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Appendices
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Appendices
A.1.
User guide and access to more detailed information.................................................................1
A.2.
Glossary.....................................................................................................................................1
A.3.
Acronyms, chemical symbols, scientific units, country groupings ...........................................16
3.1
Acronyms and chemical symbols ........................................................................................16
3.2
Scientific units......................................................................................................................17
3.3
Country groupings ...............................................................................................................18
A.4.
List of authors...........................................................................................................................19
4.1
Core Writing Team members...............................................................................................19
4.2
Extended Writing Team member.........................................................................................20
A.5.
List of reviewers and Review Editors.......................................................................................20
5.1
Reviewers ............................................................................................................................20
5.2
Review Editors.....................................................................................................................20
A.6.
Index.........................................................................................................................................21
A.1. User guide and access to more detailed information
As defined in the IPCC Procedures, the SYR synthesises and integrates material contained within
IPCC Assessment Reports and Special Reports. The scope of the SYR of the Fourth Assessment
Report includes material contained in the three Working Group contributions to the AR4, and it draws
on information contained in other IPCC Reports as required. The SYR is based exclusively on
assessments by the IPCC Working Groups, it does not refer to or assess the primary scientific
literature itself.
The SYR is largely self-contained but provides only a very condensed summary of the much richer
information contained in the underlying Working Group reports. Users may wish to access relevant
material at the required level of detail in the following manner:
The Summary for Policymakers (SPM) of the SYR provides the most condensed summary of
our current understanding of scientific, technical and socio-economic aspects of climate
change. All references in curly brackets in this Summary for Policymakers refer to numbered
sections of the longer report of the SYR.
The Introduction and six Topics of the longer report of the SYR provide more detailed and
more comprehensive information than the SYR SPM. References in curly backets in the
longer report of the SYR point to chapter sections, Summaries for Policymakers and
Technical Summaries of the three underlying Working Group reports of the AR4, and in some
instances to other topic sections of the SYR itself. References to the IPCC Third Assessment
Report in 2001 (TAR) are identified by adding “TAR” in front of the cited report.
Users who wish to gain a better understanding of scientific details or access the primary
scientific literature on which the SYR is based, should refer to chapter sections of the
underlying Working Group reports that are cited in the longer report of the SYR. The
individual chapters of the Working Group reports provide comprehensive references to the
primary scientific literature on which IPCC assessments are based, and also offer the most
detailed region- and sector-specific information.
A comprehensive glossary, list of acronyms, abbreviations and scientific units, and an index are
provided below to facilitate use of this report by as wide an audience as possible.
A.2. Glossary
This Glossary is based on the glossaries published in the IPCC Fourth Assessment Report. Additional
work has been undertaken on additions, consistency and shortening of definitions to make this
glossary more suitable to a wider audience.
Editor:
Alfons P. M. Baede (Netherlands)
Co-editors:
Paul van der Linden (United Kingdom), Aviel Verbruggen (Belgium)

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The italics used have the following meaning:
Glossary word reference
Glossary secondary reference (i.e. terms which are either
contained in a glossary of the IPCC Working Group
contributions to the AR4, or defined within the text of
an entry of this glossary).
A.
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 possible abrupt events that have been
proposed include a dramatic reorganization of the
thermohaline circulation, rapid deglaciation and massive
melting of permafrost or increases in soil respiration leading to
fast changes in the carbon cycle. Others may be truly
unexpected, resulting from a strong, rapidly changing, forcing
of a non-linear system.
Absorption, scattering and emission of radiation
Electromagnetic radiation may interact with matter, be it in the
form of the atoms and molecules of a gas (e.g. the gases in
the atmosphere) or in the form of particulate, solid or liquid,
matter (e.g. aerosols), in various ways. Matter itself emits
radiation in accordance with its composition and temperature.
Radiation may be absorbed by matter, whereby the absorbed
energy may be transferred or re-emitted. Finally, radiation may
also be deflected from its original path (scattered) as a result
of interaction with matter.
Activities Implemented Jointly (AIJ)
The pilot phase for Joint Implementation, as defined in Article
4.2(a) of the United Nations Framework Convention on Climate
Change (UNFCCC) 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 UNFCCC to gain
experience in jointly implemented projects. There is no credit
for AIJ during the pilot phase. A decision remains 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 potential mechanisms
for stimulating additional resource flows for reducing
emissions. See also Clean Development Mechanism, and
Emissions Trading.
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 temperature-shock resistant plants for sensitive ones,
etc.
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 whole of capabilities, resources and institutions of a
country or region to implement effective adaptation measures.
Aerosols
A collection of airborne solid or liquid particles, with a typical
size between 0.01 and 10 micrometer (a millionth of a meter)
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
through acting as cloud condensation nuclei or modifying the
optical properties and lifetime of clouds.
Afforestation
Planting of new forests on lands that historically have not
contained forests (for at least 50 years). 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)
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 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.
Albedo feedback
A climate feedback involving changes in the Earth’s albedo. It
usually refers to changes in the cryosphere which has an
albedo much larger (0.8) than the average planetary albedo
(0.3). In a warming climate, it is anticipated that the
cryosphere would shrink, the Earth’s overall albedo would
decrease and more solar energy would be absorbed to warm
the Earth still further.
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, characterized by the presence of rosette-forming
herbaceous plants and low shrubby slow-growing woody
plants.
Annex I countries
The group of countries included in Annex I (as amended in
1998) to the United Nations Framework Convention on Climate
Change (UNFCCC), including all the OECD countries in the
year 1990 and countries with 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
greenhouse gas emissions by the year 2000. By default, the
other countries are referred to as Non-Annex I countries. For a
list of Annex I countries, see http://unfccc.int; for a list of OECD
countries, see http://www.oecd.org.

