burning
of fossil fuels, deforestation, land use changes, livestock production,
fertilization, waste management, and industrial processes.
Arid zone
Areas where vegetation growth is severely constrained due to limited
water availability. For the most part, the native vegetation of arid zones
is sparse. There is high rainfall variability, with annual averages below
mm. Crop farming in arid zones requires irrigation.
Atlantic Multi-decadal Oscillation/Variability (AMO/AMV)
A multi-decadal (65- to 75-year) fluctuation in the North Atlantic, in
which sea surface temperatures showed warm phases during roughly
to 1880 and 1930 to 1960 and cool phases during 1905 to 1925
and 1970 to 1990 with a range of approximately 0.4°C. See AMO Index
in WGI AR5 Box 2.5.
Atmosphere-Ocean General Circulation Model (AOGCM)
See Climate model.
Attribution
See Detection and attribution.
Autonomous adaptation
Adaptation in response to experienced climate and its effects, without
planning explicitly or consciously focused on addressing climate change.
Also referred to as spontaneous adaptation.
Baseline/reference
The baseline (or reference) is the state against which change is measured.
A baseline period is the period relative to which anomalies are computed.
The baseline concentration of a trace gas is that measured at a location
not influenced by local anthropogenic emissions.
Biodiversity
The variability among living organisms from terrestrial, marine, and
other ecosystems. Biodiversity includes variability at the genetic, species,
and ecosystem levels.4
Bioenergy
Energy derived from any form of biomass such as recently living organisms
or their metabolic by-products.
Biofuel
A fuel, generally in liquid form, developed from organic matter or
combustible oils produced by living or recently living plants. Examples
of biofuel include alcohol (bioethanol), black liquor from the papermanufacturing
process, and soybean oil.
First-generation manufactured biofuel First-generation
manufactured biofuel is derived from grains, oilseeds, animal fats,
and waste vegetable oils with mature conversion technologies.
Second-generation biofuel Second-generation biofuel uses nontraditional
biochemical and thermochemical conversion processes
and feedstock mostly derived from the lignocellulosic fractions of,
for example, agricultural and forestry residues, municipal solid
waste, etc.
Third-generation biofuel Third-generation biofuel would be
derived from feedstocks such as algae and energy crops by
advanced processes still under development.
These second- and third-generation biofuels produced through new
processes are also referred to as next-generation or advanced biofuels,
or advanced biofuel technologies.
Biomass
The total mass of living organisms in a given area or volume; dead
plant material can be included as dead biomass. Biomass burning is the
burning of living and dead vegetation.
Biome
A biome is a major and distinct regional element of the biosphere,
typically consisting of several ecosystems (e.g., forests, rivers, ponds,
swamps within a region). Biomes are characterized by typical communities
of plants and animals.
Biosphere
The part of the Earth system comprising all ecosystems and living
organisms, in the atmosphere, on land (terrestrial biosphere), or in the
oceans (marine biosphere), including derived dead organic matter, such
as litter, soil organic matter, and oceanic detritus.
Boundary organization
A bridging institution, social arrangement, or network that acts as an
intermediary between science and policy.
Business As Usual (BAU)
Business as usual projections are based on the assumption that operating
practices and policies remain as they are at present. Although baseline
scenarios could incorporate some specific features of BAU scenarios
(e.g., a ban on a specific technology), BAU scenarios imply that no
practices or policies other than the current ones are in place. See also
Baseline/reference, Climate scenario, Emission scenario, Representative
Concentration Pathways, Scenario, Socioeconomic scenario, and SRES
scenarios.
Capacity building
The practice of enhancing the strengths and attributes of, and resources
available to, an individual, community, society, or organization to respond
to change.
This glossary entry builds from definitions used in the Global Biodiversity Assessment (Heywood, 1995) and the Millennium Ecosystem Assessment (MEA, 2005).

Annex II Glossary
II
Carbon cycle
The term used to describe the flow of carbon (in various forms, e.g., as
carbon dioxide) through the atmosphere, ocean, terrestrial and marine
biosphere, and lithosphere. In this report, the reference unit for the
global carbon cycle is GtC or equivalently PgC (1015g).
Carbon dioxide (CO2)
A naturally occurring gas, also a by-product of burning fossil fuels from
fossil carbon deposits, such as oil, gas, and coal, of burning biomass, of
land use changes, and of industrial processes (e.g., cement production).
It is the principal anthropogenic greenhouse gas that affects the Earth’s
radiative balance. It is the reference gas against which other greenhouse
gases are measured and therefore has a Global Warming Potential of 1.
Carbon dioxide (CO2) fertilization
The enhancement of the growth of plants as a result of increased
atmospheric carbon dioxide (CO2) concentration.
Carbon sequestration
See Uptake.
Clean Development Mechanism (CDM)
A mechanism defined under Article 12 of the Kyoto Protocol through
which investors (governments or companies) from developed (Annex
B) countries may finance greenhouse gas emission reduction or removal
projects in developing (Non-Annex B) countries, and receive Certified
Emission Reduction Units for doing so, which can be credited towards
the commitments of the respective developed countries. The CDM is
intended to facilitate the two objectives of promoting sustainable
development in developing countries and of helping industrialized
countries to reach their emissions commitments in a cost-effective way.
Climate
Climate in a narrow sense is usually defined as the average weather, or
more rigorously, as the statistical description in terms of the mean and
variability of relevant quantities over a period of time ranging from months
to thousands or millions of years. The classical period for averaging
these variables is 30 years, as defined by the World Meteorological
Organization. The relevant quantities are most often surface variables
such as temperature, precipitation, and wind. Climate in a wider sense
is the state, including a statistical description, of the climate system.
Climate-altering pollutants (CAPs)
Gases and particles released from human activities that affect the
climate either directly, through mechanisms such as radiative forcing
from changes in greenhouse gas concentrations, or indirectly, by, for
example, affecting cloud formation or the lifetime of greenhouse gases
in the atmosphere. CAPs include both those pollutants that have a
warming effect on the atmosphere, such as CO2, and those with cooling
effects, such as sulfates.
Climate change
Climate change refers to a change in the state of the climate that can
be identified (e.g., by using statistical tests) by changes in the mean
and/or the variability of its properties, and that persists for an extended
period, typically decades or longer. Climate change may be due to
natural internal processes or external forcings such as modulations of
the solar cycles, volcanic eruptions, and persistent anthropogenic
changes in the composition of the atmosphere or in land use. Note
that the Framework Convention on Climate Change (UNFCCC), in its
Article 1, defines climate change as: “a change of climate which is
attributed directly or indirectly to human activity that alters the
composition of the global atmosphere and which is in addition to
natural climate variability observed over comparable time periods.” The
UNFCCC thus makes a distinction between climate change attributable
to human activities altering the atmospheric composition, and climate
variability attributable to natural causes. See also Climate change
commitment and Detection and Attribution.
Climate change commitment
Due to the thermal inertia of the ocean and slow processes in the
cryosphere and land surfaces, the climate would continue to change
even if the atmospheric composition were held fixed at today’s values.
Past change in atmospheric composition leads to a committed climate
change, which continues for as long as a radiative imbalance persists
and until all components of the climate system have adjusted to a new
state. The further change in temperature after the composition of the
atmosphere is held constant is referred to as the constant composition
temperature commitment or simply committed warming or warming
commitment. Climate change commitment includes other future
changes, for example, in the hydrological cycle, in extreme weather
events, in extreme climate events, and in sea level change. The constant
emission commitment is the committed climate change that would
result from keeping anthropogenic emissions constant and the zero
emission commitment is the climate change commitment when emissions
are set to zero. See also Climate change.
Climate extreme (Extreme weather or climate event)
See Extreme weather event.
Climate feedback
An interaction in which a perturbation in one climate quantity causes
a change in a second, and the change in the second quantity ultimately
leads to an additional change in the first. A negative feedback is one in
which the initial perturbation is weakened by the changes it causes; a
positive feedback is one in which the initial perturbation is enhanced.
In this Assessment Report, a somewhat narrower definition is often
used in which the climate quantity that is perturbed is the global mean
surface temperature, which in turn causes changes in the global
radiation budget. In either case, the initial perturbation can either be
externally forced or arise as part of internal variability.
Climate governance
Purposeful mechanisms and measures aimed at steering social systems
towards preventing, mitigating, or adapting to the risks posed by climate
change (Jagers and Stripple, 2003).
Climate model (spectrum or hierarchy)
A numerical representation of the climate system based on the physical,
chemical, and biological properties of its components, their interactions,
and feedback processes, and accounting for some of its known properties.
The climate system can be represented by models of varying complexity;
that is, for any one component or combination of components, a
spectrum or hierarchy of models can be identified, differing in such


aspects as the number of spatial dimensions, the extent to which
physical, chemical, or biological processes are explicitly represented, or
the level at which empirical parameterizations are involved. Coupled
Atmosphere-Ocean General Circulation Models (AOGCMs) provide a
representation of the climate system that is near or at the most
comprehensive end of the spectrum currently available. There is an
evolution towards more complex models with interactive chemistry and
biology. Climate models are applied as a research tool to study and
simulate the climate, and for operational purposes, including monthly,
seasonal, and interannual climate predictions. See also Earth System
Model.
Climate prediction
A climate prediction or climate forecast is the result of an attempt to
produce (starting from a particular state of the climate system) an
estimate of the actual evolution of the climate in the future, for example,
at seasonal, interannual, or decadal time scales. Because the future
evolution of the climate system may be highly sensitive to initial
conditions, such predictions are usually probabilistic in nature. See also
Climate projection, Climate scenario, and Predictability.
Climate projection
A climate projection is the simulated response of the climate system to
a scenario of future emission or concentration of greenhouse gases and
aerosols, generally derived using climate models. Climate projections
are distinguished from climate predictions by their dependence on the
emission/concentration/radiative-forcing scenario used, which is in turn
based on assumptions concerning, for example, future socioeconomic
and technological developments that may or may not be realized. See
also Climate scenario.
Climate-resilient pathways
Iterative processes for managing change within complex systems in
order to reduce disruptions and enhance opportunities associated with
climate change.
Climate scenario
A plausible and often simplified representation of the future climate,
based on an internally consistent set of climatological relationships that
has been constructed for explicit use in investigating the potential
consequences of anthropogenic climate change, often serving as input
to impact models. Climate projections often serve as the raw material
for constructing climate scenarios, but climate scenarios usually require
additional information such as the observed current climate. See also
Emission scenario and Scenario.
Climate sensitivity
In IPCC reports, equilibrium climate sensitivity (units: °C) refers to the
equilibrium (steady state) change in the annual global mean surface
temperature following a doubling of the atmospheric equivalent carbon
dioxide concentration. Owing to computational constraints, the
equilibrium climate sensitivity in a climate model is sometimes estimated
by running an atmospheric general circulation model coupled to a
mixed-layer ocean model, because equilibrium climate sensitivity is
largely determined by atmospheric processes. Efficient models can be run
to equilibrium with a dynamic ocean. The climate sensitivity parameter
(units: °C (W m–2)–1) refers to the equilibrium change in the annual
global mean surface temperature following a unit change in radiative
forcing.
The effective climate sensitivity (units: °C) is an estimate of the global
mean surface temperature response to doubled carbon dioxide
concentration that is evaluated from model output or observations for
evolving non-equilibrium conditions. It is a measure of the strengths of
the climate feedbacks at a particular time and may vary with forcing
history and climate state, and therefore may differ from equilibrium
climate sensitivity.
The transient climate response (units: °C) is the change in the global
mean surface temperature, averaged over a 20-year period, centered
at the time of atmospheric carbon dioxide doubling, in a climate model
simulation in which CO2 increases at 1% yr–1. It is a measure of the
strength and rapidity of the surface temperature response to greenhouse
gas forcing.
Climate system
The climate system is the highly complex system consisting of five major
components: the atmosphere, the hydrosphere, the cryosphere, the
lithosphere, and the biosphere, and the interactions among them. The
climate system evolves in time under the influence of its own internal
dynamics and because of external forcings such as volcanic eruptions,
solar variations, and anthropogenic forcings such as the changing
composition of the atmosphere and land use change.
Climate variability
Climate variability refers to variations in the mean state and other
statistics (such as standard deviations, the occurrence of extremes,
etc.) of the climate on all spatial and temporal scales beyond that of
individual weather events. Variability may be due to natural internal
processes within the climate system (internal variability), or to variations
in natural or anthropogenic external forcing (external variability). See
also Climate change.
Climate velocity
The speed at which isolines of a specified climate variable travel across
landscapes or seascapes due to changing climate. For example, climate
velocity for temperature is the speed at which isotherms move due to
changing climate (km yr–1) and is calculated as the temporal change
in temperature (°C yr–1) divided by the current spatial gradient in
temperature (°C km–1). It can be calculated using additional climate
variables such as precipitation or can be based on the climatic niche of
organisms.
Climatic driver (Climate driver)
A changing aspect of the climate system that influences a component
of a human or natural system.
CMIP3 and CMIP5
Phases three and five of the Coupled Model Intercomparison Project
(CMIP3 and CMIP5), coordinating and archiving climate model
simulations based on shared model inputs by modeling groups from
around the world. The CMIP3 multi-model data set includes projections
using SRES scenarios. The CMIP5 data set includes projections using the
Representative Concentration Pathways.

Annex II Glossary
II
Coastal squeeze
A narrowing of coastal ecosystems and amenities (e.g., beaches, salt
marshes, mangroves, and mud and sand flats) confined between
landward-retreating shorelines (from sea level rise and/or erosion) and
naturally or artificially fixed shorelines including engineering defenses
(e.g., seawalls), potentially making the ecosystems or amenities vanish.
Co-benefits
The positive effects that a policy or measure aimed at one objective
might have on other objectives, irrespective of the net effect on overall
social welfare. Co-benefits are often subject to uncertainty and depend
on local circumstances and implementation practices, among other
factors. Co-benefits are also referred to as ancillary benefits.
Community-based adaptation
Local, community-driven adaptation. Community-based adaptation
focuses attention on empowering and promoting the adaptive capacity
of communities. It is an approach that takes context, culture, knowledge,
agency, and preferences of communities as strengths.
Confidence
The validity of a finding based on the type, amount, quality, and
consistency of evidence (e.g., mechanistic understanding, theory, data,
models, expert judgment) and on the degree of agreement. Confidence
is expressed qualitatively (Mastrandrea et al., 2010). See Box 1-1. See
also Uncertainty.
Contextual vulnerability (Starting-point vulnerability)
A present inability to cope with external pressures or changes, such as
changing climate conditions. Contextual vulnerability is a characteristic
of social and ecological systems generated by multiple factors and
processes (O’Brien et al., 2007).
Convection
Vertical motion driven by buoyancy forces arising from static instability,
usually caused by near-surface cooling or increases in salinity in the
case of the ocean and near-surface warming or cloud-top radiative
cooling in the case of the atmosphere. In the atmosphere, convection
gives rise to cumulus clouds and precipitation and is effective at both
scavenging and vertically transporting chemical species. In the ocean,
convection can carry surface waters to deep within the ocean.
Coping
The use of available skills, resources, and opportunities to address,
manage, and overcome adverse conditions, with the aim of achieving
basic functioning of people, institutions, organizations, and systems in
the short to medium term.5
Coping capacity
The ability of people, institutions, organizations, and systems, using
available skills, values, beliefs, resources, and opportunities, to address,
manage, and overcome adverse conditions in the short to medium
term.6
Coral bleaching
Loss of coral pigmentation through the loss of intracellular symbiotic
algae (known as zooxanthellae) and/or loss of their pigments.
Cryosphere
All regions on and beneath the surface of the Earth and ocean
where water is in solid form, including sea ice, lake ice, river ice, snow
cover, glaciers and ice sheets, and frozen ground (which includes
permafrost).
Cultural impacts
Impacts on material and ecological aspects of culture and the lived
experience of culture, including dimensions such as identity, community
cohesion and belonging, sense of place, worldview, values, perceptions,
and tradition. Cultural impacts are closely related to ecological impacts,
especially for iconic and representational dimensions of species and
landscapes. Culture and cultural practices frame the importance and
value of the impacts of change, shape the feasibility and acceptability
of adaptation options, and provide the skills and practices that enable
adaptation.
Dead zones
Extremely hypoxic (i.e., low-oxygen) areas in oceans and lakes, caused
by excessive nutrient input from human activities coupled with other
factors that deplete the oxygen required to support many marine
organisms in bottom and near-bottom water. See also Eutrophication
and Hypoxic events.
Decarbonization
The process by which countries or other entities aim to achieve a lowcarbon
economy, or by which individuals aim to reduce their consumption
of carbon.
Deforestation
Conversion of forest to non-forest. For a discussion of the term forest
and related terms such as afforestation, reforestation, and deforestation
see the IPCC Special Report on Land Use, Land-Use Change, and Forestry
(IPCC, 2000). See also the report on Definitions and Methodological
Options to Inventory Emissions from Direct Human-induced Degradation
of Forests and Devegetation of Other Vegetation Types (IPCC, 2003).
Desertification
Land degradation in arid, semi-arid, and dry sub-humid areas resulting
from various factors, including climatic variations and human activities.
Land degradation in arid, semi-arid, and dry sub-humid areas is reduction
or loss of the biological or economic productivity and complexity of
rainfed cropland, irrigated cropland, or range, pasture, forest, and
woodlands resulting from land uses or from a process or combination
of processes, including processes arising from human activities and
habitation patterns, such as (1) soil erosion caused by wind and/or
water; (2) deterioration of the physical, chemical, biological, or economic
properties of soil; and (3) long-term loss of natural vegetation (UNCCD,
).
This glossary entry builds from the definition used in UNISDR (2009) and IPCC (2012a).
This glossary entry builds from the definition used in UNISDR (2009) and IPCC (2012a).


Detection and attribution
Detection of change is defined as the process of demonstrating that
climate or a system affected by climate has changed in some defined
statistical sense, without providing a reason for that change. An identified
change is detected in observations if its likelihood of occurrence by
chance due to internal variability alone is determined to be small, for
example, <10%. Attribution is defined as the process of evaluating the
relative contributions of multiple causal factors to a change or event
with an assignment of statistical confidence (Hegerl et al., 2010).
Detection of impacts of climate change
For a natural, human, or managed system, identification of a change
from a specified baseline. The baseline characterizes behavior in the
absence of climate change and may be stationary or non-stationary
(e.g., due to land use change).
Disadvantaged populations
Sectors of a society that are marginalized, often because of low
socioeconomic status, low income, lack of access to basic services such
as health or education, lack of power, race, gender, religion, or poor
access to communication technologies.
Disaster
Severe alterations in the normal functioning of a community or a society
due to hazardous physical events interacting with vulnerable social
conditions, leading to widespread adverse human, material, economic,
or environmental effects that require immediate emergency response
to satisfy critical human needs and that may require external support
for recovery.
Disaster management
Social processes for designing, implementing, and evaluating strategies,
policies, and measures that promote and improve disaster preparedness,
response, and recovery practices at different organizational and societal
levels.
Disaster risk
The likelihood within a specific time period of disaster. See Disaster.
Disaster Risk Management (DRM)
Processes for designing, implementing, and evaluating strategies,
policies, and measures to improve the understanding of disaster risk,
foster disaster risk reduction and transfer, and promote continuous
improvement in disaster preparedness, response, and recovery practices,
with the explicit purpose of increasing human security, well-being,
quality of life, and sustainable development.
Disaster Risk Reduction (DRR)
Denotes both a policy goal or objective, and the strategic and instrumental
measures employed for anticipating future disaster risk; reducing existing
exposure, hazard, or vulnerability; and improving resilience.
Discounting
A mathematical operation making monetary (or other) amounts received
or expended at different times (years) comparable across time. The
discounter uses a fixed or possibly time-varying discount rate (>0) from
year to year that makes future value worth less today.
Disturbance regime
Frequency, intensity, and types of disturbances of ecological systems,
such as fires, insect or pest outbreaks, floods, and droughts.
Diurnal temperature range
The difference between the maximum and minimum temperature
during a 24-hour period.
Downscaling
Downscaling is a method that derives local- to regional-scale (10 to
km) information from larger-scale models or data analyses. Two
main methods exist: dynamical downscaling and empirical/statistical
downscaling. The dynamical method uses the output of regional climate
models, global models with variable spatial resolution, or high-resolution
global models. The empirical/statistical methods develop statistical
relationships that link the large-scale atmospheric variables with local/
regional climate variables. In all cases, the quality of the driving model
remains an important limitation on quality of the downscaled information.
Drought
A period of abnormally dry weather long enough to cause a serious
hydrological imbalance. Drought is a relative term; therefore any
discussion in terms of precipitation deficit must refer to the particular
precipitation-related activity that is under discussion. For example,
shortage of precipitation during the growing season impinges on crop
production or ecosystem function in general (due to soil moisture
drought, also termed agricultural drought), and during the runoff and
percolation season primarily affects water supplies (hydrological drought).
Storage changes in soil moisture and groundwater are also affected
by increases in actual evapotranspiration in addition to reductions in
precipitation. A period with an abnormal precipitation deficit is defined
as a meteorological drought. A megadrought is a very lengthy and
pervasive drought, lasting much longer than normal, usually a decade
or more. For the corresponding indices, see WGI AR5 Box 2.4.
Dynamic Global Vegetation Model (DGVM)
A model that simulates vegetation development and dynamics through
space and time, as driven by climate and other environmental changes.
Early warning system
The set of capacities needed to generate and disseminate timely and
meaningful warning information to enable individuals, communities,
and organizations threatened by a hazard to prepare to act promptly
and appropriately to reduce the possibility of harm or loss.7
Earth System Model (ESM)
A coupled atmosphere-ocean general circulation model in which a
representation of the carbon cycle is included, allowing for interactive
calculation of atmospheric CO2 or compatible emissions. Additional
components (e.g., atmospheric chemistry, ice sheets, dynamic vegetation,
nitrogen cycle, but also urban or crop models) may be included. See
also Climate model.
This glossary entry builds from the definition used in UNISDR (2009) and IPCC (2012a).

Annex II Glossary
II
Ecophysiological process
Processes in which individual organisms respond continuously to
environmental variability or change, such as climate change, generally
at a microscopic or sub-organ scale. Ecophysiological mechanisms
underpin individual organisms’ tolerance to environmental stress, and
comprise a broad range of responses defining the absolute tolerances
by individuals of environmental conditions. Ecophysiological responses
may scale up to control species’ geographic ranges.
Ecosystem
A functional unit consisting of living organisms, their non-living
environment, and the interactions within and between them. The
components included in a given ecosystem and its spatial boundaries
depend on the purpose for which the ecosystem is defined: in some cases
they are relatively sharp, while in others they are diffuse. Ecosystem
boundaries can change over time. Ecosystems are nested within other
ecosystems, and their scale can range from very small to the entire
biosphere. In the current era, most ecosystems either contain people as
key organisms, or are influenced by the effects of human activities in
their environment.
Ecosystem approach
A strategy for the integrated management of land, water, and living
resources that promotes conservation and sustainable use in an equitable
way. An ecosystem approach is based on the application of scientific
methodologies focused on levels of biological organization, which
encompass the essential structure, processes, functions, and interactions
of organisms and their environment. It recognizes that humans, with
their cultural diversity, are an integral component of many ecosystems.
The ecosystem approach requires adaptive management to deal with
the complex and dynamic nature of ecosystems and the absence of
complete knowledge or understanding of their functioning. Priority
targets are conservation of biodiversity and of the ecosystem structure
and functioning, in order to maintain ecosystem services.8
Ecosystem-based adaptation
The use of biodiversity and ecosystem services as part of an overall
adaptation strategy to help people to adapt to the adverse effects of
climate change. Ecosystem-based adaptation uses the range of
opportunities for the sustainable management, conservation, and
restoration of ecosystems to provide services that enable people to
adapt to the impacts of climate change. It aims to maintain and increase
the resilience and reduce the vulnerability of ecosystems and people in
the face of the adverse effects of climate change. Ecosystem-based
adaptation is most appropriately integrated into broader adaptation
and development strategies (CBD, 2009).
Ecosystem services
Ecological processes or functions having monetary or non-monetary
value to individuals or society at large. These are frequently classified as
(1) supporting services such as productivity or biodiversity maintenance,
(2) provisioning services such as food, fiber, or fish, (3) regulating services
such as climate regulation or carbon sequestration, and (4) cultural
services such as tourism or spiritual and aesthetic appreciation.
El Niño-Southern Oscillation (ENSO)
The term El Niño was initially used to describe a warm-water current
that periodically flows along the coast of Ecuador and Peru, disrupting
the local fishery. It has since become identified with a basin-wide
warming of the tropical Pacific Ocean east of the dateline. This oceanic
event is associated with a fluctuation of a global-scale tropical and
subtropical surface pressure pattern called the Southern Oscillation. This
coupled atmosphere-ocean phenomenon, with preferred time scales of
to about 7 years, is known as the El Niño-Southern Oscillation (ENSO).
It is often measured by the surface pressure anomaly difference between
Tahiti and Darwin or the sea surface temperatures in the central and
eastern equatorial Pacific. During an ENSO event, the prevailing trade
winds weaken, reducing upwelling and altering ocean currents such that
the sea surface temperatures warm, further weakening the trade winds.
This event has a great impact on the wind, sea surface temperature,
and precipitation patterns in the tropical Pacific. It has climatic effects
throughout the Pacific region and in many other parts of the world,
through global teleconnections. The cold phase of ENSO is called La
Niña. For the corresponding indices, see WGI AR5 Box 2.5.
Emergent risk
A risk that arises from the interaction of phenomena in a complex
system, for example, the risk caused when geographic shifts in human
population in response to climate change lead to increased vulnerability
and exposure of populations in the receiving region.
Emission scenario
A plausible representation of the future development of emissions of
substances that are potentially radiatively active (e.g., greenhouse
gases, aerosols) based on a coherent and internally consistent set
of assumptions about driving forces (such as demographic and
socioeconomic development, technological change) and their key
relationships. Concentration scenarios, derived from emission scenarios,
are used as input to a climate model to compute climate projections. In
IPCC (1992) a set of emission scenarios was presented, which were used
as a basis for the climate projections in IPCC (1996). These emission
scenarios are referred to as the IS92 scenarios. In the IPCC Special
Report on Emissions Scenarios (Nakićenović and Swart, 2000) emission
scenarios, the so-called SRES scenarios, were published, some of which
were used, among others, as a basis for the climate projections
presented in Chapters 9 to 11 of IPCC (2001) and Chapters 10 and 11
of IPCC (2007). New emission scenarios for climate change, the four
Representative Concentration Pathways, were developed for, but
independently of, the present IPCC assessment. See also Climate
scenario and Scenario.
Ensemble
A collection of model simulations characterizing a climate prediction or
projection. Differences in initial conditions and model formulation result
in different evolutions of the modeled system and may give information
on uncertainty associated with model error and error in initial conditions
in the case of climate forecasts and on uncertainty associated with
model error and with internally generated climate variability in the case
of climate projections.
This glossary entry builds from definitions used in CBD (2000), MEA (2005), and the Fourth Assessment Report.


Environmental migration
Human migration involves movement over a significant distance and
duration. Environmental migration refers to human migration where
environmental risks or environmental change plays a significant role in
influencing the migration decision and destination. Migration may
involve distinct categories such as direct, involuntary, and temporary
displacement due to weather-related disasters; voluntary relocation as
settlements and economies become less viable; or planned resettlement
encouraged by government actions or incentives. All migration decisions
are multi-causal, and hence it is not meaningful to describe any migrant
flow as being solely for environmental reasons.
Environmental services
See Ecosystem services.
Eutrophication
Over-enrichment of water by nutrients such as nitrogen and phosphorus.
It is one of the leading causes of water quality impairment. The two most
acute symptoms of eutrophication are hypoxia (or oxygen depletion)
and harmful algal blooms. See also Dead zones.
Evolutionary adaptation
For a population or species, change in functional characteristics as a result
of selection acting on heritable traits. The rate of evolutionary adaptation
depends on factors such as strength of selection, generation turnover time,
and degree of outcrossing (as opposed to inbreeding). See also Adaptation.
Exposure
The presence of people, livelihoods, species or ecosystems, environmental
functions, services, and resources, infrastructure, or economic, social, or
cultural assets in places and settings that could be adversely affected.
External forcing
External forcing refers to a forcing agent outside the climate system
causing a change in the climate system. Volcanic eruptions, solar variations,
and anthropogenic changes in the composition of the atmosphere and
land use change are external forcings. Orbital forcing is also an external
forcing as the insolation changes with orbital parameters eccentricity,
tilt, and precession of the equinox.
Externalities/external costs/external benefits
Externalities arise from a human activity when agents responsible for
the activity do not take full account of the activity’s impacts on others’
production and consumption possibilities, and no compensation exists
for such impacts. When the impacts are negative, they are external costs.
When the impacts are positive, they are external benefits.
Extratropical cyclone
A large-scale (of order 1000 km) storm in the middle or high latitudes
having low central pressure and fronts with strong horizontal gradients
in temperature and humidity. A major cause of extreme wind speeds
and heavy precipitation especially in wintertime.
Extreme climate event
See Extreme weather event.
Extreme sea level
See Storm surge.
Extreme weather event
An extreme weather event is an event that is rare at a particular place
and time of year. Definitions of rare vary, but an extreme weather event
would normally be as rare as or rarer than the 10th or 90th percentile
of a probability density function estimated from observations. By
definition, the characteristics of what is called extreme weather may vary
from place to place in an absolute sense. When a pattern of extreme
weather persists for some time, such as a season, it may be classed as
an extreme climate event, especially if it yields an average or total that
is itself extreme (e.g., drought or heavy rainfall over a season).
Famine
Scarcity of food over an extended period and over a large geographical
area, such as a country, or lack of access to food for socioeconomic,
political, or cultural reasons. Famines may be caused by climate-related
extreme events such as droughts or floods and by disease, war, or other
factors.
Feedback
See Climate feedback.
Fire weather
Weather conditions conducive to triggering and sustaining wild fires,
usually based on a set of indicators and combinations of indicators
including temperature, soil moisture, humidity, and wind. Fire weather
does not include the presence or absence of fuel load.
Fitness (Darwinian)
Fitness is the relative capacity of an individual or genotype to both
survive and reproduce, quantified as the average contribution of the
genotype to the gene pool of the next generations. During evolution,
natural selection favors functions providing greater fitness such that
the functions become more common over generations.
Flood
The overflowing of the normal confines of a stream or other body of
water, or the accumulation of water over areas not normally submerged.
Floods include river (fluvial) floods, flash floods, urban floods, pluvial
floods, sewer floods, coastal floods, and glacial lake outburst floods.
Food security
A state that prevails when people have secure access to sufficient
amounts of safe and nutritious food for normal growth, development,
and an active and healthy life.9 See also Access to food.
Food system
A food system includes the suite of activities and actors in the food chain
(i.e., producing, processing and packaging, storing and transporting,
trading and retailing, and preparing and consuming food); and the
outcome of these activities relating to the three components underpinning
food security (i.e., access to food, utilization of food, and food availability),
all of which need to be stable over time. Food security is therefore
This glossary entry builds from definitions used in FAO (2000) and previous IPCC reports.

Annex II Glossary
II
underpinned by food systems, and is an emergent property of the
behavior of the whole food system. Food insecurity arises when any
aspect of the food system is stressed.
Forecast
See Climate prediction and Climate projection.
General Circulation Model (GCM)
See Climate model.
Geoengineering
Geoengineering refers to a broad set of methods and technologies that
aim to deliberately alter the climate system in order to alleviate the
impacts of climate change. Most, but not all, methods seek to either
(1) reduce the amount of absorbed solar energy in the climate system
(Solar Radiation Management) or (2) increase net carbon sinks from
the atmosphere at a scale sufficiently large to alter climate (Carbon
Dioxide Removal). Scale and intent are of central importance. Two key
characteristics of geoengineering methods of particular concern are that
they use or affect the climate system (e.g., atmosphere, land, or ocean)
globally or regionally and/or could have substantive unintended effects
that cross national boundaries. Geoengineering is different from weather
modification and ecological engineering, but the boundary can be fuzzy
(IPCC, 2012b, p. 2).
Global change
A generic term to describe global scale changes in systems, including
the climate system, ecosystems, and social-ecological systems.
Global Climate Model (also referred to as General
Circulation Model, both abbreviated as GCM)
See Climate model.
Global mean surface temperature
An estimate of the global mean surface air temperature. However, for
changes over time, only anomalies, as departures from a climatology,
are used, most commonly based on the area-weighted global average
of the sea surface temperature anomaly and land surface air temperature
anomaly.
Greenhouse effect
The infrared radiative effect of all infrared-absorbing constituents in the
atmosphere. Greenhouse gases, clouds, and (to a small extent) aerosols
absorb terrestrial radiation emitted by the Earth’s surface and elsewhere
in the atmosphere. These substances emit infrared radiation in all
directions, but, everything else being equal, the net amount emitted to
space is normally less than would have been emitted in the absence of
these absorbers because of the decline of temperature with altitude
in the troposphere and the consequent weakening of emission. An
increase in the concentration of greenhouse gases increases the
magnitude of this effect; the difference is sometimes called the enhanced
greenhouse effect. The change in a greenhouse gas concentration
because of anthropogenic emissions contributes to an instantaneous
radiative forcing. Surface temperature and troposphere warm in
response to this forcing, gradually restoring the radiative balance at
the top of the atmosphere.
Greenhouse gas (GHG)
Greenhouse gases are those gaseous constituents of the atmosphere,
both natural and anthropogenic, that absorb and emit radiation at
specific wavelengths within the spectrum of terrestrial radiation emitted
by the Earth’s surface, the atmosphere itself, and clouds. This property
causes the greenhouse effect. Water vapor (H2O), carbon dioxide (CO2),
nitrous oxide (N2O), methane (CH4), and ozone (O3) are the primary
greenhouse gases in the Earth’s atmosphere. Moreover, there are a
number of entirely human-made greenhouse gases in the atmosphere,
such as the halocarbons and other chlorine- and bromine-containing
substances, dealt with under the Montreal Protocol. Beside CO2, N2O,
and CH4, the Kyoto Protocol deals with the greenhouse gases sulfur
hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons
(PFCs). For a list of well-mixed greenhouse gases, see WGI AR5 Table
.SM.1.
Ground-level ozone
Atmospheric ozone formed naturally or from human-emitted precursors
near Earth’s surface, thus affecting human health, agriculture, and
ecosystems. Ozone is a greenhouse gas, but ground-level ozone, unlike
stratospheric ozone, also directly affects organisms at the surface.
Ground-level ozone is sometimes referred to as tropospheric ozone,
although much of the troposphere is well above the surface and thus
does not directly expose organisms at the surface. See also Ozone.
Groundwater recharge
The process by which external water is added to the zone of saturation
of an aquifer, either directly into a geologic formation that traps the
water or indirectly by way of another formation.
Hazard
The potential occurrence of a natural or human-induced physical event
or trend or physical impact that may cause loss of life, injury, or other
health impacts, as well as damage and loss to property, infrastructure,
livelihoods, service provision, ecosystems, and environmental resources.
In this report, the term hazard usually refers to climate-related physical
events or trends or their physical impacts.
Heat wave
A period of abnormally and uncomfortably hot weather.
Hotspot
A geographical area characterized by high vulnerability and exposure
to climate change.
Human security
A condition that is met when the vital core of human lives is protected,
and when people have the freedom and capacity to live with dignity.
In the context of climate change, the vital core of human lives includes
the universal and culturally specific, material and non-material elements
necessary for people to act on behalf of their interests and to live with
dignity.
Human system
Any system in which human organizations and institutions play a major
role. Often, but not always, the term is synonymous with society or


social system. Systems such as agricultural systems, political systems,
technological systems, and economic systems are all human systems in
the sense applied in this report.
Hydrological cycle
The cycle in which water evaporates from the oceans and the land
surface, is carried over the Earth in atmospheric circulation as water
vapor, condenses to form clouds, precipitates over ocean and land as
rain or snow, which on land can be intercepted by trees and vegetation,
provides runoff on the land surface, infiltrates into soils, recharges
groundwater, discharges into streams, and ultimately, flows out into
the oceans, from which it will eventually evaporate again. The various
systems involved in the hydrological cycle are usually referred to as
hydrological systems.
Hypoxic events
Events that lead to deficiencies of oxygen in water bodies. See also Dead
zones and Eutrophication.
Ice cap
A dome-shaped ice mass that is considerably smaller in extent than an
ice sheet.
Ice sheet
A mass of land ice of continental size that is sufficiently thick to cover
most of the underlying bed, so that its shape is mainly determined by
its dynamics (the flow of the ice as it deforms internally and/or slides
at its base). An ice sheet flows outward from a high central ice plateau
with a small average surface slope. The margins usually slope more
steeply, and most ice is discharged through fast flowing ice streams or
outlet glaciers, in some cases into the sea or into ice shelves floating
on the sea. There are only two ice sheets in the modern world, one on
Greenland and one on Antarctica. During glacial periods there were
others.
Ice shelf
A floating slab of ice of considerable thickness extending from the coast
(usually of great horizontal extent with a very gently sloping surface),
often filling embayments in the coastline of an ice sheet. Nearly all ice
shelves are in Antarctica, where most of the ice discharged into the
ocean flows via ice shelves.
(climate change) Impact assessment
The practice of identifying and evaluating, in monetary and/or nonmonetary
terms, the effects of climate change on natural and human
systems.
Impacts (Consequences, Outcomes)10
Effects on natural and human systems. In this report, the term impacts
is used primarily to refer to the effects on natural and human systems
of extreme weather and climate events and of climate change. Impacts
generally refer to effects on lives, livelihoods, health, ecosystems,
economies, societies, cultures, services, and infrastructure due to the
interaction of climate changes or hazardous climate events occurring
within a specific time period and the vulnerability of an exposed society
or system. Impacts are also referred to as consequences and outcomes.
The impacts of climate change on geophysical systems, including floods,
droughts, and sea level rise, are a subset of impacts called physical
impacts.
Income
The maximum amount that a household, or other unit, can consume
without reducing its real net worth. Total income is the broadest measure
of income and refers to regular receipts such as wages and salaries,
income from self-employment, interest and dividends from invested
funds, pensions or other benefits from social insurance, and other current
transfers receivable.11
Indian Ocean Dipole (IOD)
Large-scale mode of interannual variability of sea surface temperature
in the Indian Ocean. This pattern manifests through a zonal gradient of
tropical sea surface temperature, which in one extreme phase in boreal
autumn shows cooling off Sumatra and warming off Somalia in the
west, combined with anomalous easterlies along the equator.
Indigenous peoples
Indigenous peoples and nations are those that, having a historical
continuity with pre-invasion and pre-colonial societies that developed
on their territories, consider themselves distinct from other sectors of
the societies now prevailing on those territories, or parts of them. They
form at present principally non-dominant sectors of society and are
often determined to preserve, develop, and transmit to future generations
their ancestral territories, and their ethnic identity, as the basis of their
continued existence as peoples, in accordance with their own cultural
patterns, social institutions, and common law system.12
Industrial Revolution
A period of rapid industrial growth with far-reaching social and
economic consequences, beginning in Britain during the second half of
the 18th century and spreading to Europe and later to other countries
including the United States. The invention of the steam engine was an
important trigger of this development. The industrial revolution marks
the beginning of a strong increase in the use of fossil fuels and emission
of, in particular, fossil carbon dioxide. In this report the terms preindustrial
and industrial refer, somewhat arbitrarily, to the periods before and after
, respectively.
Industrialized/developed/developing countries
There are a diversity of approaches for categorizing countries on the
basis of their level of development, and for defining terms such as
industrialized, developed, or developing. Several categorizations are
used in this report. In the United Nations system, there is no established
convention for the designation of developed and developing countries
or areas. The United Nations Statistics Division specifies developed and
developing regions based on common practice. In addition, specific
countries are designated as least developed countries, landlocked
Reflecting progress in science, this glossary entry differs in breadth and focus from the entry used in the Fourth Assessment Report and other IPCC reports.
This glossary entry builds from the definition used in OECD (2003).
This glossary entry builds from the definitions used in Cobo (1987) and previous IPCC reports.

Annex II Glossary
II
developing countries, small island developing states, and transition
economies. Many countries appear in more than one of these categories.
The World Bank uses income as the main criterion for classifying
countries as low, lower middle, upper middle, and high income. The
UNDP aggregates indicators for life expectancy, educational attainment,
and income into a single composite human development index (HDI) to
classify countries as low, medium, high, or very high human development.
See Box 1-2.
Informal sector
Commercial enterprises (mostly small) that are not registered or that
otherwise fall outside official rules and regulations. Among the
businesses that make up the informal sector, there is great diversity in
the value of the goods or services produced, the numbers employed,
the extent of illegality, and the connection to the formal sector.
Many informal enterprises have some characteristics of formal-sector
enterprises, and some people are in informal employment in the formal
sector as they lack legal protection or employment benefits.
Informal settlement
A term given to settlements or residential areas that by at least one
criterion fall outside official rules and regulations. Most informal
settlements have poor housing (with widespread use of temporary
materials) and are developed on land that is occupied illegally with
high levels of overcrowding. In most such settlements, provision for
safe water, sanitation, drainage, paved roads, and basic services is
inadequate or lacking. The term slum is often used for informal
settlements, although it is misleading as many informal settlements
develop into good quality residential areas, especially where governments
support such development.
Institutions
Institutions are rules and norms held in common by social actors that
guide, constrain, and shape human interaction. Institutions can be
formal, such as laws and policies, or informal, such as norms and
conventions. Organizations—such as parliaments, regulatory agencies,
private firms, and community bodies—develop and act in response to
institutional frameworks and the incentives they frame. Institutions can
guide, constrain, and shape human interaction through direct control,
through incentives, and through processes of socialization.
Insurance/reinsurance
A family of financial instruments for sharing and transferring risk among
a pool of at-risk households, businesses, and/or governments. See also
Risk transfer.
Integrated assessment
A method of analysis that combines results and models from the physical,
biological, economic, and social sciences, and the interactions among
these components, in a consistent framework to evaluate the status
and the consequences of environmental change and the policy responses
to it.
Integrated Coastal Zone Management (ICZM)
An integrated approach for sustainably managing coastal areas, taking
into account all coastal habitats and uses.
Invasive species/Invasive Alien Species (IAS)
A species introduced outside its natural past or present distribution (i.e.,
an alien species) that becomes established in natural or semi-natural
ecosystems or habitat, is an agent of change, and threatens native
biological diversity (IUCN, 2000; CBD, 2002).
Key vulnerability, Key risk, Key impact
A vulnerability, risk, or impact relevant to the definition and elaboration
of “dangerous anthropogenic interference (DAI) with the climate
system,” in the terminology of United Nations Framework Convention
on Climate Change (UNFCCC) Article 2, meriting particular attention by
policy makers in that context.
Key risks are potentially severe adverse consequences for humans and
social-ecological systems resulting from the interaction of climaterelated
hazards with vulnerabilities of societies and systems exposed.
Risks are considered “key” due to high hazard or high vulnerability of
societies and systems exposed, or both.
Vulnerabilities are considered “key” if they have the potential to combine
with hazardous events or trends to result in key risks. Vulnerabilities
that have little influence on climate-related risk, for instance, due to
lack of exposure to hazards, would not be considered key.
Key impacts are severe consequences for humans and social-ecological
systems.
Land grabbing
Large acquisitions of land or water rights for industrial agriculture,
mitigation projects, or biofuels that have negative consequences on
local and marginalized communities.
Land surface air temperature
The surface air temperature as measured in well-ventilated screens over
land at 1.5 m above the ground.
Land use and Land use change
Land use refers to the total of arrangements, activities, and inputs
undertaken in a certain land cover type (a set of human actions). The
term land use is also used in the sense of the social and economic
purposes for which land is managed (e.g., grazing, timber extraction,
and conservation). Land use change refers to a change in the use or
management of land by humans, which may lead to a change in land
cover. Land cover and land use change may have an impact on the
surface albedo, evapotranspiration, sources and sinks of greenhouse
gases, or other properties of the climate system and may thus give rise
to radiative forcing and/or other impacts on climate, locally or globally.
See also the IPCC Special Report on Land Use, Land-Use Change, and
Forestry (IPCC, 2000).
La Niña
See El Niño-Southern Oscillation.
Last Glacial Maximum (LGM)
The period during the last ice age when the glaciers and ice sheets
reached their maximum extent, approximately 21 ka ago. This period


has been widely studied because the radiative forcings and boundary
conditions are relatively well known.
Likelihood
The chance of a specific outcome occurring, where this might be
estimated probabilistically. Likelihood is expressed in this report using
a standard terminology (Mastrandrea et al., 2010), defined in Box 1-1.
See also Confidence and Uncertainty.
Livelihood
The resources used and the activities undertaken in order to live.
Livelihoods are usually determined by the entitlements and assets to
which people have access. Such assets can be categorized as human,
social, natural, physical, or financial.
Low regrets policy
A policy that would generate net social and/or economic benefits under
current climate and a range of future climate change scenarios.
Maladaptive actions (Maladaptation)
Actions that may lead to increased risk of adverse climate-related
outcomes, increased vulnerability to climate change, or diminished
welfare, now or in the future.
Mean sea level
The surface level of the ocean at a particular point averaged over an
extended period of time such as a month or year. Mean sea level is often
used as a national datum to which heights on land are referred.
Meridional Overturning Circulation (MOC)
Meridional (north-south) overturning circulation in the ocean quantified
by zonal (east-west) sums of mass transports in depth or density layers.
In the North Atlantic, away from the subpolar regions, the MOC (which
is in principle an observable quantity) is often identified with the
thermohaline circulation (THC), which is a conceptual and incomplete
interpretation. It must be borne in mind that the MOC is also driven by
wind, and can also include shallower overturning cells such as occur in the
upper ocean in the tropics and subtropics, in which warm (light) waters
moving poleward are transformed to slightly denser waters and subducted
equatorward at deeper levels. See also Thermohaline circulation.
Microclimate
Local climate at or near the Earth’s surface. See also Climate.
Mitigation (of climate change)
A human intervention to reduce the sources or enhance the sinks of
greenhouse gases.
Mitigation (of disaster risk and disaster)
The lessening of the potential adverse impacts of physical hazards
(including those that are human-induced) through actions that reduce
hazard, exposure, and vulnerability.
Mode of climate variability
Underlying space-time structure with preferred spatial pattern and
temporal variation that helps account for the gross features in variance
and for teleconnections. A mode of variability is often considered to be
the product of a spatial climate pattern and an associated climate index
time series.
Monsoon
A monsoon is a tropical and subtropical seasonal reversal in both the
surface winds and associated precipitation, caused by differential
heating between a continental-scale land mass and the adjacent ocean.
Monsoon rains occur mainly over land in summer.
Non-climatic driver (Non-climate driver)
An agent or process outside the climate system that influences a human
or natural system.
Nonlinearity
A process is called nonlinear when there is no simple proportional
relation between cause and effect. The climate system contains many
such nonlinear processes, resulting in a system with potentially very
complex behavior. Such complexity may lead to abrupt climate change.
See also Predictability.
North Atlantic Oscillation (NAO)
The North Atlantic Oscillation consists of opposing variations of surface
pressure near Iceland and near the Azores. It therefore corresponds to
fluctuations in the strength of the main westerly winds across the Atlantic
into Europe, and thus to fluctuations in the embedded extratropical
cyclones with their associated frontal systems. See NAO Index in WGI
AR5 Box 2.5.
Ocean acidification
Ocean acidification refers to a reduction in the pH of the ocean over an
extended period, typically decades or longer, which is caused primarily
by uptake of carbon dioxide from the atmosphere, but can also be
caused by other chemical additions or subtractions from the ocean.
Anthropogenic ocean acidification refers to the component of pH
reduction that is caused by human activity (IPCC, 2011, p. 37).
Opportunity costs
The benefits of an activity forgone through the choice of another
activity.
Outcome vulnerability (End-point vulnerability)
Vulnerability as the end point of a sequence of analyses beginning with
projections of future emission trends, moving on to the development of
climate scenarios, and concluding with biophysical impact studies and
the identification of adaptive options. Any residual consequences that
remain after adaptation has taken place define the levels of vulnerability
(Kelly and Adger, 2000; O’Brien et al., 2007).
Oxygen Minimum Zone (OMZ)
The midwater layer (200 to 1000 m) in the open ocean in which oxygen
saturation is the lowest in the ocean. The degree of oxygen depletion
depends on the largely bacterial consumption of organic matter, and the
distribution of the OMZs is influenced by large-scale ocean circulation.
In coastal oceans, OMZs extend to the shelves and may also affect
benthic ecosystems.

Annex II Glossary
II
Ozone
Ozone, the triatomic form of oxygen (O3), is a gaseous atmospheric
constituent. In the troposphere, it is created both naturally and by
photochemical reactions involving gases resulting from human activities
(smog). Tropospheric ozone acts as a greenhouse gas. In the stratosphere,
it is created by the interaction between solar ultraviolet radiation and
molecular oxygen (O2). Stratospheric ozone plays a dominant role in the
stratospheric radiative balance. Its concentration is highest in the ozone
layer.
Pacific Decadal Oscillation (PDO)
The pattern and time series of the first empirical orthogonal function
of sea surface temperature over the North Pacific north of 20°N. The
PDO broadened to cover the whole Pacific Basin is known as the Interdecadal
Pacific Oscillation (IPO). The PDO and IPO exhibit similar
temporal evolution.
Parameterization
In climate models, this term refers to the technique of representing
processes that cannot be explicitly resolved at the spatial or temporal
resolution of the model (sub-grid scale processes) by relationships
between model-resolved larger-scale variables and the area- or timeaveraged
effect of such sub-grid scale processes.
Particulates
Very small solid particles emitted during the combustion of fossil and
biomass fuels. Particulates may consist of a wide variety of substances.
Of greatest concern for health are particulates of diameter less than or
equal to 10 nm, usually designated as PM10.
Pastoralism
A livelihood strategy based on moving livestock to seasonal pastures
primarily in order to convert grasses, forbs, tree leaves, or crop residues
into human food. The search for feed is however not the only reason
for mobility; people and livestock may move to avoid various natural
and/or social hazards, to avoid competition with others, or to seek more
favorable conditions. Pastoralism can also be thought of as a strategy
that is shaped by both social and ecological factors concerning
uncertainty and variability of precipitation, and low and unpredictable
productivity of terrestrial ecosystems.
Path dependence
The generic situation where decisions, events, or outcomes at one point
in time constrain adaptation, mitigation, or other actions or options at
a later point in time.
Permafrost
Ground (soil or rock and included ice and organic material) that remains
at or below 0°C for at least 2 consecutive years.
Persistent Organic Pollutants (POPs)
Toxic organic chemical substances that persist in the environment for
long periods of time, are transported and deposited in locations distant
from their sources of release, bioaccumulate, and can have adverse
effects on human health and ecosystems.13
Phenology
The relationship between biological phenomena that recur periodically
(e.g., development stages, migration) and climate and seasonal changes.
Photochemical smog
A mix of oxidizing air pollutants produced by the reaction of sunlight
with primary air pollutants, especially hydrocarbons.
Poverty
Poverty is a complex concept with several definitions stemming from
different schools of thought. It can refer to material circumstances (such
as need, pattern of deprivation, or limited resources), economic conditions
(such as standard of living, inequality, or economic position), and/or
social relationships (such as social class, dependency, exclusion, lack of
basic security, or lack of entitlement).
Poverty trap
Poverty trap is understood differently across disciplines. In the social
sciences, the concept, primarily employed at the individual, household,
or community level, describes a situation in which escaping poverty
becomes impossible due to unproductive or inflexible resources. A
poverty trap can also be seen as a critical minimum asset threshold,
below which families are unable to successfully educate their children,
build up their productive assets, and get out of poverty. Extreme poverty
is itself a poverty trap, since poor persons lack the means to participate
meaningfully in society. In economics, the term poverty trap is often
used at national scales, referring to a self-perpetuating condition
where an economy, caught in a vicious cycle, suffers from persistent
underdevelopment (Matsuyama, 2008). Many proposed models of
poverty traps are found in the literature.
Predictability
The extent to which future states of a system may be predicted based on
knowledge of current and past states of the system. Because knowledge
of the climate system’s past and current states is generally imperfect,
as are the models that utilize this knowledge to produce a climate
prediction, and because the climate system is inherently nonlinear and
chaotic, predictability of the climate system is inherently limited. Even
with arbitrarily accurate models and observations, there may still be
limits to the predictability of such a nonlinear system (AMS, 2000).
Preindustrial
See Industrial Revolution.
Probability Density Function (PDF)
A probability density function is a function that indicates the relative
chances of occurrence of different outcomes of a variable. The function
integrates to unity over the domain for which it is defined and has the
property that the integral over a sub-domain equals the probability that
the outcome of the variable lies within that sub-domain. For example,
the probability that a temperature anomaly defined in a particular way
is greater than zero is obtained from its PDF by integrating the PDF over
all possible temperature anomalies greater than zero. Probability density
functions that describe two or more variables simultaneously are
similarly defined.
This glossary entry builds from the definition in the Stockholm Convention on Persistent Organic Pollutants (Secretariat of the Stockholm Convention, 2001).


Projection
A projection is a potential future evolution of a quantity or set of
quantities, often computed with the aid of a model. Unlike predictions,
projections are conditional on assumptions concerning, for example,
future socioeconomic and technological developments that may or may
not be realized. See also Climate prediction and Climate projection.
Proxy
A proxy climate indicator is a record that is interpreted, using physical
and biophysical principles, to represent some combination of climaterelated
variations back in time. Climate-related data derived in this way
are referred to as proxy data. Examples of proxies include pollen analysis,
tree ring records, speleothems, characteristics of corals, and various data
derived from marine sediments and ice cores. Proxy data can be calibrated
to provide quantitative climate information.
Public good
A good that is both non-excludable and non-rivalrous in that individuals
cannot be effectively excluded from use and where use by one individual
does not reduce availability to others.
Radiative forcing
Radiative forcing is the change in the net, downward minus upward,
radiative flux (expressed in W m–2) at the tropopause or top of atmosphere
due to a change in an external driver of climate change, such as a
change in the concentration of carbon dioxide or the output of the Sun.
Sometimes internal drivers are still treated as forcings even though they
result from the alteration in climate, for example aerosol or greenhouse
gas changes in paleoclimates. The traditional radiative forcing is computed
with all tropospheric properties held fixed at their unperturbed values,
and after allowing for stratospheric temperatures, if perturbed, to
readjust to radiative-dynamical equilibrium. Radiative forcing is called
instantaneous if no change in stratospheric temperature is accounted
for. The radiative forcing once rapid adjustments are accounted for is
termed the effective radiative forcing. For the purposes of this report,
radiative forcing is further defined as the change relative to the year
and, unless otherwise noted, refers to a global and annual average
value. Radiative forcing is not to be confused with cloud radiative forcing,
which describes an unrelated measure of the impact of clouds on the
radiative flux at the top of the atmosphere.
Reanalysis
Reanalyses are estimates of historical atmospheric temperature and
wind or oceanographic temperature and current, and other quantities,
created by processing past meteorological or oceanographic data using
fixed state-of-the-art weather forecasting or ocean circulation models
with data assimilation techniques. Using fixed data assimilation avoids
effects from the changing analysis system that occur in operational
analyses. Although continuity is improved, global reanalyses still suffer
from changing coverage and biases in the observing systems.
Reasons for concern
Elements of a classification framework, first developed in the IPCC Third
Assessment Report, which aims to facilitate judgments about what level
of climate change may be “dangerous” (in the language of Article 2 of
the UNFCCC) by aggregating impacts, risks, and vulnerabilities.
Reference scenario
See Baseline/reference.
Reflexivity
A system attribute where cause and effect form a feedback loop, in
which the effect changes the system itself. Self-adapting systems such
as societies are inherently reflexive, as are planned changes in complex
systems. Reflexive decision making in a social system has the potential
to change the underpinning values that led to those decisions. Reflexivity
is also an important aspect of adaptive management.
Reforestation
Planting of forests on lands that have previously contained forests but
that have been converted to some other use. For a discussion of the
term forest and related terms such as afforestation, reforestation, and
deforestation, see the IPCC Special Report on Land Use, Land-Use
Change, and Forestry (IPCC, 2000). See also the Report on Definitions
and Methodological Options to Inventory Emissions from Direct Humaninduced
Degradation of Forests and Devegetation of Other Vegetation
Types (IPCC, 2003).
Relative sea level
Sea level measured by a tide gauge with respect to the land upon which
it is situated. See also Mean sea level and Sea level change.
Representative Concentration Pathways (RCPs)
Scenarios that include time series of emissions and concentrations of
the full suite of greenhouse gases and aerosols and chemically active
gases, as well as land use/land cover (Moss et al., 2008). The word
representative signifies that each RCP provides only one of many
possible scenarios that would lead to the specific radiative forcing
characteristics. The term pathway emphasizes that not only the longterm
concentration levels are of interest, but also the trajectory taken
over time to reach that outcome (Moss et al., 2010).
RCPs usually refer to the portion of the concentration pathway extending
up to 2100, for which Integrated Assessment Models produced
corresponding emission scenarios. Extended Concentration Pathways
(ECPs) describe extensions of the RCPs from 2100 to 2500 that were
calculated using simple rules generated by stakeholder consultations,
and do not represent fully consistent scenarios.
Four RCPs produced from Integrated Assessment Models were selected
from the published literature and are used in the present IPCC Assessment
as a basis for the climate predictions and projections in WGI AR5 Chapters
to 14:
RCP2.6 One pathway where radiative forcing peaks at approximately
W m–2 before 2100 and then declines (the corresponding ECP
assuming constant emissions after 2100).
RCP4.5 and RCP6.0 Two intermediate stabilization pathways in
which radiative forcing is stabilized at approximately 4.5 W m–2 and
.0 W m–2 after 2100 (the corresponding ECPs assuming constant
concentrations after 2150).

Annex II Glossary
II
RCP8.5 One high pathway for which radiative forcing reaches
greater than 8.5 W m–2 by 2100 and continues to rise for some
amount of time (the corresponding ECP assuming constant emissions
after 2100 and constant concentrations after 2250).
For further description of future scenarios, see WGI AR5 Box 1.1.
Resilience
The capacity of social, economic, and environmental systems to cope with
a hazardous event or trend or disturbance, responding or reorganizing
in ways that maintain their essential function, identity, and structure,
while also maintaining the capacity for adaptation, learning, and
transformation.14
Return period
An estimate of the average time interval between occurrences of an
event (e.g., flood or extreme rainfall) of (or below/above) a defined size
or intensity. See also Return value.
Return value
The highest (or, alternatively, lowest) value of a given variable, on
average occurring once in a given period of time (e.g., in 10 years). See
also Return period.
Risk
The potential for consequences where something of value is at stake and
where the outcome is uncertain, recognizing the diversity of values.15
Risk is often represented as probability of occurrence of hazardous
events or trends multiplied by the impacts if these events or trends
occur. Risk results from the interaction of vulnerability, exposure, and
hazard. In this report, the term risk is used primarily to refer to the risks
of climate-change impacts.
Risk assessment
The qualitative and/or quantitative scientific estimation of risks.
Risk management
Plans, actions, or policies to reduce the likelihood and/or consequences
of risks or to respond to consequences.
Risk perception
The subjective judgment that people make about the characteristics and
severity of a risk.
Risk transfer
The practice of formally or informally shifting the risk of financial
consequences for particular negative events from one party to
another.
Runoff
That part of precipitation that does not evaporate and is not transpired,
but flows through the ground or over the ground surface and returns
to bodies of water. See also Hydrological cycle.
Salt-water intrusion/encroachment
Displacement of fresh surface water or groundwater by the advance of
salt water due to its greater density. This usually occurs in coastal and
estuarine areas due to decreasing land-based influence (e.g., from
reduced runoff or groundwater recharge, or from excessive water
withdrawals from aquifers) or increasing marine influence (e.g., relative
sea level rise).
Scenario
A plausible description of how the future may develop based on a
coherent and internally consistent set of assumptions about key driving
forces (e.g., rate of technological change, prices) and relationships. Note
that scenarios are neither predictions nor forecasts, but are useful to
provide a view of the implications of developments and actions. See
also Climate scenario, Emission scenario, Representative Concentration
Pathways, and SRES scenarios.
Sea level change
Sea level can change, both globally and locally due to (1) changes in
the shape of the ocean basins, (2) a change in ocean volume as a result
of a change in the mass of water in the ocean, and (3) changes in ocean
volume as a result of changes in ocean water density. Global mean sea
level change resulting from change in the mass of the ocean is called
barystatic. The amount of barystatic sea level change due to the addition
or removal of a mass of water is called its sea level equivalent (SLE).
Sea level changes, both globally and locally, resulting from changes in
water density are called steric. Density changes induced by temperature
changes only are called thermosteric, while density changes induced by
salinity changes are called halosteric. Barystatic and steric sea level
changes do not include the effect of changes in the shape of ocean
basins induced by the change in the ocean mass and its distribution.
See also Relative sea level and Thermal expansion.
Sea Surface Temperature (SST)
The sea surface temperature is the subsurface bulk temperature in the
top few meters of the ocean, measured by ships, buoys, and drifters.
From ships, measurements of water samples in buckets were mostly
switched in the 1940s to samples from engine intake water. Satellite
measurements of skin temperature (uppermost layer; a fraction of a
millimeter thick) in the infrared or the top centimeter or so in the
microwave are also used, but must be adjusted to be compatible with
the bulk temperature.
Semi-arid zone
Areas where vegetation growth is constrained by limited water availability,
often with short growing seasons and high interannual variation in
primary production. Annual precipitation ranges from 300 to 800 mm,
depending on the occurrence of summer and winter rains.
Sensitivity
The degree to which a system or species is affected, either adversely or
beneficially, by climate variability or change. The effect may be direct
(e.g., a change in crop yield in response to a change in the mean, range,
This definition builds from the definition used in Arctic Council (2013).
This definition builds from the definitions used in Rosa (1998) and Rosa (2003).


or variability of temperature) or indirect (e.g., damages caused by an
increase in the frequency of coastal flooding due to sea level rise).
Significant wave height
The average trough-to-crest height of the highest one-third of the wave
heights (sea and swell) occurring in a particular time period.
Sink
Any process, activity, or mechanism that removes a greenhouse gas,
an aerosol, or a precursor of a greenhouse gas or aerosol from the
atmosphere.
Social Cost of Carbon (SCC)
The net present value of climate damages (with harmful damages
expressed as a positive number) from one more tonne of carbon in the
form of CO2, conditional on a global emissions trajectory over time.
Social protection
In the context of development aid and climate policy, social protection
usually describes public and private initiatives that provide income or
consumption transfers to the poor, protect the vulnerable against livelihood
risks, and enhance the social status and rights of the marginalized, with
the overall objective of reducing the economic and social vulnerability of
poor, vulnerable, and marginalized groups (Devereux and Sabates-Wheeler,
). In other contexts, social protection may be used synonymously
with social policy and can be described as all public and private initiatives
that provide access to services, such as health, education, or housing, or
income and consumption transfers to people. Social protection policies
protect the poor and vulnerable against livelihood risks and enhance
the social status and rights of the marginalized, as well as prevent
vulnerable people from falling into poverty.
Socioeconomic scenario
A scenario that describes a possible future in terms of population,
gross domestic product, and other socioeconomic factors relevant to
understanding the implications of climate change.
Southern Annular Mode (SAM)
The leading mode of variability of Southern Hemisphere geopotential
height, which is associated with shifts in the latitude of the midlatitude
jet. See SAM Index in WGI AR5 Box 2.5.
Species distribution modeling
Simulation of ecological effects of climate change. Species distribution
modeling uses statistically or theoretically derived response surfaces to
relate observations of species occurrence or known tolerance limits to
environmental predictor variables, thereby predicting a species’ range
as the manifestation of habitat characteristics that limit or support its
presence at a particular location. Species distribution models are also
referred to as environmental niche models. Bioclimate envelope models
can be considered as a subset of species distribution models that predict
species occurrence or habitat suitability based on climatic variables only.
SRES scenarios
SRES scenarios are emission scenarios developed by Nakićenović and
Swart (2000) and used, among others, as a basis for some of the climate
projections shown in Chapters 9 to 11 of IPCC (2001) and Chapters 10
and 11 of IPCC (2007). The following terms are relevant for a better
understanding of the structure and use of the set of SRES scenarios:
Scenario family Scenarios that have a similar demographic, societal,
economic, and technical change storyline. Four scenario families
comprise the SRES scenario set: A1, A2, B1, and B2.
Illustrative scenario A scenario that is illustrative for each of the
six scenario groups reflected in the Summary for Policymakers of
Nakićenović and Swart (2000). They include four revised marker
scenarios for the scenario groups A1B, A2, B1, and B2, and two
additional scenarios for the A1FI and A1T groups. All scenario
groups are equally sound.
Marker scenario A scenario that was originally posted in draft
form on the SRES web site to represent a given scenario family. The
choice of markers was based on which of the initial quantifications
best reflected the storyline, and the features of specific models.
Markers are no more likely than other scenarios, but are considered
by the SRES writing team as illustrative of a particular storyline.
They are included in revised form in Nakićenović and Swart (2000).
These scenarios received the closest scrutiny of the entire writing
team and via the SRES open process. Scenarios were also selected
to illustrate the other two scenario groups.
StorylineA narrative description of a scenario (or family of scenarios),
highlighting the main scenario characteristics, relationships between
key driving forces, and the dynamics of their evolution.
Storm surge
The temporary increase, at a particular locality, in the height of the sea
due to extreme meteorological conditions (low atmospheric pressure
and/or strong winds). The storm surge is defined as being the excess
above the level expected from the tidal variation alone at that time and
place.
Storm tracks
Originally, a term referring to the tracks of individual cyclonic weather
systems, but now often generalized to refer to the main regions where
the tracks of extratropical disturbances occur as sequences of low
(cyclonic) and high (anticyclonic) pressure systems.
Stratosphere
The highly stratified region of the atmosphere above the troposphere
extending from about 10 km (ranging from 9 km at high latitudes to
km in the tropics on average) to about 50 km altitude.
Stressors
Events and trends, often not climate-related, that have an important
effect on the system exposed and can increase vulnerability to climaterelated
risk.
Subsistence agriculture
Farming and associated activities that together form a livelihood
strategy in which most output is consumed directly but some may be
sold at market. Subsistence agriculture can be one of several livelihood
activities.

Annex II Glossary
II
Surface temperature
See Global mean surface temperature, Land surface air temperature,
and Sea Surface Temperature.
Sustainability
A dynamic process that guarantees the persistence of natural and
human systems in an equitable manner.
Sustainable development
Development that meets the needs of the present without compromising
the ability of future generations to meet their own needs (WCED, 1987).
Thermal expansion
In connection with sea level, this refers to the increase in volume (and
decrease in density) that results from warming water. A warming of the
ocean leads to an expansion of the ocean volume and hence an increase
in sea level. See also Sea level change.
Thermocline
The layer of maximum vertical temperature gradient in the ocean, lying
between the surface ocean and the abyssal ocean. In subtropical regions,
its source waters are typically surface waters at higher latitudes that have
subducted and moved equatorward. At high latitudes, it is sometimes
absent, replaced by a halocline, which is a layer of maximum vertical
salinity gradient.
Thermohaline circulation (THC)
Large-scale circulation in the ocean that transforms low-density upper
ocean waters to higher-density intermediate and deep waters and
returns those waters back to the upper ocean. The circulation is
asymmetric, with conversion to dense waters in restricted regions at
high latitudes and the return to the surface involving slow upwelling
and diffusive processes over much larger geographic regions. The
THC is driven by high densities at or near the surface, caused by cold
temperatures and/or high salinities, but despite its suggestive though
common name, is also driven by mechanical forces such as wind and
tides. Frequently, the name THC has been used synonymously with
Meridional Overturning Circulation. See also Meridional Overturning
Circulation.
Tipping point
A level of change in system properties beyond which a system reorganizes,
often abruptly, and does not return to the initial state even if the drivers
of the change are abated.16
Traditional knowledge
The knowledge, innovations, and practices of both indigenous and local
communities around the world that are deeply grounded in history and
experience. Traditional knowledge is dynamic and adapts to cultural and
environmental change, and also incorporates other forms of knowledge
and viewpoints. Traditional knowledge is generally transmitted orally
from generation to generation. It is often used as a synonym for
indigenous knowledge, local knowledge, or traditional ecological
knowledge.
Transformation
A change in the fundamental attributes of natural and human systems.
Tree line
The upper limit of tree growth in mountains or at high latitudes. It is
more elevated or more poleward than the forest line.
Tropical cyclone
A strong, cyclonic-scale disturbance that originates over tropical oceans.
Distinguished from weaker systems (often named tropical disturbances
or depressions) by exceeding a threshold wind speed. A tropical storm is
a tropical cyclone with 1-minute average surface winds between 18 and
m s–1. Beyond 32 m s–1, a tropical cyclone is called a hurricane,
typhoon, or cyclone, depending on geographic location.
Troposphere
The lowest part of the atmosphere, from the surface to about 10 km in
altitude at mid-latitudes (ranging from 9 km at high latitudes to 16 km
in the tropics on average), where clouds and weather phenomena occur.
In the troposphere, temperatures generally decrease with height. See
also Stratosphere.
Tsunami
A wave, or train of waves, produced by a disturbance such as a submarine
earthquake displacing the sea floor, a landslide, a volcanic eruption, or
an asteroid impact.
Tundra
A treeless biome characteristic of polar and alpine regions.
Uncertainty
A state of incomplete knowledge that can result from a lack of information
or from disagreement about what is known or even knowable. It may
have many types of sources, from imprecision in the data to ambiguously
defined concepts or terminology, or uncertain projections of human
behavior. Uncertainty can therefore be represented by quantitative
measures (e.g., a probability density function) or by qualitative statements
(e.g., reflecting the judgment of a team of experts) (see Moss and
Schneider, 2000; Manning et al., 2004; Mastrandrea et al., 2010). See
also Confidence and Likelihood.
United Nations Framework Convention
on Climate Change (UNFCCC)
The Convention was adopted on 9 May 1992 in New York and signed
at the 1992 Earth Summit in Rio de Janeiro by more than 150 countries
and the European Community. Its ultimate objective is the “stabilization
of greenhouse gas concentrations in the atmosphere at a level that
would prevent dangerous anthropogenic interference with the climate
system.” It contains commitments for all Parties. Under the Convention,
Parties included in Annex I (all OECD countries and countries with
economies in transition) aim to return greenhouse gas emissions not
controlled by the Montreal Protocol to 1990 levels by the year 2000.
The convention entered in force in March 1994. In 1997, the UNFCCC
adopted the Kyoto Protocol.
The glossary for the Working Group I contribution to the Fifth Assessment Report defines tipping point in the context of climate: “In climate, a hypothesized critical threshold
when global or regional climate changes from one stable state to another stable state. The tipping point event may be irreversible.”


Uptake
The addition of a substance of concern to a reservoir. The uptake of
carbon containing substances, in particular carbon dioxide, is often
called (carbon) sequestration.
Upwelling region
A region of an ocean where cold, typically nutrient-rich waters well up
from the deep ocean.
Urban heat island
The relative warmth of a city compared with surrounding rural areas,
associated with changes in runoff, effects on heat retention, and
changes in surface albedo.
Volatile Organic Compounds (VOCs)
Important class of organic chemical air pollutants that are volatile
at ambient air conditions. Other terms used to represent VOCs are
hydrocarbons (HCs), reactive organic gases (ROGs), and non-methane
volatile organic compounds (NMVOCs). NMVOCs are major contributors
(together with NOX and CO) to the formation of photochemical oxidants
such as ozone.
Vulnerability17
The propensity or predisposition to be adversely affected. Vulnerability
encompasses a variety of concepts and elements including sensitivity
or susceptibility to harm and lack of capacity to cope and adapt. See
also Contextual vulnerability and Outcome vulnerability.
Vulnerability index
A metric characterizing the vulnerability of a system. A climate
vulnerability index is typically derived by combining, with or without
weighting, several indicators assumed to represent vulnerability.
Water cycle
See Hydrological cycle.
Water-use efficiency
Carbon gain by photosynthesis per unit of water lost by evapotranspiration.
It can be expressed on a short-term basis as the ratio of photosynthetic
carbon gain per unit transpirational water loss, or on a seasonal basis
as the ratio of net primary production or agricultural yield to the amount
of water used.