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Annex II countries
The group of countries included in Annex II to the United
Nations Framework Convention on Climate Change (UNFCCC),
including all OECD countries in the year 1990. 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.
For a list of Annex II countries, see http://unfccc.int; for a list of
OECD countries, see http://www.oecd.org.
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. For a list of Annex I countries,
see http://unfccc.int.
See Kyoto Protocol
Anthropogenic
Resulting from or produced by human beings.
Anthropogenic emissions
Emissions of greenhouse gases, greenhouse gas precursors,
and aerosols associated with human activities, including the
burning of fossil fuels, deforestation, land-use changes,
livestock, fertilization, etc.
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 (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.
Attribution
See Detection and attribution.
B.
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
Reference for measurable quantities from which an alternative
outcome can be measured, e.g. a non-intervention scenario
used as a reference in the analysis of intervention scenarios.
Basin
The drainage area of a stream, river, or lake.
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
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). 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.
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.
Borehole temperature
Borehole temperatures are measured in boreholes of tens to
hundreds of meters depth into the subsurface of the Earth.
Borehole temperature depth profiles are commonly used to
infer time variations in the ground surface temperature on
centennial time scales.
Bottom-up models
Bottom-up models represent reality by aggregating
characteristics of specific activities and processes, considering
technological, engineering and cost details. See also Top-
down models.
C.
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.
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 (CO
2
)
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 and of 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 (CO
2
) fertilization
The enhancement of the growth of plants as a result of
increased atmospheric carbon dioxide (CO
2
) concentration.
Depending on their mechanism of photosynthesis, certain
types of plants are more sensitive to changes in atmospheric
CO
2
concentration.

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Carbon intensity
The amount of emission of carbon dioxide per unit of Gross
Domestic Product.
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.
Carbon sequestration
See Uptake
Catchment
An area that collects and drains rainwater.
Chlorofluorocarbons (CFCs)
See Halocarbons
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 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 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 parts of this report different
averaging periods, such as a period of 20 years, are also used.
Climate-carbon cycle coupling
Future climate change induced by atmospheric emissions of
greenhouse gases will impact on the global carbon cycle.
Changes in the global carbon cycle in turn will influence the
fraction of anthropogenic greenhouse gases that remains in
the atmosphere, and hence the atmospheric concentrations of
greenhouse gases, resulting in further climate change. This
feedback is called climate-carbon cycle coupling. The first
generation coupled climate-carbon cycle models indicates that
global warming will increase the fraction of anthropogenic CO
2
that remains in the atmosphere.
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, 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; Detection and Attribution.
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 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 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 the most comprehensive end of the
spectrum currently available. There is an evolution towards
more complex models with interactive chemistry and biology
(see WGI Chapter 8). 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 an estimate of the actual evolution of the
climate in the future, for example, at seasonal, interannual or
long-term time scales. Since 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.
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 socioeconomic and
technological developments that may or may not be realised
and are therefore subject to substantial uncertainty.
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

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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 reports, equilibrium climate sensitivity refers to the
equilibrium change in the annual mean global surface
temperature following a doubling of the atmospheric equivalent
carbon dioxide concentration. Due to computational
constraints, the equilibrium climate sensitivity in a climate
model is usually 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 transient climate response is the change in the global
surface temperature, averaged over a 20-year period, centred
at the time of atmospheric carbon dioxide doubling, that is, at
year 70 in a 1% yr
–1
compound carbon dioxide 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 shift
An abrupt shift or jump in mean values signalling a change in
climate regime (see Patterns of climate variability). Most widely
used in conjunction with the 1976/1977 climate shift that
seems to correspond to a change in El Nińo-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 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 feedback
A climate feedback involving changes in any of the properties
of clouds as a response to other atmospheric changes.
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, and the radiative properties of clouds, and
an estimate of the impact of these changes on the Earth’s
radiation budget. At present, cloud feedbacks remain the
largest source of uncertainty in climate sensitivity estimates.
See also Radiative forcing.
CO
2
See Carbon dioxide.
CO
2
-equivalent
See Box “Carbon dioxide-equivalent (CO
2
-eq) emissions and
concentrations” in topic 2 of the Synthesis Report and WGI
Chapter 2.10.
CO
2
-fertilization
See Carbon dioxide fertilization.
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).
Combined Heat and Power (CHP)
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. Also called co-generation.
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, organisations, or individuals,
conform to the implementing obligations. See also
Implementation.
Confidence
The level of confidence in the correctness of a result is
expressed in this report, using a standard terminology defined
as follows:
Terminology
Degree of confidence in being
correct
Very high confidence
High confidence
Medium confidence
Low confidence
Very low confidence
At least 9 out of 10 chance of
being correct
About 8 out of 10 chance
About 5 out of 10 chance
About 2 out of 10 chance
Less than 1 out of 10 chance
See also Likelihood; Uncertainty
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. See Coral bleaching; Coral reefs
Coral bleaching
The paling in colour which results if a coral loses its symbiotic,
energy-providing, organisms.
Coral reefs
Rock-like limestone 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 subtropical oceans.
Cost
The consumption of resources such as labour time, capital,
materials, fuels, etc. as a 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, damage costs (to ecosystems,
people and economies due to negative effects from climate

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change), and implementation costs of changing existing rules
and regulation, capacity building efforts, information, training
and education, etc. Private costs are carried by individuals,
companies or other private entities that undertake the action,
whereas social costs include also the external costs on the
environment and on society as a whole. The negative of costs
are benefits (also sometimes called negative costs). Costs
minus benefits are net costs.
Cryosphere
The component of the climate system consisting of all snow,
ice and frozen ground (including permafrost) on and beneath
the surface of the Earth and ocean. See also Glacier; Ice
sheet.
D.
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 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).
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.
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.
Development path or pathway
An evolution based on an array of technological, economic,
social, institutional, cultural, and biophysical characteristics
that determine the interactions between natural and human
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).
Discount rate
See Discounting
Drought
In general terms, drought is a ‘prolonged absence or marked
deficiency of precipitation’, a ‘deficiency that results in water
shortage for some activity or for some group’, or a ‘period of
abnormally dry weather sufficiently prolonged for the lack of
precipitation to cause a serious hydrological imbalance’ (Heim,
2002). Drought has been defined in a number of ways.
Agricultural drought relates to moisture deficits in the topmost
1 metre or so of soil (the root zone) that affect crops,
meteorological drought is mainly a prolonged deficit of
precipitation, and hydrologic drought is related to below-normal
streamflow, lake and groundwater levels. A megadrought is a
longdrawn out and pervasive drought, lasting much longer than
normal, usually a decade or more.
Dynamical ice discharge
Discharge of ice from ice sheets or ice caps caused by the
dynamics of the ice sheet or ice cap (e.g. in the form of glacier
flow, ice streams and calving icebergs) rather than by melt or
runoff.
E.
Economic (mitigation) potential
See Mitigation potential.
Economies in Transition (EITs)
Countries with their economies changing from a planned
economic system to a market economy.
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, ultimately, the
entire Earth.
El Nińo-Southern Oscillation (ENSO)
The term El Nińo was initially used to describe a warm-water
current that periodically flows along the coast of Ecuador and
Perú, disrupting the local fishery. It has since become
identified with a basinwide warming of the tropical Pacific 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 collectively known as El Nińo-
Southern Oscillation, or ENSO. 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 Nińa.
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) new
emission scenarios, the so-called SRES scenarios, were