Annex II Glossary Abrupt change/abrupt climate change Abrupt change refers to a change that is substantially faster than the rate of change in the recent history of the affected components of a system. Abrupt climate change refers to a large-scale change in the climate system that takes place over a few decades or less, persists (or is anticipated to persist) for at least a few decades and causes substantial disruptions in human and natural systems. {WGI, II, III} Adaptation The process of adjustment to actual or expected climate and its effects. In human systems, adaptation seeks to moderate or avoid harm or exploit beneficial opportunities. In some natural systems, human intervention may facilitate adjustment to expected climate and its effects1. {WGII, III} Adaptation deficit The gap between the current state of a system and a state that minimizes adverse impacts from existing climate conditions and variability. {WGII} Adaptation limit The point at which an actor’s objectives (or system needs) cannot be secured from intolerable risks through adaptive actions. {WGII} Hard adaptation limit No adaptive actions are possible to avoid intolerable risks. Soft adaptation limit Options are currently not available to avoid intolerable risks through adaptive action. Adaptive capacity The ability of systems, institutions, humans and other organisms to adjust to potential damage, to take advantage of opportunities, or to respond to consequences2. {WGII, III} Adverse side effects The negative effects that a policy or measure aimed at one objective might have on other objectives, irrespective of the net effect on overall social welfare. Adverse side effects are often subject to uncertainty and depend on local circumstances and implementation practices, among other factors. See also Co-benefits and Risk. {WGIII} Afforestation Planting of new forests on lands that historically have not contained forests. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000b). See also information provided by the United Nations Framework Convention on Climate Change (UNFCCC, 2013) and the report on Definitions and Methodological Options to Inventory Emissions from Direct Human-induced Degradation of Forests and Devegetation of Other Vegetation Types (IPCC, 2003). {WGI, III} Agriculture, Forestry and Other Land Use (AFOLU and FOLU/LULUCF) AFOLU plays a central role for food security and sustainable development. The main mitigation options within AFOLU involve one or more of three strategies: prevention of emissions to the atmosphere by conserving existing carbon pools in soils or vegetation or by reducing emissions of methane and nitrous oxide; sequestration—increasing the size of existing carbon pools and thereby extracting carbon dioxide (CO2) from the atmosphere; and substitution—substituting biological products for fossil fuels or energy-intensive products, thereby reducing CO2 emissions. Demand-side measures (e.g., reducing losses and wastes of food, changes in human diet, or changes in wood consumption) may also play a role. FOLU (Forestry and Other Land Use)—also referred to as LULUCF (Land Use, Land-Use Change, and Forestry)—is the subset of AFOLU emissions and removals of greenhouse gases (GHGs) resulting from direct human-induced land use, land-use change, and forestry activities excluding agricultural emissions. {WGIII} Albedo The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. Snow-covered surfaces have a high albedo, the albedo of soils ranges from high to low and vegetation-covered surfaces and oceans have a low albedo. The Earth’s planetary albedo varies mainly through varying cloudiness, snow, ice, leaf area and land cover changes. {WGI, III} Altimetry A technique for measuring the height of the Earth’s surface with respect to the geocentre of the Earth within a defined terrestrial reference frame (geocentric sea level). {WGI} Ancillary benefits See Co-benefits. {WGII, III} Attribution See Detection and attribution. {WGI, II}. Baseline/reference The baseline (or reference) is the state against which change is measured. A baseline period is the period relative to which anomalies are computed. In the context of transformation pathways, the term baseline This glossary defines some specific terms as the Core Writing Team of the Synthesis Report intends them to be interpreted in the context of this report. Red, italicized words indicate that the term is defined in the glossary. The references to Working Groups (WG) I, II and III in italics at the end of each term in this glossary refer to the AR5 WG glossaries and should be read as: WGI (IPCC, 2013a), WGII (IPCC, 2014a), and WGIII (IPCC, 2014b). Reflecting progress in science, this glossary entry differs in breadth and focus from the entry used in the Fourth Assessment Report and other IPCC reports. This glossary entry builds from definitions used in previous IPCC reports and the Millennium Ecosystem Assessment (MEA, 2005).


scenarios refers to scenarios that are based on the assumption that no mitigation policies or measures will be implemented beyond those that are already in force and/or are legislated or planned to be adopted. Baseline scenarios are not intended to be predictions of the future, but rather counterfactual constructions that can serve to highlight the level of emissions that would occur without further policy effort. Typically, baseline scenarios are then compared to mitigation scenarios that are constructed to meet different goals for greenhouse gas (GHG) emissions, atmospheric concentrations or temperature change. The term baseline scenario is used interchangeably with reference scenario and no policy scenario. In much of the literature the term is also synonymous with the term business-as-usual (BAU) scenario, although the term BAU has fallen out of favour because the idea of business as usual in century-long socio-economic projections is hard to fathom. See also Emission scenario, Representative Concentration Pathways (RCPs) and SRES scenarios. {WGI, II, III} Biodiversity The variability among living organisms from terrestrial, marine and other ecosystems. Biodiversity includes variability at the genetic, species and ecosystem levels3. {WGII, III} Bioenergy and Carbon Dioxide Capture and Storage (BECCS) The application of Carbon Dioxide Capture and Storage (CCS) technology to bioenergy conversion processes. Depending on the total lifecycle emissions, including total marginal consequential effects (from indirect land-use change (iLUC) and other processes), BECCS has the potential for net carbon dioxide (CO2) removal from the atmosphere. See also Sequestration. {WGIII} Burden sharing/effort sharing In the context of mitigation, burden sharing refers to sharing the effort of reducing the sources or enhancing the sinks of greenhouse gases (GHGs) from historical or projected levels, usually allocated by some criteria, as well as sharing the cost burden across countries. {WGIII} Cancún Agreements A set of decisions adopted at the 16th Session of the Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change (UNFCCC), including the following, among others: the newly established Green Climate Fund (GCF), a newly established technol- ogy mechanism, a process for advancing discussions on adaptation, a formal process for reporting mitigation commitments, a goal of limiting global mean surface temperature increase to 2°C and an agreement on MRV—Measurement, Reporting and Verification for those countries that receive international support for their mitigation efforts. {WGIII} Cancún Pledges During 2010, many countries submitted their existing plans for controlling greenhouse gas (GHG) emissions to the Climate Change Secretariat and these proposals have now been formally acknowledged under the United Nations Framework Convention on Climate Change (UNFCCC). Developed countries presented their plans in the shape of economy-wide targets to reduce emissions, mainly up to 2020, while developing countries proposed ways to limit their growth of emissions in the shape of plans of action. {WGIII} Carbon cycle The term used to describe the flow of carbon (in various forms, e.g., as carbon dioxide (CO2)) through the atmosphere, ocean, terrestrial and marine biosphere and lithosphere. In this report, the reference unit for the global carbon cycle is GtCO2 or GtC (Gigatonne of carbon = 1 GtC = 1015 grams of carbon. This corresponds to 3.667 GtCO2). {WGI, II, III} Carbon Dioxide Capture and Storage (CCS) A process in which a relatively pure stream of carbon dioxide (CO2) from industrial and energy-related sources is separated (captured), conditioned, compressed and transported to a storage location for long-term isolation from the atmosphere. See also Bioenergy and Carbon Dioxide Capture and Storage (BECCS) and Sequestration. {WGIII} Carbon Dioxide Removal (CDR) Carbon Dioxide Removal methods refer to a set of techniques that aim to remove CO2 directly from the atmosphere by either (1) increasing natural sinks for carbon or (2) using chemical engineering to remove the CO2, with the intent of reducing the atmospheric CO2 concentration. CDR methods involve the ocean, land and technical systems, including such methods as iron fertilization, large-scale afforestation and direct capture of CO2 from the atmosphere using engineered chemical means. Some CDR methods fall under the category of geoengineering, though this may not be the case for others, with the distinction being based on the magnitude, scale and impact of the particular CDR activities. The boundary between CDR and mitigation is not clear and there could be some overlap between the two given current definitions (IPCC, 2012b, p. 2). See also Solar Radiation Management (SRM). {WGI, III} Carbon intensity The amount of emissions of carbon dioxide (CO2) released per unit of another variable such as Gross Domestic Product (GDP), output energy use or transport. {WGIII} Carbon price The price for avoided or released carbon dioxide (CO2) or CO2-equivalent emissions. This may refer to the rate of a carbon tax, or the price of emission permits. In many models that are used to assess the economic costs of mitigation, carbon prices are used as a proxy to represent the level of effort in mitigation policies. {WGIII} Carbon tax A levy on the carbon content of fossil fuels. Because virtually all of the carbon in fossil fuels is ultimately emitted as carbon dioxide (CO2), a carbon tax is equivalent to an emission tax on CO2 emissions. {WGIII} Climate Climate in a narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these This glossary entry builds from definitions used in the Global Biodiversity Assessment (Heywood, 1995) and the Millennium Ecosystem Assessment (MEA, 2005).


variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. {WGI, II, III} Climate change Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use. Note that the Framework Convention on Climate Change (UNFCCC), in its Article 1, defines climate change as: ‘a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods’. The UNFCCC thus makes a distinction between climate change attributable to human activities altering the atmospheric composition and climate variability attributable to natural causes. See also Detection and Attribution. {WGI, II, III} Climate extreme (extreme weather or climate event) See Extreme weather event. {WGI, II} Climate feedback An interaction in which a perturbation in one climate quantity causes a change in a second and the change in the second quantity ultimately leads to an additional change in the first. A negative feedback is one in which the initial perturbation is weakened by the changes it causes; a positive feedback is one in which the initial perturbation is enhanced. In the Fifth Assessment Report, a somewhat narrower definition is often used in which the climate quantity that is perturbed is the global mean surface temperature, which in turn causes changes in the global radiation budget. In either case, the initial perturbation can either be externally forced or arise as part of internal variability. {WGI, II, III} Climate finance There is no agreed definition of climate finance. The term climate finance is applied both to the financial resources devoted to addressing climate change globally and to financial flows to developing countries to assist them in addressing climate change. The literature includes several concepts in these categories, among which the most commonly used include: {WGIII} Incremental costs The cost of capital of the incremental investment and the change of operating and maintenance costs for a mitigation or adaptation project in comparison to a reference project. It can be calculated as the difference of the net present values of the two projects. Incremental investment The extra capital required for the initial investment for a mitigation or adaptation project in comparison to a reference project. Total climate finance All financial flows whose expected effect is to reduce net greenhouse gas (GHG) emissions and/or to enhance resilience to the impacts of climate variability and the projected climate change. This covers private and public funds, domestic and international flows and expenditures for mitigation and adaptation to current climate variability as well as future climate change. Total climate finance flowing to developing countries The amount of the total climate finance invested in developing countries that comes from developed countries. This covers private and public funds. Private climate finance flowing to developing countries Finance and investment by private actors in/from developed countries for mitigation and adaptation activities in developing countries. Public climate finance flowing to developing countries Finance provided by developed countries’ governments and bilateral institutions as well as by multilateral institutions for mitigation and adaptation activities in developing countries. Most of the funds provided are concessional loans and grants. Climate model (spectrum or hierarchy) A numerical representation of the climate system based on the physical, chemical and biological properties of its components, their interactions and feedback processes and accounting for some of its known properties. The climate system can be represented by models of varying complexity; that is, for any one component or combination of components a spectrum or hierarchy of models can be identified, differing in such aspects as the number of spatial dimensions, the extent to which physical, chemical or biological processes are explicitly represented, or the level at which empirical parametrizations are involved. Coupled Atmosphere–Ocean General Circulation Models (AOGCMs) provide a representation of the climate system that is near or at the most comprehensive end of the spectrum currently available. There is an evolution towards more complex models with interactive chemistry and biology. Climate models are applied as a research tool to study and simulate the climate and for operational purposes, including monthly, seasonal and interannual climate predictions. {WGI, II, III} Climate projection A climate projection is the simulated response of the climate system to a scenario of future emission or concentration of greenhouse gases (GHGs) and aerosols, generally derived using climate models. Climate projections are distinguished from climate predictions by their dependence on the emission/concentration/radiative forcing scenario used, which is in turn based on assumptions concerning, for example, future socio-economic and technological developments that may or may not be realized. {WGI, II, III} Climate-resilient pathways Iterative processes for managing change within complex systems in order to reduce disruptions and enhance opportunities associated with climate change. {WGII} Climate response See Climate sensitivity. {WGI} Climate sensitivity In IPCC reports, equilibrium climate sensitivity (units: °C) refers to the equilibrium (steady state) change in the annual global mean surface


temperature following a doubling of the atmospheric equivalent carbon dioxide (CO2 ) concentration. Owing to computational constraints, the equilibrium climate sensitivity in a climate model is sometimes estimated by running an atmospheric general circulation model coupled to a mixed-layer ocean model, because equilibrium climate sensitivity is largely determined by atmospheric processes. Efficient models can be run to equilibrium with a dynamic ocean. The climate sensitivity parameter (units: °C (W m–2)–1) refers to the equilibrium change in the annual global mean surface temperature following a unit change in radiative forcing. The effective climate sensitivity (units: °C) is an estimate of the global mean surface temperature response to doubled CO2 concentration that is evaluated from model output or observations for evolving non- equilibrium conditions. It is a measure of the strengths of the climate feedbacks at a particular time and may vary with forcing history and climate state and therefore may differ from equilibrium climate sensitivity. The transient climate response (units: °C) is the change in the global mean surface temperature, averaged over a 20-year period, centered at the time of atmospheric CO2 doubling, in a climate model simulation in which CO2 increases at 1%/yr. It is a measure of the strength and rapidity of the surface temperature response to greenhouse gas (GHG) forcing. {WGI, II, III} Climate system The climate system is the highly complex system consisting of five major components: the atmosphere, the hydrosphere, the cryosphere, the lithosphere and the biosphere and the interactions between them. The climate system evolves in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations and anthropogenic forcings such as the changing composition of the atmosphere and land-use change. {WGI, II, III} Climate variability Climate variability refers to variations in the mean state and other statistics (such as standard deviations, the occurrence of extremes, etc.) of the climate on all spatial and temporal scales beyond that of individual weather events. Variability may be due to natural internal processes within the climate system (internal variability), or to variations in natural or anthropogenic external forcing (external variability). See also Climate change. {WGI, II, III} CO2-equivalent (CO2-eq) concentration The concentration of carbon dioxide (CO2) that would cause the same radiative forcing as a given mixture of CO2 and other forcing components. Those values may consider only greenhouse gases (GHGs), or a combination of GHGs, aerosols and surface albedo change. CO2-equivalent concentration is a metric for comparing radiative forcing of a mix of different forcing components at a particular time but does not imply equivalence of the corresponding climate change responses nor future forcing. There is generally no connection between CO2-equivalent emissions and resulting CO2-equivalent concentrations. {WGI, III} CO2-equivalent (CO2-eq) emission The amount of carbon dioxide (CO2) emission that would cause the same integrated radiative forcing, over a given time horizon, as an emitted amount of a greenhouse gas (GHG) or a mixture of GHGs. The CO2-equivalent emission is obtained by multiplying the emission of a GHG by its Global Warming Potential (GWP) for the given time horizon (see WGI Chapter 8, Table 8.A.1 and WGIII Annex II.9.1 for GWP values of the different GHGs used here). For a mix of GHGs it is obtained by summing the CO2-equivalent emissions of each gas. CO2-equivalent emission is a common scale for comparing emissions of different GHGs but does not imply equivalence of the corresponding climate change responses. There is generally no connection between CO2-equivalent emissions and resulting CO2-equivalent concentrations. {WGI, III} Co-benefits The positive effects that a policy or measure aimed at one objective might have on other objectives, irrespective of the net effect on overall social welfare. Co-benefits are often subject to uncertainty and depend on local circumstances and implementation practices, among other factors. Co-benefits are also referred to as ancillary benefits. {WGII, III} Confidence The validity of a finding based on the type, amount, quality and consistency of evidence (e.g., mechanistic understanding, theory, data, models, expert judgment) and on the degree of agreement. In this report, confidence is expressed qualitatively (Mastrandrea et al., 2010). See WGI AR5 Figure 1.11 for the levels of confidence; see WGI AR5 Table 1.2 for the list of likelihood qualifiers; see WGII AR5 Box 1-1. See also Uncertainty. {WGI, II, III} Cost-effectiveness A policy is more cost-effective if it achieves a given policy goal at lower cost. Integrated models approximate cost‐effective solutions, unless they are specifically constrained to behave otherwise. Cost-effective mitigation scenarios are those based on a stylized implementation approach in which a single price on carbon dioxide (CO2) and other greenhouse gases (GHGs) is applied across the globe in every sector of every country and that rises over time in a way that achieves lowest global discounted costs. {WGIII} Decarbonization The process by which countries or other entities aim to achieve a low-carbon economy, or by which individuals aim to reduce their consumption of carbon. {WGII, III} Deforestation Conversion of forest to non-forest. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000b). See also information provided by the United Nations Framework Convention on Climate Change (UNFCCC, 2013) and the report on Definitions and Methodological Options to Inventory Emissions from Direct Human-induced Degradation of Forests and Devegetation of Other Vegetation Types (IPCC, 2003). {WGI, II} Detection and attribution Detection of change is defined as the process of demonstrating that climate or a system affected by climate has changed in some defined statistical sense, without providing a reason for that change. An identified change is detected in observations if its likelihood of occurrence by chance due to internal variability alone is determined to be small,


for example, <10%. Attribution is defined as the process of evaluating the relative contributions of multiple causal factors to a change or event with an assignment of statistical confidence (Hegerl et al., 2010). {WGI, II} Detection of impacts of climate change For a natural, human or managed system, identification of a change from a specified baseline. The baseline characterizes behavior in the absence of climate change and may be stationary or non-stationary (e.g., due to land-use change). {WGII} Disaster Severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting with vulnerable social conditions, leading to widespread adverse human, material, economic or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery. {WGII} Discounting A mathematical operation making monetary (or other) amounts received or expended at different times (years) comparable across time. The discounter uses a fixed or possibly time‐varying discount rate (>0) from year to year that makes future value worth less today. {WGII, III} Drought A period of abnormally dry weather long enough to cause a serious hydrological imbalance. Drought is a relative term; therefore any discussion in terms of precipitation deficit must refer to the particular precipitation-related activity that is under discussion. For example, shortage of precipitation during the growing season impinges on crop production or ecosystem function in general (due to soil moisture drought, also termed agricultural drought) and during the runoff and percolation season primarily affects water supplies (hydrological drought). Storage changes in soil moisture and groundwater are also affected by increases in actual evapotranspiration in addition to reductions in precipitation. A period with an abnormal precipitation deficit is defined as a meteorological drought. A megadrought is a very lengthy and pervasive drought, lasting much longer than normal, usually a decade or more. For the corresponding indices, see WGI AR5 Box 2.4. {WGI, II} Early warning system The set of capacities needed to generate and disseminate timely and meaningful warning information to enable individuals, communities and organizations threatened by a hazard to prepare to act promptly and appropriately to reduce the possibility of harm or loss4. {WGII} Earth System Model (ESM) A coupled atmosphere–ocean general circulation model in which a representation of the carbon cycle is included, allowing for interactive calculation of atmospheric CO2 or compatible emissions. Additional components (e.g., atmospheric chemistry, ice sheets, dynamic vegetation, nitrogen cycle, but also urban or crop models) may be included. See also Climate model. {WGI, II} Ecosystem An ecosystem is a functional unit consisting of living organisms, their non-living environment and the interactions within and between them. The components included in a given ecosystem and its spatial boun- daries depend on the purpose for which the ecosystem is defined: in some cases they are relatively sharp, while in others they are diffuse. Ecosystem boundaries can change over time. Ecosystems are nested within other ecosystems and their scale can range from very small to the entire biosphere. In the current era, most ecosystems either contain people as key organisms, or are influenced by the effects of human activities in their environment. {WGI, II, III} Ecosystem services Ecological processes or functions having monetary or non-monetary value to individuals or society at large. These are frequently classified as (1) supporting services such as productivity or biodiversity maintenance, (2) provisioning services such as food, fiber or fish, (3) regulating services such as climate regulation or carbon sequestration and (4) cultural services such as tourism or spiritual and aesthetic appreciation. {WGII, III} El Niño-Southern Oscillation (ENSO) The term El Niño was initially used to describe a warm-water current that periodically flows along the coast of Ecuador and Peru, disrupting the local fishery. It has since become identified with a basin-wide warming of the tropical Pacific Ocean east of the dateline. This oceanic event is associated with a fluctuation of a global-scale tropical and subtropical surface pressure pattern called the Southern Oscillation. This coupled atmosphere–ocean phenomenon, with preferred time scales of two to about seven years, is known as the El Niño-Southern Oscillation (ENSO). It is often measured by the surface pressure anomaly difference between Tahiti and Darwin or the sea surface temperatures in the central and eastern equatorial Pacific. During an ENSO event, the prevailing trade winds weaken, reducing upwelling and altering ocean currents such that the sea surface temperatures warm, further weakening the trade winds. This event has a great impact on the wind, sea surface temperature and precipitation patterns in the tropical Pacific. It has climatic effects throughout the Pacific region and in many other parts of the world, through global teleconnections. The cold phase of ENSO is called La Niña. For the corresponding indices, see WGI AR5 Box 2.5. {WGI, II} Emission scenario A plausible representation of the future development of emissions of substances that are potentially radiatively active (e.g., greenhouse gases (GHGs), aerosols) based on a coherent and internally consistent set of assumptions about driving forces (such as demographic and socio-economic development, technological change, energy and land use) and their key relationships. Concentration scenarios, derived from emission scenarios, are used as input to a climate model to compute climate projections. In IPCC (1992) a set of emission scenarios was presented which were used as a basis for the climate projections in IPCC (1996). These emission scenarios are referred to as the IS92 scenarios. In the IPCC Special Report on Emissions Scenarios (IPCC, 2000a) emission scenarios, the so-called SRES scenarios, were published, some of This glossary entry builds from the definitions used in UNISDR (2009) and IPCC (2012a).


which were used, among others, as a basis for the climate projections presented in Chapters 9 to 11 of IPCC WGI TAR (IPCC, 2001a) and Chapters 10 and 11 of IPCC WGI AR4 (IPCC, 2007) as well as in the IPCC WGI AR5 (IPCC, 2013b). New emission scenarios for climate change, the four Representative Concentration Pathways, were developed for, but independently of, the present IPCC assessment. See also Baseline/reference, Mitigation scenario and Transformation pathway. {WGI, II, III} Energy access Access to clean, reliable and affordable energy services for cooking and heating, lighting, communications and productive uses (AGECC, 2010). {WGIII} Energy intensity The ratio of energy use to economic or physical output. {WGIII} Energy security The goal of a given country, or the global community as a whole, to maintain an adequate, stable and predictable energy supply. Measures encompass safeguarding the sufficiency of energy resources to meet national energy demand at competitive and stable prices and the resilience of the energy supply; enabling development and deployment of technologies; building sufficient infrastructure to generate, store and transmit energy supplies and ensuring enforceable contracts of delivery. {WGIII} Ensemble A collection of model simulations characterizing a climate prediction or projection. Differences in initial conditions and model formulation result in different evolutions of the modeled system and may give information on uncertainty associated with model error and error in initial conditions in the case of climate forecasts and on uncertainty associated with model error and with internally generated climate variability in the case of climate projections. {WGI, II} Equilibrium climate sensitivity See Climate sensitivity. {WGI} Eutrophication Over-enrichment of water by nutrients such as nitrogen and phosphorus. It is one of the leading causes of water quality impairment. The two most acute symptoms of eutrophication are hypoxia (or oxygen depletion) and harmful algal blooms. {WGII} Exposure The presence of people, livelihoods, species or ecosystems, environmental functions, services, and resources, infrastructure, or economic, social, or cultural assets in places and settings that could be adversely affected. {WGII} External forcing External forcing refers to a forcing agent outside the climate system causing a change in the climate system. Volcanic eruptions, solar variations and anthropogenic changes in the composition of the atmosphere and land-use change are external forcings. Orbital forcing is also an external forcing as the insolation changes with orbital parameters eccentricity, tilt and precession of the equinox. {WGI, II} Extreme weather event An extreme weather event is an event that is rare at a particular place and time of year. Definitions of rare vary, but an extreme weather event would normally be as rare as or rarer than the 10th or 90th percentile of a probability density function estimated from observations. By definition, the characteristics of what is called extreme weather may vary from place to place in an absolute sense. When a pattern of extreme weather persists for some time, such as a season, it may be classed as an extreme climate event, especially if it yields an average or total that is itself extreme (e.g., drought or heavy rainfall over a season). {WGI, II} Feedback See Climate feedback. {WGI, II} Flood The overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas not normally submerged. Floods include river (fluvial) floods, flash floods, urban floods, pluvial floods, sewer floods, coastal floods and glacial lake outburst floods. {WGII} Food security A state that prevails when people have secure access to sufficient amounts of safe and nutritious food for normal growth, development and an active and healthy life. {WGII, III} Forest A vegetation type dominated by trees. Many definitions of the term forest are in use throughout the world, reflecting wide differences in biogeophysical conditions, social structure and economics. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000b). See also information provided by the United Nations Framework Convention on Climate Change (UNFCCC, 2013) and the Report on Definitions and Methodological Options to Inventory Emissions from Direct Human-induced Degradation of Forests and Devegetation of Other Vegetation Types (IPCC, 2003). {WGI, III} Fuel poverty A condition in which a household is unable to guarantee a certain level of consumption of domestic energy services (especially heating) or suffers disproportionate expenditure burdens to meet these needs. {WGIII} Geoengineering Geoengineering refers to a broad set of methods and technologies that aim to deliberately alter the climate system in order to alleviate the impacts of climate change. Most, but not all, methods seek to either (1) reduce the amount of absorbed solar energy in the climate system (Solar Radiation Management) or (2) increase net carbon sinks from the atmosphere at a scale sufficiently large to alter climate (Carbon Dioxide Removal). Scale and intent are of central importance. Two key characteristics of geoengineering methods of particular concern are that they use or affect the climate system (e.g., atmosphere, land or ocean) globally or regionally and/or could have substantive unintended effects that cross national boundaries. Geoengineering is different from weather modification and ecological engineering, but the boundary can be fuzzy (IPCC, 2012b, p. 2). {WGI, II, III}


Global climate model (also referred to as general circulation model, both abbreviated as GCM) See Climate model. {WGI, II} Global Temperature change Potential (GTP) An index measuring the change in global mean surface temperature at a chosen point in time following an emission of a unit mass of a given substance, relative to that of the reference substance, carbon dioxide (CO2). The Global Temperature change Potential (GTP) thus represents the combined effect of the differing times these substances remain in the atmosphere, their effectiveness in causing radiative forcing and the response of the climate system. The GTP has been defined in two different ways: • Fixed GTP: based on a fixed time horizon in the future (such as GTP100 for a time horizon of 100 years) • Dynamic GTP: based on a target year (such as the year when global mean temperature is expected to reach a target level). In the dynamic GTP, the time horizon reduces over time as the target year is approached and hence the GTP value changes for emissions occurring further in the future. {WGI Chapter 8} Global warming Global warming refers to the gradual increase, observed or projected, in global surface temperature, as one of the consequences of radiative forcing caused by anthropogenic emissions. {WGIII} Global Warming Potential (GWP) An index measuring the radiative forcing following an emission of a unit mass of a given substance, accumulated over a chosen time horizon, relative to that of the reference substance, carbon dioxide (CO2). The GWP thus represents the combined effect of the differing times these substances remain in the atmosphere and their effectiveness in causing radiative forcing. (WGI, III} Hazard The potential occurrence of a natural or human-induced physical event or trend or physical impact that may cause loss of life, injury, or other health impacts, as well as damage and loss to property, infrastructure, livelihoods, service provision, ecosystems and environmental resources. In this report, the term hazard usually refers to climate-related physical events or trends or their physical impacts. {WGII} Heat wave A period of abnormally and uncomfortably hot weather. {WGI, II} Hydrological cycle The cycle in which water evaporates from the oceans and the land surface, is carried over the Earth in atmospheric circulation as water vapour, condenses to form clouds, precipitates over ocean and land as rain or snow, which on land can be intercepted by trees and vegetation, provides runoff on the land surface, infiltrates into soils, recharges groundwater, discharges into streams and ultimately flows out into the oceans, from which it will eventually evaporate again. The various systems involved in the hydrological cycle are usually referred to as hydrological systems. {WGI, II} Impacts (consequences, outcomes) Effects on natural and human systems. In this report, the term impacts is used primarily to refer to the effects on natural and human systems of extreme weather and climate events and of climate change. Impacts generally refer to effects on lives, livelihoods, health, ecosystems, economies, societies, cultures, services and infrastructure due to the interaction of climate changes or hazardous climate events occurring within a specific time period and the vulnerability of an exposed society or system. Impacts are also referred to as consequences and outcomes. The impacts of climate change on geophysical systems, including floods, droughts and sea level rise, are a subset of impacts called physical impacts. {WGII} Indirect emissions Emissions that are a consequence of the activities within well-defined boundaries of, for instance, a region, an economic sector, a company or process, but which occur outside the specified boundaries. For example, emissions are described as indirect if they relate to the use of heat but physically arise outside the boundaries of the heat user, or to electricity production but physically arise outside of the boundaries of the power supply sector. {WGIII} Industrial Revolution A period of rapid industrial growth with far-reaching social and economic consequences, beginning in Britain during the second half of the 18th century and spreading to Europe and later to other countries including the United States. The invention of the steam engine was an important trigger of this development. The industrial revolution marks the beginning of a strong increase in the use of fossil fuels and emission of, in particular, fossil carbon dioxide (CO2). In this report the terms pre-industrial and industrial refer, somewhat arbitrarily, to the periods before and after 1750, respectively. {WGI, II, III} Integrated assessment A method of analysis that combines results and models from the physical, biological, economic and social sciences and the interactions among these components in a consistent framework to evaluate the status and the consequences of environmental change and the policy responses to it. See also Integrated models. {WGII, III} Integrated Coastal Zone Management (ICZM) An integrated approach for sustainably managing coastal areas, taking into account all coastal habitats and uses. {WGII} Integrated models Integrated models explore the interactions between multiple sectors of the economy or components of particular systems, such as the energy system. In the context of transformation pathways, they refer to models that, at a minimum, include full and disaggregated representations of the energy system and its linkage to the overall economy that will allow for consideration of interactions among different elements of that system. Integrated models may also include representations of the full economy, land use and land-use change (LUC) and the climate system. See also Integrated assessment. {WGIII} Internal variability See Climate variability. {WGI}


Irreversibility A perturbed state of a dynamical system is defined as irreversible on a given timescale, if the recovery timescale from this state due to natural processes is substantially longer than the time it takes for the system to reach this perturbed state. In the context of this report, the time scale of interest is centennial to millennial. See also Tipping point. {WGI} Land use and land-use change Land use refers to the total of arrangements, activities and inputs undertaken in a certain land cover type (a set of human actions). The term land use is also used in the sense of the social and economic purposes for which land is managed (e.g., grazing, timber extraction and conservation). In urban settlements it is related to land uses within cities and their hinterlands. Urban land use has implications on city management, structure and form and thus on energy demand, greenhouse gas (GHG) emissions and mobility, among other aspects. {WGI, II, III} Land-use change (LUC) Land-use change refers to a change in the use or management of land by humans, which may lead to a change in land cover. Land cover and land-use change may have an impact on the surface albedo, evapotranspiration, sources and sinks of greenhouse gases (GHGs), or other properties of the climate system and may thus give rise to radiative forcing and/or other impacts on climate, locally or globally. See also the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000b). Indirect land-use change (iLUC) Indirect land-use change refers to shifts in land use induced by a change in the production level of an agricultural product elsewhere, often mediated by markets or driven by policies. For example, if agricultural land is diverted to fuel production, forest clearance may occur elsewhere to replace the former agricultural production. See also Agriculture, Forestry and Other Land Use (AFOLU), Afforestation, Deforestation and Reforestation. Leakage Phenomena whereby the reduction in emissions (relative to a baseline) in a jurisdiction/sector associated with the implementation of mitigation policy is offset to some degree by an increase outside the jurisdiction/sector through induced changes in consumption, production, prices, land use and/or trade across the jurisdictions/sectors. Leakage can occur at a number of levels, be it a project, state, province, nation or world region. In the context of Carbon Dioxide Capture and Storage (CCS), CO2 leakage refers to the escape of injected carbon dioxide (CO2) from the storage location and eventual release to the atmosphere. In the context of other substances, the term is used more generically, such as for methane (CH4) leakage (e.g., from fossil fuel extraction activities) and hydrofluorocarbon (HFC) leakage (e.g., from refrigeration and air- conditioning systems). {WGIII} Likelihood The chance of a specific outcome occurring, where this might be estimated probabilistically. Likelihood is expressed in this report using a standard terminology (Mastrandrea et al., 2010), defined in WGI AR5 Table 1.2 and WGII AR5 Box 1-1. See also Confidence and Uncertainty. {WGI, II, III} Lock-in Lock-in occurs when a market is stuck with a standard even though participants would be better off with an alternative. In this report, lock-in is used more broadly as path dependence, which is the generic situation where decisions, events or outcomes at one point in time constrain adaptation, mitigation or other actions or options at a later point in time. {WGII, III} Low regrets policy A policy that would generate net social and/or economic benefits under current climate and a range of future climate change scenarios. {WGII} Marine-based ice sheet An ice sheet containing a substantial region that rests on a bed lying below sea level and whose perimeter is in contact with the ocean. The best known example is the West Antarctic ice sheet. {WGI} Meridional Overturning Circulation (MOC) Meridional (north–south) overturning circulation in the ocean quantified by zonal (east–west) sums of mass transports in depth or density layers. In the North Atlantic, away from the subpolar regions, the MOC (which is in principle an observable quantity) is often identified with the thermohaline circulation (THC), which is a conceptual and incomplete interpretation. It must be borne in mind that the MOC is also driven by wind and can also include shallower overturning cells such as occur in the upper ocean in the tropics and subtropics, in which warm (light) waters moving poleward are transformed to slightly denser waters and subducted equatorward at deeper levels. {WGI, II} Mitigation (of climate change) A human intervention to reduce the sources or enhance the sinks of greenhouse gases (GHGs). This report also assesses human interventions to reduce the sources of other substances which may contribute directly or indirectly to limiting climate change, including, for example, the reduction of particulate matter emissions that can directly alter the radiation balance (e.g., black carbon) or measures that control emissions of carbon monoxide, nitrogen oxides, Volatile Organic Compounds and other pollutants that can alter the concentration of tropospheric ozone which has an indirect effect on the climate. {WGI, II, III} Mitigation scenario A plausible description of the future that describes how the (studied) system responds to the implementation of mitigation policies and measures. See also Baseline/reference, Emission scenario, Representative Concentration Pathways (RCPs), SRES scenarios and Transformation pathway. {WGIII} Net negative emissions A situation of net negative emissions is achieved when, as result of human activities, more greenhouse gases (GHGs) are sequestered or stored than are released into the atmosphere. {SYR Box 2.2, footnote 29} Ocean acidification Ocean acidification refers to a reduction in the pH of the ocean over an extended period, typically decades or longer, which is caused primarily


by uptake of carbon dioxide (CO2) from the atmosphere, but can also be caused by other chemical additions or subtractions from the ocean. Anthropogenic ocean acidification refers to the component of pH reduction that is caused by human activity (IPCC, 2011, p. 37). {WGI, II} Overshoot pathways Emissions, concentration or temperature pathways in which the metric of interest temporarily exceeds, or overshoots the long-term goal. {WGIII} Oxygen Minimum Zone (OMZ) The midwater layer (200–1000 m) in the open ocean in which oxygen saturation is the lowest in the ocean. The degree of oxygen depletion depends on the largely bacterial consumption of organic matter and the distribution of the OMZs is influenced by large-scale ocean circulation. In coastal oceans, OMZs extend to the shelves and may also affect benthic ecosystems. {WGII} Permafrost Ground (soil or rock and included ice and organic material) that remains at or below 0°C for at least two consecutive years. {WGI, II} pH pH is a dimensionless measure of the acidity of water (or any solution) given by its concentration of hydrogen ions (H+). pH is measured on a logarithmic scale where pH = –log10(H+). Thus, a pH decrease of unit corresponds to a 10-fold increase in the concentration of H+, or acidity. {WGI} Poverty Poverty is a complex concept with several definitions stemming from different schools of thought. It can refer to material circumstances (such as need, pattern of deprivation or limited resources), economic conditions (such as standard of living, inequality or economic position) and/or social relationships (such as social class, dependency, exclusion, lack of basic security or lack of entitlement). {WGII} Pre-industrial See Industrial Revolution. {WGI, II, III} Private costs Private costs are carried by individuals, companies or other private entities that undertake an action, whereas social costs include additionally the external costs on the environment and on society as a whole. Quantitative estimates of both private and social costs may be incomplete, because of difficulties in measuring all relevant effects. {WGIII} Projection A projection is a potential future evolution of a quantity or set of quantities, often computed with the aid of a model. Unlike predictions, projections are conditional on assumptions concerning, for example, future socio-economic and technological developments that may or may not be realized. See also Climate projection. {WGI, II} Radiative forcing The strength of drivers is quantified as Radiative Forcing (RF) in units watts per square meter (W/m2) as in previous IPCC assessments. RF is the change in energy flux caused by a driver and is calculated at the tropopause or at the top of the atmosphere. {WGI} Reasons For Concern (RFCs) Elements of a classification framework, first developed in the IPCC Third Assessment Report (IPCC, 2001b), which aims to facilitate judgments about what level of climate change may be dangerous (in the language of Article 2 of the United Nations Framework Convention on Climate Change (UNFCCC)) by aggregating impacts, risks and vulnerabilities. {WGII} Reducing Emissions from Deforestation and Forest Degradation (REDD) An effort to create financial value for the carbon stored in forests, offering incentives for developing countries to reduce emissions from forested lands and invest in low-carbon paths to sustainable development (SD). It is therefore a mechanism for mitigation that results from avoiding deforestation. REDD+ goes beyond reforestation and forest degradation and includes the role of conservation, sustainable management of forests and enhancement of forest carbon stocks. The concept was first introduced in 2005 in the 11th Session of the Conference of the Parties (COP) in Montreal and later given greater recognition in the 13th Session of the COP in 2007 at Bali and inclusion in the Bali Action Plan which called for ‘policy approaches and positive incentives on issues relating to reducing emissions from deforestation and forest degradation in developing countries (REDD) and the role of conservation, sustainable management of forests and enhancement of forest carbon stock in developing countries’. Since then, support for REDD has increased and has slowly become a framework for action supported by a number of countries. {WGIII} Reforestation Planting of forests on lands that have previously contained forests but that have been converted to some other use. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000b). See also information provided by the United Nations Framework Convention on Climate Change (UNFCCC, 2013). See also the Report on Definitions and Methodological Options to Inventory Emissions from Direct Human-induced Degradation of Forests and Devegetation of Other Vegetation Types (IPCC, 2003). {WGI, II, III} Representative Concentration Pathways (RCPs) Scenarios that include time series of emissions and concentrations of the full suite of greenhouse gases (GHGs) and aerosols and chemically active gases, as well as land use/land cover (Moss et al., 2008). The word representative signifies that each RCP provides only one of many possible scenarios that would lead to the specific radiative forcing characteristics. The term pathway emphasizes that not only the long-term concentration levels are of interest, but also the trajectory taken over time to reach that outcome (Moss et al., 2010). RCPs usually refer to the portion of the concentration pathway extending up to 2100, for which Integrated Assessment Models produced corresponding emission scenarios. Extended Concentration Pathways (ECPs) describe extensions of the RCPs from 2100 to 2500 that were


calculated using simple rules generated by stakeholder consultations and do not represent fully consistent scenarios. Four RCPs produced from Integrated Assessment Models were selected from the published literature and are used in the present IPCC Assessment as a basis for the climate predictions and projections presented in WGI AR5 Chapters 11 to 14 (IPCC, 2013b): RCP2.6 One pathway where radiative forcing peaks at approximately W/m2 before 2100 and then declines (the corresponding ECP assuming constant emissions after 2100). RCP4.5 and RCP6.0 Two intermediate stabilization pathways in which radiative forcing is stabilized at approximately 4.5 W/m2 and 6.0 W/m2 after 2100 (the corresponding ECPs assuming constant concentrations after 2150). RCP8.5 One high pathway for which radiative forcing reaches >8.5 W/m2 by 2100 and continues to rise for some amount of time (the corresponding ECP assuming constant emissions after 2100 and constant concentrations after 2250). For further description of future scenarios, see WGI AR5 Box 1.1. See also van Vuuren et al., 2011. {WGI, II, III} Resilience The capacity of social, economic and environmental systems to cope with a hazardous event or trend or disturbance, responding or reorganizing in ways that maintain their essential function, identity and structure, while also maintaining the capacity for adaptation, learning and transformation5. {WGII, III} Risk The potential for consequences where something of value is at stake and where the outcome is uncertain, recognizing the diversity of values. Risk is often represented as probability or likelihood of occurrence of hazardous events or trends multiplied by the impacts if these events or trends occur. In this report, the term risk is often used to refer to the potential, when the outcome is uncertain, for adverse consequences on lives, livelihoods, health, ecosystems and species, economic, social and cultural assets, services (including environmental services) and infrastructure. {WGII, III} Risk management The plans, actions or policies to reduce the likelihood and/or consequences of risks or to respond to consequences. {WGII} Sequestration The uptake (i.e., the addition of a substance of concern to a reservoir) of carbon containing substances, in particular carbon dioxide (CO2), in terrestrial or marine reservoirs. Biological sequestration includes direct removal of CO2 from the atmosphere through land-use change (LUC), afforestation, reforestation, revegetation, carbon storage in landfills and practices that enhance soil carbon in agriculture (cropland management, grazing land management). In parts of the literature, but not in this report, (carbon) sequestration is used to refer to Carbon Dioxide Capture and Storage (CCS). {WGIII} Sink Any process, activity or mechanism that removes a greenhouse gas (GHG), an aerosol or a precursor of a GHG or aerosol from the atmosphere. {WGI, II, III} Social cost of carbon The net present value of climate damages (with harmful damages expressed as a positive number) from one more tonne of carbon in the form of carbon dioxide (CO2), conditional on a global emissions trajectory over time. {WGII, III} Social costs See Private costs. {WGIII} Solar Radiation Management (SRM) Solar Radiation Management refers to the intentional modification of the Earth’s shortwave radiative budget with the aim to reduce climate change according to a given metric (e.g., surface temperature, precipitation, regional impacts, etc.). Artificial injection of stratospheric aerosols and cloud brightening are two examples of SRM techniques. Methods to modify some fast-responding elements of the long wave radiative budget (such as cirrus clouds), although not strictly speaking SRM, can be related to SRM. SRM techniques do not fall within the usual definitions of mitigation and adaptation (IPCC, 2012b, p. 2). See also Carbon Dioxide Removal (CDR) and Geoengineering. {WGI, III} SRES scenarios SRES scenarios are emission scenarios developed by IPCC (2000a) and used, among others, as a basis for some of the climate projections shown in Chapters 9 to 11 of IPCC WGI TAR (IPCC, 2001a), Chapters 10 and 11 of IPCC WGI AR4 (IPCC, 2007), as well as in the IPCC WGI AR5 (IPCC, 2013b). {WGI, II, III} Storm surge The temporary increase, at a particular locality, in the height of the sea due to extreme meteorological conditions (low atmospheric pressure and/or strong winds). The storm surge is defined as being the excess above the level expected from the tidal variation alone at that time and place. {WGI, II} Structural change Changes, for example, in the relative share of gross domestic product (GDP) produced by the industrial, agricultural, or services sectors of an economy, or more generally, systems transformations whereby some components are either replaced or potentially substituted by other components. {WGIII} Sustainability A dynamic process that guarantees the persistence of natural and human systems in an equitable manner. {WGII, III} This definition builds from the definition used in Arctic Council (2013).


Sustainable development Development that meets the needs of the present without compromising the ability of future generations to meet their own needs (WCED, 1987). {WGII, III} Thermal expansion In connection with sea level, this refers to the increase in volume (and decrease in density) that results from warming water. A warming of the ocean leads to an expansion of the ocean volume and hence an increase in sea level. {WGI, II} Tipping point A level of change in system properties beyond which a system reorganizes, often abruptly, and does not return to the initial state even if the drivers of the change are abated. For the climate system, it refers to a critical threshold when global or regional climate changes from one stable state to another stable state. The tipping point event may be irreversible. See also Irreversibility. {WGI, II, III} Transformation A change in the fundamental attributes of natural and human systems. {WGII} Transformation pathway The trajectory taken over time to meet different goals for greenhouse gas (GHG) emissions, atmospheric concentrations, or global mean surface temperature change that implies a set of economic, technological and behavioural changes. This can encompass changes in the way energy and infrastructure are used and produced, natural resources are managed and institutions are set up and in the pace and direction of technological change (TC). See also Baseline/reference, Emission scenario, Mitigation scenario, Representative Concentration Pathways (RCPs) and SRES scenarios. {WGIII} Transient Climate Response to Cumulative CO2 Emissions (TCRE) The transient global average surface temperature change per unit cumulated CO2 emissions, usually 1000 PgC. TCRE combines both information on the airborne fraction of cumulated CO2 emissions (the fraction of the total CO2 emitted that remains in the atmosphere) and on the transient climate response (TCR). {WGI} Uncertainty A state of incomplete knowledge that can result from a lack of information or from disagreement about what is known or even knowable. It may have many types of sources, from imprecision in the data to ambiguously defined concepts or terminology, or uncertain projections of human behaviour. Uncertainty can therefore be represented by quantitative measures (e.g., a probability density function) or by qualitative statements (e.g., reflecting the judgment of a team of experts) (see Moss and Schneider, 2000; Manning et al., 2004; Mastrandrea et al., 2010). See also Confidence and Likelihood. {WGI, II, III} Vulnerability The propensity or predisposition to be adversely affected. Vulnerability encompasses a variety of concepts and elements including sensitivity or susceptibility to harm and lack of capacity to cope and adapt. {WGII}
402 IPCC Special Report on Carbon dioxide Capture and Storage
Note: the definitions in this Annex refer to the use of the terms
in the context of this report. It provides an explanation of
specific terms as the authors intend them to be interpreted in
this report.
Abatement
Reduction in the degree or intensity of emissions or other
pollutants.
Absorption
Chemical or physical take-up of molecules into the bulk of a
solid or liquid, forming either a solution or compound.
Acid gas
Any gas mixture that turns to an acid when dissolved in water
(normally refers to H2S + CO2 from sour gas (q.v.)).
Adiabatic
A process in which no heat is gained or lost by the system.
Adsorption
The uptake of molecules on the surface of a solid or a liquid.
Afforestation
Planting of new forests on lands that historically have not
contained forests.
Aluminium silicate mineral
Natural mineral – such as feldspar, clays, micas, amphiboles
– composed of Al2O3 and SiO2 plus other cations.
Amine
Organic chemical compound containing one or more nitrogens
in -NH2, -NH or -N groups.
Anaerobic condition
Reducing condition that only supports life which does not
require free oxygen.
Anhydrite
Calcium sulphate: the common hydrous form is called
gypsum.
Antarctic Treaty
Applies to the area south of 60 degrees South, and declares
that Antarctica shall be used for peaceful purposes only.
Anthracite
Coal with the highest carbon content and therefore the highest
rank (q.v.).
Anthropogenic source
Source which is man-made as opposed to natural.
Anticline
Folded geological strata that is convex upwards.
API
American Petroleum Institute; degree API is a measure of oil
density given by (141.5/specific gravity) -131.5.
Aquifer
Geological structure containing water and with significant
permeability to allow flow; it is bound by seals.
Assessment unit
A geological province with high petroleum potential.
Assigned amount
The amount by which a Party listed in Annex B of the Kyoto
Protocol agrees to reduce its anthropogenic emissions.
ATR
Auto thermal reforming: a process in which the heat for the
reaction of CH4 with steam is generated by partial oxidation of
CH4.
Autoproduction
The production of electricity for own use.
Basalt
A type of basic igneous rock which is typically erupted from a
volcano.
Basel Convention
UN Convention on the Control of Transboundary Movements
of Hazardous Wastes and their Disposal, which was adopted at
Basel on 22 March 1989.
Baseline
The datum against which change is measured.
Basin
A geological region with strata dipping towards a common
axis or centre.
Bathymetric
Pertaining to the depth of water.
Benthic
Pertaining to conditions at depth in bodies of water.
Bicarbonate ion
The anion formed by dissolving carbon dioxide in water,
HCO3
-.
Biomass
Matter derived recently from the biosphere.
Biomass-based CCS
Carbon capture and storage in which the feedstock (q.v.) is
biomass
Annex II: Glossary, acronyms and abbreviations 403
Bituminous coal
An intermediate rank of coal falling between the extremes of
peat and anthracite, and closer to anthracite.
Blow-out
Refers to catastrophic failure of a well when the petroleum
fluids or water flow unrestricted to the surface.
Bohr effect
The pH-dependent change in the oxygen affinity of blood.
Bottom-up model
A model that includes technological and engineering details in
the analysis.
Boundary
In GHG accounting, the separation between accounting units,
be they national, organizational, operational, business units or
sectors.
Break-even price
The price necessary at a given level of production to cover all
costs.
Buoyancy
Tendency of a fluid or solid to rise through a fluid of higher
density.
Cap rock
Rock of very low permeability that acts as an upper seal to
prevent fluid flow out of a reservoir.
Capillary entry pressure
Additional pressure needed for a liquid or gas to enter a pore
and overcome surface tension.
Capture efficiency
The fraction of CO2 separated from the gas stream of a source
Carbon credit
A convertible and transferable instrument that allows an
organization to benefit financially from an emission reduction.
Carbon trading
A market-based approach that allows those with excess
emissions to trade that excess for reduced emissions
elsewhere.
Carbonate
Natural minerals composed of various anions bonded to a
CO3
2- cation (e.g. calcite, dolomite, siderite, limestone).
Carbonate neutralization
A method for storing carbon in the ocean based upon the
reaction of CO2 with a mineral carbonate such as limestone to
produce bicarbonate anions and soluble cations.
Casing
A pipe which is inserted to stabilize the borehole of a well
after it is drilled.
CBM
Coal bed methane
CCS
Carbon dioxide capture and storage
CDM
Clean development mechanism: a Kyoto Protocol mechanism
to assist non-Annex 1 countries to contribute to the objectives
of the Protocol and help Annex I countries to meet their
commitments.
Certification
In the context of carbon trading, certifying that a project
achieves a quantified reduction in emissions over a given
period.
Chemical looping combustion
A process in which combustion of a hydrocarbon fuel is split
into separate oxidation and reduction reactions by using a
metal oxide as an oxygen carrier between the two reactors.
Chlorite
A magnesium-iron aluminosilicate sheet silicate clay mineral.
Class “x” well
A regulatory classification for wells used for the injection of
fluids into the ground.
Claus plant
A plant that transforms H2S into elemental sulphur.
Cleats
The system of joints, cleavage planes, or planes of weakness
found in coal seams along which the coal fractures.
CO2 avoided
The difference between CO2 captured, transmitted and/or
stored, and the amount of CO2 generated by a system without
capture, net of the emissions not captured by a system with
CO2 capture.
CO2 equivalent
A measure used to compare emissions of different greenhouse
gases based on their global warming potential.
Co-benefit
The additional benefits generated by policies that are
implemented for a specific reason.
404 IPCC Special Report on Carbon dioxide Capture and Storage
COE
Cost of electricity, value as calculated by Equation 1 in
Section 3.7.
Co-firing
The simultaneous use of more than one fuel in a power plant
or industrial process.
Completion of a well
Refers to the cementing and perforating of casing and
stimulation to connect a well bore to reservoir.
Congruence
The quality of agreement between two entities.
Conservative values
Parameter values selected so that a parameter, such as CO2
leakage, is over-estimated.
Containment
Restriction of movement of a fluid to a designated volume
(e.g. reservoir).
Continental shelf
The extension of the continental mass beneath the ocean.
COREX
A process for producing iron.
Cryogenic
Pertaining to low temperatures, usually under about -100°C.
D, Darcy
A non-SI unit of permeability, abbreviated D, and
approximately = 1μm2.
Dawsonite
A mineral: dihydroxide sodium aluminium carbonate.
Deep saline aquifer
A deep underground rock formation composed of permeable
materials and containing highly saline fluids.
Deep sea
The sea below 1000m depth.
Default emissions factor
An approximate emission factor that may be used in the
absence of precise or measured values of an Emissions Factor.
Demonstration phase
Demonstration phase means that the technology is
implemented in a pilot project or on a small scale, but not yet
economically feasible at full scale.
Dense phase
A gas compressed to a density approaching that of the liquid.
Dense fluid
A gas compressed to a density approaching that of the liquid.
Depleted
Of a reservoir: one where production is significantly reduced.
Diagenesis
Processes that cause changes in sediment after it has been
deposited and buried under another layer.
DIC
Dissolved Inorganic Carbon.
Dip
In geology, the angle below the horizontal taken by rock strata.
Discharge
The amount of water issuing from a spring or in a stream that
passes a specific point in a given period of time.
Discordant sequence
In geology, sequence of rock strata that is markedly different
from strata above or below.
Dolomite
A magnesium-rich carbonate sedimentary rock. Also, a
magnesium-rich carbonate mineral (CaMgCO3).
Double-grip packer
A device used to seal a drill string equipped with two gripping
mechanisms.
Down-hole log
Record of conditions in a borehole.
Drill cuttings
The solid particles recovered during the drilling of a well.
Drill string
The assembly of drilling rods that leads from the surface to the
drilling tool.
Drive
Fluid flow created in formations by pressure differences
arising from borehole operations.
Dry ice
Solid carbon dioxide
Dynamic miscibility
The attainment of mixing following the prolonged injection of
gas into an oilfield.
Annex II: Glossary, acronyms and abbreviations 405
ECBM
Enhanced coal bed methane recovery; the use of CO2 to
enhance the recovery of the methane present in unminable
coal beds through the preferential adsorption of CO2 on coal.
Economic potential
The amount of greenhouse gas emissions reductions from
a specific option that could be achieved cost-effectively,
given prevailing circumstances (i.e. a market value of CO2
reductions and costs of other options).
Economically feasible under specific conditions
A technology that is well understood and used in selected
commercial applications, such as in a favourable tax regime or
a niche market, processing at least 0.1 MtCO2/yr, with a few
(less than 5) replications of the technology.
EGR
Enhanced gas recovery: the recovery of gas additional to that
produced naturally by fluid injection or other means.
Emission factor
A normalized measure of GHG emissions in terms of activity,
e.g., tonnes of GHG emitted per tonne of fuel consumed.
Emissions credit
A commodity giving its holder the right to emit a certain
quantity of GHGs (q.v.).
Emissions trading
A trading scheme that allows permits for the release of a
specified number of tonnes of a pollutant to be sold and
bought.
Endothermic
Concerning a chemical reaction that absorbs heat, or requires
heat to drive it.
Enhanced gas recovery
See EGR.
Enhanced oil recovery
See EOR
Entrained flow
Flow in which a solid or liquid, in the form of fine particles, is
transported in diluted form by high velocity gas.
Entrainment gas
The gas employed in entrained flow (q.v.).
EOR
Enhanced oil recovery: the recovery of oil additional to that
produced naturally by fluid injection or other means.
Euphotic zone
The zone of the ocean reached by sunlight.
Evaporite
A rock formed by evaporation.
Exothermic
Concerning a chemical reaction that releases heat, such as
combustion.
Ex-situ mineralization
A process where minerals are mined, transferred to an
industrial facility, reacted with carbon dioxide and processed.
Exsolution
The formation of different phases during the cooling of a
homogeneous fluid.
Extended reach well
Borehole that is diverted into a more horizontal direction to
extend its reach.
Extremophile
Microbe living in environments where life was previously
considered impossible.
Far field
A region remote from a signal source.
Fault
In geology, a surface at which strata are no longer continuous,
but displaced.
Fault reactivation
The tendency for a fault to become active, i.e. for movement
to occur.
Fault slip
The extent to which a fault has slipped in past times.
FBC
Fluidized bed combustion: – combustion in a fluidized bed
(q.v.).
Feldspar
A group of alumino-silicate minerals that makes up much of
the Earth’s crust.
Feedstock
The material that is fed to a process
FGD
Flue gas desulphurization.
Fischer-Tropsch
A process that transforms a gas mixture of CO and H2 into
liquid hydrocarbons and water.
406 IPCC Special Report on Carbon dioxide Capture and Storage
Fixation
The immobilization of CO2 by its reaction with another
material to produce a stable compound
Fixed bed
A gas-solid contactor or reactor formed by a bed of stationary
solid particles that allows the passage of gas between the
particles.
Flood
The injection of a fluid into an underground reservoir.
Flue gas
Gases produced by combustion of a fuel that are normally
emitted to the atmosphere.
Fluidized bed
A gas-solid contactor or reactor comprising a bed of fine
solid particles suspended by passing a gas through the bed at
sufficiently high velocity.
Folding
In geology, the bending of rock strata from the plane in which
they were formed.
Formation
A body of rock of considerable extent with distinctive
characteristics that allow geologists to map, describe, and
name it.
Formation water
Water that occurs naturally within the pores of rock
formations.
Fouling
Deposition of a solid on the surface of heat or mass transfer
equipment that has the effect of reducing the heat or mass
transfer.
Fracture
Any break in rock along which no significant movement has
occurred.
Fuel cell
Electrochemical device in which a fuel is oxidized in a
controlled manner to produce an electric current and heat
directly.
Fugitive emission
Any releases of gases or vapours from anthropogenic activities
such as the processing or transportation of gas or petroleum.
FutureGen Project
US Government initiative for a new power station with low
CO2 emissions.
Gas turbine
A machine in which a fuel is burned with compressed air or
oxygen and mechanical work is recovered by the expansion of
the hot products.
Gasification
Process by which a carbon-containing solid fuel is transformed
into a carbon- and hydrogen-containing gaseous fuel by
reaction with air or oxygen and steam.
Geochemical trapping
The retention of injected CO2 by geochemical reactions.
Geological setting
The geological environment of various locations.
Geological time
The time over which geological processes have taken place.
Geomechanics
The science of the movement of the Earth’s crust.
Geosphere
The earth, its rocks and minerals, and its waters.
Geothermal
Concerning heat flowing from deep in the earth.
GHG
Greenhouse gases: carbon dioxide (CO2), methane
(CH4), nitrous oxide (N2O), hydroflurocarbons (HFCs),
perfluorocarbons (PFCs), and sulphur hexafluoride (SF6).
Hazardous and non-hazardous waste
Potentially harmful and non-harmful substances that have
been released or discarded into the environment.
Hazardous waste directive
European directive in force to regulate definitions of waste
classes and to regulate the handling of the waste classes.
HAZOP
HAZard and OPerability, a process used to assess the risks of
operating potentially hazardous equipment.
Helsinki Convention
International legal convention protecting the Baltic water
against pollution.
Henry’s Law
States that the solubility of a gas in a liquid is proportional to
the partial pressure of the gas in contact with the liquid.
HHV
Higher heating value: the energy released from the combustion
of a fuel that includes the latent heat of water.
Annex II: Glossary, acronyms and abbreviations 407
Host rock
In geology, the rock formation that contains a foreign material.
Hybrid vehicle
Vehicle that combines a fossil fuel internal combustion engine
and an alternative energy source, typically batteries.
Hydrate
An ice-like compound formed by the reaction of water and
CO2, CH4 or similar gases.
Hydrodynamic trap
A geological structure in which fluids are retained by low
levels of porosity in the surrounding rocks.
Hydrogeological
Concerning water in the geological environment.
Hydrostatic
Pertaining to the properties of a stationary body of water.
Hypercapnia
Excessively high CO2 levels in the blood.
Hypoxia
Having low rates of oxygen transfer in living tissue.
Hysteresis
The phenomenon of a lagging recovery from deformation or
other disturbance.
IEA GHG
International Energy Agency – Greenhouse Gas R&D
Programme.
IGCC
Integrated gasification combined cycle: power generation in
which hydrocarbons or coal are gasified (q.v.) and the gas is
used as a fuel to drive both a gas and a steam turbine.
Igneous
Rock formed when molten rock (magma) has cooled and
solidified (crystallized).
Immature basin
A basin in which the processes leading to oil or gas formation
have started but are incomplete.
Infrared spectroscopy
Chemical analysis using infrared spectroscope method.
Injection
The process of using pressure to force fluids down wells.
Injection well
A well in which fluids are injected rather than produced.
Injectivity
A measure of the rate at which a quantity of fluid can be
injected into a well.
In-situ mineralization
A process where minerals are not mined: carbon dioxide
is injected in the silicate formation where it reacts with the
minerals, forming carbonates and silica.
International Seabed Authority
An organization established under the 1982 UN Convention
on the Law of the Sea, headquartered in Kingston, Jamaica.
Ion
An atom or molecule that has acquired a charge by either
gaining or losing electrons.
IPCC
Intergovernmental Panel on Climate Change
JI
Joint Implementation: under the Kyoto Protocol, it allows a
Party with a GHG emission target to receive credits from other
Annex 1 Parties.
Kyoto Protocol
Protocol to the United Nations Framework Convention on
Climate Change, which was adopted at Kyoto on 11 December
1997.
Leach
To dissolve a substance from a solid.
Leakage
In respect of carbon trading, the change of anthropogenic
emissions by sources or removals by sinks which occurs
outside the project boundary.
Leakage
In respect of carbon storage, the escape of injected fluid from
storage.
Levellized cost
The future values of an input or product that would make the
NPV (q.v.) of a project equal to zero.
LHV
Lower heating value: energy released from the combustion of
a fuel that excludes the latent heat of water.
Lignite/sub-bituminous coal
Relatively young coal of low rank with a relatively high
hydrogen and oxygen content.
408 IPCC Special Report on Carbon dioxide Capture and Storage
Limestone
A sedimentary rock made mostly of the mineral calcite
(calcium carbonate), usually formed from shells of dead
organisms.
LNG
Liquefied natural gas
Lithology
Science of the nature and composition of rocks
Lithosphere
The outer layer of the Earth, made of solid rock, which
includes the crust and uppermost mantle up to 100 km thick.
Log
Records taken during or after the drilling of a well.
London Convention
On the Prevention of Marine Pollution by Dumping of Wastes
and Other Matter, which was adopted at London, Mexico City,
Moscow and Washington on 29 December 1972.
London Protocol
Protocol to the Convention adopted in London on 2 November
1996 but which had not entered into force at the time of
writing.
Low-carbon energy carrier
Fuel that provides low fuel-cycle-wide emissions of CO2, such
as methanol.
Macro-invertebrate
Small creature living in the seabed and subsoil, like
earthworms, snails and beetles.
Madrid Protocol
A protocol to the 11th Antarctic Treaty to provide for
Antarctica’s environmental protection.
Mafic
Term used for silicate minerals, magmas, and rocks, which are
relatively high in the heavier elements.
Magmatic activity
The flow of magma (lava).
Marginal cost
Additional cost that arises from the expansion of activity. For
example, emission reduction by one additional unit.
Maturation
The geological process of changing with time. For example,
the alteration of peat into lignite, then into sub-bituminous and
bituminous coal, and then into anthracite.
Mature sedimentary basins
Geological provinces formed by the deposition of particulate
matter under water when the deposits have matured into
hydrocarbon reserves.
MEA
Mono-ethanolamine
Medium-gravity oil
Oil with a density of between about 850 and 925kg/m3
(between 20 and 30 API).
Membrane
A sheet or block of material that selectively separates the
components of a fluid mixture.
Metamorphic
Of rocks that have been altered by heat or pressure.
Mica
Class of silicate minerals with internal plate structure.
Microseismicity
Small-scale seismic tremors.
Migration
The movement of fluids in reservoir rocks.
Mineral trap
A geological structure in which fluids are retained by the
reaction of the fluid to form a stable mineral.
Miscible displacement
Injection process that introduces miscible gases into the
reservoir, thereby maintaining reservoir pressure and
improving oil displacement.
Mitigation
The process of reducing the impact of any failure.
Monitoring
The process of measuring the quantity of carbon dioxide
stored and its location.
Monte Carlo
A modelling technique in which the statistical properties of
outcomes are tested by random inputs.
Mudstone
A very fine-grained sedimentary rock formed from mud.
MWh
Megawatt-hour
Annex II: Glossary, acronyms and abbreviations 409
National Greenhouse Gas Inventory
An inventory of anthropogenic emissions by sources and
removals by sinks of greenhouse gases prepared by Parties to
the UNFCCC.
Natural analogue
A natural occurrence that mirrors in most essential elements an
intended or actual human activity.
Natural underground trap
A geological structure in which fluids are retained by natural
processes.
Navier-Stokes equations
The general equations describing the flow of fluids.
Near-field
The region close to a signal source.
NGCC
Natural gas combined cycle: natural-gas-fired power plant
with gas and steam turbines.
Non-hazardous waste
Non-harmful substances that have been released or discarded
into the environment.
NPV
Net present value: the value of future cash flows discounted to
the present at a defined rate of interest.
Numerical approximation
Representation of physico-mathematical laws through linear
approximations.
Observation well
A well installed to permit the observation of subsurface
conditions.
OECD
Organization for Economic Co-operation and Development
OSPAR
Convention for the Protection of the Marine Environment of
the North-East Atlantic, which was adopted at Paris on 22
September 1992.
Outcrop
The point at which a particular stratum reaches the earth’s
surface.
Overburden
Rocks and sediments above any particular stratum.
Overpressure
Pressure created in a reservoir that exceeds the pressure
inherent at the reservoir’s depth.
Oxidation
The loss of one or more electrons by an atom, molecule, or
ion.
Oxyfuel combustion
Combustion of a fuel with pure oxygen or a mixture of
oxygen, water and carbon dioxide.
Packer
A device for sealing off a section of a borehole or part of a
borehole.
Partial oxidation
The oxidation of a carbon-containing fuel under conditions
that produce a large fraction of CO and hydrogen.
Partial pressure
The pressure that would be exerted by a particular gas in a
mixture of gases if the other gases were not present.
pCO2 The partial pressure (q.v.) of CO2.
PC
Pulverized coal: usually used in connection with boilers fed
with finely ground coal.
Pejus level
The level in the ocean below which the functioning of animals
deteriorates significantly.
Pelagic
Relating to, or occurring, or living in, or frequenting, the open
ocean.
Perfluorocarbon
Synthetically produced halocarbons containing only carbon
and fluorine atoms. They are characterized by extreme
stability, non-flammability, low toxicity and high global
warming potential.
Permeability
Ability to flow or transmit fluids through a porous solid such
as rock.
Permian
A geological age between 290 and 248 million years ago.
Phytotoxic
Poisonous to plants.
Piezo-electric transducer
Crystals or films that are able to convert mechanical energy in
electrical energy or vice-versa.
410 IPCC Special Report on Carbon dioxide Capture and Storage
Pig
A device that is driven down pipelines to inspect and/or clean
them.
Point source
An emission source that is confined to a single small location
Polygeneration
Production of more than one form of energy, for example
synthetic liquid fuels plus electricity.
Pore space
Space between rock or sediment grains that can contain fluids.
Poroelastic
Elastic behaviour of porous media.
Porosity
Measure for the amount of pore space in a rock.
Post-combustion capture
The capture of carbon dioxide after combustion.
POX
Partial oxidation (q.v.)
Pre-combustion capture
The capture of carbon dioxide following the processing of the
fuel before combustion.
Primary legal source
Legal source not depending on authority given by others.
Probability density function
Function that describes the probability for a series of
parameter values.
Prospectivity
A qualitative assessment of the likelihood that a suitable
storage location is present in a given area based on the
available information
Proven reserve
For oil declared by operator to be economical; for gas about
which a decision has been taken to proceed with development
and production; see Resource.
Province
An area with separate but similar geological formations.
PSA
Pressure swing adsorption: a method of separating gases
using the physical adsorption of one gas at high pressure and
releasing it at low pressure.
Rank
Quality criterion for coal.
Reduction
The gain of one or more electrons by an atom, molecule, or
ion
Reduction commitment
A commitment by a Party to the Kyoto Protocol to meet its
quantified emission limit.
Reforestation
Planting of forests on lands that have previously contained
forests but that have been converted to some other use.
Regional scale
A geological feature that crosses an entire basin.
Remediation
The process of correcting any source of failure.
Renewables
Energy sources that are inherently renewable such as solar
energy, hydropower, wind, and biomass.
Rep. Value
Representative value
Reproductive dysfunction
Inability to reproduce.
Reserve
A resource (q.v.) from which it is generally economic to
produce valuable minerals or hydrocarbons.
Reservoir
A subsurface body of rock with sufficient porosity and
permeability to store and transmit fluids.
Residual saturation
The fraction of the injected CO2 that is trapped in pores by
capillary forces.
Resource
A body of a potentially valuable mineral or hydrocarbon.
Retrofit
A modification of the existing equipment to upgrade and
incorporate changes after installation.
Risk assessment
Part of a risk-management system.
Root anoxia
Lack, or deficiency, of oxygen in root zone.
Root zone
Part of the soil in which plants have their roots.
Annex II: Glossary, acronyms and abbreviations 411
Safe Drinking Water Act
An Act of the US Congress originally passed in 1974. It
regulates, among other things, the possible contamination of
underground water.
Saline formation
Sediment or rock body containing brackish water or brine.
Saline groundwater
Groundwater in which salts are dissolved.
Sandstone
Sand that has turned into a rock due to geological processes.
Saturated zone
Part of the subsurface that is totally saturated with
groundwater.
Scenario
A plausible description of the future based on an internally
consistent set of assumptions about key relationships and
driving forces. Note that scenarios are neither predictions nor
forecasts.
SCR
Selective catalytic reduction
Scrubber
A gas-liquid contacting device for the purification of gases or
capture of a gaseous component.
Seabed
Borderline between the free water and the top of the bottom
sediment.
Seal
An impermeable rock that forms a barrier above and around a
reservoir such that fluids are held in the reservoir.
Secondary recovery
Recovery of oil by artificial means, after natural production
mechanisms like overpressure have ceased.
Sedimentary basin
Natural large-scale depression in the earth’s surface that is
filled with sediments.
Seismic profile
A two-dimensional seismic image of the subsurface.
Seismic technique
Measurement of the properties of rocks by the speed of sound
waves generated artificially or naturally.
Seismicity
The episodic occurrence of natural or man-induced
earthquakes.
Selexol
A commercial physical absorption process to remove CO2
using glycol dimethylethers.
Shale
Clay that has changed into a rock due to geological processes.
Shift convertor
A reactor in which the water-gas shift reaction, CO + H2O =
CO2 + H2, takes place.
Simplex orifice fitting
An apparatus for measuring the flow rate of gases or liquids.
Sink
The natural uptake of CO2 from the atmosphere, typically in
soils, forests or the oceans.
SMR
Steam methane reforming: a catalytic process in which
methane reacts with steam to produce a mixture of H2, CO and
CO2.
SNG
Synthetic natural gas: fuel gas with a high concentration of
methane produced from coal or heavy hydrocarbons.
SOFC
Solid oxide fuel cell: a fuel cell (q.v.) in which the electrolyte
is a solid ceramic composed of calcium- or yttrium-stabilized
zirconium oxides.
Soil gas
Gas contained in the space between soil grains
Solubility trapping
A process in which fluids are retained by dissolution in liquids
naturally present.
Sour gas
Natural gas containing significant quantities of acid gases like
H2S and CO2.
Source
Any process, activity or mechanism that releases a greenhouse
gas, an aerosol, or a precursor thereof into the atmosphere.
Speciation
The determination of the number of species into which a
single species will divide over time.
Spill point
The structurally lowest point in a structural trap (q.v.) that can
retain fluids lighter than background
fluids.
412 IPCC Special Report on Carbon dioxide Capture and Storage
Spoil pile
Heap of waste material derived from mining or processing
operations.
SRES
Special Report on Emissions Scenarios; used as a basis for the
climate projections in the TAR (q.v.).
Stabilization
Relating to the stabilization atmospheric concentrations of
greenhouse gases.
Stable geological formation
A formation (q.v.) that has not recently been disturbed by
tectonic movement.
Steam reforming
A catalytic process in which a hydrocarbon is reacted with
steam to produce a mixture of H2, CO and CO2.
Storage
A process for retaining captured CO2 so that it does not reach
the atmosphere.
Strain gauge
Gauge to determine the deformation of an object subjected to
stress.
Stratigraphic
The order and relative position of strata.
Stratigraphic column
A column showing the sequence of different strata.
Stratigraphic trap
A sealed geological container capable of retaining fluids,
formed by changes in rock type, structure or facies.
Stimulation
The enhancement of the ability to inject fluids into, or recover
fluids from, a well.
Stripper
A gas-liquid contacting device, in which a component is
transferred from liquid phase to the gas phase.
Structural trap
Geological structure capable of retaining hydrocarbons, sealed
structurally by a fault or fold.
Structure
Geological feature produced by the deformation of the Earth’s
crust, such as a fold or a fault; a feature within a rock such as a
fracture; or, more generally, the spatial arrangement of rocks.
Structure contour map
Map showing the contours of geological structures.
Subsoil
Term used in London and OSPAR conventions, meaning the
sediments below the seabed.
Sub-bituminous coal
Coal of a rank between lignite (q.v.) and bituminous (q.v.)
coal.
Sustainable
Of development, that which is sustainable in ecological, social
and economic areas.
Supercritical
At a temperature and pressure above the critical temperature
and pressure of the substance concerned. The critical point
represents the highest temperature and pressure at which the
substance can exist as a vapour and liquid in equilibrium
Syngas
Synthesis gas (q.v.)
Synthesis gas
A gas mixture containing a suitable proportion of CO and H2
for the synthesis of organic compounds or combustion.
Synfuel
Fuel, typically liquid fuel, produced by processing fossil fuel.
Tail gas
Effluent gas at the end of a process.
Tailing
The waste resulting from the extraction of value from ore.
TAR
Third Assessment Report of the Intergovernmental Panel on
Climate Change
TCR
Total capital requirement
Technical Potential
The amount by which it is possible to reduce greenhouse gas
emissions by implementing a technology or practice that has
reached the demonstration phase.
Tectonically active area
Area of the Earth where deformation is presently causing
structural changes.
Tertiary
Geological age about 65 to 2 million years ago.
Tertiary recovery
Oil generated by a third method; the first is by pressure release
or depletion, and the second by oil driven out by the injection
of water.
Annex II: Glossary, acronyms and abbreviations 413
Thermocline
The ocean phenomenon characterized by a sharp change in
temperature with depth.
Thermohaline
The vertical overturning of water masses due to seasonal
heating, evaporation, and cooling.
Top-down model
A model based on applying macro-economic theory and
econometric techniques to historical data about consumption,
prices, etc.
Toxemia
Poisoning, usually of the blood.
Toxicology
Scientific study of poisons and their effects.
Tracer
A chemical compound or isotope added in small quantities to
trace flow patterns.
Transaction cost
The full cost of transferring property or rights between parties.
Trap
A geological structure that physically retains fluids that are
lighter than the background fluids, e.g. an inverted cup.
Ultramafic rocks
An igneous rock consisting almost entirely of iron- and
magnesium-rich minerals with a silica content typically less
than 45%.
UNCLOS
United Nations Convention on the Law of the Sea, which was
adopted at Montego Bay on 10 December 1982.
Unconformity
A geological surface separating older from younger rocks and
representing a gap in the geological record.
Under-saturated
A solution that could contain more solute than is presently
dissolved in it.
UNFCCC
United Nations Framework Convention on Climate Change,
which was adopted at New York on 9 May 1992.
Unminable
Extremely unlikely to be mined under current or foreseeable
economic conditions
Updip
Inclining upwards following a structural contour of strata.
Upper ocean
The ocean above 1000m depth.
Vacuum residue
The heavy hydrocarbon mixture that is produced at the bottom
of vacuum distillation columns in oil refineries.
Vadose zone
Region from the water table to the ground surface, also called
the unsaturated zone because it is partially water-saturated.
Validation
In the context of CDM (q.v.), the process of the independent
evaluation of a project by a designated operational entity on
the basis of set requirements.
Ventilation
The exchange of gases dissolved in sea-water with the
atmosphere, or gas exchange between an animal and the
environment.
Verification
The proving, to a standard still to be decided, of the results
of monitoring (q.v.). In the context of CDM, the independent
review by a designated operational entity of monitored
reductions in anthropogenic emissions.
Viscous fingering
Flow phenomenon arising from the flow of two largely
immiscible fluids through a porous medium.
Well
Manmade hole drilled into the earth to produce liquids or
gases, or to allow the injection of fluids.
Well with multiple completions
Well drilled with multiple branching holes and more than one
hole being made ready for use.
Well-bore annulus
The annulus between the rock and the well casing.
Wellhead pressure
Pressure developed on surface at the top of the well.
Wettability
Surface with properties allowing water to contact the surface
intimately.
Zero-carbon energy carrier
Carbon-free energy carrier, typically electricity or hydrogen.Annexes


AI Coordinating Editor: J.B. Robin Matthews (France/UK) Editorial Team: Mustafa Babiker (Sudan), Heleen de Coninck (Netherlands/EU), Sarah Connors (France/UK), Renée van Diemen (UK/Netherlands), Riyanti Djalante (Japan/Indonesia), Kristie L. Ebi (USA), Neville Ellis (Australia), Andreas Fischlin (Switzerland), Tania Guillén Bolaños (Germany/Nicaragua), Kiane de Kleijne (Netherlands/EU), Valérie Masson-Delmotte (France), Richard Millar (UK), Elvira S. Poloczanska (Germany/UK), Hans-Otto Pörtner (Germany), Andy Reisinger (New Zealand), Joeri Rogelj (Austria/Belgium), Sonia I. Seneviratne (Switzerland), Chandni Singh (India), Petra Tschakert (Australia/Austria), Nora M. Weyer (Germany) Notes: Note that subterms are in italics beneath main terms. This glossary defines some specific terms as the Lead Authors intend them to be interpreted in the context of this report. Blue, italicized words indicate that the term is defined in the Glossary. This annex should be cited as: IPCC, 2018: Annex I: Glossary [Matthews, J.B.R. (ed.)]. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press Annex I: Glossary