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published. For the meaning of some terms related to these
scenarios, see SRES scenarios.
Emission(s) trading
A market-based approach to achieving environmental
objectives. It allows those reducing greenhouse gas 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 trajectory
A projected development in time of the emission of a
greenhouse gas or group of greenhouse gases, aerosols and
greenhouse gas precursors.
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. This primary energy needs to
be converted and transported to become usable energy (e.g.
light). 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 balance
The difference between the total incoming and total outgoing
energy in the climate system. 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
amount of incoming solar radiation on average must 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.
Energy efficiency
Ratio of useful energy output of a system, conversion process
or activity, to its energy input.
Energy intensity
Energy intensity is the ratio of energy use to economic or
physical output. At the national level, energy intensity is the
ratio of total primary energy use or final energy use to Gross
Domestic Product. At the activity level, one can also use
physical quantities in the denominator, e.g. litre fuel/vehicle
km.
Equivalent carbon dioxide concentration
See Box “Carbon dioxide-equivalent (CO
2
-eq) emissions and
concentrations” in topic 2 of the Synthesis Report.
Equivalent carbon dioxide emission
See Box “Carbon dioxide-equivalent (CO
2
-eq) emissions and
concentrations” in topic 2 of the Synthesis Report and WGI
Chapter 2.10.
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.
Evapotranspiration
The combined process of water evaporation from the Earth’s
surface and transpiration from vegetation.
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.
Extinction
The complete disappearance of an entire biological species.
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 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.
F-gases
This term refers to the groups of gases hydrofluorocarbons,
perfluorocarbons, and sulphurhexafluoride, which are covered
under the Kyoto Protocol.
Feedback
See Climate feedback.
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.
Forcing
See External forcing
Forecast
See Climate forecast; Climate projection; 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. Particular criteria apply under the Kyoto Protocol.
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

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(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 fuels
Carbon-based fuels from fossil hydrocarbon deposits, including
coal, peat, oil, and natural gas.
Framework Convention on Climate Change
See United Nations Framework Convention on Climate
Change (UNFCCC).
Frozen ground
Soil or rock in which part or all of the pore water is frozen (Van
Everdingen, 1998). Frozen ground includes permafrost.
Ground that freezes and thaws annually is called seasonally
frozen ground.
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 carbon dioxide) and the heat can be
utilized. See Combined Heat and Power.
Fuel switching
In general this is substituting fuel A for fuel B. In the climate
change discussion it is implicit that fuel A has a lower carbon
content than fuel B, e.g. natural gas for coal.
G.
Glacial lake
A lake formed by glacier meltwater, located either at the front
of a glacier (known as a proglacial lake), on the surface of a
glacier (supraglacial lake), within the glacier (englacial lake) or
at the glacier bed (subglacial lake).
Glacier
A mass of land ice which 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. See Mass balance
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.
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 carbon dioxide. The GWP represents the combined
effect of the differing times these gases remain in the
atmosphere and their relative effectiveness in absorbing
outgoing thermal infrared radiation. The Kyoto Protocol is
based on GWPs from pulse emissions over a 100-year time
frame.
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 (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
thermal infrared radiation emitted by the Earth’s surface, the
atmosphere itself, and by clouds. This property causes the
greenhouse effect. Water vapour (H
2
O), carbon dioxide (CO
2
),
nitrous oxide (N
2
O), methane (CH
4
) and ozone (O
3
) 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 CO
2
, N
2
O and CH
4
,
the Kyoto Protocol deals with the greenhouse gases sulphur
hexafluoride (SF
6
), hydrofluorocarbons (HFCs) and
perfluorocarbons (PFCs).
Gross Domestic Product (GDP)
Gross Domestic Product (GDP) is the monetary value of all
goods and services produced within a nation.
H.
Halocarbons
A collective term for the group of partially halogenated organic
species, including the chlorofluorocarbons (CFCs),
hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons
(HFCs), halons, methyl chloride, methyl bromide, etc. 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.
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 Fourth Assessment
Report.
Hydrochlorofluorocarbons (HCFCs)
See Halocarbons
Hydrofluorocarbons (HFCs)
One of the six greenhouse gases or groups of 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. See Halocarbons
Hydrosphere
The component of the climate system comprising liquid surface
and subterranean water, such as oceans, seas, rivers, fresh
water lakes, underground water, etc.

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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, condensates 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, discharges into streams, and
ultimately, flows out into the oceans, from which it will
eventually evaporate again (AMS, 2000). The various systems
involved in the hydrological cycle are usually referred to as
hydrological systems.
Hydrological systems
See Hydrological cycle
I.
Ice cap
A dome shaped ice mass, usually covering a highland area,
which is considerably smaller in extent than an ice sheet.
Ice core
A cylinder of ice drilled out of a glacier or 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 dynamics (the flow of the ice as it deforms
internally and/or slides at its base). An ice sheet flows
outwards 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 three large ice sheets in the
modern world, one on Greenland and two on Antarctica, the
East and West Antarctic Ice Sheet, divided by the
Transantarctic Mountains. During glacial periods there were
others.
(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.
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. See also
Compliance
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.
Induced technological change
See technological 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 eighteenth 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.
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.
In the context of the climate system, inertia relates to the delay
in climate change after an external forcing has been applied,
and to the continuation of climate change even after the
external forcing has been stabilised.
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 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 organization, city, or nation.
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. Models
used to carry out such analysis are called Integrated
Assessment Models.
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
on Water 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 policymakers at all levels; 3)
women play a central part in the provision, management and