.5°C pathway See Pathways. .5°C warmer worlds Projected worlds in which global warming has reached and, unless otherwise indicated, been limited to 1.5°C above pre-industrial levels. There is no single 1.5°C warmer world, and projections of 1.5°C warmer worlds look different depending on whether it is considered on a near-term transient trajectory or at climate equilibrium after several millennia, and, in both cases, if it occurs with or without overshoot. Within the 21st century, several aspects play a role for the assessment of risk and potential impacts in 1.5°C warmer worlds: the possible occurrence, magnitude and duration of an overshoot; the way in which emissions reductions are achieved; the ways in which policies might be able to influence the resilience of human and natural systems; and the nature of the regional and sub-regional risks. Beyond the 21st century, several elements of the climate system would continue to change even if the global mean temperatures remain stable, including further increases of sea level. Agenda for Sustainable Development A UN resolution in September 2015 adopting a plan of action for people, planet and prosperity in a new global development framework anchored in 17 Sustainable Development Goals (UN, 2015). See also Sustainable Development Goals (SDGs). Acceptability of policy or system change The extent to which a policy or system change is evaluated unfavourably or favourably, or rejected or supported, by members of the general public (public acceptability) or politicians or governments (political acceptability). Acceptability may vary from totally unacceptable/fully rejected to totally acceptable/fully supported; individuals may differ in how acceptable policies or system changes are believed to be. Adaptability See Adaptive capacity. Adaptation In human systems, the process of adjustment to actual or expected climate and its effects, in order to moderate harm or exploit beneficial opportunities. In natural systems, the process of adjustment to actual climate and its effects; human intervention may facilitate adjustment to expected climate and its effects. Incremental adaptation Adaptation that maintains the essence and integrity of a system or process at a given scale. In some cases, incremental adaptation can accrue to result in transformational adaptation (Termeer et al., 2017; Tàbara et al., 2018). Transformational adaptation Adaptation that changes the fundamental attributes of a socioecological system in anticipation of climate change and its impacts. Adaptation limits The point at which an actor’s objectives (or system needs) cannot be secured from intolerable risks through adaptive actions. • Hard adaptation limit: No adaptive actions are possible to avoid intolerable risks. • Soft adaptation limit: Options are currently not available to avoid intolerable risks through adaptive action. See also Adaptation options, Adaptive capacity and Maladaptive actions (Maladaptation). Adaptation behaviour See Human behaviour. Adaptation limits See Adaptation. Adaptation options The array of strategies and measures that are available and appropriate for addressing adaptation. They include a wide range of actions that can be categorized as structural, institutional, ecological or behavioural. See also Adaptation, Adaptive capacity and Maladaptive actions (Maladaptation). Adaptation pathways See Pathways. Adaptive capacity The ability of systems, institutions, humans and other organisms to adjust to potential damage, to take advantage of opportunities, or to respond to consequences. This glossary entry builds from definitions used in previous IPCC reports and the Millennium Ecosystem Assessment (MEA, 2005). See also Adaptation, Adaptation options and Maladaptive actions (Maladaptation). Adaptive governance See Governance. Aerosol A suspension of airborne solid or liquid particles, with a typical size between a few nanometres and 10 μm that reside in the atmosphere for at least several hours. The term aerosol, which includes both the particles and the suspending gas, is often used in this report in its plural form to mean aerosol particles. Aerosols may be of either natural or anthropogenic origin. Aerosols may influence climate in several ways: through both interactions that scatter and/or absorb radiation and through interactions with cloud microphysics and other cloud properties, or upon deposition on snow- or ice-covered surfaces thereby altering their albedo and contributing to climate feedback. Atmospheric aerosols, whether natural or anthropogenic, originate from two different pathways: emissions of primary particulate matter (PM), and formation of secondary PM from gaseous precursors. The bulk of aerosols are of natural origin. Some scientists use group labels that refer to the chemical composition, namely: sea salt, organic carbon, black carbon (BC), mineral species (mainly desert dust), sulphate, nitrate, and ammonium. These labels are, however, imperfect as aerosols combine particles to create complex mixtures. See also Short-lived climate forcers (SLCF) and Black carbon (BC). Afforestation Planting of new forests on lands that historically have not contained forests. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000), information provided by the United Nations Framework Convention on Climate Change (UNFCCC, 2013) and the report on Definitions and Methodological Options to Inventory Emissions from Direct Humaninduced Degradation of Forests and Devegetation of Other Vegetation Types (IPCC, 2003). See also Reforestation, Deforestation, and Reducing Emissions from Deforestation and Forest Degradation (REDD+). Agreement In this report, the degree of agreement within the scientific body of knowledge on a particular finding is assessed based on multiple lines of evidence (e.g., mechanistic understanding, theory, data, models, expert judgement) and expressed qualitatively (Mastrandrea et al., 2010). See also Evidence, Confidence, Likelihood and Uncertainty. Air pollution Degradation of air quality with negative effects on human health or the natural or built environment due to the introduction, by natural processes or human activity, into the atmosphere of substances (gases, aerosols) which have a direct (primary pollutants) or indirect (secondary pollutants) harmful effect. See also Aerosol and Short-lived climate forcers (SLCF). Albedo The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. Snow-covered surfaces have a high albedo, the surface albedo of soils ranges from high to low, and vegetation-covered surfaces and the oceans have a low albedo. The Earth’s planetary albedo changes mainly through varying cloudiness and changes in snow, ice, leaf area and land cover. Ambient persuasive technology Technological systems and environments that are designed to change human cognitive processing,


attitudes and behaviours without the need for the user’s conscious attention. Anomaly The deviation of a variable from its value averaged over a reference period. Anthropocene The ‘Anthropocene’ is a proposed new geological epoch resulting from significant human-driven changes to the structure and functioning of the Earth System, including the climate system. Originally proposed in the Earth System science community in 2000, the proposed new epoch is undergoing a formalization process within the geological community based on the stratigraphic evidence that human activities have changed the Earth System to the extent of forming geological deposits with a signature that is distinct from those of the Holocene, and which will remain in the geological record. Both the stratigraphic and Earth System approaches to defining the Anthropocene consider the mid-20th Century to be the most appropriate starting date, although others have been proposed and continue to be discussed. The Anthropocene concept has been taken up by a diversity of disciplines and the public to denote the substantive influence humans have had on the state, dynamics and future of the Earth System. See also Holocene. Anthropogenic Resulting from or produced by human activities. See also Anthropogenic emissions and Anthropogenic removals. Anthropogenic emissions Emissions of greenhouse gases (GHGs), precursors of GHGs and aerosols caused by human activities. These activities include the burning of fossil fuels, deforestation, land use and land-use changes (LULUC), livestock production, fertilisation, waste management and industrial processes. See also Anthropogenic and Anthropogenic removals. Anthropogenic removals Anthropogenic removals refer to the withdrawal of GHGs from the atmosphere as a result of deliberate human activities. These include enhancing biological sinks of CO2 and using chemical engineering to achieve long-term removal and storage. Carbon capture and storage (CCS) from industrial and energy-related sources, which alone does not remove CO2 in the atmosphere, can reduce atmospheric CO2 if it is combined with bioenergy production (BECCS). See also Anthropogenic emissions, Bioenergy with carbon dioxide capture and storage (BECCS) and Carbon dioxide capture and storage (CCS). Artificial intelligence (AI) Computer systems able to perform tasks normally requiring human intelligence, such as visual perception and speech recognition. Atmosphere The gaseous envelope surrounding the earth, divided into five layers – the troposphere which contains half of the Earth’s atmosphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere, which is the outer limit of the atmosphere. The dry atmosphere consists almost entirely of nitrogen (78.1% volume mixing ratio) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93 % volume mixing ratio), helium and radiatively active greenhouse gases (GHGs) such as carbon dioxide (CO2) (0.04% volume mixing ratio) and ozone (O3). In addition, the atmosphere contains the GHG water vapour (H2O), whose amounts are highly variable but typically around 1% volume mixing ratio. The atmosphere also contains clouds and aerosols. See also Troposphere, Stratosphere, Greenhouse gas (GHG) and Hydrological cycle. Atmosphere–ocean general circulation model (AOGCM) See Climate model. Attribution See Detection and attribution. Baseline scenario In much of the literature the term is also synonymous with the term business-as-usual (BAU) scenario, although the term BAU has fallen out of favour because the idea of business as usual in century-long socio-economic projections is hard to fathom. In the context of transformation pathways, the term baseline scenarios refers to scenarios that are based on the assumption that no mitigation policies or measures will be implemented beyond those that are already in force and/or are legislated or planned to be adopted. Baseline scenarios are not intended to be predictions of the future, but rather counterfactual constructions that can serve to highlight the level of emissions that would occur without further policy effort. Typically, baseline scenarios are then compared to mitigation scenarios that are constructed to meet different goals for greenhouse gas (GHG) emissions, atmospheric concentrations or temperature change. The term baseline scenario is often used interchangeably with reference scenario and no policy scenario. See also Emission scenario and Mitigation scenario. Battery electric vehicle (BEV) See Electric vehicle (EV). Biochar Stable, carbon-rich material produced by heating biomass in an oxygen-limited environment. Biochar may be added to soils to improve soil functions and to reduce greenhouse gas emissions from biomass and soils, and for carbon sequestration. This definition builds from IBI (2018). Biodiversity Biological diversity means the variability among living organisms from all sources, including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems (UN, 1992). Bioenergy Energy derived from any form of biomass or its metabolic by-products. See also Biomass and Biofuel. Bioenergy with carbon dioxide capture and storage (BECCS) Carbon dioxide capture and storage (CCS) technology applied to a bioenergy facility. Note that depending on the total emissions of the BECCS supply chain, carbon dioxide (CO2) can be removed from the atmosphere. See also Bioenergy and Carbon dioxide capture and storage (CCS). Biofuel A fuel, generally in liquid form, produced from biomass. Biofuels currently include bioethanol from sugarcane or maize, biodiesel from canola or soybeans, and black liquor from the paper-manufacturing process. See also Biomass and Bioenergy. Biomass Living or recently dead organic material. See also Bioenergy and Biofuel. Biophilic urbanism Designing cities with green roofs, green walls and green balconies to bring nature into the densest parts of cities in order to provide green infrastructure and human health benefits. See also Green infrastructure. Black carbon (BC) Operationally defined aerosol species based on measurement of light absorption and chemical reactivity and/or thermal stability. It is sometimes referred to as soot. BC is mostly formed by the incomplete combustion of fossil fuels, biofuels and biomass but it also occurs naturally. It stays in the atmosphere only for days or weeks. It is the most strongly light-absorbing component of particulate matter (PM) and has a warming effect by absorbing heat into the atmosphere and reducing the albedo when deposited on snow or ice. See also Aerosol. Blue carbon Blue carbon is the carbon captured by living organisms in coastal (e.g., mangroves, salt marshes, seagrasses) and marine ecosystems, and stored in biomass and sediments. Burden sharing (also referred to as Effort sharing) In the context of mitigation, burden sharing refers to sharing the effort of reducing the sources or enhancing the sinks of greenhouse gases (GHGs)


from historical or projected levels, usually allocated by some criteria, as well as sharing the cost burden across countries. Business as usual (BAU) See Baseline scenario. Carbon budget This term refers to three concepts in the literature: (1) an assessment of carbon cycle sources and sinks on a global level, through the synthesis of evidence for fossil fuel and cement emissions, land-use change emissions, ocean and land CO2 sinks, and the resulting atmospheric CO2 growth rate. This is referred to as the global carbon budget; (2) the estimated cumulative amount of global carbon dioxide emissions that that is estimated to limit global surface temperature to a given level above a reference period, taking into account global surface temperature contributions of other GHGs and climate forcers; (3) the distribution of the carbon budget defined under (2) to the regional, national, or sub-national level based on considerations of equity, costs or efficiency. See also Remaining carbon budget. Carbon cycle The term used to describe the flow of carbon (in various forms, e.g., as carbon dioxide (CO2), carbon in biomass, and carbon dissolved in the ocean as carbonate and bicarbonate) through the atmosphere, hydrosphere, terrestrial and marine biosphere and lithosphere. In this report, the reference unit for the global carbon cycle is GtCO2 or GtC (Gigatonne of carbon = 1 GtC = 1015 grams of carbon. This corresponds to 3.667 GtCO2). Carbon dioxide (CO2) A naturally occurring gas, CO2 is also a by-product of burning fossil fuels (such as oil, gas and coal), of burning biomass, of land-use changes (LUC) and of industrial processes (e.g., cement production). It is the principal anthropogenic greenhouse gas (GHG) that affects the Earth’s radiative balance. It is the reference gas against which other GHGs are measured and therefore has a global warming potential (GWP) of 1. See also Greenhouse gas (GHG). Carbon dioxide capture and storage (CCS) A process in which a relatively pure stream of carbon dioxide (CO2) from industrial and energy-related sources is separated (captured), conditioned, compressed and transported to a storage location for long-term isolation from the atmosphere. Sometimes referred to as Carbon capture and storage. See also Carbon dioxide capture and utilisation (CCU), Bioenergy with carbon dioxide capture and storage (BECCS) and Uptake. Carbon dioxide capture and utilisation (CCU) A process in which CO2 is captured and then used to produce a new product. If the CO2 is stored in a product for a climate-relevant time horizon, this is referred to as carbon dioxide capture, utilisation and storage (CCUS). Only then, and only combined with CO2 recently removed from the atmosphere, can CCUS lead to carbon dioxide removal. CCU is sometimes referred to as carbon dioxide capture and use. See also Carbon dioxide capture and storage (CCS). Carbon dioxide capture, utilisation and storage (CCUS) See Carbon dioxide capture and utilisation (CCU). Carbon dioxide removal (CDR) Anthropogenic activities removing CO2 from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological or geochemical sinks and direct air capture and storage, but excludes natural CO2 uptake not directly caused by human activities. See also Mitigation (of climate change), Greenhouse gas removal (GGR), Negative emissions, Direct air carbon dioxide capture and storage (DACCS) and Sink. Carbon intensity The amount of emissions of carbon dioxide (CO2) released per unit of another variable such as gross domestic product (GDP), output energy use or transport. Carbon neutrality See Net zero CO2 emissions. Carbon price The price for avoided or released carbon dioxide (CO2) or CO2-equivalent emissions. This may refer to the rate of a carbon tax, or the price of emission permits. In many models that are used to assess the economic costs of mitigation, carbon prices are used as a proxy to represent the level of effort in mitigation policies. Carbon sequestration The process of storing carbon in a carbon pool. See also Blue carbon, Carbon dioxide capture and storage (CCS), Uptake and Sink. Carbon sink See Sink. Clean Development Mechanism (CDM) A mechanism defined under Article 12 of the Kyoto Protocol through which investors (governments or companies) from developed (Annex B) countries may finance greenhouse gas (GHG) emission reduction or removal projects in developing countries (Non-Annex B), and receive Certified Emission Reduction Units (CERs) for doing so. The CERs can be credited towards the commitments of the respective developed countries. The CDM is intended to facilitate the two objectives of promoting sustainable development (SD) in developing countries and of helping industrialised countries to reach their emissions commitments in a cost-effective way. Climate Climate in a narrow sense is usually defined as the average weather, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period for averaging these variables is 30 years, as defined by the World Meteorological Organization. The relevant quantities are most often surface variables such as temperature, precipitation and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. Climate change Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use. Note that the Framework Convention on Climate Change (UNFCCC), in its Article , defines climate change as: ‘a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.’ The UNFCCC thus makes a distinction between climate change attributable to human activities altering the atmospheric composition and climate variability attributable to natural causes. See also Climate variability, Global warming, Ocean acidification (OA) and Detection and attribution. Climate change commitment Climate change commitment is defined as the unavoidable future climate change resulting from inertia in the geophysical and socio-economic systems. Different types of climate change commitment are discussed in the literature (see subterms). Climate change commitment is usually quantified in terms of the further change in temperature, but it includes other future changes, for example in the hydrological cycle, in extreme weather events, in extreme climate events, and in sea level. Constant composition commitment The constant composition commitment is the remaining climate change that would result if atmospheric composition, and hence radiative forcing, were held fixed at a given value. It results from the thermal inertia of the ocean and slow processes in the cryosphere and land surface.


Constant emissions commitment The constant emissions commitment is the committed climate change that would result from keeping anthropogenic emissions constant. Zero emissions commitment The zero emissions commitment is the climate change commitment that would result from setting anthropogenic emissions to zero. It is determined by both inertia in physical climate system components (ocean, cryosphere, land surface) and carbon cycle inertia. Feasible scenario commitment The feasible scenario commitment is the climate change that corresponds to the lowest emission scenario judged feasible. Infrastructure commitment The infrastructure commitment is the climate change that would result if existing greenhouse gas and aerosol emitting infrastructure were used until the end of its expected lifetime. Climate-compatible development (CCD) A form of development building on climate strategies that embrace development goals and development strategies that integrate climate risk management, adaptation and mitigation. This definition builds from Mitchell and Maxwell (2010). Climate extreme (extreme weather or climate event) The occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends of the range of observed values of the variable. For simplicity, both extreme weather events and extreme climate events are referred to collectively as ‘climate extremes’. See also Extreme weather event. Climate feedback An interaction in which a perturbation in one climate quantity causes a change in a second and the change in the second quantity ultimately leads to an additional change in the first. A negative feedback is one in which the initial perturbation is weakened by the changes it causes; a positive feedback is one in which the initial perturbation is enhanced. The initial perturbation can either be externally forced or arise as part of internal variability. Climate governance See Governance. Climate justice See Justice. Climate model A numerical representation of the climate system based on the physical, chemical and biological properties of its components, their interactions and feedback processes, and accounting for some of its known properties. The climate system can be represented by models of varying complexity; that is, for any one component or combination of components a spectrum or hierarchy of models can be identified, differing in such aspects as the number of spatial dimensions, the extent to which physical, chemical or biological processes are explicitly represented, or the level at which empirical parametrizations are involved. There is an evolution towards more complex models with interactive chemistry and biology. Climate models are applied as a research tool to study and simulate the climate and for operational purposes, including monthly, seasonal and interannual climate predictions. See also Earth system model (ESM). Climate neutrality Concept of a state in which human activities result in no net effect on the climate system. Achieving such a state would require balancing of residual emissions with emission (carbon dioxide) removal as well as accounting for regional or local biogeophysical effects of human activities that, for example, affect surface albedo or local climate. See also Net zero CO2 emissions. Climate projection A climate projection is the simulated response of the climate system to a scenario of future emission or concentration of greenhouse gases (GHGs) and aerosols, generally derived using climate models. Climate projections are distinguished from climate predictions by their dependence on the emission/concentration/radiative forcing scenario used, which is in turn based on assumptions concerning, for example, future socioeconomic and technological developments that may or may not be realized. Climate-resilient development pathways (CRDPs) Trajectories that strengthen sustainable development and efforts to eradicate poverty and reduce inequalities while promoting fair and cross-scalar adaptation to and resilience in a changing climate. They raise the ethics, equity and feasibility aspects of the deep societal transformation needed to drastically reduce emissions to limit global warming (e.g., to 1.5°C) and achieve desirable and liveable futures and well-being for all. Climate-resilient pathways Iterative processes for managing change within complex systems in order to reduce disruptions and enhance opportunities associated with climate change. See also Development pathways (under Pathways), Transformation pathways (under Pathways), and Climate-resilient development pathways (CRDPs). Climate sensitivity Climate sensitivity refers to the change in the annual global mean surface temperature in response to a change in the atmospheric CO2 concentration or other radiative forcing. Equilibrium climate sensitivity Refers to the equilibrium (steady state) change in the annual global mean surface temperature following a doubling of the atmospheric carbon dioxide (CO2) concentration. As a true equilibrium is challenging to define in climate models with dynamic oceans, the equilibrium climate sensitivity is often estimated through experiments in AOGCMs where CO2 levels are either quadrupled or doubled from pre-industrial levels and which are integrated for 100-200 years. The climate sensitivity parameter (units: °C (W m–2)–1) refers to the equilibrium change in the annual global mean surface temperature following a unit change in radiative forcing. Effective climate sensitivity An estimate of the global mean surface temperature response to a doubling of the atmospheric carbon dioxide (CO2) concentration that is evaluated from model output or observations for evolving non-equilibrium conditions. It is a measure of the strengths of the climate feedbacks at a particular time and may vary with forcing history and climate state, and therefore may differ from equilibrium climate sensitivity. Transient climate response The change in the global mean surface temperature, averaged over a -year period, centered at the time of atmospheric CO2 doubling, in a climate model simulation in which CO2 increases at 1% yr-1 from preindustrial. It is a measure of the strength of climate feedbacks and the timescale of ocean heat uptake. Climate services Climate services refers to information and products that enhance users’ knowledge and understanding about the impacts of climate change and/or climate variability so as to aid decision-making of individuals and organizations and enable preparedness and early climate change action. Products can include climate data products. Climate-smart agriculture (CSA) Climate-smart agriculture (CSA) is an approach that helps to guide actions needed to transform and reorient agricultural systems to effectively support development and ensure food security in a changing climate. CSA aims to tackle three main objectives: sustainably increasing agricultural productivity and incomes, adapting and building resilience to climate change, and reducing and/or removing greenhouse gas emissions, where possible (FAO, 2018). Climate system The climate system is the highly complex system consisting of five major components: the atmosphere, the hydrosphere,


the cryosphere, the lithosphere and the biosphere and the interactions between them. The climate system evolves in time under the influence of its own internal dynamics and because of external forcings such as volcanic eruptions, solar variations and anthropogenic forcings such as the changing composition of the atmosphere and land-use change. Climate target Climate target refers to a temperature limit, concentration level, or emissions reduction goal used towards the aim of avoiding dangerous anthropogenic interference with the climate system. For example, national climate targets may aim to reduce greenhouse gas emissions by a certain amount over a given time horizon, for example those under the Kyoto Protocol. Climate variability Climate variability refers to variations in the mean state and other statistics (such as standard deviations, the occurrence of extremes, etc.) of the climate on all spatial and temporal scales beyond that of individual weather events. Variability may be due to natural internal processes within the climate system (internal variability), or to variations in natural or anthropogenic external forcing (external variability). See also Climate change. CO2 equivalent (CO2-eq) emission The amount of carbon dioxide (CO2) emission that would cause the same integrated radiative forcing or temperature change, over a given time horizon, as an emitted amount of a greenhouse gas (GHG) or a mixture of GHGs. There are a number of ways to compute such equivalent emissions and choose appropriate time horizons. Most typically, the CO2-equivalent emission is obtained by multiplying the emission of a GHG by its global warming potential (GWP) for a 100-year time horizon. For a mix of GHGs it is obtained by summing the CO2-equivalent emissions of each gas. CO2-equivalent emission is a common scale for comparing emissions of different GHGs but does not imply equivalence of the corresponding climate change responses. There is generally no connection between CO2-equivalent emissions and resulting CO2-equivalent concentrations. Co-benefits The positive effects that a policy or measure aimed at one objective might have on other objectives, thereby increasing the total benefits for society or the environment. Co-benefits are often subject to uncertainty and depend on local circumstances and implementation practices, among other factors. Co-benefits are also referred to as ancillary benefits. Common but Differentiated Responsibilities and Respective Capabilities (CBDR-RC) Common but Differentiated Responsibilities and Respective Capabilities (CBDR–RC) is a key principle in the United Nations Framework Convention on Climate Change (UNFCCC) that recognises the different capabilities and differing responsibilities of individual countries in tacking climate change. The principle of CBDR– RC is embedded in the 1992 UNFCCC treaty. The convention states: “… the global nature of climate change calls for the widest possible cooperation by all countries and their participation in an effective and appropriate international response, in accordance with their common but differentiated responsibilities and respective capabilities and their social and economic conditions.” Since then the CBDR-RC principle has guided the UN climate negotiations. Conference of the Parties (COP) The supreme body of UN conventions, such as the United Nations Framework Convention on Climate Change (UNFCCC), comprising parties with a right to vote that have ratified or acceded to the convention. See also United Nations Framework Convention on Climate Change (UNFCCC). Confidence The robustness of a finding based on the type, amount, quality and consistency of evidence (e.g., mechanistic understanding, theory, data, models, expert judgment) and on the degree of agreement across multiple lines of evidence. In this report, confidence is expressed qualitatively (Mastrandrea et al., 2010). See Section 1.6 for the list of confidence levels used. See also Agreement, Evidence, Likelihood and Uncertainty. Conservation agriculture A coherent group of agronomic and soil management practices that reduce the disruption of soil structure and biota. Constant composition commitment See Climate change commitment. Constant emissions commitment See Climate change commitment. Coping capacity The ability of people, institutions, organizations, and systems, using available skills, values, beliefs, resources, and opportunities, to address, manage, and overcome adverse conditions in the short to medium term. This glossary entry builds from the definition used in UNISDR (2009) and IPCC (2012a). See also Resilience. Cost–benefit analysis Monetary assessment of all negative and positive impacts associated with a given action. Cost–benefit analysis enables comparison of different interventions, investments or strategies and reveals how a given investment or policy effort pays off for a particular person, company or country. Cost–benefit analyses representing society’s point of view are important for climate change decision-making, but there are difficulties in aggregating costs and benefits across different actors and across timescales. See also Discounting. Cost-effectiveness A measure of the cost at which policy goal or outcome is achieved. The lower the cost the greater the cost-effectiveness. Coupled Model Intercomparison Project (CMIP) The Coupled Model Intercomparison Project (CMIP) is a climate modelling activity from the World Climate Research Programme (WCRP) which coordinates and archives climate model simulations based on shared model inputs by modelling groups from around the world. The CMIP3 multimodel data set includes projections using SRES scenarios. The CMIP5 data set includes projections using the Representative Concentration Pathways (RCPs). The CMIP6 phase involves a suite of common model experiments as well as an ensemble of CMIP-endorsed model intercomparison projects (MIPs). Cumulative emissions The total amount of emissions released over a specified period of time. See also Carbon budget, and Transient climate response to cumulative CO2 emissions (TCRE). Decarbonization The process by which countries, individuals or other entities aim to achieve zero fossil carbon existence. Typically refers to a reduction of the carbon emissions associated with electricity, industry and transport. Decoupling Decoupling (in relation to climate change) is where economic growth is no longer strongly associated with consumption of fossil fuels. Relative decoupling is where both grow but at different rates. Absolute decoupling is where economic growth happens but fossil fuels decline. Deforestation Conversion of forest to non-forest. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000). See also information provided by the United Nations Framework Convention on Climate Change (UNFCCC, ) and the report on Definitions and Methodological Options to Inventory Emissions from Direct Human-induced Degradation of Forests and Devegetation of Other Vegetation Types (IPCC, 2003). See also Afforestation, Reforestation and Reducing Emissions from Deforestation and Forest Degradation (REDD+). Deliberative governance See Governance.


Demand- and supply-side measures Demand-side measures Policies and programmes for influencing the demand for goods and/ or services. In the energy sector, demand-side management aims at reducing the demand for electricity and other forms of energy required to deliver energy services. Supply-side measures Policies and programmes for influencing how a certain demand for goods and/or services is met. In the energy sector, for example, supplyside mitigation measures aim at reducing the amount of greenhouse gas emissions emitted per unit of energy produced. See also Mitigation measures. Demand-side measures See Demand- and supply-side measures. Detection See Detection and attribution. Detection and attribution Detection of change is defined as the process of demonstrating that climate or a system affected by climate has changed in some defined statistical sense, without providing a reason for that change. An identified change is detected in observations if its likelihood of occurrence by chance due to internal variability alone is determined to be small, for example, <10%. Attribution is defined as the process of evaluating the relative contributions of multiple causal factors to a change or event with a formal assessment of confidence. Development pathways See Pathways. Direct air carbon dioxide capture and storage (DACCS) Chemical process by which CO2 is captured directly from the ambient air, with subsequent storage. Also known as direct air capture and storage (DACS). Disaster Severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting with vulnerable social conditions, leading to widespread adverse human, material, economic or environmental effects that require immediate emergency response to satisfy critical human needs and that may require external support for recovery. See also Hazard and Vulnerability. Disaster risk management (DRM) Processes for designing, implementing, and evaluating strategies, policies, and measures to improve the understanding of disaster risk, foster disaster risk reduction and transfer, and promote continuous improvement in disaster preparedness, response, and recovery practices, with the explicit purpose of increasing human security, well-being, quality of life, and sustainable development. Discount rate See Discounting. Discounting A mathematical operation that aims to make monetary (or other) amounts received or expended at different times (years) comparable across time. The discounter uses a fixed or possibly timevarying discount rate from year to year that makes future value worth less today (if the discount rate is positive). The choice of discount rate(s) is debated as it is a judgement based on hidden and/or explicit values. (Internal) Displacement Internal displacement refers to the forced movement of people within the country they live in. Internally displaced persons (IDPs) are ‘Persons or groups of persons who have been forced or obliged to flee or to leave their homes or places of habitual residence, in particular as a result of or in order to avoid the effects of armed conflict, situations of generalized violence, violations of human rights or natural or human-made disasters, and who have not crossed an internationally recognized State border.’ (UN, 1998). See also Migration. Disruptive innovation Disruptive innovation is demand-led technological change that leads to significant system change and is characterized by strong exponential growth. Distributive equity See Equity. Distributive justice See Justice. Double dividend The extent to which revenues generated by policy instruments, such as carbon taxes or auctioned (tradeable) emission permits can (1) contribute to mitigation and (2) offset part of the potential welfare losses of climate policies through recycling the revenue in the economy by reducing other distortionary taxes. Downscaling Downscaling is a method that derives local- to regional-scale (up to 100 km) information from larger-scale models or data analyses. Two main methods exist: dynamical downscaling and empirical/statistical downscaling. The dynamical method uses the output of regional climate models, global models with variable spatial resolution, or high-resolution global models. The empirical/statistical methods are based on observations and develop statistical relationships that link the large-scale atmospheric variables with local/regional climate variables. In all cases, the quality of the driving model remains an important limitation on quality of the downscaled information. The two methods can be combined, e.g., applying empirical/statistical downscaling to the output of a regional climate model, consisting of a dynamical downscaling of a global climate model. Drought A period of abnormally dry weather long enough to cause a serious hydrological imbalance. Drought is a relative term, therefore any discussion in terms of precipitation deficit must refer to the particular precipitation-related activity that is under discussion. For example, shortage of precipitation during the growing season impinges on crop production or ecosystem function in general (due to soil moisture drought, also termed agricultural drought), and during the runoff and percolation season primarily affects water supplies (hydrological drought). Storage changes in soil moisture and groundwater are also affected by increases in actual evapotranspiration in addition to reductions in precipitation. A period with an abnormal precipitation deficit is defined as a meteorological drought. See also Soil moisture. Megadrought A megadrought is a very lengthy and pervasive drought, lasting much longer than normal, usually a decade or more. Early warning systems (EWS) The set of technical, financial and institutional capacities needed to generate and disseminate timely and meaningful warning information to enable individuals, communities and organizations threatened by a hazard to prepare to act promptly and appropriately to reduce the possibility of harm or loss. Dependent upon context, EWS may draw upon scientific and/or Indigenous knowledge. EWS are also considered for ecological applications e.g., conservation, where the organization itself is not threatened by hazard but the ecosystem under conservation is (an example is coral bleaching alerts), in agriculture (for example, warnings of ground frost, hailstorms) and in fisheries (storm and tsunami warnings). This glossary entry builds from the definitions used in UNISDR (2009) and IPCC (2012a). Earth system feedbacks See Climate feedback. Earth system model (ESM) A coupled atmosphere–ocean general circulation model in which a representation of the carbon cycle is included, allowing for interactive calculation of atmospheric CO2 or compatible emissions. Additional components (e.g., atmospheric chemistry, ice sheets, dynamic vegetation, nitrogen cycle, but also urban or crop models) may be included. See also Climate model.


Ecosystem An ecosystem is a functional unit consisting of living organisms, their non-living environment and the interactions within and between them. The components included in a given ecosystem and its spatial boundaries depend on the purpose for which the ecosystem is defined: in some cases they are relatively sharp, while in others they are diffuse. Ecosystem boundaries can change over time. Ecosystems are nested within other ecosystems and their scale can range from very small to the entire biosphere. In the current era, most ecosystems either contain people as key organisms, or are influenced by the effects of human activities in their environment. See also Ecosystem services. Ecosystem services Ecological processes or functions having monetary or non-monetary value to individuals or society at large. These are frequently classified as (1) supporting services such as productivity or biodiversity maintenance, (2) provisioning services such as food or fibre, (3) regulating services such as climate regulation or carbon sequestration, and (4) cultural services such as tourism or spiritual and aesthetic appreciation. Effective climate sensitivity See Climate sensitivity. Effective radiative forcing See Radiative forcing. El Niño-Southern Oscillation (ENSO) The term El Niño was initially used to describe a warm-water current that periodically flows along the coast of Ecuador and Peru, disrupting the local fishery. It has since become identified with warming of the tropical Pacific Ocean east of the dateline. This oceanic event is associated with a fluctuation of a global-scale tropical and subtropical surface pressure pattern called the Southern Oscillation. This coupled atmosphere–ocean phenomenon, with preferred time scales of two to about seven years, is known as the El Niño-Southern Oscillation (ENSO). It is often measured by the surface pressure anomaly difference between Tahiti and Darwin and/or the sea surface temperatures in the central and eastern equatorial Pacific. During an ENSO event, the prevailing trade winds weaken, reducing upwelling and altering ocean currents such that the sea surface temperatures warm, further weakening the trade winds. This phenomenon has a great impact on the wind, sea surface temperature and precipitation patterns in the tropical Pacific. It has climatic effects throughout the Pacific region and in many other parts of the world, through global teleconnections. The cold phase of ENSO is called La Niña. Electric vehicle (EV) A vehicle whose propulsion is powered fully or mostly by electricity. Battery electric vehicle (BEV) A vehicle whose propulsion is entirely electric without any internal combustion engine. Plug-in hybrid electric vehicle (PHEV) A vehicle whose propulsion is mostly electric with batteries re-charged from an electric source but extra power and distance are provided by a hybrid internal combustion engine. Emission pathways See Pathways. Emission scenario A plausible representation of the future development of emissions of substances that are radiatively active (e.g., greenhouse gases (GHGs), aerosols) based on a coherent and internally consistent set of assumptions about driving forces (such as demographic and socio-economic development, technological change, energy and land use) and their key relationships. Concentration scenarios, derived from emission scenarios, are often used as input to a climate model to compute climate projections. See also Baseline scenario, Mitigation scenario, Socio-economic scenario, Scenario, Representative Concentration Pathways (RCPs) (under Pathways), Shared Socio-economic Pathways (SSPs) (under Pathways) and Transformation pathways (under Pathways). Emission trajectories A projected development in time of the emission of a greenhouse gas (GHG) or group of GHGs, aerosols, and GHG precursors. See also Emission pathways (under Pathways). Emissions trading A market-based instrument aiming at meeting a mitigation objective in an efficient way. A cap on GHG emissions is divided in tradeable emission permits that are allocated by a combination of auctioning and handing out free allowances to entities within the jurisdiction of the trading scheme. Entities need to surrender emission permits equal to the amount of their emissions (e.g., tonnes of CO2). An entity may sell excess permits to entities that can avoid the same amount of emissions in a cheaper way. Trading schemes may occur at the intra-company, domestic, or international level (e.g., the flexibility mechanisms under the Kyoto Protocol and the EU-ETS) and may apply to carbon dioxide (CO2), other greenhouse gases (GHGs), or other substances. Enabling conditions Conditions that affect the feasibility of adaptation and mitigation options, and can accelerate and scale-up systemic transitions that would limit temperature increase to 1.5°C and enhance capacities of systems and societies to adapt to the associated climate change, while achieving sustainable development, eradicating poverty and reducing inequalities. Enabling conditions include finance, technological innovation, strengthening policy instruments, institutional capacity, multilevel governance, and changes in human behaviour and lifestyles. They also include inclusive processes, attention to power asymmetries and unequal opportunities for development and reconsideration of values. See also Feasibility. Energy efficiency The ratio of output or useful energy or energy services or other useful physical outputs obtained from a system, conversion process, transmission or storage activity to the input of energy (measured as kWh kWh-1, tonnes kWh-1 or any other physical measure of useful output like tonne-km transported). Energy efficiency is often described by energy intensity. In economics, energy intensity describes the ratio of economic output to energy input. Most commonly energy efficiency is measured as input energy over a physical or economic unit, i.e., kWh USD-1 (energy intensity), kWh tonne-1. For buildings, it is often measured as kWh m-2, and for vehicles as km liter-1 or liter km-1. Very often in policy ‘energy efficiency’ is intended as the measures to reduce energy demand through technological options such as insulating buildings, more efficient appliances, efficient lighting, efficient vehicles, etc. Energy security The goal of a given country, or the global community as a whole, to maintain an adequate, stable and predictable energy supply. Measures encompass safeguarding the sufficiency of energy resources to meet national energy demand at competitive and stable prices and the resilience of the energy supply; enabling development and deployment of technologies; building sufficient infrastructure to generate, store and transmit energy supplies; and ensuring enforceable contracts of delivery. Enhanced weathering Enhancing the removal of carbon dioxide (CO2) from the atmosphere through dissolution of silicate and carbonate rocks by grinding these minerals to small particles and actively applying them to soils, coasts or oceans. (Model) Ensemble A group of parallel model simulations characterising historical climate conditions, climate predictions, or climate projections. Variation of the results across the ensemble members may give an estimate of modelling-based uncertainty. Ensembles made with the same model but different initial conditions only characterize the uncertainty associated with internal climate variability, whereas multimodel ensembles including simulations by several models also include the impact of model differences. Perturbed parameter ensembles, in which model parameters are varied in a systematic


manner, aim to assess the uncertainty resulting from internal model specifications within a single model. Remaining sources of uncertainty unaddressed with model ensembles are related to systematic model errors or biases, which may be assessed from systematic comparisons of model simulations with observations wherever available. See also Climate projection. Equality A principle that ascribes equal worth to all human beings, including equal opportunities, rights, and obligations, irrespective of origins. Inequality Uneven opportunities and social positions, and processes of discrimination within a group or society, based on gender, class, ethnicity, age, and (dis) ability, often produced by uneven development. Income inequality refers to gaps between highest and lowest income earners within a country and between countries. See also Equity, Ethics and Fairness. Equilibrium climate sensitivity See Climate sensitivity. Equity Equity is the principle of fairness in burden sharing and is a basis for understanding how the impacts and responses to climate change, including costs and benefits, are distributed in and by society in more or less equal ways. It is often aligned with ideas of equality, fairness and justice and applied with respect to equity in the responsibility for, and distribution of, climate impacts and policies across society, generations, and gender, and in the sense of who participates and controls the processes of decision-making. Distributive equity Equity in the consequences, outcomes, costs and benefits of actions or policies. In the case of climate change or climate policies for different people, places and countries, including equity aspects of sharing burdens and benefits for mitigation and adaptation. Gender equity Ensuring equity in that women and men have the same rights, resources and opportunities. In the case of climate change gender equity recognizes that women are often more vulnerable to the impacts of climate change and may be disadvantaged in the process and outcomes of climate policy. Inter-generational equity Equity between generations that acknowledges that the effects of past and present emissions, vulnerabilities and policies impose costs and benefits for people in the future and of different age groups. Procedural equity Equity in the process of decision-making, including recognition and inclusiveness in participation, equal representation, bargaining power, voice and equitable access to knowledge and resources to participate. See also Equality, Ethics and Fairness. Ethics Ethics involves questions of justice and value. Justice is concerned with right and wrong, equity and fairness, and, in general, with the rights to which people and living beings are entitled. Value is a matter of worth, benefit, or good. See also Equality, Equity and Fairness. Evidence Data and information used in the scientific process to establish findings. In this report, the degree of evidence reflects the amount, quality and consistency of scientific/technical information on which the Lead Authors are basing their findings. See also Agreement, Confidence, Likelihood and Uncertainty. Exposure The presence of people; livelihoods; species or ecosystems; environmental functions, services, and resources; infrastructure; or economic, social, or cultural assets in places and settings that could be adversely affected. See also Hazard, Risk and Vulnerability. Extratropical cyclone Any cyclonic-scale storm that is not a tropical cyclone. Usually refers to a middle- or high-latitude migratory storm system formed in regions of large horizontal temperature variations. Sometimes called extratropical storm or extratropical low. See also Tropical cyclone. Extreme weather event An extreme weather event is an event that is rare at a particular place and time of year. Definitions of rare vary, but an extreme weather event would normally be as rare as or rarer than the th or 90th percentile of a probability density function estimated from observations. By definition, the characteristics of what is called extreme weather may vary from place to place in an absolute sense. When a pattern of extreme weather persists for some time, such as a season, it may be classed as an extreme climate event, especially if it yields an average or total that is itself extreme (e.g., drought or heavy rainfall over a season). See also Heatwave and Climate extreme (extreme weather or climate event). Extreme weather or climate event See Climate extreme (extreme weather or climate event). Fairness Impartial and just treatment without favouritism or discrimination in which each person is considered of equal worth with equal opportunity. See also Equity, Equality and Ethics. Feasibility The degree to which climate goals and response options are considered possible and/or desirable. Feasibility depends on geophysical, ecological, technological, economic, social and institutional conditions for change. Conditions underpinning feasibility are dynamic, spatially variable, and may vary between different groups. See also Enabling conditions. Feasible scenario commitment See Climate change commitment. Feedback See Climate feedback. Flexible governance See Governance. Flood The overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas that are not normally submerged. Floods include river (fluvial) floods, flash floods, urban floods, pluvial floods, sewer floods, coastal floods, and glacial lake outburst floods. Food security A situation that exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy life (FAO, 2001). Food wastage Food wastage encompasses food loss (the loss of food during production and transportation) and food waste (the waste of food by the consumer) (FAO, 2013). Forcing See Radiative forcing. Forest A vegetation type dominated by trees. Many definitions of the term forest are in use throughout the world, reflecting wide differences in biogeophysical conditions, social structure and economics. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000). See also information provided by the United Nations Framework Convention on Climate Change (UNFCCC, ) and the Report on Definitions and Methodological Options to Inventory Emissions from Direct Human-induced Degradation of Forests and Devegetation of Other Vegetation Types (IPCC, 2003). See also Afforestation, Deforestation and Reforestation. Fossil fuels Carbon-based fuels from fossil hydrocarbon deposits, including coal, oil, and natural gas.


Framework Convention on Climate Change See United Nations Framework Convention on Climate Change (UNFCCC). Gender equity See Equity. General purpose technologies (GPT) General purpose technologies can be or are used pervasively in a wide range of sectors in ways that fundamentally change the modes of operation of those sectors (Helpman, ). Examples include the steam engine, power generator and motor, ICT, and biotechnology. Geoengineering In this report, separate consideration is given to the two main approaches considered as ‘geoengineering’ in some of the literature: solar radiation modification (SRM) and carbon dioxide removal (CDR). Because of this separation, the term ‘geoengineering’ is not used in this report. See also Carbon dioxide removal (CDR) and Solar radiation modification (SRM). Glacier A perennial mass of ice, and possibly firn and snow, originating on the land surface by the recrystallisation of snow and showing evidence of past or present flow. A glacier typically gains mass by accumulation of snow, and loses mass by melting and ice discharge into the sea or a lake if the glacier terminates in a body of water. Land ice masses of continental size (>50,000 km2) are referred to as ice sheets. See also Ice sheet. Global climate model (also referred to as general circulation model, both abbreviated as GCM) See Climate model. Global mean surface temperature (GMST) Estimated global average of near-surface air temperatures over land and sea-ice, and sea surface temperatures over ice-free ocean regions, with changes normally expressed as departures from a value over a specified reference period. When estimating changes in GMST, near-surface air temperature over both land and oceans are also used.1 See also Land surface air temperature, Sea surface temperature (SST) and Global mean surface air temperature (GSAT). Global mean surface air temperature (GSAT) Global average of near-surface air temperatures over land and oceans. Changes in GSAT are often used as a measure of global temperature change in climate models but are not observed directly. See also Global mean surface temperature (GMST) and Land surface air temperature. Global warming The estimated increase in global mean surface temperature (GMST) averaged over a 30-year period, or the 30-year period centered on a particular year or decade, expressed relative to pre-industrial levels unless otherwise specified. For 30-year periods that span past and future years, the current multi-decadal warming trend is assumed to continue. See also Climate change and Climate variability. Governance A comprehensive and inclusive concept of the full range of means for deciding, managing, implementing and monitoring policies and measures. Whereas government is defined strictly in terms of the nation-state, the more inclusive concept of governance recognizes the contributions of various levels of government (global, international, regional, sub-national and local) and the contributing roles of the private sector, of nongovernmental actors, and of civil society to addressing the many types of issues facing the global community. Adaptive governance An emerging term in the literature for the evolution of formal and informal institutions of governance that prioritize social learning in planning, implementation and evaluation of policy through iterative social learning to steer the use and protection of natural resources, ecosystem services and common pool natural resources, particularly in situations of complexity and uncertainty. Climate governance Purposeful mechanisms and measures aimed at steering social systems towards preventing, mitigating, or adapting to the risks posed by climate change (Jagers and Stripple, 2003). Deliberative governance Deliberative governance involves decision-making through inclusive public conversation, which allows opportunity for developing policy options through public discussion rather than collating individual preferences through voting or referenda (although the latter governance mechanisms can also be proceeded and legitimated by public deliberation processes). Flexible governance Strategies of governance at various levels, which prioritize the use of social learning and rapid feedback mechanisms in planning and policy making, often through incremental, experimental and iterative management processes. Governance capacity The ability of governance institutions, leaders, and non-state and civil society to plan, co-ordinate, fund, implement, evaluate and adjust policies and measures over the short, medium and long term, adjusting for uncertainty, rapid change and wide-ranging impacts and multiple actors and demands. Multilevel governance Multilevel governance refers to negotiated, non-hierarchical exchanges between institutions at the transnational, national, regional and local levels. Multilevel governance identifies relationships among governance processes at these different levels. Multilevel governance does include negotiated relationships among institutions at different institutional levels and also a vertical ‘layering’ of governance processes at different levels. Institutional relationships take place directly between transnational, regional and local levels, thus bypassing the state level (Peters and Pierre, 2001) Participatory governance A governance system that enables direct public engagement in decisionmaking using a variety of techniques for example, referenda, community deliberation, citizen juries or participatory budgeting. The approach can be applied in formal and informal institutional contexts from national to local, but is usually associated with devolved decision-making. This definition builds from Fung and Wright (2003) and Sarmiento and Tilly (2018). Governance capacity See Governance. Green infrastructure The interconnected set of natural and constructed ecological systems, green spaces and other landscape features. It includes planted and indigenous trees, wetlands, parks, green open spaces and original grassland and woodlands, as well as possible building and street-level design interventions that incorporate vegetation. Green infrastructure provides services and functions in the same way as conventional infrastructure. This definition builds from Culwick and Bobbins (2016). Greenhouse gas (GHG) Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of terrestrial radiation emitted by the Earth’s surface, the atmosphere itself and by clouds. This property causes the greenhouse effect. Water vapour (H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and Past IPCC reports, reflecting the literature, have used a variety of approximately equivalent metrics of GMST change.


ozone (O3) are the primary GHGs in the Earth’s atmosphere. Moreover, there are a number of entirely human-made GHGs in the atmosphere, such as the halocarbons and other chlorine- and bromine-containing substances, dealt with under the Montreal Protocol. Beside CO2, N2O and CH4, the Kyoto Protocol deals with the GHGs sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs). See also Carbon dioxide (CO2), Methane (CH4), Nitrous oxide (N2O) and Ozone (O3). Greenhouse gas removal (GGR) Withdrawal of a GHG and/or a precursor from the atmosphere by a sink. See also Carbon dioxide removal (CDR) and Negative emissions. Gross domestic product (GDP) The sum of gross value added, at purchasers’ prices, by all resident and non-resident producers in the economy, plus any taxes and minus any subsidies not included in the value of the products in a country or a geographic region for a given period, normally one year. GDP is calculated without deducting for depreciation of fabricated assets or depletion and degradation of natural resources. Gross fixed capital formation (GFCF) One component of the GDP that corresponds to the total value of acquisitions, minus disposals of fixed assets during one year by the business sector, governments and households, plus certain additions to the value of non-produced assets (such as subsoil assets or major improvements in the quantity, quality or productivity of land). Halocarbons A collective term for the group of partially halogenated organic species, which includes the chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), halons, methyl chloride and methyl bromide. Many of the halocarbons have large global warming potentials. The chlorine and bromine-containing halocarbons are also involved in the depletion of the ozone layer. Hazard The potential occurrence of a natural or human-induced physical event or trend that may cause loss of life, injury, or other health impacts, as well as damage and loss to property, infrastructure, livelihoods, service provision, ecosystems and environmental resources. See also Disaster, Exposure, Risk, and Vulnerability. Heatwave A period of abnormally hot weather. Heatwaves and warm spells have various and in some cases overlapping definitions. See also Extreme weather event. Heating, ventilation, and air conditioning (HVAC) Heating, ventilation and air conditioning technology is used to control temperature and humidity in an indoor environment, be it in buildings or in vehicles, providing thermal comfort and healthy air quality to the occupants. HVAC systems can be designed for an isolated space, an individual building or a distributed heating and cooling network within a building structure or a district heating system. The latter provides economies of scale and also scope for integration with solar heat, natural seasonal cooling/heating etc. Holocene The Holocene is the current interglacial geological epoch, the second of two epochs within the Quaternary period, the preceding being the Pleistocene. The International Commission on Stratigraphy defines the start of the Holocene at 11,650 years before 1950. See also Anthropocene. Human behaviour The way in which a person acts in response to a particular situation or stimulus. Human actions are relevant at different levels, from international, national, and sub-national actors, to NGO, firmlevel actors, and communities, households, and individual actions. Adaptation behaviour Human actions that directly or indirectly affect the risks of climate change impacts. Mitigation behaviour Human actions that directly or indirectly influence mitigation. Human behavioural change A transformation or modification of human actions. Behaviour change efforts can be planned in ways that mitigate climate change and/or reduce negative consequences of climate change impacts. Human rights Rights that are inherent to all human beings, universal, inalienable, and indivisible, typically expressed and guaranteed by law. They include the right to life; economic, social, and cultural rights; and the right to development and self-determination. Based upon the definition by the UN Office of the High Commissioner for Human Rights (UNOHCHR, 2018). Procedural rights Rights to a legal procedure to enforce substantive rights. Substantive rights Basic human rights, including the right to the substance of being human such as life itself, liberty and happiness. Human security A condition that is met when the vital core of human lives is protected, and when people have the freedom and capacity to live with dignity. In the context of climate change, the vital core of human lives includes the universal and culturally specific, material and nonmaterial elements necessary for people to act on behalf of their interests and to live with dignity. Human system Any system in which human organizations and institutions play a major role. Often, but not always, the term is synonymous with society or social system. Systems such as agricultural systems, urban systems, political systems, technological systems and economic systems are all human systems in the sense applied in this report. Hydrological cycle The cycle in which water evaporates from the oceans and the land surface, is carried over the earth in atmospheric circulation as water vapour, condenses to form clouds, precipitates as rain or snow, which on land can be intercepted by trees and vegetation, potentially accumulates as snow or ice, provides runoff on the land surface, infiltrates into soils, recharges groundwater, discharges into streams, flows out into the oceans, and ultimately evaporates again from the ocean or land surface. The various systems involved in the hydrological cycle are usually referred to as hydrological systems. Ice sheet A mass of land ice of continental size that is sufficiently thick to cover most of the underlying bed, so that its shape is mainly determined by its dynamics (the flow of the ice as it deforms internally and/or slides at its base). An ice sheet flows outward from a high central ice plateau with a small average surface slope. The margins usually slope more steeply, and most ice is discharged through fast flowing ice streams or outlet glaciers, in some cases into the sea or into ice shelves floating on the sea. There are only two ice sheets in the modern world, one on Greenland and one on Antarctica. During glacial periods there were others. See also Glacier. (climate change) Impact assessment The practice of identifying and evaluating, in monetary and/or non-monetary terms, the effects of climate change on natural and human systems. Impacts (consequences, outcomes) The consequences of realized risks on natural and human systems, where risks result from the interactions of climate-related hazards (including extreme weather and climate events), exposure, and vulnerability. Impacts generally refer to effects on lives; livelihoods; health and well-being; ecosystems and species; economic, social and cultural assets; services (including


ecosystem services); and infrastructure. Impacts may be referred to as consequences or outcomes, and can be adverse or beneficial. See also Adaptation, Exposure, Hazard, Loss and Damage, and losses and damages, and Vulnerability. Incremental adaptation See Adaptation. Indigenous knowledge Indigenous knowledge refers to the understandings, skills and philosophies developed by societies with long histories of interaction with their natural surroundings. For many Indigenous peoples, Indigenous knowledge informs decision-making about fundamental aspects of life, from day-to-day activities to longer term actions. This knowledge is integral to cultural complexes, which also encompass language, systems of classification, resource use practices, social interactions, values, ritual and spirituality. These distinctive ways of knowing are important facets of the world’s cultural diversity. This definition builds on UNESCO (2018). Indirect land-use change (iLUC) See Land-use change (LUC). Industrial revolution A period of rapid industrial growth with farreaching social and economic consequences, beginning in Britain during the second half of the 18th century and spreading to Europe and later to other countries, including the United States. The invention of the steam engine was an important trigger of this development. The industrial revolution marks the beginning of a strong increase in the use of fossil fuels, initially coal, and hence emission of carbon dioxide (CO2). See also Pre-industrial. Industrialized/developed/developing countries There are a diversity of approaches for categorizing countries on the basis of their level of development, and for defining terms such as industrialized, developed, or developing. Several categorizations are used in this report. (1) In the United Nations system, there is no established convention for designation of developed and developing countries or areas. (2) The United Nations Statistics Division specifies developed and developing regions based on common practice. In addition, specific countries are designated as Least Developed Countries (LDC), landlocked developing countries, small island developing states, and transition economies. Many countries appear in more than one of these categories. (3) The World Bank uses income as the main criterion for classifying countries as low, lower middle, upper middle and high income. (4) The UNDP aggregates indicators for life expectancy, educational attainment, and income into a single composite Human Development Index (HDI) to classify countries as low, medium, high or very high human development. Inequality See Equality. Information and communication technology (ICT) An umbrella term that includes any information and communication device or application, encompassing: computer systems, network hardware and software, cell phones, etc. Infrastructure commitment See Climate change commitment. Institution Institutions are rules and norms held in common by social actors that guide, constrain and shape human interaction. Institutions can be formal, such as laws and policies, or informal, such as norms and conventions. Organizations – such as parliaments, regulatory agencies, private firms and community bodies – develop and act in response to institutional frameworks and the incentives they frame. Institutions can guide, constrain and shape human interaction through direct control, through incentives, and through processes of socialization. See also Institutional capacity. Institutional capacity Institutional capacity comprises building and strengthening individual organizations and providing technical and management training to support integrated planning and decisionmaking processes between organizations and people, as well as empowerment, social capital, and an enabling environment, including the culture, values and power relations (Willems and Baumert, 2003). Integrated assessment A method of analysis that combines results and models from the physical, biological, economic and social sciences and the interactions among these components in a consistent framework to evaluate the status and the consequences of environmental change and the policy responses to it. See also Integrated assessment model (IAM). Integrated assessment model (IAM) Integrated assessment models (IAMs) integrate knowledge from two or more domains into a single framework. They are one of the main tools for undertaking integrated assessments. One class of IAM used in respect of climate change mitigation may include representations of: multiple sectors of the economy, such as energy, land use and land-use change; interactions between sectors; the economy as a whole; associated GHG emissions and sinks; and reduced representations of the climate system. This class of model is used to assess linkages between economic, social and technological development and the evolution of the climate system. Another class of IAM additionally includes representations of the costs associated with climate change impacts, but includes less detailed representations of economic systems. These can be used to assess impacts and mitigation in a cost–benefit framework and have been used to estimate the social cost of carbon. Integrated water resources management (IWRM) A process which promotes the coordinated development and management of water, land and related resources in order to maximize economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems. Inter-generational equity See Equity. Inter-generational justice See Justice. Internal variability See Climate variability. Internet of Things (IoT) The network of computing devices embedded in everyday objects such as cars, phones and computers, connected via the internet, enabling them to send and receive data. Iron fertilization See Ocean fertilization. Irreversibility A perturbed state of a dynamical system is defined as irreversible on a given timescale, if the recovery time scale from this state due to natural processes is substantially longer than the time it takes for the system to reach this perturbed state. See also Tipping point. Justice Justice is concerned with ensuring that people get what is due to them, setting out the moral or legal principles of fairness and equity in the way people are treated, often based on the ethics and values of society. Climate justice Justice that links development and human rights to achieve a humancentred approach to addressing climate change, safeguarding the rights of the most vulnerable people and sharing the burdens and benefits of climate change and its impacts equitably and fairly. This definition builds upon the one used by the Mary Robinson Foundation – Climate Justice (MRFCJ, 2018). Distributive justice Justice in the allocation of economic and non-economic costs and benefits across society.


Inter-generational justice Justice in the distribution of economic and non-economic costs and benefits across generations. Procedural justice Justice in the way outcomes are brought about including who participates and is heard in the processes of decision-making. Social justice Just or fair relations within society that seek to address the distribution of wealth, access to resources, opportunity, and support according to principles of justice and fairness. See also Equity, Ethics, Fairness, and Human rights. Kyoto Protocol The Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC) is an international treaty adopted in December 1997 in Kyoto, Japan, at the Third Session of the Conference of the Parties (COP3) to the UNFCCC. It contains legally binding commitments, in addition to those included in the UNFCCC. Countries included in Annex B of the Protocol (mostly OECD countries and countries with economies in transition) agreed to reduce their anthropogenic greenhouse gas (GHG) emissions (carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6)) by at least 5% below 1990 levels in the first commitment period (2008–2012). The Kyoto Protocol entered into force on 16 February 2005 and as of May had 192 Parties (191 States and the European Union). A second commitment period was agreed in December 2012 at COP18, known as the Doha Amendment to the Kyoto Protocol, in which a new set of Parties committed to reduce GHG emissions by at least 18% below 1990 levels in the period from 2013 to 2020. However, as of May 2018, the Doha Amendment had not received sufficient ratifications to enter into force. See also United Nations Framework Convention on Climate Change (UNFCCC) and Paris Agreement. Land surface air temperature The near-surface air temperature over land, typically measured at 1.25–2 m above the ground using standard meteorological equipment. Land use Land use refers to the total of arrangements, activities and inputs undertaken in a certain land cover type (a set of human actions). The term land use is also used in the sense of the social and economic purposes for which land is managed (e.g., grazing, timber extraction, conservation and city dwelling). In national greenhouse gas inventories, land use is classified according to the IPCC land use categories of forest land, cropland, grassland, wetland, settlements, other. See also Land-use change (LUC). Land-use change (LUC) Land-use change involves a change from one land use category to another. Indirect land-use change (iLUC) Refers to market-mediated or policy-driven shifts in land use that cannot be directly attributed to land-use management decisions of individuals or groups. For example, if agricultural land is diverted to fuel production, forest clearance may occur elsewhere to replace the former agricultural production. Land use, land-use change and forestry (LULUCF) In the context of national greenhouse gas (GHG) inventories under the UNFCCC, LULUCF is a GHG inventory sector that covers anthropogenic emissions and removals of GHG from carbon pools in managed lands, excluding non-CO2 agricultural emissions. Following the 2006 IPCC Guidelines for National GHG Inventories, ‘anthropogenic’ land-related GHG fluxes are defined as all those occurring on ‘managed land’, i.e., ‘where human interventions and practices have been applied to perform production, ecological or social functions’. Since managed land may include CO2 removals not considered as ‘anthropogenic’ in some of the scientific literature assessed in this report (e.g., removals associated with CO2 fertilization and N deposition), the land-related net GHG emission estimates included in this report are not necessarily directly comparable with LULUCF estimates in National GHG Inventories. See also Afforestation, Deforestation, Reforestation, and the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000). Land use, land-use change and forestry (LULUCF) See Land-use change (LUC). Life cycle assessment (LCA) Compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product or service throughout its life cycle. This definition builds from ISO (2018). Likelihood The chance of a specific outcome occurring, where this might be estimated probabilistically. Likelihood is expressed in this report using a standard terminology (Mastrandrea et al., 2010). See Section 1.6 for the list of likelihood qualifiers used. See also Agreement, Evidence, Confidence and Uncertainty. Livelihood The resources used and the activities undertaken in order to live. Livelihoods are usually determined by the entitlements and assets to which people have access. Such assets can be categorised as human, social, natural, physical or financial. Local knowledge Local knowledge refers to the understandings and skills developed by individuals and populations, specific to the places where they live. Local knowledge informs decision-making about fundamental aspects of life, from day-to-day activities to longer-term actions. This knowledge is a key element of the social and cultural systems which influence observations of, and responses to climate change; it also informs governance decisions. This definition builds on UNESCO (2018). Lock-in A situation in which the future development of a system, including infrastructure, technologies, investments, institutions, and behavioural norms, is determined or constrained (‘locked in’) by historic developments. Long-lived climate forcers (LLCF) Long-lived climate forcers refer to a set of well-mixed greenhouse gases with long atmospheric lifetimes. This set of compounds includes carbon dioxide (CO2) and nitrous oxide (N2O), together with some fluorinated gases. They have a warming effect on climate. These compounds accumulate in the atmosphere at decadal to centennial time scales, and their effect on climate hence persists for decades to centuries after their emission. On time scales of decades to a century, already emitted emissions of long-lived climate forcers can only be abated by greenhouse gas removal (GGR). See also Short-lived climate forcers (SLCF). Loss and Damage, and losses and damages Research has taken Loss and Damage (capitalized letters) to refer to political debate under the UNFCCC following the establishment of the Warsaw Mechanism on Loss and Damage in 2013, which is to ‘address loss and damage associated with impacts of climate change, including extreme events and slow onset events, in developing countries that are particularly vulnerable to the adverse effects of climate change.’ Lowercase letters (losses and damages) have been taken to refer broadly to harm from (observed) impacts and (projected) risks (see Mechler et al., in press). Maladaptive actions (Maladaptation) Actions that may lead to increased risk of adverse climate-related outcomes, including via increased GHG emissions, increased vulnerability to climate change, or diminished welfare, now or in the future. Maladaptation is usually an unintended consequence.


Market exchange rate (MER) The rate at which a currency of one country can be exchanged with the currency of another country. In most economies such rates evolve daily while in others there are official conversion rates that are adjusted periodically. See also Purchasing power parity (PPP). Market failure When private decisions are based on market prices that do not reflect the real scarcity of goods and services but rather reflect market distortions, they do not generate an efficient allocation of resources but cause welfare losses. A market distortion is any event in which a market reaches a market clearing price that is substantially different from the price that a market would achieve while operating under conditions of perfect competition and state enforcement of legal contracts and the ownership of private property. Examples of factors causing market prices to deviate from real economic scarcity are environmental externalities, public goods, monopoly power, information asymmetry, transaction costs and non-rational behaviour. Measurement, Reporting and Verification (MRV) Measurement ‘Processes of data collection over time, providing basic datasets, including associated accuracy and precision, for the range of relevant variables. Possible data sources are field measurements, field observations, detection through remote sensing and interviews.’ (UN-REDD, 2009). Reporting ‘The process of formal reporting of assessment results to the UNFCCC, according to predetermined formats and according to established standards, especially the IPCC [Intergovernmental Panel on Climate Change] Guidelines and GPG [Good Practice Guidance].’ (UN-REDD, ) Verification ‘The process of formal verification of reports, for example the established approach to verify national communications and national inventory reports to the UNFCCC.’ (UN-REDD, 2009) Megadrought See Drought. Methane (CH4) One of the six greenhouse gases (GHGs) to be mitigated under the Kyoto Protocol and is the major component of natural gas and associated with all hydrocarbon fuels. Significant emissions occur as a result of animal husbandry and agriculture, and their management represents a major mitigation option. Migrant See Migration. Migration The International Organization for Migration (IOM) defines migration as ‘The movement of a person or a group of persons, either across an international border, or within a State. It is a population movement, encompassing any kind of movement of people, whatever its length, composition and causes; it includes migration of refugees, displaced persons, economic migrants, and persons moving for other purposes, including family reunification.’ (IOM, 2018). Migrant The International Organization for Migration (IOM) defines a migrant as ‘any person who is moving or has moved across an international border or within a State away from his/her habitual place of residence, regardless of (1) the person’s legal status; (2) whether the movement is voluntary or involuntary; (3) what the causes for the movement are; or (4) what the length of the stay is.’ (IOM, 2018). See also (Internal) Displacement. Millennium Development Goals (MDGs) A set of eight timebound and measurable goals for combating poverty, hunger, disease, illiteracy, discrimination against women and environmental degradation. These goals were agreed at the UN Millennium Summit in 2000 together with an action plan to reach the goals by 2015. Mitigation (of climate change) A human intervention to reduce emissions or enhance the sinks of greenhouse gases. Mitigation behaviour See Human behaviour. Mitigation measures In climate policy, mitigation measures are technologies, processes or practices that contribute to mitigation, for example, renewable energy (RE) technologies, waste minimization processes and public transport commuting practices. See also Mitigation option, and Policies (for climate change mitigation and adaptation). Mitigation option A technology or practice that reduces GHG emissions or enhances sinks. Mitigation pathways See Pathways. Mitigation scenario A plausible description of the future that describes how the (studied) system responds to the implementation of mitigation policies and measures. See also Emission scenario, Pathways, Socio-economic scenario and Stabilization (of GHG or CO2-equivalent concentration). Monitoring and evaluation (M&E) Monitoring and evaluation refers to mechanisms put in place at national to local scales to respectively monitor and evaluate efforts to reduce greenhouse gas emissions and/ or adapt to the impacts of climate change with the aim of systematically identifying, characterizing and assessing progress over time. Motivation (of an individual) An individual’s reason or reasons for acting in a particular way; individuals may consider various consequences of actions, including financial, social, affective and environmental consequences. Motivation can come from outside (extrinsic) or from inside (intrinsic) the individual. Multilevel governance See Governance. Narratives Qualitative descriptions of plausible future world evolutions, describing the characteristics, general logic and developments underlying a particular quantitative set of scenarios. Narratives are also referred to in the literature as ‘storylines’. See also Scenario, Scenario storyline and Pathways. Nationally Determined Contributions (NDCs) A term used under the United Nations Framework Convention on Climate Change (UNFCCC) whereby a country that has joined the Paris Agreement outlines its plans for reducing its emissions. Some countries’ NDCs also address how they will adapt to climate change impacts, and what support they need from, or will provide to, other countries to adopt low-carbon pathways and to build climate resilience. According to Article 4 paragraph 2 of the Paris Agreement, each Party shall prepare, communicate and maintain successive NDCs that it intends to achieve. In the lead up to st Conference of the Parties in Paris in 2015, countries submitted Intended Nationally Determined Contributions (INDCs). As countries join the Paris Agreement, unless they decide otherwise, this INDC becomes their first Nationally Determined Contribution (NDC). See also United Nations Framework Convention on Climate Change (UNFCCC) and Paris Agreement. Negative emissions Removal of greenhouse gases (GHGs) from the atmosphere by deliberate human activities, i.e., in addition to the removal that would occur via natural carbon cycle processes. See also Net negative emissions, Net zero emissions, Carbon dioxide removal (CDR) and Greenhouse gas removal (GGR).


Net negative emissions A situation of net negative emissions is achieved when, as result of human activities, more greenhouse gases are removed from the atmosphere than are emitted into it. Where multiple greenhouse gases are involved, the quantification of negative emissions depends on the climate metric chosen to compare emissions of different gases (such as global warming potential, global temperature change potential, and others, as well as the chosen time horizon). See also Negative emissions, Net zero emissions and Net zero CO2 emissions. Net zero CO2 emissions Net zero carbon dioxide (CO2) emissions are achieved when anthropogenic CO2 emissions are balanced globally by anthropogenic CO2 removals over a specified period. Net zero CO2 emissions are also referred to as carbon neutrality. See also Net zero emissions and Net negative emissions. Net zero emissions Net zero emissions are achieved when anthropogenic emissions of greenhouse gases to the atmosphere are balanced by anthropogenic removals over a specified period. Where multiple greenhouse gases are involved, the quantification of net zero emissions depends on the climate metric chosen to compare emissions of different gases (such as global warming potential, global temperature change potential, and others, as well as the chosen time horizon). See also Net zero CO2 emissions, Negative emissions and Net negative emissions. Nitrous oxide (N2O) One of the six greenhouse gases (GHGs) to be mitigated under the Kyoto Protocol. The main anthropogenic source of N2O is agriculture (soil and animal manure management), but important contributions also come from sewage treatment, fossil fuel combustion, and chemical industrial processes. N2O is also produced naturally from a wide variety of biological sources in soil and water, particularly microbial action in wet tropical forests. Non-CO2 emissions and radiative forcing Non-CO2 emissions included in this report are all anthropogenic emissions other than CO2 that result in radiative forcing. These include short-lived climate forcers, such as methane (CH4), some fluorinated gases, ozone (O3) precursors, aerosols or aerosol precursors, such as black carbon and sulphur dioxide, respectively, as well as long-lived greenhouse gases, such as nitrous oxide (N2O) or other fluorinated gases. The radiative forcing associated with non-CO2 emissions and changes in surface albedo is referred to as non-CO2 radiative forcing. Non-overshoot pathways See Pathways. Ocean acidification (OA) Ocean acidification refers to a reduction in the pH of the ocean over an extended period, typically decades or longer, which is caused primarily by uptake of carbon dioxide (CO2) from the atmosphere, but can also be caused by other chemical additions or subtractions from the ocean. Anthropogenic ocean acidification refers to the component of pH reduction that is caused by human activity (IPCC, , p. 37). Ocean fertilization Deliberate increase of nutrient supply to the near-surface ocean in order to enhance biological production through which additional carbon dioxide (CO2) from the atmosphere is sequestered. This can be achieved by the addition of micro-nutrients or macro-nutrients. Ocean fertilization is regulated by the London Protocol. Overshoot See Temperature overshoot. Overshoot pathways See Pathways. Ozone (O3) Ozone, the triatomic form of oxygen (O3), is a gaseous atmospheric constituent. In the troposphere, it is created both naturally and by photochemical reactions involving gases resulting from human activities (smog). Tropospheric ozone acts as a greenhouse gas. In the stratosphere, it is created by the interaction between solar ultraviolet radiation and molecular oxygen (O2). Stratospheric ozone plays a dominant role in the stratospheric radiative balance. Its concentration is highest in the ozone layer. Paris Agreement The Paris Agreement under the United Nations Framework Convention on Climate Change (UNFCCC) was adopted on December 2015 in Paris, France, at the 21st session of the Conference of the Parties (COP) to the UNFCCC. The agreement, adopted by 196 Parties to the UNFCCC, entered into force on 4 November 2016 and as of May 2018 had 195 Signatories and was ratified by 177 Parties. One of the goals of the Paris Agreement is ‘Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels’, recognising that this would significantly reduce the risks and impacts of climate change. Additionally, the Agreement aims to strengthen the ability of countries to deal with the impacts of climate change. The Paris Agreement is intended to become fully effective in 2020. See also United Nations Framework Convention on Climate Change (UNFCCC), Kyoto Protocol and Nationally Determined Contributions (NDCs). Participatory governance See Governance. Pathways The temporal evolution of natural and/or human systems towards a future state. Pathway concepts range from sets of quantitative and qualitative scenarios or narratives of potential futures to solutionoriented decision-making processes to achieve desirable societal goals. Pathway approaches typically focus on biophysical, techno-economic, and/or socio-behavioural trajectories and involve various dynamics, goals and actors across different scales. .5°C pathway A pathway of emissions of greenhouse gases and other climate forcers that provides an approximately one-in-two to two-in-three chance, given current knowledge of the climate response, of global warming either remaining below 1.5°C or returning to 1.5°C by around 2100 following an overshoot. See also Temperature overshoot. Adaptation pathways A series of adaptation choices involving trade-offs between short-term and long-term goals and values. These are processes of deliberation to identify solutions that are meaningful to people in the context of their daily lives and to avoid potential maladaptation. Development pathways Development pathways are trajectories based on an array of social, economic, cultural, technological, institutional and biophysical features that characterise the interactions between human and natural systems and outline visions for the future, at a particular scale. Emission pathways Modelled trajectories of global anthropogenic emissions over the 21st century are termed emission pathways. Mitigation pathways A mitigation pathway is a temporal evolution of a set of mitigation scenario features, such as greenhouse gas emissions and socio-economic development. Overshoot pathways Pathways that exceed the stabilization level (concentration, forcing, or temperature) before the end of a time horizon of interest (e.g., before ) and then decline towards that level by that time. Once the target level is exceeded, removal by sinks of greenhouse gases is required. See also Temperature overshoot.


Non-overshoot pathways Pathways that stay below the stabilization level (concentration, forcing, or temperature) during the time horizon of interest (e.g., until 2100). Representative Concentration Pathways (RCPs) Scenarios that include time series of emissions and concentrations of the full suite of greenhouse gases (GHGs) and aerosols and chemically active gases, as well as land use/land cover (Moss et al., 2008). The word representative signifies that each RCP provides only one of many possible scenarios that would lead to the specific radiative forcing characteristics. The term pathway emphasizes the fact that not only the long-term concentration levels but also the trajectory taken over time to reach that outcome are of interest (Moss et al., 2010). RCPs were used to develop climate projections in CMIP5. • RCP2.6: One pathway where radiative forcing peaks at approximately 3 W m-2 and then declines to be limited at 2.6 W m-2 in 2100 (the corresponding Extended Concentration Pathway, or ECP, has constant emissions after 2100). • RCP4.5 and RCP6.0: Two intermediate stabilization pathways in which radiative forcing is limited at approximately 4.5 W m-2 and 6.0 W m-2 in 2100 (the corresponding ECPs have constant concentrations after 2150). • RCP8.5: One high pathway which leads to >8.5 W m-2 in 2100 (the corresponding ECP has constant emissions after 2100 until and constant concentrations after 2250). See also Coupled Model Intercomparison Project (CMIP) and Shared Socio-economic Pathways (SSPs). Shared Socio-economic Pathways (SSPs) Shared Socio-economic Pathways (SSPs) were developed to complement the RCPs with varying socio-economic challenges to adaptation and mitigation (O’Neill et al., 2014). Based on five narratives, the SSPs describe alternative socio-economic futures in the absence of climate policy intervention, comprising sustainable development (SSP1), regional rivalry (SSP3), inequality (SSP4), fossil–fuelled development (SSP5) and middle-of-the-road development (SSP2) (O’Neill, 2000; O’Neill et al., ; Riahi et al., 2017). The combination of SSP-based socio-economic scenarios and Representative Concentration Pathway (RCP)-based climate projections provides an integrative frame for climate impact and policy analysis. Transformation pathways Trajectories describing consistent sets of possible futures of greenhouse gas (GHG) emissions, atmospheric concentrations, or global mean surface temperatures implied from mitigation and adaptation actions associated with a set of broad and irreversible economic, technological, societal and behavioural changes. This can encompass changes in the way energy and infrastructure are used and produced, natural resources are managed and institutions are set up and in the pace and direction of technological change. See also Scenario, Scenario storyline, Emission scenario, Mitigation scenario, Baseline scenario, Stabilization (of GHG or CO2-equivalent concentration) and Narratives. Peri-urban areas Peri-urban areas are those parts of a city that appear to be quite rural but are in reality strongly linked functionally to the city in its daily activities. Permafrost Ground (soil or rock and included ice and organic material) that remains at or below 0°C for at least two consecutive years. pH pH is a dimensionless measure of the acidity of a solution given by its concentration of hydrogen ions ([H+]). pH is measured on a logarithmic scale where pH = -log10[H+]. Thus, a pH decrease of 1 unit corresponds to a 10-fold increase in the concentration of H+, or acidity. Plug-in hybrid electric vehicle (PHEV) See Electric vehicle (EV). Policies (for climate change mitigation and adaptation) Policies are taken and/or mandated by a government – often in conjunction with business and industry within a single country, or collectively with other countries – to accelerate mitigation and adaptation measures. Examples of policies are support mechanisms for renewable energy supplies, carbon or energy taxes, fuel efficiency standards for automobiles, etc. Political economy The set of interlinked relationships between people, the state, society and markets as defined by law, politics, economics, customs and power that determine the outcome of trade and transactions and the distribution of wealth in a country or economy. Poverty Poverty is a complex concept with several definitions stemming from different schools of thought. It can refer to material circumstances (such as need, pattern of deprivation or limited resources), economic conditions (such as standard of living, inequality or economic position) and/or social relationships (such as social class, dependency, exclusion, lack of basic security or lack of entitlement). See also Poverty eradication. Poverty eradication A set of measures to end poverty in all its forms everywhere. See also Sustainable Development Goals (SDGs). Precursors Atmospheric compounds that are not greenhouse gases (GHGs) or aerosols, but that have an effect on GHG or aerosol concentrations by taking part in physical or chemical processes regulating their production or destruction rates. See also Aerosol and Greenhouse gas (GHG). Pre-industrial The multi-century period prior to the onset of largescale industrial activity around 1750. The reference period 1850–1900 is used to approximate pre-industrial global mean surface temperature (GMST). See also Industrial revolution. Procedural equity See Equity. Procedural justice See Justice. Procedural rights See Human rights. Projection A projection is a potential future evolution of a quantity or set of quantities, often computed with the aid of a model. Unlike predictions, projections are conditional on assumptions concerning, for example, future socio-economic and technological developments that may or may not be realized. See also Climate projection, Scenario and Pathways. Purchasing power parity (PPP) The purchasing power of a currency is expressed using a basket of goods and services that can be bought with a given amount in the home country. International comparison of, for example, gross domestic products (GDPs) of countries can be based on the purchasing power of currencies rather than on current exchange rates. PPP estimates tend to lower the gap between the per capita GDP in industrialized and developing countries. See also Market exchange rate (MER). Radiative forcing Radiative forcing is the change in the net, downward minus upward, radiative flux (expressed in W m-2) at the tropopause or top of atmosphere due to a change in a driver of climate change, such as a change in the concentration of carbon dioxide (CO2) or the output of the Sun. The traditional radiative forcing is computed with all tropospheric properties held fixed at their unperturbed values, and after allowing for stratospheric temperatures, if perturbed, to readjust to radiative-dynamical equilibrium. Radiative forcing is called instantaneous if no change in stratospheric temperature is accounted for. The radiative forcing once rapid adjustments are accounted for is termed


the effective radiative forcing. Radiative forcing is not to be confused with cloud radiative forcing, which describes an unrelated measure of the impact of clouds on the radiative flux at the top of the atmosphere. Reasons for Concern (RFCs) Elements of a classification framework, first developed in the IPCC Third Assessment Report, which aims to facilitate judgments about what level of climate change may be dangerous (in the language of Article 2 of the UNFCCC) by aggregating risks from various sectors, considering hazards, exposures, vulnerabilities, capacities to adapt, and the resulting impacts. Reducing Emissions from Deforestation and Forest Degradation (REDD+) An effort to create financial value for the carbon stored in forests, offering incentives for developing countries to reduce emissions from forested lands and invest in low-carbon paths to sustainable development (SD). It is therefore a mechanism for mitigation that results from avoiding deforestation. REDD+ goes beyond deforestation and forest degradation, and includes the role of conservation, sustainable management of forests and enhancement of forest carbon stocks. The concept was first introduced in 2005 in the 11th Session of the Conference of the Parties (COP) in Montreal and later given greater recognition in the 13th Session of the COP in 2007 at Bali and inclusion in the Bali Action Plan, which called for ‘policy approaches and positive incentives on issues relating to reducing emissions from deforestation and forest degradation in developing countries (REDD) and the role of conservation, sustainable management of forests and enhancement of forest carbon stock in developing countries.’ Since then, support for REDD has increased and has slowly become a framework for action supported by a number of countries. Reference period The period relative to which anomalies are computed. See also Anomaly. Reference scenario See Baseline scenario. Reforestation Planting of forests on lands that have previously contained forests but that have been converted to some other use. For a discussion of the term forest and related terms such as afforestation, reforestation and deforestation, see the IPCC Special Report on Land Use, Land-Use Change, and Forestry (IPCC, 2000), information provided by the United Nations Framework Convention on Climate Change (UNFCCC, ), the report on Definitions and Methodological Options to Inventory Emissions from Direct Human-induced Degradation of Forests and Devegetation of Other Vegetation Types (IPCC, 2003). See also Deforestation, Afforestation and Reducing Emissions from Deforestation and Forest Degradation (REDD+). Region A region is a relatively large-scale land or ocean area characterized by specific geographical and climatological features. The climate of a land-based region is affected by regional and local scale features like topography, land use characteristics and large water bodies, as well as remote influences from other regions, in addition to global climate conditions. The IPCC defines a set of standard regions for analyses of observed climate trends and climate model projections (see Figure 3.2; AR5, SREX). Remaining carbon budget Estimated cumulative net global anthropogenic CO2 emissions from the start of 2018 to the time that anthropogenic CO2 emissions reach net zero that would result, at some probability, in limiting global warming to a given level, accounting for the impact of other anthropogenic emissions. Representative Concentration Pathways (RCPs) See Pathways. Resilience The capacity of social, economic and environmental systems to cope with a hazardous event or trend or disturbance, responding or reorganizing in ways that maintain their essential function, identity and structure while also maintaining the capacity for adaptation, learning and transformation. This definition builds from the definition used by Arctic Council (2013). See also Hazard, Risk and Vulnerability. Risk The potential for adverse consequences where something of value is at stake and where the occurrence and degree of an outcome is uncertain. In the context of the assessment of climate impacts, the term risk is often used to refer to the potential for adverse consequences of a climate-related hazard, or of adaptation or mitigation responses to such a hazard, on lives, livelihoods, health and well-being, ecosystems and species, economic, social and cultural assets, services (including ecosystem services), and infrastructure. Risk results from the interaction of vulnerability (of the affected system), its exposure over time (to the hazard), as well as the (climate-related) hazard and the likelihood of its occurrence. Risk assessment The qualitative and/or quantitative scientific estimation of risks. See also Risk, Risk management and Risk perception. Risk management Plans, actions, strategies or policies to reduce the likelihood and/or consequences of risks or to respond to consequences. See also Risk, Risk assessment and Risk perception. Risk perception The subjective judgment that people make about the characteristics and severity of a risk. See also Risk, Risk assessment and Risk management. Runoff The flow of water over the surface or through the subsurface, which typically originates from the part of liquid precipitation and/or snow/ice melt that does not evaporate or refreeze, and is not transpired. See also Hydrological cycle. Scenario A plausible description of how the future may develop based on a coherent and internally consistent set of assumptions about key driving forces (e.g., rate of technological change, prices) and relationships. Note that scenarios are neither predictions nor forecasts, but are used to provide a view of the implications of developments and actions. See also Baseline scenario, Emission scenario, Mitigation scenario and Pathways. Scenario storyline A narrative description of a scenario (or family of scenarios), highlighting the main scenario characteristics, relationships between key driving forces and the dynamics of their evolution. Also referred to as ‘narratives’ in the scenario literature. See also Narratives. SDG-interaction score A seven-point scale (Nilsson et al., 2016) used to rate interactions between mitigation options and the SDGs. Scores range from +3 (indivisible) to −3 (cancelling), with a zero score indicating ‘consistent’ but with neither a positive or negative interaction. The scale, as applied in this report, also includes direction (whether the interaction is uni- or bi-directional) and confidence as assessed per IPCC guidelines. Sea ice Ice found at the sea surface that has originated from the freezing of seawater. Sea ice may be discontinuous pieces (ice floes) moved on the ocean surface by wind and currents (pack ice), or a motionless sheet attached to the coast (land-fast ice). Sea ice concentration is the fraction of the ocean covered by ice. Sea ice less than one year old is called firstyear ice. Perennial ice is sea ice that survives at least one summer. It may be subdivided into second-year ice and multi-year ice, where multi-year ice has survived at least two summers. Sea level change (sea level rise/sea level fall) Sea level can change, both globally and locally (relative sea level change) due to (1) a change in ocean volume as a result of a change in the mass of water in the ocean, (2) changes in ocean volume as a result of changes in ocean water density, (3) changes in the shape of the ocean basins and changes


in the Earth’s gravitational and rotational fields, and (4) local subsidence or uplift of the land. Global mean sea level change resulting from change in the mass of the ocean is called barystatic. The amount of barystatic sea level change due to the addition or removal of a mass of water is called its sea level equivalent (SLE). Sea level changes, both globally and locally, resulting from changes in water density are called steric. Density changes induced by temperature changes only are called thermosteric, while density changes induced by salinity changes are called halosteric. Barystatic and steric sea level changes do not include the effect of changes in the shape of ocean basins induced by the change in the ocean mass and its distribution. Sea surface temperature (SST) The sea surface temperature is the subsurface bulk temperature in the top few meters of the ocean, measured by ships, buoys, and drifters. From ships, measurements of water samples in buckets were mostly switched in the 1940s to samples from engine intake water. Satellite measurements of skin temperature (uppermost layer; a fraction of a millimeter thick) in the infrared or the top centimeter or so in the microwave are also used, but must be adjusted to be compatible with the bulk temperature. Sendai Framework for Disaster Risk Reduction The Sendai Framework for Disaster Risk Reduction 2015–2030 outlines seven clear targets and four priorities for action to prevent new, and to reduce existing, disaster risks. The voluntary, non-binding agreement recognizes that the State has the primary role to reduce disaster risk but that responsibility should be shared with other stakeholders, including local government and the private sector. Its aim is to achieve ‘substantial reduction of disaster risk and losses in lives, livelihoods and health and in the economic, physical, social, cultural and environmental assets of persons, businesses, communities and countries.’ Sequestration See Uptake. Shared Socio-economic Pathways (SSPs) See Pathways. Short-lived climate forcers (SLCF) Short-lived climate forcers refers to a set of compounds that are primarily composed of those with short lifetimes in the atmosphere compared to well-mixed greenhouse gases, and are also referred to as near-term climate forcers. This set of compounds includes methane (CH4), which is also a well-mixed greenhouse gas, as well as ozone (O3) and aerosols, or their precursors, and some halogenated species that are not well-mixed greenhouse gases. These compounds do not accumulate in the atmosphere at decadal to centennial time scales, and so their effect on climate is predominantly in the first decade after their emission, although their changes can still induce long-term climate effects such as sea level change. Their effect can be cooling or warming. A subset of exclusively warming short-lived climate forcers is referred to as short-lived climate pollutants. See also Long-lived climate forcers (LLCF). Short-lived climate pollutants (SLCP) See Short-lived climate forcers (SLCF). Sink A reservoir (natural or human, in soil, ocean, and plants) where a greenhouse gas, an aerosol or a precursor of a greenhouse gas is stored. Note that UNFCCC Article 1.8 refers to a sink as any process, activity or mechanism which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere. See also Uptake. Small island developing states (SIDS) Small island developing states (SIDS), as recognised by the United Nations OHRLLS (Office of the High Representative for the Least Developed Countries, Landlocked Developing Countries and Small Island Developing States), are a distinct group of developing countries facing specific social, economic and environmental vulnerabilities (UN-OHRLLS, 2011). They were recognized as a special case both for their environment and development at the Rio Earth Summit in Brazil in 1992. Fifty-eight countries and territories are presently classified as SIDS by the UN OHRLLS, with 38 being UN member states and 20 being Non-UN Members or Associate Members of the Regional Commissions (UN-OHRLLS, 2018). Social cost of carbon (SCC) The net present value of aggregate climate damages (with overall harmful damages expressed as a number with positive sign) from one more tonne of carbon in the form of carbon dioxide (CO2), conditional on a global emissions trajectory over time. Social costs The full costs of an action in terms of social welfare losses, including external costs associated with the impacts of this action on the environment, the economy (GDP, employment) and on the society as a whole. Social-ecological systems An integrated system that includes human societies and ecosystems, in which humans are part of nature. The functions of such a system arise from the interactions and interdependence of the social and ecological subsystems. The system’s structure is characterized by reciprocal feedbacks, emphasising that humans must be seen as a part of, not apart from, nature. This definition builds from Arctic Council (2016) and Berkes and Folke (1998). Social inclusion A process of improving the terms of participation in society, particularly for people who are disadvantaged, through enhancing opportunities, access to resources, and respect for rights (UN DESA, 2016). Social justice See Justice. Social learning A process of social interaction through which people learn new behaviours, capacities, values and attitudes. Social value of mitigation activities (SVMA) Social, economic and environmental value of mitigation activities that include, in addition to their climate benefits, their co-benefits to adaptation and sustainable development objectives. Societal (social) transformation See Transformation. Socio-economic scenario A scenario that describes a possible future in terms of population, gross domestic product (GDP), and other socio-economic factors relevant to understanding the implications of climate change. See also Baseline scenario, Emission scenario, Mitigation scenario and Pathways. Socio-technical transitions Socio-technical transitions are where technological change is associated with social systems and the two are inextricably linked. Soil carbon sequestration (SCS) Land management changes which increase the soil organic carbon content, resulting in a net removal of CO2 from the atmosphere. Soil moisture Water stored in the soil in liquid or frozen form. Rootzone soil moisture is of most relevance for plant activity. Solar radiation management See Solar radiation modification (SRM). Solar radiation modification (SRM) Solar radiation modification refers to the intentional modification of the Earth’s shortwave radiative budget with the aim of reducing warming. Artificial injection of stratospheric aerosols, marine cloud brightening and land surface albedo modification are examples of proposed SRM methods. SRM does not fall within the definitions of mitigation and adaptation (IPCC, 2012b, p. ). Note that in the literature SRM is also referred to as solar radiation management or albedo enhancement.


Stabilization (of GHG or CO2-equivalent concentration) A state in which the atmospheric concentrations of one greenhouse gas (GHG) (e.g., carbon dioxide) or of a CO2-equivalent basket of GHGs (or a combination of GHGs and aerosols) remains constant over time. Stranded assets Assets exposed to devaluations or conversion to ‘liabilities’ because of unanticipated changes in their initially expected revenues due to innovations and/or evolutions of the business context, including changes in public regulations at the domestic and international levels. Stratosphere The highly stratified region of the atmosphere above the troposphere extending from about 10 km (ranging from 9 km at high latitudes to 16 km in the tropics on average) to about 50 km altitude. See also Atmosphere, and Troposphere. Sub-national actor Sub-national actors include state/provincial, regional, metropolitan and local/municipal governments as well as nonparty stakeholders, such as civil society, the private sector, cities and other sub-national authorities, local communities and indigenous peoples. Substantive rights See Human rights. Supply-side measures See Demand- and supply-side measures. Surface temperature See Global mean surface temperature (GMST), Land surface air temperature, Global mean surface air temperature (GSAT) and Sea surface temperature (SST). Sustainability A dynamic process that guarantees the persistence of natural and human systems in an equitable manner. Sustainable development (SD) Development that meets the needs of the present without compromising the ability of future generations to meet their own needs (WCED, 1987) and balances social, economic and environmental concerns. See also Sustainable Development Goals (SDGs) and Development pathways (under Pathways). Sustainable Development Goals (SDGs) The 17 global goals for development for all countries established by the United Nations through a participatory process and elaborated in the 2030 Agenda for Sustainable Development, including ending poverty and hunger; ensuring health and well-being, education, gender equality, clean water and energy, and decent work; building and ensuring resilient and sustainable infrastructure, cities and consumption; reducing inequalities; protecting land and water ecosystems; promoting peace, justice and partnerships; and taking urgent action on climate change. See also Sustainable development (SD). Technology transfer The exchange of knowledge, hardware and associated software, money and goods among stakeholders, which leads to the spread of technology for adaptation or mitigation. The term encompasses both diffusion of technologies and technological cooperation across and within countries. Temperature overshoot The temporary exceedance of a specified level of global warming, such as 1.5°C. Overshoot implies a peak followed by a decline in global warming, achieved through anthropogenic removal of CO2 exceeding remaining CO2 emissions globally. See also Overshoot pathways and Non-overshoot pathways (both under Pathways). Tipping point A level of change in system properties beyond which a system reorganizes, often abruptly, and does not return to the initial state even if the drivers of the change are abated. For the climate system, it refers to a critical threshold when global or regional climate changes from one stable state to another stable state. See also Irreversibility. Transformation A change in the fundamental attributes of natural and human systems. Societal (social) transformation A profound and often deliberate shift initiated by communities toward sustainability, facilitated by changes in individual and collective values and behaviours, and a fairer balance of political, cultural, and institutional power in society. Transformation pathways See Pathways. Transformational adaptation See Adaptation. Transformative change A system-wide change that requires more than technological change through consideration of social and economic factors that, with technology, can bring about rapid change at scale. Transient climate response See Climate sensitivity. Transient climate response to cumulative CO2 emissions (TCRE) The transient global average surface temperature change per unit cumulative CO2 emissions, usually 1000 GtC. TCRE combines both information on the airborne fraction of cumulative CO2 emissions (the fraction of the total CO2 emitted that remains in the atmosphere, which is determined by carbon cycle processes) and on the transient climate response (TCR). See also Transient climate response (under Climate sensitivity). Transit-oriented development (TOD) An approach to urban development that maximizes the amount of residential, business and leisure space within walking distance of efficient public transport, so as to enhance mobility of citizens, the viability of public transport and the value of urban land in mutually supporting ways. Transition The process of changing from one state or condition to another in a given period of time. Transition can be in individuals, firms, cities, regions and nations, and can be based on incremental or transformative change. Tropical cyclone The general term for a strong, cyclonic-scale disturbance that originates over tropical oceans. Distinguished from weaker systems (often named tropical disturbances or depressions) by exceeding a threshold wind speed. A tropical storm is a tropical cyclone with one-minute average surface winds between 18 and 32 m s-1. Beyond m s-1, a tropical cyclone is called a hurricane, typhoon, or cyclone, depending on geographic location. See also Extratropical cyclone. Troposphere The lowest part of the atmosphere, from the surface to about 10 km in altitude at mid-latitudes (ranging from 9 km at high latitudes to 16 km in the tropics on average), where clouds and weather phenomena occur. In the troposphere, temperatures generally decrease with height. See also Atmosphere and Stratosphere. Uncertainty A state of incomplete knowledge that can result from a lack of information or from disagreement about what is known or even knowable. It may have many types of sources, from imprecision in the data to ambiguously defined concepts or terminology, incomplete understanding of critical processes, or uncertain projections of human behaviour. Uncertainty can therefore be represented by quantitative measures (e.g., a probability density function) or by qualitative statements (e.g., reflecting the judgment of a team of experts) (see Moss and Schneider, 2000; IPCC, 2004; Mastrandrea et al., 2010). See also Confidence and Likelihood. United Nations Framework Convention on Climate Change (UNFCCC) The UNFCCC was adopted in May 1992 and opened for signature at the 1992 Earth Summit in Rio de Janeiro. It entered into force in March 1994 and as of May 2018 had 197 Parties (196 States and the European Union). The Convention’s ultimate objective is the ‘stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate


system.’ The provisions of the Convention are pursued and implemented by two treaties: the Kyoto Protocol and the Paris Agreement. See also Kyoto Protocol and Paris Agreement. Uptake The addition of a substance of concern to a reservoir. See also Carbon sequestration and Sink. Vulnerability The propensity or predisposition to be adversely affected. Vulnerability encompasses a variety of concepts and elements including sensitivity or susceptibility to harm and lack of capacity to cope and adapt. See also Exposure, Hazard and Risk. Water cycle See Hydrological cycle. Well-being A state of existence that fulfils various human needs, including material living conditions and quality of life, as well as the ability to pursue one’s goals, to thrive, and feel satisfied with one’s life. Ecosystem well-being refers to the ability of ecosystems to maintain their diversity and quality. Zero emissions commitment See Climate change commitment.
 G.1
GLOSSARY
Glossary
G.2 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
Accuracy
A relative measure of the exactness of an emission or removal estimate. Estimates should be accurate in the sense that they are systematically neither over nor under true emissions or removals, so far as can be judged.
Activity
A practice or ensemble of practices that take place on a delineated area over a given period of time.
Activity data
Data on the magnitude of a human activity resulting in emissions or removals taking place during a given period of time. Data on energy use, metal production, land areas, management systems, lime and fertilizer use and waste arisings are examples of activity data.
Agricultural pond
An artificial storage containing water for agricultural (irrigation) or pastoral (stock watering) uses. They are typically unlined and constructed using a combination of earthen embankments and the natural topography on the landscape. They can range in size from very small farm dams (< 50 m2) to very large (> 10 km2).
Allochthonous
Material or formation originating outside the water body.
Allometric model
A formula that quantitatively describes an allometric relationship.
Allometry
The relative dimensional relationships between body parts that grow at different rates.
Anaerobic
Conditions in which oxygen is not readily available. These conditions are important for the production of methane emissions. Whenever organic material decomposes in anaerobic conditions (in landfills, flooded rice fields, etc.) methane is likely to be formed.
Andosol
A soil developed in volcanic ash. Generally andosols have good drainage and are prone to fertility problems.
Approaches to consistent representation of lands
Approach 1: Represents land-use area totals within a defined spatial unit, which is often defined by political boundaries, such as a country, province or municipality.
Approach 2: The essential feature of Approach 2 is that it provides an assessment of both the net losses or gains in the area of specific land-use categories and what these conversions represent (i.e., changes both from and to a category). Thus, Approach 2 differs from Approach 1 in that it includes information on conversions between categories, but is still only tracking those changes without spatially-explicit location data, often based on political boundaries (i.e., locations of specific land-use and land-use conversions are not known).
Approach 3: The key defining characteristic of Approach 3 is that it is both spatially and temporally consistent and explicit. Sample-based, survey-based and wall-to-wall methods can be considered Approach 3 depending on the design of the sampling/mapping program and the way the data is processed and analysed.
Aquaculture pond
An artificial storage containing water for the production of aquatic animals or plants. They are typically unlined and constructed using a combination of earthen embankments and the natural topography on the landscape. They can range in size from (< 50 m2) to (> 10 km2).
Arithmetic mean
The sum of the values divided by the number of values.
Auto producer
An enterprise which generates electricity or heat for its own use and/or sells it as a secondary activity i.e., not as its main business.
Autochthonous
Material or formation originating from inside the water body.
 G.3
Back-casting
The opposite of forecasting. Predicting conditions in the past from current conditions.
Backflows
By-product oils from petrochemical processing of refinery products which are generally returned to the refinery for further processing into petroleum products.
Base year
The starting year for the inventory. Currently this is typically 1990.
Benthic chlorophyll
An indicator of the eutrophication status of a water body based on the presence of microalgae at the sediment-water interface at the bottom of the water body.
Bias
A systematic error of the observation and estimation method, whose magnitude in most cases is unknown. It can be introduced by using measuring equipment that is improperly calibrated, by selecting items from a wrong population or by favouring certain elements of a population, etc. For example: Estimating the total fugitive emission from gas transport and distribution using only measurements of leakage from high/medium pressure pipelines can lead to bias if the leakage in the lower pressure distribution network (which is significantly more difficult to measure) is neglected.
Biochar
For the purpose of this report, biochar is defined as a solid material generated by heating biomass to a temperature in excess of 350 °C under conditions of controlled and limited oxidant concentrations to prevent combustion. These processes can be classified as either pyrolysis (in which oxidants are excluded), or gasification (in which oxidant concentrations are low enough to generate syngas).
Bioenergy
Energy derived from any form of biomass.
Biofuels
Any fuels derived from biomass, either deliberately grown or from waste products. Peat is not considered a biofuel in these guidelines due to the length of time required for peat to re-accumulate after harvest.
Biogenic carbon
Carbon derived from biogenic (plant or animal) sources excluding fossil carbon. Note that peat is treated as a fossil carbon in these guidelines as it takes so long to replace harvested peat.
Biological treatment of waste
Composting and anaerobic digestion of organic wastes, such as food waste, garden/park waste and sludge, to reduce volume in the waste material, stabilisation of waste, and destruction of pathogens in the waste material. This includes mechanical-biological treatment.
Biomass
(1) The total mass of living organisms in a given area or of a given species usually expressed as dry weight. Includes above and below ground living biomass.
(2) Organic matter consisting of or recently derived from living organisms (especially regarded as fuel) excluding peat. Includes products, by-products and waste derived from such material.
Blowing agent (for foam production)
A gas, volatile liquid, or chemical that generates gas during the foaming process. The gas creates bubbles or cells in the plastic structure of a foam.
Bootstrap technique
Bootstrap technique is a type of computationally intensive statistical method which uses repeated resampling with replacement from a set of data to assess variability of parameter estimates. Bootstrap technique is a specific case of a Monte Carlo method.
Boreal
See polar/boreal.
Glossary
G.4 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
Calcium carbide
Calcium carbide is used in the production of acetylene, in the manufacture of cyanamide (a minor historical use), and as a reductant in electric arc steel furnaces. It is made from calcium carbonate (limestone) and carbon-containing reductant (e.g., petroleum coke).
Canal
An artificial waterway typically constructed with a uniform cross-section to provide navigation or to transport water for irrigation, hydropower, town water supplies, etc. They may be earthen structures or they may have concrete linings. “Canals are generally long and narrow, with a uniform width and depth, and have a single outlet.” <<https://www.ramsar.org/news/ramsar-topics-report-on-canal-estates>>
Carbon budget
The balance of the exchanges of carbon between carbon pools or within one specific loop (e.g., atmosphere – biosphere) of the carbon cycle. This is a generic definition of “carbon budget” in the context of national greenhouse gas inventories. This term may be defined with other specific meaning in the other context. (For example, see the Glossary of IPCC Special Report “Global Warming of 1.5°C”).
Carbon dioxide equivalent emission
The amount of carbon dioxide (CO2) emission that would cause the same integrated radiative forcing or temperature change, over a given time horizon, as an emitted amount of a greenhouse gas (GHG) or a mixture of GHGs. There are a number of ways to compute such equivalent emissions and choose appropriate time horizons. Most typically, the CO2-equivalent emission is obtained by multiplying the emission of a GHG by its global warming potential (GWP) for a 100-year time horizon.
Carbon sequestration
The process of storing carbon in a carbon pool.
Category
Categories are subdivisions of the four main sectors Energy; Industrial Processes and Product Use (IPPU); Agriculture, Forestry and Other Land Use (AFOLU); and Waste. Categories may be further divided into sub-categories. For details, see Chapter 8 of Volume 1.
Census
A census is a survey conducted on the full set of observation objects belonging to a given population or universe.
Channel
A generic term for a waterway that encompasses creeks, streams, rivers, canals, ditches etc., as applied in the AFOLU sector for national greenhouse gas inventories.
Chlorofluorocarbons (CFCs)
Halocarbons containing only chlorine, fluorine, and carbon atoms. CFCs are both ozone-depleting substances (ODSs) and greenhouse gases.
Chronosequence
Chronosequences in this report are used in the context of the AFOLU sector, and consist of a temporal sequence in land use or management, for example, years since deforestation, which are used to evaluate change over time. Efforts are made to control all other between-site differences (e.g., by selecting areas with similar soil type, topography, previous vegetation). Chronosequences are often used as a surrogate for experimental studies or measurements repeated over time at the same location.
Climate sub-domain
A subset of a climate zone into which lands may be grouped for the purposes of inventory calculations. Used to provide finer resolution of climate gradients within one of the six climate zones.
Co-digestate
Supplemental material added to anaerobic digesters, in addition to the main digestion material (manure in the case of agricultural digesters) to increase methane yield.
 G.5
Coefficient of variation
Statistical definition: The coefficient of variation, vx is the ratio of the population standard deviation, σx, and mean, μx, where vx = σx /μx. It also frequently refers to the sample coefficient of variation, which is the ratio of the sample standard deviation and sample mean.1
Cogeneration
See: Combined Heat and Power (CHP) generation.
Combined heat and power (CHP)
Combined heat and power (CHP), also known as cogeneration, is the simultaneous production of both electricity and useful heat for application by the producer or to be sold to other users with the aim of better utilisation of the energy used. Public utilities may utilise part of the heat produced in power plants and sell it for public heating purposes. Industries as auto-producers may sell part of the excess electricity produced to other industries or to electric utilities.
Comparability
Comparability means that estimates of emissions and removals reported by countries in inventories are comparable among countries. For this purpose, countries should use agreed methodologies and formats for estimating and reporting inventories.
Completeness
Completeness means that an inventory covers all sources and sinks and gases included in the IPCC Guidelines for the full geographic coverage in addition to other existing relevant source/sink categories which are specific to individual countries (and therefore may not be included in the IPCC Guidelines).
Confidence
The term ‘confidence’ is used to represent trust in a measurement or estimate. Having confidence in inventory estimates does not make those estimates more accurate or precise; however, it will eventually help to establish a consensus regarding whether the data can be applied to solve a problem. This usage of confidence differs substantially from the statistical usage in the term confidence interval.
Confidence interval
A confidence interval (CI) is a type of interval estimate, computed from the statistics of the observed/estimated data, that might contain the true value of an unknown population parameter. The interval has an associated confidence level that quantifies the level of confidence that the parameter lies in the interval. Most commonly, the 95 per cent confidence level is used.
Consistency
Consistency means that an inventory is internally consistent in all its elements over a period of years. An inventory is consistent if the same methodologies are used for the base year and all subsequent years and if consistent data sets are used to estimate emissions or removals from sources or sinks. An inventory using different methodologies for different years can be considered to be consistent if it has been estimated in a transparent manner taking into account the guidance in Volume 1 on good practice in time series consistency.
Correlation
Mutual relationship between two quantities. See correlation coefficient.
Correlation coefficient
A number lying between –1 and +1, which measures the mutual relationship between two variables that are observed together. A value of +1 means that the variables have a perfect linear relationship; a value of –1 means that there is a perfect inverse linear relation; and a value of 0 means that there is no straight line relation. It is defined as the covariance of the two variables divided by the product of their standard deviations.
Country-specific data
Data for either activities or emission factors that are based on research carried out on sites either in that country or otherwise representative of that country.
1 ‘Coefficient of variation’ is the term, which is frequently replaced by ‘error’ in a statement like ‘the error is 5%’.
Glossary
G.6 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
Cruise
(When applied to aircraft) All aircraft activities that take place at altitudes above 914 metres (3,000 feet) including any additional climb or descent operations above this altitude. There is no upper limit.
Dam
An artificial structure that is barrier used to hold back water in a reservoir. Typically constructed with mineral sediment or concrete.
Degassing emissions
Elevated gas emissions that occur as water is released from a dam and experiences sudden changes in pressure, temperature and turbulence. These changes cause air-water exchange processes to occur at much greater rates than in surface waters as the released water approaches a new equilibrium with the environment downstream following Le Chatelier's principle. In the case of dams the change in the hydrostatic pressure before and after water passing through turbines affects this balance.
Also, water released from dams is typically released into a stilling basin designed to dissipate much of the turbulent energy of the flow in order to prevent excessive bank erosion in the natural river channel downstream. The increased water column turbulence greatly increases the air-water gas transfer rate for a given dissolved gas concentration. In some cases, water may be discharged through needle valves into the air, which provides very high air-water contact area leading to rapid gas release.
Decision tree
A decision tree is a flow chart describing the specific ordered steps which need to be followed to develop an inventory or an inventory component in accordance with the principles of good practice.
Denitrification
The microbially facilitated reduction of nitrates or nitrites to molecular nitrogen (N2) through which the nitrogen is emitted from the substrate to the atmosphere.
Diffusive emission
The gas flux across the air-water interface governed by diffusion. For measuring diffusive fluxes, the most popular method employs floating chambers. Frequently estimated using the Thin Boundary Layer model of gas transfer.
Displaced emission
An emission of greenhouse gases that has been relocated in space (and possibly in time) but unchanged in quantity. For example, remineralisation and emission of CO2 of 1 kg of soil C assumed to occur in an agricultural field may actually occur downstream in a river, reservoir or ocean if that 1 kg of soil C is carried into the stream network as a consequence of rainfall. The carbon is still converted to CO2 but enters the atmosphere at a location downstream of the carbon source.
Dissolved Inorganic Carbon (DIC)
Sum of all inorganic carbon species in solution (e.g. carbonate, bicarbonate, carbonic acid, carbon dioxide).
Dissolved Organic Carbon (DOC)
Organic carbon remaining in solution after filtering the sample, typically using a 0.45 micrometre filter.
Distribution function
A distribution function or cumulative distribution function F(x) for a random variable X specifies the probability P(X ≤ x) that X is less than or equal to x.
Ditch
A long, narrow excavation dug in the earth, typically unlined, often with a uniform cross-section. They are most often used to provide drainage alongside roadways and from agricultural fields and to convey water for irrigation.
Downstream emissions
The total greenhouse gas emissions that occur downstream of a dam including both degassing emissions and the diffusive emission.
Drainage channel
A ditch used for drainage.
 G.7
Drawdown zone
The area around the perimeter of a reservoir or pond that is intermittently exposed to the air as a result of water level changes.
Ebullitive emission
The flux of gas carried by bubbles from sediments through to the water column to the atmosphere.
Eddy flux measurement
The measurement of material fluxes by correlating high-frequency turbulent velocity fluctuations with turbulent concentration fluctuations. Also referred to as eddy correlation i.e. micrometeorological method that uses differences in concentration associated with turbulence in the air to quantify net vertical gas exchange.
Emission factor
A coefficient that quantifies the emissions or removals of a gas per unit activity. Emission factors are often based on a sample of measurement data, averaged to develop a representative rate of emission for a given activity level under a given set of operating conditions.
Emissions
The release of greenhouse gases and/or their precursors into the atmosphere over a specified area and period of time. (UNFCCC Article 1.4)
Energy recovery
A form of resource recovery in which the organic fraction of waste is converted to some form of usable energy. Recovery may be achieved through the combustion of processed or raw refuse to produce steam through the pyrolysis of refuse to produce oil or gas; and through the anaerobic digestion of organic wastes to produce methane gas.
Enhanced coal bed methane (recovery)
Increased CH4 recovery produced by the injection of CO2 into coal seams.
Epilimnetic
Pertaining to the epilimnion of a stratified water body.
Epilimnion
The uppermost region of a density-stratified reservoir. Frequently defined as the region above the strongest temperature gradient in the water column. It always includes, but is not limited to, the surface mixing layer – the isothermal region of actively turbulent water just below the air-water interface.
Estimation
The process of calculating emissions and/or removals.
Eutrophication
Natural or anthropogenic process of nutrient enrichment of a water body which leads to increases in algal biomass.
Evaporative emissions
Evaporative emissions fall within the class of fugitive emissions and are released from area (rather than point) sources. These are often emissions of Non-Methane Volatile Organic Compounds (NMVOCs), and are produced when the product is exposed to the air – for example in the use of paints or solvents.
Excluded carbon
Carbon in non-energy uses of fossil fuels (feed stocks, reductant and non-energy products) excluded from fuel combustion.
Expert judgement
A carefully considered, well-documented qualitative or quantitative judgement made in the absence of unequivocal observational evidence by a person or persons who have a demonstrable expertise in the given field.
Feedstock
Fossil fuels used as raw materials in chemical conversion processes to produce primarily organic chemicals and, to a lesser extent, inorganic chemicals.
Glossary
G.8 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
First use
Distinguishes first uses (and related emissions) from later non-energy uses of fossil fuels. For example, first-use emissions from lubricants are those which take place as a result of oxidation during use as a lubricant. Used lubricants may be used subsequently for heat raising as waste oils.
Flaring
All burning of natural gas/vapour streams and hydrocarbon liquids by flares as a waste disposal option rather than for the production of useful heat or power.
Floating chamber
Closed container that floats on the surface of the water used to quantify greenhouse gas emissions from the water surface. The time-dependent change in gas concentration within the floating chamber is a direct measurement of the gas flux.
Flood control
The operation of a reservoir to reduce peaks in river discharge.
Flow rate
The volume of water or gas passing through an imaginary plane at an instant of time [units are length3 time-1; e.g., m3 s-1, ft3 s-1, ML d-1, Ln min-1].
Fluorocarbons
Halocarbons containing fluorine atoms, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs).
Flux
(1) The rate of flow of any liquid or gas, across a given area; the amount of this crossing a given area in a given time. E.g., "Flux of CO2 absorbed by forests".
(2) Raw materials, such as limestone, dolomite, lime, and silica sand, which are used to reduce the heat or other energy requirements of thermal processing of minerals (such as the smelting of metals). Fluxes also may serve a dual function as a slagging agent.
Forest Land
This category includes all land with woody vegetation consistent with thresholds used to define Forest Land in the national greenhouse gas inventory. It also includes systems with a vegetation structure that currently fall below, but in situ could potentially reach the threshold values used by a country to define the Forest Land category.
Fossil carbon
Carbon derived from fossil fuel or other fossil source.
Fuel
Any substance burned as a source of energy such as heat or electricity. See also Primary Fuels and Secondary Fuels.
Fuel combustion
Within the Guidelines fuel combustion is the intentional oxidation of materials within an apparatus that is designed to provide heat or mechanical work to a process, or for use away from the apparatus.
Fuel wood
Wood used directly as fuel.
Fugitive Emissions (oil and natural gas systems)
The intentional or unintentional release of greenhouse gases that occur during the exploration, processing and delivery of fossil fuels to the point of final use. This excludes greenhouse gas emissions from fuel combustion for the production of useful heat or power. It encompasses venting, flaring, and leaks.
Funnel trap
A device deployed underwater to capture bubbles.
 G.9
Global warming potential
Global Warming Potentials (GWP) are calculated as the ratio of the radiative forcing of one kilogramme greenhouse gas emitted to the atmosphere to that from one kilogramme CO2 over a period of time (e.g., 100 years).
Good Practice
"Good practice" is a key concept for inventory compilers to follow in preparing national greenhouse gas inventories. The key concept does not change in the 2019 Refinement. The term "good practice" has been defined, since 2000 when this concept was introduced2, as "a set of procedures intended to ensure that greenhouse gas inventories are accurate in the sense that they are systematically neither over- nor underestimates so far as can be judged, and that uncertainties are reduced so far as practicable". This definition has gained general acceptance amongst countries as the basis for inventory development and its centrality has been retained for the 2019 Refinement. Certain terms in the definition have been updated based on feedback from the statistics community, such that this definition can be also understood as "a set of procedures intended to ensure that greenhouse gas inventories are accurate in the sense that they are systematically neither over- nor underestimates so far as can be judged, and that they are precise so far as practicable" in the context of refinement of Chapter 3 of Volume 13.
Good Practice covers choice of estimation methods appropriate to national circumstances, quality assurance and quality control at the national level, quantification of uncertainties and data archiving and reporting to promote transparency.
Ground truth
A term used for data obtained by measurements on the ground, usually as validation for remote sensing, e.g., satellite data.
Harvested wood products
Harvested wood products (HWP) according to the Good Practice Guidance for Land Use, Land-Use Change and Forestry (2003) and the 2006 IPCC Guidelines refer to wood and paper products, and include i) wood products in use (i.e. wood utilised as a material); ii) wood biomass used for energy purposes and iii) wood biomass in solid waste disposal sites.
Hydrocarbon
Strictly defined as molecules containing only hydrogen and carbon. The term is often used more broadly to include any molecules in petroleum which may also contain S, N, or O. An unsaturated hydrocarbon is any hydrocarbon containing olefinic, acetylenic, or aromatic structures.
Hydrochlorofluorocarbons (HCFCs)
Halocarbons containing only hydrogen, chlorine, fluorine and carbon atoms. Because HCFCs contain chlorine, they contribute to ozone depletion. They are also greenhouse gases.
Hydrofluorocarbons (HFCs)
Halocarbons containing only hydrogen, fluorine and carbon atoms. Because HFCs contain no chlorine, bromine, or iodine, they do not deplete the ozone layer. Like other halocarbons, they are potent greenhouse gases.
Hydrofluoroethers (HFEs)
Chemicals composed of hydrogen, fluorine and carbon atoms, with ether structure. Because HFEs contain no chlorine, bromine, or iodine, they do not deplete the ozone layer. Like other halocarbons, they are potent greenhouse gases.
Hypolimnetic
Pertaining to the hypolimnion.
2 The definition was originally introduced with the Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories published in 2000.
3 In the 2006 IPCC Guidelines, the term “uncertainty” was used with two meanings – a general one which is associated with both accuracy and precision, and a specific one only as the inverse of precision. This definition text of “good practice” which uses the term “precise” instead of “uncertainties” overcomes inconsistencies with general IPCC definition for uncertainty, without changing the original concept of “good practice”.
Glossary
G.10 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
Hypolimnion
The region of colder water at the bottom of a thermally stratified water body. It lies below the metalimnion (or thermocline) – the region with the strongest temperature gradient – and it may contain a weak temperature gradient. In many reservoirs, the hypolimnion can be anoxic (no oxygen) for many months each year because vertical transport of dissolved gases from above occurs mainly by slow diffusive processes across the metalimnion. This can lead to the accumulation of large concentrations of dissolved CH4 released from the bottom sediments.
Hypoxia
Waterbodies where dissolved oxygen has become undersaturated due to natural and/or anthropogenic processes which have led to aerobic biological oxygen consumption rates greater than the rate of re-oxygenation.
Hypoxic
Depletion of dissolved oxygen in aquatic environments to levels that are detrimental or fatal to aerobic organisms often caused by eutrophication.
Independence
Two random variables are independent if there is a complete absence of association between how their sample values vary. The most commonly used measure of the lack of independence between two random variables is the correlation coefficient.
Inflow, in the context of water bodies
The water that enters a water body (e.g. pond, lake, reservoir). In addition to surface flows (streams, rivers), inflow may also include precipitation and groundwater inputs.
Irrigation channel
An open channel that transports water in order to irrigate agricultural land.
Key category
A key category is one that is prioritised within the national inventory system because its estimate has a significant influence on a country's total inventory of greenhouse gases in terms of the absolute level of emissions and removals, the trend in emissions and removals, or uncertainty in emissions or removals. Whenever the term key category is used, it includes both source and sink categories.
Key source
See key category.
Kilns
A tubular heating apparatus used in the manufacture of cement, lime and other materials. The calcination reaction may take place in the kiln itself, or, where so-equipped, it may partly or completely take place in a preheater and/or precalciner apparatus ahead of the kiln.
Land cover
Refers to the bio-physical coverage of land (e.g., bare soil, rocks, forests, buildings and roads or lakes).
Land use
A broad classification of land based on the activities and cover, and in this report refers specifically to six general types including Forest Land, Cropland, Grassland, Wetlands, Settlements and Other Land. Note that a specific parcel of land may have more than one land use, but it is generally the predominant land use that forms the basis for the classification. The land-uses may be considered as top-level categories for representing all land-use areas, with sub-divisions describing specific circumstances significant to emissions estimation.
Landfill gas
Municipal solid waste contains significant portions of organic materials that produce a variety of gaseous products when deposited, compacted, and covered in landfills. Anaerobic bacteria thrive in the oxygen-free environment, resulting in the decomposition of the organic materials and the production of primarily carbon dioxide and methane. Carbon dioxide is likely to leach out of the landfill because it is soluble in water. Methane, on the other hand, which is less soluble in water and lighter than air, is likely to migrate directly to the atmosphere.
 G.11
Large dams
A dam with a height of 15 metres or greater from lowest foundation to crest or a dam between 5 metres and 15 metres impounding more than 3 million cubic metres. (See International Commission On Large Dams Constitution, Page 3)
LTO (landing and take-off) cycle
All aircraft activities that occur under 914 metres (3 000 feet) including idling aircraft engines, taxi-out, take-off, climb up to 914 metres, descend, approach and taxi-in. Note: some gatherers of statistics count either single take-off or landing as one cycle; however, it is both one take-off and one landing that together define the LTO cycle.
Lubricants
Lubricants are hydrocarbons produced from distillate or residue, and they are mainly used to reduce friction between bearing surfaces. This category includes all finished grades of lubricating oil, from spindle oil to cylinder oil, and those used in greases, including motor oils and all grades of lubricating oil base stocks.
Managed land
Land where human interventions and practices have been applied to perform production, ecological or social functions. All land definitions and classifications should be specified at the national level, described in a transparent manner, and be applied consistently over time. Therefore, what is not defined as ‘managed land’ by a country should be classified as unmanaged.
Managed Land Proxy (MLP)
For the AFOLU Sector, anthropogenic greenhouse gas emissions and removals by sinks are defined as all those occurring on ‘managed land’. This approach, i.e., the use of managed land as a proxy for anthropogenic effects, was adopted in the Good Practice Guidance for Land Use, Land-Use Change and Forestry (2003) and that use is maintained in the 2019 Refinement.
Manure
Waste materials produced by domestic livestock (vegetative material such as green manures are considered to be crop residues or compost). The term ‘manure’ is used here collectively to include both dung and urine (i.e., the solids and the liquids) produced by livestock.
Mean
The mean is a value around which values sampled from a probability distribution tend to lie. The sample mean or arithmetic average is an estimator for the mean. It is an unbiased and consistent estimator of the population mean (expected value) and is itself a random variable with its own variance value. The sample mean is the sum of values divided by the number of values:
Σ=niixnx1 (xi, where i = 1,…., n are items of a sample).
Measurement-based approach
The use of direct measurements to compute GHG fluxes from a system.
Median
The median or population median is a value which divides the integral of a probability density function (PDF) into two halves. For symmetric PDFs, it equals the mean. The median is the 50th population percentile.
The sample median is an estimator of the population median. It is the value that divides an ordered sample into two equal halves. If there are 2n + 1 observations, the median is taken as the (n + 1)th member of the ordered sample. If there are 2n, it is taken as being halfway between the nth and (n + 1)th.
Methanogenic production
Production of methane by microorganisms (methanogenic bacteria) during the decomposition of organic matter.
Glossary
G.12 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
Mode
The mode of a distribution is the value which has the highest probability of occurrence. Distributions can have one or more modes. In practice, distributions with only one mode are usually encountered. In this case, the mode or population mode of a PDF is the measure of a value around which values sampled from a probability distribution tend to lie.
The sample mode is an estimator for the population mode calculated by subdividing the sample range into equal subclasses, counting how many observations fall into each class and selecting the centre point of the class (or classes) with the greatest number of observations.
Model
A model is a quantitatively-based or qualitatively-based abstraction of a real-world situation which may simplify or neglect certain features to better focus on its more important elements.
Example: the relationship that emissions equal an emission factor times an activity level is a simple model. The term ‘model’ is also often used in the sense of a computer software realisation of a model abstraction.
Model-based approach
The application of (typically) statistical or process-based models that employ indirect measurements to infer GHG fluxes from a system of interest. For example, a model-based estimate of a pollutant flux could be computed as the product of an assumed concentration and a measured flow rate, whereas the corresponding measurement-based estimate would use a measured concentration and a measured flow rate.
Monte Carlo method
In these Guidelines a Monte Carlo method is recommended to analyse the uncertainty of the inventory. The principle of Monte Carlo analysis is to perform the inventory calculation many times by computer, each time with the uncertain emission factors or model parameters and activity data chosen randomly (by the computer) within the distribution on uncertainties specified initially by the user. Uncertainties in emission factors and/or activity data are often large and may not have normal distributions. In this case the conventional statistical rules for combining uncertainties become very approximate. Monte Carlo analysis can deal with this situation by generating an uncertainty distribution for the inventory estimate that is consistent with the input uncertainty distributions on the emission factors, model parameters and activity data.
Non-energy products
Primary or secondary fossil fuels which are used directly for their physical or diluent properties. Examples are: lubricants, paraffin waxes, bitumen, and white spirits and mineral turpentine (as solvent).
Non-energy use
Within the Guidelines this term refers to the use of fossil fuels as Feedstock, Reductant or Non-energy products. However, the use of this term differs between countries and sources of energy statistics. In most energy statistics, e.g., of the International Energy Agency (IEA), fuel inputs of reductants to blast furnaces are not included but accounted for as inputs to a fuel conversion activity transforming coke and other inputs to blast furnace gas.
Non-marketed lime production
Lime production occurring at facilities where the primary purpose is the production of lime as an intermediate input: such as plants that produce steel, synthetic soda ash, calcium carbide, magnesia and magnesium metal, as well as copper smelter and sugar mills. The lime produced by these facilities is often used on site and thus is often not reported in national statistics. Also referred to as in-house lime production.
Non-Methane Volatile Organic Compounds (NMVOCs)
A class of emissions which includes a wide range of specific organic chemical substances. Non-Methane Volatile Organic Compounds (NMVOCs) play a major role in the formation of ozone in the troposphere (lower atmosphere). Ozone in the troposphere is a greenhouse gas. It is also a major local and regional air pollutant, causing significant health and environmental damage. Because they contribute to ozone formation, NMVOCs are considered "precursor" greenhouse gases. NMVOCs, once oxidized in the atmosphere, produce carbon dioxide.
 G.13
Normal distribution
The normal (or Gaussian) distribution has the probability density function (PDF) given in the following equation and is defined by two parameters (the mean μ and the standard σ deviation).
∞≤≤∞=−−xexfx-for ,21)(222) (σμπσ.
Nutrient loading
An increase in levels of nitrogen, phosphorus, and sulphur entering aquatic systems as a result of human activity occurring in the catchment.
Observational data
Observational data is empirical data from instrumental (usually monitoring equipment) or manual methods (through counts in a survey or census).
Off-gas
The exhaust gas from a chemical process (combustion or non-combustion). The off gas may be vented to the atmosphere, burned for energy recovery or flared (without energy recovery), or used as a feedstock for another chemical process. Secondary products may also be recovered from the off gas.
Open burning of waste
The combustion of unwanted combustible materials such as paper, wood, plastics, textiles, rubber, and other debris in the open or at an open dump site, where smoke and other emissions are released directly into the air without passing through a chimney or stack. Open burning can also include incineration devices that do not control the combustion air to maintain an adequate temperature and do not provide sufficient residence time for complete combustion.
Outflow, in the context of reservoirs
Water discharged from a dam.
Outflow area
The area where water is discharged immediate downstream of a dam. It is characterised by exceptionally high levels of turbulence in the water (see degassing emissions) that directly result from the operation of the dam.
Oxic
Containing dissolved oxygen.
Oxidation
Chemically transform of a substance by combining it with oxygen.
Oxycline
The region of high dissolved oxygen concentration change within the water column that separates oxic and anoxic regions.
Ozone-depleting substances (ODS)
A compound that contributes to stratospheric ozone depletion. Ozone-depleting substances (ODS) include CFCs, HCFCs, halons, methyl bromide, carbon tetrachloride, and methyl chloroform. ODS are generally very stable in the troposphere and only degrade under intense ultraviolet light in the stratosphere. When they break down, they release chlorine or bromine atoms, which then deplete ozone.
Pasture
Area covered with grass or other plants used or suitable for the grazing of livestock; grassland.
PDF
See Probability density function.
Peat
Soft, porous or compressed, sedimentary deposit of plant origin with high water content in the natural state (up to about 90 percent). Countries may define peat according to their national circumstances.
Glossary
G.14 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
Peatland
Peatlands are wetland ecosystems where soils are dominated by peat. In peatlands net primary production exceeds organic matter decomposition as a result of waterlogged conditions, which leads to the accumulation of peat.
Percentile
A percentile (or a centile) is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations fall.
Perfluorocarbons (PFCs)
Synthetically produced halocarbons containing only carbon and fluorine atoms. They are characterized by extreme stability, non-flammability, low toxicity, zero ozone depleting potential, and high global warming potential.
Plant-mediated emission
Flows of greenhouse gas emissions to the atmosphere that are influenced by plants, and such as the production, transport and oxidation of methane in wetland soils.
Polar/boreal, dry climate
Regions where mean annual temperature (MAT) is less than or equal to 0 oC, and the ratio of mean annual precipitation to potential evapotranspiration is less than or equal to 1.
Polar/boreal, moist climate
Regions where mean annual temperature (MAT) is less than or equal to 0 oC, and the ratio of mean annual precipitation to potential evapotranspiration is greater than 1.
Ponds
The water impounded behind a small dam (< 15 m high) or embankment.
Pool, carbon and nitrogen
A reservoir in the Earth system where elements, such as carbon and nitrogen, reside in various chemical forms for a period of time. An example is carbon and nitrogen pools in forest biomass, which are composed of various types of compounds synthesized by trees. A group of pools are linked in a cycle with flows among the pools influenced by both anthropogenic and non-anthropogenic processes.
An example is carbon and nitrogen pools in forest biomass, wood products, dead organic matter, soils and the atmosphere, in which flows are influenced by non-anthropogenic drivers such as plant production and microbial decomposition, as well as anthropogenic drivers such as fertilization, land use, tree harvest and product use. The units are in mass.
Population
The population is the totality of items under consideration. In the case of a random variable, the probability distribution is considered to define the population of that variable.
Precision
Closeness of agreement between independent results of measurements obtained under stipulated conditions. Better precision means less random error.
Primary fuels
Fuels which are extracted directly from natural resources. Examples are: crude oil, natural gas, coals, etc.
Process-based modelling
A mathematical modelling approach based on a theoretical understanding of fundamental ecological, biological, chemical, and physical processes. Typically using differential equations to represent the change over time of parameters of interest, it provides a useful framework to project specific responses to altered environmental conditions. For example, a process-based model might be used to quantify the delivery of organic matter delivered from the catchment and/or produced by primary production within a reservoir, its deposition onto a reservoir's sediment, the degradation of the organic matter aerobically to CO2 or anaerobically to CH4 over time, and the emission of these gases across the air-water interface.
 G.15
Probability
The probability of an event is a measure of the likelihood that the event will occur. The probability of any event can range from 0 to 1. The sum of probabilities of all sample points in a sample space is equal to 1.
Probability density function
A probability density function (PDF) is a function, whose value at any given sample (or point) in the sample space (the set of possible values taken by the random variable) can be interpreted as providing a relative likelihood that the value of the random variable would equal that sample.
Probability distribution
Statistical definition: A function giving the probability that a random variable takes any given value or belongs to a given set of values. The probability on the whole set of values of the random variable equals 1.
Process emissions
Emissions from industrial processes involving chemical transformations other than combustion.
Pumped storage reservoirs
Reservoirs at different elevations that are used to store energy by moving water from the lower to the higher elevation.
Quality Assurance
Quality Assurance (QA) activities include a planned system of review procedures conducted by personnel not directly involved in the inventory compilation/development process to verify that data quality objectives were met, ensure that the inventory represents the best possible estimate of emissions and sinks given the current state of scientific knowledge and data available, and support the effectiveness of the quality control (QC) programme.
Quality Control
Quality Control (QC) is a system of routine technical activities, to measure and control the quality of the inventory as it is being developed. The QC system is designed to:
(i) Provide routine and consistent checks to ensure data integrity, correctness, and completeness;
(ii) Identify and address errors and omissions;
(iii) Document and archive inventory material and record all QC activities.
QC activities include general methods such as accuracy checks on data acquisition and calculations and the use of approved standardised procedures for emission calculations, measurements, estimating uncertainties, archiving information and reporting. More detailed QC activities include technical reviews of source categories, activity and emission factor data, and methods.
RAMSAR
The Convention on Wetlands, called the Ramsar Convention, is an intergovernmental treaty that provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources.
Removals
Removal of greenhouse gases and/or their precursors from the atmosphere by a sink.
Reporting
The process of providing results of the inventory as described in Volume 1 Chapter 8.
Reservoir
(1) A component or components of the climate system where a greenhouse gas or a precursor of a greenhouse gas is stored. (UNFCCC Article 1.7)
(2) Water bodies regulated for human activities (energy production, irrigation, navigation, recreation etc.) where substantial changes in water area due to water level regulation may occur. The water impounded behind a dam.
(3) In the context of oil and natural gas systems, an underground formation where oil and gas has accumulated; consists of porous or fractured rock that holds oil and gas and a cap rock that prevents its escape.
Glossary
G.16 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories
Rice paddies
A flooded parcel of land used for growing semiaquatic rice. Paddy cultivation should not be confused with cultivation of deep water rice, which is grown in flooded conditions with water more than 50 cm (20 in) deep for at least a month.
River emissions
GHG emissions from the surface of a normally (in a hydraulic sense) flowing river downstream of the exceptionally turbulent region (see outflow area) immediately downstream of a dam. ‘Normal flow’ refers to the velocity of the flow being solely determined by channel shape and bed slope so that water column turbulence is produced predominantly by natural shear forces at the water-river bed interface.
Run-of-the-river reservoirs
Reservoirs in hydroelectric systems that harvest the energy from flowing water to generate electricity but cannot store more water than one day's annual mean inflow (i.e. annual mean flow / 365).
Secchi depth
A practical measure of aquatic turbidity (versus clarity) based on the depth at which a standard Secchi disc (created by Angelo Secchi) ceases to be visible from the surface of the water body.
Secondary fuels
Fuels manufactured from primary fuels. Examples are: cokes, motor gasoline and coke oven gas, blast furnace gas.
Sink
Any process, activity or mechanism which removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas from the atmosphere. (UNFCCC Article 1.8) Notation in the final stages of reporting is the negative (-) sign.
Soil carbon pool
A pool of carbon comprised of soil organic matter that is smaller than 2mm in size.
Source
Any process or activity which releases a greenhouse gas, an aerosol or a precursor of a greenhouse gas into the atmosphere. (UNFCCC Article 1.9) Notation in the final stages of reporting is the positive (+) sign.
Spillway
An engineered channel used to pass high flows safely past a dam when the reservoir water level is higher than the crest of the dam. Note that the maximum water level of a reservoir is frequently higher than the crest because of the use of gates that are on top of the crest.
Standard deviation
The population standard deviation is the positive square root of the variance. It is estimated by the sample standard deviation that is the positive square root of the sample variance.
Storage volume
The volume of water stored in a water body. The ‘active’ storage of a reservoir is the volume of water contained between the full supply level (the maximum level at which water may be stored indefinitely) and the lowest outlet level. The ‘dead’ storage is the volume of water that is below the lowest outlet and therefore cannot be routinely accessed for beneficial use. The ‘flood control’ storage is the volume of water contained between the full supply level and the top of gates (or other adjustable structures) located on top of the spillway and used to regulate the discharge of floodwaters. The total reservoir storage volume is the sum of dead storage, active storage, and flood control storage capacities.
Surrogate data
Surrogate data or so-called proxy data is data that is used in place of the actual data, where the specific data needed is unobtainable. Often surrogate data is needed to describe changes in an emission source over time, for example population change may be used to approximate change in waste arisings.
Survey
A survey is an investigation about the characteristics of a given population by means of collecting data from a sample of that population and estimating their characteristics through the systematic use of statistical methodology.
 G.17
Systematic and random errors
Systematic error (i.e., bias) is the difference between the true, but usually unknown, value of a quantity being estimated, and the mean observed value as would be estimated by the sample mean of an infinite set of observations. The random error of an individual measurement is the difference between an individual measurement and the above limiting value of the sample mean.
Systematic error
See systematic and random errors.
Temperate, cold dry climate
Areas where mean annual temperature (MAT) is between 0 – 10 oC, and the ratio of mean annual precipitation to potential evapotranspiration is less than or equal to 1.
Temperate, cold moist climate
Areas where mean annual temperature (MAT) is between 0 – 10 oC, and the ratio of mean annual precipitation to potential evapotranspiration is greater than 1.
Temperate, warm dry climate
Areas where mean annual temperature (MAT) is between 10 – 18 oC (or greater than 18 oC with more than 7 days of frost per year), and the ratio of mean annual precipitation to potential evapotranspiration is less than or equal to 1.
Temperate, warm moist climate
Areas where mean annual temperature (MAT) is between 10 – 18 oC (or greater than 18 oC with more than 7 days of frost per year), and the ratio of mean annual precipitation to potential evapotranspiration is greater than 1.
Thin boundary layer model
The thin boundary layer model expresses the flux of gas across an air-water interface as the product of a gas transfer velocity and the concentration change across the interface. It was originally developed by Liss and Slater (1974).
Tier
A tier represents a level of methodological complexity. Usually three tiers are provided. Tier 1 is the basic method, Tier 2 intermediate and Tier 3 most demanding in terms of complexity and data requirements. Tiers 2 and 3 are sometimes referred to as higher tier methods and are generally considered to be more accurate.
Time series
A time series is series of values which are affected by random processes and which are observed at successive (usually equidistant) points in time.
Transparency
Transparency means that the assumptions and methodologies used for an inventory should be clearly explained to facilitate replication and assessment of the inventory by users of the reported information. The transparency of inventories is fundamental to the success of the process for the communication and consideration of information.
Trend
The trend of a quantity measures its change over a time period, with a positive trend value indicating growth in the quantity, and a negative value indicating a decrease. It is defined as the ratio of the change in the quantity over the time period, divided by the initial value of the quantity, and is usually expressed either as a percentage or a fraction.

Trophic state
A measure of the biological productivity of a water body. It is usually characterized by some combination of nutrients, photosynthetic pigments (Chl-a) and/or water column optical properties. As the ambient nutrient levels increase, primary production (the algal population) increases and the water clarity decreases. As primary production increases, higher levels of biological production are supported and the trophic state increases.
Lakes or reservoirs are usually classified as being in one of four possible trophic states: oligotrophic, mesotrophic, eutrophic, or hypereutrophic. (see e.g., Carlson, 1977)
Oligotrophic: an oligotrophic lake or reservoir is characterised by low primary productivity, as a result of low nutrient content. (Chl-a ≤ 2.6 μg L-1.)
Mesotrophic: mesotrophic lakes or reservoirs are characterised with an intermediate level of productivity (2.6 μg L-1 < Chl-a ≤ 20 μg L-1.)
Eutrophic: a eutrophic lake, pond or reservoir with high biological productivity. Due to excessive nutrients, especially nitrogen and phosphorus, these water bodies are able to support an abundance of aquatic plants. (20 μg L-1 < Chl-a ≤ 56 μg L-1.)
Hypereutrophic: a hypereutrophic body of water experiences the highest levels of biological productivity. (56 μg L-1 < Chl-a)
Tropical, dry climate
Areas where mean annual temperature (MAT) is more than 18 oC, with no more than 7 days of frost, and mean annual precipitation less than or equal to 1000mm.
Tropical, moist climate
Areas where mean annual temperature (MAT) is more than 18 oC, with no more than 7 days of frost, and mean annual precipitation greater than 1000mm and less than or equal to 2000mm.
Tropical montane climate
Areas where mean annual temperature (MAT) is more than 18 oC, with no more than 7 days of frost, and an elevation greater than 1000m.
Tropical, wet climate
Areas where mean annual temperature (MAT) is more than 18 oC, with no more than 7 days of frost, and mean annual precipitation greater than 2000mm.
Unbiased estimator
An unbiased estimator is a statistic whose expected value equals the value of the parameter being estimated. Note that this term has a specific statistical meaning and that an estimate of a quantity calculated from an unbiased estimator may lack bias in the statistical sense, but may be biased in the more general sense of the word if the sample has been affected by unknown systematic error. Thus, in statistical usage, a biased estimator can be understood as a deficiency in the statistical evaluation of the collected data, and not in the data themselves or in the method of their measurement or collection. For example, the arithmetic mean (average) x is an unbiased estimator of the expected value (mean).
Uncertainty
Lack of knowledge of the true value of a variable that can be described as a probability density function characterizing the range and likelihood of possible values. Uncertainty depends on the analyst’s state of knowledge, which in turn depends on the quality and quantity of applicable data as well as knowledge of underlying processes and inference methods. (See Volume 1 Chapter 3.)
Uncertainty analysis
An uncertainty analysis of a model aims to provide quantitative measures of the uncertainty of output values caused by uncertainties in the model itself and in its input values, and to examine the relative importance of these factors.
Validation
Validation is the establishment of sound approach and foundation. In the context of emission inventories, validation involves checking to ensure that the inventory has been compiled correctly in line with reporting instructions and guidelines. It checks the internal consistency of the inventory. The legal use of validation is to give an official confirmation or approval of an act or product.
 G.19
Variability
This refers to observed differences attributable to true heterogeneity or diversity in a population. Variability derives from processes which are either inherently random or whose nature and effects are influential but unknown. Variability is not usually reducible by further measurement or study, but can be characterised by quantities such as the sample variance.
Verification
Verification refers to the collection of activities and procedures that can be followed during the planning and development, or after completion of an inventory that can help to establish its reliability for the intended applications of that inventory.
Typically, methods external to the inventory are used to check the truth of the inventory, including comparisons with estimates made by other bodies or with emission and uptake measurements determined from atmospheric concentrations or concentration gradients of these gases.
Watercourse
The channel that a flowing body of water follows.
Water residence time
The average amount of time that water spends in a particular system (lake, reservoir, etc.). Defined as the volume of the reservoir divided by the inflow.
Water withdrawal
The controlled release of water from a dam. Depending on the dam’s design, i.e. the number and level of discrete outlets, the withdrawn water may originate solely from specific regions of the water column, i.e. epilimnion, metalimnion and hypolimnion. The withdrawal region for a specific discharge depends strongly on the density stratification of the water body, the outlet dimensions, and the reservoir morphology.
Wetlands
This category includes land that is covered or saturated by water for all or part of the year (e.g., peatland) and that does not fall into the forest land, cropland, grassland or settlements categories. The category can be subdivided into managed and unmanaged according to national definitions. Wetlands occur over all climate zones and include reservoirs and other constructed waterbodies (e.g. agriculture and aquaculture ponds, canals and ditches and wetlands constructed for wastewater treatment) as managed sub-divisions. Managed wetlands may also include peatlands, riparian wetlands, forested swamps, marshes, playas, pans, salt lakes, brackish wetlands, salinas, and sabkhas, in addition to coastal wetlands, including mangroves, saltmarshes, tidal marshes and seagrass. Unmanaged wetlands include natural rivers, lakes and ponds and any wetlands that have not been directly modified by human activity based on the Managed Land Proxy.AI Annex I: Glossary
This annex should be cited as:
IPCC, 2019: Annex I: Glossary [van Diemen, R. (ed.)]. In: Climate Change and Land: an IPCC special report on climate
change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in
terrestrial ecosystems [P.R. Shukla, J. Skea, E. Calvo Buendia, V. Masson-Delmotte, H.-O. Pörtner, D. C. Roberts, P. Zhai,
R. Slade, S. Connors, R. van Diemen, M. Ferrat, E. Haughey, S. Luz, S. Neogi, M. Pathak, J. Petzold, J. Portugal Pereira,
P. Vyas, E. Huntley, K. Kissick, M. Belkacemi, J. Malley, (eds.)]. In press.
Coordinating Editor:
Renée van Diemen (The Netherlands/United Kingdom)
Editorial Team:
Tim Benton (United Kingdom), Eduardo Calvo (Peru), Annette Cowie (Australia), Valérie
Masson-Delmotte (France), Aziz Elbehri (Morocco), Karlheinz Erb (Italy), Giacomo Grassi (Italy/
European Union), J.B. Robin Matthews (United Kingdom), Hans-Otto Pörtner (Germany), Andy
Reisinger (New Zealand), Debra Roberts (South Africa), Priyadarshi Shukla (India), Andrey Sirin
(The Russian Federation), Jim Skea (United Kingdom), Murat Türkeş (Turkey), Nora M. Weyer
(Germany), Sumaya Zakieldeen (Sudan), Panmao Zhai (China)
Notes:
Note that subterms are in italics beneath main terms.
This glossary defines some specific terms as the Lead Authors intend them to be interpreted in
the context of this report. Blue, italicised words indicate that the term is defined in the Glossary.



.5°C pathway See Pathways.
Agenda for Sustainable Development A UN resolution
in September 2015 adopting a plan of action for people, planet and
prosperity in a new global development framework anchored in 17
Sustainable Development Goals (UN, 2015).
Acceptability of policy or system change The extent to
which a policy or system change is evaluated unfavourably or
favourably, or rejected or supported, by members of the general
public (public acceptability) or politicians or governments (political
acceptability). Acceptability may vary from totally unacceptable/fully
rejected to totally acceptable/fully supported; individuals may differ
in how acceptable policies or system changes are believed to be.
Acclimatisation A change in functional or morphological traits
occurring once or repeatedly (e.g., seasonally) during the lifetime
of an individual organism in its natural environment. Through
acclimatisation the individual maintains performance across a range
of environmental conditions. For a clear differentiation between
findings in laboratory and field studies, the term acclimation is used
in ecophysiology for the respective phenomena when observed in
well-defined experimental settings. The term (adaptive) plasticity
characterises the generally limited scope of changes in phenotype
that an individual can reach through the process of acclimatisation.
Activity A practice or ensemble of practices that take place on
a delineated area over a given period of time.
Activity data Data on the magnitude of a human activity resulting
in emissions or removals taking place during a given period of time. In
the Agriculture, Forestry and Other Land Use (AFOLU) sector, data on
area of different land uses, management systems, animal numbers,
lime and fertiliser use are examples of activity data.
Adaptability See Adaptive capacity.
Adaptation In human systems, the process of adjustment to
actual or expected climate and its effects, in order to moderate harm
or exploit beneficial opportunities. In natural systems, the process of
adjustment to actual climate and its effects; human intervention may
facilitate adjustment to expected climate and its effects.
Incremental adaptation
Adaptation that maintains the essence and integrity of a system or
process at a given scale (Park et al., 2012).
Transformational adaptation
Adaptation that changes the fundamental attributes of a socialecological
system in anticipation of climate change and its impacts.
Adaptation limits
The point at which an actor’s objectives (or system needs) cannot be
secured from intolerable risks through adaptive actions.
• Hard adaptation limit: No adaptive actions are possible to avoid
intolerable risks.
• Soft adaptation limit: Options are currently not available to
avoid intolerable risks through adaptive action.
See also Adaptation options, Adaptive capacity and Maladaptive
actions (Maladaptation).
Adaptation behaviour See Human behaviour.
Adaptation limits See Adaptation.
Adaptation options The array of strategies and measures
that are available and appropriate for addressing adaptation. They
include a wide range of actions that can be categorised as structural,
institutional, ecological or behavioural. See also Adaptive capacity,
and Maladaptive actions (Maladaptation).
Adaptation pathways See Pathways
Adaptive capacity The ability of systems, institutions, humans
and other organisms to adjust to potential damage, to take advantage
of opportunities, or to respond to consequences (IPCC, 2014; MA,
). See also Adaptation, Adaptation options, and Maladaptive
actions (Maladaptation).
Adaptive governance See Governance.
Adverse side-effect The negative effects that a policy or
measure aimed at one objective might have on other objectives,
without yet evaluating the net effect on overall social welfare.
Adverse side-effects are often subject to uncertainty and depend on,
among others, local circumstances and implementation practices. See
also Co-benefits and Risk.
Aerosol A suspension of airborne solid or liquid particles, with
a typical size between a few nanometres and 10 μm that reside in the
atmosphere for at least several hours. The term aerosol, which includes
both the particles and the suspending gas, is often used in this report
in its plural form to mean aerosol particles. Aerosols may be of either
natural or anthropogenic origin. Aerosols may influence climate in
several ways: through both interactions that scatter and/or absorb
radiation and through interactions with cloud microphysics and other
cloud properties, or upon deposition on snow or ice covered surfaces
thereby altering their albedo and contributing to climate feedback.
Atmospheric aerosols, whether natural or anthropogenic, originate
from two different pathways: emissions of primary particulate matter
(PM), and formation of secondary PM from gaseous precursors. The
bulk of aerosols are of natural origin. Some scientists use group
labels that refer to the chemical composition, namely: sea salt,
organic carbon, black carbon (BC), mineral species (mainly desert
dust), sulphate, nitrate, and ammonium. These labels are, however,
imperfect as aerosols combine particles to create complex mixtures.
See also Short-lived climate forcers (SLCF).
Afforestation Conversion to forest of land that historically has
not contained forests. [Note: For a discussion of the term forest and
related terms such as afforestation, reforestation and deforestation, in
the context of reporting and accounting Article 3.3 and 3.4 activities
under the Kyoto Protocol, see 2013 Revised Supplementary Methods
and Good Practice Guidance Arising from the Kyoto Protocol.] See
also Reforestation, Deforestation, Forest and Reducing Emissions
from Deforestation and Forest Degradation (REDD+).
Agreement In this report, the degree of agreement within the
scientific body of knowledge on a particular finding is assessed
based on multiple lines of evidence (e.g., mechanistic understanding,
theory, data, models, expert judgement) and expressed qualitatively
(Mastrandrea et al., 2010). See also Confidence, Likelihood,
and Uncertainty.

Glossary Annex I
AI
Agriculture, Forestry and Other Land Use (AFOLU) In the
context of national greenhouse gas (GHG) inventories under the
United Nations Convention on Climate Change (UNFCCC), AFOLU is
the sum of the GHG inventory sectors Agriculture and Land Use, Land-
Use Change and Forestry (LULUCF); see the 2006 IPCC Guidelines
for National GHG Inventories for details. Given the difference in
estimating the ‘anthropogenic’ carbon dioxide (CO2) removals
between countries and the global modelling community, the landrelated
net GHG emissions from global models included in this report
are not necessarily directly comparable with LULUCF estimates in
national GHG Inventories.
FOLU (Forestry and Other Land Use) – also referred to as LULUCF
The subset of AFOLU emissions and removals of greenhouse gases
(GHGs) resulting from direct human-induced land use, land-use
change, and forestry activities excluding agricultural emissions.
See also Land-Use Change (LUC) and Land Use, Land-Use Change and
Forestry (LULUCF).
Agrobiodiversity ‘The variety and variability of animals, plants
and micro-organisms that are used directly or indirectly for food
and agriculture, including crops, livestock, forestry and fisheries.
It comprises the diversity of genetic resources (varieties, breeds)
and species used for food, fodder, fibre, fuel and pharmaceuticals.
It also includes the diversity of non-harvested species that support
production (soil micro-organisms, predators, pollinators), and those
in the wider environment that support agro-ecosystems (agricultural,
pastoral, forest and aquatic) as well as the diversity of the agroecosystems’
(FAO, 2005).
Agroecology ‘The science and practice of applying ecological
concepts, principles and knowledge (i.e., the interactions of, and
explanations for, the diversity, abundance and activities of organisms)
to the study, design and management of sustainable agroecosystems.
It includes the roles of human beings as a central organism in
agroecology by way of social and economic processes in farming
systems. Agroecology examines the roles and interactions among
all relevant biophysical, technical and socioeconomic components of
farming systems and their surrounding landscapes’ (IPBES, 2019).
Agroforestry Collective name for land-use systems and
technologies where woody perennials (trees, shrubs, palms,
bamboos, etc.) are deliberately used on the same land-management
units as agricultural crops and/or animals, in some form of spatial
arrangement or temporal sequence. In agroforestry systems there
are both ecological and economical interactions between the
different components. Agroforestry can also be defined as a dynamic,
ecologically based, natural resource management system that,
through the integration of trees on farms and in the agricultural
landscape, diversifies and sustains production for increased social,
economic and environmental benefits for land users at all levels
(FAO, 2015a).
Air pollution Degradation of air quality with negative effects
on human health, the natural or built environment, due to the
introduction by natural processes or human activity in the atmosphere
of substances (gases, aerosols) which have a direct (primary
pollutants) or indirect (secondary pollutants) harmful effect. See also
Short-lived climate forcers (SLCF).
Albedo The proportion of sunlight (solar radiation) reflected by
a surface or object, often expressed as a percentage. Clouds, snow
and ice usually have high albedo; soil surfaces cover the albedo range
from high to low; vegetation in the dry season and/or in arid zones
can have high albedo, whereas photosynthetically active vegetation
and the ocean have low albedo. The Earth’s planetary albedo changes
mainly through varying cloudiness, snow, ice, leaf area and land
cover changes.
Ambient persuasive technology Technological systems
and environments that are designed to change human cognitive
processing, attitudes and behaviours without the need for the user’s
conscious attention.
Anomaly The deviation of a variable from its value averaged over
a reference period. See also Reference period.
Anthromes ‘Human systems, with natural ecosystems
embedded within them’ (Ellis and Ramankutty 2008). The anthrome
classification system is based on human population density and land
use, and comprises the following classes: dense settlements, villages,
croplands, rangeland, forested (then broadened to seminatural) and
wildlands (Ellis et al. 2010).
Anthropocene A proposed new geological epoch resulting from
significant human-driven changes to the structure and functioning of
the Earth System, including the climate system. Originally proposed
in the Earth System science community in 2000, the proposed new
epoch is undergoing a formalisation process within the geological
community based on the stratigraphic evidence that human activities
have changed the Earth System to the extent of forming geological
deposits with a signature that is distinct from those of the Holocene,
and which will remain in the geological record. Both the stratigraphic
and Earth System approaches to defining the Anthropocene consider
the mid-20th century to be the most appropriate starting date,
although others have been proposed and continue to be discussed.
The Anthropocene concept has been taken up by a diversity of
disciplines and the public to denote the substantive influence humans
have had on the state, dynamics and future of the Earth System. See
also Holocene.
Anthropogenic Resulting from or produced by human activities.
See also Anthropogenic emissions, and Anthropogenic removals.
Anthropogenic emissions Emissions of greenhouse gases
(GHGs), precursors of GHGs and aerosols caused by human activities.
These activities include the burning of fossil fuels, deforestation, land
use and land-use changes (LUC), livestock production, fertilisation,
waste management, and industrial processes. See also Anthropogenic,
and Anthropogenic removals.
Anthropogenic removals The withdrawal of greenhouse
gases (GHGs) from the atmosphere as a result of deliberate human
activities. These include enhancing biological sinks of CO2 and using
chemical engineering to achieve long term removal and storage.
Carbon capture and storage (CCS) from industrial and energy-related
sources, which alone does not remove CO2 from the atmosphere,
can help reduce atmospheric CO2 if it is combined with bioenergy
production (BECCS). [Note: In the 2006 IPCC Guidelines for National
GHG Inventories, which are used in reporting of emissions to the
UNFCCC, 'anthropogenic’ land-related GHG fluxes are defined as all


those occurring on 'managed land’, i.e. ‘where human interventions
and practices have been applied to perform production, ecological or
social functions’. However, some removals (e.g. removals associated
with CO2 fertilisation and N deposition) are not considered as
‘anthropogenic’, or are referred to as ‘indirect’ anthropogenic
effects, in some of the scientific literature assessed in this report. As
a consequence, the land-related net GHG emission estimates from
global models included in this report are not necessarily directly
comparable with LULUCF estimates in national GHG Inventories.
See also Anthropogenic emissions, Bioenergy with carbon dioxide
capture and storage (BECCS), Carbon dioxide capture and storage
(CCS) and Land use, Land-use change, and Forestry (LULUCF).
Aridity The state of a long-term climatic feature characterised
by low average precipitation or available water in a region. Aridity
generally arises from widespread persistent atmospheric subsidence
or anticyclonic conditions, and from more localised subsidence
in the lee side of mountains (adapted from Gbeckor-Kove, 1989;
Türkeş, 1999).
Atmosphere The gaseous envelope surrounding the Earth, divided
into five layers — the troposphere which contains half of the Earth’s
atmosphere, the stratosphere, the mesosphere, the thermosphere,
and the exosphere, which is the outer limit of the atmosphere. The
dry atmosphere consists almost entirely of nitrogen (78.1% volume
mixing ratio) and oxygen (20.9% volume mixing ratio), together
with a number of trace gases, such as argon (0.93 % volume mixing
ratio), helium and radiatively active greenhouse gases (GHGs) such
as carbon dioxide (CO2) (0.04% volume mixing ratio) and ozone (O3).
In addition, the atmosphere contains the GHG water vapour (H2O),
whose amounts are highly variable but typically around 1% volume
mixing ratio. The atmosphere also contains clouds and aerosols. See
also Carbon dioxide (CO2), Ozone (O3), Troposphere, Stratosphere,
Greenhouse gas (GHG), and Hydrological cycle.
Atmosphere-ocean general circulation model
(AOGCM) See Climate model.
Atmospheric boundary layer The atmospheric layer adjacent
to the Earth’s surface that is affected by friction against that boundary
surface, and possibly by transport of heat and other variables across
that surface (AMS, 2000). The lowest 100 m of the boundary layer
(about 10% of the boundary layer thickness), where mechanical
generation of turbulence is dominant, is called the surface boundary
layer or surface layer.
Attribution See Detection and attribution.
Baseline scenario In much of the literature the term is also
synonymous with the term business-as-usual (BAU) scenario, although
the term BAU has fallen out of favour because the idea of business
as usual in century-long socio-economic projections is hard to
fathom. In the context of transformation pathways, the term baseline
scenarios refers to scenarios that are based on the assumption that
no mitigation policies or measures will be implemented beyond
those that are already in force and/or are legislated or planned to
be adopted. Baseline scenarios are not intended to be predictions
of the future, but rather counterfactual constructions that can serve
to highlight the level of emissions that would occur without further
policy effort. Typically, baseline scenarios are then compared to
mitigation scenarios that are constructed to meet different goals
for greenhouse gas (GHG) emissions, atmospheric concentrations
or temperature change. The term baseline scenario is often used
interchangeably with reference scenario and no policy scenario. See
also Emission scenario, and Mitigation scenario.
Biochar Relatively stable, carbon-rich material produced by
heating biomass in an oxygen-limited environment. Biochar is
distinguished from charcoal by its application: biochar is used as
a soil amendment with the intention to improve soil functions and
to reduce greenhouse gas (GHG) emissions from biomass that would
otherwise decompose rapidly (IBI, 2018).
Biodiversity Biodiversity or biological diversity means the
variability among living organisms from all sources including, among
other things, terrestrial, marine and other aquatic ecosystems and the
ecological complexes of which they are part; this includes diversity
within species, between species and of ecosystems (UN, 1992). See
also Ecosystem, and Ecosystem service.
Bioenergy Energy derived from any form of biomass or its
metabolic by-products. See also Biomass and Biofuel.
Bioenergy with carbon dioxide capture and storage
(BECCS) Carbon dioxide capture and storage (CCS) technology
applied to a bioenergy facility. Note that depending on the total
emissions of the BECCS supply chain, carbon dioxide (CO2) can be
removed from the atmosphere. See also Bioenergy, and Carbon
dioxide capture and storage (CCS).
Biofuel A fuel, generally in liquid form, produced from biomass.
Biofuels include bioethanol from sugarcane, sugar beet or maize, and
biodiesel from canola or soybeans. See also Biomass, and Bioenergy.
Biogeochemical effects Processes through which land affects
climate, excluding biophysical effects. These processes include
changes in net emissions of carbon dioxide (CO2) towards the
atmosphere, net emissions of aerosols (mineral and organic), ozone
deposition on ecosystems, and net emissions of biogenic volatile
organic compounds (BVOCs) and their subsequent changes in
atmospheric chemistry. See also Biophysical effects.
Biomass Organic material excluding the material that is fossilised
or embedded in geological formations. Biomass may refer to the mass
of organic matter in a specific area (ISO, 2014). See also Bioenergy,
and Biofuel.
Traditional biomass
The combustion of wood, charcoal, agricultural residues and/or
animal dung for cooking or heating in open fires or in inefficient
stoves as is common in low-income countries.
Biome 'Global-scale zones, generally defined by the type of plant
life that they support in response to average rainfall and temperature
patterns. For example, tundra, coral reefs or savannas’ (IPBES, 2019).
Biophysical effects The range of physical processes through
which land affects climate. These processes include changes in
hydrology (e.g. water vapor fluxes at the land/atmosphere interface),
heat exchanges via convective fluxes (latent and sensible), radiation
(solar and infra-red, absorbed and emitted), and momentum (e.g.
affecting wind speed).