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safeguarding of water; 4) water has an economic value in all its
competing uses and should be recognized as an economic
good.
Interglacials
The warm periods between ice age glaciations. The previous
interglacial, dated approximately from 129,000 to 116,000
years ago, is referred to as Last Interglacial. (AMS, 2000)
J.
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 United Nations Framework Convention on
Climate Change (UNFCCC)
See also Kyoto Mechanisms; Activities Implemented Jointly.
K.
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 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
Organization 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 to 2012. The
Kyoto Protocol entered into force on 16 February 2005.
L.
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 a 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).
Last Interglacial (LIG)
See Interglacial
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.
Level of Scientific Understanding (LOSU)
This is an index on a 5-step scale (high, medium, medium-low,
low and very low) designed to characterise 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 evidence for the
physical/chemical mechanisms determining the forcing and
the consensus surrounding the quantitative estimate and its
uncertainty.
Likelihood
The likelihood of an occurrence, an outcome or a result, where
this can be estimated probabilistically, is expressed in IPCC
reports using a standard terminology defined as follows:
Terminology
Likelihood of the occurrence
/ outcome
Virtually certain
Very likely
Likely
More likely than not
About as likely as not
Unlikely
Very unlikely
Exceptionally unlikely
>99% probability of occurrence
>90% probability
>66% probability
>50% probability
33 to 66% probability
<33% probability
<10% probability
<1% probability
See also Confidence; Uncertainty
M.
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 of consumption.
Malaria
Endemic or epidemic parasitic disease caused by species of
the genus Plasmodium (Protozoa) and transmitted to humans
by mosquitoes of the genus Anopheles; produces bouts of high
fever and systemic disorders, affects about 300 million and
kills approximately 2 million people worldwide every year.
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 black-market rates may differ significantly and the MER is
difficult to pin down.
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.
Market potential
See Mitigation potential.
Mass balance (of glaciers, ice caps or ice sheets)
The balance between the mass input to an ice body
(accumulation) and the mass loss (ablation, iceberg calving).
Mass balance terms include the following:
Specific mass balance: net mass loss or gain over a
hydrological cycle at a point on the surface of a glacier.
Total mass balance (of the glacier): The specific mass
balance spatially integrated over the entire glacier area; the
total mass a glacier gains or loses over a hydrological cycle.
Mean specific mass balance: The total mass balance per unit
area of the glacier. If surface is specified (specific surface
mass balance, etc.) then ice-flow contributions are not
considered; otherwise, mass balance includes contributions
from ice flow and iceberg calving. The specific surface mass
balance is positive in the accumulation area and negative in
the ablation area.

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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 and tides. Relative sea
level is sea level measured by a tide gauge with respect to the
land upon which it is situated.
See Sea level change/sea level rise.
Measures
Measures are technologies, processes, and practices that
reduce greenhouse gas 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.
Meridional Overturning Circulation (MOC)
A zonally averaged, large scale meridional (north-south)
overturning circulation in the oceans. In the Atlantic such a
circulation transports relatively warm upper-ocean waters
northward, and relatively cold deep waters southward. The
Gulf Stream forms part of this Atlantic circulation.
Methane (CH
4
)
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. 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, may be captured and used as a fuel or for some
other economic purpose (e.g. chemical feedstock).
Metric
A consistent measurement of a characteristic of an object or
activity that is otherwise difficult to quantify.
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.
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 greenhouse gas
emissions and enhance sinks.
Mitigative capacity
This is a country’s ability to reduce anthropogenic greenhouse
gas 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.
Mitigation Potential
In the context of climate change mitigation, the mitigation
potential is the amount of mitigation that could be - but is not
yet– realized over time.
Market potential is the mitigation potential based on private
costs and private discount rates, which might be expected to
occur under forecast market conditions, including policies and
measures currently in place, noting that barriers limit actual
uptake. Private costs and discount rates reflect the perspective
of private consumers and companies.
Economic potential is the mitigation potential that takes into
account social costs and benefits and social discount rates,
assuming that market efficiency is improved by policies and
measures and barriers are removed. Social costs and
discount rates reflect the perspective of society. Social
discount rates are lower than those used by private investors.
Studies of market potential can be used to inform policy
makers about mitigation potential with existing policies and
barriers, while studies of economic potential show what might
be achieved if appropriate new and additional policies were put
into place to remove barriers and include social costs and
benefits. The economic potential is therefore generally greater
than the market potential.
Technical potential is 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. No explicit reference to costs is
made but adopting ‘practical constraints’ may take implicit
economic considerations into account.
Model
See Climate model; Bottom-up model; Top-down model
Model hierarchy
See Climate model
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.
Morbidity
Rate of occurrence of disease or other health disorder within a
population, taking account of the age-specific morbidity rates.
Morbidity indicators include chronic disease incidence/
prevalence, rates of hospitalization, primary care consultations,
disability-days (i.e., days of absence from work), and
prevalence of symptoms.
Mortality
Rate of occurrence of death within a population; calculation of
mortality takes account of age-specific death rates, and can
thus yield measures of life expectancy and the extent of
premature death.
N.
Net market benefits
Climate change, especially moderate climate change, is
expected to bring positive and negative impacts to market-
based sectors, but with significant differences across different
sectors and regions and depending on both the rate and
magnitude of climate change. The sum of the positive and
negative market-based benefits and costs summed across all
sectors and all regions for a given period is called net market
benefits. Net market benefits exclude any non-market impacts.
Nitrous oxide (N
2
O)
One of the six types of greenhouse gases to be curbed 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.
Non-governmental Organization (NGO)
A non-profit group or association organized outside of
institutionalized political structures to realize particular social