Glossary Annex I
AI
Black carbon (BC) A relatively pure form of carbon, also known
as soot, arising from the incomplete combustion of fossil fuels,
biofuel, and biomass. It stays in the atmosphere only for days or
weeks. Black carbon is a climate forcing agent with strong warming
effect, both in the atmosphere and when deposited on snow or ice.
See also Atmosphere, and Aerosol.
Blue carbon All biologically-driven carbon fluxes and storage
in marine systems that are amenable to management can be
considered as blue carbon. Coastal blue carbon focuses on rooted
vegetation in the coastal zone, such as tidal marshes, mangroves and
seagrasses. These ecosystems have high carbon burial rates on a per
unit area basis and accumulate carbon in their soils and sediments.
They provide many non-climatic benefits and can contribute to
ecosystem-based adaptation. If degraded or lost, coastal blue carbon
ecosystems are likely to release most of their carbon back to the
atmosphere. There is current debate regarding the application of the
blue carbon concept to other coastal and non-coastal processes and
ecosystems, including the open ocean. See also Ecosystem services,
and Carbon sequestration.
Business as usual (BAU) See Baseline scenario.
Carbon budget Refers to three concepts in the literature:
(1) an assessment of carbon cycle sources and sinks on a global
level, through the synthesis of evidence for fossil-fuel and cement
emissions, land-use change emissions, ocean and land CO2 sinks,
and the resulting atmospheric carbon dioxide (CO2) growth rate.
This is referred to as the global carbon budget; (2) the estimated
cumulative amount of global carbon dioxide emissions that that is
estimated to limit global surface temperature to a given level above
a reference period, taking into account global surface temperature
contributions of other greenhouse gases (GHGs) and climate forcers;
(3) the distribution of the carbon budget defined under (2) to the
regional, national, or sub-national level based on considerations of
equity, costs or efficiency. See also Remaining carbon budget.
Carbon cycle The flow of carbon (in various forms, e.g., as carbon
dioxide (CO2), carbon in biomass, and carbon dissolved in the ocean
as carbonate and bicarbonate) through the atmosphere, hydrosphere,
terrestrial and marine biosphere and lithosphere. In this report, the
reference unit for the global carbon cycle is GtCO2 or GtC (one
Gigatonne = 1 Gt = 1015 grams; 1GtC corresponds to 3.667 GtCO2).
Carbon dioxide (CO2) A naturally occurring gas, CO2 is also a byproduct
of burning fossil fuels (such as oil, gas and coal), of burning
biomass, of land-use changes (LUC) and of industrial processes (e.g.,
cement production). It is the principal anthropogenic greenhouse gas
(GHG) that affects the Earth’s radiative balance. It is the reference gas
against which other GHGs are measured and therefore has a Global
Warming Potential (GWP) of 1. See also Greenhouse gas (GHG), Land
use, and Land-use change.
Carbon dioxide capture and storage (CCS) A process in
which a relatively pure stream of carbon dioxide (CO2) from industrial
and energy-related sources is separated (captured), conditioned,
compressed and transported to a storage location for long-term
isolation from the atmosphere. Sometimes referred to as Carbon
Capture and Storage. See also Carbon dioxide capture and utilisation
(CCU), Bioenergy with carbon dioxide capture and storage (BECCS),
and Sequestration.
Carbon dioxide capture and utilisation (CCU) A process in
which carbon dioxide (CO2) is captured and then used to produce a
new product. If the CO2 is stored in a product for a climate-relevant
time horizon, this is referred to as carbon dioxide capture, utilisation
and storage (CCUS). Only then, and only combined with CO2 recently
removed from the atmosphere, can CCUS lead to carbon dioxide
removal. CCU is sometimes referred to as Carbon dioxide capture and
use. See also Carbon dioxide capture and storage (CCS).
Carbon dioxide capture, utilisation and storage (CCUS) See
Carbon dioxide capture and utilisation (CCU).
Carbon dioxide removal (CDR) Anthropogenic activities
removing carbon dioxide (CO2) from the atmosphere and durably
storing it in geological, terrestrial, or ocean reservoirs, or in products.
It includes existing and potential anthropogenic enhancement of
biological or geochemical sinks and direct air capture and storage,
but excludes natural CO2 uptake not directly caused by human
activities. See also Mitigation (of climate change), Greenhouse gas
removal (GGR), Negative emission technologies, and Sink.
Carbon intensity The amount of emissions of carbon dioxide
(CO2) released per unit of another variable such as gross domestic
product (GDP), output energy use or transport.
Carbon price The price for avoided or released carbon dioxide
(CO2) or CO2-equivalent emissions. This may refer to the rate of
a carbon tax, or the price of emission permits. In many models that
are used to assess the economic costs of mitigation, carbon prices are
used as a proxy to represent the level of effort in mitigation policies.
See also Mitigation.
Carbon sequestration The process of storing carbon in a carbon
pool. See also Blue carbon, Carbon dioxide capture and storage
(CCS), Uptake, and Sink.
Carbon sink See Sink.
Carbon stock The quantity of carbon in a carbon pool. See also
Pool, carbon and nitrogen.
Citizen science A voluntary participation of the public in the
collection and/or processing of data as part of a scientific study
(Silvertown, 2009).
Clean Development Mechanism (CDM) A mechanism defined
under Article 12 of the Kyoto Protocol through which investors
(governments or companies) from developed (Annex B) countries
may finance greenhouse gas (GHG) emission reduction or removal
projects in developing countries (Non-Annex B), and receive Certified
Emission Reduction Units (CERs) for doing so. The CERs can be credited
towards the commitments of the respective developed countries.
The CDM is intended to facilitate the two objectives of promoting
sustainable development (SD) in developing countries and of helping
industrialised countries to reach their emissions commitments in
a cost-effective way.
Climate Climate in a narrow sense is usually defined as the
average weather, or more rigorously, as the statistical description in
terms of the mean and variability of relevant quantities over a period


of time ranging from months to thousands or millions of years. The
classical period for averaging these variables is 30 years, as defined
by the World Meteorological Organization. The relevant quantities
are most often surface variables such as temperature, precipitation
and wind. Climate in a wider sense is the state, including a statistical
description, of the climate system.
Climate change A change in the state of the climate that can be
identified (e.g., by using statistical tests) by changes in the mean and/
or the variability of its properties and that persists for an extended
period, typically decades or longer. Climate change may be due to
natural internal processes or external forcings such as modulations
of the solar cycles, volcanic eruptions and persistent anthropogenic
changes in the composition of the atmosphere or in land use. Note
that the United Nations Framework Convention on Climate Change
(UNFCCC), in its Article 1, defines climate change as: ‘a change of
climate which is attributed directly or indirectly to human activity
that alters the composition of the global atmosphere and which is
in addition to natural climate variability observed over comparable
time periods’. The UNFCCC thus makes a distinction between climate
change attributable to human activities altering the atmospheric
composition and climate variability attributable to natural causes.
See also Climate variability, Global warming, Ocean acidification, and
Detection and attribution.
Climate extreme (extreme weather or climate event) The
occurrence of a value of a weather or climate variable above (or
below) a threshold value near the upper (or lower) ends of the
range of observed values of the variable. For simplicity, both extreme
weather events and extreme climate events are referred to collectively
as ‘climate extremes.’ See also Extreme weather event.
Climate feedback An interaction in which a perturbation in
one climate quantity causes a change in a second and the change
in the second quantity ultimately leads to an additional change in
the first. A negative feedback is one in which the initial perturbation
is weakened by the changes it causes; a positive feedback is one in
which the initial perturbation is enhanced. The initial perturbation
can either be externally forced or arise as part of internal variability.
Climate governance See Governance.
Climate model A numerical representation of the climate
system based on the physical, chemical and biological properties
of its components, their interactions and feedback processes and
accounting for some of its known properties. The climate system
can be represented by models of varying complexity; that is, for
any one component or combination of components a spectrum or
hierarchy of models can be identified, differing in such aspects as
the number of spatial dimensions, the extent to which physical,
chemical or biological processes are explicitly represented, or the
level at which empirical parametrizations are involved. There is an
evolution towards more complex models with interactive chemistry
and biology. Climate models are applied as a research tool to study
and simulate the climate and for operational purposes, including
monthly, seasonal and interannual climate predictions. See also Earth
system model (ESM).
Climate projection Simulated response of the climate system
to a scenario of future emissions or concentrations of greenhouse
gases (GHGs) and aerosols, and changes in land use, generally
derived using climate models. Climate projections are distinguished
from climate predictions by their dependence on the emission/
concentration/radiative forcing scenario used, which is in turn based
on assumptions concerning, for example, future socioeconomic and
technological developments that may or may not be realised.
Climate-resilient development pathways (CRDPs)
Trajectories that strengthen sustainable development and efforts to
eradicate poverty and reduce inequalities while promoting fair and
cross-scalar adaptation to and resilience in a changing climate. They
raise the ethics, equity, and feasibility aspects of the deep societal
transformation needed to drastically reduce emissions to limit global
warming (e.g., to 2°C) and achieve desirable and liveable futures and
well-being for all.
Climate-resilient pathways Iterative processes for managing
change within complex systems in order to reduce disruptions and
enhance opportunities associated with climate change. See also
Climate-resilient development pathways (CRDPs), Development
pathways, Pathways, and Transformation pathways.
Climate sensitivity The change in the annual global mean
surface temperature in response to a change in the atmospheric
carbon dioxide (CO2) concentration or other radiative forcing.
Equilibrium climate sensitivity
An estimate of the global mean surface temperature response to
a doubling of the atmospheric carbon dioxide (CO2) concentration
that is evaluated from model output or observations for evolving
non-equilibrium conditions. It is a measure of the strengths of the
climate feedbacks at a particular time and may vary with forcing
history and climate state, and therefore may differ from equilibrium
climate sensitivity.
Transient climate response
The change in the global mean surface temperature, averaged over
a 20-year period, centred at the time of atmospheric carbon dioxide
(CO2) doubling, in a climate model simulation in which CO2 increases
at 1% yr–1 from pre-industrial. It is a measure of the strength of
climate feedbacks and the timescale of ocean heat uptake.
See also Climate model, and Global mean surface temperature
(GMST).
Climate services Information and products that enhance users’
knowledge and understanding about the impacts of climate change
and/or climate variability so as to aid decision-making of individuals
and organisations and enable preparedness and early climate change
action. Such services involve high-quality data from national and
international databases on temperature, rainfall, wind, soil moisture
and ocean conditions, as well as maps, risk and vulnerability
analyses, assessments, and long-term projections and scenarios.
Depending on the user’s needs, these data and information products
may be combined with non-meteorological data, such as agricultural
production, health trends, population distributions in high-risk areas,
road and infrastructure maps for the delivery of goods, and other
socio-economic variables (WMO, 2019).
Climate-smart agriculture (CSA) An approach to agriculture
that aims to transform and reorient agricultural systems to effectively
support development and ensure food security in a changing climate

Glossary Annex I
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by: sustainably increasing agricultural productivity and incomes;
adapting and building resilience to climate change; and reducing and/
or removing greenhouse gas emissions, where possible (FAO, 2018).
Climate system The system consisting of five major components:
the atmosphere, the hydrosphere, the cryosphere, the lithosphere and
the biosphere and the interactions between them. The climate system
evolves in time under the influence of its own internal dynamics
and because of external forcings such as volcanic eruptions, solar
variations, orbital forcing, and anthropogenic forcings such as the
changing composition of the atmosphere and land-use change.
Climate target A temperature limit, concentration level,
or emissions reduction goal used towards the aim of avoiding
dangerous anthropogenic interference with the climate system. For
example, national climate targets may aim to reduce greenhouse gas
emissions by a certain amount over a given time horizon, for example
those under the Kyoto Protocol.
Climate variability Variations in the mean state and other
statistics (such as standard deviations, the occurrence of extremes,
etc.) of the climate on all spatial and temporal scales beyond that
of individual weather events. Variability may be due to natural
internal processes within the climate system (internal variability), or
to variations in natural or anthropogenic external forcing (external
variability). See also Climate change.
CO2 equivalent (CO2-eq) emission The amount of carbon
dioxide (CO2) emission that would cause the same integrated
radiative forcing or temperature change, over a given time horizon, as
an emitted amount of a greenhouse gas (GHG) or a mixture of GHGs.
There are a number of ways to compute such equivalent emissions
and choose appropriate time horizons. Most typically, the CO2-
equivalent emission is obtained by multiplying the emission of a GHG
by its Global Warming Potential (GWP) for a 100 year time horizon.
For a mix of GHGs it is obtained by summing the CO2-equivalent
emissions of each gas. CO2-equivalent emission is a common scale
for comparing emissions of different GHGs but does not imply
equivalence of the corresponding climate change responses. There
is generally no connection between CO2-equivalent emissions and
resulting CO2-equivalent concentrations.
CO2 fertilisation The enhancement of plant growth as a result
of increased atmospheric carbon dioxide (CO2) concentration.
The magnitude of CO2 fertilisation depends on nutrients and
water availability.
Co-benefits The positive effects that a policy or measure aimed
at one objective might have on other objectives, thereby increasing
the total benefits for society or the environment. Co-benefits are
often subject to uncertainty and depend on local circumstances
and implementation practices, among other factors. Co-benefits are
also referred to as ancillary benefits. See also Adverse side-effects,
and Risk.
Collective action A number of people working together
voluntarily to achieve some common objective (Meinzen-Dick and Di
Gregorio, 2004).
Conference of the Parties (COP) The supreme body of UN
conventions, such as the United Nations Framework Convention on
Climate Change (UNFCCC), comprising parties with a right to vote
that have ratified or acceded to the convention. See also United
Nations Convention to Combat Desertification (UNCCD).
Confidence The robustness of a finding based on the type,
amount, quality and consistency of evidence (e.g., mechanistic
understanding, theory, data, models, expert judgment) and on the
degree of agreement across multiple lines of evidence. In this report,
confidence is expressed qualitatively (Mastrandrea et al., 2010). See
also Likelihood, and Uncertainty.
Convection Vertical motion driven by buoyancy forces arising
from static instability, usually caused by near-surface cooling or
increases in salinity in the case of the ocean and near-surface warming
or cloud-top radiative cooling in the case of the atmosphere. In the
atmosphere, convection gives rise to cumulus clouds and precipitation
and is effective at both scavenging and vertically transporting
chemical species. In the ocean, convection can carry surface waters
to deep within the ocean.
Coping capacity The ability of people, institutions, organisations,
and systems, using available skills, values, beliefs, resources, and
opportunities, to address, manage, and overcome adverse conditions
in the short to medium term. (UNISDR, 2009; IPCC, 2012a). See
also Resilience.
Cost-benefit analysis Monetary assessment of all negative
and positive impacts associated with a given action. Cost-benefit
analysis enables comparison of different interventions, investments
or strategies and reveal how a given investment or policy effort pays
off for a particular person, company or country. Cost-benefit analyses
representing society’s point of view are important for climate
change decision making, but there are difficulties in aggregating
costs and benefits across different actors and across timescales. See
also Discounting.
Cost-effectiveness A measure of the cost at which a policy
goal or outcome is achieved. The lower the cost the greater the
cost effectiveness.
Coupled Model Intercomparison Project (CMIP) A climate
modelling activity from the World Climate Research Programme
(WCRP) which coordinates and archives climate model simulations
based on shared model inputs by modelling groups from around
the world. The CMIP3 multi-model data set includes projections
using SRES scenarios. The CMIP5 data set includes projections using
the Representative Concentration Pathways (RCPs). The CMIP6
phase involves a suite of common model experiments as well as an
ensemble of CMIP-endorsed model intercomparison projects (MIPs).
Cumulative emissions The total amount of emissions released
over a specified period of time. See also Carbon budget.
Decarbonisation Process by which countries, individuals or other
entities aim to achieve zero fossil carbon existence. Typically refers
to a reduction of the carbon emissions associated with electricity,
industry and transport.
Decoupling Decoupling (in relation to climate change) is where
economic growth is no longer strongly associated with consumption
of fossil fuels. Relative decoupling is where both grow but at different


rates. Absolute decoupling is where economic growth happens but
fossil fuels decline.
Deforestation Conversion of forest to non-forest. [Note: For
a discussion of the term forest and related terms such as afforestation,
reforestation and deforestation in the context of reporting and
accounting Article 3.3 and 3.4 activities under the Kyoto Protocol, see
Revised Supplementary Methods and Good Practice Guidance
Arising from the Kyoto Protocol.] See also Reducing Emissions from
Deforestation and Forest Degradation (REDD+).
Deliberative governance See Governance.
Demand and supply-side measures
Demand-side measures
Policies and programmes for influencing the demand for goods and/
or services. In the energy sector, demand-side management aims
at reducing the demand for electricity and other forms of energy
required to deliver energy services.
Supply-side measures
Policies and programmes for influencing how a certain demand for
goods and/or services is met. In the energy sector, for example, supplyside
mitigation measures aim at reducing the amount of greenhouse
gas (GHG) emissions emitted per unit of energy produced.
See also Mitigation measures.
Demand-side measures See Demand and supply-side measures.
Desertification Land degradation in arid, semi-arid, and dry subhumid
areas resulting from many factors, including climatic variations
and human activities (UNCCD, 1994).
Detection See Detection and attribution.
Detection and attribution Detection of change is defined
as the process of demonstrating that climate or a system affected
by climate has changed in some defined statistical sense, without
providing a reason for that change. An identified change is detected
in observations if its likelihood of occurrence by chance due to
internal variability alone is determined to be small, for example,
<10%. Attribution is defined as the process of evaluating the relative
contributions of multiple causal factors to a change or event with
a formal assessment of confidence.
Development pathways See Pathways.
Diet ‘The kinds of food that follow a particular pattern that
a person or community eats’ (FAO, 2014). See also Dietary patterns.
Dietary patterns The quantities, proportions, variety or
combinations of different foods and beverages in diets, and the
frequency with which they are habitually consumed (Dietary
Guidelines Advisory Committee, 2015). See also Diet.
Dietary and nutrition transitions Modernisation,
urbanisation, economic development, and increased wealth lead to
predictable shifts in diet, referred to as ‘nutrition transitions’ (Misra
and Khurana, 2008; Popkin, 2006). Over historical time there have
been a number of dietary transitions but in recent decades the
prime transition has been associated with changes from subsistence
towards eating diets rich in calories and relatively poor in nutrition
(the ‘westernised diet’) that are obesogenic. From a public health
perspective, a new dietary transition is in focus, from the obesogenic
diet to one promoting health.
Disaster A ‘serious disruption of the functioning of a community
or a society at any scale due to hazardous events interacting with
conditions of exposure, vulnerability and capacity, leading to one or
more of the following: human, material, economic and environmental
losses and impacts’ (UNISDR, 2017). See also Exposure, Risk,
Vulnerability and Hazard.
Disaster risk management (DRM) Processes for designing,
implementing, and evaluating strategies, policies, and measures
to improve the understanding of current and future disaster risk,
foster disaster risk reduction and transfer, and promote continuous
improvement in disaster preparedness, prevention and protection,
response, and recovery practices, with the explicit purpose of
increasing human security, well-being, quality of life, and sustainable
development (UNISDR, 2017).
Discounting A mathematical operation that aims to make
monetary (or other) amounts received or expended at different
times (years) comparable across time. The discounter uses a fixed
or possibly time-varying discount rate from year to year that makes
future value worth less today (if the discount rate is positive). The
choice of discount rate(s) is debated as it is a judgement based on
hidden and/or explicit values.
Discount rate See Discounting.
(Internal) Displacement The forced movement of people
within the country they live in. Internally displaced persons (IDPs) are
‘Persons or groups of persons who have been forced or obliged to flee
or to leave their homes or places of habitual residence, in particular as
a result of or in order to avoid the effects of armed conflict, situations
of generalized violence, violations of human rights or natural or
human-made disasters, and who have not crossed an internationally
recognized State border’ (UN, 1998). See also Migration.
Displacement In land system science, displacement denotes the
increasing spatial separation between the location of agricultural
and forestry production and the place of consumption of these
products, as it occurs with trade. Displacement disconnects spatially
environmental impacts from their socioeconomic drivers.
Downscaling Method that derives local- to regional-scale (up to
km) information from larger-scale models or data analyses. Two
main methods exist: dynamical downscaling and empirical/statistical
downscaling. The dynamical method uses the output of regional
climate models, global models with variable spatial resolution, or
high-resolution global models. The empirical/statistical methods [are
based on observations and] develop statistical relationships that link
the large-scale atmospheric variables with local/ regional climate
variables. In all cases, the quality of the driving model remains an
important limitation on quality of the downscaled information. The
two methods can be combined, e.g., applying empirical/statistical
downscaling to the output of a regional climate model, consisting of
a dynamical downscaling of a global climate model.
Drainage ‘Artificial lowering of the soil water table’ (IPCC, 2013).
See also Rewetting.

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Drought A period of abnormally dry weather long enough
to cause a serious hydrological imbalance. Drought is a relative
term, therefore any discussion in terms of precipitation deficit
must refer to the particular precipitation-related activity that is
under discussion. For example, shortage of precipitation during the
growing season impinges on crop production or ecosystem function
in general (due to soil moisture drought, also termed agricultural
drought), and during the runoff and percolation season primarily
affects water supplies (hydrological drought). Storage changes in
soil moisture and groundwater are also affected by increases in
actual evapotranspiration in addition to reductions in precipitation.
A period with an abnormal precipitation deficit is defined as
a meteorological drought.
Megadrought
A very lengthy and pervasive drought, lasting much longer than
normal, usually a decade or more.
Early warning systems (EWS) The set of technical, financial
and institutional capacities needed to generate and disseminate
timely and meaningful warning information to enable individuals,
communities and organisations threatened by a hazard to prepare
to act promptly and appropriately to reduce the possibility of harm
or loss. Dependent upon context, EWS may draw upon scientific and/
or Indigenous knowledge. EWS are also considered for ecological
applications e.g., conservation, where the organisation itself is not
threatened by hazard but the ecosystem under conservation is
(an example is coral bleaching alerts), in agriculture (for example,
warnings of ground frost, hailstorms) and in fisheries (storm and
tsunami warnings) (UNISDR, 2009; IPCC, 2012a).
Earth system feedbacks See Climate feedback.
Earth system model (ESM) A coupled atmosphere–ocean
general circulation model in which a representation of the carbon
cycle is included, allowing for interactive calculation of atmospheric
carbon dioxide (CO2) or compatible emissions. Additional components
(e.g., atmospheric chemistry, ice sheets, dynamic vegetation, nitrogen
cycle, but also urban or crop models) may be included. See also
Climate model.
Ecological cascade A series of secondary extinctions as a result
of the extinction of a key species within an ecosystem (Soulé, 2010).
Ecosystem A functional unit consisting of living organisms, their
non-living environment and the interactions within and between
them. The components included in a given ecosystem and its spatial
boundaries depend on the purpose for which the ecosystem is
defined: in some cases they are relatively sharp, while in others they
are diffuse. Ecosystem boundaries can change over time. Ecosystems
are nested within other ecosystems and their scale can range from
very small to the entire biosphere. In the current era, most ecosystems
either contain people as key organisms, or are influenced by the effects
of human activities in their environment. See also Ecosystem services.
Ecosystem services Ecological processes or functions having
monetary or non-monetary value to individuals or society at large.
These are frequently classified as (1) supporting services such as
productivity or biodiversity maintenance, (2) provisioning services
such as food or fibre, (3) regulating services such as climate regulation
or carbon sequestration, and (4) cultural services such as tourism or
spiritual and aesthetic appreciation. See also Ecosystem.
Effective climate sensitivity See Climate sensitivity.
Effective radiative forcing See Radiative forcing.
El Niño-Southern Oscillation (ENSO) The term El Niño was
initially used to describe a warm-water current that periodically flows
along the coast of Ecuador and Peru, disrupting the local fishery. It has
since become identified with warming of the tropical Pacific Ocean
east of the dateline. This oceanic event is associated with a fluctuation
of a global-scale tropical and subtropical surface pressure pattern
called the Southern Oscillation. This coupled atmosphere–ocean
phenomenon, with preferred time scales of two to about seven
years, is known as the El Niño-Southern Oscillation (ENSO). It is often
measured by the surface pressure anomaly difference between Tahiti
and Darwin and/or the sea surface temperatures in the central and
eastern equatorial Pacific. During an ENSO event, the prevailing trade
winds weaken, reducing upwelling and altering ocean currents such
that the sea surface temperatures warm, further weakening the trade
winds. This phenomenon has a great impact on the wind, sea surface
temperature and precipitation patterns in the tropical Pacific. It has
climatic effects throughout the Pacific region and in many other parts
of the world, through global teleconnections. The cold phase of ENSO
is called La Niña.
Embodied (embedded) [emissions, water, land] The total
emissions [water use, land use] generated [used] in the production
of goods and services regardless of the location and timing of those
emissions [water use, land use] in the production process. This
includes emissions [water use, land use] within the country used
to produce goods or services for the country’s own use, but also
includes the emissions [water use, land use] related to the production
of such goods or services in other countries that are then consumed
in another country through imports. Such emissions [water, land]
are termed ‘embodied’ or ‘embedded’ emissions, or in some cases
(particularly with water) as ‘virtual water use’ (David and Caldeira,
; Allan, 2005; MacDonald et al., 2015).
Emission scenario A plausible representation of the future
development of emissions of substances that are radiatively active
(e.g., greenhouse gases (GHGs), aerosols) based on a coherent and
internally consistent set of assumptions about driving forces (such as
demographic and socio-economic development, technological change,
energy and land use) and their key relationships. Concentration
scenarios, derived from emission scenarios, are often used as
input to a climate model to compute climate projections. See also
Baseline scenario, Mitigation scenario, Representative Concentration
Pathways (RCPs) (under Pathways), Shared socio-economic pathways
(SSPs) (under Pathways), Scenario, Socio-economic scenario, and
Transformation pathway.
Emission trajectories A projected development in time of the
emission of a greenhouse gas (GHG) or group of GHGs, aerosols, and
GHG precursors. See also Pathways.
Energy access Access to clean, reliable and affordable energy
services for cooking and heating, lighting, communications, and
productive uses (with special reference to Sustainable Development
Goal 7) (AGECC, 2010). See also Traditional biomass.


Enabling conditions (for adaptation and mitigation
options) Conditions that affect the feasibility of adaptation
and mitigation options, and can accelerate and scale-up systemic
transitions that would limit temperature increase and enhance
capacities of systems and societies to adapt to the associated climate
change, while achieving sustainable development, eradicating
poverty and reducing inequalities. Enabling conditions include
finance, technological innovation, strengthening policy instruments,
institutional capacity, multi-level governance, and changes in human
behaviour and lifestyles. They also include inclusive processes,
attention to power asymmetries and unequal opportunities for
development and reconsideration of values.
Energy efficiency The ratio of output or useful energy or energy
services or other useful physical outputs obtained from a system,
conversion process, transmission or storage activity to the input
of energy (measured as kWh kWh–1, tonnes kWh–1 or any other
physical measure of useful output like tonne-km transported). Energy
efficiency is often described by energy intensity. In economics,
energy intensity describes the ratio of economic output to energy
input. Most commonly energy efficiency is measured as input energy
over a physical or economic unit, i.e. kWh USD–1 (energy intensity),
kWh tonne–1. For buildings, it is often measured as kWh m–2, and
for vehicles as km liter–1or liter km–1. Very often in policy ‘energy
efficiency’ is intended as the measures to reduce energy demand
through technological options such as insulating buildings, more
efficient appliances, efficient lighting, efficient vehicles, etc.
Energy security The goal of a given country, or the global
community as a whole, to maintain an adequate, stable and
predictable energy supply. Measures encompass safeguarding the
sufficiency of energy resources to meet national energy demand at
competitive and stable prices and the resilience of the energy supply;
enabling development and deployment of technologies; building
sufficient infrastructure to generate, store and transmit energy
supplies and ensuring enforceable contracts of delivery.
Enhanced weathering Enhancing the removal of carbon
dioxide (CO2) from the atmosphere through dissolution of silicate
and carbonate rocks by grinding these minerals to small particles
and actively applying them to soils, coasts or oceans.
(Model) Ensemble A group of parallel model simulations
characterising historical climate conditions, climate predictions, or
climate projections. Variation of the results across the ensemble
members may give an estimate of modelling-based uncertainty.
Ensembles made with the same model but different initial conditions
only characterise the uncertainty associated with internal climate
variability, whereas multi-model ensembles including simulations
by several models also include the impact of model differences.
Perturbed parameter ensembles, in which model parameters are
varied in a systematic manner, aim to assess the uncertainty resulting
from internal model specifications within a single model. Remaining
sources of uncertainty unaddressed with model ensembles are
related to systematic model errors or biases, which may be assessed
from systematic comparisons of model simulations with observations
wherever available. See also Climate projection.
Equality A principle that ascribes equal worth to all human beings,
including equal opportunities, rights, and obligations, irrespective
of origins.
Inequality
Uneven opportunities and social positions, and processes of
discrimination within a group or society, based on gender,
class, ethnicity, age, and (dis)ability, often produced by uneven
development. Income inequality refers to gaps between highest and
lowest income earners within a country and between countries. See
also Equity and Fairness.
Equilibrium climate sensitivity See Climate sensitivity.
Equity The principle of being fair and impartial, and a basis for
understanding how the impacts and responses to climate change,
including costs and benefits, are distributed in and by society in more
or less equal ways. It is often aligned with ideas of equality, fairness
and justice and applied with respect to equity in the responsibility
for, and distribution of, climate impacts and policies across society,
generations, and gender, and in the sense of who participates and
controls the processes of decision making.
Distributive equity
Equity in the consequences, outcomes, costs and benefits of actions
or policies. In the case of climate change or climate policies for
different people, places and countries, including equity aspects of
sharing burdens and benefits for mitigation and adaptation.
Gender equity
Equity between women and men with regard to their rights,
resources and opportunities. In the case of climate change, gender
equity recognises that women are often more vulnerable to the
impacts of climate change and may be disadvantaged in the process
and outcomes of climate policy.
Inter-generational equity
Equity between generations. In the context of climate change, intergenerational
equity acknowledges that the effects of past and present
emissions, vulnerabilities and policies impose costs and benefits for
people in the future and of different age groups.
Procedural equity
Equity in the process of decision making including recognition and
inclusiveness in participation, equal representation, bargaining
power, voice and equitable access to knowledge and resources
to participate.
See also Equality and Fairness.
Evaporation The physical process by which a liquid (e.g., water)
becomes a gas (e.g., water vapour).
Evapotranspiration The combined processes through which
water is transferred to the atmosphere from open water and ice
surfaces, bare soil, and vegetation that make up the Earth’s surface.
Potential Evapotranspiration
The potential rate of water loss without any limits imposed by the
water supply. See also Evaporation.
Evidence Data and information used in the scientific process to
establish findings. In this report, the degree of evidence reflects the
amount, quality, and consistency of scientific/technical information

Glossary Annex I
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on which the Lead Authors base their findings. See also Agreement,
Confidence, Likelihood, and Uncertainty.
Exposure The presence of people; livelihoods; species or
ecosystems; environmental functions, services, and resources;
infrastructure; or economic, social, or cultural assets in places and
settings that could be adversely affected. See also Hazard, Risk,
and Vulnerability.
Extratropical Cyclone Any cyclonic-scale storm that is not
a tropical cyclone. Usually refers to a middle- or high-latitude
migratory storm system formed in regions of large horizontal
temperature variations. Sometimes called extratropical storm or
extratropical low. See also Tropical cyclone.
Extreme weather or climate event See Climate extreme
(extreme weather or climate event).
Extreme weather event An event that is rare at a particular
place and time of year. Definitions of ‘rare’ vary, but an extreme
weather event would normally be as rare as or rarer than the 10th
or 90th percentile of a probability density function estimated from
observations. By definition, the characteristics of what is called
extreme weather may vary from place to place in an absolute sense.
When a pattern of extreme weather persists for some time, such as
a season, it may be classed as an extreme climate event, especially
if it yields an average or total that is itself extreme (e.g., drought
or heavy rainfall over a season). See also Heat wave, and Climate
extreme (extreme weather or climate event).
Fairness Impartial and just treatment without favouritism or
discrimination in which each person is considered of equal worth
with equal opportunity. See also Equity, and Equality.
Feasibility The degree to which climate goals and response
options are considered possible and/or desirable. Feasibility
depends on geophysical, ecological, technological, economic, social
and institutional conditions for change. Conditions underpinning
feasibility are dynamic, spatially variable, and may vary between
different groups. See also Enabling conditions.
Feedback See Climate feedback.
Flexible governance See Governance.
Flood The overflowing of the normal confines of a stream or other
body of water, or the accumulation of water over areas that are not
normally submerged. Floods include river (fluvial) floods, flash floods,
urban floods, rain (pluvial) floods, sewer floods, coastal floods, and
glacial lake outburst floods.
Flux A movement (a flow) of matter (e.g., water vapor, particles),
heat or energy from one place to another, or from one medium (e.g.,
land surface) to another (e.g., atmosphere).
Food loss and waste ‘The decrease in quantity or quality
of food’. Food waste is part of food loss and refers to discarding
or alternative (non-food) use of food that is safe and nutritious
for human consumption along the entire food supply chain, from
primary production to end household consumer level. Food waste is
recognised as a distinct part of food loss because the drivers that
generate it and the solutions to it are different from those of food
losses (FAO, 2015b).
Food security A situation that exists when all people, at all times,
have physical, social and economic access to sufficient, safe and
nutritious food that meets their dietary needs and food preferences
for an active and healthy life (FAO, 2001). [Note: Whilst the term
‘food security’ explicitly includes nutrition within it ‘dietary needs …
for an active and healthy life’, in the past the term has sometimes
privileged the supply of calories (energy), especially to the hungry.
Thus, the term ‘food and nutrition security’ is often used (with the
same definition as food security) to emphasise that the term food
covers both energy and nutrition (FAO, 2009).]
Food system All the elements (environment, people, inputs,
processes, infrastructures, institutions, etc.) and activities that
relate to the production, processing, distribution, preparation and
consumption of food, and the output of these activities, including
socio-economic and environmental outcomes (HLPE, 2017). [Note:
Whilst there is a global food system (encompassing the totality of
global production and consumption), each location’s food system is
unique, being defined by that place’s mix of food produced locally,
nationally, regionally or globally.]
Forcing See Radiative forcing.
Forest A vegetation type dominated by trees. Many definitions
of the term forest are in use throughout the world, reflecting
wide differences in biogeophysical conditions, social structure and
economics. [Note: For a discussion of the term forest in the context of
National GHG inventories, see the 2006 IPCC Guidelines for National
GHG Inventories and information provided by the United Nations
Framework Convention on Climate Change (UNFCCC, 2019).] See
also Afforestation, Deforestation, and Reforestation.
Fossil fuels Carbon-based fuels from fossil hydrocarbon deposits,
including coal, oil, and natural gas.
Framework Convention on Climate Change See United
Nations Framework Convention on Climate Change (UNFCCC).
Gender equity See Equity.
Glacier A perennial mass of ice, and possibly firn and snow,
originating on the land surface by the recrystallisation of snow and
showing evidence of past or present flow. A glacier typically gains
mass by accumulation of snow, and loses mass by melting and ice
discharge into the sea or a lake if the glacier terminates in a body of
water. Land ice masses of continental size (>50 000 km2) are referred
to as ice sheets.
Global climate model (also referred to as general circulation
model, both abbreviated as GCM) See Climate model.
Global mean surface temperature (GMST) Estimated
global average of near-surface air temperatures over land and
sea-ice, and sea surface temperatures over ice-free ocean regions,
with changes normally expressed as departures from a value over a
specified reference period. When estimating changes in GMST, nearsurface
air temperature over both land and oceans are also used. See
also Global mean surface air temperature (GSAT), Land surface air
temperature, and Sea surface temperature (SST).


Global mean surface air temperature (GSAT) Global average
of near-surface air temperatures over land and oceans. Changes
in GSAT are often used as a measure of global temperature change in
climate models but are not observed directly. See also Global mean
surface temperature (GMST), and Land surface air temperature.
Global warming An increase in global mean surface temperature
(GMST) averaged over a 30-year period, or the 30-year period centred
on a particular year or decade, expressed relative to pre-industrial
levels unless otherwise specified. For 30-year periods that span past
and future years, the current multi-decadal warming trend is assumed
to continue. See also Climate change, and Climate variability.
Governance A comprehensive and inclusive concept of the full
range of means for deciding, managing, implementing and monitoring
policies and measures. Whereas government is defined strictly in
terms of the nation-state, the more inclusive concept of governance
recognises the contributions of various levels of government (global,
international, regional, sub-national and local) and the contributing
roles of the private sector, of nongovernmental actors, and of civil
society to addressing the many types of issues facing the global
community, and the local context where the effectiveness of policies
and measures are determined.
Adaptive governance
An emerging term in the literature for the evolution of formal
and informal institutions of governance that prioritise planning,
implementation and evaluation of policy through iterative social
learning; in the context of climate change, governance facilitating
social learning to steer the use and protection of natural resources,
and ecosystem services, particularly in situations of complexity
and uncertainty.
Climate governance
Purposeful mechanisms and measures aimed at steering social
systems towards preventing, mitigating, or adapting to the risks
posed by climate change (Jagers and Stripple, 2003).
Deliberative governance
Involves decision making through inclusive public conversation
which allows opportunity for developing policy options through
public discussion rather than collating individual preferences through
voting or referenda (although the latter governance mechanisms can
also be proceeded and legitimated by public deliberation processes).
Flexible governance
Strategies of governance at various levels, which prioritise the use
of social learning and rapid feedback mechanisms in planning and
policy making, often through incremental, experimental and iterative
management processes.
Governance capacity
The ability of governance institutions, leaders, and non-state and
civil society to plan, co-ordinate, fund, implement, evaluate and
adjust policies and measures over the short, medium and long term,
adjusting for uncertainty, rapid change and wide ranging impacts
and multiple actors and demands.
Multi-level governance
Negotiated, non-hierarchical exchanges between institutions at the
transnational, national, regional and local levels.
Participatory governance
A governance system that enables direct public engagement in
decision-making using a variety of techniques for example, referenda,
community deliberation, citizen juries or participatory budgeting. The
approach can be applied in formal and informal institutional contexts
from national to local, but is usually associated with devolved
decision making (Fung and Wright, 2003; Sarmiento and Tilly, 2018).
Governance capacity See Governance.
Grazing land The sum of rangelands and pastures not considered
as cropland, and subject to livestock grazing or hay production. It
includes a wide range of ecosystems, e.g. systems with vegetation
that fall below the threshold used in the forest land category,
silvo-pastoral systems, as well as natural, managed grasslands
and semideserts.
Green infrastructure The interconnected set of natural and
constructed ecological systems, green spaces and other landscape
features. It includes planted and indigenous trees, wetlands, parks,
green open spaces and original grassland and woodlands, as well
as possible building and street level design interventions that
incorporate vegetation. Green infrastructure provides services and
functions in the same way as conventional infrastructure (Culwick
and Bobbins, 2016).
Greenhouse gas (GHG) Gaseous constituents of the atmosphere,
both natural and anthropogenic, that absorb and emit radiation at
specific wavelengths within the spectrum of terrestrial radiation
emitted by the Earth’s surface, the atmosphere itself, and by clouds.
This property causes the greenhouse effect. Water vapour (H2O),
carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and ozone
(O3) are the primary GHGs in the Earth’s atmosphere. Moreover, there
are a number of entirely human-made GHGs in the atmosphere,
such as the halocarbons and other chlorine- and bromine-containing
substances, dealt with under the Montreal Protocol. Beside CO2, N2O
and CH4, the Kyoto Protocol deals with the GHGs sulphur hexafluoride
(SF6), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs).
Greenhouse gas removal (GGR) Withdrawal of a greenhouse
gas (GHG) and/or a precursor from the atmosphere by a sink. See also
Carbon dioxide removal (CDR), and Negative emissions.
Gross domestic product (GDP) The sum of gross value added,
at purchasers’ prices, by all resident and non-resident producers in
the economy, plus any taxes and minus any subsidies not included
in the value of the products in a country or a geographic region for a
given period, normally one year. GDP is calculated without deducting
for depreciation of fabricated assets or depletion and degradation of
natural resources.
Halocarbons A collective term for the group of partially
halogenated organic species, which includes the chlorofluorocarbons
(CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons
(HFCs), halons, methyl chloride and methyl bromide. Many of the
halocarbons have large Global Warming Potentials. The chlorine and
bromine-containing halocarbons are also involved in the depletion of
the ozone layer.
Hazard The potential occurrence of a natural or human-induced
physical event or trend that may cause loss of life, injury, or other

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health impacts, as well as damage and loss to property, infrastructure,
livelihoods, service provision, ecosystems and environmental
resources. See also Disaster, Exposure, Risk, and Vulnerability.
Heatwave A period of abnormally hot weather. Heatwaves and
warm spells have various and in some cases overlapping definitions.
See also Extreme weather event.
Holocene The current interglacial geological epoch, the second of
two epochs within the Quaternary period, the preceding being the
Pleistocene. The International Commission on Stratigraphy defines
the start of the Holocene at 11,700 years before 2000 (ICS, 2019).See
also Anthropocene.
Human behaviour The way in which a person acts in response
to a particular situation or stimulus. Human actions are relevant
at different levels, from international, national, and sub-national
actors, to NGO, firm-level actors, and communities, households, and
individual actions.
Adaptation behaviour
Human actions that directly or indirectly affect the risks of climate
change impacts.
Mitigation behaviour
Human actions that directly or indirectly influence mitigation.
Human behavioural change A transformation or modification
of human actions. Behaviour change efforts can be planned in ways
that mitigate climate change and/or reduce negative consequences
of climate change impacts.
Human rights Rights that are inherent to all human beings,
universal, inalienable, and indivisible, typically expressed and
guaranteed by law. They include the right to life, economic, social, and
cultural rights, and the right to development and self-determination
(based upon the definition by the UN Office of the High Commissioner
for Human Rights).
Procedural rights
Rights to a legal procedure to enforce substantive rights.
Substantive rights
Basic human rights, including the right to the substance of being
human such as life itself, liberty and happiness.
Human security A condition that is met when the vital core of
human lives is protected, and when people have the freedom and
capacity to live with dignity. In the context of climate change, the
vital core of human lives includes the universal and culturally specific,
material and non-material elements necessary for people to act on
behalf of their interests and to live with dignity.
Human system Any system in which human organisations
and institutions play a major role. Often, but not always, the term
is synonymous with society or social system. Systems such as
agricultural systems, urban systems, political systems, technological
systems, and economic systems are all human systems in the sense
applied in this report.
Hydrological cycle The cycle in which water evaporates from the
oceans and the land surface, is carried over the Earth in atmospheric
circulation as water vapour, condenses to form clouds, precipitates
as rain or snow, which on land can be intercepted by trees and
vegetation, potentially accumulating as snow or ice, provides runoff
on the land surface, infiltrates into soils, recharges groundwater,
discharges into streams, and ultimately, flows out into the oceans
as rivers, polar glaciers and ice sheets, from which it will eventually
evaporate again. The various systems involved in the hydrological
cycle are usually referred to as hydrological systems.
Ice sheet An ice body originating on land that covers an area of
continental size, generally defined as covering >50,000 km2. An ice
sheet flows outward from a high central ice plateau with a small
average surface slope. The margins usually slope more steeply, and
most ice is discharged through fast flowing ice streams or outlet
glaciers, often into the sea or into ice shelves floating on the sea.
There are only two ice sheets in the modern world, one on Greenland
and one on Antarctica. The latter is divided into the East Antarctic Ice
Sheet (EAIS), the West Antarctic Ice Sheet (WAIS) and the Antarctic
Peninsula ice sheet. During glacial periods there were other ice
sheets. See also Glacier.
Impacts (consequences, outcomes) The consequences of
realised risks on natural and human systems, where risks result
from the interactions of climate-related hazards (including extreme
weather and climate events), exposure, and vulnerability. Impacts
generally refer to effects on lives, livelihoods, health and well-being,
ecosystems and species, economic, social and cultural assets, services
(including ecosystem services), and infrastructure. Impacts may be
referred to as consequences or outcomes, and can be adverse or
beneficial. See also Adaptation, Exposure, Hazard, Loss and Damage,
and losses and damages, and Vulnerability.
(climate change) Impact assessment The practice of
identifying and evaluating, in monetary and/or non-monetary terms,
the effects of climate change on natural and human systems.
Incremental adaptation See Adaptation.
Indigenous knowledge The understandings, skills and
philosophies developed by societies with long histories of interaction
with their natural surroundings. For many Indigenous peoples,
Indigenous knowledge informs decision-making about fundamental
aspects of life, from day-to-day activities to longer term actions. This
knowledge is integral to cultural complexes, which also encompass
language, systems of classification, resource use practices, social
interactions, values, ritual and spirituality. These distinctive ways
of knowing are important facets of the world’s cultural diversity.
(UNESCO, 2018). See also Local knowledge.
Indirect land-use change See Land-use change.
Industrial revolution A period of rapid industrial growth with
far-reaching social and economic consequences, beginning in Britain
during the second half of the 18th century and spreading to Europe
and later to other countries including the United States. The invention
of the steam engine was an important trigger of this development.
The industrial revolution marks the beginning of a strong increase
in the use of fossil fuels, initially coal, and hence emission of carbon
dioxide (CO2). See also Pre-industrial.
Industrialised/developed/developing countries There are
a diversity of approaches for categorising countries on the basis of
their level of economic development, and for defining terms such


as industrialised, developed, or developing. Several categorisations
are used in this report. (1) In the United Nations system, there is no
established convention for designating of developed and developing
countries or areas. (2) The United Nations Statistics Division specifies
developed and developing regions based on common practice.
In addition, specific countries are designated as Least Developed
Countries (LDC), landlocked developing countries, small island
developing states (SIDS), and transition economies. Many countries
appear in more than one of these categories. (3) The World Bank
uses income as the main criterion for classifying countries as
low, lower middle, upper middle, and high income. (4) The United
Nations Development Programme (UNDP) aggregates indicators for
life expectancy, educational attainment, and income into a single
composite Human Development Index (HDI) to classify countries as
low, medium, high, or very high human development.
Inequality See Equality.
Institution Rules, norms and conventions held in common by
social actors that guide, constrain and shape human interaction.
Institutions can be formal, such as laws and policies, or informal,
such as norms and conventions. Organisations - such as parliaments,
regulatory agencies, private firms, and community bodies - develop
and act in response to institutional frameworks and the incentives
they frame. Institutions can guide, constrain and shape human
interaction through direct control, through incentives, and through
processes of socialisation. See also Institutional capacity.
Institutional capacity Building and strengthening individual
organisations and providing technical and management training to
support integrated planning and decision-making processes between
organisations and people, as well as empowerment, social capital,
and an enabling environment, including the culture, values and
power relations (Willems and Baumert, 2003).
Integrated assessment A method of analysis that combines
results and models from the physical, biological, economic and
social sciences and the interactions among these components in
a consistent framework to evaluate the status and the consequences
of environmental change and the policy responses to it. See also
Integrated assessment model (IAM).
Integrated assessment model (IAM) Models that integrate
knowledge from two or more domains into a single framework. They
are one of the main tools for undertaking integrated assessments.
One class of IAM used in respect of climate change mitigation may
include representations of: multiple sectors of the economy, such as
energy, land use and land use change; interactions between sectors;
the economy as a whole; associated greenhouse gas (GHG) emissions
and sinks; and reduced representations of the climate system. This
class of model is used to assess linkages between economic, social
and technological development and the evolution of the climate
system. Another class of IAM additionally includes representations of
the costs associated with climate change impacts, but includes less
detailed representations of economic systems. These can be used to
assess impacts and mitigation in a cost-benefit framework and have
been used to estimate the social cost of carbon.
Integrated response options In this report, integrated
response options are those options that simultaneously address
more than one land challenge. These can be categorised into options
that rely on a) land management, b) value chain management, and
c) risk management. Integrated response options are not mutually
exclusive. See also Land challenge.
Integrated water resources management (IWRM) A process
which promotes the coordinated development and management of
water, land and related resources in order to maximise economic and
social welfare in an equitable manner without compromising the
sustainability of vital ecosystems.
Inter-generational equity See Equity.
Internal variability See Climate variability.
Irreversibility A perturbed state of a dynamical system is defined
as irreversible on a given timescale if the recovery timescale from
this state due to natural processes is substantially longer than the
time it takes for the system to reach this perturbed state. See also
Tipping point.
Kyoto Protocol The Kyoto Protocol to the United Nations
Framework Convention on Climate Change (UNFCCC) is an
international treaty adopted in December 1997 in Kyoto, Japan, at
the Third Session of the Conference of the Parties (COP3) to the
UNFCCC. It contains legally binding commitments, in addition to
those included in the UNFCCC. Countries included in Annex B of the
Protocol (mostly OECD countries and countries with economies in
transition) agreed to reduce their anthropogenic greenhouse gas
(GHG) emissions (carbon dioxide (CO2), methane (CH4), nitrous
oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs),
and sulphur hexafluoride (SF6) by at least 5% below 1990 levels
in the first commitment period (2008–2012). The Kyoto Protocol
entered into force on 16 February 2005 and as of May 2018 had 192
Parties (191 States and the European Union). A second commitment
period was agreed in December 2012 at COP18, known as the Doha
Amendment to the Kyoto Protocol, in which a new set of Parties
committed to reduce GHG emissions by at least 18% below 1990
levels in the period from 2013 to 2020. However, as of May 2018, the
Doha Amendment had not received sufficient ratifications to enter
into force. See also Paris Agreement.
Land The terrestrial portion of the biosphere that comprises the
natural resources (soil, near surface air, vegetation and other biota,
and water), the ecological processes, topography, and human
settlements and infrastructure that operate within that system (FAO,
; UNCCD, 1994).
Land challenges In this report, land challenges refers to landbased
mitigation and adaptation, desertification, land degradation
and food security.
Land cover The biophysical coverage of land (e.g., bare soil,
rocks, forests, buildings and roads or lakes). Land cover is often
categorised in broad land-cover classes (e.g., deciduous forest,
coniferous forest, mixed forest, grassland, bare ground). [Note: In
some literature assessed in this report, land cover and land use are
used interchangeably, but the two represent distinct classification
systems. For example, the land cover class woodland can be under
various land uses such as livestock grazing, recreation, conservation,
or wood harvest.] See also Land cover change, and Land-use change.

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Land cover change Change from one land cover class to another,
due to change in land use or change in natural conditions (Pongratz et
al., 2018). See also Land-use change, and Land management change.
Land degradation A negative trend in land condition, caused by
direct or indirect human-induced processes including anthropogenic
climate change, expressed as long-term reduction or loss of at least
one of the following: biological productivity, ecological integrity or
value to humans. [Note: This definition applies to forest and nonforest
land. Changes in land condition resulting solely from natural
processes (such as volcanic eruptions) are not considered to be
land degradation. Reduction of biological productivity or ecological
integrity or value to humans can constitute degradation, but any one
of these changes need not necessarily be considered degradation.]
Land degradation neutrality A state whereby the amount
and quality of land resources necessary to support ecosystem
functions and services and enhance food security remain stable or
increase within specified temporal and spatial scales and ecosystems
(UNCCD, 2019).
Land management Sum of land-use practices (e.g., sowing,
fertilizing, weeding, harvesting, thinning, clear-cutting) that take
place within broader land-use categories. (Pongratz et al., 2018)
Land management change
A change in land management that occurs within a land-use category.
See also Land-use change.
Land potential The inherent, long-term potential of the land to
sustainably generate ecosystem services, which reflects the capacity
and resilience of the land-based natural capital, in the face of ongoing
environmental change (UNEP, 2016).
Land rehabilitation Direct or indirect actions undertaken with
the aim of reinstating a level of ecosystem functionality, where
the goal is provision of goods and services rather than ecological
restoration (McDonald, et al., 2016).
Land restoration The process of assisting the recovery of land
from a degraded state (McDonald et al., 2016; IPBES, 2018).
Land surface air temperature (LSAT) The near-surface air
temperature over land, typically measured at 1.25–2 m above the
ground using standard meteorological equipment.
Land use The total of arrangements, activities and inputs applied
to a parcel of land. The term land use is also used in the sense of
the social and economic purposes for which land is managed
(e.g., grazing, timber extraction, conservation and city dwelling).
In national GHG inventories, land use is classified according to
the IPCC land use categories of forest land, cropland, grassland,
wetlands, settlements, other lands (see the 2006 IPCC Guidelines for
National GHG Inventories for details). See also Land-use change and
Land management.
Land-use change (LUC) The change from one land use category
to another. [Note: In some of the scientific literature assessed in this
report, land-use change encompasses changes in land-use categories
as well as changes in land management.]
Indirect land-use change (iLUC)
Land use change outside the area of focus, that occurs as
a consequence of change in use or management of land within the
area of focus, such as through market or policy drivers. For example,
if agricultural land is diverted to biofuel production, forest clearance
may occur elsewhere to replace the former agricultural production.
See also Afforestation, Agriculture, Forestry and Other Land Use
(AFOLU), Deforestation, Land use, land-use change and forestry
(LULUCF), Reforestation, the IPCC Special Report on Land Use, Land-
Use Change, and Forestry (IPCC, 2000), and the 2006 IPCC Guidelines
for National GHG Inventories (IPCC, 2006).
Land use, land-use change and forestry (LULUCF) In the
context of national greenhouse gas (GHG) inventories under the
United Nations Framework Convention on Climate Change (UNFCCC,
), LULUCF is a GHG inventory sector that covers anthropogenic
emissions and removals of GHG in managed lands, excluding non-
CO2 agricultural emissions. Following the 2006 IPCC Guidelines
for National GHG Inventories, ‘anthropogenic’ land-related GHG
fluxes are defined as all those occurring on ‘managed land’, i.e.,
‘where human interventions and practices have been applied to
perform production, ecological or social functions’. Since managed
land may include carbon dioxide (CO2) removals not considered
as ‘anthropogenic’ in some of the scientific literature assessed in
this report (e.g., removals associated with CO2 fertilisation and
N deposition), the land-related net GHG emission estimates from
global models included in this report are not necessarily directly
comparable with LULUCF estimates in National GHG Inventories. See
also Land-use change (LUC).
Latent heat flux The turbulent flux of heat from the Earth’s
surface to the atmosphere that is associated with evaporation or
condensation of water vapour at the surface; a component of the
surface energy budget. See also Atmosphere, and Flux.
Leakage The effects of policies that result in a displacement of the
environmental impact, thereby counteracting the intended effects of
the initial policies.
Lifecycle assessment (LCA) Compilation and evaluation of the
inputs, outputs and the potential environmental impacts of a product
or service throughout its life cycle (ISO, 2018).
Likelihood The chance of a specific outcome occurring, where this
might be estimated probabilistically. Likelihood is expressed in this
report using a standard terminology (Mastrandrea et al., 2010). See
also Agreement, Evidence, Confidence, and Uncertainty.
Livelihood The resources used and the activities undertaken in
order to live. Livelihoods are usually determined by the entitlements
and assets to which people have access. Such assets can be
categorised as human, social, natural, physical, or financial.
Local knowledge The understandings and skills developed
by individuals and populations, specific to the places where they
live. Local knowledge informs decision-making about fundamental
aspects of life, from day-to-day activities to longer term actions.
This knowledge is a key element of the social and cultural systems
which influence observations of, and responses to climate change;
it also informs governance decisions (UNESCO, 2018). See also
Indigenous knowledge.


Lock-in A situation in which the future development of a system,
including infrastructure, technologies, investments, institutions, and
behavioural norms, is determined or constrained (‘locked in’) by
historic developments.
Long-lived climate forcers (LLCF) A set of well-mixed
greenhouse gases with long atmospheric lifetimes. This set of
compounds includes carbon dioxide (CO2) and nitrous oxide (N2O),
together with some fluorinated gases. They have a warming effect on
climate. These compounds accumulate in the atmosphere at decadal
to centennial timescales, and their effect on climate hence persists
for decades to centuries after their emission. On timescales of
decades to a century already emitted emissions of long-lived climate
forcers can only be abated by greenhouse gas removal (GGR). See
also Short-lived climate forcers (SLCF).
Loss and Damage, and losses and damages Research has
taken Loss and Damage (capitalised letters) to refer to political
debate under the United Nations Framework Convention on Climate
Change (UNFCCC) following the establishment of the Warsaw
Mechanism on Loss and Damage in 2013, which is to ‘address loss
and damage associated with impacts of climate change, including
extreme events and slow onset events, in developing countries that
are particularly vulnerable to the adverse effects of climate change.’
Lowercase letters (losses and damages) have been taken to refer
broadly to harm from (observed) impacts and (projected) risks
(Mechler et al., 2018).
Maladaptive actions (Maladaptation) Actions that may lead
to increased risk of adverse climate-related outcomes, including via
increased greenhouse gas (GHG) emissions, increased vulnerability
to climate change, or diminished welfare, now or in the future.
Maladaptation is usually an unintended consequence.
Malnutrition Deficiencies, excesses, or imbalances in a person’s
intake of energy and/or nutrients. The term malnutrition addresses
three broad groups of conditions: undernutrition, which includes
wasting (low weight-for-height), stunting (low height-for-age)
and underweight (low weight-for-age); micronutrient-related
malnutrition, which includes micronutrient deficiencies (a lack of
important vitamins and minerals) or micronutrient excess; and
overweight, obesity and diet-related noncommunicable diseases
(such as heart disease, stroke, diabetes and some cancers) (WHO,
). Micronutrient deficiencies are sometimes termed ‘hidden
hunger’ to emphasise that people can be malnourished in the sense
of deficient without being deficient in calories. Hidden hunger can
apply even where people are obese.
Managed forest Forests subject to human interventions (notably
silvicultural management such as planting, pruning, thinning), timber
and fuelwood harvest, protection (fire suppression, insect supression)
and management for amenity values or conservation, with defined
geographical boundaries (Ogle et al., 2018). [Note: For a discussion
of the term ‘forest’ in the context of National GHG inventories, see
the 2006 IPCC Guidelines for National GHG Inventories.] See also
Managed land.
Managed grassland Grasslands on which human interventions
are carried out, such as grazing domestic livestock or hay removal.
Managed land In the context of national greenhouse gas (GHG)
inventories under the United Nations Framework Convention on
Climate Change (UNFCCC), the 2006 IPCC Guidelines for National
GHG Inventories (IPCC, 2006) defines managed land ‘where human
interventions and practices have been applied to perform production,
ecological or social functions’. The IPCC (2006) defines anthropogenic
GHG emissions and removals in the LULUCF sector as all those
occurring on ‘managed land’. The key rationale for this approach is
that the preponderance of anthropogenic effects occurs on managed
lands. [Note: More details can be found in 2006 IPCC Guidelines for
National GHG Inventories, Volume 4, Chapter 1.]
Market failure When private decisions are based on market
prices that do not reflect the real scarcity of goods and services but
rather reflect market distortions, they do not generate an efficient
allocation of resources but cause welfare losses. A market distortion
is any event in which a market reaches a market clearing price
that is substantially different from the price that a market would
achieve while operating under conditions of perfect competition and
state enforcement of legal contracts and the ownership of private
property. Examples of factors causing market prices to deviate from
real economic scarcity are environmental externalities, public goods,
monopoly power, information asymmetry, transaction costs, and nonrational
behaviour.
Measurement, reporting and verification (MRV)
Measurement
‘The process of data collection over time, providing basic datasets,
including associated accuracy and precision, for the range of
relevant variables. Possible data sources are field measurements,
field observations, detection through remote sensing and interviews’
(UN REDD, 2009).
Reporting
‘The process of formal reporting of assessment results to the UNFCCC,
according to predetermined formats and according to established
standards, especially the Intergovernmental Panel on Climate Change
(IPCC) Guidelines and GPG (Good Practice Guidance)’ (UN REDD,
).
Verification
‘The process of formal verification of reports, for example, the
established approach to verify national communications and national
inventory reports to the UNFCCC’ (UN REDD, 2009).
Megadrought See Drought.
Methane (CH4) One of the six greenhouse gases (GHGs) to be
mitigated under the Kyoto Protocol. Methane is the major component
of natural gas and associated with all hydrocarbon fuels. Significant
anthropogenic emissions also occur as a result of animal husbandry
and paddy rice production. Methane is also produced naturally
where organic matter decays under anaerobic conditions, such as
in wetlands.
Migrant See Migration.
Migration ‘The movement of a person or a group of persons, either
across an international border, or within a State. It is a population
movement, encompassing any kind of movement of people, whatever
its length, composition and causes; it includes migration of refugees,

Glossary Annex I
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displaced persons, economic migrants, and persons moving for other
purposes, including family reunification’ (IOM, 2018).
Migrant
‘Any person who is moving or has moved across an international
border or within a State away from his/her habitual place of residence,
regardless of (1) the person’s legal status; (2) whether the movement
is voluntary or involuntary; (3) what the causes for the movement are;
or (4) what the length of the stay is’ (IOM, 2018).
See also (Internal) Displacement.
Millennium Development Goals (MDGs) A set of eight
time-bound and measurable goals for combating poverty, hunger,
disease, illiteracy, discrimination against women and environmental
degradation. These goals were agreed at the UN Millennium Summit
in 2000 together with an action plan to reach the goals by 2015.
Mitigation (of climate change) A human intervention to
reduce emissions or enhance the sinks of greenhouse gases.
Mitigation behaviour See Human behaviour.
Mitigation measures In climate policy, mitigation measures are
technologies, processes or practices that contribute to mitigation,
for example renewable energy technologies, waste minimisation
processes, public transport commuting practices.
Mitigation option A technology or practice that reduces
greenhouse gas (GHG) emissions or enhances sinks.
Mitigation pathways See Pathways.
Mitigation scenario A plausible description of the future that
describes how the (studied) system responds to the implementation
of mitigation policies and measures. See also Emission scenario,
Pathways, Socio-economic scenarios, and Stabilisation (of GHG or
CO2-equivalent concentration).
Monitoring and evaluation (M&E) Mechanisms put in place
at national to local scales to respectively monitor and evaluate
efforts to reduce greenhouse gas emissions and/or adapt to the
impacts of climate change with the aim of systematically identifying,
characterising and assessing progress over time.
Motivation (of an individual) An individual’s reason or
reasons for acting in a particular way; individuals may consider
various consequences of actions, including financial, social, affective,
and environmental consequences. Motivation can arise from factors
external or internal to the individual.
Multi-level governance See Governance.
Narratives (in the context of scenarios) Qualitative
descriptions of plausible future world evolutions, describing
the characteristics, general logic and developments underlying
a particular quantitative set of scenarios. Narratives are also referred
to in the literature as ‘storylines’. See also Scenario, Scenario storyline,
and Pathways.
Nationally Determined Contributions (NDCs) A term used
under the United Nations Framework Convention on Climate Change
(UNFCCC) whereby a country that has joined the Paris Agreement
outlines its plans for reducing its emissions. Some countries NDCs
also address how they will adapt to climate change impacts, and
what support they need from, or will provide to, other countries to
adopt low-carbon pathways and to build climate resilience. According
to Article 4 paragraph 2 of the Paris Agreement, each Party shall
prepare, communicate and maintain successive NDCs that it intends
to achieve. In the lead up to the 21st Conference of the Parties in
Paris in 2015, countries submitted Intended Nationally Determined
Contributions (INDCs). As countries join the Paris Agreement, unless
they decide otherwise, this INDC becomes their first Nationally
Determined Contribution (NDC).
Negative emissions Removal of greenhouse gases (GHGs) from
the atmosphere by deliberate human activities, i.e., in addition to the
removal that would occur via natural carbon cycle processes. See
also Net negative emissions, Net-zero emissions, Carbon dioxide
removal (CDR), and Greenhouse gas removal (GGR).
Negative emissions technologies An activity or mechanism
that results in negative emissions.
Net negative emissions A situation of net negative emissions is
achieved when, as result of human activities, more greenhouse gases
(GHG) are removed from the atmosphere than are emitted into it.
Where multiple greenhouse gases are involved, the quantification of
negative emissions depends on the climate metric chosen to compare
emissions of different gases (such as global warming potential, global
temperature change potential, and others, as well as the chosen time
horizon). See also Negative emissions, Net-zero emissions and Netzero
CO2 emissions.
Net-zero CO2 emissions Conditions in which any remaining
anthropogenic carbon dioxide (CO2) emissions are balanced by
anthropogenic CO2 removals over a specified period. See also Netzero
emissions, and Net negative emissions.
Net-zero emissions Net-zero emissions are achieved when
emissions of greenhouse gases (GHGs) to the atmosphere are
balanced by anthropogenic removals. Where multiple greenhouse
gases are involved, the quantification of net-zero emissions depends
on the climate metric chosen to compare emissions of different
gases (such as global warming potential, global temperature
change potential, and others, as well as the chosen time horizon).
See also Net-zero CO2 emissions, Negative emissions, and Net
negative emissions.
Nitrous oxide (N2O) One of the six greenhouse gases (GHGs)
to be mitigated under the Kyoto Protocol. The main anthropogenic
source of N2O is agriculture (soil and animal manure management),
but important contributions also come from sewage treatment,
fossil fuel combustion, and chemical industrial processes. N2O is also
produced naturally from a wide variety of biological sources in soil
and water, particularly microbial action in wet tropical forests.
Non-overshoot pathways See Pathways.
Nutrition transition A predictable change in dietary patterns
associated with a country’s economic development whereby
‘problems of under- and overnutrition often coexist, reflecting the
trends in which an increasing proportion of people consume the types
of diets associated with a number of chronic diseases’ (Popkin, 1994).


Ocean acidification (OA) A reduction in the pH of the ocean,
accompanied by other chemical changes, over an extended period,
typically decades or longer, which is caused primarily by uptake
of carbon dioxide (CO2) from the atmosphere, but can also be
caused by other chemical additions or subtractions from the ocean.
Anthropogenic ocean acidification refers to the component of pH
reduction that is caused by human activity (IPCC, 2011, p. 37). See
also Climate change.
Ocean fertilisation Deliberate increase of nutrient supply to
the near-surface ocean in order to enhance biological production
through which additional carbon dioxide (CO2) from the atmosphere
is sequestered. This can be achieved by the addition of micronutrients
or macro-nutrients. Ocean fertilisation is regulated by the
London Protocol
Overshoot See Temperature overshoot.
Overshoot pathways See Pathways.
Ozone (O3) The triatomic form of oxygen (O3). In the troposphere,
it is created both naturally and by photochemical reactions involving
gases resulting from human activities (smog). Tropospheric ozone acts
as a greenhouse gas (GHG). In the stratosphere, it is created by the
interaction between solar ultraviolet radiation and molecular oxygen
(O2). Stratospheric ozone plays a dominant role in the stratospheric
radiative balance. Its concentration is highest in the ozone layer.
Paris Agreement The Paris Agreement under the United Nations
Framework Convention on Climate Change (UNFCCC) was adopted on
December 2015 in Paris, France, at the 21st session of the Conference
of the Parties (COP) to the UNFCCC. The agreement, adopted by 196
Parties to the UNFCCC, entered into force on 4 November 2016 and
as of May 2018 had 195 Signatories and was ratified by 177 Parties.
One of the goals of the Paris Agreement is ‘Holding the increase in the
global average temperature to well below 2°C above pre-industrial
levels and pursuing efforts to limit the temperature increase to 1.5°C
above pre-industrial levels’, recognising that this would significantly
reduce the risks and impacts of climate change. Additionally, the
Agreement aims to strengthen the ability of countries to deal with
the impacts of climate change. The Paris Agreement is intended
to become fully effective in 2020. See also Kyoto Protocol, and
Nationally Determined Contributions (NDCs).
Participatory governance See Governance.
Pasture Area covered with grass or other plants used or suitable
for grazing of livestock; grassland.
Pathways The temporal evolution of natural and/or human
systems towards a future state. Pathway concepts range from sets
of quantitative and qualitative scenarios or narratives of potential
futures to solution-oriented decision-making processes to achieve
desirable societal goals. Pathway approaches typically focus on
biophysical, techno-economic, and/or socio-behavioural trajectories
and involve various dynamics, goals, and actors across different scales.
.5°C pathway
A pathway of emissions of greenhouse gases and other climate
forcers that provides an approximately one-in-two to two-in-three
chance, given current knowledge of the climate response, of global
warming either remaining below 1.5°C or returning to 1.5°C by
around 2100 following an overshoot.
See also Temperature overshoot.
Adaptation pathways
A series of adaptation choices involving trade-offs between shortterm
and long-term goals and values. These are processes of
deliberation to identify solutions that are meaningful to people in
the context of their daily lives and to avoid potential maladaptation.
Development pathways
Development pathways are trajectories based on an array of social,
economic, cultural, technological, institutional, and biophysical
features that characterise the interactions between human and
natural systems and outline visions for the future, at a particular scale.
Mitigation pathways
A mitigation pathway is a temporal evolution of a set of mitigation
scenario features, such as greenhouse gas (GHG) emissions and
socio-economic development.
Overshoot pathways
Pathways that exceed the stabilisation level (concentration, forcing,
or temperature) before the end of a time horizon of interest
(e.g., before 2100) and then decline towards that level by that time.
Once the target level is exceeded, removal by sinks of greenhouse
gases (GHGs) is required. See also Temperature overshoot.
Non-overshoot pathways
Pathways that stay below the stabilisation level (concentration,
forcing, or temperature) during the time horizon of interest (e.g.,
until 2100).
Representative Concentration Pathways (RCPs)
Scenarios that include time series of emissions and concentrations
of the full suite of greenhouse gases (GHGs) and aerosols and
chemically active gases, as well as land use/land cover (Moss et
al., 2008). The word representative signifies that each RCP provides
only one of many possible scenarios that would lead to the specific
radiative forcing characteristics. The term pathway emphasises the
fact that not only the long-term concentration levels, but also the
trajectory taken over time to reach that outcome are of interest
(Moss et al., 2010). RCPs were used to develop climate projections in
CMIP5. See also Coupled Model Intercomparison Project (CMIP), and
Shared Socio-economic Pathways (SSPs).
• RCP2.6: One pathway where radiative forcing peaks at
approximately 3 W m–2 and then declines to be limited at
.6 W m–2 in 2100 (the corresponding Extended Concentration
Pathway, or ECP, has constant emissions after 2100).
• RCP4.5 and RCP6.0: Two intermediate stabilisation pathways in
which radiative forcing is limited at approximately 4.5 W m–2
and 6.0 W m–2 in 2100 (the corresponding ECPs have constant
concentrations after 2150).
• RCP8.5: One high pathway which leads to >8.5 W m–2 in 2100
(the corresponding ECP has constant emissions after 2100 until
and constant concentrations after 2250).
Shared Socio-economic Pathways (SSPs)
Shared Socio-economic Pathways (SSPs) were developed to
complement the Representative Concentration Pathways (RCPs) with
varying socio-economic challenges to adaptation and mitigation

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(O’Neill et al., 2014). Based on five narratives, the SSPs describe
alternative socio-economic futures in the absence of climate policy
intervention, comprising sustainable development (SSP1), regional
rivalry (SSP3), inequality (SSP4), fossil–fueled development (SSP5),
and a middle-of-the-road development (SSP2) (O’Neill et al., 2017;
Riahi et al., 2017). The combination of SSP-based socio-economic
scenarios and RCP-based climate projections provides an integrative
frame for climate impact and policy analysis.
Transformation pathways
Trajectories describing consistent sets of possible futures of
greenhouse gas (GHG) emissions, atmospheric concentrations,
or global mean surface temperatures implied from mitigation and
adaptation actions associated with a set of broad and irreversible
economic, technological, societal, and behavioural changes. This can
encompass changes in the way energy and infrastructure are used
and produced, natural resources are managed and institutions are set
up and in the pace and direction of technological change (TC).
See also Scenario, Scenario storyline, Emission scenario, Mitigation
scenario, Baseline scenario, Stabilisation (of GHG or CO2-equivalent
concentration), and Narratives.
Peat Soft, porous or compressed, sedentary deposit of which
a substantial portion is partly decomposed plant material with high
water content in the natural state (up to about 90 percent) (IPCC,
). See also Peatlands.
Peatlands Peatland is a land where soils are dominated by peat.
See also Reservoir, and Sink.
Peri-urban areas Parts of a city that appear to be quite rural
but are in reality strongly linked functionally to the city in its daily
activities.
Permafrost Ground (soil or rock and included ice and
organic material) that remains at or below 0°C for at least two
consecutive years.
pH A dimensionless measure of the acidity of a solution given
by its concentration of hydrogen ions ([H+]). pH is measured on
a logarithmic scale where pH = -log10[H+]. Thus, a pH decrease of
unit corresponds to a 10-fold increase in the concentration of H+, or
acidity. See also Ocean acidification.
Phenology The relationship between biological phenomena that
recur periodically (e.g., development stages, migration) and climate
and seasonal changes.
Planetary health The Rockefeller-Lancet Commission defines
planetary health as ‘the achievement of the highest attainable
standard of health, well-being, and equity worldwide through
judicious attention to the human systems — political, economic, and
social — that shape the future of humanity and the Earth’s natural
systems that define the safe environmental limits within which
humanity can flourish. Put simply, planetary health is the health of
human civilisation and the state of the natural systems on which it
depends’ (Whitmee et al., 2015).
Political economy The set of interlinked relationships between
people, the state, society and markets as defined by law, politics,
economics, customs and power that determine the outcome of
trade and transactions and the distribution of wealth in a country
or economy.
Pool, carbon and nitrogen A reservoir in the earth system where
elements, such as carbon and nitrogen, reside in various chemical
forms for a period of time.
Poverty A complex concept with several definitions stemming
from different schools of thought. It can refer to material
circumstances (such as need, pattern of deprivation or limited
resources), economic conditions (such as standard of living, inequality
or economic position) and/or social relationships (such as social class,
dependency, exclusion, lack of basic security or lack of entitlement).
See also Poverty eradication.
Poverty eradication A set of measures to end poverty in all its
forms everywhere. See also Sustainable Development Goals (SDGs).
Precursors Atmospheric compounds that are not greenhouse
gases (GHGs) or aerosols, but that have an effect on GHG or aerosol
concentrations by taking part in physical or chemical processes
regulating their production or destruction rates. See also Aerosol, and
Greenhouse gas (GHG).
Pre-industrial The multi-century period prior to the onset of
large-scale industrial activity around 1750. The reference period
–1900 is used to approximate pre-industrial global mean
surface temperature (GMST). See also Industrial revolution.
Primary production The synthesis of organic compounds
by plants and microbes, on land or in the ocean, primarily by
photosynthesis using light and carbon dioxide (CO2) as sources
of energy and carbon respectively. It can also occur through
chemosynthesis, using chemical energy, e.g., in deep sea vents.
Gross Primary Production (GPP)
The total amount of carbon fixed by photosynthesis over a specific
time period.
Net primary production (NPP)
The amount of carbon accumulated through photosynthesis minus
the amount lost by plant respiration over a specified time period that
would prevail in the absence of land use.
Procedural equity See Equity
Procedural rights See Human rights.
Projection A potential future evolution of a quantity or set of
quantities, often computed with the aid of a model. Unlike predictions,
projections are conditional on assumptions concerning, for example,
future socio-economic and technological developments that may
or may not be realised. See also Climate projection, Scenario,
and Pathways.
Radiative forcing The change in the net, downward minus
upward, radiative flux (expressed in W m–2) at the tropopause or
top of atmosphere due to a change in a driver of climate change,
such as a change in the concentration of carbon dioxide (CO2),
the concentration of volcanic aerosols or the output of the Sun.
The traditional radiative forcing is computed with all tropospheric
properties held fixed at their unperturbed values, and after allowing
for stratospheric temperatures, if perturbed, to readjust to radiativedynamical
equilibrium. Radiative forcing is called instantaneous if no


change in stratospheric temperature is accounted for. The radiative
forcing once rapid adjustments are accounted for is termed the
effective radiative forcing. Radiative forcing is not to be confused with
cloud radiative forcing, which describes an unrelated measure of the
impact of clouds on the radiative flux at the top of the atmosphere.
Reasons for concern (RFCs) Elements of a classification
framework, first developed in the IPCC Third Assessment Report,
which aims to facilitate judgments about what level of climate
change may be dangerous (in the language of Article 2 of the
UNFCCC) by aggregating risks from various sectors, considering
hazards, exposures, vulnerabilities, capacities to adapt, and the
resulting impacts.
Reducing Emissions from Deforestation and Forest
Degradation (REDD+) REDD+ refers to reducing emissions
from deforestation; reducing emissions from forest degradation;
conservation of forest carbon stocks; sustainable management
of forests; and enhancement of forest carbon stocks (see UNFCCC
decision 1/CP.16, para. 70).
Reference period The period relative to which anomalies are
computed. See also Anomalies.
Reference scenario See Baseline scenario.
Reforestation Conversion to forest of land that has previously
contained forests but that has been converted to some other use.
[Note: For a discussion of the term forest and related terms such
as afforestation, reforestation and deforestation in the context
of reporting and accounting Article 3.3 and 3.4 activities under
the Kyoto Protocol, see 2013 Revised Supplementary Methods
and Good Practice Guidance Arising from the Kyoto Protocol.] See
also Afforestation, Deforestation, and Reducing Emissions from
Deforestation and Forest Degradation (REDD+).
Region A relatively large-scale land or ocean area characterised
by specific geographical and climatological features. The climate of
a land-based region is affected by regional and local scale features
like topography, land use characteristics and large water bodies, as
well as remote influences from other regions, in addition to global
climate conditions. The IPCC defines a set of standard regions for
analyses of observed climate trends and climate model projections
(see IPCC 2018, Fig. 3.2; AR5, SREX).
Remaining carbon budget Cumulative global carbon dioxide
(CO2) emissions from the start of 2018 to the time that CO2 emissions
reach net-zero that would result, at some probability, in limiting
global warming to a given level, accounting for the impact of other
anthropogenic emissions. See also Carbon budget.
Representative concentration pathways (RCPs) See
Pathways.
Reservoir A component or components of the climate system
where a greenhouse gas (GHG) or a precursor of a greenhouse gas is
stored (UNFCCC Article 1.7).
Resilience The capacity of interconnected social, economic
and ecological systems to cope with a hazardous event, trend or
disturbance, responding or reorganising in ways that maintain their
essential function, identity and structure. Resilience is a positive
attribute when it maintains capacity for adaptation, learning and/
or transformation (adapted from the Arctic Council, 2013). See also
Hazard, Risk, and Vulnerability.
Respiration The process whereby living organisms convert
organic matter to carbon dioxide (CO2), releasing energy and
consuming molecular oxygen.
Rewetting ‘The deliberate action of changing a drained soil
into a wet soil, e.g. by blocking drainage ditches, disabling pumping
facilities or breaching obstructions’ (IPCC, 2013). See also Drainage.
Risk The potential for adverse consequences for human or
ecological systems, recognising the diversity of values and objectives
associated with such systems. In the context of climate change,
risks can arise from potential impacts of climate change as well as
human responses to climate change. Relevant adverse consequences
include those on lives, livelihoods, health and well-being, economic,
social and cultural assets and investments, infrastructure, services
(including ecosystem services), ecosystems and species.
In the context of climate change impacts, risks result from dynamic
interactions between climate-related hazards with the exposure
and vulnerability of the affected human or ecological system to the
hazards. Hazards, exposure and vulnerability may each be subject
to uncertainty in terms of magnitude and likelihood of occurrence,
and each may change over time and space due to socio-economic
changes and human decision-making (see also risk management,
adaptation, and mitigation).
In the context of climate change responses, risks result from the
potential for such responses not achieving the intended objective(s),
or from potential trade-offs with, or negative side-effects on, other
societal objectives, such as the Sustainable Development Goals (see
also risk trade-off). Risks can arise for example from uncertainty in
implementation, effectiveness or outcomes of climate policy, climaterelated
investments, technology development or adoption, and
system transitions.
Risk assessment The qualitative and/or quantitative scientific
estimation of risks. See also Risk management, and Risk perception.
Risk management Plans, actions, strategies or policies to reduce
the likelihood and/or magnitude of adverse potential consequences,
based on assessed or perceived risks. See also Risk assessment, and
Risk perception.
Risk perception The subjective judgment that people make about
the characteristics and severity of a risk. See also Risk assessment,
and Risk management.
Risk trade-off The change in portfolio of risks that occurs when
a countervailing risk is generated (knowingly or inadvertently) by an
intervention to reduce the target risk (Wiener and Graham, 2009).
See also Adverse side-effect, and Co-benefits.
Runoff The flow of water over the surface or through the
subsurface, which typically originates from the part of liquid
precipitation and/or snow/ice melt that does not evaporate or
refreeze, and is not transpired. See also Hydrological cycle.
Saline soils Soils with levels of soluble salts (commonly sulphates
and chlorides of calcium and magnesium) in the saturation extract

Glossary Annex I
AI
high enough to negatively affect plant growth. Saline soils are usually
flocculated and have good water permeability (Well and Brady, 2016).
See also Soil salinity and Sodic soils.
Scenario A plausible description of how the future may develop
based on a coherent and internally consistent set of assumptions
about key driving forces (e.g., rate of technological change (TC),
prices) and relationships. Note that scenarios are neither predictions
nor forecasts, but are used to provide a view of the implications
of developments and actions. See also Baseline scenario, Emission
scenario, Mitigation scenario and Pathways.
Scenario storyline A narrative description of a scenario (or
family of scenarios), highlighting the main scenario characteristics,
relationships between key driving forces and the dynamics of their
evolution. Also referred to as ‘narratives’ in the scenario literature.
Sea ice Ice found at the sea surface that has originated from
the freezing of seawater. Sea ice may be discontinuous pieces (ice
floes) moved on the ocean surface by wind and currents (pack ice),
or a motionless sheet attached to the coast (land-fast ice). Sea ice
concentration is the fraction of the ocean covered by ice. Sea ice less
than one year old is called first-year ice. Perennial ice is sea ice that
survives at least one summer. It may be subdivided into second-year
ice and multi-year ice, where multi-year ice has survived at least
two summers.
Sea level change (sea level rise/sea level fall) Change to
the height of sea level, both globally and locally (relative sea level
change) due to (1) a change in ocean volume as a result of a change
in the mass of water in the ocean, (2) changes in ocean volume
as a result of changes in ocean water density, (3) changes in the
shape of the ocean basins and changes in the Earth’s gravitational
and rotational fields, and (4) local subsidence or uplift of the land.
Global mean sea level change resulting from change in the mass
of the ocean is called barystatic. The amount of barystatic sea level
change due to the addition or removal of a mass of water is called
its sea level equivalent (SLE). Sea level changes, both globally and
locally, resulting from changes in water density are called steric.
Density changes induced by temperature changes only are called
thermosteric, while density changes induced by salinity changes
are called halosteric. Barystatic and steric sea level changes do not
include the effect of changes in the shape of ocean basins induced by
the change in the ocean mass and its distribution.
Sea surface temperature (SST) The subsurface bulk
temperature in the top few meters of the ocean, measured by ships,
buoys, and drifters. From ships, measurements of water samples in
buckets were mostly switched in the 1940s to samples from engine
intake water. Satellite measurements of skin temperature (uppermost
layer; a fraction of a millimetre thick) in the infrared or the top
centimetre or so in the microwave are also used, but must be adjusted
to be compatible with the bulk temperature.
Sendai Framework for Disaster Risk Reduction The Sendai
Framework for Disaster Risk Reduction 2015–2030 outlines seven
clear targets and four priorities for action to prevent new, and to
reduce existing disaster risks. The voluntary, non-binding agreement
recognises that the State has the primary role to reduce disaster risk
but that responsibility should be shared with other stakeholders
including local government, the private sector and other stakeholders,
with the aim for the substantial reduction of disaster risk and
losses in lives, livelihoods and health and in the economic, physical,
social, cultural and environmental assets of persons, businesses,
communities and countries.
Sequestration See Uptake and Carbon sequestration.
Shared socio-economic pathways (SSPs) See Pathways.
Short-lived climate forcers (SLCF) A set of compounds that are
primarily composed of those with short lifetimes in the atmosphere
compared to well-mixed greenhouse gases (GHGs), and are also
referred to as near-term climate forcers. This set of compounds
includes methane (CH4), which is also a well-mixed greenhouse gas,
as well as ozone (O3) and aerosols, or their precursors, and some
halogenated species that are not well-mixed greenhouse gases.
These compounds do not accumulate in the atmosphere at decadal to
centennial timescales, and so their effect on climate is predominantly
in the first decade after their emission, although their changes can still
induce long-term climate effects such as sea level change. Their effect
can be cooling or warming. A subset of exclusively warming shortlived
climate forcers is referred to as short-lived climate pollutants.
See also Long-lived climate forcers (LLCF).
Short-lived climate pollutants (SLCP) See Short-lived climate
forcers (SLCF).
Sink Any process, activity or mechanism which removes
a greenhouse gas, an aerosol or a precursor of a greenhouse gas
from the atmosphere (UNFCCC Article 1.8). See also Sequestration,
Source, and Uptake.
Small Island Developing States (SIDS) Small Island
Developing States (SIDS), as recognised by the United Nations
OHRLLS (Office of the High Representative for the Least Developed
Countries, Landlocked Developing Countries and Small Island
Developing States), are a distinct group of developing countries
facing specific social, economic and environmental vulnerabilities
(UN-OHRLLS, 2011). They were recognised as a special case both for
their environment and development at the Rio Earth Summit in Brazil
in 1992. Fifty eight countries and territories are presently classified
as SIDS by the UN OHRLLS, with 38 being UN member states and
being Non-UN Members or Associate Members of the Regional
Commissions (UN-OHRLLS, 2018).
Social costs The full costs of an action in terms of social welfare
losses, including external costs associated with the impacts of this
action on the environment, the economy (GDP, employment) and on
the society as a whole.
Social cost of carbon (SCC) The net present value of aggregate
climate damages (with overall harmful damages expressed as
a number with positive sign) from one more tonne of carbon in the
form of carbon dioxide (CO2), conditional on a global emissions
trajectory over time.
Social-ecological system An integrated system that includes
human societies and ecosystems, in which humans are part of
nature. The functions of such a system arise from the interactions and
interdependence of the social and ecological subsystems. The system’s
structure is characterised by reciprocal feedbacks, emphasising that


humans must be seen as a part of, not apart from, nature (Arctic
Council, 2016; Berkes and Folke, 1998).
Social inclusion A process of improving the terms of participation
in society, particularly for people who are disadvantaged, through
enhancing opportunities, access to resources, and respect for rights
(UN DESA 2016).
Social learning A process of social interaction through which
people learn new behaviours, capacities, values, and attitudes.
Societal (social) transformation See Transformation.
Socio-economic scenario A scenario that describes a possible
future in terms of population, gross domestic product (GDP),
and other socio-economic factors relevant to understanding the
implications of climate change. See also Baseline scenario, Emission
scenario, Mitigation scenario, and Pathways.
Socio-technical transitions Where technological change is
associated with social systems and the two are inextricably linked.
Sodic soils Soils with disproportionately high concentration of
sodium (Na+) in relation to calcium (Ca2+) and magnesium (Mg2+)
adsorbed at the cation exchange site on the surface of soil particles.
Sodic soils are characterised by a poor soil structure and poor
aeration (NDSU, 2014). See also Soil salinity.
Soil carbon sequestration (SCS) Land management changes
which increase the soil organic carbon content, resulting in a net
removal of carbon dioxide (CO2) from the atmosphere.
Soil conservation The maintenance of soil fertility through
controlling erosion, preserving soil organic matter, ensuring favourable
soil physical properties, and retaining nutrients (Young, 1989).
Soil erosion The displacement of the soil by the action of water
or wind. Soil erosion is a major process of land degradation.
Soil organic carbon Carbon contained in soil organic matter.
Soil organic matter The organic component of soil, comprising
plant and animal residue at various stages of decomposition, and
soil organisms.
Soil moisture Water stored in the soil in liquid or frozen form.
Root-zone soil moisture is of most relevance for plant activity.
Soil salinity The concentration of soluble salts in the water
extracted from a saturated soil (saturation extract), comprising
chlorides and sulphates of Sodium (Na+), calcium (Ca2+) and
magnesium (Mg2+) as well as carbonate salts (adapted from FAO,
). See also Saline soils, and Sodic soils.
Source Any process or activity which releases a greenhouse gas,
an aerosol or a precursor of a greenhouse gas into the atmosphere
(UNFCCC Article 1.9). See also Sink.
Stabilisation (of GHG or CO2-equivalent concentration)
A state in which the atmospheric concentrations of one greenhouse
gas (GHG) (e.g., carbon dioxide) or of a CO2-equivalent basket of
GHGs (or a combination of GHGs and aerosols) remains constant
over time.
Stranded assets Assets exposed to devaluations or conversion
to ‘liabilities’ because of unanticipated changes in their initially
expected revenues due to innovations and/or evolutions of the
business context, including changes in public regulations at the
domestic and international levels.
Stratosphere The highly stratified region of the atmosphere
above the troposphere extending from about 10 km (ranging from 9
km at high latitudes to 16 km in the tropics on average) to about 50
km altitude. See also Atmosphere, and Troposphere.
Subnational actors State/provincial, regional, metropolitan
and local/municipal governments as well as non-party stakeholders,
such as civil society, the private sector, cities and other subnational
authorities, local communities and indigenous peoples.
Substantive rights See Human rights.
Supply-side measures See Demand and supply-side measures.
Surface temperature See Global mean surface temperature
(GMST), Land surface air temperature, and Sea surface
temperature (SST).
Sustainability A dynamic process that guarantees the
persistence of natural and human systems in an equitable manner.
Sustainable development (SD) Development that meets
the needs of the present without compromising the ability of
future generations to meet their own needs (WCED, 1987) and
balances social, economic and environmental concerns. See also
Sustainable Development Goals (SDGs), and Development pathways
(under Pathways).
Sustainable Development Goals (SDGs) The 17 global goals
for development for all countries established by the United Nations
through a participatory process and elaborated in the 2030 Agenda
for Sustainable Development, including ending poverty and hunger;
ensuring health and well-being, education, gender equality, clean
water and energy, and decent work; building and ensuring resilient
and sustainable infrastructure, cities and consumption; reducing
inequalities; protecting land and water ecosystems; promoting peace,
justice and partnerships; and taking urgent action on climate change.
See also Sustainable development (SD).
Sustainable forest management The stewardship and use of
forests and forest lands in a way, and at a rate, that maintains their
biodiversity, productivity, regeneration capacity, vitality and their
potential to fulfil, now and in the future, relevant ecological, economic
and social functions, at local, national, and global levels, and that
does not cause damage to other ecosystems (Forest Europe, 1993).
Sustainable intensification (of agriculture) Increasing yields
from the same area of land while decreasing negative environmental
impacts of agricultural production and increasing the provision of
environmental services (CGIAR, 2019). [Note: this definition is based
on the concept of meeting demand from a finite land area, but it
is scale-dependent. Sustainable intensification at a given scale (e.g.,
global or national) may require a decrease in production intensity
at smaller scales and in particular places (often associated with
previous, unsustainable, intensification) to achieve sustainability
(Garnett et al., 2013).]

Glossary Annex I
AI
Sustainable land management The stewardship and use of
land resources, including soils, water, animals and plants, to meet
changing human needs, while simultaneously ensuring the long-term
productive potential of these resources and the maintenance of their
environmental functions (Adapted from WOCAT, undated).
Technology transfer The exchange of knowledge, hardware and
associated software, money and goods among stakeholders, which
leads to the spread of technology for adaptation or mitigation. The
term encompasses both diffusion of technologies and technological
cooperation across and within countries.
Teleconnections A statistical association between climate
variables at widely separated, geographically-fixed spatial locations.
Teleconnections are caused by large spatial structures such as basinwide
coupled modes of ocean-atmosphere variability, Rossby wavetrains,
mid-latitude jets and storm tracks, etc.
Temperature overshoot The temporary exceedance of a
specified level of global warming, such as 1.5°C. Overshoot implies
a peak followed by a decline in global warming, achieved through
anthropogenic removal of carbon dioxide (CO2) exceeding remaining
CO2 emissions globally. See also Pathways (Subterms: Overshoot
pathways, Non-overshoot Pathways).
Tier In the context of the IPCC Guidelines for National Greenhouse
Gas Inventories, a tier represents a level of methodological complexity.
Usually three tiers are provided. Tier 1 is the basic method, Tier 2
intermediate and Tier 3 most demanding in terms of complexity
and data requirements. Tiers 2 and 3 are sometimes referred to as
higher tier methods and are generally considered to be more accurate
(IPCC, 2019).
Tipping point A level of change in system properties beyond
which a system reorganises, often abruptly, and does not return to
the initial state even if the drivers of the change are abated. For the
climate system, it refers to a critical threshold beyond which global
or regional climate changes from one stable state to another stable
state. Tipping points are also used when referring to impact: the term
can imply that an impact tipping point is (about to be) reached in
a natural or human system. See also Irreversibility.
Transformation A change in the fundamental attributes of
natural and human systems.
Societal (social) transformation
A profound and often deliberate shift initiated by communities toward
sustainability, facilitated by changes in individual and collective
values and behaviours, and a fairer balance of political, cultural, and
institutional power in society.
Transformation pathways See Pathways.
Transformational adaptation See Adaptation.
Transformative change A system wide change that alters the
fundamental attributes of the system.
Transient climate response to cumulative CO2 emissions
(TCRE) The transient global average surface temperature change
per unit cumulative carbon dioxide (CO2) emissions, usually 1000
GtC. TCRE combines both information on the airborne fraction of
cumulative CO2 emissions (the fraction of the total CO2 emitted that
remains in the atmosphere, which is determined by carbon cycle
processes) and on the transient climate response (TCR). See also
Transient climate response (TCR) (under Climate sensitivity).
Transit-oriented development (TOD) An approach to urban
development that maximises the amount of residential, business and
leisure space within walking distance of efficient public transport, so
as to enhance mobility of citizens, the viability of public transport and
the value of urban land in mutually supporting ways.
Transition The process of changing from one state or condition to
another in a given period of time. Transition can occur in individuals,
firms, cities, regions and nations, and can be based on incremental or
transformative change.
Tropical cyclone The general term for a strong, cyclonic-scale
disturbance that originates over tropical oceans. Distinguished from
weaker systems (often named tropical disturbances or depressions)
by exceeding a threshold wind speed. A tropical storm is a tropical
cyclone with one-minute average surface winds between 18 and
m s–1. Beyond 32 m s–1, a tropical cyclone is called a hurricane,
typhoon, or cyclone, depending on geographic location. See also
Extratropical cyclone.
Troposphere The lowest part of the atmosphere, from the surface
to about 10 km in altitude at mid-latitudes (ranging from 9 km at
high latitudes to 16 km in the tropics on average), where clouds and
weather phenomena occur. In the troposphere, temperatures generally
decrease with height. See also Atmosphere, and Stratosphere.
Uncertainty A state of incomplete knowledge that can result
from a lack of information or from disagreement about what is
known or even knowable. It may have many types of sources,
from imprecision in the data to ambiguously defined concepts or
terminology, incomplete understanding of critical processes, or
uncertain projections of human behaviour. Uncertainty can therefore
be represented by quantitative measures (e.g., a probability density
function) or by qualitative statements (e.g., reflecting the judgment
of a team of experts) (see IPCC, 2004; Mastrandrea et al., 2010; Moss
and Schneider, 2000). See also Confidence, and Likelihood.
United Nations Convention to Combat Desertification
(UNCCD) A legally binding international agreement linking
environment and development to sustainable land management,
established in 1994. The Convention’s objective is ‘to combat
desertification and mitigate the effects of drought in countries
experiencing drought and/or desertification’. The Convention
specifically addresses the arid, semi-arid and dry sub-humid areas,
known as the drylands, and has a particular focus on Africa. As of
October 2018, the UNCCD had 197 Parties.
United Nations Framework Convention on Climate Change
(UNFCCC) The UNFCCC was adopted in May 1992 and opened for
signature at the 1992 Earth Summit in Rio de Janeiro. It entered into
force in March 1994 and as of May 2018 had 197 Parties (196 States
and the European Union). The Convention’s ultimate objective is the
‘stabilisation of greenhouse gas concentrations in the atmosphere
at a level that would prevent dangerous anthropogenic interference
with the climate system’. The provisions of the Convention are
pursued and implemented by two treaties: the Kyoto Protocol and
the Paris Agreement.


Urban green infrastructure Public and private green spaces,
including remnant native vegetation, parks, private gardens, golf
courses, street trees, urban farming and engineered options such
as green roofs, green walls, biofilters and raingardens (Norton et
al., 2015).
Urban and Peri-urban agriculture ‘The cultivation of crops and
rearing of animals for food and other uses within and surrounding
the boundaries of cities, including fisheries and forestry’ (EPRS, 2014).
Uptake The addition of a substance of concern to a reservoir. See
also Carbon sequestration, and Sink.
Vegetation browning A decrease in photosynthetically active
plant biomass which is inferred from satellite observations.
Vegetation greening An increase in photosynthetically active
plant biomass which is inferred from satellite observations.
Vulnerability The propensity or predisposition to be adversely
affected. Vulnerability encompasses a variety of concepts and
elements including sensitivity or susceptibility to harm and lack of
capacity to cope and adapt. See also Exposure, Hazard, and Risk.
Water cycle See Hydrological cycle.
Well-being A state of existence that fulfils various human needs,
including material living conditions and quality of life, as well as
the ability to pursue one’s goals, to thrive, and feel satisfied with
one’s life. Ecosystem well-being refers to the ability of ecosystems to
maintain their diversity and quality.
Wetland Land that is covered or saturated by water for all or part
of the year (e.g., peatland).
Terminologies Used in Climate Change
Compiled by Anu Adhikari, Racchya Shah, Sony Baral
and Rajendra Khanal
About IUCN
IUCN, International Union for Conservation of Nature, helps the world find pragmatic
solutions to our most pressing environment and development challenges. It supports
scientific research, manages field projects all over the world and brings governments,
non-government organizations, United Nations agencies, companies and local
communities together to develop and implement policy, laws and best practice.
IUCN is the world’s oldest and largest global environmental network - a democratic
membership union with more than 1,000 government and NGO member organizations,
and almost 12,000 volunteer scientists in more than 160 countries.
IUCN’s work is supported by more than 1,100 professional staff in 60 offices and
hundreds of partners in public, NGO and private sectors around the world. The Union’s
headquarters are located in Gland, near Geneva, Switzerland.
www.iucn.org

A
. Abatement: Abatement is the word which is used to denote the result
of decreased Greenhouse Gases Emission. This can also be taken as an
activity to lessen the effects of Greenhouse Effect.
. Aboveground Biomass: All living biomass above the soil including the
stem, stump, branches, bark, seeds and foliage is known as aboveground
biomass.
. Absolute Humidity: The quantity of water vapour in a given volume of
air expressed by mass is known as absolute humidity.
. Absolute Risk: A quantitative or qualitative prediction of the likelihood
and significance of a given impact is known as absolute risk. In the
Voluntary Carbon Standard (VCS), the level of absolute risk can be
calculated using the ‘likelihood × significance’ methodology. The
calculated risk can then be converted into a risk classification.
. Accelerated Erosion: Erosion is a natural phenomenon which results
in soil losses and water quality degradation. Accelerated erosion is
generally caused by activities that disturb or expose the soil to the
erosive forces of gravity and rainwater. Climatic or weather conditions
combined with human activity can accentuate soil erosion. For example,
severe and intense storm events may increase the rate of accelerated
erosion.
. Acceptable Risk: The level of potential losses that a society or
community considers acceptable given existing social, economic,
political, cultural, technical and environmental conditions is known as
acceptable risk. The term “acceptable risk” describes the likelihood of
an event whose probability of occurrence is small, whose consequences
are so slight, or whose benefits (perceived or real) are so great, that
individuals or groups in society are willing to take or be subjected to the
risk that the event might occur. The concept of acceptable risk evolved
partly from the realization that absolute safety is generally an unachievable
goal, and that even very low exposures to certain toxic substances may
confer some level of risk. The notion of virtual safety corresponding to
an acceptable level of risk emerged as a risk management objective in

cases where such exposures could not be completely or cost-effectively
eliminated.
. Acclimatization: The process of an individual organism adjusting to a
gradual change in its environment (such as a change in temperature,
humidity, photoperiod or pH) allowing it to maintain performance across
a range of environmental conditions is known as acclimatization.
Acclimatization occurs in a short period of time (days to weeks), and
within the organism’s lifetime (compare to adaptation). This may be a
discrete occurrence or may instead represent part of a periodic cycle,
such as a mammal shedding heavy winter fur in favor of a lighter
summer coat. Organisms can adjust their morphological, behavioural,
physical and/or biochemical traits in response to changes in their
environment.
. Adaptability: The ability of a system to adjust to Climate
Change (including climate variability and extremes) to moderate
potential damages, to take advantage of opportunities or to cope with
the consequences is known as adaptability.
. Adaptation: Adjustment in natural or human systems to a new or
changing environment is known as adaptation. Adaptation is a process
by which individuals, communities and countries seek to cope with the
consequences of climate change. ‘Adaptation is not coping’, it is about
the capacity to shift strategies as conditions change and to develop
systems that are resilient and sufficiently flexible to respond to change. It
may be planned or autonomous. Various types of adaptation can be
distinguished, including anticipatory and reactive adaptation, private and
public adaptation, and autonomous and planned adaptation.
. Adaptation Assessment: The practice of identifying options to adapt
to climate change effects and evaluating them in terms of criteria such as
availability, benefits, costs, effectiveness, efficiency and feasibility is known
as adaptation assessment.
. Adaptation Baseline: Any datum (baseline or reference) against which
change is measured is known as adaptation baseline. It might be a
“current baseline,” in which case it represents observable present-day
conditions. It might also be a “future baseline,” which is a projected
future set of conditions excluding the driving factor of interest.

Alternative interpretations of the reference conditions can give rise to
multiple baselines.
. Adaptation Benefits: The avoided damage costs or the accrued
benefits following the adoption and implementation of adaptation
measures is known as adaptation benefits.
. Adaptation Cost: Costs of planning, preparing for, facilitating and
implementing adaptation measures including transition costs is known as
adaptation cost.
. Adaptation Deficit: Failure to adapt adequately to existing climate risks
largely accounts for the adaptation deficit. Controlling and eliminating
this deficit in the course of development is necessary but is not a
sufficient step in the longer-term project of adapting to climate change.
Development decisions that do not properly consider current climate
risks add to the costs and increase the deficit. As Climate Change
accelerates, the adaptation deficit has the potential to rise much higher
unless a serious adaptation program is implemented.
. Adaptation Fund: Fund which was established to finance concrete
adaptation projects and programmes in developing country Parties to
the Kyoto Protocol that are particularly vulnerable to the adverse
effects of Climate Change is known as adaptation fund.
. Adaptation Measures: Measures can be individual interventions or
they consist of packages of related measures. Specific measures might
include actions that promote the chosen policy direction, such as
implementing an irrigation project or setting up a farmer information,
advice and early warning programme. It is usually addressed together;
respond to the need for climate adaptation in distinct but sometimes
overlapping ways. Policies, generally speaking, refer to objectives
together with the means of implementation.
. Adaptation Method: A set and sequence of steps or tasks that should
be followed to accomplish the task that represents a part of large
framework is known as adaptation method. Method can be implemented
through using a number of tools. Examples include methods for
development and use of scenario data in the vulnerability and adaptation
assessment.

. Adaptation Policy Baseline: Any datum against which change is
measured is known as adaptation policy baseline. It includes a
description of adaptations to current climate that are already in place
(e.g. existing risk mitigation policies and programmes).
. Adaptation Policy Framework (APF): Structural process for
developing adaptation strategies, policies, and measures to enhance and
ensure human development in the face of Climate Change including
climate variability is known as adaptation policy framework. The APF is
designed to link Climate Change adaptation to sustainable development
and other global environmental issues. It consists of five basic
components scoping and designing an adaptation project, assessing
current vulnerability, characterizing future climate risks, developing an
adaptation strategy and continuing the adaptation process.
. Adaptation Strategies: These are long-term changes in behaviour and
practice in response to continuing stresses. They are the responses of
people to their analysis of risk. People may respond to climate change
by changing their agricultural practices or using new technologies. For
example, they might start rainwater harvesting or they may try to
diversify their livelihood activities and focus on those less affected by
natural hazards. Certain family members may migrate to another place.
The extent to which people can adapt usually reflects their access to and
ability to use different types of assets. In areas where there are very few
assets or people lack the capacity to utilize them, vulnerability will be
high.
. Adaptation Technologies: It includes both scientific and traditional
technologies. Most adaptation technology focuses on local innovations,
knowledge and practices that are effective in adapting to climatic
hazards. The application of technology in order to reduce the
vulnerability or enhance the resilience of a natural or human system to
the impacts of Climate Change.
. Adaptation to Climate Change: An initiatives and measures to
reduce the vulnerability of natural and human systems against actual or
expected Climate Change effects is known as adaptation to climate
change. Crucial to reducing vulnerability to Climate Change,
understanding how individuals, groups and natural systems can prepare
for and respond to changes in climate is known as adaptation. The

broader concept of adaptation also applies to non-climatic factors such
as soil erosion or surface subsidence.
. Adaptive Capacity: The ability of a system to adjust to climate change
(including climate variability and extremes) to moderate potential
damages, to take advantage of opportunities or to cope with the
consequences is known as adaptive capacity. The potential to adjust in
order to minimize negative impacts and maximize any benefits from
changes in climate is known as adaptive capacity. The whole of
capabilities, resources and institutions of a country or region to
implement effective adaptation measures.
. Additionality: Reduction in emissions by sources or enhancement of
removals by sinks that is additional to any that would occur in the
absence of a Joint Implementation or a Clean Development Mechanism
project activity as defined in the Kyoto Protocol Articles on Joint
Implementation and the Clean Development Mechanism is known as
additionality.
. Adverse Effect: Changes in the physical environment or biota resulting
from climate change which have significant deleterious effects on the
composition, resilience or productivity of natural and managed
ecosystems or on the operation of a socioeconomic systems or on
human health and welfare is known as adverse effect.
. Aerosols: A collection of airborne solid or liquid particles, with a
typical size between 0.01 and 10 mm that reside in the atmosphere for
at least several hours is known as aerosols. Aerosols may be of either
natural or anthropogenic origin. Aerosols may influence climate in two
ways: directly through scattering and absorbing radiation and indirectly
through acting as condensation nuclei for cloud formation or modifying
the optical properties and lifetime of clouds.
. Afforestation: Planting of new forests on lands that historically have
not contained forests or the direct human-induced conversion of land
that has not been forested for a period of at least 50 years to forested
land through planting, seeding and/or the human-induced promotion of
natural seed sources is known as afforestation.

. Aggregate Impacts: Total impacts summed up across sectors and/or
region is known as aggregate impacts. The aggregation of impacts
requires knowledge of (or assumptions about) the relative importance
of impacts in different sectors and regions. Measures of aggregate
impacts include, for example, the total number of people affected, change
in net primary productivity, number of systems undergoing change or
total economic costs.
. Agriculture, Forestry and Other Land Use (AFOLU): This includes
activities related to: Afforestation, Reforestation and Revegetation (ARR),
Agricultural Land Management (ALM), Improved Forest Management
(IFM) and Reduced Emissions from Deforestation and Degradation
(REDD).
. Agroclimatology: The study of climate as to its effect on crops; it
includes, for example, the relation of growth rate and crop yields to the
various climatic factors and hence the optimum and limiting climates for
any given crop is known as agroclimatology.
. Agroecology: The application of ecological principles to the
production of food, fuel, fiber and pharmaceuticals is known as
agroecology. The term encompasses a broad range of approaches and
is considered a science, a movement and a practice.
. Agroforestry: An ecologically based natural resource management
system in which trees are integrated in farmland and rangeland is known
as agroforestry.
. Air: The atmosphere of Earth is a layer of gases surrounding the planet
Earth that is retained by Earth’s gravity is known as air.
. Airborne Disease: Any diseases which are caused by pathogenic
microbial agents and transmitted through the air is known as air borne
disease. Airborne diseases effect humans and get discharged through
coughing, sneezing, laughing or through close personal contact. These
pathogens ride on either dust particles or small respiratory droplets and
can stay suspended in air and or are capable of traveling distances on air
currents.
. Air Pollution: The introduction of chemicals, particulate matter or
biological materials that cause harm or discomfort to humans or other

living organisms or cause damage to the natural environment or built
environment into the atmosphere is known as air pollution.
. Allowance: An amount that is allowed or granted, for example,
something such as money given at regular intervals or for a specific
purpose is known as allowance.
. Alternative Energy: Energy derived from non-fossil-fuel sources or
energy sources other than the traditional forest product and commercial
energy items is known as alternative energy. They are tidal power, wind
power, solar power etc.
. Alternative Technology: Technologies which are more
environmentally friendly than the functionally equivalent technologies
dominant in current practice is known as alternative technology. It is
technology that has an alternative to resource-intensive and wasteful
industry, aims to utilize resources sparingly with minimum damage to the
environment at affordable cost and with a possible degree of control
over the processes.
. Ancillary Benefits: The ancillary or side effects of policies aimed
exclusively at Climate Change mitigation. Such policies have an impact
not only on greenhouse gas emissions but also on resource use
efficiency like reduction in emissions of local and regional air pollutants
associated with fossil-fuel use and on issues such as transportation,
agriculture, land-use practices, employment, and fuel security.
Sometimes these benefits are referred to as “ancillary impacts”. In some
cases the benefits may be negative.
. Annex B Countries/Parties: The countries included in Annex B to the
Kyoto Protocol that have agreed to a target for their greenhouse-gas
emissions, including all the Annex I countries (as amended in 1998)
except for Turkey and Belarus is known as Annex B countries or
Parties.
. Annex I Countries/Parties: Group of countries included in Annex I
(as amended in 1998) to the United Nations Framework Convention on
Climate Change, including all the developed countries in the
Organization for Economic Cooperation and Development and
economies in transition are known as Annex I countries or parties.

. Annex II Countries: Group of countries included in Annex II to the
United Nations Framework Convention on Climate Change, including
all developed countries in the Organization for Economic Cooperation
and Development is known as Annex II countries. Under Article 4.2(g)
of the Convention, these countries are expected to provide financial
resources to assist developing countries to comply with their
obligations, such as preparing national reports. Annex II countries are
also expected to promote the transfer of environmentally sound
technologies to developing countries.
. Anthropogenic: It is related to the influence of human beings or their
ancestors on natural objects. Anthropogenic carbon dioxide is that
portion of carbon dioxide in the atmosphere that is produced directly by
human activities such as the burning of fossil fuels rather than by such
processes as respiration and decay. Anthropogenic factors are human
activities that change the environment. In some cases the chain of
causality of human influence on the climate is direct and unambiguous
(for e.g. the effects of irrigation on local humidity); while in other
instances it is less clear.
. Anthropogenic Emissions: Emissions of greenhouse gases, greenhouse
gas precursors and aerosols associated with human activities is known
as anthropogenic emissions. These include burning of fossil fuels for
energy, deforestation, and land use changes that result in net increase in
emissions.
. Anthropogenic Source: A source of pollution caused or produced by
human activities, such as the use of consumer products or industrial
processes is known as anthropogenic source.
. Anticipatory Adaptation: Adaptation that takes place before an
impact of climate change is observed is known as anticipatory
adaptation.
. Appropriate Technology (AT): Technology that is designed with
special consideration to the environmental, ethical, cultural, social,
political, and economic aspects of the community it is intended for is
known as appropriate technology. With environmental and ethical goals
in mind, AT proponents claim their methods require fewer resources,
are easier to maintain and have less impacts on the environment

compared to techniques from mainstream technology which they
contend is wasteful and environmentally polluting.
. Assigned Amounts: Under the Kyoto Protocol, the total amount of
greenhouse gas emissions that each Annex B country has agreed that its
emissions will not exceed in the first commitment period (2008 to 2012)
is the assigned amount. This is calculated by multiplying the country’s
total greenhouse gas emissions in 1990 by five (for the percentage it
agreed to as listed in Annex B of the Kyoto Protocol (e.g. 92% for the
European Union and 93% for the USA).
. Atmosphere: The gaseous envelop surrounding the Earth is known as
atmosphere. The dry atmosphere consists almost entirely of nitrogen
(78.1% volume mixing ratio) and oxygen (20.9% volume mixing ratio),
together with a number of trace gases, such as argon (0.93% volume
mixing ratio), helium, and radiatively active greenhouse gases such as
carbon dioxide (0.035% volume mixing ratio) and ozone. In addition,
the atmosphere contains water vapor, whose amount is highly variable
but typically one percent volume mixing ratio. The atmosphere also
contains clouds and aerosols.
. Autonomous Adaptation: Adaptation that does not constitute a
conscious response to climatic stimuli but is triggered by ecological
changes in natural systems and by market or welfare changes in human
systems.
. Autumn: Autumn (Fall in American English) is one of the four temperate
seasons. Autumn marks the transition from summer into winter usually in
September (Northern Hemisphere) or March (Southern Hemisphere)
when the arrival of night becomes noticeably earlier.

B
. Bali Action Plan: Decision that was adopted by 1/CP.13 of the
COP-13 is known as Bali action plan. It also includes the Ad Hoc
Working Group on Further Commitments for Annex I Parties under the
Kyoto Protocol (AWG-KP) negotiations and their 2009 deadline, the
launch of the Adaptation Fund, the scope and content of the Article 9
review of the Kyoto Protocol, as well as decisions on technology
transfer and on reducing emissions from deforestation. The Conference
of Parties decided to launch a comprehensive process to enable the
implementation of the Convention through long-term cooperative
action, now, up to and beyond 2012.
. Belowground Biomass: All living biomass of live roots is known as
belowground biomass. Fine roots of less than ~2mm diameter are
sometimes excluded because these often cannot be distinguished
empirically from soil organic matter or litter.
. Bio-Carbon: The carbon sequestered and stored in the world’s trees,
plants, soils and oceans is known as bio-carbon. It is called
bio-carbon because it is carbon sequestered biologically. Bio-Carbon is
being rapidly released into the atmosphere through deforestation and
land degradation. Bio-Carbon is both a leading driver of anthropogenic
greenhouse gasses and one of the lowest-cost opportunities for
abatement.
. Bio-Carbon Fund: The Bio-Carbon Fund provides carbon finance for
projects that sequester or conserve greenhouse gases in forests,
agro- and other ecosystems. Through its focus on bio-carbon, or ‘sinks’,
it delivers carbon finance to many developing countries that otherwise
have few opportunities to participate in the Clean Development
Mechanism (CDM), or to countries with economies in transition through
Joint Implementation (JI). The Bio-Carbon Fund tests and demonstrates
how Land use, Land-use Change and Forestry (LULUCF) activities
can generate high-quality Ecological Resilience (ERs) with
environmental and livelihood benefits that can be measured, monitored
and certified and stand the test of time.
. Bioclimatology: The interdisciplinary field of science that studies the
interactions between the biosphere and the Earth’s atmosphere on time
scales of the order of seasons or longer is known as bioclimatology.

. Biodiversity: The numbers and relative abundances of different genes
(genetic diversity), species and ecosystems (communities) in a particular
area is known as biodiversity or the total diversity of all organisms and
ecosystems at various spatial scales (from genes to entire biomes).
. Bioenergy: The renewable energy derived from biological
sources/biomass to be used for heat, electricity or vehicle fuel is known
as bioenergy. Bio-fuel derived from plant materials is among the most
rapidly growing renewable energy technologies.
. Bio-engineering: The application of concepts and methods of physics,
chemistry and mathematics to solve problems in life sciences using
engineering’s own analytical and synthetic methodologies is known as
bio-engineering.
. Bio-fuel: A fuel produced from dry organic matter or combustible oil
produced by plants is known as bio-fuel. Examples of bio-fuel include
alcohol (from fermented sugar), black liquor from the paper
manufacturing process, wood and soybean oil.
. Biogas: A gas produced by the biological breakdown of organic
matter in the absence of oxygen is known as biogas. Biogas originates
from biogenic material and is a type of bio-fuel. This type of biogas
comprises primarily methane and carbon dioxide.
. Biogeochemical Cycle: Movements through the Earth system of key
chemical constituents essential to life, such as carbon, nitrogen, oxygen
and phosphorus is known as biogeochemical cycle.
. Biological Community: Community of plants, animals and other
organisms of particular area is known as biological community.
. Biological Hazard: Process or phenomenon of organic origin or
conveyed by biological vectors including exposure to pathogenic
micro-organisms, toxins and bioactive substances that may cause loss
of life, injury, illness or other health impacts, property damage, loss of
livelihoods and services, social and economic disruption or
environmental damage is known as biological hazard. Examples of
biological hazards include outbreaks of epidemic diseases, plant or
animal contagion, insect or other animal plagues and infestations.

. Biomass: The total mass of living organisms in a given area or volume;
recently dead plant material is often included as dead biomass.
. Biomass Energy: A renewable energy source derived from biological
material from living or recently living organisms such as wood, waste,
(hydrogen) gas, and alcohol fuels is known as biomass energy. Biomass
is commonly plant matter grown to generate electricity or produce heat.
In this sense, living biomass can also be included as plants that can also
generate electricity while still alive. The most conventional way in which
biomass is used, however, still relies on direct incineration.
. Biome: A major and distinct regional element of the biosphere, typically
consisting of several ecosystems (e.g. forests, rivers, ponds, swamps
within a region of similar climate) or a regional ecosystem with a distinct
assemblage of vegetation, animals, microbes, and physical environment
often reflecting a certain climate and soil is known as biome. Biomes are
characterized by typical communities of plants and animals.
. Biosphere: The part of the Earth system comprising all ecosystems and
living organisms in the atmosphere, on land (terrestrial biosphere) or in
the oceans (marine biosphere), including derived dead organic matter
such as litter, soil organic matter and oceanic detritus is known as
biosphere.
. Biostabilizer: A machine that converts solid waste into compost by
grinding and aeration is known as biostabilizer.
. Biota: All living organisms of an area; the flora and fauna considered as
a unit is known as biota.
. Black Carbon (BC): A climate forcing agent formed through the
incomplete combustion of fossil fuels, bio-fuel and biomass and is
emitted in both anthropogenic and naturally occurring soot is known as
black carbon. It has recently emerged as a major contributor to global
climate change, now attributed as the second largest contributor to
global warming. BC particles strongly absorb sunlight and give soot its
black color. It consists of pure carbon in several linked forms. Primary
sources include emissions from diesel engines, cook stoves, wood burning
and forest fires. Black carbon warms the Earth by absorbing heat in the
atmosphere and by reducing albedo, the ability to reflect sunlight, when

deposited on snow and ice. BC remains in the atmosphere for only a
few weeks.
. Blue Planet: A BBC nature documentary series narrated by David
Attenborough, first transmitted in the UK from 12 September 2001 is
known as blue planet.

C
. Canopy Area: Leaves which acts as an umbrella over the ground
surface is known as canopy area.
. Capacity: The combination of all the strengths, attributes and resources
available within a community, society or organization that can be used to
achieve agreed goals is known as capacity.
. Capacity Building: In the context of Climate Change, capacity
building is a process of developing the technical skills and institutional
capability in developing countries and economies in transition to enable
them to participate in all aspects of adaptation to, mitigation of, and
research on Climate Change and the implementation of the Kyoto
Mechanisms, etc.
. Capacity Development: The process by which people, organizations
and society systematically stimulate and develop their capacities over
time to achieve social and economic goals, including through
improvement of knowledge, skills, systems, and institutions is known as
capacity development or capacity development is a concept that
extends the term of capacity building to encompass all aspects of
creating and sustaining capacity growth over time. It does not involve
only learning and various types of training but also continuous efforts to
develop institutions, political awareness, financial resources, technology
systems and the wider social and cultural enabling environment.
. Carbon Accounting System: The accounting process undertaken to
measure the amount of carbon dioxide equivalents that will not be
released into the atmosphere as a result of Flexible Mechanisms projects
under the Kyoto Protocol is known as carbon accounting system. These
projects thus include (but are not limited to) renewable energy projects
and biomass, forage and tree plantations.
. Carbon (Dioxide) Capture and Storage (CCS): A process
consisting of separation of carbon dioxide from industrial and
energy-related sources, transport to a storage location and long-term
isolation from the atmosphere is known as carbon capture and storage.

. Carbon Cycle: The flow of carbon (in various forms, e.g. as carbon
dioxide) through the atmosphere, ocean, terrestrial biosphere and
lithosphere is known as carbon cycle.
. Carbon Dioxide (CO2): CO2 is a naturally occurring gas and a
by-product of burning fossil fuels or biomass, of land-use changes and
of industrial processes. It is the principal anthropogenic greenhouse gas
that affects Earth’s radiative balance. It is the reference gas against which
other greenhouse gases are measured and therefore it has a Global
Warming Potential of one.
. Carbon Finance: Carbon finance is a new branch of environmental
finance. Carbon finance explores the financial implications of living in a
carbon-constrained world, a world in which emissions of carbon
dioxide and other greenhouse gases (GHGs) carry a price. The general
term is applied to investments in GHG emission reduction projects and
the creation (origination) of financial instruments that are tradable on the
carbon market.
. Carbon Footprint: The total set of greenhouse gas emissions caused
by an organization, event or product is known as carbon footprint.
. Carbon Intensity: The amount of emission of carbon dioxide per unit
of Gross Domestic Product is known as carbon intensity.
. Carbon Leakage: The part of emissions reductions in Annex B
countries that may be offset by an increase of the emissions in the
non-constrained countries above their baseline levels is known as
carbon leakage. This can occur through (1) relocation of
energy-intensive production in non-constrained regions; (2) increased
consumption of fossil fuels in these regions through decline in the
international price of oil and gas triggered by lower demand for these
energies; and (3) changes in incomes (thus in energy demand) because
of better terms of trade.
. Carbon Market: A carbon market is a market (institution of exchange)
where carbon shares are traded (bought and sold). Carbon shares are
also known as pollution credits. Carbon market functions with a limit on
allowable level of emissions. Polluters who are under this set cap can
sell their excess emission rights to those concerns who have crossed this
cap.

. Carbon Monoxide (CO): Carbon monoxide also called carbonous
oxide, is a colorless, odorless and tasteless gas which is slightly lighter
than air. It is highly toxic to humans and animals in higher quantities
although it is also produced in normal animal metabolism in low
quantities and is thought to have some normal biological functions.
. Carbon Offset: A mechanism for individuals and businesses to
neutralize rather than actually reduce their greenhouse gas emissions by
purchasing the right to claim someone else’s reductions as their own is
known as carbon offset.
. Carbon Pools: A reservoir of carbon that has the potential to
accumulate (or lose) carbon over time is known as carbon pools. In
Agriculture Forestry and Other Land Use (AFOLU), this encompasses
aboveground biomass, belowground biomass, litter, dead wood and
soil organic carbon.
. Carbon Rights: A carbon right is a new and unique form of land
interest that confers upon the holder a right to the intangible benefit of
carbon sequestration on a piece of forested land.
. Carbon Sequestration: The process of removing carbon from the
atmosphere and depositing it in a reservoir is known as carbon
sequestration.
. Carbon Sink: A carbon pool that is increasing in size is known as
carbon sink. A carbon pool can be a sink for atmospheric carbon if
during a given time interval more carbon is flowing into it than out of it.
. Carbon Stock: The quantity of carbon held within a pool is known as
carbon stock. It is measured in metric tons of CO2.
. Carbon Substitution: The substitution of carbon intensive products
with harvested [sustainable] wood products or substitution of fossil fuel
with bio-fuels is known as carbon substitution.
. Carbonaceous Aerosol: Aerosol consisting predominantly of organic
substances and various forms of black carbon is known as
carbonaceous aerosol.

. Carrying Capacity: The carrying capacity of a biological species in an
environment is the population size of the species that the environment
can sustain indefinitely, given the food, habitat, water and other
necessities available in the environment.
. Catastrophic Event: A climate related event having sudden onset and
widely distributed and large magnitude impacts on human or natural
systems such as historically rapid sea level rise or sudden shifts (over a
decade or less) in atmospheric or oceanic circulation patterns is known
as catastrophic event. Such events have occurred in the past due to
natural causes.
. Catchment: An area that collects and drains rainwater is known as
catchment.
. Certified Emission Reductions (CERs): Certified Emission
Reductions (CERs) are a type of emissions unit (or carbon credits)
issued by the Clean Development Mechanism (CDM) Executive Board
for emission reductions achieved by CDM projects and verified by a
Department of Energy (DoE) under the rules of the Kyoto Protocol.
CERs are either long-term (lCER) or temporary (tCER), depending on
the likely duration of their benefit. Both types of CER can be purchased
from the primary market (purchased from original party that makes the
reduction) or secondary market (resold from a marketplace).
. Character: The peculiar quality or the sum of qualities by which a
person or a thing is distinguished from others; the stamp impressed by
nature, education or habit; that which a person or thing really is; nature;
and disposition is known as character.
. Chlorofluorocarbons: Greenhouse gases covered under the 1987
Montreal Protocol and used for refrigeration, air conditioning,
packaging, insulation, solvents, or aerosol propellants is known as
chlorofluorocarbons. Since they are not destroyed in the lower
atmosphere, CFCs drift into the upper atmosphere where given
suitable conditions they break down ozone. These gases are being
replaced by other compounds, including hydro chlorofluorocarbons and
hydrofluorocarbons, which are greenhouse gases covered under the
Kyoto Protocol.

. City Climate: Climate characteristic of the interior of a landmass of
continental size marked by large annual, daily and day-to-day
temperature ranges, low relative humidity and a moderate or small
irregular rainfall. Annual extremes of temperature that occur soon after
the solstices is known as city climate.
. Clean Development Mechanism: Defined in Article 12 of the Kyoto
Protocol, the Clean Development Mechanism is intended to meet two
objectives: (1) to assist Parties not included in Annex I in achieving
sustainable development and in contributing to the ultimate objective of
the convention; and (2) to assist Parties included in Annex I in achieving
compliance with their quantified emission limitation and reduction
commitments. Certified Emission Reduction Units from Clean
Development Mechanism projects undertaken in Non-Annex I
countries that limit or reduce greenhouse gas emissions, when certified
by operational entities designated by Conference of the Parties/Meeting
of the Parties can be accrued to the investor (government or industry)
from Parties in Annex B. A share of the proceeds from the certified
project. A mechanism under the Kyoto protocol through which
developed countries may finance greenhouse gas emission reduction or
removal projects in developing countries and receive credits for doing
so which they may apply towards meeting mandatory limits on their own
emissions is known as clean development mechanism.
. Climate: Climate is in a narrow sense is usually defined as the “average
weather” or more rigorously as the statistical description in terms of the
mean and variability of relevant quantities over a period of time ranging
from months to thousands or millions of years. The classical period is 30
years, as defined by the World Meteorological Organization (WMO).
These relevant quantities are most often surface variables such as
temperature, precipitation and wind. Climate in a wider sense is the
state including a statistical description of the climate system.
. Climate Change: It refers to a statistically significant variation in either
the mean state of the climate or in its variability, persisting for an
extended period (typically decades or longer). Climate Change may be
due to natural processes or external forcing or to persistent
anthropogenic changes in the composition of the atmosphere or in
land-use. This means a change of climate which is attributed directly or
indirectly to human activity that alters the composition of the global

atmosphere and which is in addition to natural climate variability
observed over comparable time periods. The UN Framework
Convention on Climate Change (UNFCCC) uses the term “Climate
Change” for human-caused change and “climate variability” for other
changes.
. Climate Change Adaptation: Adjustment in natural or human systems
in response to actual or expected climatic stimuli or their effects, which
moderates harm or exploits beneficial opportunities is known as Climate
Change Adaptation.
. Climate Change Adaptation Strategy: A general plan of action of any
country for addressing the impacts of Climate Change including climate
variability and extremes is known as Climate Change Adaptation
Strategy of a country. It may include a mix of policies and measures
selected to meet the overarching objective of reducing the country’s
vulnerability. Depending on the circumstances, the strategy can be
comprehensive at a national level, addressing adaptation across sectors,
regions and vulnerable populations or it can be more limited, focusing on
just one or two sectors or regions.
. Climate Change Impacts: The effect of Climate Change on natural
and human systems is known as Climate Change Impacts. Depending
on the consideration of adaptation, one can distinguish between
potential impacts and residual impacts
. Climate Change Impact Assessment: Impacts that affect
ecosystems or human welfare but that are not directly linked to market
transactions, for example, an increased risk of premature death. The
analysis of positive and negative consequences of Climate Changes on
natural systems and human societies, both with and without adaptation
to such changes is known as Climate Change Impact Assessment.
. Climate Change Mitigation: Strategies and policies that reduce the
concentration of greenhouse gases in the atmosphere either by
reducing their emissions or by increasing their capture is known as
Climate Change Mitigation.
. Climate Change Scenario: A coherent and internally-consistent
description of the change in climate by a certain time in the future using a

specific modeling technique and under specific assumptions about the
growth of greenhouse gas and other emissions and about other factors
that may influence climate in the future is known as Climate Change
Scenario. A “Climate Change Scenario” is the difference between a
climate scenario and the current climate. A plausible and often simplified
representation of the future climate based on an internally consistent set
of climatological relationships, that has been constructed for explicit use
in investigating the potential consequences of anthropogenic climate
change, often serving as input to impact models. Climate projections
often serve as the raw material for constructing climate scenarios but
climate scenarios usually require additional information such as about
the observed current climate.
. Climate Change Vulnerability Assessment: A range of tools that
exist to help communities understand the hazards that affect them and
take appropriate measures to minimize their potential impact is known
as Climate Change Vulnerability Assessment.
. Climate Hazard: The harmful effect of Climate Change on livelihoods
and ecosystems is known as climate hazard. They can be caused by
gradual climate variability or extreme weather events. Some hazards are
continuous phenomena that start slowly such as the increasing
unpredictability of temperatures and rainfall. Others are sudden but
relatively discrete events such as heat waves or floods.
. Climate Model: A numerical representation of the climate system based
on the physical, chemical and biological properties of its components,
their interactions and feedback processes and accounting for all or some
of its known properties is known as climate model. The climate system
can be represented by models of varying complexity - that is, for any
one component or combination of components a “hierarchy” of models
can be identified differing in such aspects as the number of spatial
dimensions, the extent to which physical, chemical or biological
processes are explicitly represented or the level at which empirical
parameterizations are involved. Coupled Atmosphere/Ocean/Sea-ice
General Circulation Models (AOGCMs) provide a comprehensive
representation of the climate system. There is an evolution towards more
complex models with active chemistry and biology. Climate models are
applied as search tool to study and simulate the climate but also for
operational purposes, including monthly, seasonal and inter-annual
climate predictions.

. Climate Prediction: A climate prediction or climate forecast is the
result of an attempt to produce a most likely description or estimate of
the actual evolution of the climate in the future (for e.g. at seasonal,
inter-annual or long-term time-scales).
. Climate Profile: An analysis (often in graphical form) representing
the extent to which something exhibits various characteristics, such as
biographical sketch is known as climate profile.
. Climate Projection: A projection of the response of the climate system
to emission or concentration scenarios of greenhouse gases and
aerosols, or radiative forcing scenarios, often based upon simulations
by climate models is known as climate projection. Climate projections
are distinguished from climate predictions; it depend upon the emission/
concentration/radiative forcing scenario used which are based on
assumptions concerning, for example, future socio-economic and
technological developments that may or may not be realized and are
therefore subject to substantial uncertainty.
. Climate Risk: The likelihood that the harmful effects will happen is
known as climate risk or it is a measure of the probability of harm to life,
property and the environment that would occur if a hazard took place.
Risk is estimated by combining the probability of events and the
consequences (usually seen as losses) that would arise if the events took
place. It denotes the result of the interaction of physically defined
hazards with the properties of the exposed systems i.e. their sensitivity
or social vulnerability. Risk can also be considered as the combination
of an event, its likelihood and its consequences i.e. risk equals the
probability of climate hazard multiplied by a given system’s vulnerability.
. Climate Sensitivity: A measure of how responsive the temperature of
the climate system is to a change in the radiative forcing is known as
climate sensitivity. It is usually expressed as the temperature change
associated with a doubling of the concentration of carbon dioxide in
Earth’s atmosphere.
. Climate Shift: An abrupt shift or jump in mean values signaling a change
in climate regime is known as climate shift. Most widely used in
conjunction with the 1976/1977 climate shift that seems tocorrespond
to a change in El Niño-Southern Oscillation behaviour.

. Climate System: The climate system is the highly complex system
consisting of five major components: the atmosphere, the hydrosphere,
the cryosphere, the land surface and the biosphere and the interactions
between them. The climate system evolves in time under the influence
of its own internal dynamics and because of external forcing such as
volcanic eruptions, solar variations and anthropogenic forcing such as
the changing composition of the atmosphere and land use change.
. Climate Trend: The general direction in which climate factors such as
average annual temperature or rainfall tend to move over time is known
as climate trend.
. Climate Variability: Variations in the mean state and other statistics
(such as standard deviations, the occurrence of extremes, etc.) of the
climate on all spatial and temporal scales beyond that of individual
weather events is known as climate variability.
. Climate Variation: Change in the statistical properties of the climate
system when considered over periods of decades or longer, regardless
of cause is known as climate variation.
. Climatology (Climate Science): The study of climate, scientifically
defined as weather conditions averaged over a period of time is known
as climatology.
. Cloud Albedo Effect or Twomey Effect: A radiative forcing induced
by an increase in anthropogenic aerosols which cause an initial increase
in droplet concentration and a decrease in droplet size for fixed liquid
water content leading to an increase of cloud albedo is known as cloud
albedo effect or “Twomey effect.”
. Cloud Lifetime Effect or Albrecht Effect: A radiative forcing
induced by an increase in anthropogenic aerosols which cause a
decrease in droplet size, reducing the precipitation efficiency, thereby
modifying the liquid water content, cloud thickness and cloud lifetime is
known as “cloud lifetime effect” or “Albrecht affect.”
. Coalition of Rainforest Nations: The Coalition for Rainforest
Nations (CfRN) is an organization established by forested tropical
countries to collaboratively reconcile forest stewardship with economic

development. The Rainforest Coalition aims to bring together both
developing and industrialized nations for the purpose of creating
community-driven, environmentally sustainable economic growth.
. Cold Waves: Weather phenomenon that is distinguished by a cooling
of the air is known as cold waves.
. Common Property Resources: It means real property owned by
“tenants in common,” who each have an “undivided interest” in the
entire property. Common Property also means lands owned by the
government for public (common) use like parks and national forests.
. Communicable Disease: A communicable disease is carried by
microorganisms and transmitted through people, animals, surfaces, foods
or air. Communicable diseases rely on fluid exchange, contaminated
substances or close contact to travel from an infected carrier to a healthy
individual.
. Community: In the context of vulnerability assessment, a community
can be defined as people living in one geographical area who are
exposed to common hazards due to their location. They may have
common experience in responding to hazards and disasters. However,
they may have different perceptions of and exposure to risk. Groups
within the locality will have a stake in risk reduction measures (either in
favour or against).
. Community Based Adaptation: Community based adaptation is one
where the explicit objective is to reduce vulnerability to climate change.
. Community Based Adaptation Planning: Community Based
Adaptation (CBA) can be viewed simply as an additional layer of
community based development activities, practices, research and
policies.
. Community Based Vulnerability Assessment: Community based
vulnerability assessments are policy and action oriented assessment done
in the community with the help of a range of community based
participatory tools with overall objective to mitigate the negative
impacts of disaster. It is done in full participation of the community.

. Community Development (CD): Community Development is a broad
term applied to the practices and academic disciplines of civic leaders,
activists, involved citizens and professionals to improve various aspects
of local communities. Community Development seeks to empower
individuals and groups of people by providing these groups with the
skills they need to affect change in their own communities. These skills
are often concentrated around building political power through the
formation of large social groups working for a common agenda.
. Community and/or Environmental Impacts: The effect that project
activities may have on the socio-economic or environmental landscape
is known as community or environmental impacts. The General
Approval Process of the Voluntary Carbon Standards (VCS) requires
that project activities which do not have any negative impacts and do
not provide perverse incentives for the clearing of land to generate
carbon credits.
. Conference of Parties: The supreme body of the United Nations
Framework Convention on Climate Change (UNFCCC), comprising
countries that have ratified or acceded to the UNFCCC is known as
conference of parties. The first session of the Conference of the Parties
(COP- 1) was held in Berlin, Germany in 1995, followed by COP-2 in
Geneva, Switzerland 1996, COP-3 in Kyoto, Japan 1997, COP-4
in Buenos Aires, Argentina 1998, COP-5 in Bonn, Germany 1999,
COP-6 Part 1 in The Hague, Netherland 2000, and COP-6 Part 2 in
Bonn, Germany 2001, COP-7 in Marrakech, Morocco 2001, COP-8
in New Delhi, India 2002, COP-9 in Milan, Italy 2003, COP-10 in
Buenos Aires, Argentina 2004, COP-11 in Montreal, Canada 2005,
COP-12 in Nairobi 2006, COP-13 in Bali, Indonesia 2007, COP-14
in Poznañ, Poland 2008, COP-15 in Copenhagen, Denmark 2009,
COP-16 in Cancún, Mexico 2010 and COP-17 to be held in Durban,
South Africa 2011.
. Conservation Area: A tract of land that has been awarded protected
status in order to ensure that natural features, cultural heritage or biota
are safeguarded is known as conservation area. A conservation area
may be a nature reserve, a park, a land reclamation project or other
area.

. Conservation of Natural Resources: The wise use of the earth’s
resources by humanity is known as conservation of natural resources.
The term conservation came into use in the late 19th century. It refers to
the management, mainly for economic reasons, of such valuable natural
resources as timber, fish, topsoil, pastureland and minerals and also to
the preservation of forests, wildlife, parkland, wilderness and watershed
areas. Conservation of natural resources is now usually embraced in the
broader conception of conserving the earth itself by protecting its
capacity for self-renewal.
. Contingency Planning: A management process that analyses specific
potential events or emerging situations that might threaten society or the
environment and establishes arrangements in advance to enable timely,
effective and appropriate responses to such events and situations is known
as contingency planning. Contingency planning results in organized and
coordinated courses of action with clearly identified institutional roles
and resources, information processes and operational arrangements
for specific actors at times of need. Based on scenarios of possible
emergency conditions or disaster events, it allows key actors to
envision, anticipate and solve problems that can arise during crises.
Contingency planning is an important part of overall preparedness.
Contingency plans need to be regularly updated and exercised.
. Convention: A large gathering of people who share a common interest
is known as convention.
. Convention of Biological Diversity (or biodiversity): Known
informally as the Biodiversity Convention, is an international legally binding
treaty. It is one of the three environmental conventions to arise from the
UN Earth Summit in Rio de Janeiro in 1992. Its objective is to develop
national strategies for the conservation and sustainable use of biological
diversity. It is often seen as the key document regarding sustainable
development. The agreement covers all ecosystems, species and
genetic resources. It links traditional conservation efforts to the
economic goal of using biological resources sustainably. It sets
principles for the fair and equitable sharing of the benefits arising from
the use of genetic resources, notably those destined for commercial use.
. Copenhagen Accord: The Copenhagen Accord is a document that
delegates at the session of the Conference of Parties (COP 15) to the

United Nations Framework Convention on Climate Change (UNFCC)
agreed to “take note of” at the final plenary on 18 December 2009.
The Accord, drafted by, on the one hand, the United States and on the
other, in a united position as the BASIC countries (China, India, South
Africa and Brazil), is not legally binding and does not commit countries
to agree to a binding successor to the Kyoto Protocol whose present
round ends in 2012.
. Coping: The use of existing resources to achieve desired goals during
and immediately after a climate-induced hazard is knows as coping.
. Coping Capacity: The ability of people, organizations and systems,
using available skills and resources to face and manage adverse
conditions, emergencies or disasters is known as coping capacity. The
capacity to cope requires continuing awareness, resources and good
management, both in normal times as well as during crises or adverse
conditions. Coping capacities contribute to the reduction of disaster risks.
. Coping Mechanism: Those means by which societies unassisted from
the outside meet relief and recovery needs and adjust to future disaster
risk is known as coping mechanism.
. Coping Range: The variation in climatic stimuli that a system can
absorb without producing significant impacts is known as coping range
or it is the range of climate where the outcomes are beneficial or
negative but tolerable. Beyond the coping range, the damages or loss
are no longer tolerable and a society (or a system) is said to be
vulnerable.
. Coping Strategies: Households develop short-term responses to
specific shocks known as coping strategies. These are ‘next best’
efforts to make do in a difficult situation with the hope that the household
can return to normal activities and their normal livelihoods strategy.
. Corrective Disaster Management: Management activities that
address and seek to correct or reduce disaster risks which are already
present is known as corrective disaster management.
. Cropland: Arable and tillage land, and agro-forestry systems where
vegetation falls below the threshold used for the forest land category is
known as cropland.

. Cultural Services: The benefits that ecosystem can provide such as
recreational, spiritual, religious and other non-material benefit is known
as “cultural services”.
. Customary Rights: Rights which are acquired by custom for local
usages, belonging to all the inhabitants of a particular place or district is
know as customary rights.

D
. Deadwood: Includes all non-living woody biomass not contained in the
litter, either standing, lying on the ground or in the soil is known as
deadwood. Deadwood includes wood lying on the surface, dead roots,
and stumps larger than or equal to 10 cm in diameter or any other
diameter used by the host country.
. Declaration: A non-binding political statement made by ministers
attending a major meeting (e.g. the Delhi Ministerial Declaration on
climate change and sustainable development at COP-8) is known as
declaration.
. Deforestation: Conversion of forest to non-forest is known as
deforestation.
. Degradation: Changes which negatively affect the structure or function
of the site and thereby lower the capacity to supply products and/or
services.
. Demography: Demography is the scientific study of characteristics and
dynamics pertaining to the human population. The characteristics
encompassed by this study include size, growth rate, density, vital
statistics and distribution of a specified population.
. Desertification: Land degradation in arid, semi-arid and dry
sub-humid areas resulting from various factors including climatic
variations and human activities is known as desertification. The
progressive destruction or degradation of vegetative cover, especially in
arid or semi-arid regions bordering existing deserts. Overgrazing of
rangelands, large-scale cutting of forests and woodlands, drought, burning
of extensive areas and climate changes all serve to destroy or degrade
the vegetation cover.
. Designated National Authority: A designated national authority
(DNA) is the body granted responsibility by a Party to authorize and
approve participation in Clean Development Mechanism (CDM)
projects. Establishment of a DNA is one of the requirements for
participation by a Party in the CDM. The main task of the DNA is to

assess potential CDM projects to determine whether they will assist the
host country in achieving its sustainable development goals and to
provide a letter of approval to project participants in CDM projects. An
office, ministry or other official entity appointed by a party to the Kyoto
protocol to review and give national approval to projects proposed
under the Clean Development Mechanism.
. Developing Countries: Developing country is a term generally used to
describe a nation with a low level of material well-being. These are
countries which in most cases have low standard of living.
. Development: A step or stage in growth, advancement etc. is known
as development. Development does not just involve the biological and
physical aspects of growth but also the cognitive and social aspects
associated with development throughout life. The United Nations
Development Programme uses a more detailed definition, according to
them development is ‘to lead long and healthy lives, to be
knowledgeable, to have access to the resources needed for a decent
standard of living and to be able to participate in the life of the
community.
. Disaster: A serious disruption of the functioning of a community or a
society causing widespread human, material, economic or
environmental losses which exceed the ability of the affected community
or society to cope using its own resources is known as disaster.
Disasters are often described as a result of the combination of: the
exposure to a hazard; the conditions of vulnerability that are present;
and insufficient capacity or measures to reduce or cope with the
potential negative consequences. Disaster impacts may include loss of
life, injury, disease and other negative effects on human physical, mental
and social well-being together with damage to property, destruction of
assets, loss of services, social and economic disruption and
environmental degradation.
. Disaster Risk: The potential disaster losses, in lives, health status,
livelihoods, assets and services which could occur to a particular
community or a society over some specified future time period is known
as disaster risk. The definition of disaster risk reflects the concept of
disasters as the outcome of continuously present conditions of risk.
Disaster risk comprises different types of potential losses which are

often difficult to quantify. Nevertheless, with knowledge of the prevailing
hazards and the patterns of population and socio-economic
development, disaster risks can be assessed and mapped in broad terms
at least.
. Disaster Risk Management: The systematic process of using
administrative directives, organizations, and operational skills and
capacities to implement strategies, policies and improved coping
capacities in order to lessen the adverse impacts of hazards and the
possibility of disaster is knows as disaster risk management. This term is
an extension of the more general term “risk management” to address the
specific issue of disaster risks. Disaster risk management aims to avoid,
lessen or transfer the adverse effects of hazards through activities and
measures for prevention, mitigation and preparedness.
. Disaster Risk Reduction: The concept and practice of reducing
disaster risks through systematic efforts to analyze and manage the causal
factors of disasters including through reduced exposure to hazards,
lessened vulnerability of people and property, wise management of land
and the environment and improved preparedness for adverse events is
known as disaster risk reduction.
. Disaster Risk Reduction Plans: A document prepared by an
authority, sector, organization or enterprise that sets out goals and
specific objectives for reducing disaster risks together with related
actions to accomplish these objectives. Disaster risk reduction plans
should be guided by the Hyogo Framework and considered and
coordinated within relevant development plans, resource allocations and
programme activities. National level plans needs to be specific to each
level of administrative responsibility and adapted to the different social
and geographical circumstances that are present. The time frame and
responsibilities for implementation and the sources of funding should be
specified in the plan. Linkages to Climate Change adaptation plans should
be made where possible.
. Disturbance Regime: Frequency, intensity, and types of disturbances
such as fires, insect or pest outbreaks, floods and drought is known as
disturbance regime.

. Diurnal Temperature Range: The difference between the maximum
and minimum temperature during a day is known as diurnal temperature
range.
. Dominant Species: The species that predominates in an ecological
community, particularly when they are most numerous or form the bulk
of the biomass is known as dominant species.
. Downscaling: Downscaling is a method that derives local-to-regionalscale
(10 to 100 km) information from larger-scale models or data
analyses. Two main methods are distinguished: dynamical downscaling
and empirical/statistical downscaling. In all cases, the quality of the
downscaled product depends on the quality of the driving model.
. Drivers of Deforestation and Forest Degradation: According to
REDD the drivers of deforestation and forest degradation are divided
into two as: National Drivers: military personnel, government officials,
economic land concessions and Sub-National Drivers: forest fires,
migrant encroachment, land speculation, agricultural expansion, illegal
logging and firewood consumption.
. Drought: The phenomenon that exists when precipitation has been
significantly below normal recorded levels causing serious hydrological
imbalances that adversely affect land resource production systems is
known as drought. A drought is an extended period of months or years
when a region notes a deficiency in its water supply. Generally, this
occurs when a region receives consistently below average precipitation.
It can have a substantial impact on the ecosystem and agriculture of the
affected region. Although droughts can persist for several years, even a
short intense drought can cause significant damage and harm the local
economy.
. Dynamical Downscaling: The method of downscaling which uses the
output of regional climate models, global models with variable spatial
resolution or high-resolution global models is known as dynamical
downscaling.

E
. Early Warning System: The set of capacities needed to generate and
disseminate timely and meaningful warning information to enable
individuals, communities, and organizations threatened by a hazard to
prepare and to act appropriately in sufficient time to reduce the
possibility of harm or loss is known as early warning system.
. Earth Summit: Conference held in Rio de Janeiro (June 3-14, 1992)
to reconcile worldwide economic development with environmental
protection is known as earth summit. It was the largest gathering of
world leaders in history with 117 heads of state and representatives of
countries.
. Eco Tax: An eco tax is designated for the purpose of influencing human
behavior (specifically economic behavior) to follow an ecologically
benign path.
. Ecological Community: A group of actually or potentially interacting
species living in the same place is known as ecological community. A
community is bound together by the network of influences that species
have on one another.
. Ecological Footprint: A measure of human demand on the ecosystem
is known as ecological footprint. It compares human consumption of
natural resources with the planet’s ecological capacity to regenerate them.
. Ecological Resilience: The ability of a system to absorb impacts
before a threshold is reached where the system changes into a different
state is known as ecological resilience.
. Ecosystem: Dynamic complexes of plant, animal and microorganism
communities and the non-living environment interacting as functional units
or a community of all plants and animals and their physical environment
functioning together as an interdependent unit is known as ecosystem.
. Ecosystem Approach: A strategy for the integrated management of
land, water, and living resources that promotes conservation and
sustainable use is known as ecosystem approach. An ecosystem
approach is based on the application of appropriate scientific methods

focused on levels of biological organization, which encompass the
essential structure, processes, functions and interactions among
organisms and their environment. It recognizes that humans with their
cultural diversity are an integral component of many ecosystems.
. Ecosystem Based Adaptation: It includes a range of local and
landscape scale strategies for managing ecosystems to increase
resilience and maintain essential ecosystem services and reduce the
vulnerability of people, their livelihoods and nature in the face of climate
change. It also identifies and implements a range of strategies for the
management, conservation and restoration of ecosystems to ensure that
they continue to provide the services that enable people to adapt to the
impacts of Climate Change. It involves collective action among
governments, communities, conservation and development organizations,
and other stakeholders to plan and empower local action that will
increase environmental and community resilience to the changing
climate. Ecosystem based adaptation and community based adaptation
are therefore mutually supportive.
. Ecosystem Services: Ecological processes or a function that have value
to individuals or society or the benefits people obtain from ecosystems
is known as ecosystem services. The concept ‘ecosystem goods and
services’ is synonymous with ecosystem services. Integrated
management of land, water and living resources that promotes
conservation and sustainable use provide the basis for maintaining
ecosystem services, including those that contribute to reduced disaster
risks.
. Effect: The first event A (the cause) is a reason that brings about the
second event B (the effect) is known as effect.
. Effective Climate Sensitivity: It is a measure of the strengths of the
feedbacks at a particular time and may vary with forcing history and
climate state. It is evaluated from model output for evolving
non-equilibrium conditions.
. Embodied Energy: The energy used to produce a material substance
(such as processed metals or building materials) taking into account
energy used at the manufacturing facility (zero order) and energy used in
producing the materials that are used in the manufacturing facility (first
order) and so on is known as embodied energy.

. Emergency Management: The organization and management of
resources and responsibilities for addressing all aspects of emergencies,
in particular preparedness, response and rehabilitation is known as
emergency management.
. Emergency Services: The set of specialized agencies that have
specific responsibilities and objectives in serving and protecting people
and property in emergency situations is known as emergency services.
. Emissions: In the climate change context, emissions refer to the release
of greenhouse gases and/or their precursors and aerosols into the
atmosphere over a specified area and period of time.
. Emission Factor: The relationship between the amount of pollution
produced and the amount of raw material processed is known as
emission factor. For example, an emission factor for a blast frame
making iron would be the number of pounds of particulates per ton of
raw materials.
. Emission Inventory: A listing by source of the amount of air pollutant
discharge into the atmosphere of a community is known as emission
inventory. It is used to establish emission standards.
. Emission Standard: A level of emission that by law or by voluntary
agreement may not be exceeded is known as emission standard. Many
standards use emission factors in their prescription and therefore do not
impose absolute limits on the emissions.
. Emissions Permit: The non-transferable or tradable allocation of
entitlements by an administrative authority (intergovernmental
organization, central or local government agency) to a regional (country,
sub-national) or a sectoral (an individual firm) entity to emit a specified
amount of a substance is known as emissions permit.
. Emissions Quota: The portion or share of total allowable emissions
assigned to a country or group of countries within a framework of
maximum total emissions and mandatory allocations of resources is
known as emissions quota.

. Emissions Reduction Unit: Equal to one tonne (metric ton) of
carbon dioxide emissions reduced or sequestered arising from a Joint
Implementation (defined in Article 6 of the Kyoto Protocol) project
calculated by using Global Warming Potential is known as emissions
reduction unit.
. Emissions Scenario: A plausible representation of the future
development of emissions of substances that are potentially radiatively
active (e.g. greenhouse gases and aerosols), based on a coherent and
internally consistent set of assumptions about driving forces (such as
demographic and socio-economic development, technological change)
and their key relationships. Concentration scenarios derived from
emissions scenarios are used as input into a climate model to compute
climate projections. In IPCC (1992), a set of emissions scenarios were
used as a basis for the climate projections in IPCC (1996). These
emissions scenarios are referred to as the IS92 scenarios.
. Emissions Tax: Levy imposed by a government on each unit of CO2
equivalent emissions by a source subject to the tax is known as
emissions tax. Since virtually all of the carbon in fossil fuels is ultimately
emitted as carbon dioxide, a levy on the carbon content of fossil fuels a
carbon tax is equivalent to an emissions tax for emissions caused by
fossil-fuel combustion.
. Emissions Trading: One of the three Kyoto mechanisms, by which an
Annex I party may transfer Kyoto Protocol units to or acquire units
from another Annex I party is known as emissions trading. A
market-based approach to achieving environmental objectives that
allows, those reducing greenhouse gas emissions below what is required,
to use or trade the excess reductions to offset emissions at another source
inside or outside the country. In general, trading can occur at the
intra-company, domestic, and international levels. An emission trading
under Article 17 of the Kyoto Protocol is a tradable quota system based
on the assigned amounts calculated from the emission reduction and
limitation commitments listed in Annex B of the Protocol.
. Empirical /Statistical Downscaling: The methods of downscaling
which develop statistical relationships that link the large-scale atmospheric
variables with local/regional climate variables is known as
empirical/statistical downscaling.