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and/or environmental objectives or serve particular
constituencies. Source:
http://www.edu.gov.nf.ca/curriculum/teched/resources/glos-
biodiversity.html
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.
O.
Ocean acidification
A decrease in the pH of sea water due to the uptake of
anthropogenic carbon dioxide.
Opportunities
Circumstances to decrease the gap between the market
potential of any technology or practice and the economic
potential, or technical potential.
Ozone (O
3)
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 (smog). Troposphere ozone
acts as a greenhouse gas. In the stratosphere, ozone is
created by the interaction between solar ultraviolet radiation
and molecular oxygen (O
2
). Stratospheric ozone plays a
dominant role in the stratospheric radiative balance. Its
concentration is highest in the ozone layer.
P.
Paleoclimate
Climate during periods prior to the development of measuring
instruments, including historic and geologic time, for which only
proxy climate records are available.
Patterns 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 Nińo- Southern
Oscillation (ENSO), the Northern Annular Mode (NAM;
previously called Arctic Oscillation, AO) and the Southern
Annular Mode (SAM; previously called the Antarctic
Oscillation, AAO). Many of the prominent modes of climate
variability are discussed in section 3.6 of the Working Group I
Report.
Percentile
A percentile is a value on a scale of zero to one hundred 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 90
th
(10
th
)
percentile may be used to refer to the threshold for the upper
(lower) extremes.
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.
Permafrost
Ground (soil or rock and included ice and organic material) that
remains at or below 0°C for at least two consecutive years
(Van Everdingen, 1998) . See also Frozen ground.
pH
pH is a dimensionless measure of the acidity of water (or any
solution). Pure water has a pH=7. Acid solutions have a pH
smaller than 7 and basic solutions have a pH larger than 7. pH
is measured on a logarithmic scale. Thus, a pH decrease of 1
unit corresponds to a 10-fold increase in the acidity.
Phenology
The study of natural phenomena in biological systems that
recur periodically (e.g., development stages, migration) and
their relation to climate and seasonal changes.
Photosynthesis
The process by which green plants, algae and some bacteria
take carbon dioxide from the air (or bicarbonate in water) to
build carbohydrates. There are several pathways of
photosynthesis with different responses to atmospheric carbon
dioxide concentrations. See Carbon dioxide fertilization.
Plankton
Micro-organisms 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.
Policies
In United Nations Framework Convention on Climate Change
(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
A coherent set of a variety of measures and/or technologies
that policy makers can use to achieve a postulated policy
target. By widening the scope in measures and technologies
more diverse events and uncertainties can be addressed.
Post-SRES (scenarios)
Baseline and mitigation emission scenarios published after
completion of the IPCC Special Report on Emission Scenarios
(SRES) (Nakićenović and Swart, 2000), i.e. after the year
2000.
Pre-industrial
See Industrial revolution.
Projection
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 realised, and are therefore subject to
substantial uncertainty. See also Climate projection; Climate
prediction.
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 (GDP) of countries can be based on

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the purchasing power of currencies rather than on current
exchange rates. PPP estimates tend to lower per capita GDPs
in industrialised countries and raise per capita GDPs in
developing countries.
R.
Radiative forcing
Radiative forcing is the change in the net, downward minus
upward, irradiance (expressed in Watts per square metre,
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.
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 Human-induced
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 forcings like topography, land-use
characteristics, lakes etc., as well as remote influences from
other regions.
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.
Retrofitting
Retrofitting means to install new or modified parts or
equipment, or undertake structural modifications, to existing
infrastructure that were either not available or not considered
necessary at the time of construction. The purpose of
retrofitting in the context of climate change is generally to
ensure that existing infrastructure meets new design
specifications that may be required under altered climate
conditions.
Runoff
That part of precipitation that does not evaporate and is not
transpired, but flows over the ground surface and returns to
bodies of water. See Hydrological cycle
S.
Salinisation
The accumulation of salts in soils.
Saltwater intrusion
Displacement of fresh surface water or groundwater by the
advance of saltwater 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 sea-level rise).
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 SRES scenarios;
Climate scenario; Emission scenarios.
Sea-ice biome
The biome formed by all marine organisms living within or on
the floating sea ice (frozen seawater) of the polar oceans.
Sea ice
Any form of ice found at sea that has originated from the
freezing of sea water. 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 less than one year old is called first-year ice.
Multi-year ice is sea ice that has survived at least one summer
melt season.
Sea level change/sea level rise
Sea level can change, both globally and locally, due to (i)
changes in the shape of the ocean basins, (ii) changes in the
total mass of water and (iii) changes in water density. Factors
leading to sea level rise under global warming include both
increases in the total mass of water from the melting of land-
based snow and ice, and changes in water density from an
increase in ocean water temperatures and salinity changes.
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.
See also Mean Sea Level, Thermal expansion.
Seasonally frozen ground
See Frozen ground
Sensitivity
Sensitivity is the degree to which a system is affected, either
adversely or beneficially, by climate variability or climate
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).
This concept of sensitivity is not to be confused with climate
sensitivity, which is defined separately above.
Singularity
A trait marking one phenomenon or aspect as distinct from
others; something singular, distinct, peculiar, uncommon or
unusual.
Sink
Any process, activity or mechanism which removes a
greenhouse gas, an aerosol or a precursor of a greenhouse
gas or aerosol from the atmosphere.
Snow pack
A seasonal accumulation of slow-melting snow.
Soil temperature
The temperature of the ground near the surface (often within
the first 10 cm).
Solar activity
The Sun exhibits periods of high activity observed in numbers
of sunspots, as well as radiative output, magnetic activity, and

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emission of high energy particles. These variations take place
on a range of time-scales from millions of years to minutes
Solar radiation
Electromagnetic radiation emitted by the Sun. It is also referred
to as short-wave radiation. Solar radiation has a distinctive
range of wavelengths (spectrum) determined by the
temperature of the Sun, peaking in visible wavelengths. See
also Thermal infrared radiation, Total Solar Irradiance
Source
Source mostly refers to any process, activity or mechanism
that releases a greenhouse gas, an aerosol, or a precursor of
a greenhouse gas or aerosol into the atmosphere. Source can
also refer to e.g. an energy source.
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
km
2
), through regional (100,000 to 10 million km
2
) to
continental (10 to 100 million km
2
). Temporal scales may range
from seasonal to geological (up to hundreds of millions of
years).
SRES scenarios
SRES scenarios are emission scenarios developed by
Nakićenović et Swart (2000) and used, among others, as a
basis for some of the climate projections used in the Fourth
Assessment Report. 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 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.
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.
Stabilisation
Keeping constant the atmospheric concentrations of one or
more greenhouse gases (e.g. carbon dioxide) or of a CO2-
equivalent basket of greenhouse gases. Stabilisation analyses
or scenarios address the stabilisation of the concentration of
greenhouse gases in the atmosphere.
Stakeholder
A person or an organization that has a legitimate interest in a
project or entity, or 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). Product, technology or
performance standards establish minimum requirements for
affected products or technologies. Standards impose
reductions in greenhouse gas emissions associated with the
manufacture or use of the products and/or application of the
technology.
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.
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 altitude.
Streamflow
Water flow within a river channel, for example expressed in
m
3
/s. A synonym for river discharge.
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.
Sulphurhexafluoride (SF
6
)
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.
Surface temperature
See Global surface temperature.
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.
T.
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 carbon dioxide, 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 carbon dioxide emissions