. Endangered: Species whose population is so small that it is in danger
of becoming extinct is known as endangered.
. Endemic: It is restricted or peculiar to a locality or region. With regard
to human health, endemic can refer to a disease or agent present or
usually prevalent in a population or geographical area at all times.
. Energy: The amount of work or heat delivered is known as energy.
Energy is classified in a variety of types and becomes useful to human
ends when it flows from one place to another or is converted from one
type into another.
. Energy Efficiency: Ratio of energy output of a conversion process or
of a system to its energy input is known as energy efficiency.
. Energy Service: The application of useful energy to tasks desired by
the consumer such as transportation, a warm room or light is known as
energy services.
. Energy Tax: An energy tax is a levy on the energy content of fuels
reduces demand for energy and so reduces carbon dioxide emissions
from fossil fuel use.
. Energy Transformation: The change from one form of energy, such as
the energy embodied in fossil fuels to electricity is known as energy
transformation.
. Engineering Resilience: The capacity of a system to return to its
pre-disturbance state is known as engineering resilience.
. Ensemble: A group of parallel model simulations used for climate
projections is known as ensemble. Variation of the results across the
ensemble members gives an estimate of uncertainty. Ensembles made
with the same model but different initial conditions only characterize the
uncertainty associated with internal climate variability.
. Environment: It encompasses all living and non-living things occurring
naturally on Earth or some region thereof.

. Environment Impact Auditing: Environmental audit is the assessment
of the compliance of environmental administration and performance of
an operating business with environmental protection requirements, with
sound environmental practice in general, and with the principles of
sustainable development. Environmental auditing is mandatory only in
cases stipulated by law.
. Environment Impact Monitoring: Environmental impact monitoring
is the systematic observation of the state of the environment and of the
factors influencing it. Its main purposes are to forecast changes to the
state of the environment and to provide initial data for planning
documents, programmes and projects. The procedure of environmental
monitoring shall be established by law.
. Environmental Audit: An independent assessment of the current state
of a party’s compliance with applicable environmental requirements is
known as environmental audit.
. Environmental Degradation: The reduction of the capacity of the
environment to meet social and ecological objectives and needs is known
as environmental degradation. Degradation of the environment can alter
the frequency and intensity of natural hazards and increase the
vulnerability of communities. The types of human-induced degradation
are varied and include land misuse, soil erosion and loss, desertification,
wild land fires, loss of biodiversity, deforestation, mangrove destruction,
land, water and air pollution, climate change, sea level rise and ozone
depletion.
. Environmental Impact Assessment: Process by which the
environmental consequences of a proposed project or programme are
evaluated is known as environmental impact assessment. It is
undertaken as an integral part of planning and decision making
processes with a view to limiting or reducing the adverse impacts of the
project or programme. Environmental impact assessment is a policy tool
that provides evidence and analysis of environmental impacts of
activities from conception to decision-making. It is utilized extensively in
national programming and project approval processes and for
international development assistance projects. Environmental impact
assessments should include detailed risk assessments and provide
alternatives, solutions or options to deal with identified problems.

. Environmental Refugee: These are people forced to migrate away
from their homeland due to sudden or long-term changes to their local
environment. When the migration is considered to be forced and not a
matter of choice, additionally, if the causes for the migration are believed
to be due to global warming related environmental disasters, the term
climate refugee is sometimes used.
. Environmentally Sound Technologies: Technologies that protect the
environment are less polluting, use all resources in a more sustainable
manner, recycle more of their wastes and products, and handle residual
wastes in a more acceptable manner than the technologies for which
they were substitutes and are compatible with nationally determined
socio-economic, cultural and environmental priorities is known as
environmentally sound technologies.
. Epidemic: Occurring suddenly in numbers clearly in excess of normal
expectancy for example infectious diseases. It is also applied to any
disease, injury or other health-related event occurring in such outbreaks
is known as epidemic.
. Equilibrium Climate Experiment: An “equilibrium climate experiment”
is an experiment in which a climate model is allowed to fully adjust to a
change in radiative forcing. Such experiments provide information on
the difference between the initial and final states of the model, but not on
the time dependent response.
. Equilibrium Climate Sensitivity: Equilibrium climate sensitivity refers
to the equilibrium change in global mean surface temperature following a
doubling of the atmospheric (equivalent) CO2 concentration. More
generally, equilibrium climate sensitivity refers to the equilibrium change
in surface air temperature following a unit change in radiative forcing
(°C/Wm -2 ). In practice, the evaluation of the equilibrium climate
sensitivity requires very long simulations with coupled general circulation
models.
. Equilibrium line: The level on a glacier where the net balance equals
zero and accumulation equals ablation, the point at which expansion of
the glacier by accumulation is outstripped by losses of ice through
ablation is known as equilibrium line. Snow does not remain below the
equilibrium line throughout the warmer season.

. Erosion: The process of removal and transport of soil and rock by
weathering, mass wasting by the action of streams, glaciers, waves, winds
and underground water is known as erosion.
. Ethnic group: An ethnic group (or ethnicity) is a group of people whose
members identify with each other through a common heritage, often
consisting of a common language, a common culture (often including a
shared religion) and an ideology that stresses common ancestry or
endogamy.
. Eustatic Sea Level Rise: Change in global average sea level brought
about by an alteration to the volume of the world ocean is known as
eustatic sea level rise.
. Eutrophication: The process by which a body of water (often shallow)
becomes (either naturally or by pollution) rich in dissolved nutrients with
a seasonal deficiency in dissolved oxygen is known as eutrophication.
. Evaporation: The process by which a liquid becomes a gas is known
as evaporation.
. Evapotransportation: The combined process of evaporation from the
Earth’s surface and transpiration from vegetation is known as
evapotransportation.
. Exhaust Emission: Exhaust gas or flue gas is emitted as a result of the
combustion of fuels such as natural gas, gasoline/petrol, diesel fuel, fuel
oil or coal is known as exhaust emission. It is discharged into the
atmosphere through an exhaust pipe, flue gas stack or propelling nozzle.
. Expert Group on Technology Transfer (EGTT): An expert group
established at COP-7 with the objective of enhancing the
implementation of Article 4.5 of the Convention by analyzing and
identifying ways to facilitate and advance technology transfer activities
under the convention.
. Exposure: The degree of climate stress upon a particular unit analysis is
known as exposure. It may be represented as either long-term change in
climate conditions or by changes in climate variability including the
magnitude and frequency of extreme events or people, property,
systems or other elements present in hazard zones that are thereby

subject to potential losses or the nature and degree to which a system is
exposed to significant climatic variations is known as exposure.
Measures of exposure can include the number of people or types of
assets in an area.
. Extensive Risk: The widespread risk associated with the exposure of
dispersed populations to repeated or persistent hazard conditions of
low or moderate intensity, often of a highly localized nature, which can
lead to debilitating cumulative disaster impacts is known as extensive
risk. Extensive risk is mainly a characteristic of rural areas and urban
margins where communities are exposed to, and vulnerable to, recurring
localized floods, landslides storms or droughts. Extensive risk is often
associated with poverty, urbanization and environmental degradation.
. External Climate Variability: Variability may result from natural or
anthropogenic external forcing within the climate system is called
external climate variability.
. Externalities: Externalities occur when the activity of one person has
an inadvertent impact on the well-being of another person. Many
aspects of environmental degradation such as air pollution, global
warming, loss of wilderness and contamination of water bodies are viewed
as externalities of economic transactions.
. Extinction: The complete disappearance of an entire species is known
as extinction.
. Extirpation: The disappearance of a species from part of its range;
local extinction is known as extirpation.
. Extreme Weather Event: Meteorological conditions that are rare for
a particular place and/or time, such as an intense storm or heat wave is
known as extreme weather event. An extreme climate event is an
unusual average over time of a number of weather events, for example
heavy rainfall over a season. Definitions of rare vary, but an extreme
weather event would normally be as rare as or rarer than the 10th or 90th
percentile of the observed probability density function. By
definition, the characteristics of what is called extreme weather may vary
from place to place in an absolute sense. Single extreme events cannot
be simply and directly attributed to anthropogenic climate change, as

there is always a finite chance the event in question might have occurred
naturally. When a pattern of extreme weather persists for some time,
such as a season, it may be classed as an extreme climate event,
especially if it yields an average or total that is itself extreme (e.g. drought
or heavy rainfall over a season).

F
. Fallow: A period during the year when the land is kept bare and no crop
is raised on it is known as fallow.
. Financial Additionality: If the project activity funding will be
additional to existing Global Environmental Facility, other financial
commitments of Parties included in Annex I, Official Development
Assistance, and other systems of cooperation then it is known as
financial additionality.
. Financial Capital: The financial resource which are available to people
(whether savings, supplies of credit or regular remittances or pensions)
and which provide them with different livelihood options is known as
financial capital. Financial capital generally refers to saved-up
financial wealth especially that used to start or maintain a business.
. Financial Mechanism: Developed country Parties (Annex II Parties)
are required to provide financial resources to assist developing country
parties implement the convention. To facilitate this, the convention
established a financial mechanism to provide funds to developing
country parties. The parties to the convention assigned operation of the
financial mechanism to the Global Environment Facility (GEF) on an
on- going basis, subject to review every four years. The financial
mechanism is accountable to the COP.
. Flood: A flood is an overflow of an expanse of water that submerges
land. Flooding may result from the volume of water within a body of
water, such as a river or lake, which overflows or breaks levees with the
result that some of the water escapes its usual boundaries.
. Fog: Fog is a collection of water droplets or ice crystals suspended in
the air at or near the Earth’s surface. While fog is a type of a cloud, the
term “fog” is typically distinguished from the more generic term “cloud”
in that fog is low-lying and the moisture in the fog is often generated
locally (such as from a nearby body of water, like a lake or the ocean or
from nearby moist ground or marshes).
. Food Insecurity: A situation that exists when people lack secure
access to sufficient amounts of safe and nutritious food for normal growth

and development and an active and healthy life is known as food
insecurity. It may be caused by the unavailability of food, insufficient
purchasing power, inappropriate distribution, or inadequate use of food
at the household level. Food insecurity may be chronic, seasonal or
transitory.
. Food Security: It’s availability of food and one’s access to it. A
household is considered food-secure when its occupants do not live in
hunger or fear of starvation. “Food security exists when all the people,
at all times, have physical and economic access to sufficient, safe and
nutritious food to meet their dieatary and food preferences for an active
and healthy life.” (World Food Simmit 1996).
. Food Sufficiency: Food sufficiency is the ability to produce enough
food to support a population.
. Forecast: Definite statement or statistical estimate of the likely
occurrence of a future event or conditions for a specific area.
. Forest Carbon Partnership Facility: The Forest Carbon Partnership
Facility (FCPF) which became operational in June 2008, is a global
partnership focused on reducing emissions from deforestation and
forest degradation, forest carbon stock conservation, sustainable
management of forests and enhancement of forest carbon stocks
(REDD+).
. Forest Degradation: Changes within the forest which negatively
affects the structure or functions of the stand or site, and thereby lowers
the capacity to supply products and/or services is known as forest
degradation. Deforestation defined broadly can include not only
conversion to non-forest but also degradation that reduces forest
quality, the density and structure of the trees, the ecological services
supplied, the biomass of plants and animals, the species diversity and
the genetic diversity.
. Forest Dweller: Someone who subsists in a forest environment is known
as forest dweller.
. Forest Governance: Forest Governance is the act of governing the
forest. It relates to decisions that define expectations, grant power or

verify performance. It consists of either a separate process or part of
management or leadership processes. These processes and systems are
typically administered by a government.
. Forest Investment Program: The Forest Investment Program (FIP)
is a targeted program of the Strategic Climate Fund (SCF), which is one
of two funds within the framework of the Climate Investment Funds
(CIF). The FIP supports developing countries’ efforts to reduce
deforestation and forest degradation (REDD) and promotes sustainable
forest management that leads to emission reductions and the protection
of carbon reservoirs.
. Forest Management: Forest management is the branch of forestry
concerned with the overall administrative, economic, legal and social
aspects and with the essentially scientific and technical aspects,
especially silviculture, protection and forest regulation.
. Forest State: Most commonly considered in terms of the dominant
assemblage of tree species forming an ecosystem at a location, the
functional roles those species play and the characteristic vegetation
structures (height, layers, stems density, etc.) at maturity is known as
forest state.
. Forest Transition: Forest transition refers to a geographic theory
describing a reversal or turnaround in land-use trends for a given
territory from a period of net forest area loss (i.e. deforestation) to a
period of net forest area gain.
. Fossil Fuels: Carbon-based fuels from fossil carbon deposits including
coal, oil and natural gas is known as fossil fuel.
. Frost: Frost is the solid deposition of water vapor from saturated air. It
is formed when solid surfaces are cooled to below the dew point of the
adjacent air as well as below the freezing point of water.
. Functional Groups: Assemblages of species performing similar
functional roles within an ecosystem, such as pollination, production or
decomposition (i.e. trophic groups), hence providing some redundancy
is known as functional groups.

. Fund Mechanism: Method or source through which funding is made
available such as bank loans, bond or share issue, reserves or savings,
sales revenue is known as fund mechanism.
. Fundamental Niche: A geographic area with the appropriate set of
abiotic factors in which a species could occur is known as fundamental
niche.
. Fungibility Emission: Interchangeability, such as the flexibility
mechanisms for reducing greenhouse gas emissions that were agreed
under the Kyoto Protocol.

G
. Genetic Diversity: Genetic diversity refers to the total number of
genetic characteristics in the genetic makeup of a species or any
variation in the nucleotides, genes, chromosomes, or whole genomes of
organisms is known as genetic diversity. It is distinguished from genetic
variability which describes the tendency of genetic characteristics to vary.
Genetic diversity serves as a way for populations to adapt to changing
environments.
. Geo-Engineering: Efforts to stabilize the climate system by directly
managing the energy balance of the Earth thereby overcoming the
enhanced greenhouse effect is known as geo-engineering.
. Geographic Information System (GIS): A computer-based system
designed to collect, store, manage and analyze spatially referenced
information and associated attribute data is known as Geographic
Information System.
. Geological Hazard: Geological process or phenomenon that may cause
loss of life, injury or other health impacts, property damage, loss of
livelihoods and services, social and economic disruption or
environmental damage is known as geological hazard. Geological
hazards include internal earth processes, such as earthquakes, volcanic
activity and emissions, and related geophysical processes such as mass
movements, landslides, rockslides, surface collapses and debris or mud
flows. Hydro meteorological factors are important contributors to some
of these processes.
. Glacial Lake: A lake formed by glacier melt water located either at the
front of a glacier (known as a pro-glacial lake), on the surface of a
glacier (supra-glacial lake), within the glacier (englacial lake) or at the
glacier bed (sub-glacial lake) is known as glacial lake.
. Glacial Lake Outburst: A glacial lake outburst flood is created when
water dammed by a glacier or a moraine is released.
. Glacier: A mass of land ice flowing downhill (by internal deformation
and sliding at the base) and is constrained by the internal stress and
friction at the base and sides, surrounding topography (e.g. the sides of

a valley or surrounding peaks) is known as glacier. The bedrock
topography is the major influence on the dynamics and surface slope of
a glacier. A glacier is maintained by accumulation of snow at high
altitudes, balanced by melting at low altitudes or discharge into the sea.
. Global Environment Facility: The Global Environment Facility (GEF)
unites 182 member governments in partnership with international
institutions, nongovernmental organizations, and the private sector to
address global environmental issues. As an independent financial
organization, the GEF provides grants to developing countries and
countries with economies in transition for projects related to biodiversity,
climate change, international waters, land degradation, the ozone layer,
and persistent organic pollutants. These projects benefit the global
environment, linking local, national, and global environmental challenges
and promoting sustainable livelihoods.
. Global Surface Temperature: The global surface temperature is the
area weighted global average of (i) the sea surface temperature over the
oceans (i.e. the sub-surface bulk temperature in the first few meters of
the ocean) and (ii) the surface air temperature over land at 1.5 m above
the ground. The global surface temperature is an estimate of the global
mean surface air temperature. However, for changes over time only
anomalies as departures from climatology are used. Most commonly
based on the area weighted global average of the sea surface
temperature anomaly and land surface air temperature anomaly.
. Global Warming: The gradual increase observed or projected in
global surface temperature as one of the consequences of radioactive
forcing caused by anthropogenic emissions is known as global warming.
. Global Warming Potential: An index, describing the radiative
characteristics of well-mixed greenhouse gases that represents the
combined effect of the differing times these gases remain in the
atmosphere and their relative effectiveness in absorbing outgoing
infrared radiation is known as global warming potential. This index
approximates the time-integrated warming effect of a unit mass of a
given greenhouse gas in today’s atmosphere, relative to that of carbon
dioxide.

. Globalization: The growing integration and interdependence of
countries worldwide through the increasing volume and variety of cross
border transactions in goods and services, free international capital flows
and the more rapid and widespread diffusion of technology, information
and culture.
. Grass Land: Grasslands (also called greenswards) are areas where
the vegetation is dominated by grasses (Poaceae) and other herbaceous
(non-woody) plants.
. Greenhouse Effect: Greenhouse gases effectively absorb thermal
infrared radiation, emitted by the Earth’s surface, by the atmosphere
itself due to the same gases, and by clouds. Atmospheric radiation is
emitted to all sides, including downward to the Earth’s surface. Thus,
greenhouse gases trap heat within the surface-troposphere system. This
is called the greenhouse effect. Thermal infrared radiation in the
troposphere is strongly coupled to the temperature of the atmosphere at
the altitude at which it is emitted. In the troposphere, the temperature
generally decreases with height. Effectively, infrared radiation emitted to
space originates from an altitude with a temperature of on average,
–190C, in balance with the net incoming solar radiation, whereas the
Earth’s surface is kept at a much higher temperature of on average,
+140C. An increase in the concentration of greenhouse gases leads to
an increased infrared opacity of the atmosphere, and therefore to an
effective radiation into space from a higher altitude at a lower
temperature. This causes a radioactive forcing that leads to an
enhancement of the greenhouse effect, the so-called enhanced
greenhouse effect.
. Greenhouse Gases: The atmospheric gases responsible for causing
global warming and climate change. The major GHGs are carbon
dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Less
prevalent but very powerful greenhouse gases are hydroflurocarbons
(HFCs), periflurocarbons (PFCs) and sulphur hexafluoride (SF6).
. Gross Primary Production: The amount of carbon fixed from the
atmosphere through photosynthesis is known as gross primary
production.

. Group of 77 (G-77) and China: A large negotiating alliance of
developing countries that focuses on numerous international topics,
including climate change. The G-77 was founded in 1967 under the
auspices of the United Nations Conference on Trade and Development
(UNCTAD). It seeks to harmonize the negotiating positions of its 131
member states.

H
. Habit: An acquired pattern of behavior that often occurs automatically
is known as habit.
. Habitat: The particular environment or place where an organism or
species tend to live; a more locally circumscribed portion of the total
environment is known as habitat.
. Hail: Hail is a form of solid precipitation which consists of balls or
irregular lumps of ice, that are individually called hail stones. Hail stones
on Earth consist mostly of water ice and measure between 5 millimetres
(0.20 inch) and 150 millimetres (5.9 inch) in diameter, with the larger
stones coming from severe thunderstorms.
. Halocarbons: Halocarbon compounds are chemicals in which one or
more carbon atoms are linked by covalent bonds with one or
more halogen atoms (fluorine, chlorine,bromine or iodine) resulting in
the formation of organofluorine compounds, organochlorine
compounds, organobromine compounds, and organoiodine compounds.
Chlorine halocarbons are the most common and are
called organochlorides. Halocarbons are typically nonflammable and
nonreactive though some halocarbons are broken down by ultraviolet
radiation in the upper atmosphere and this process releases free halogen
atoms that damage the ozone layer. Some halocarbons have also been
implicated as greenhouse gases.
. Hazard: A dangerous phenomenon, substance, human activity or
condition that may cause loss of life, injury or other health impacts,
property damage, loss of livelihoods and services, social and economic
disruption, or environmental damage is known as hazard. The hazards
of concern to disaster risk reduction as stated in footnote 3 of the Hyogo
Framework are “… hazards of natural origin and related environmental
and technological hazards and risks.” Such hazards arise from a variety
of geological, meteorological, hydrological, oceanic, biological and
technological sources, sometimes acting in combination. In technical
settings, hazards are described quantitatively by the likely frequency of
occurrence of different intensities for different areas as determined from
historical data or scientific analysis.

. Hazard Based Approach: One of several conceptual and analytical
approaches to adaptation projects, this approach places its starting
emphasis on the biophysical aspects of climate - related risk - that is the
climate hazard.
. Hazard Mapping: The process of establishing hazard geographically
where certain phenomena are likely to pose a threat to human
settlements is known as hazard mapping. Hazard maps identify areas
that are subject to natural phenomena, such as earthquakes, hurricanes
and tornadoes and areas that could be threatened by manmade
disasters. For example, areas surrounding nuclear power plants,
chemical disposal sites or areas (such as refineries) subject to threat
from explosion or fire.
. Heritage Site: A UNESCO World Heritage Site is a place (such as a
forest, mountain, lake, desert, monument, building, complex or city) that
is listed by the UNESCO as of special cultural or physical significance.
. Hot Air/ Paper Credit: Hot Air refers to the concern that some
governments will be able to meet their targets for greenhouse-gas
emissions under the Kyoto Protocol with minimal effort and could then
flood the market with emissions credits, reducing the incentive for other
countries to cut their own domestic emissions. Paper credit founded
upon evidences of debt, such as promissory notes, due bills, etc.
. Hot waves: A heat wave is a prolonged period of excessively hot weather
which may be accompanied by high humidity.
. Human Capital: The skill, knowledge, ability to labour and good health
important to the ability to pursue different livelihood strategies is known
as human capital.
. Human Development: Human Development is a development
paradigm that is about much more than the rise or fall of national
incomes. It is about creating an environment in which people can
develop their full potential and lead productive, creative lives in accord
with their needs and interests.
. Humidity: The amount of water vapor in the air is known as humidity.

. Hybrid: It is used here to refer to approaches that apply uniform and
site-specific methods in tandem and within an iterative process to
develop and assess the range of adaptation strategies.
. Hydro Meteorological Hazard: Process or phenomenon of
atmospheric, hydrological or oceanographic nature that may cause loss
of life, injury or other health impacts, property damage, loss of
livelihoods and services, social and economic disruption or
environmental damage is known as hydro meteorological hazard.
. Hydrofluorocarbons (HFC5): Among the six greenhouse gases to be
curbed under the Kyoto Protocol. They are produced commercially as
a substitute for chlorofluorocarbons. HFCs largely are used in
refrigeration and semiconductor manufacturing. Their Global Warming
Potentials range from 1,300 to 11,700.
. Hydrological Cycle: The process of evaporation, vertical and
horizontal transport of vapor, condensation, precipitation, and the flow
of water from continents to oceans is known as hydrological cycle. It is
a major factor in determining climate through its influence on surface
vegetation, the clouds, snow and ice, and soil moisture. The hydrologic
cycle is responsible for 25 to 30 per cent of the mid-latitudes’ heat
transport from the equatorial to polar regions.

I
. ILO Convention 169: ILO Convention 169 is a legally binding
international instrument open to ratification, which deals specifically with
the rights of indigenous and tribal peoples. It is adopted in 1989. Today,
it has been ratified by 20 countries. Once it ratifies the Convention, a
country has one year to align legislation, policies and programmes to the
Convention before it becomes legally binding. Countries that have
ratified the Convention are subject to supervision with regards to its
implementation. The Convention applies to (a) “tribal peoples in
independent countries whose social, cultural and economic conditions
distinguish them from other sections of the national community, and whose
status is regulated wholly or partially by their own customs and
traditions or by special laws and regulations”; and (b) “peoples in
independent countries who are regarded as indigenous on account of
their descent from the populations which inhabited the country at the
time of the conquest or colonization or the establishment of the present
state boundaries and who, irrespective of their legal status, retain some
or all of their won social, economic, cultural and political institutions.”
The REDD strategy thus must respect traditional knowledge, skills and
the practices of indigenous people.
. Impact: The detrimental and beneficial consequence of climate change
on natural and human systems is known as impact.
. Impact Assessment: The practice of identifying and evaluating the
detrimental and beneficial consequences of climate change on natural
and human systems is known as impact assessment.
. Incentives: Any factor (financial or non-financial) that enables or
motivates a particular course of action or a tangible or intangible
reward that is designed to motivate a person or group to behave in a
certain way is known as incentives.
. Indicators: Quantitative or qualitative parameters that provide a simple
and reliable basis for assessing change is known as indicators. In the
context of the Adaptation Planning Framework (APF), a set of
indicators is used to characterize an adaptation phenomenon to
construct a baseline and to measure and assess changes in the priority
system.

. Indigenous Peoples: People whose ancestors inhabited a place or a
country when persons from another culture or ethnic background
arrived on the scene and dominated them through conquest, settlement,
or other means and who today live more in conformity with their own
social, economic, and cultural customs and traditions than those of the
country of which they now form a part (also referred to as “native,”
“aboriginal” or “tribal” peoples) is known as indigenous peoples.
. Indirect Aerosol Effect: Aerosols may lead to an indirect radiative
forcing of the climate system through acting as condensation nuclei or
modifying the optical properties and lifetime of clouds. Two indirect
effects are distinguished: First indirect effect: cloud albedo or twomey
effect and second indirect effect: cloud lifetime effect or Albrecht effect.
. Infectious Diseases: Infectious diseases, also known as
communicable diseases or transmissible diseases comprise clinically
evident illness (i.e. characteristic medical signs and/or symptoms of
disease) resulting from the infection, presence and growth of pathogenic
biological agents in an individual host organism. In certain cases,
infectious diseases may be asymtomatic for much of their entire course.
Infectious pathogens include some viruses, bacteria, fungi, protozoa,
multicellular parasites and aberrant proteins known as prions. These
pathogens are the cause of disease epidemics, in the sense that without
the pathogen no infectious epidemic occurs.
. Input Based Payment: Something put into a system or expended in its
operation to achieve output or a result, especially energy, work or power
used to drive a machine is known as input based payment.
. Institutional Appraisal: The analysis of institutions, particularly
institutions that are influential in any given context: their role, degree of
influence, how they function and how they inter-relate is known as
institutional appraisal. This is important for understanding key influences
on local livelihoods. It is often done by and with local people through
participatory methods to establish their perceptions of institutional roles.
This can also be called ‘institutional appraisal’ or ‘institutional mapping’.
The term can also apply to analysis of a single institution: its strengths,
weaknesses, leadership, internal structures etc. with a view to
institutional strengthening.

. Integrated Assessment: A method of analysis that combines results
and models from the physical, biological, economic, and social sciences,
and the interactions between these components, in a consistent
framework, to evaluate the status and the consequences of
environmental change and the policy responses to it is known as
integrated assessment.
. Integrated Risk Assessment: The integrated risk assessment for an
asset should jointly consider the likelihood that the asset will experience
a particular impact and the consequences of that impact on the
surrounding community or region (from a health/safety, economic,
environmental, cultural or other point of view)
. Intensive Risk: The risk associated with the exposure of large
concentrations of people and economic activities to intense hazard events,
which can lead to potentially catastrophic disaster impacts involving high
mortality and asset loss is known as intensive risk. Intensive risk is mainly
a characteristic of large cities or densely populated areas that are not
only exposed to intense hazards such as strong earthquakes, active
volcanoes, heavy floods, tsunamis or major storms but also have high
levels of vulnerability to these hazards.
. Interaction Effect: The result or consequence of the interaction of
climate change policy instruments with existing domestic tax systems,
including both cost-increasing tax interaction and cost-reducing
revenue-recycling effect is known as interaction effect. The former
reflects the impact that greenhouse gas policies can have on the
functioning of labor and capital markets through their effects on real
wages and the real return to capital. By restricting the allowable
greenhouse gas emissions, permits, regulations, or a carbon tax raise the
costs of production and the prices of output, thus reducing the real
return to labor and capital.
. Intergovernmental Panel on Climate Change (IPCC): The
Intergovernmental Panel on Climate Change (IPCC) is a scientific
intergovernmental body tasked with reviewing and assessing the most
recent scientific, technical and socio-economic information produced
worldwide relevant to the understanding of climate change. It provides
the world with a clear scientific view on the current state of climate
change and its potential environmental and socio-economic

consequences, notably the risk of climate change caused by human
activity. The panel was first established in 1988 by the World
Meteorological Organization (WMO) and the United Nations
Environment Programme (UNEP), two organizations of the United
Nations, an action confirmed on 6 December 1988 by the United
Nations General Assembly through Resolution 43/53.
. Internal Climate Variability: Variability may result from natural
internal processes within the climate system is known as internal climate
variability.
. International Emissions/Carbon/Energy Tax: International emissions/
carbon/energy tax is a tax imposed on specified sources in participating
countries by an international agency. The revenue is distributed or used
as specified by participating countries or the international agency.
. Introduced Species: A species occurring in an area outside its
historically known natural range as a result of accidental dispersal by
humans is known as introduced species.
. Invasive Species: An introduced species that invades natural habitats
is known as invasive species.
. Investment Additionality: If the value of the Emissions Reduction Unit/
Certified Emission Reduction Unit will significantly improve the financial
and/or commercial viability of the project activity then it is known as
investment additionality.

J
. Joint Implementation: Joint Implementation (JI), is another
mechanism allowing investments in developed countries to generate
emission credit for the same or another developed country.
. Joint Liaison Group (JLG): Group of representative of UNFCCC,
CBD and UNCCD Secretariats set up to explore common activities to
confront problems related to climate change, biodiversity and
desertification.

K
. Known Technological Options: Technologies that exist in operation
or pilot plant stage to-date is known as known technological options. It
does not include any new technologies that will require drastic
technological breakthroughs.
. Kyoto Mechanism: Economic mechanisms based on market principles
that Parties to the Kyoto Protocol can use in an attempt to lessen the
potential economic impacts of greenhouse gas emission reduction
requirements. They include Joint Implementation (Article 6), the Clean
Development Mechanism (Article 12) and Emissions Trading (Article
) is known as Kyoto mechanism.
. Kyoto Protocol: The Kyoto Protocol to the United Nations
Framework Convention on Climate Change (UNFCCC) was adopted
at the Third Session of the Conference of the Parties to the UNFCCC in
in Kyoto, Japan. It contains legally binding commitments, in
addition to those included in the UNFCCC. Countries included in
Annex B of the Protocol (most countries in the Organization for
Economic Cooperation and Development, and countries with
economies in transition) agreed to reduce their anthropogenic
greenhouse gas emissions (carbon dioxide, methane, nitrous oxide,
hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride) by at least
% below 1990 levels in the commitment period 2008 to 2012.

L
. Land Degradation: The United Nations Convention to Combat
Desertification defines land degradation as a reduction or loss in arid,
semiarid, and dry sub-humid areas of the biological or economic
productivity and complexity of rain-fed cropland, irrigated cropland, or
range, pasture, forest and woodlands resulting from land uses or from a
process or combination of processes including processes arising from
human activities and habitation patterns such as: (i) soil erosion caused
by wind and/or water; (ii) deterioration of the physical, chemical and
biological or economic properties of soil; and (iii) long-term loss of
natural vegetation. Land degradation is a concept in which the value of
the biophysical environment is affected by one or more combination of
human-induced processes acting upon the land. It is viewed as any change
or disturbance to the land perceived to be deleterious or undesirable.
. Land Pollution: Land pollution is the degradation of Earth’s land
surfaces often caused by human activities and their misuse of land
resources. It occurs when waste is not disposed properly.
. Land Tenure: Land tenure is the name given, particularly in common
law systems, to the legal regime in which land is owned by an individual,
who is said to “hold” the land.
. Land Use: The total of arrangements, activities, and inputs undertaken
in a certain land cover type (a set of human actions) is known as land use
or it is the social and economic purposes for which land is managed (e.g.
grazing, timber extraction and conservation).
. Land Use Change: A change in the use or management of land by
humans, which may lead to a change in land cover is known as land use
change. Land cover and land-use change may have an impact on the
albedo, evapotranspiration, sources and sinks of greenhouse gases or
other properties of the climate system, and may thus have an impact on
climate locally or globally.
. Land Use Planning: The process undertaken by public authorities to
identify, evaluate and decide on different options for the use of land
including consideration of long term economic, social and environmental
objectives and the implications for different communities and interest

groups, and the subsequent formulation and promulgation of plans that
describe the permitted or acceptable uses is known as land use
planning. Land-use planning can help to mitigate disasters and reduce
risks by discouraging settlements and construction of key installations in
hazard-prone areas, including consideration of service routes for
transport, power, water, sewage and other critical facilities.
. Land Use, Land Use Change and Forestry (LULUCF): Land use,
land-use change and forestry (LULUCF) is defined as, “A greenhouse
gas inventory sector that covers emissions and removals of greenhouse
gases resulting from direct human-induced land use, land-use change
and forestry activities.”
. Landscape: Landscape comprises the visible features of an area of
land including the physical elements of landforms, water bodies such as
rivers, lakes and the sea, living elements of land cover including
indigenous vegetation, human elements including land uses, buildings and
structures and transitory elements such as lighting and weather
conditions.
. Landslide: A mass of material that has slipped downhill by gravity,
often assisted by water when the material is saturated. Rapid movement
of a mass of soil, rock or debris down a slope is known as landslide.
. Leakage: The part of emissions reductions in Annex B countries that
may be offset by an increase of the emission in the non-constrained
countries above their baseline levels is known as leakage. This can
occur through (i) relocation of energy-intensive production in
non-constrained regions; (ii) increased consumption of fossil fuels in these
regions through decline in the international price of oil and gas triggered
by lower demand for these energies; and (iii) changes in incomes (thus in
energy demand) because of better terms of trade. Leakage also refers
to the situation in which a carbon sequestration activity (e.g. tree
planting) on one piece of land inadvertently, directly or indirectly,
triggers an activity, which in whole or part counteracts the carbon effects
of the initial activity.
. Least Developed Countries: Least Developed Country (LDC) is the
name given to a country which, according to the United Nations,
exhibits the lowest indicators of socioeconomic development and with
the lowest Human Development Index ratings of all countries in the world.

. Least Developed Countries Expert Group (LEG): A panel of 12
experts which provides advice to LDCs on the preparation and
implementation of national adaptation programmes of actions (NAPAs)-
plans for addressing the urgent and immediate needs of those countries
to adapt to climate change is known as least developed countries expert
group.
. Least Developed Country Fund (LDCF): The LDCF is a fund
established to support a work programme to assist Least Developed
Country Parties to carry out, inter alia, the preparation and
implementation of National Adaptation Programmes of Action (NAPAs).
The global environment facility as the entity that operated the financial
mechanism of the Convention has been entrusted to operate this fund.
. Livelihood: A livelihood comprises the capabilities, assets and
activities required for a means of living. A livelihood comprises the
capabilities, assets (stores, resources, claims and access) and activities
required for a means of living. A livelihood is sustainable when it can
cope with and recover from stress and shocks, maintain or enhance its
capabilities and assets and provide sustainable livelihood opportunities
for the next generation; and which contributes net benefits to other
livelihoods at the local and global levels in the long- and short-term.
. Livelihood Assets: Assets that the resource poor people possess or
have access to and use to gain a livelihood is known as livelihood assets.
Livelihood assets serve as the basis for people’s livelihoods.
. Livelihood Outcome: Livelihood outcomes are the achievements of
livelihood strategies. Successful livelihood strategies should lead to more
income and more economically sustainable livelihoods, increased
well-being, reduced vulnerability and more sustainable use of the natural
resource base.
. Livelihood Strategies: Livelihood strategies include productive
activities, investment strategies and reproductive choices. The ways in
which poor people deploy their assets and capabilities to improve their
livelihoods (i.e. consumption, production, processing, exchange and
income-generating activities) is known as livelihood strategies. These
are the range and combination of activities and choices that people make/
undertake in order to achieve their livelihood goals. Livelihood

strategies encompass productive activities, investment strategies and
reproductive choices among other things.
. Local Adaptation Plan of Action (LAPA): This will enable
communities to understand the uncertainty of future climatic conditions
and engage effectively in a process of developing adaptation programmes.
They will implement climate resilient plans that are flexible enough to
respond to changing climate and vulnerability conditions. They will also
inform sectoral programmes and catalyze an integrated response to
Climate Change between sectors. Local level adaptation planning
begins at community level, contributes to village development
committee level plans which in turn inform district and national level plans.
. Local Adaptive Capacity: The ability of a local system to adjust to
climate change (including climate variability and extremes) to moderate
potential damages, to take advantage of opportunities or to cope with
the consequences is known as local adaptive capacity.
. Local Communities: A community is a group of interacting organisms
sharing an environment. In human local communities; intent, belief,
resources, preferences, needs, risks and a number of other conditions
may be present and are common affecting the identity of the participants
and their degree of cohesiveness. A local community has been defined
as a group of interacting people living in a common location.
. Local Institutions: A custom, practice, relationship or behavioral
pattern of importance in the life of a community or society is known as
local institutions.

M
. Magnitude: The property of relative size or extent (whether large or
small)
. Maladaptation: Any changes in natural or human systems that
inadvertently increase vulnerability to climatic stimuli. An adaptation that
does not succeed in reducing vulnerability but increases it instead is known
as maladaptation.
. Market Impact: Impacts that are linked to market transactions and
directly affect gross domestic product (GDP, a country’s national
accounts) for example, changes in the supply and price of agricultural
goods is known as market impact.
. Market Mechanism: Market mechanism is a term from economics
referring to the use of money exchanged by buyers and sellers with an
open and understood system of value and time tradeoffs to produce the
best distribution of goods and services.
. Marrakesh Account: The principles in the Marrakesh Accords
respond to concerns that the use of LULUCF (Land Use, Land Use
Change and Forestry) activities should not undermine the environmental
integrity of the Kyoto Protocol. These principles underscore, for
example, the need for sound science and consistent methodologies as
well as the importance of conserving biodiversity. They also specify that
naturally-occurring removals including removals as a consequence of
indirect anthropogenic effects should be excluded from the system and
that any re-release of greenhouse gases (e.g. through forest fires) must
be promptly accounted for.
. Mean Sea Level: Mean Sea Level is normally defined as the average
relative sea level over a period, such as a month or a year, long enough
to average out transients such as waves.
. Meeting of Parties: The Conference of the Parties of the United
Nations Framework Convention on Climate Change will serve as the
Meeting of the Parties (MOP), the supreme body of the Kyoto
Protocol but only Parties to the Kyoto Protocol may participate in

deliberations and make decisions. Until the Protocol enters into force,
MOP cannot meet.
. Meteorology: Meteorology is the interdisciplinary scientific study of
the atmosphere.
. Methane (CH4): Methane is a chemical compound with the chemical
formula CH4. It is the simplest alkane, and the principal component
of natural gas, about 87% by volume. It is a relatively potent greenhouse
gas. Compared with carbon dioxide, it has a high global warming
potential of 72 (calculated over a period of 20 years) or 25 (for a time
period of 100 years). It has a net lifetime of about 10 years; it also
affects the degradation of the ozone layer.
. Micro-climate: A local atmospheric zone where the climate differs from
the surrounding area is known as micro-climate.
. Millennium Development Goals (MDGs): A set of time-bound and
measurable goals for combating poverty, hunger, disease, illiteracy,
discrimination against women and environmental degradation, agreed at
the UN Millennium Summit in 2000 is known as Millennium
Development Goals.
. Mist: Mist is a phenomenon of small droplets suspended in air. It can
occur as part of natural weather and is common in cold air above warmer
water, in exhaled air in the cold. The only difference between mist and
fog is visibility.
. Mitigation: In the context of climate change, mitigation is a human
intervention to reduce the sources or enhance the sinks of greenhouse
gases. Examples include using fossil fuels more efficiently for industrial
processes or electricity generation, switching to solar energy or wind
power, improving the insulation of buildings and expanding forests and
other sinks to remove greater amount of carbon dioxide from the
atmosphere. Tackling climate change by limiting greenhouse gas
emissions is known as mitigation. In Climate Change policy, “mitigation”
is defined differently, being the term used for the reduction of
greenhouse gas emissions that are the source of Climate Change.
. Mitigation Option: Options that maintain existing carbon stocks or
pool of carbon is known as mitigation option.

. Mitigation Measures: Mitigation measures encompass engineering
techniques and hazard-resistant construction as well as improved
environmental policies and public awareness.
. Mitigative Capacity: The social, political and economic structures and
conditions that is required for effective mitigation is known as mitigative
capacity.
. Modified Natural Forest: Forest/other wooded land of naturally
regenerated native species which show clear and visible indications of
human activities is known as modified natural forest. It includes but is
not limited to, selectively logged-over areas, naturally regenerating
areas following agricultural land use, areas recovering from human
induced fires, areas where it is not possible to distinguish whether the
regeneration has been natural or assisted monotypic stand: a forest stand
containing one tree species.
. Monitoring, Reporting and Verification (MRV): MRV can require
that Parties monitor, report and verify environmental compliance data.
Reporting, monitoring, and verification measures can assist States in
tracking their compliance under the respective MRVs. These
requirements vary in formality and reporting methodologies. As
technology has evolved, compliance-related information systems with
computerized databases are increasingly used to collect, sort and
process this information. The advantages of using compliance-related
information systems include increased transparency, ease of data
analysis and verification, and increased efficiency, organization and
prompt compilation of data.
. Monsoon: Wind in the general atmospheric circulation typified by a
seasonal persistent wind direction and by a pronounced change in
direction from one season to the next is known as monsoon.
. Montreal Protocol: The Montreal Protocol on substances that
deplete the ozone layer was adopted in Montreal in 1987 and
subsequently adjusted and amended in London (1990), Copenhagen
(1992), Vienna (1995), Montreal (1997), and Beijing (1999). It
controls the consumption and production of chlorine - and
bromine-containing chemicals that destroy stratospheric ozone, such as
chlorofluorocarbons (CFCs), methyl chloroform, carbon tetrachloride
and many others.

. Multi-model Ensemble: Multi-model ensembles include simulations
by several models and also include the impact of model differences.

N
. National Accounting System: National accounts or National Account
Systems (NAS) are the implementation of complete and consistent
accounting techniques for measuring the economic activity of a nation
(more broadly termed, social accounts).
. National Adaptation Programmes of Actions (NAPAs): Documents
prepared by least developed countries (LDCs) identifying urgent and
immediate activities useful for coping with climate change is known as
national adaptation programes of actions. The NAPAs are then
presented to the international donor community for support to start
adapting to current and projected adverse effects of climate change.
. National (Nepal) Biodiversity Strategy: The Nepal Biodiversity
Strategy (NBS) is an important output of the Biodiversity Conservation
Project of the Ministry of Forests and Soil Conservation (MFSC) of
His Majesty’s Government of Nepal. The Biodiversity Conservation
Project is supported by the Global Environment Facility (GEF) and the
United Nations Development Programme UNDP).The preparation of
the NBS is based on the substantial efforts of and assistance from
numerous scientists, policy-makers and organizations who generously
shared their data and expertise. The document represents the
culmination of hard work by a broad range of government sectors,
nongovernmental organizations and individual stakeholders.
. National Communication: A document submitted in accordance with
the convention (and the protocol) by which a party informs other parties
of activities undertaken to address climate change is known as national
communication. Most developed countries have now submitted their
fourth national communications; most developing countries have
completed their first national communication and are in the process of
preparing their second. Nepal is in the process of preparation of second
national communication.
. National Conservation Strategy: The National Conservation
Strategy are in response to the need for laying down the guidelines that
will help to weave environmental considerations into the fabric of our
national life and of our development process. It is an expression of our
commitment for reorienting policies and action in unison with the
environmental perspective.

. National Platform for Disaster Risk Reduction: A generic term for
national mechanisms for coordination and policy guidance on disaster
risk reduction that are multi-sectoral and inter-disciplinary in nature, with
public, private and civil society participation involving all concerned
entities within a country. Disaster risk reduction requires the knowledge,
capacities and inputs of a wide range of sectors and organizations,
including United Nations agencies present at the national level, as
appropriate. Most sectors are affected directly or indirectly by disasters
and many have specific responsibilities that impinge upon disaster risks.
National platforms provide a means to enhance national action to
reduce disaster risks, and they represent the national mechanism for the
International Strategy for Disaster Reduction.
. National Sovereignty: National sovereignty is the doctrine that
sovereignty belongs to and derives from the nation, an abstract entity
normally linked to a physical territory and its past, present and future
citizens.
. Nationally Appropriate Mitigation Action: Nationally Appropriate
Mitigation Action (NAMA) refers to a set of policies and actions
countries undertake as part of a commitment to reduce greenhouse gas
emissions. The term recognizes that different countries may take
different nationally appropriate action on the basis of equity and in
accordance with common but differentiated responsibilities and
respective capabilities. It also emphasizes financial assistance from
developed countries to developing countries to reduce emissions.
. Natural Capital: The natural resource stocks from which resource flows
useful for livelihoods are derived (including land, water, wildlife,
biodiversity and environmental resources) is known as natural capital.
. Natural Disaster: A natural disaster is the effect of a natural hazard
(e.g. flood, tornado, hurricane, volcanic eruption, earthquake or
landslide). It leads to financial, environmental or human losses. The
resulting loss depends on the vulnerability of the affected population to
resist the hazard also called their resilience. This understanding is
concentrated in the formulation: “disasters occur when hazards meet
vulnerability.” A natural hazard will hence never result in a natural
disaster in areas without vulnerability (e.g. strong earthquakes in
uninhabited areas).

. Natural Ecosystem: A natural ecosystem is a biological environment
consisting of all the organisms living in a particular area, as well as all the
nonliving, physical components of the environment with which the
organisms interact, such as air, soil, water and sunlight. It is all the
organisms in a given area along with the nonliving (abiotic) factors with
which they interact.
. Natural Gas: Natural gas is a gas consisting primarily of methane,
typically with 0-20% higher hydrocarbons (primarily ethane). It is found
associated with other hydrocarbon fuel in coal beds as methane
clathrates and is an important fuel source and a major feedstock for
fertilizers.
. Natural Hazard: Natural process or phenomenon that may cause loss
of life, injury or other health impacts, property damage, loss of
livelihoods and services, social and economic disruption or
environmental damage is known as natural hazard. Natural hazards are
a sub-set of all hazards. The term is used to describe actual hazard
events as well as the latent hazard conditions that may give rise to future
events. Natural hazard events can be characterized by their magnitude
or intensity, speed of onset, duration, and area of extent. For example,
earthquakes have short durations and usually affect a relatively small
region, whereas droughts are slow to develop and fade away and often
affect large regions. In some cases hazards may be coupled, as in the
flood caused by a hurricane or the tsunami that is created by an
earthquake.
. Natural Regeneration: The natural regeneration of vegetation is a
dynamic process by which life recolonises land when the vegetation has
been partially or totally destroyed. Life recovers the lost ground through
the mechanism of the succession of species.
. Nested Approach: A flexible mechanism to reduce emissions from
deforestation is known as nested approach. It is mix of both national
and sub-national approaches where transition to national approach is
mandatory and accounting and crediting take place at both national and
sub-national levels.
. Net Biome Production: Net gain or loss of carbon from a region is
known as Net Biome Production. NBP is equal to the Net Ecosystem

Production minus the carbon lost due to a disturbance (e.g. a forest fire
or a forest harvest).
. Net Carbon Dioxide Emissions: Difference between sources and sinks
of carbon dioxide in a given period and specific area or region is known
as net carbon dioxide emission.
. Net Ecosystem Production (NEP): Net gain or loss of carbon from
an ecosystem is known as Net Ecosystem Production. NEP is equal to
the Net Primary Production minus the carbon lost through heterotrophic
respiration.
. Net Emission: The act of sending or throwing out; the act of sending
forth or putting into circulation; issue as the emission of light from the
sun, the emission of heat from a fire and the emission of bank notes is
known as net emission.
. Net Primary Production (NPP): The increase in plant biomass or
carbon of a unit of a landscape is known as Net Primary Production.
NPP is equal to the Gross Primary Production minus carbon lost through
autotrophic respiration.
. Nitrogen Oxide (NO2): Nitrogen oxide can refer to a binary
compound of oxygen and nitrogen. In atmospheric chemistry and air
pollution and related fields, nitrogen oxides refers specifically to NOx
(NO and NO2). It is also a major greenhouse gas and air pollutant.
Considered over a 100 year period, it has 298 times more impact per
unit weight (Global warming potential) than carbon dioxide.
. No Regrets Options: Technology for reducing greenhouse gas
emissions whose other benefits (in terms of efficiency or reduced energy
costs) are so extensive that the investment is worth it for that reason
alone is known as no regret options. For example: combined cycle gas
turbines-in which the heat from the burning fuel drives steam turbines
while the thermal expansion of the exhaust gases drives gas turbines may
boost the efficiency of electricity generating plants by 70 per cent.
. Non Annex B Countries /Parties: The countries that are not included
in Annex B in the Kyoto Protocol is known as Non Annex B countries/
parties.

. Non Annex I Countries/Parties: The countries that have ratified or
acceded to the United Nations Framework Convention on Climate
Change that are not included in Annex I of the Climate Convention is
known as Non Annex I countries /parties.
. Non Conventional Energy: Energy such as fuel cells, production of
hydrogen through the solar or nuclear route including its storage
facilities, wind and tidal energy etc. also have to be developed as
alternatives to fossils fuels is known as non conventional energy.
. Non Governmental Organization: A non-profit group or association
organized outside of institutionalized political structures to realize
particular social and/or environmental objectives or serve particular
constituencies is known as Non Governmental Organizations.
. Non Market Impacts: Impacts that affect ecosystems or human
welfare but that are not directly linked to market transactions for
example, an increased risk of premature death is known as non market
impacts.
. Non Structural Measures: Any measure not involving physical
construction that uses knowledge, practice or agreement to reduce risks
and impacts, in particular through policies and laws, public awareness
raising, training and education is known as non structural measures.
Common structural measures for disaster risk reduction include dams,
flood levies, ocean wave barriers, earthquake-resistant construction and
evacuation shelters. Common non-structural measures include building
codes, land use planning laws and their enforcement, research and
assessment, information resources and public awareness programmes.
. Nuclear Energy: A very important source of non carbon energy is
known as nuclear energy.

O
. OECD Countries: Organization for Economic Co-operation and
Development (OECD) was established at 1992 to promote policies
that will improve the economic and social well-being of people around
the world. The OECD provides a forum in which governments can work
together to share experiences and seek solutions to common problems.
. Offset: A carbon offset is a reduction in emissions of carbon or
greenhouse gases made in order to compensate for or to offset an
emission made elsewhere. Carbon offsets are measured in metric tons
of carbon dioxide-equivalent (CO2e) and may represent six primary
categories of greenhouse gases. One carbon offset represents the
reduction of one metric ton of carbon dioxide or its equivalent in other
greenhouse gases.
. Open Access: Easy and open access to the resources is known as
open access.
. Opportunity Cost: Opportunity cost is the cost related to the
next-best choice available to someone who has picked among several
mutually exclusive choices. It is a key concept in economics. It has been
described as expressing “the basic relationship between scarcity and
choice.”
. Organic Aerosol: Aerosol particles consisting predominantly of
organic compounds, mainly C, H and O, and lesser amounts of other
elements is known as organic aerosol.
. Output Based Payment: The Output Based Payment System (OPS)
is based on the simple principle of exchanging goods and services against
a reasonable price. OPS is a performance based management approach
which links the payment of service providers (SP) to their delivery of
services or outputs.
. Ozone: The triatomic form of oxygen (O3) is a gaseous atmospheric
constituent is known as ozone. It is created in troposphere and
stratosphere.

. Ozone Layer: The stratosphere contains a layer in which the
concentration of ozone is greatest; this is known as ozone layer. The
layer extends from about 12 to 40 km. The ozone concentration reaches
a maximum between about 20 and 25 km. This layer is being depleted
by human emissions of chlorine and bromine compounds. Every year,
during the Southern Hemisphere spring, a very strong depletion of the
ozone layer takes place over the Antarctic region also caused by
human-made chlorine and bromine compounds in combination with the
specific meteorological conditions of that region. This phenomenon is
called the ozone hole.
. Ozone Layer Depletion: Ozone depletion describes two distinct but
related observations: a slow, steady decline of about four per cent per
decade in the total volume of ozone in Earth’s stratosphere (the ozone
layer) since the late 1970s and a much larger but seasonal decrease in
stratospheric ozone over Earth’s polar regions during the same period.
The latter phenomenon is commonly referred to as the ozone hole. In
addition to this well-known stratospheric ozone depletion there are also
tropospheric ozone depletion events which occur near the surface in
Polar Regions during spring.
. Ozone Pollution: Ozone pollution is a form of pollution which is
characterized by high concentrations of ozone, a form of oxygen, at
ground level. Exposure to ozone can cause serious health problems in
plants and people, and ozone pollution is a major problem in some
regions of the world.

P
. Parameterization: In climate models, this term refers to the technique
of representing processes that can not be explicitly resolved at the
spatial or temporal resolution of the model (sub-grid scale processes)
by relationships between the area or time-averaged effect of such
sub-grid-scale processes and the larger scale flow.
. Parts Per Billion (ppb): Represents the concentration of something in
water or soil. One ppb represents one microgram of something per liter
of water (ug/l) or one microgram of something per kilogram of soil
(ug/kg).
. Parts Per Million (ppm): This is a way of expressing very dilute
concentrations of substances. Just as per cent means out of a hundred,
so parts per million or ppm means out of a million. Usually describes the
concentration of something in water or soil. One ppm is equivalent to
one milligram of something per liter of water (mg/l) or one milligram of
something per kilogram soil (mg/kg).
. Payment: A payment is the transfer of wealth from one party (such as a
person or company) to another. A payment is usually made in exchange
for the provision of goods, services or both or to fulfill a legal obligation.
. Payment for Environmental Services (PES): Payments for
Environmental Services are part of a new and more direct conservation
paradigm, explicitly recognizing the need to bridge the interests of
landowners and outsiders. Eloquent theoretical assessments have praised
the absolute advantages of PES over traditional conservation approaches.
PES is a highly promising conservation approach that can benefit
buyers, sellers and improve the resource base but it is unlikely to
completely outstrip other conservation instruments.
. Perfluorocarbons (PFCs): It is among the six greenhouse gases to be
abated under the Kyoto Protocol. These are by-products of aluminum
smelting and uranium enrichment. They also replace
chlorofluorocarbons in manufacturing semiconductors. The Global
Warming Potential of PFCs is 6,500 - 9,200 times that of carbon
dioxide.

. Performance Based Payment (PBP): It is a form of contractor
financing based on the completion of authorized work. PBPs are for use
on fixed-price contractual arrangements. The main focus is on the
completion of authorized work taking the form of milestones points in
time. No payments are paid to contractors until the agreed-to
milestones are completely finished.
. Permanence: Temporary nature of credits is known as permanence. It
is the property of being able to exist for an indefinite duration.
. Permits: Emissions trading in domestic systems is known as permits.
. Perturbed Parameter Ensembles: Ensembles in which model
parameters are varied in a systematic manner. It aims to produce a more
objective estimate of modeling uncertainty than is possible with
traditional multi-model ensembles is know as perturbed parameter
ensembles.
. Phased Approach: It is the stage or the approach in a process of
change or development.
. Phenology: The study of natural phenomena in biological systems that
recur periodically (e.g. development stages and migration) and their
relation to climate and seasonal changes is known as phenology.
. Photosynthesis: The process by which plants take carbon dioxide (CO2)
from the air (or bicarbonate in water) to build carbohydrates, releasing
oxygen (O2) in the process. There are several pathways of
photosynthesis with different responses to atmospheric CO2
concentrations is known as photosynthesis.
. Physical Capital: The basic infrastructure (transport, shelter, water,
energy and communications) and the production equipment and means
which enable people to pursue their livelihoods is known as physical
capital.
. Planned Adaptation: Adaptation that is the result of a deliberate policy
decision based on an awareness that conditions have changed or are
about to change and that action is required to return to maintain or achieve
a desired state is known as planned adaptation.

. Plantation: Forest/other wooded land of introduced species and in some
cases native species established through planting or seeding, mainly for
production of wood or non-wood goods is known as plantation.
. Polluters Pay Principle (PPP): The Polluter Pays Principle is an
environmental policy principle which requires that the costs of pollution
be borne by those who cause it. In its original emergence the Polluter
Pays Principle aims at determining how the costs of pollution prevention
and control must be allocated.
. Pollution: Pollution is the introduction of contaminants into a natural
environment that causes instability, disorder, harm or discomfort to the
ecosystem i.e. physical systems or living organisms. Pollution can take
the form of chemical substances or energy, such as noise, heat or light.
. Post Glacial Rebound: The vertical movement of the continents and
sea floor following the disappearance and shrinking of ice sheets for
example, since the Last Glacial Maximum (21 ky BP) is known as post
glacial rebound. The rebound is an isostatic land movement.
. Potential Impacts: All impacts that may occur given a projected change
in climate, without considering adaptation is known as potential impacts.
. Precipitation: Precipitation is any product of the condensation of
atmospheric water vapor that falls under gravity. The main forms of
precipitation include drizzle, rain, sleet, snow, graupel and hail. It occurs
when a local portion of the atmosphere becomes saturated with water
vapor and the water condenses two processes possibly acting together
that can lead to air becoming saturated: cooling the air or adding water
vapor to the air.
. Preparedness: The knowledge and capacities developed by
governments, professional response and recovery organizations,
communities and individuals to effectively anticipate, respond to and
recover from the impacts of likely, imminent or current hazard events or
conditions is known as preparedness. Preparedness action is carried
out within the context of disaster risk management and aims to build the
capacities needed to efficiently manage all types of emergencies and
achieve orderly transitions from response through to sustained recovery.
Preparedness is based on a sound analysis of disaster risks and good

linkages with early warning systems, and includes such activities as
contingency planning, stockpiling of equipment and supplies, the
development of arrangements for coordination, evacuation and public
information and associated training and field exercises. The related term
“readiness” describes the ability to quickly and appropriately respond
when required.
. Prevention: The outright avoidance of adverse impacts of hazards and
related disasters is known as prevention. Prevention (i.e. disaster
prevention) expresses the concept and intention to completely avoid
potential adverse impacts through action taken in advance. Examples
include dams or embankments that eliminate flood risks, land-use
regulations that do not permit any settlement in high risk zones, and
seismic engineering designs that ensure the survival and function of a
critical building in any likely earthquake.
. Primary Energy/Energy Sources: Primary energy (also referred to
as energy sources) is the energy embodied in natural resources
(e.g. coal, crude oil, natural gas and uranium) that has not undergone
any anthropogenic conversion. This primary energy needs to be
converted and transported to become usable energy (e.g. light).
. Primary forest: Forest/other wooded land of native species where
there are no clearly visible indications of human activities and the
ecological processes are not significantly disturbed is known as primary
forest.
. Priority Sector: The sectors or the area which needs urgent attention
to address is known as priority sector.
. Private Adaptation: Adaptation that is initiated and implemented by
individuals, households or private companies is known as private
adaptation. Private adaptation is usually in the actor’s rational
self-interest.
. Productivity or Production: The rate at which biomass is produced
per unit area by any class of organisms is known as productivity or
production.

. Projection: A projection is a potential future evolution of a quantity or
set of quantities often computed with the aid of a model. Projections are
distinguished from “predictions” in order to emphasize that projections
involve assumptions concerning, for example, future socio-economic and
technological developments that may or may not be realized and are
therefore subject to substantial uncertainty.
. Prospective Disaster Risk Management: Management activities that
address and seek to avoid the development of new or increased
disaster risks is known as prospective disaster risk management. This
concept focuses on addressing risks that may develop in future if risk
reduction policies are not put in place, rather than on the risks that are
already present and which can be managed and reduced now.
. Protocol: An international agreement linked to an existing convention,
but as a separate and additional agreement which must be signed and
ratified by the parties to the convention concerned is known as
protocol. Protocols typically strengthen a convention by adding new,
more detailed commitments.
. Provisioning Services: The benefits that ecosystem can provide such
as food and water is known as “provisioning services”.
. Proxy: A proxy climate indicator is a local record that is interpreted,
using physical and biophysical principles, to represent some
combination of climate-related variations back in time. Climate-related
data derived in this way are referred to as proxy data. Examples of
proxies are tree ring records, characteristics of corals and various data
derived from ice cores.
. Public Adaptation: Adaptation that is initiated and implemented by
governments at all levels is known as public adaptation. Public
adaptation is usually directed at collective needs.
. Public Awareness: The extent of common knowledge about Climate
Change, the factors that lead to climate induced disasters and the
actions that can be taken individually and collectively to reduce
exposure and vulnerability to hazards is known as public awareness.
Public awareness is a key factor in effective adaptation strategies. Its
development is pursued, for example, through the development and

dissemination of information through media and educational channels,
the establishment of information centres, networks, and community or
participation actions and advocacy by senior public officials and
community leaders.

Q
. Quotas: Emissions trading in international systems is known as quotas.

R
. Rainfall: Rain is liquid precipitation, as opposed to non-liquid kinds of
precipitation such as snow, hail and sleet. Rain requires the presence of
a thick layer of the atmosphere to have temperatures above the melting
point of water near and above the Earth’s surface
. Rapid Climate Change: The non-linearity of the climate system may
lead to rapid Climate Change, sometimes called abrupt events or even
surprises. Some such abrupt events may be imaginable, such as a
dramatic reorganization of the thermohaline circulation, rapid deglaciation
or massive melting of permafrost leading to fast changes in the carbon
cycle. Others may be truly unexpected, as a consequence of a strong,
rapidly changing and forcing of a non-linear system.
. Ratification: Formal approval, often by a parliament or other national
legislature, of a convention, protocol or treaty, enabling a country to
become a Party is known as ratification. Ratification is a separate
process that occurs after a country has signed an agreement, the
instrument of ratification must be deposited with a depositary (in the
case of the climate change convention the UN secretary general) to start
the countdown to becoming a party (in the case of the convention, the
countdown is 90 days).
. Reactive Adaptation: Adaptation that takes place after impacts of
climate change have been observed is known as reactive adaptation.
. Readiness Preparation Proposal (R-PP): The R-PP is a roadmap
toward achieving REDD Readiness. It indicates what activities could be
undertaken and provides a guide to how these activities can be
undertaken and what resources will be needed. It does not seek to
define the outcome of these activities but provides draft Terms of
Reference (ToR) for further defining them.
. Recovery: The restoration and improvement where appropriate of
facilities, livelihoods and living conditions of disaster-affected
communities including efforts to reduce disaster risk factors is known as
recovery.

. REDD Standards: This initiative is developing standards that can be
used by governments, NGOs, financing agencies and other
stakeholders to design and implement REDD+ programs that respect
the rights of indigenous peoples and local communities and generate
significant social and environmental co-benefits. The standards have been
developed through an inclusive process engaging governments, NGOs
and other civil society organizations, indigenous peoples organizations,
international policy and research institutions and the private sector.
. Reference Scenario: The reference scenario provides a plausible
picture of a future in the priority system without adaptation, to allow for
comparison of different adaptation strategies, policies and measures.
. Reforestation: Planting of forests on lands that have previously
contained forests but that have been converted to some other use or the
direct human-induced conversion of non-forested land to forested land
through planting, seeding and/or the human-induced promotion of
natural seed sources, on land that was forested but that has been
converted to non-forested land is known as reforestation.
. Regeneration: In biology, regeneration is the process of renewal,
restoration, and growth that makes genomes, cells, organs, organisms,
and ecosystems resilient to natural fluctuations or events that cause
disturbance or damage. Every species is capable of regeneration from
bacteria to humans.
. Regime: A regime is a preferred state of the climate system, often
representing one phase of dominant patterns or modes of climate
variability.
. Region: A region is a territory characterized by specific geographical
and climatological features. The climate of a region is affected by
regional and local scale forcing such as topography, land use
characteristics, lakes etc. as well as remote influences from other
regions.
. Regulating Services: The benefits that ecosystems can provide such
as regulation of floods, drought, land degradation and disease is known
as “regulating services.”

. Rehabilitation: Rehabilitation is a treatment or treatments designed to
facilitate the process of recovery from injury, illness or disease to as
normal a condition as possible.
. Relative Sea Level Rise: Relative sea-level rise occurs where there
is a net increase in the level of the ocean relative to local land
movements. Impact researchers focus on relative sea-level change.
. Relief Response: Relief Respone also known as Emergency
Management is the generic name of an interdisciplinary field dealing with
the strategic organizational management processes used to protect
critical assets of an organization from hazard risks that can cause
disasters or catastrophes and to ensure their continuance within their
planned lifetime.
. Remote Sensing: Remote sensing is the small or large scale acquisition
of information of an object or phenomenon by the use of either
recording or real-time sensing device(s) that are wireless, or not in
physical or intimate contact with the object (such as by way of aircraft,
spacecraft, satellite, buoy, or ship). In practice, remote sensing is the
stand-off collection through the use of a variety of devices for gathering
information on a given object or area.
. Removals: The act of removing or state of being removed is known as
removals.
. Removals Unit (RMU): A Removal Unit is a tradable carbon credit
or ‘Kyoto unit’ representing an allowance to emit one metric tonne of
greenhouse gases absorbed by a removal or Carbon sink activity in an
Annex I country. Removal Units are generated and issued by Kyoto
Protocol Annex I Parties for carbon absorption by Land use, Land-use
Change and Forestry (LULUCF) activities such as reforestation.
. Renewable Energy: The gases circling the Earth that are essential in
helping to determine the temperature of the Earth; without them this
planet would likely be so cold as to be uninhabitable is known as
renewable energy. Renewable energy is obtained from the continuing or
repetitive currents of energy occurring in the natural environment, and
includes non-carbon technologies such as solar energy, hydropower,
wind, tide and waves and geothermal heat as well as carbon neutral
technologies such as biomass.

. Reservoirs: A component or components of the climate system where
a greenhouse gas or a precursor of a greenhouse gas is stored is known
as reservoirs. Trees are reservoirs for carbon dioxide.
. Residual Impacts: The impacts of climate change that would occur
after adaptation is known as residual impacts.
. Residual Risk: The risk that remains in unmanaged form, even when
effective disaster risk reduction measures are in place and for which
emergency response and recovery capacities must be maintained is
known as residual risk. The presence of residual risk implies a
continuing need to develop and support effective capacities for
emergency services, preparedness, response and recovery together with
socio-economic policies such as safety nets and risk transfer
mechanisms.
. Resilience: The capacity of a system, community or society potentially
exposed to hazards to adapt by resisting or changing in order to reach
and maintain an acceptable level of functioning and structure is known
as resilience. This is determined by the degree to which the social
system is capable of organizing itself to increase its capacity for learning
from past disasters for better future protection and to improve risk
reduction measures. The ability of a system, community or society
exposed to hazards to resist, absorb, accommodate to and recover from
the effects of a hazard in a timely and efficient manner, including through
the preservation and restoration of its essential basic structures and
functions. It is the amount of change a system can undergo without
changing state.
. Resistance: The capacity of the ecosystem to absorb disturbances
and remain largely unchanged.
. Response: The provision of emergency services and public assistance
during or immediately after a disaster in order to save lives reduces
health impacts, ensure public safety and meet the basic subsistence needs
of the people affected is known as response.
. Response Time: The response time or adjustment time is the time
needed for the climate system or its components to re-equilibrate to a
new state following a forcing resulting from external and internal

processes or feedbacks. It is very different for various components of
the climate system. The response time of the troposphere is relatively
short, from days to weeks, whereas the stratosphere comes into
equilibrium on a time scale of typically a few months. Due to their large
heat capacity the oceans have a much longer response time, typically
decades but up to centuries or millennia. The response time of the strongly
coupled surface troposphere system is, therefore, slow compared to
that of the stratosphere and mainly determined by the oceans. The
biosphere may respond fast (e.g. to droughts) but also very slowly to
imposed changes.
. Restoration: Returning a work to a better state is known as
restoration.
. Result Based Payment: Result based payment is an initiative to and
implement a reimbursement system that rewards care quality and results
is known as result based payment. Result based payment would align
the positive attributes of the current payment process with a
reimbursement system based on appraisal of quality care and
appropriate outcomes.
. Retrofitting: Reinforcement or upgrading of existing structures to
become more resistant and resilient to the damaging effects of hazards is
known as retrofitting. Retrofitting requires consideration of the design
and function of the structure, the stresses that the structure may be
subject to from particular hazards or hazard scenarios and the
practicality and costs of different retrofitting options. Examples of
retrofitting include adding bracing to stiffen walls, reinforcing pillars, adding
steel ties between walls and roofs, installing shutters on windows and
improving the protection of important facilities and equipment.
. Risk: The combination of the probability of an event and its negative
consequences is known as risk. It is the result of interaction of physically
defined hazards with the properties of the exposed systems that is their
sensitivity or (social) vulnerability. Risk can also be considered as the
combination of an event, its likelihood and its consequences that is risk
equals the probability of climate hazard multiplied by a given system’s
vulnerability.

. Risk Assessment: A methodology to determine the nature and extent
of risk by analyzing potential hazards and evaluating existing conditions
of vulnerability that together could potentially harm exposed people,
property, services, livelihoods and the environment on which they
depend is known as risk assessment.
. Risk Management: The systematic approach and practice of
managing uncertainty to minimize potential harm and loss is known as
risk management. Risk management comprises risk assessment and
analysis, and the implementation of strategies and specific actions to
control, reduce and transfer risks. It is widely practiced by organizations
to minimize risk in environmental damage, social impacts and damage
from fire and natural hazards. Risk management is a core issue for
sectors such as water supply, energy and agriculture whose production
is directly affected by extremes of weather and climate.
. Risk Mapping: The process of identifying high-risk areas is known as
risk mapping. This is done by correlating a hazard, such as an
earthquake, to the terrain and to the probability that such an event will
occur. The results of these analyses are usually presented in the form
of risk maps, which show the type and degree of hazard represented by
a particular natural phenomenon at a given geographic location. Risk
mapping is usually the first step in vulnerability reduction.
. Risk Transfer: The process of formally or informally shifting the
financial consequences of particular risks from one party to another
whereby a household, community, enterprise or state authority will
obtain resources from the other party after a disaster occurs, in
exchange for ongoing or compensatory social or financial benefits
provided to that other party is known as risk transfer. Insurance is a
well-known form of risk transfer, where coverage of a risk is obtained
from an insurer in exchange for ongoing premiums paid to the insurer.
Risk transfer can occur informally within family and community networks
where there are reciprocal expectations of mutual aid by means of gifts
or credit, as well as formally where governments, insurers, multi-lateral
banks and other large risk-bearing entities establish mechanisms to help
cope with losses in major events. Such mechanisms include insurance
and re-insurance contracts, catastrophe bonds, contingent credit
facilities and reserve funds, where the costs are covered by premiums,
investor contributions, interest rates and past savings respectively.

. Runoff: Runoff is a term used to describe the water from rain,
snowmelt or irrigation that flows over the land surface and is not
absorbed into the ground, instead flowing into streams or other surface
waters or land depressions.

S
. Safeguard Principles: A safeguard is a law or a rule used to restrain
international trade in order to protect a certain home industry from
foreign competition.
. Scenario: A plausible and often simplified description of how the future
may develop based on a coherent and internally consistent set of
assumptions about key driving forces (e.g. rate of technology change,
prices, etc.) and relationships is known as scenario. Scenarios are
neither predictions nor forecasts and sometimes may be based on a
“narrative storyline.” Scenarios may be derived from projections but are
often based on additional information from other sources.
. Scoping: Scoping is used to identify the key issues of concern at an
early stage in the planning process. Scoping should be carried out at an
early stage in order to aid site selection and identify any possible
alternatives. The scoping process should involve all interested parties
such as the proponent and planning or environmental agencies and
members of the public.
. Sea Level Rise: An increase in the mean level of the ocean is known
as sea level rise.
. Second Assessment Report (SAR): An extensive review of
worldwide research on climate change compiled by the IPCC and
published in 1995 is known as second assessment report. The report is
also known as Climate Change 1995.
. Secondary Forest: A degraded forest is a secondary forest that has
lost through human activities, the structure, function, species
composition or productivity normally associated with a natural forest
type expected on that site. Hence, a degraded forest delivers a reduced
supply of goods and services from the given site and maintains only
limited biological diversity. Biological diversity of degraded forests
includes many non-tree components, which may dominate in the
under-canopy vegetation.
. Secretariat: The office staffed by international civil servants
responsible for servicing the UNFCCC convention and ensuring its

smooth operation is known as secretariat. The secretariat makes
arrangements for meetings, compiles and prepares reports and
coordinates with other relevant international bodies. The Climate Change
secretariat which is based in Bonn, Germany is institutionally linked to
the United Nations.
. Sector: Part or division, as of the economy (e.g. the manufacturing
sector, the services sector) or the environment (e.g. water resources,
forestry) is known as sector.
. Sensitivity: The degree to which a system is affected, either adversely
or beneficially by climate-related stimuli is known as sensitivity. The
effect may be direct (e.g. a change in crop yield in response to a change
in the mean, range, or variability of temperature) or indirect (e.g.
damages caused by an increase in the frequency of coastal flooding due
to sea-level rise).
. Sequestration: The process of increasing the carbon content of a
carbon reservoir other than the atmosphere is known as sequestration.
Biological approaches to sequestration include direct removal of carbon
dioxide from the atmosphere through land-use change, afforestation,
reforestation, and practices that enhance soil carbon in agriculture. Physical
approaches include separation and disposal of carbon dioxide from flue
gases or from processing fossil fuels to produce hydrogen and carbon
dioxide-rich fractions and long-term storage in underground in depleted
oil and gas reservoirs, coal seams and saline aquifers.
. Shock: Shocks are sudden, unexpected or unpredictable events that
have impacts on livelihood security are known as shock.
. Silviculture: Development and care of forests or the art of producing
and tending a forest by manipulating its establishment, composition and
growth to best fulfill the objectives of the owner is known as silviculture.
Silviculture is the science, art and practice of caring for forests with
respect to human objectives. This may or may not include timber
production. The name comes from the Latin silvi- (forest) + culture (as
in growing).
. Sink: Any process, activity or mechanism that removes a greenhouse
gas, an aerosol, or a precursor of a greenhouse gas or aerosol from the

atmosphere is known as sink. Forests and other vegetation are
considered sinks because they remove carbon dioxide through
photosynthesis.
. Site-specific Approach: Site-specific Approach seeks to develop and
assess detailed adaptation strategies on the basis of specific perceptions
of vulnerability that have emerged from the full range of stakeholders at
the site level (e.g. local communities and local projects).
. Slash and Burn: Slash and burn consists of cutting and burning of
forests or woodlands to create fields for agriculture or pasture for
livestock, or for a variety of other purposes. It is sometimes part of
shifting cultivation agriculture, and of transhumance livestock herding.
Slash and burn agriculture typically uses little technology and other tools,
and is almost always done for subsistence activity.
. Snow: Snow is a type of precipitation within the Earth’s atmosphere in
the form of crystalline water ice consisting of a multitude of snowflakes
that fall from clouds. Since snow is composed of small ice particles, it is
a granular material. It has an open and therefore soft structure, unless
packed by external pressure.
. Snow Packs: A seasonal accumulation of slow-melting snow is known
as snowpack.
. Snowline: The climatic snow line is the point above which snow and ice
cover the ground throughout the year. The actual snow line may
seasonally be significantly lower.
. Social Capital: The social resources upon which people draw in
pursuit of livelihoods (i.e. networks, membership of groups,
relationships of trust, access to wider institutions of society, etc.) is known
as social capital.
. Social Vulnerability: Social vulnerability is one dimension of vulnerability
to multiple stressors and shocks, including natural hazards. Social
vulnerability refers to the inability of people, organizations, and societies
to withstand adverse impacts from multiple stressors to which they are
exposed. These impacts are due in part to characteristics inherent in
social interactions, institutions and systems of cultural values.