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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
agreement. A harmonised tax commits participating countries
to impose a tax at a common rate on the same sources. 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.
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 that leads to
the spreading of technology for adaptation or mitigation The
term encompasses both diffusion of technologies and
technological cooperation across and within countries.
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. See Sea
level change.
Thermal infrared radiation
Radiation emitted by the Earth’s surface, the atmosphere and
the clouds. It is also known as terrestrial 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 colour in the visible part of the spectrum.
The spectrum of thermal infrared radiation is practically distinct
from that of shortwave or solar radiation because of the
difference in temperature between the Sun and the Earth-
atmosphere system.
Tide gauge
A device at a coastal location (and some deep sea locations)
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.
See Sea level change/sea level rise
Top-down models
Top-down model apply 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, like the energy
sector, transportation, agriculture, and industry. Some top-
down models incorporate technology data, narrowing the gap
to bottom-up models.
Total Solar Irradiance (TSI)
The amount of solar radiation 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 1,368 Watts per square meter (W
m
−2
) with an accuracy of about 0.2%. 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 on the order of 0.1%. Source: AMS, 2000.
Tradable permit
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. 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.
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 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.
U.
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, for example, a range of values
calculated by various models, or by qualitative statements, for
example, reflecting the judgement of a team of experts (see
Moss and Schneider, 2000; Manning et al., 2004). See also
Likelihood; Confidence.
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 member countries in the
year 1990 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. See 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.

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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.
V.
Vector
An organism, such as an insect, that transmits a pathogen
from one host to another.
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.
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.
W.
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 stress
A country is water stressed if the available freshwater supply
relative to water withdrawals acts as an important constraint on
development. In global-scale assessments, basins with water
stress are often defined as having a per capita water
availability below 1,000 m
3
/yr (based on long-term average
runoff). Withdrawals exceeding 20% of renewable water supply
have also 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.
Z.
Zooplankton
See Plankton
References
Glossaries of the contributions of Working Groups I, II and III to
the IPCC Fourth Assessment Report.
AMS, 2000: AMS Glossary of Meteorology, 2nd Ed. American
Meteorological Society, Boston, MA,
http://amsglossary.allenpress.com/glossary/browse.
Cleveland C.J. and C. Morris, 2006: Dictionary of Energy,
Elsevier, Amsterdam, 502p
Heim, R.R., 2002: A Review of Twentieth-Century Drought
Indices Used in the United States. Bull. Am. Meteorol.
Soc., 83, 1149–1165
IPCC, 1996: Climate Change 1995: The Science of Climate
Change. Contribution of Working Group I to the Second
Assessment Report of the Intergovernmental Panel on
Climate Change [Houghton., J.T., et al. (eds.)].
Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA, 572 pp.
IPCC, 2000: Land Use, Land-Use Change, and Forestry.
Special Report of the Intergovernmental Panel on
Climate Change [Watson, R.T., et al. (eds.)]. Cambridge
University Press, Cambridge, United Kingdom and New
York, NY, USA, 377 pp.
IPCC, 2003: Definitions and Methodological Options to
Inventory Emissions from Direct Human-Induced
Degradation of Forests and Devegetation of Other
Vegetation Types [Penman, J., et al. (eds.)]. The Institute
for Global Environmental Strategies (IGES), Japan , 32
pp.
IUCN, 1980: The World Conservation Strategy: living resource
conservation for sustainable development, Gland,
Switzerland, IUCN/UNEP/WWF.
Manning, M., et al., 2004: IPCC Workshop on Describing
Scientific Uncertainties in Climate Change to Support
Analysis of Risk of Options. Workshop Report.
Intergovernmental Panel on Climate Change, Geneva.
Moss, R., and S. Schneider, 2000: Uncertainties in the IPCC
TAR: Recommendations to Lead Authors for More
Consistent Assessment and Reporting. In: IPCC
Supporting Material: Guidance Papers on Cross Cutting
Issues in the Third Assessment Report of the IPCC.
[Pachauri, R., T. Taniguchi, and K. Tanaka (eds.)].
Intergovernmental Panel on Climate Change, Geneva,
pp. 33–51.
Nakićenović, N., and R. Swart (eds.), 2000: Special Report on
Emissions Scenarios. A Special Report of Working
Group III of the Intergovernmental Panel on Climate
Change. Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA, 599 pp.
Van Everdingen, R. (ed.): 1998. Multi-Language Glossary of
Permafrost and Related Ground-Ice Terms, revised May
2005. National Snow and Ice Data Center/World Data
Center for Glaciology, Boulder, CO,
http://nsidc.org/fgdc/glossary/.
A.3. Acronyms, chemical symbols, scientific units, country groupings
3.1
Acronyms and chemical symbols
A1
A family of scenarios in the IPCC Special
Report on Emission Scenarios; see glossary
under SRES scenarios
A1T
One of the six SRES marker scenarios; see
glossary under SRES scenarios
A1B
One of the six SRES marker scenarios; see
glossary under SRES scenarios
A1FI
One of the six SRES marker scenarios; see
glossary under SRES scenarios
A2
A family of scenarios in the IPCC Special
Report on Emission Scenarios; also one of
the six SRES marker scenarios; see
glossary under SRES scenarios