. Socio-economic Vulnerability: An aggregate measure of human
welfare that integrates environmental, social, economic and political
exposure to a range of harmful perturbations is known as
socio-economic vulnerability.
. Socio Natural Hazard: The phenomenon of increased occurrence of
certain geophysical and hydro-meteorological hazard events, such as
landslides, flooding, land subsidence and drought that arise from the
interaction of natural hazards with overexploited or degraded land and
environmental resources is known as socio natural hazard.
Socio-natural hazards can be reduced and avoided through wise
management of land and environmental resources.
. Soil Erosion: Erosion is the process of weathering and transport of
solids (sediment, soil, rock and other particles) in the natural
environment or their source and deposits them elsewhere. It usually
occurs due to transport by wind, water or ice, by down-slope creep of
soil and other material under the force of gravity, or by living organisms,
such as burrowing animals in the case of bio-erosion.
. Soil Moisture: Water stored in or at the land surface and available for
evaporation is known as soil moisture.
. Soot Particles: Particles formed during the quenching of gases at the
outer edge of flames of organic vapors consisting predominantly of
carbon, with lesser amounts of oxygen and hydrogen present as
carboxyl and phenolic groups and exhibiting an imperfect graphitic
structure is known as soot particles.
. Source: Any process, activity, or mechanism that releases a greenhouse
gas, an aerosol or a precursor of a greenhouse gas or aerosol into the
atmosphere is known as source.
. Spatial Scale: Climate may vary on a large range of spatial scales, it
may range from local (less than 100,000 km2), through regional (100,000
to 10 million km2) to continental (10 to 100 million km2) and this is know
as spatial scale.
. Special Climate Change Fund (SCCF): The SCCF was established
to finance projects relating to adaptation, technology transfer and

capacity building, energy, transport, industry, agriculture, forestry and
waste management and economic diversification. This fund should
complement other funding mechanisms for the implementation of the
convention.
. Specific Humidity: A ratio of mass quantities of water vapor to dry air,
such as 1:200. Humidity indicates the likelihood of precipitation, dew or
fog is known as specific humidity.
. Spill Over Effect: The economic effects of domestic or sectoral
mitigation measures on other countries or sectors is known as spill over
effect. Spillover effects can be positive or negative and include effects
on trade, carbon leakage, transfer and diffusion of environmentally sound
technology and other issues.
. Spring: Spring is one of the four temperate seasons, the transition
period between winter and summer. Spring and “springtime” refer to the
season, and broadly to ideas of rebirth, renewal and regrowth. The
specific definition of the exact timing of “spring” varies according to
local climate, cultures and customs. At the spring equinox, days are close
to 12 hours long with day length increasing as the season progresses.
. Stability: The capacity of an ecosystem to remain more or less in the
same state within bounds, that is, the capacity to maintain a dynamic
equilibrium in time while resisting change.
. Stabilization: The achievement of stabilization of atmospheric
concentrations of one or more greenhouse gases (e.g. carbon dioxide or
a CO2 equivalent basket of greenhouse gases) is known as stabilization.
. Stabilization Analysis: Analysis of a scenario that address the
stabilization of the concentration of greenhouse gases is known as
stabilization analysis.
. Stakeholder: Person or entity holding grants, concessions, or any other
type of value that would be affected by a particular action or policy is
known as stakeholder.
. Stern Report/ Review: The Stern Review on the Economics of
Climate Change is a 700 page report released for the British

government on October 30, 2006 by economist Nicholas Stern, Chair
of the Grantham Research Institute on Climate Change and the
Environment at the London School of Economics and also chair of the
Centre for Climate Change Economics and Policy (CCCEP) at Leeds
University and LSE. The report discusses the effect of global warming
on the world economy. Although not the first economic report on
Climate Change, it is significant as the largest and most widely known
and discussed report of its kind.
. Stimuli: All the elements of climate change including mean climate
characteristics, climate variability and the frequency and magnitude of
extremes is known as stimuli.
. Storm: A storm is any disturbed state of an astronomical body’s
atmosphere, especially affecting its surface, and strongly implying
severe weather. It may be marked by strong wind, thunder and lightning
(a thunderstorm), heavy precipitation, such as ice (ice storm) or wind
transporting some substance through the atmosphere (as in a dust storm,
snowstorm, hailstorm, etc.). Storms generally lead to significant
negative impacts to lives and property, such as storm surge, heavy rains,
lightning, wildfires and vertical wind shear which can cause airplane
crashes.
. Strategy: A broad plan of action that is implemented through policies
and measures is known as strategy.
. Stratosphere: The highly stratified region of the atmosphere above the
troposphere extending from about 10 km (ranging from 9 km in high
latitudes to 16 km in the tropics on average) to about 50 km is known as
stratosphere.
. Stratospheric Ozone: Ozone created by the interaction between solar
ultraviolet radiation and molecular oxygen (O2) is known as stratospheric
ozone. Stratospheric ozone plays a decisive role in the stratospheric
radiative balance. Its concentration is highest in the ozone layer.
Depletion of stratospheric ozone, due to chemical reactions that may be
enhanced by Climate Change which results in an increased ground-level
flux of ultraviolet-B radiation.

. Stress: Stresses are long-term trends that undermine livelihood
potential. These include inadequate public services, poor transport, bad
communications, inferior education and inadequate health systems. Other
stresses include a steady decline in the quantity and quality of stocks of
natural resources, climate change, political instability and national or
regional economic decline that negatively impact on household
livelihoods.
. Structural Means: Any physical construction to reduce or avoid
possible impacts of hazards or application of engineering techniques to
achieve hazard resistance and resilience in structures or systems is known
as structural means.
. Subsidiary Body for Scientific and Technology Advice: A
subsidiary body for scientific and technological advice is hereby
established to provide the Conference of the Parties and, as
appropriate, its other subsidiary bodies with timely information and
advice on scientific and technological matters relating to the Convention.
This body shall be open to participation by all Parties and shall be
multidisciplinary. It shall comprise government representatives
competent in the relevant field of expertise. It shall report regularly to the
Conference of the Parties on all aspects of its work.
. Subsidiary Body of Implementation: The Subsidiary Body for
Implementation (SBI) is an advisory body established under the United
Nations Framework Convention on Climate Change to make
“recommendations on policy and implementation issues to the COP and
if requested, to other bodies.” The SBI is one of two permanent
subsidiary bodies created by the convention, with the other being the
Subsidiary Body for Scientific and Technological Advice (SBSTA).
. Succession: Progressive changes in species composition and forest
community structure caused by natural processes (nonhuman) over time.
. Sulfur Hexafluoride (SF6): One of the six greenhouse gases to be
curbed under the Kyoto Protocol. It is largely used in heavy industry to
insulate high-voltage equipment and to assist in the manufacturing of
cable-cooling systems. Its Global Warming Potential is 23,900.

. Summer: Summer is the warmest of the four temperate seasons,
between spring and autumn. At the summer solstice, the days are
longest and the nights are shortest, with day-length decreasing as the
season progresses after the solstice.
. Supporting Services: The benefits that ecosystem can provide such as
soil formation and nutrient cycling that maintain the conditions for life on
earth is known as “supporting services”.
. Surface runoff: The water that travels over the soil surface to the
nearest surface stream or other surface water on land depression is known
as surface runoff.
. Sustainability: Development that meets the needs of the present
without compromising the ability of future generations to meet their own
needs is known as sustainability.
. Sustainable Development: Sustainable Development (SD) is a
pattern of resource use that aims to meet human needs while preserving
the environment so that these needs can be met not only in the present,
but also for generations to come (sometimes taught as
ELF-Environment, Local people and Future). Sustainable development
is development that “meets the needs of the present without
compromising the ability of future generations to meet their own needs.
Sustainable development ties together concern for the carrying capacity
of natural systems with the social challenges facing humanity.
. Sustainable Forest Management: Sustainable Forest Management
(SFM) is the management of forests according to the principles of
sustainable development. Sustainable forest management uses very broad
social, economic and environmental goals.
. Sustainable Livelihood: A livelihood is sustainable when it can cope
with and recover from external stresses and shocks and maintain or
enhance its capabilities and assets now and in the future.
. Sustainable Use: Sustainability is the capacity to use the present
resources without detoriating the resources for the use of future
generations. In ecology, the word describes how biological systems
remain diverse and productive over time. Long-lived and healthy
wetlands and forests are examples of sustainable biological systems.

. System: A region, a community, a household, an economic sector, a
business, a population group, etc. that is exposed to varying degrees to
different climate hazards is known as system.

T
. Technology: A piece of equipment or a technique for performing a
particular activity is known as technology. The adverse impacts of
hazards often cannot be prevented fully but their scale or severity can be
substantially lessened by various strategies and actions.
. Technological Hazard: A hazard originating from technological or
industrial conditions, including accidents, dangerous procedures,
infrastructure failures or specific human activities, that may cause loss of
life, injury, illness or other health impacts, property damage, loss of
livelihoods and services, social and economic disruption or
environmental damage is known as technological hazard. Examples of
technological hazards include industrial pollution, nuclear radiation, toxic
wastes, dam failures, transport accidents, factory explosions, fires and
chemical spills. Technological hazards also may arise directly as a result
of the impacts of a natural hazard event.
. Technological Potential: The amount by which it is possible to reduce
greenhouse gas emissions or improve energy efficiency by implementing
a technology or practice that has already been demonstrated is known
as technological potential.
. Technology Additionality: If the technology used for the project
activity will be the best available for the circumstances of the host party
then it is known as technology additionality.
. Technology Transfer: The broad set of processes that cover the
exchange of knowledge, money, and goods among different
stakeholders that lead to the spreading of technology for adapting to or
mitigating Climate Change is known as technology transfer. As a generic
concept, the term is used to encompass both diffusion of technologies
and technological cooperation across and within countries.
. Temperature: Temperature is a physical property of matter that
quantitatively expresses the common notions of hot and cold. Objects
of low temperature are cold, while various degrees of higher
temperatures are referred to as warm or hot. Quantitatively,
temperature is measured with thermometers which may be calibrated to
a variety of temperature scales.

. Temporal Scale: Climate may vary on a large range of scales, which
may range from seasonal to geological (up to hundreds of millions of
years) is know as temporal scale.
. The Himalayas: It is the highest mountain range in the world which
supplies fresh water to millions of people in Asia through its eight rivers
(Ganges, Brahmaputra, Indus, Irrawardy, Salween, Mekong, Yellow
river and Yangtze) is known as Himalayas.
. Third Assessment Report: The third extensive review of global
scientific research on Climate Change, published by the IPCC in 2001
is known as third assessment report.
. Threatened Species: Threatened species are any species (including
animals, plants, fungi, etc.) which are vulnerable to endangerment in the
near future.
. Threshold: The level of magnitude of a system process at which
sudden or rapid change occurs is known as threshold. A point or level at
which new properties emerge in an ecological, economic or other
system, invalidating predictions based on mathematical relationships that
apply at lower levels.
. Thunderstorm: A thunderstorm, also known as an electrical storm, a
lightning storm, thundershower or simply a storm is a form of weather
characterized by the presence of lightning and its acoustic effect on the
Earth’s atmosphere known as thunder.
. Tier: One of a series of rows placed one above another is known as
tier.
. Traditional People: People, communities, and nations who are native
to a particular area is known as traditional people.
. Transhumance: Seasonal movement of people with their livestock over
relatively short distances, typically to higher pastures in summer and to
lower valleys in winter is known as transhumance.
. Transient Climate Experiment: If the forcing is allowed to evolve
gradually according to a prescribed emission scenario, the

time-dependent response of a climate model may be analyzed. Such an
experiment is called a “transient climate experiment.”
. Transient Climate Response: The globally averaged surface air
temperature increase, averaged over a 20 year period, centered at the
time of CO2 doubling (i.e. at year 70 in a 1% per year compound CO2
increase experiment with a global coupled climate model).
. Tree line: The tree line is the edge of the habitat at which trees are
capable of growing. Beyond the tree line, they are unable to grow
because of inappropriate environmental conditions (usually cold
temperatures, insufficient air pressure or lack of moisture).
. Tree Outside Forest: Trees outside the forest are defined by default,
as all trees excluded from the definition of forest and other wooded
lands. Trees outside the forest are located on “other lands”, mostly on
farmlands and built-up areas both in rural and urban areas.
. Trend: Pattern of gradual change in a condition, output, or process or
an average or general tendency of a series of data points to move in a
certain direction over time, represented by a line or curve on a graph.
. Tribal People: A tribe viewed historically or developmentally, consists
of a social group existing before the development of or outside of states
is known as tribal people.
. Tribal Society: Societies organized largely on the basis of kinship,
especially corporate descent groups is known as tribal society.
. Troposphere: The lowest part of the atmosphere from the surface to
about 10 km in altitude in mid-latitudes (ranging from 9 km in high
latitudes to 16 km in the tropics on average) where clouds and “weather”
phenomena occur. In the troposphere, temperatures generally decrease
with height.
. Tropospheric Ozone: Ozone created in both naturally and by
photochemical reactions involving gases resulting from human activities
(photochemical “smog”) is known as troposhperic ozone. In high
concentrations, tropospheric ozone can be harmful to a wide-range of
living organisms. Tropospheric ozone acts as a greenhouse gas.

U
. Umbrella Group: A loose coalition of non European Union developed
countries formed following the adoption of the Kyoto Protocol is known
as umbrella group. Although there is no formal membership list, the group
usually includes Australia, Canada, Iceland, Japan, New Zealand,
Norway, the Russian Federation, Ukraine and the United States.
. United Nations Framework Convention on Climate Change
(UNFCCC): The Convention was adopted on 9 May 1992 in New
York and signed at the 1992 Earth Summit in Rio de Janeiro by more
than 150 countries and the European Community. Its ultimate objective
is the “stabilization of greenhouse gas concentrations in the atmosphere
at a level that would prevent dangerous anthropogenic interference with
the climate system.” It contains commitments for all Parties. Under the
Convention, Parties included in Annex I aim to return greenhouse gas
emissions not controlled by the Montreal Protocol to 1990 levels by the
year 2000. The Convention entered into force in March 1994. See also
Kyoto Protocol and Conference of the Parties (COP).
. UN REDD Programme: The UN-REDD Programme is the United
Nations collaborative initiative on Reducing Emissions from
Deforestation and forest Degradation (REDD) in developing countries.
The Programme was created in response to the UNFCCC decision on
REDD at COP 13 and the Bali Action Plan, and builds on the convening
power and expertise of the Food and Agriculture Organization of the
United Nations (FAO), the United Nations Development Programme
(UNDP) and the United Nations Environment Programme (UNEP).
The UN-REDD Programme supports nationally-led REDD+ processes
and promotes the informed and meaningful involvement of all
stakeholders, including indigenous peoples and other forest-dependent
communities, in national and international REDD+ implementation.
. Uncertainty: An expression of the degree to which a value (e.g. the
future state of the climate system) is unknown is known as uncertainty.
Uncertainty can result from lack of information or from disagreement
about what is known or even knowable. It may have many types of
sources, from quantifiable errors in the data to ambiguously defined
concepts or terminology or uncertain projections of human behavior.

Uncertainty can therefore be represented by quantitative measures (e.g.
a range of values calculated by various models) or by qualitative
statements (e.g. reflecting the judgment of a team of experts).
. Uniform Approach: Conforming to one principle, standard or rule;
consistent is known as uniform approach. It seeks to develop and
assess broad adaptation strategies on the basis of a comprehensive
perception of vulnerability that may exist. (e.g. across sectors, across
regions and across development challenges).
. Uniform Report Format: A standard format through which parties
submit information on activities implemented jointly under the
convention is known as uniform report format.
. Unique and Threatened System: Entities that are confined to a
relatively narrow geographical range but can affect other, often larger
entities beyond their range; narrow geographical range points to
sensitivity to environmental variables, including climate, and therefore
attests to potential vulnerability to Climate Change is known as unique
and threatened system.

V
. Validation: Something, such as a certificate, that validates something.
Attestation, authentication, confirmation, proof or verification is known
as validation.
. Vector: An organism, such as an insect, that transmits a pathogen from
one host to another is known as vector.
. Vector-borne Disease: Disease that is transmitted between hosts by a
vector organism such as a mosquito or tick (e.g. malaria, dengue fever
and leishmaniasis) is known as vector borne disease.
. Vegetation Type: Vegetation is a general term for the plant life of a
region. It refers to the ground cover provided by plants. It is a general
term, without specific reference to particular tax, life forms, structure,
spatial extent, or any other specific botanical or geographic
characteristics. It is broader than the term flora which refers exclusively
to species composition. Perhaps the closest synonym is plant
community but vegetation can and often does refer to a wider range of
spatial scales than that term does, including scales as large as the global.
. Voluntary Agreements: An agreement between a government
authority and one or more private parties as well as a unilateral
commitment that is recognized by the public authority to achieve
environmental objectives or to improve environmental performance
beyond compliance is known as voluntary agreement.
. Voluntary Carbon Offset Mechanism: These mechanisms are based
on the notion that greenhouse gases produce the same effect on the
climate wherever they are emitted from and that if in certain conditions it
proves impossible to reduce emissions linked to one’s own activities, in
theory enabling emissions to be cut elsewhere will have the same end
result. For example, companies buy a “CO2 credit” by financing a project
in a developing country (or an emerging economy) that will allow the
same amount of CO2 to be saved; or else they go onto the market and
buy carbon credits generated by actions that enabled emissions to be
avoided or credits resulting from quota surpluses. Industries can,
however, help to reduce global greenhouse emissions by means of a
voluntary carbon offset mechanism.

. Voluntary Carbon Standard: The Voluntary Carbon Standard (VCS)
is a quality standard for voluntary carbon offset industry. Based on the
Kyoto Protocol’s Clean Development Mechanism, VCS establishes
criteria for validating, measuring, and monitoring carbon offset projects
. Voluntary Commitments: A draft article considered during the
negotiation of the Kyoto Protocol that would have permitted developing
countries to voluntarily adhere to legally binding emissions targets is
known as voluntary commitments.
. Voluntary Emission Reduction: Voluntary Emission Reductions or
Verified Emission Reductions (VERs) are a type of carbon offset
exchanged in the voluntary or ‘Over-the-Counter’ (OTC) market for
carbon credits . Verified Emission Reductions are usually certified through
a voluntary certification process. Verified Emission Reductions are
usually created by projects which have been verified outside of the Kyoto
Protocol. One VER is equivalent to one metric ton of CO2 emissions.
Through these schemes, industries and individuals voluntarily
compensate for their emissions or provide an additional contribution to
mitigating Climate Change.
. Vulnerability: Vulnerability is a set of conditions and processes
resulting from physical, social, economic, and environmental factors,
which increase the likelihood that a community will negatively affected
by a climate hazard or change. It is a combination of exposure to
climatic conditions, how sensitive the community is to those conditions,
and the capacity to adapt to those changes, geographical, climatic,
social, economic, physical, environmental, development related. The
degree to which a system is susceptible to or unable to cope with
adverse effects of Climate Change, including climate variability and
extremes. Vulnerability is a function of the character, magnitude and rate
of climate variation to which a system is exposed, its sensitivity, and its
adaptive capacity. It is dependent on a wide variety of institutional,
economic and environmental factors, not all of which are linked directly
with the climate.
. Vulnerability Assessment: Vulnerability Assessment identifies who and
what is exposed and sensitive to change is known as vulnerability
assessment. A vulnerability assessment starts by considering the factors
that make people or the environment susceptible to harm, i.e. access to

natural and financial resources; ability to self-protect; support networks
and so on. Assessment of vulnerability to Climate Change mainly
involves research into the exposure, sensitivity and adaptive capacity
levels of a system in the presence of a specific impact, for example,
rising frequency of floods. The governing factors of vulnerability
assessment studies mainly include scale of assessment, the kind of
impact or hazard being considered and the target group or system being
assessed.
. Vulnerability Context: Assessing local context during livelihood analysis
is vulnerability context. The poor are constantly insecure but there are
certain factors and trends that can make their insecurity much deeper.
Vulnerability assessment involves an analysis of factors and long-term
trends. Many of these factors come from several levels away from the
immediate environment.
. Vulnerability to Climate Change: The characteristics of a system
which cause it to suffer a definite degradation (incapability to perform
the designated mission) as a result of having been subjected to a certain
level of effects in an unnatural (manmade) hostile environment is known
as vulnerability to climate change.
. Vulnerable: Liable to injury; subject to be affected injuriously is known
as vulnerable or exposed to the possibility of being attacked or harmed,
either physically or emotionally.
. Vulnerable Communities: People with special needs include
members of the community with little or no ability to successfully
address, implement or be fully responsible for their own emergency
preparedness, response or recovery is known as vulnerable
communities. This includes people whose life circumstances leave them
unable or unwilling to follow emergency instruction as well as anyone
unable or unwilling to fully access or use preparedness and responsive
services.
. Vulnerable Groups: The definition of vulnerable groups varies between
countries, but amongst the most important defining characteristics are
age, sex, ethnicity and location. But also important are people with
disabilities and stigmatized illnesses such as mental ill-health. In areas
facing war or civil conflicts displaced people and refugees form an
important vulnerable group.

W
. Water: Water is a chemical substance with the chemical formula H2O.
Its molecule contains one oxygen and two hydrogen atoms connected
by covalent bonds. Water is a liquid at ambient conditions, but it often
co-exists on Earth with its solid state, ice and gaseous state (water
vapor).
. Water Borne Disease: Waterborne diseases are caused by
pathogenic microorganisms which are directly transmitted when
contaminated fresh water is consumed. Contaminated fresh water used
in the preparation of food can be the source of food borne disease
through consumption of the same microorganisms.
. Water Pollution: The contamination of water bodies (e.g. lakes, rivers,
oceans and groundwater) is known as water pollution. Water pollution
occurs when pollutants are discharged directly or indirectly into water
bodies without adequate treatment to remove harmful compounds.
. Water Stress: A country is water-stressed if the available freshwater
supply relative to water withdrawals acts as an important constraint on
development. Withdrawals exceeding 20% of renewable water supply
has been used as an indicator of water stress.
. Water Use Efficiency: Carbon gain in photosynthesis per unit water
lost in evapotranspiration is known as water use efficiency. It can be
expressed on a short-term basis as the ratio of photosynthetic carbon
gain per unit transpirational water loss, or on a seasonal basis as the
ratio of net primary production or agricultural yield to the amount of
available water.
. Weather: The behavior of the atmosphere on a day-to-day basis in a
relatively local area is known as weather. A description of the weather
would include daily temperatures, relative humidity, sunshine, wind and
rainfall.
. Weather Forecast: The application of science and technology to
predict the state of the atmosphere or a future time and a given location
is known as weather forecast. Human beings have attempted to predict

the weather informally for millennia, and formally since at least the
nineteenth century. Weather forecasts are made by collecting
quantitative data about the current state of the atmosphere and using
scientific understanding of atmospheric processes to project how the
atmosphere will evolve.
. Wind: Wind is the flow of gases on a large scale. On Earth, wind
consists of the bulk movement of air.
. Wind Erosion: Erosion is the process of weathering and transport of
solids (sediment, soil, rock and other particles) in the natural
environment or their source and deposits them elsewhere. When it
occurs due to transport by wind is called wind erosion.
. Winter: Winter is the coldest season of the year in temperate climates,
between autumn and spring. At the winter solstice, the days are shortest
and the nights are longest, with days lengthening as the season progresses
after the solstice.
. WRE Profiles: The carbon dioxide concentration profiles leading to
stabilization defined by Wigley, Richels, and Edmonds (1996) whose
initials provide the acronym is known as WRE profiles. For any given
stabilization level, these profiles span a wide range of possibilities.

Z
. Zoning: Zoning is a device of land use planning used by local
governments in most developed countries. The word is derived from the
practice of designating permitted uses of land based on mapped zones
which separate one set of land uses from another. Zoning may be
use-based (regulating the uses to which land may be put) or it may
regulate building height, lot coverage and similar characteristics or some
combination of these.
 	
Glossary

Glossary of climate change acronyms and jargon

 

Negotiators at the climate change meetings rely on an extensive vocabulary of acronyms and technical jargon. Here are some of the most important.

I) The Players

 

Ad hoc Group on Article 13 (AG13) - A subsidiary body (committee) created by COP-1 to explore how to help governments overcome difficulties they may experience in meeting their commitments.

Ad hoc Group on the Berlin Mandate (AGBM) - A subsidiary body created by COP-1 to conduct the talks that led to the adoption of the Kyoto Protocol; the AGBM concluded its final meeting on 30 November 1997.

Annex I Parties - The industrialized countries listed in this annex to the Convention are trying to return their greenhouse gas emissions to 1990 levels by the year 2000 as per Article 4.2(a) and (b). They have also accepted emission targets for the period 2008-12 as per Article 3 and Annex B of the Kyoto Protocol. They include the 24 original OECD members, the European Union, and 14 countries with economies in transition (Croatia, Liechtenstein, Monaco and Slovenia joined at COP-3, and the Czech Republic and Slovakia replaced Czechoslovakia).

Annex II Parties - The rich countries listed in this annex to the Convention have a special obligation to help developing countries with financial and technological resources. They include the 24 original OECD members plus the European Union.

AOSIS - The Alliance of Small Island States is an ad hoc coalition of low-lying and island countries. These countries are particularly vulnerable to sea-level rise and share common positions on climate change. The 42 members and observers are American Samoa, Antigua and Barbuda, Bahamas, Barbados, Belize, Cape Verde, Comoros, Cook Islands, Cuba, Cyprus, Dominica, Federated States of Micronesia, Fiji, Grenada, Guam, Guinea-Bissau, Guyana, Jamaica, Kiribati, Maldives, Malta, Marshall Islands, Mauritius, Nauru, Netherlands Antilles, Niue, Palau, Papua New Guinea, Samoa, Sao Tome and Principe, Seychelles, Singapore, Solomon Islands, St. Kitts & Nevis, St. Lucia, St. Vincent and the Grenadines, Suriname, Tonga, Trinidad and Tobago, Tuvalu, US Virgin Islands, and Vanuatu.

Bureau - Responsible for directing the work of the COP. Its 10 members are delegates elected by each of the five regional groups and they include the COP President, six Vice Presidents, the Chairs of SBI and SBSTA, and a rapporteur. In addition, each subsidiary body also has its own Bureau.

Chair (or chairman etc.) - The participating governments elect a Chair for the subsidiary bodies from amongst the delegates. Different Chairs may be elected for other informal groups. The Chair is responsible for facilitating progress towards an agreement and serves during the inter-sessional period until the start of the next COP.

Committee of the Whole - Often created by a COP to facilitate the process of negotiating text. When the Committee finishes its work it turns the text over to the COP which finalizes and then formally adopts it during a plenary session.

Conference of the Parties (COP) - The COP is the supreme body of the Convention. It currently meets once a year to review the Convention's progress. The word "conference" is not used here in the sense of "meeting" but rather of "association", which explains the seemingly redundant expression "fourth session of the Conference of the Parties".

COP/MOP - The Kyoto Protocol's supreme body will be the COP, which will serve as the Protocol's meeting of the Parties. The sessions of the COP and the COP/MOP will be held during the same period. This will improve cost-effectiveness and coordination with the Convention.

countries with economies in transition (EIT) - Those Central and East European countries and former republics of the Soviet Union that are in transition to a market economy.

European Union (EU) - As a regional economic integration organization, the European Union can be and is a Party to the Convention; however, it does not have a separate vote from its members. The EU can also be a Party to the Protocol. Because it signed the Convention when it was known as the EEC, it retains this name for all formal Convention-related purposes. Its members are Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, the Netherlands, Portugal, Spain, Sweden, and the UK.

friends of the chair - Delegates who are called upon by the Chair (who takes into account the need for a political balance among various interests) to assist in carrying out specific tasks.

Group of 77 and China - The G-77 was founded in 1967 under the auspices of the United Nations Conference for Trade and Development (UNCTAD). It seeks to harmonize the negotiating positions of its 132 developing-country members.

Global Environment Facility (GEF) - The multi-billion-dollar GEF was established by the World Bank, the UN Development Programme, and the UN Environment Programme in 1990. It operates the Convention's "financial mechanism" on an interim basis and funds developing country projects that have global climate change benefits.

Intergovernmental Negotiating Committee (INC) - The INC met during five sessions between February 1991 and May 1992 to draft the Convention; it met six more times to prepare for COP-1 before completing its work in February 1995.

Intergovernmental Panel on Climate Change (IPCC) - The IPCC was established in 1988 by the World Meteorological Organization and the UN Environment Programme. It conducts rigorous surveys of the world-wide technical and scientific literature and publishes assessment reports that are widely recognized as the most credible existing sources of information on climate change. The IPCC also works on methodologies and responds to specific requests from the Convention's subsidiary bodies.

JUSSCANNZ - The non-EU industrialized countries meet as a group to discuss various issues; they are Japan, the US, Switzerland, Canada, Australia, Norway, and New Zealand. Iceland, Mexico, and the Republic of Korea may also attend meetings.

national delegation - One or more officials who are empowered to represent and negotiate on behalf of their government.

non-governmental organizations (NGOs) - Many relevant NGOs attend the climate talks as observers in order to interact with delegates and the press and provide information. NGOs must be non-profit and can include environmental groups, research institutions, business groups, and associations of urban and local governments.

non-Party - A state that has not ratified the Convention may attend talks as an observer.

observer - The COP and its subsidiary bodies normally permit observers to attend their sessions. Observers may include the United Nations and its specialized agencies, the International Atomic Energy Agency, non-Party states, and other relevant governmental or non-governmental organizations.

OECD - The Organization for Economic Cooperation and Development consists of Australia, Austria, Belgium, Canada, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Republic of Korea, Japan, Luxembourg, Mexico, the Netherlands, New Zealand, Norway, Poland, Portugal, Spain, Sweden, Switzerland, Turkey, the UK, and the US.

Party - A state (or regional economic integration organization such as the EU) that agrees to be bound by a treaty and for which the treaty has entered into force.

President - Elected by the Parties to preside over the COP, the President is often a senior official or minister from the state or region hosting the meeting.

regional groups - The five regional groups meet privately to discuss issues and nominate bureau members and other officials. They are Africa, Asia, Central and Eastern Europe (CEE), Latin America and the Caribbean (GRULAC), and the Western Europe and Others Group (WEOG).

secretariat - Staffed by international civil servants and responsible for servicing the COP and ensuring its smooth operation, the secretariat makes arrangements for meetings, compiles and prepares reports, and coordinates with other relevant international bodies. The Climate Change secretariat is institutionally linked to the United Nations.

subsidiary body - A committee that assists the Conference of the Parties. Two permanent ones are defined by the Convention: the Subsidiary Body for Implementation and the Subsidiary Body for Scientific and Technological Advice. COP-1 also established two other temporary bodies: the Ad hoc Group on the Berlin Mandate, which concluded its work on 30 November 1997, and the Ad hoc Group on Article 13. Additional subsidiary bodies may be established as needed.

Subsidiary Body for Implementation (SBI) - Makes recommendations on policy and implementation issues to the COP and, if requested, other bodies.

Subsidiary Body for Scientific and Technological Advice (SBSTA) - Serves as the link between the information and assessments provided by expert sources (such as the IPCC) on the one hand, and the policy-oriented needs of the COP on the other.

II) The action (meetings, documents, process)

agenda - A programme of work that the delegates adopt and are guided by; the annotated agenda contains a more detailed explanation of each agenda item.

amendment - The COP can change the existing Convention text through consensus or, if consensus cannot be reached, by a three-quarters majority vote by all Parties present and voting.

Berlin Mandate - Adopted at COP-1, the Berlin Mandate launched the talks that led to the adoption of the Kyoto Protocol.

consensus - An agreement can be adopted by consensus rather than by a vote when there are no stated objections from delegations.

contact group - The COP or the Committee of the Whole may establish an open-ended meeting wherein Parties can negotiate before forwarding agreed text to the plenary for formal adoption. Observers can generally attend.

COP sessions - The first session of the Conference of the Parties (COP-1) was held in Berlin from 28 March to 7 April 1995, the second (COP-2) in Geneva from 8 - 19 July 1996, the third (COP-3) in Kyoto from 1 -11 December 1997, and the fourth (COP-4) is being held in Buenos Aires from 2 - 13 November 1998.

Conference Room Papers (CRPs) - A category of in-session documents containing new proposals or outcomes of in-session work for use only during the session.

declaration - A non-binding political statement made by ministers attending a major meeting (e.g. the Geneva Ministerial Declaration at COP-2).

decision - Unlike a resolution, a decision is a formal agreement and leads to binding actions. It becomes part of the agreed body of decisions that direct the work of the COP.

documents - Official meeting documents are available to everyone and feature the logos of the United Nations and the Climate Change Convention and a reference number, such as FCCC/CP/1998/1. Pre-session documents are available before the meeting, often in all six UN languages. In-session documents are distributed on-site (see CRPs, L docs, Misc. docs, and nonpapers). Informal documents are often distributed outside the meeting room by observers.

drafting groups - To facilitate negotiations, the President or the Chair may establish smaller drafting groups to meet separately and in private to prepare text. Observers generally may not attend.

entry into force - Intergovernmental agreements, including protocols and amendments, are not legally binding until they have been ratified by a certain number of countries; the Climate Change Convention required 50 and enters into force for each new Party 90 days after it ratifies.

informal contact group - On the instructions of the President or Chair, delegates may meet in private to discuss specific matters in order to consolidate different views, reach a compromise, and produce an agreed proposal, often in the form of a written text.

L. docs - In-session documents that contain draft reports and texts for adoption by the COP or the subsidiary bodies, usually in all 6 UN languages.

meetings vs. sessions - Each session of the COP is divided into a number of meetings. Each meeting is generally scheduled from 10 a.m. to 1 p.m. or from 3 p.m. to 6 p.m., so that the morning of 2 November will be the first meeting of the fourth session of the COP.

misc. docs - Miscellaneous documents are issued on plain paper with no UN masthead; they generally contain views or comments submitted as received from a delegation without formal editing.

nonpapers - In-session documents issued informally to facilitate negotiations; they do not have an official document symbol although they may have an identifying number or the name of the authors.

plenary - A meeting of the entire COP where all formal decisions are taken.

protocol - A protocol is linked to an existing convention, but it is a separate and additional agreement that must be signed and ratified by the Parties to the convention. Protocols typically strengthen a convention by adding new, more detailed commitments.

ratification - After signing the Convention or the Protocol, a country must ratify it, often with the approval of its parliament or other legislature. The instrument of ratification must be deposited with the depositary (in this case the UN Secretary-General) to start the 90-day countdown to becoming a Party.

recommendation - Weaker than a decision or a resolution and not binding on Parties.

reservation - A Party may accept a decision of the COP while noting its reservations and concerns for the record. However, no reservations may be made to the Convention itself or to the Protocol.

resolution - Unlike decisions, resolutions do not generally become part of the formal body of decisions that guide the work of the COP. They are directives that guide, opinions rather than permanent legal acts.

rules of procedure - The rules that govern the proceedings of the COP, including the procedures for decision-making and participation. The COP has not yet adopted the rules and all expect one (on voting) are currently being "applied".

Second Assessment Report (SAR) - Also known as Climate Change 1995, the IPCC's SAR was written and reviewed by some 2,000 scientists and experts world-wide. It concluded that "the balance of evidence suggests that there is a discernible human influence on global climate" and confirmed the availability of "no-regrets" options and other cost-effective strategies for combating climate change.

signature - The head of state or government, the foreign minister, or another designated official indicates his or her country's agreement with the adopted text of the Convention or the Protocol and its intention to become a Party by signing.

square brackets - Used during negotiations to indicate that a section of text is being discussed but has not yet been agreed.

Third Assessment Report (TAR) - The IPCC's Third Assessment Report is expected to be finalized in late 2000 and published in early 2001.

III) The issues

activities implemented jointly (AIJ) - Under a pilot phase that ends by 2000, AIJ activities can be carried out through partnerships between an investor from a developed country and a counterpart in a host country. The purpose is to involve private-sector money in the transfer of technology and know-how. See also Joint Implementation.

Article 4.1 - This Convention article contains general commitments for all Parties - developing and developed.

Article 4.2 - This Convention article contains specific commitments for developed country (Annex I) Parties only, notably to take measures aimed at returning greenhouse gas emissions to 1990 levels by the year 2000.

clean development mechanism (CDM) - The Kyoto Protocol establishes the CDM to enable industrialized countries to finance emissions-avoiding projects in developing countries and receive credit for doing so.

emissions trading - The Kyoto Protocol establishes a mechanism whereby Parties with emissions commitments may trade their emission allowances with other Parties. The aim is to improve the overall flexibility and economic efficiency of making emissions cuts.

financial mechanism - As defined by the Convention, its role is to transfer funds and technologies to developing countries on a grant or consessional basis, under the guidance of the COP. The Global Environment Facility is "operating" the mechanism on an interim basis.

greenhouse gases (GHGs) - The major GHGs responsible for causing climate change are carbon dioxide (CO2), methane (CH4), and nitrous oxide (N20). The Kyoto Protocol also addresses hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6).

"hot air" - Refers to the concern that some governments will be able to meet their commitment targets with minimal effort and could then flood the market for emissions credits, reducing the incentive for other countries to cut their own domestic emissions.

in-depth review (IDR) - The first submissions of national communications by developed countries were subjected to a series of in-depth reviews generally involving country visits by international teams of experts.

joint implementation (JI) - The Kyoto Protocol establishes a mechanism whereby a developed country can receive "emissions reduction units" when it helps to finance projects that reduce net emissions in another developed country (including countries with economies in transition). Some aspects of this approach are being tested as Activities Implemented Jointly (see AIJ).

mechanisms - The Kyoto Protocol establishes three mechanisms to increase the flexibility and reduce the costs of making emissions cuts; these are the Clean Development Mechanism, emissions trading, and joint implementation.

national communications - A central requirement of the Convention (and the Protocol) is that each Party must inform the others about its national climate change activities. Many developed countries have submitted their second reports and developing countries have started to submit their first.

policies and measures - Countries must decide what policies and measures to adopt in order to achieve their emissions targets. Some possible policies and measures which Parties could implement are listed in the Kyoto Protocol and could offer opportunities for intergovernmental cooperation.

Quantified Emissions Limitation and Reduction Commitments - Legally-binding targets and timetables under the Kyoto Protocol for the limitation or reduction of greenhouse gas emissions for developed countries.

review of commitments - The Parties must regularly review the adequacy of the Convention's Article 4.2 (a) and (b) outlining developed country commitments to limit emissions. The first review took place at COP-1 and led to the Berlin Mandate and the adoption of the Kyoto Protocol. The second review is to take place in Buenos Aires.

sinks - Under the Kyoto Protocol, developed countries can include changes in net emissions (calculated as emissions minus removals of CO2) from certain activities in the land-use change and forestry sector. Calculating the effects of sinks (growing vegetation tends to absorb carbon dioxide from the atmosphere) is methodologically complex and still needs to be clarified.

voluntary commitments - During the Kyoto negotiations, a draft article that would have permitted developing countries to voluntary adhere to legally binding emissions targets was dropped in the final hours. This issue remains important for some negotiators and may be discussed in Buenos Aires.

 AAU
Assigned amount unit. A Kyoto Protocol unit equal to 1 metric tonne of CO2 equivalent. Each Annex I Party issues AAUs up to the level of its assigned amount, established pursuant to Article 3, paragraphs 7 and 8, of the Kyoto Protocol. Assigned amount units may be exchanged through emissions trading.

Abatement
Refers to reducing the degree or intensity of greenhouse-gas emissions.

AC
Adaptation Committee. The Adaptation Committee was established by the Conference of the Parties as part of the Cancun Agreements to promote the implementation of enhanced action on adaptation in a coherent manner under the Convention, inter alia, through various functions. More information available here.

Accession
An act whereby a State becomes a Party to a treaty already negotiated and signed by other States; has the same legal effect as ratification.

Adaptation
Adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects, which moderates harm or exploits beneficial opportunities.

Adaptation Fund
The Adaptation Fund was established to finance concrete adaptation projects and programmes in developing countries that are particularly vulnerable and are Parties to the Kyoto Protocol. The Fund is to be financed with a share of proceeds from clean development mechanism (CDM) project activities and receive funds from other sources. It is operated by the Adaptation Fund Board. More information available here.

ADP
Ad hoc Working Group on the Durban Platform for Enhanced Action. The ADP is a subsidiary body established at COP 17 in Durban in 2011 to develop a protocol, another legal instrument or an agreed outcome with legal force under the Convention applicable to all Parties. The ADP is to complete its work by 2015 in order to adopt this protocol, legal instrument or agreed outcome with legal force at the twenty-first session of the COP and for it to come into effect from 2020. More information here.

Afforestation
Planting of new forests on lands that historically have not contained forests.

AG13
Ad hoc Group on Article 13. A subsidiary body (committee) created by COP-1 to explore how to help governments overcome difficulties experienced in meeting their commitments under the Climate Change Convention (1995-1998).

AGBM
Ad hoc Group on the Berlin Mandate. A subsidiary body created by COP-1 to conduct the talks that led to the adoption of the Kyoto Protocol. The AGBM concluded its work on 30 November 1997.

AIJ
Activities implemented jointly. Activities carried out under the Convention to mitigate climate change through partnerships between an investor from a developed country and a counterpart in a host country under a pilot phase that ended in the year 2000. The purpose was to involve private-sector money in the transfer of technology and know-how. See also JI - Joint Implementation

Amendment
A modification by the COP to the text of the Convention. If consensus cannot be reached, an amendment must win three-quarters of the votes of all Parties present and casting ballots.

Annex I Parties
The industrialized countries listed in Annex I to the Convention, which committed to returning their greenhouse-gas emissions to 1990 levels by the year 2000 as per Article 4.2 (a) and (b). They have also accepted emissions targets for the period 2008-12 as per Article 3 and Annex B of the Kyoto Protocol. They include the 24 original OECD members, the European Union, and 14 countries with economies in transition. (Croatia, Liechtenstein, Monaco, and Slovenia joined Annex 1 at COP-3, and the Czech Republic and Slovakia replaced Czechoslovakia.) List of Parties to the Convention can be found here.

Annex II Parties
The countries listed in Annex II to the Convention which have a special obligation to provide financial resources and facilitate technology transfer to developing countries. Annex II Parties include the 24 original OECD members plus the European Union. List of Parties to the Convention can be found here.

Anthropogenic greenhouse emissions
Greenhouse-gas emissions resulting from human activities.

AOSIS
Alliance of Small Island States. An ad hoc coalition of low-lying and island countries. These nations are particularly vulnerable to rising sea levels and share common positions on climate change. The 43 members and observers are American Samoa, Antigua and Barbuda, Bahamas, Barbados, Belize, Cape Verde, Comoros, Cook Islands, Cuba, Dominica, Dominican Republic, Federated States of Micronesia, Fiji, Grenada, Guam, Guinea-Bissau, Guyana, Haiti, Jamaica, Kiribati, Maldives, Marshall Islands, Mauritius, Nauru, Netherlands Antilles, Niue, Palau, Papua New Guinea, Samoa, Sao Tome and Principe, Seychelles, Singapore, Solomon Islands, St. Kitts & Nevis, St. Lucia, St. Vincent and the Grenadines, Suriname, Timor-Leste, Tonga, Trinidad and Tobago, Tuvalu, US Virgin Islands, and Vanuatu.

APA
Ad Hoc Working Group on the Paris Agreement. The APA was established to prepare for the entry into force of the Paris Agreement and for the convening of the first session of the Conference of the Parties serving as the meeting of the Parties to the Paris Agreement (CMA). More information here. 

Article 4.1
An article of the Convention stipulating general commitments assumed by all Parties, developing or developed.

Article 4.2
An article of the Convention stating the specific commitments of developed-country (Annex I) Parties only -- notably that they would take measures aimed at returning greenhouse-gas emissions to 1990 levels by the year 2000.

Article 6 Supervisory Committee
A committee providing international oversight of "track-two" joint implementation projects. Joint implementation projects are carried out by sponsoring and recipient developed countries under Article 6 of the Kyoto Protocol -- with the recipient likely to be a country with an "economy in transition". Track-two is used if one or both of the countries does not meet requirements for the standard ("track one") joint implementation programme. See track two.

AWG-KP
Ad hoc Working Group on further commitments for Annex I Parties under the Kyoto Protocol. The AWG-KP was established in 2005 by Parties to the Kyoto Protocol in Montreal to consider further commitments of industrialized countries under the Kyoto Protocol for the period beyond 2012. More information here. 

AWG-LCA
Ad hoc Working Group on Long-term Cooperative Action under the Convention. The AWG-LCA was established in Bali in 2007 to conduct negotiations on a strengthened international deal on climate change. More information here.
B

BAP
Bali Action Plan. Included in the Bali Road Map, agreed at the Conference of the Parties in Bali, Indonesia in 2007 (COP13), introduced AWG-LCA.

Bali Road Map
The Bali Road Map was adopted at the 13th Conference of the Parties and the 3rd Meeting of the Parties in December 2007 in Bali. The Road Map is a set of a forward-looking decisions that represent the work that needs to be done under various negotiating "tracks" that is essential to reaching a secure climate future. It includes the Bali Action Plan, which charts the course for a new negotiating process designed to tackle climate change, with the aim of completing this by 2009. It also includes the AWG-KP negotiations, the launch of the Adaptation Fund, the scope and content of the Article 9 review of the Kyoto Protocol, as well as decisions on technology transfer and on reducing emissions from deforestation.

Berlin Mandate
Adopted at COP-1, the mandate that launched negotiations leading to the adoption of the Kyoto Protocol.

BINGO
Business and industry non-governmental organisations.

Biomass fuels or biofuels
A fuel produced from dry organic matter or combustible oils produced by plants.
These fuels are considered renewable as long as the vegetation producing them is maintained or replanted, such as firewood, alcohol fermented from sugar, and combustible oils extracted from soy beans. Their use in place of fossil fuels cuts greenhouse gas emissions because the plants that are the fuel sources capture carbon dioxide from the atmosphere.

Bonn agreements
Informal term for a political deal reached at COP-6 in Bonn, Germany, in 2001, by which governments agreed on the most politically controversial issues under the Buenos Aires Plan of Action. The Bonn agreements paved the way for the Marrakech Accords later in the same year.

Bonn fund
A special UNFCCC fund for contributions from the Government of Germany to cover costs of UNFCCC events held in Bonn.

Brazilian proposal
A proposal by the delegation of Brazil made in May 1997 as part of the negotiations on the Kyoto Protocol. It included a formula to set differentiated emission reduction targets for Parties based on the cumulative impact of Parties' historic emissions on the global average surface temperature.

Bunker fuels
A term used to refer to fuels consumed for international marine and air transport.

Bureau
A body responsible for directing the work of the COP. Its 10 members are delegates elected by each of five regional groups. The Bureau includes the COP President, six Vice Presidents, the Chairs of SBI and SBSTA, and a rapporteur. Each of the Convention's subsidiary bodies also has a Bureau.
C

CACAM
Negotiating coalition of countries of Central Asia and the Caucasus, Albania, and the Republic of Moldova.

Capacity building
In the context of climate change, the process of developing the technical skills and institutional capability in developing countries and economies in transition to enable them to address effectively the causes and results of climate change.

Carbon market
A popular (but misleading) term for a trading system through which countries may buy or sell units of greenhouse-gas emissions in an effort to meet their national limits on emissions, either under the Kyoto Protocol or under other agreements, such as that among member states of the European Union. The term comes from the fact that carbon dioxide is the predominant greenhouse gas, and other gases are measured in units called "carbon-dioxide equivalents."

Carbon sequestration
The process of removing carbon from the atmosphere and depositing it in a reservoir.

Cartagena Dialogue
A collection of around 40 countries working towards an ambitious legally binding agreement under the UNFCCC, and who are committed to becoming or remaining low carbon domestically. Participates include: Antigua & Barbuda, Australia, Bangladesh, Barbados, Burundi, Chile, Colombia, Costa Rica, Denmark, Dominican Republic, Ethiopia, European Union, France, Gambia, Georgia,  Germany, Ghana,  Grenada, Guatemala, Indonesia, Kenya, Lebanon, Malawi, Maldives, Marshall Islands, México, Netherlands, New Zealand, Norway, Panama, Peru, Rwanda, Samoa, Spain, Swaziland, Sweden, Switzerland, Tajikistan, Tanzania, Uganda, UAE, and the United Kingdom. 
  
CBD
Convention on Biological Diversity.

CC:TRAIN
Training methodology for assessing vulnerability to climate change.

CDM
Clean Development Mechanism. A mechanism under the Kyoto Protocol through which developed countries may finance greenhouse-gas emission reduction or removal projects in developing countries, and receive credits for doing so which they may apply towards meeting mandatory limits on their own emissions.

CDM Help Desk
A support initiative for project participants, developers, coordinating and/or managing entities (CMEs), designated national authorities (DNAs) and designated operational entities (DOEs) to get reliable and timely information from the secretariat on issues regarding their CDM projects. It is only available to stakeholders in Africa, least developed countries (LDCs), small island developing States (SIDS) and countries that had 10 or fewer registered CDM projects as of 31 December 2010, as long as the project is in the process of validation or verification.

CDM Loan Scheme
An interest-free, loan initiative that provides funding to projects for development of PDD, validation, and first verification. It applies to projects located in host countries with less than 10 CDM project activities registered with the UNFCCC (as of 1 January of the year of submission), with a high probability of registration with the UNFCCC and generating at least 7,500 CERs/year for projects in Least Developed Countries (LDCs), and 15,000 CERs/year in non-LDCs. More information here.

Central Group
Formerly CG-11, a negotiating coalition of Central European Annex I Parties, now called the Central Group.

Certified emission reductions (CER)
A Kyoto Protocol unit equal to 1 metric tonne of CO2 equivalent. CERs are issued for emission reductions from CDM project activities. Two special types of CERs called temporary certified emission reduction (tCERs) and long-term certified emission reductions (lCERs) are issued for emission removals from afforestation and reforestation CDM projects.

CFC
Chlorofluorocarbon.

CG-11
Central Group 11 (negotiating coalition of Central European Annex I parties).

CGE
Consultative Group of Experts on National Communications from non-Annex I Parties. A panel established to improve the preparation of national communications from developing countries. National communications are an obligation of Parties to the Climate Change Convention.

CH4
Methane.

Chair (or Chairman, Chairperson, etc.)
National delegates elected by participating governments to lead the deliberations of the Convention's subsidiary bodies. Different chairs may be elected for other informal groups. The Chair is responsible for facilitating progress towards an agreement and serves during the inter-sessional period until the next COP.

Clearing house
A service which facilitates and simplifies transactions among multiple parties.

CMA
Conference of the Parties serving as the meeting of the Parties to the Paris Agreement. All States that are Parties to the Paris Agreement are represented at the CMA, while States that are not Parties participate as observers. The CMA oversees the implementation of the Paris Agreement and takes decisions to promote its effective implementation. More information here.

CMS
Convention on the Conservation of Migratory Species of Wild Animals.

CMP
Conference of the Parties serving as the Meeting of the Parties to the Kyoto Protocol. The Convention's supreme body is the COP, which serves as the meeting of the Parties to the Kyoto Protocol. The sessions of the COP and the CMP are held during the same period to reduce costs and improve coordination between the Convention and the Protocol. More information here. 

CO2
Carbon dioxide.

Coalition for Rainforest Nations
A voluntary grouping of largely developing nations with rainforests which addresses issues surrounding environmental sustainability specific to tropical rainforests. Participation does not necessarily imply that countries adhere to any specific domestic policies or negotiating positions within the international context. At September 2011, the group included Argentina, Bangladesh, Belize, Cameroon, Central African Republic, Chile, Congo, Costa Rica, Cote d'Ivoire, DR Congo, Dominica, Dominican Republic, Ecuador, Equatorial Guinea, El Salvador, Fiji, Gabon, Ghana, Guatemala, Guyana, Honduras, Indonesia, Jamaica, Kenya, Lesotho, Liberia, Madagascar, Malaysia, Nicaragua, Nigeria, Pakistan, Panama, Papua New Guinea, Paraguay, Samoa, Sierra Leone, Solomon Islands, Suriname, Thailand, Uruguay, Uganda, Vanuatu and Vietnam. Countries participate on a voluntarily basis primarily through unified negotiating positions, workshops and collaborative programs. 

Committee of the Whole
Often created by a COP to aid in negotiating text. It consists of the same membership as the COP. When the Committee has finished its work, it turns the text over to the COP, which finalizes and then adopts the text during a plenary session.

Compliance Committee
A committee that helps facilitate, promote and enforce compliance with the provisions of the Kyoto Protocol. It has 20 members with representation spread among various regions, small-island developing states, Annex I parties and non-Annex I parties, and functions through a plenary, a bureau, a facilitative branch and an enforcement branch. More information here.

Compliance
Fulfilment by countries/businesses/individuals of emission reduction and reporting commitments under the UNFCCC and the Kyoto Protocol.

Contact group
An open-ended meeting that may be established by the COP, a subsidiary body or a Committee of the Whole wherein Parties may negotiate before forwarding agreed text to a plenary for formal adoption. Observers generally may attend contact group sessions.

COP
Conference of the Parties. The supreme body of the Convention. It currently meets once a year to review the Convention's progress. The word "conference" is not used here in the sense of "meeting" but rather of "association". The "Conference" meets in sessional periods, for example, the "fourth session of the Conference of the Parties." More information here. 

CRF
Common Reporting Format. Standardized format for reporting estimates of greenhouse-gas emissions and removals and other relevant information by Annex I Parties.

CRPs
Conference room papers. A category of in-session documents containing new proposals or outcomes of in-session work. CRPs are for use only during the session concerned.

CSD
United Nations Commission on Sustainable Development.
D

Declaration
A non-binding political statement made by ministers attending a major meeting (e.g. the Marrakesh Ministerial Declaration of COP-7).

Deforestation
Conversion of forest to non-forest.

Designated National Authority (DNA)
An office, ministry, or other official entity appointed by a Party to the Kyoto Protocol to review and give national approval to projects proposed under the Clean Development Mechanism. More information here.

DNA Help Desk
A support initiative for Designated National Authorities (DNAs) to provide advice, support and assistance with the submission of proposals for standardized baselines, recommendations of microscale renewable energy technologies for automatic additionality, or grid emission factors. It targets DNAs from least developed countries (LDCs), small island developing States (SIDS), African countries, or Parties with less than 10 registered projects as of 31 December 2010. It is possible for project participants and designated operational entities (DOEs) to liaise with a DNA to submit a request on their behalf.

Documents
Documents fall into different categories. Official documents are available to everyone and feature the logos of the United Nations and the Climate Change Convention. They carry a reference number, such as FCCC/CP/1998/1. Pre-session documents are available before a meeting, often in all six UN languages. In-session documents are distributed on-site (see CRPs, L docs, Misc. docs, Inf. docs and non-papers). Informal documents are often distributed outside the meeting room by observers.

Drafting group
A smaller group established by the President or a Chair of a Convention body to meet separately and in private to prepare draft text -- text which must still be formally approved later in a plenary session. Observers generally may not attend drafting group meetings.
E

EIT
Countries with Economies in Transition. Central and East European countries and former republics of the Soviet Union in transition from state-controlled to market economies.

Emission reduction unit (ERU)
A Kyoto Protocol unit equal to 1 metric tonne of CO2 equivalent. ERUs are generated for emission reductions or emission removals from joint implementation projects.

Emissions trading
One of the three Kyoto mechanisms, by which an Annex I Party may transfer Kyoto Protocol units to, or acquire units from, another Annex I Party. An Annex I Party must meet specific eligibility requirements to participate in emissions trading.

Entry into force
The point at which an intergovernmental agreement becomes legally binding -- occurring at a pre-stated interval after a pre-stated and required number of ratifications by countries has been achieved. The Climate Change Convention required 50 ratifications to enter into force. It now enters into force for each new Party 90 days after that Party ratifies the Convention.

Environmental Integrity Group
A coalition or negotiating alliance consisting of Mexico, the Republic of Korea, Switzerland, Lichtenstein and Monaco.

ESCAP
Economic and Social Commission for Asia and the Pacific.

European Union (EU)
As a regional economic integration organization, the EU is a Party to both the Convention and the Kyoto Protocol. However, it does not have a separate vote from its member states. Because the EU signed the Convention when it was known as the EEC (European Economic Community), the EU retains this name for all formal Convention-related purposes. Members are Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, and the United Kingdom.

Executive Board of the Clean Development Mechanism
A 10-member panel elected at COP-7 which supervises the CDM.

Expert Group on Technology Transfer (EGTT)
An expert group established at COP 7 with the objective of enhancing the implementation of Article 4.5 of the Convention, by analyzing and identifying ways to facilitate and advance technology transfer activities under the Convention. The EGTT completed its work in 2010.

Expert review teams
Groups of experts, nominated by Parties, who review national reports submitted by Annex I Parties to the UNFCCC and the Kyoto Protocol.
F

FAO
Food and Agriculture Organization of the United Nations.

Fast-start Finance (FSF)
At COP 15 in Copenhagen in 2009, developed countries pledged to provide new and additional resources, including forestry and investments, approaching USD 30 billion for the period 2010 - 2012 and with balanced allocation between mitigation and adaptation. This collective commitment has come to be known as "Fast-start Finance". More information here.

Financial Mechanism
To facilitate the provision of climate finance, the Convention established a financial mechanism to provide funds to developing country Parties. The financial mechanism also serves the Kyoto Protocol. The Convention states that the operation of the financial mechanism can be entrusted to one or more existing international entities. The Global Environment Facility (GEF) has served as an operating entity of the financial mechanism for many years and at COP 17 in 2011, Parties also decided to designate the Green Climate Fund (GCF) as an operating entity of the financial mechanism. The financial mechanism is accountable to the COP, which decides on its policies, programme priorities and eligibility criteria for funding.

Fourth Assessment Report (AR4)
The Fourth Assessment Report of the Intergovernmental Panel on Climate Change, released in 2007.

Friends of the Chair
Delegates called upon by the Chair (who takes into account the need for political balance among various interests) to assist in carrying out specific tasks.

Fugitive fuel emissions
Greenhouse-gas emissions as by-products or waste or loss in the process of fuel production, storage, or transport, such as methane given off during oil and gas drilling and refining, or leakage of natural gas from pipelines.
G

GATT
General Agreement on Tariffs and Trade.

GCOS
Global Climate Observing System.

Global Environment Facility (GEF)
The GEF is an independent financial organization that provides grants to developing countries for projects that benefit the global environment and promote sustainable livelihoods in local communities. The Parties to the Convention assigned operation of the financial mechanism to the GEF on an on-going basis, subject to review every four years. The financial mechanism is accountable to the COP. More information here.

Global warming potential (GWP)
An index representing the combined effect of the differing times greenhouse gases remain in the atmosphere and their relative effectiveness in absorbing outgoing infrared radiation.

GOOS
Global Ocean Observing System.

Green Climate Fund (GCF)
At COP 16 in Cancun in 2010, Governments established a Green Climate Fund as an operating entity of the financial mechanism of the Convention under Article 11. The GCF will support projects, programmes, policies and other activities in developing country Parties. The Fund will be governed by the GCF Board. More information here.

Greenhouse gases (GHGs)
The atmospheric gases responsible for causing global warming and climate change. The major GHGs are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N20). Less prevalent --but very powerful -- greenhouse gases are hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6).

Group of 77 (G-77) and China
A large negotiating alliance of developing countries that focuses on numerous international topics, including climate change. The G-77 was founded in 1967 under the auspices of the United Nations Conference on Trade and Development (UNCTAD). It seeks to harmonize the negotiating positions of its 131 member states.

Group of Mountain Landlocked Developing Countries
Negotiating group formally established in June 2010 by the governments of Armenia, Kyrgyzstan and Tajikstan, focused issues faced by landlocked mountain developing countries specifically vulnerable to transportation costs and food insecurity, with a view towards expanding the group to include other interested countries.

GRULAC
Group of Latin American and Caribbean States.

GTOS
Global Terrestrial Observing System.
H

HFC
Hydrofluorocarbons.

"Hot air"
Refers to the concern that some governments will be able to meet their targets for greenhouse-gas emissions under the Kyoto Protocol with minimal effort and could then flood the market with emissions credits, reducing the incentive for other countries to cut their own domestic emissions.
I

IAR
Independent Assessment Report, the output of an independent assessment of each Annex I Party's International Transaction Log, which in turn is part of the Party's reporting requirements to the UNFCCC. IAR is forwarded to expert review teams for consideration as part of the review of national registries under Article 8 of the Kyoto Protocol. the procedure to produce the IAR is designed to provide independent assessment of each national registry.

ICA
International consultation and analysis, a form of review currently being negotiated and designed in the UNFCCC intergovernmental process.

ICAO
International Civil Aviation Organization.

ICCP
International Climate Change Partnership - global coalition of companies and trade associations committed to constructive participation in international policy making on climate change.

ICLEI
International Council of Local Environmental Initiatives.

IEA
International Energy Agency.

IGO
Intergovernmental organization.

IMO
International Maritime Organization.

Implementation
Actions (legislation or regulations, judicial decrees, or other actions) that governments take to translate international accords into domestic law and policy.

INC
Intergovernmental Negotiating Committee for the UNFCCC (1990-1995). A committee created to draft the Convention. The INC met in five sessions between February 1991 and May 1992. After the text of the Convention was adopted in 1992, the INC met six further times to prepare for COP-1. It completed its work in February 1995. 

INDC
Intended Nationally Determined Contributions. More information here

In-depth review (IDR)
A process by which an Annex I Party's implementation of the Convention and/or the Kyoto Protocol is technically assessed by international teams of experts.

INF document
Denotes an Information document. These documents are not translated and are available in the original language of issue.

Informal contact group
A group of delegates instructed by the President or a Chair to meet in private to discuss a specific matter in an effort to consolidate different views, reach a compromise, and produce an agreed proposal, often in the form of a written text.

Intergovernmental Panel on Climate Change (IPCC)
Established in 1988 by the World Meteorological Organization and the UN Environment Programme, the IPCC surveys world-wide scientific and technical literature and publishes assessment reports that are widely recognized as the most credible existing sources of information on climate change. The IPCC also works on methodologies and responds to specific requests from the Convention's subsidiary bodies. The IPCC is independent of the Convention.

IOC
Intergovernmental Oceanographic Commission.

ISO
International Standards Organization.

IUCN
International Union for Conservation of Nature.
J

Joint Implementation Supervisory Committee (JISC)
The Joint Implementation Supervisory Committee (JISC), under the authority and guidance of the CMP, inter alia, supervises the verification procedure for Joint Implementation projects.

Joint Liaison Group (JLG)
Group of representatives of UNFCCC, CBD, and UNCCD Secretariats set up to explore common activities to confront problems related to climate change, biodiversity and desertification.

Joint implementation (JI)
A mechanism under the Kyoto Protocol through which a developed country can receive "emissions reduction units" when it helps to finance projects that reduce net greenhouse-gas emissions in another developed country (in practice, the recipient state is likely to be a country with an "economy in transition"). An Annex I Party must meet specific eligibility requirements to participate in joint implementation.

JUSSCANNZ
An acronym representing non-EU industrialized countries which occasionally meet to discuss various issues related to climate change. The members are Japan, the United States, Switzerland, Canada, Australia, Norway, and New Zealand. Iceland, Mexico, and the Republic of Korea may also attend JUSSCANZ meetings.

JWG
Joint working group.
K

Kyoto Protocol
An international agreement standing on its own, and requiring separate ratification by governments, but linked to the UNFCCC. The Kyoto Protocol, among other things, sets binding targets for the reduction of greenhouse-gas emissions by industrialized countries. More information here. 

Kyoto mechanisms
Three procedures established under the Kyoto Protocol to increase the flexibility and reduce the costs of making greenhouse-gas emissions cuts. They are the Clean Development Mechanism, Emissions Trading and Joint Implementation.
L

Land use, land-use change, and forestry (LULUCF)
A greenhouse gas inventory sector that covers emissions and removals of greenhouse gases resulting from direct human-induced land use, land-use change and forestry activities.

L. docs
In-session documents that contain draft reports and texts for adoption by the COP or its subsidiary bodies. Usually such documents are available in all six UN languages.

Leakage
That portion of cuts in greenhouse-gas emissions by developed countries -- countries trying to meet mandatory limits under the Kyoto Protocol -- that may reappear in other countries not bound by such limits. For example, multinational corporations may shift factories from developed countries to developing countries to escape restrictions on emissions.

Least Developed Countries (LDCs)
The world's poorest countries. The criteria currently used by the Economic and Social Council (ECOSOC) for designation as an LDC include low income, human resource weakness and economic vulnerability. Currently 48 countries have been designated by the UN General Assembly as LDCs.

Least Developed Countries Expert Group (LEG)
A panel of 13 experts which provides advice to LDCs on the preparation and implementation of national adaptation programmes of action (NAPAs) -- plans for addressing the urgent and immediate needs of those countries to adapt to climate change.

Least Developed Country Fund (LDCF)
The LDCF is a fund established to support a work programme to assist Least Developed Country Parties to carry out, inter alia, the preparation and implementation of national adaptation programmes of action (NAPAs). The Global Environment Facility, as the entity that operates the financial mechanism of the Convention, has been entrusted to operate this fund. More information here.

Loss and damage
At COP 16 in Cancun in 2010, Governments established a work programme in order to consider approaches to address loss and damage associated with climate change impacts in developing countries that are particularly vulnerable to the adverse effects of climate change as part of the Cancun Adaptation Framework. More information here.
M

Marrakesh Accords
Agreements reached at COP-7 which set various rules for "operating" the more complex provisions of the Kyoto Protocol. Among other things, the accords include details for establishing a greenhouse-gas emissions trading system; implementing and monitoring the Protocol's Clean Development Mechanism; and setting up and operating three funds to support efforts to adapt to climate change.

Meeting
A formal gathering that occurs during a "session." Each session of the COP, for example, is divided into a number of meetings. A meeting is generally scheduled from 10 a.m. to 1 p.m. or from 3 p.m. to 6 p.m.

MISC documents
Denotes a Miscellaneous document. These documents are not translated and are issued on plain paper with no United Nations masthead. In the UNFCCC process, submissions by Parties are normally issued as miscellaneous documents. They generally contain views or comments published as received from a delegation without formal editing.

Mitigation
In the context of climate change, a human intervention to reduce the sources or enhance the sinks of greenhouse gases. Examples include using fossil fuels more efficiently for industrial processes or electricity generation, switching to solar energy or wind power, improving the insulation of buildings, and expanding forests and other "sinks" to remove greater amounts of carbon dioxide from the atmosphere.

Montreal Protocol
The Montreal Protocol on Substances that Deplete the Ozone Layer, an international agreement adopted in Montreal in 1987.

MRV
Measurable, reportable and verifiable. A process/concept that potentially supports greater transparency in the climate change regime.
N

N2O
Nitrous oxide.

National adaptation programmes of action (NAPAs)
Documents prepared by least developed countries (LDCs) identifying urgent and immediate needs for adapting to climate change.

National communication
A document submitted in accordance with the Convention (and the Protocol) by which a Party informs other Parties of activities undertaken to address climate change. Most developed countries have now submitted their fifth national communications; most developing countries have completed their first national communication and are in the process of preparing their second.

National delegation
One or more officials empowered to represent and negotiate on behalf of a government.

Nationally appropriate mitigation actions (NAMAs)
At COP 16 in Cancun in 2010, Governments decided to set up a registry to record nationally appropriate mitigation actions seeking international support, to facilitate the matching of finance, technology and capacity-building support with these actions, and to recognize other NAMAs. More information here.

NDC
According to Article 4 paragraph 2 of the Paris Agreement, each Party shall prepare, communicate and maintain successive nationally determined contributions (NDCs) that it intends to achieve. Parties shall pursue domestic mitigation measures, with the aim of achieving the objectives of such contributions. More information here.

N.N.
Not named

Non-Annex I Parties
Refers to countries that have ratified or acceded to the United Nations Framework Convention on Climate Change that are not included in Annex I of the Convention. List of Parties to the Convention is available here.

Non-governmental organizations (NGOs)
Organizations that are not part of a governmental structure. They include environmental groups, research institutions, business groups, and associations of urban and local governments. Many NGOs attend climate talks as observers. To be accredited to attend meetings under the Convention, NGOs must be non-profit. More information here.

Non-paper
An in-session document issued informally to facilitate negotiations. A non-paper does not have an official document symbol. It may have an identifying number or carry the name of its author.

Non-Party
A state that has not ratified the Convention but attends meetings as an observer. More information here.

"No-regrets options"
Technology for reducing greenhouse-gas emissions whose other benefits (in terms of efficiency or reduced energy costs) are so extensive that the investment is worth it for those reasons alone. For example, combined-cycle gas turbines -- in which the heat from the burning fuel drives steam turbines while the thermal expansion of the exhaust gases drives gas turbines -- may boost the efficiency of electricity generating plants by 70 per cent.
O

Observers
Agencies, non-governmental organizations, and Governments not Parties to the Convention which are permitted to attend, but not vote, at meetings of the COP, the CMP and the subsidiary bodies. Observers may include the United Nations and its specialized agencies; other intergovernmental organizations such as the International Atomic Energy Agency; and accredited non-governmental organizations (NGOs). More information here.

OECD
Organisation for Economic Co-operation and Development.

OPEC
Organization of Petroleum Exporting Countries.
P

Party
A state (or regional economic integration organization such as the European Union) that agrees to be bound by a treaty and for which the treaty has entered into force. More information here.

PFC
Perfluorocarbon.

Plenary
A formal meeting of the entire COP, CMP or one of the subsidiary bodies. Formal decisions or conclusions may only be taken during plenary sessions.

Policies and measures (PAMs)
A frequently used phrase -- sometimes abbreviated as PAMs -- referring to the steps taken or to be taken by countries to reduce greenhouse-gas emissions under the UNFCCC and the Kyoto Protocol. Some possible policies and measures are listed in the Protocol and could offer opportunities for intergovernmental cooperation.

President
The official of a member government elected by the Parties to preside over the COP and the CMP. The President is often a senior official or minister from the state or region hosting the Conference. The President may not participate in the negotiations as a representative of the member government during the term of presidency.

Protocol
An international agreement linked to an existing convention, but as a separate and additional agreement which must be signed and ratified by the Parties to the convention concerned. Protocols typically strengthen a convention by adding new, more detailed commitments.
Q

Quantified Emissions Limitation and Reduction Commitments (QELROs)
Legally binding targets and timetables under the Kyoto Protocol for the limitation or reduction of greenhouse-gas emissions by developed countries.
R

Ratification
Formal approval, often by a Parliament or other national legislature, of a convention, protocol, or treaty, enabling a country to become a Party. Ratification is a separate process that occurs after a country has signed an agreement. The instrument of ratification must be deposited with a "depositary" (in the case of the Climate Change Convention, the UN Secretary-General) to start the countdown to becoming a Party (in the case of the Convention, the countdown is 90 days).

Recommendation
A formal act of the COP or the CMP which is weaker than a decision or a resolution, and is not binding on Parties to the Convention or the Kyoto Protocol.

REDD
Reducing Emissions from Deforestation and Forest Degradation.

Reforestation
Replanting of forests on lands that have previously contained forests but that have been converted to some other use.

REG document
Regular documents have a serial number following the year. They are translated into all six official languages of the United Nations.

Regional groups
Alliances of countries, in most cases sharing the same geographic region, which meet privately to discuss issues and nominate bureau members and other officials for activities under the Convention. The five regional groups are Africa, Asia, Central and Eastern Europe (CEE), Latin America and the Caribbean (GRULAC), and the Western Europe and Others Group (WEOG).

Registries, registry systems
Electronic databases that tracks and records all transactions under the Kyoto Protocol's greenhouse-gas emissions trading system (the "carbon market") and under mechanisms such as the Clean Development Mechanism. "Registry" may also refer to current discussions on a system for inscribing nationally appropriate mitigation actions.

Research and systematic observation
An obligation of Parties to the Climate Change Convention; they are called upon to promote and cooperate in research and systematic observation of the climate system, and called upon to aid developing countries to do so.

Reservation
An exception or concern noted for the record by a Party in the course of accepting a decision of the COP or the CMP. No reservations are allowed to the Convention itself, or to the Protocol.

Reservoirs
A component or components of the climate system where a greenhouse gas or a precursor of a greenhouse gas is stored. Trees are "reservoirs" for carbon dioxide.

Resolution
Directives that guide the work of the COP or the CMP-- opinions rather than permanent legal acts. Unlike decisions, resolutions do not generally become part of the formal body of legislation enacted by the COP or the CMP.

Review of commitments
Regular scrutiny by Convention Parties of the adequacy of the treaty's Article 4.2 (a) and (b) outlining developed country commitments to limit greenhouse-gas emissions. The first review took place at COP-1 and led to a finding that progress was not "adequate" -- and so to negotiations that led to the Kyoto Protocol, which has more stringent commitments for developed countries.

Rio Conventions
Three environmental conventions, two of which were adopted at the 1992 "Earth Summit" in Rio de Janeiro: the United Nations Framework Convention on Climate Change (UNFCCC), and the Convention on Biodiversity (CBD), while the third, the United Nations Convention to Combat Desertification (UNCCD), was adopted in 1994. The issues addressed by the three treaties are related -- in particular, climate change can have adverse effects on desertification and biodiversity -- and through a Joint Liaison Group, the secretariats of the three conventions take steps to coordinate activities to achieve common progress.

Rio+20
The United Nations Conference on Sustainable Development, to be held in Rio de Janeiro, Brazil, on June 4-6, 2012. The first UN Conference on Sustainable Development was the "Earth Summit", held in 1992, and it spawned the three "Rio Conventions"-- the UNFCCC, the UNCCD, and the UNCBD.

Removal unit (RMU)
A Kyoto Protocol unit equal to 1 metric tonne of carbon dioxide equivalent. RMUs are generated in Annex I Parties by LULUCF activities that absorb carbon dioxide.

Roster of experts
Experts nominated by Parties to the Climate Change Convention to aid the Secretariat in work related to review of national reports of Annex I Parties, preparation of reports on adaptation technology, the transfer of technology to developing countries, and the development of know-how on mitigating and adapting to climate change.

Rules of procedure
The parliamentary rules that govern the procedures of the COP, the CMP and the subsidiary bodies, covering such matters as decision-making and participation. The COP has not yet formally adopted rules of procedure, but all except one (on voting) are currently being "applied." As such, they are commonly referred to as the "draft rules of procedure being applied".
S

SF6
Sulphur hexafluoride.

Second Assessment Report (SAR)
An extensive review of worldwide research on climate change compiled by the IPCC and published in 1995. Some 2,000 scientists and experts participated. The report is also known as Climate Change 1995. The SAR concluded that "the balance of evidence suggests that there is a discernible human influence on global climate." It also said "no-regrets options" and other cost-effective strategies exist for combating climate change.

Secretariat
The office staffed by international civil servants responsible for "servicing" the UNFCCC Convention and ensuring its smooth operation. The secretariat makes arrangements for meetings, compiles and prepares reports, and coordinates with other relevant international bodies. The Climate Change Secretariat, which is based in Bonn, Germany, is institutionally linked to the United Nations. More information here.

SIDS
Small island developing States.

Signature
The signing by a head of state or government, a foreign minister, or other designated official indicating a country's agreement with an adopted international text, such as a Convention or Protocol, and signalling the country's intention of becoming a Party to the agreement.

Sink
Any process, activity or mechanism which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere. Forests and other vegetation are considered sinks because they remove carbon dioxide through photosynthesis.

Special Climate Change Fund (SCCF)
The SCCF was established to finance projects relating to adaptation; technology transfer and capacity building; energy, transport, industry, agriculture, forestry and waste management; and economic diversification. This fund should complement other funding mechanisms for the implementation of the Convention. The Global Environment Facility (GEF), as the entity that operates the financial mechanism of the Convention, has been entrusted to operate this fund. More information here.

"Spill-over effects" (also referred to as "rebound effects" or "take-back effects")
Reverberations in developing countries caused by actions taken by developed countries to cut greenhouse-gas emissions. For example, emissions reductions in developed countries could lower demand for oil and thus international oil prices, leading to more use of oil and greater emissions in developing nations, partially off-setting the original cuts. Current estimates are that full-scale implementation of the Kyoto Protocol may cause 5 to 20 per cent of emissions reductions in industrialized countries to "leak" into developing countries.

Subsidiary body
A committee that assists the Conference of the Parties. Two permanent subsidiary bodies are created by the Convention: the Subsidiary Body for Implementation (SBI) and the Subsidiary Body for Scientific and Technological Advice (SBSTA). Two major temporary bodies that exist currently are the Ad Hoc Working Group on Further Commitments for Annex I Parties under the Kyoto Protocol (AWG-KP), established at COP 11 in Montreal, and the Ad Hoc Working Group on Long-term Cooperative Action under the Convention (AWG-LCA), established at COP 13 in Bali. Additional subsidiary bodies may be established as needed.

Square brackets
Typographical symbols [ -- ] placed around text under negotiation to indicate that the language enclosed is being discussed but has not yet been agreed upon.

Subsidiary Body for Implementation (SBI)
The SBI makes recommendations on policy and implementation issues to the COP and, if requested, to other bodies. More information here.

Subsidiary Body for Scientific and Technological Advice (SBSTA)
The SBSTA serves as a link between information and assessments provided by expert sources (such as the IPCC) and the COP, which focuses on setting policy. More information here.

Sustainable development
Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.
T

Technology transfer
A broad set of processes covering the flows of know-how, experience and equipment for mitigating and adapting to climate change among different stakeholders

Third Assessment Report (TAR)
The third extensive review of global scientific research on climate change, published by the IPCC in 2001. Among other things, the report stated that "The Earth's climate system has demonstrably changed on both global and regional scales since the pre-industrial era, with some of these changes attributable to human activities. There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities." The TAR also focused on the regional effects of climate change.

Track-two JI
One of two approaches for verifying emission reductions or removals under joint implementation, whereby each JI project is subject to verification procedures established under the supervision of the Joint Implementation Supervisory Committee. Track two procedures require that each project is reviewed by an accredited independent entity.

Trust funds
Funds earmarked for specific programmes within the UN system.

TT:CLEAR
Technology Transfer Information Clearing House.

TUNGO
Trade related non-governmental organisations.
U

Umbrella group
A loose coalition of non-European Union developed countries formed following the adoption of the Kyoto Protocol. Although there is no formal membership list, the group usually includes Australia, Canada, Iceland, Japan, New Zealand, Norway, the Russian Federation, Ukraine, and the United States.

UN
United Nations.

UNCCD
United Nations Convention to Combat Desertification.

UNCED
United Nations Conference on Environment and Development.

UNCTAD
United Nations Conference on Trade and Development.

UNDP
United Nations Development Programme.

UNECE
United Nations Economic Commission for Europe.

UNEP
United Nations Environment Programme.

UNFCCC
United Nations Framework Convention on Climate Change.

UNIDO
United Nations Industrial Development Organization.

Uniform report format
A standard format through which Parties submit information on activities implemented jointly under the Convention.
V

Voluntary commitments
A draft article considered during the negotiation of the Kyoto Protocol that would have permitted developing countries to voluntarily adhere to legally binding emissions targets. The proposed language was dropped in the final phase of the negotiations. The issue remains important for some delegations and continues to be discussed, currently in the context of the Bali Action Plan, in terms of what constitutes "voluntary".

Vulnerability
The degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate variation to which a system is exposed, its sensitivity, and its adaptive capacity.
W

WCC
World Climate Conference.

WEOG
Western European and Others Group (United Nations regional group).

WHO
World Health Organization.

WMO
World Meteorological Organization.

WSSD
World Summit on Sustainable Development.

WTO
World Trade Organization.
Y

YOUNGO
Youth non-governmental organisation