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AOGCM Atmosphere-Ocean General Circulation
Model; see glossary under climate model
B1
A family of scenarios in the IPCC Special
Report on Emission Scenarios; also denotes
one of the six SRES marker scenarios; see
glossary under SRES scenarios
B2
A family of scenarios in the IPCC Special
Report on Emission Scenarios; also denotes
one of the six SRES marker scenarios; see
glossary under SRES scenarios
CH
4
Methane; see glossary
CFC
Chlorofluorocarbon; see glossary
CO
2
Carbon dioxide; see glossary
EIT
Economies in transition; see glossary
EMIC
Earth Model of Intermediate Complexity
ENSO
El Nińo-Southern Oscillation; see glossary
F-Gases Fluorinated gases covered under the Kyoto
Protocol; see glossary
GDP
Gross domestic product
HCFC
Hydrochlorofluorocarbon; see glossary
HFC
Hydrofluorocarbon; see glossary
LOSU
Level of scientific understanding; see
glossary
MOC
Meridional overturning circulation; see
glossary
N
2
O
Nitrous oxide; see glossary
OECD
Organisation for Economic Cooperation and
Development; see www.oecd.org
PFC
Perfluorocarbon; see glossary
pH
See glossary under pH
PPP
Purchasing power parity; see glossary
RD&D
Research, development and demonstration
SCM
Simple Climate Model
SF
6
Sulfur hexafluoride; see glossary
SRES
Special Report on Emission Scenarios; see
glossary under SRES scenarios
UNFCCC United Nations Framework Convention on
Climate Change; see www.unfccc.int
3.2
Scientific units
SI (Systčme Internationale) units
Physical Quantity
Name of Unit
Symbol
length
metre
m
mass
kilogram
kg
time
second
s
thermodynamic temperature
kelvin
K
Fractions and multiples
Fraction
Prefix
Symbol
Multiple
Prefix
Symbol
10
-1
deci
d
10
deca
da
10
-2
centi
c
10
2
hecto
h
10
-3
milli
m
10
3
kilo
k
10
-6
micro
µ
10
6
mega
M
10
-9
nano
n
10
9
giga
G
10
-12
pico
p
10
12
tera
T
10
-15
femto
f
10
15
peta
P
Non-SI units, quantities and related abbreviations
°C
degree Celsius (0°C = 273 K approximately); temperature differences are also given in °C (=K) rather
than the more correct form of “Celsius degrees”
ppm
mixing ratio (as concentration measure of GHGs): parts per million (10
6
) by volume
ppb
mixing ratio (as concentration measure of GHGs): parts per billion (10
9
) by volume
ppt
mixing ratio (as concentration measure of GHGs): parts per trillion (10
12
) by volume
watt
power or radiant flux; 1 watt = 1 Joule / second = 1 kg m
2
/ s
3
yr
year
ky
thousands of years
bp
before present
GtC
gigatonnes (metric) of carbon
GtCO
2
gigatonnes (metric) of carbon dioxide (1 GtC = 3.7 GtCO
2
)
CO
2
-eq
carbon dioxide-equivalent, used as measure for the emission (generally in GtCO2-eq) or concentration
(generally in ppm CO
2
-eq) of GHGs; see Box “Carbon dioxide-equivalent emissions and
concentrations” in Topic 2 for details

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3.3
Country groupings
For the full set of countries belonging to UNFCCC Annex I, non-Annex I, and OECD, see http://www.unfccc.int
and http://www.oecd.org.
Where relevant in this report, countries have been grouped into regions according to the classification of the
UNFCCC and its Kyoto Protocol. Countries that have joined the European Union since 1997 are therefore still
listed under EIT Annex I. The countries in each of the regional groupings employed in this report include:
*
EIT Annex I: Belarus, Bulgaria, Croatia, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland,
Romania, Russian Federation, Slovakia, Slovenia, Ukraine
Europe Annex II & M&T: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland,
Ireland, Italy, Liechtenstein, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland,
United Kingdom; Monaco and Turkey
JANZ: Japan, Australia, New Zealand.
Middle East: Bahrain, Islamic Republic of Iran, Israel, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi
Arabia, Syria, United Arab Emirates, Yemen
Latin America & the Caribbean: Antigua & Barbuda, Argentina, Bahamas, Barbados, Belize, Bolivia,
Brazil, Chile, Colombia, Costa Rica, Cuba, Dominica, Dominican Republic, Ecuador, El Salvador,
Grenada, Guatemala, Guyana, Haiti, Honduras, Jamaica, Mexico, Nicaragua, Panama, Paraguay, Peru,
Saint Lucia, St. Kitts-Nevis-Anguilla, St. Vincent-Grenadines, Suriname, Trinidad and Tobago, Uruguay,
Venezuela
Non-Annex I East Asia: Cambodia, China, Korea (DPR), Laos (PDR), Mongolia, Republic of Korea,
Viet Nam.
South Asia: Afghanistan, Bangladesh, Bhutan, Comoros, Cook Islands, Fiji, India, Indonesia, Kiribati,
Malaysia, Maldives, Marshall Islands, Micronesia, (Federated States of), Myanmar, Nauru, Niue, Nepal,
Pakistan, Palau, Papua New Guinea, Philippine, Samoa, Singapore, Solomon Islands, Sri Lanka,
Thailand, Timor-L’Este, Tonga, Tuvalu, Vanuatu
North America: Canada, United States of America.
Other non-Annex I: Albania, Armenia, Azerbaijan, Bosnia Herzegovina, Cyprus, Georgia, Kazakhstan,
Kyrgyzstan, Malta, Moldova, San Marino, Serbia, Tajikistan, Turkmenistan, Uzbekistan, Republic of
Macedonia
Africa: Algeria, Angola, Benin, Botswana, Burkina Faso, Burundi, Cameroon, Cape Verde, Central
African Republic, Chad, Congo, Democratic Republic of Congo, Côte d’Ivoire, Djibouti, Egypt, Equatorial
Guinea, Eritrea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Lesotho, Liberia,
Libya, Madagascar, Malawi, Mali, Mauritania, Mauritius, Morocco, Mozambique, Namibia, Niger,
Nigeria, Rwanda, Sao Tome and Principe, Senegal, Seychelles, Sierra Leone, South Africa, Sudan,
Swaziland, Togo, Tunisia, Uganda, United Republic of Tanzania, Zambia, Zimbabwe
*
A full set of data for all countries for 2004 for all regions was not available.

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A.4. List of authors
If country/countries of residence is/are different from nationality, nationality is mentioned last.
4.1
Core Writing Team members
Bernstein, Lenny
L.S. Bernstein & Associates, L.L.C.
USA
Bosch, Peter
IPCC WGIII TSU, Ecofys Netherlands, and
Netherlands Environmental Assessment Agency
THE NETHERLANDS
Canziani, Osvaldo
IPCC WGII Co-chair, Buenos Aires
ARGENTINA
Chen, Zhenlin
Dept. of International Cooperation, China
Meteorological Administration
CHINA
Christ, Renate
Secretariat, Intergovernmental Panel on Climate
Change (IPCC)
SWITZERLAND/AUSTRIA
Davidson, Ogunlade
IPCC WGIII Co-chair, Faculty of Engineering,
University of Sierra Leone
SIERRA LEONE
Hare, William
Potsdam Institute for Climate Impact Research
GERMANY/AUSTRALIA
Huq, Saleemul
International Institute for Environment and
Development (IIED)
UK/BANGLADESH
Karoly, David
School of Meteorology, University of Oklahoma,
USA, and University of Melbourne, Australia
USA/AUSTRALIA
Kattsov, Vladimir
Voeikov Main Geophysical Observatory
RUSSIA
Kundzewicz, Zbyszek
Research Centre for Agricultural & Forest
Environment, Polish Academy of Sciences
POLAND
Liu, Jian
Secretariat, Intergovernmental Panel on Climate
Change (IPCC)
SWITZERLAND/CHINA
Lohmann, Ulrike
Institute of Atmospheric and Climate Science,
Eidgenössische Technische Hochschule (ETH)
SWITZERLAND
Manning, Martin
IPCC WGI TSU, University Corporation for
Atmospheric Research
USA/NEW ZEALAND
Matsuno, Taroh
Frontier Research Center for Global Change
JAPAN
Menne, Bettina
European Centre for Environment and Health,
World Health Organization (WHO)
ITALY
Metz, Bert
IPCC WGIII Co-chair, Global Environmental
Assessment Division, Netherlands Environmental
Assessment Agency
THE NETHERLANDS
Mirza, Monirul
Adaptation & Impacts Research Division (AIRD),
Environment Canada, and Department of Physical
and Environmental Sciences, University of Toronto
CANADA/BANGLADESH
Nicholls, Neville
School of Geography & Environmental Science,
Monash University
AUSTRALIA
Nurse, Leonard
Barbados Centre for Resource Management and
Environmental Studies, University of West Indies
BARBADOS
Pachauri, Rajendra
The Energy and Resources Institute (TERI)
INDIA
Palutikof, Jean
IPCC WGII TSU, Met Office Hadley Centre
UK
Parry, Martin
IPCC WGII Co-chair, Met Office Hadley Centre, and
Centre for Environmental Policy, Imperial College,
University of London
UK
Qin, Dahe
IPCC WGI Co-chair, China Meteorological
Administration
CHINA
Ravindranath, Nijavalli
Centre for Ecological Sciences, Indian Institute of
Science
INDIA

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Reisinger, Andy
IPCC SYR TSU, Met Office Hadley Centre, UK, and
The Energy and Resources Institute (TERI), India
UK/INDIA/GERMANY
Ren, Jiawen
Cold and Arid Regions Environment and
Engineering Research Institute, Chinese Academy
of Sciences
CHINA
Riahi, Keywan
International Institute for Applied Systems Analysis
(IIASA), and University of Vienna
AUSTRIA
Rosenzweig, Cynthia
Goddard Institute for Space Studies, National
Aeronautics and Space Administration (NASA)
USA
Rusticucci, Matilde
Ciencias de la Atmósfera y los Océanos,
Universidad de Buenos Aires
ARGENTINA
Schneider, Stephen
Department of Biological Sciences, Stanford
University
USA
Sokona, Youba
Sahara and Sahel Observatory (OSS)
TUNISIA/MALI
Solomon, Susan
IPCC WGI Co-chair, NOAA Earth System Research
Laboratory
USA
Stott, Peter
Met Office Hadley Centre
UK
Stouffer, Ronald
NOAA Geophysical Fluid Dynamics Laboratory,
Princeton University
USA
Sugiyama, Taishi
Climate Policy Project, Central Research Institute of
Electric Power Industry (CRIEPI)
JAPAN
Swart, Rob
Netherlands Environmental Assessment Agency
THE NETHERLANDS
Tirpak, Dennis
Environment Directorate, OECD, and International
Institute for Sustainable Development (IISD),
Winnipeg, Canada
FRANCE/USA
Vogel, Coleen
Department of Geography, University of
Witwatersrand
SOUTH AFRICA
Yohe, Gary
Department of Economics, Wesleyan University
USA
4.2
Extended Writing Team member
Barker, Terry
Cambridge Centre for Climate Change Mitigation
Research, University of Cambridge
UK
A.5. List of reviewers and Review Editors
5.1
Reviewers
Consistent with IPCC Rules and Procedures, the draft SYR was sent for formal review to over 2,400
individual experts as well as to the 193 member governments of the IPCC. This appendix lists the
individual experts who submitted review comments during the joint expert and government review of
the draft SYR either as individual experts or as part of a managed government review, and whose
comments were considered by the Core Writing Team in its revision of the draft report.
[reviewers to be included after IPCC-27]
5.2
Review Editors
The role of Review Editors is to ensure that all substantive expert and government review comments
are afforded appropriate consideration by the Core Writing Team. Two Review Editors were
appointed for each topic of the Longer Report of the Synthesis Report, and they confirm that all
comments were considered in accordance with IPCC procedures.

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Topic 1
Jallow, Bubu Pateh
Department of Water Resources
THE GAMBIA
Kajfež-Bogataj , Lučka
University of Ljubljana
SLOVENIA
Topic 2
Bojariu, Roxana
National Institute of Meteorology and Hydrology
ROMANIA
Hawkins, David
NRDC Climate Center
USA
Topic 3
Diaz, Sandra
CONICET-Universidad Nacional de Córdoba
ARGENTINA
Lee, Hoesung
SOUTH KOREA
Topic 4
Allali, Abdelkader
Ministry of Agriculture, Rural Development and
Fishing
MOROCCO
Elgizouli, Ismail
Higher Council for Environment & Natural Resources
SUDAN
Topic 5
Wratt, David
National Institute of Water and Atmospheric Research
NEW ZEALAND
Hohmeyer, Olav
University of Flensburg
GERMANY
Topic 6
Griggs, Dave
Monash University
AUSTRALIA/UK
Leary, Neil
International START Secretariat
USA
A.6. Index
[index to be included after IPCC-27]