Climate change is a complex topic often using
difficult and confusing words or phrases. The following terms have
been gathered from many sources including the National Oceanic and
Atmospheric Administration (NOAA), Intergovernmental Panel on
Climate Change (IPCC), and others. Included are the most commonly
referred to terms in climate change literature and news
A | B | C | D | E | F | G | H | I | J | K | L | M
N | O | P | Q |
R | S | T | U | V | W | X | Y | Z
The physiological adaptation to climatic
See Adaptive capacity.
Adjustment in natural or human systems to a new
or changing environment. Adaptation to climate change refers to
adjustment in natural or human systems in response to actual or
expected climatic stimuli or their effects, which moderates harm or
exploits beneficial opportunities. Various types of adaptation can
be distinguished, including anticipatory and reactive adaptation,
private and public adaptation, and autonomous and planned
The practice of identifying options to adapt to
climate change and evaluating them in terms of criteria such as
availability, benefits, costs, effectiveness, efficiency, and
The avoided damage costs or the accrued benefits
following the adoption and implementation of adaptation
Costs of planning, preparing for, facilitating,
and implementing adaptation measures, including transition
The ability of a system to adjust to climate
change (including climate variability and extremes) to moderate
potential damages, to take advantage of opportunities, or to cope
with the consequences.
Reduction in emissions by sources or enhancement
of removals by sinks that is additional to any that would occur in
the absence of a Joint Implementation or a Clean Development
Mechanism project activity as defined in the Kyoto Protocol
Articles on Joint Implementation and the Clean Development
Mechanism. This definition may be further broadened to include
financial, investment, and technology additionality. Under
"financial additionality," the project activity funding shall be
additional to existing Global Environmental Facility, other
financial commitments of Parties included in Annex I, Official
Development Assistance, and other systems of cooperation. Under
"investment additionality," the value of the Emissions Reduction
Unit/Certified Emission Reduction Unit shall significantly improve
the financial and/or commercial viability of the project activity.
Under "technology additionality," the technology used for the
project activity shall be the best available for the circumstances
of the host Party.
See response time.
A collection of airborne solid or liquid
particles, with a typical size between 0.01 and 10 mm that reside
in the atmosphere for at least several hours. Aerosols may be of
either natural or anthropogenic origin. Aerosols may influence
climate in two ways: directly through scattering and absorbing
radiation, and indirectly through acting as condensation nuclei for
cloud dormation or modifying the optical properties and lifetime of
clouds. See indirect aerosol effect.
Planting of new forests on lands that
historically have not contained forests.
A reproductive explosion of algae in a lake,
river, or ocean.
The biogeographic zone made up of slopes above
timberline and characterized by the presence of rosette-forming
herbaceous plants and low shrubby slow-growing woody plants.
Energy derived from non-fossil-fuel sources.
Complementary benefits of a climate policy
including improvements in local air quality and reduced reliance of
imported fossil fuels.
Resulting from or produced by human beings.
Emissions of greenhouse gases, greenhouse gas
precursors, and aerosols associated with human activities. These
include burning of fossil fuels for energy, deforestation, and
land-use changes that result in net increase in emissions.
Under an emissions trading scheme, permits to
emit can initially either be given away for free, usually under a
'grandfathering' approach based on past emissions in a base year or
an 'updating' approach based on the more recent emissions. The
alternative is to auction permits in an initial market
A stratum of permeable rock that bears water. An
unconfined aquifer is recharged directly by local rainfall, rivers,
and lakes, and the rate of recharge will be influenced by the
permeability of the overlying rocks and soils. A confined aquifer
is characterized by an overlying bed that is impermeable andthe
local rainfall does not influence the aquifer.
Ecosystems with less than 250 mm precipitation
The gaseous envelop surrounding the Earth. The
dry atmosphere consists almost entirely of nitrogen (78.1% volume
mixingratio) and oxygen (20.9% volume mixing ratio), together with
a number of trace gases, such as argon (0.93% volume mixingratio),
helium, and radiatively active greenhouse gases such as carbon
dioxide (0.035% volume mixing ratio) and ozone. In addition, the
atmosphere contains water vapor, whose amount is highly variable
but typically 1% volume mixing ratio. The atmosphere also contains
clouds and aerosols.
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The numbers and relative abundances of different
genes (genetic diversity), species, and ecosystems (communities) in
a particular area.
A fuel produced from dry organic matter or
combustible oils produced by plants. Examples of biofuel include
alcohol (from fermented sugar), black liquor from the paper
manufacturing process, wood, and soybean oil.
The total mass of living organisms in a given
area or volume; recently dead plant material is often included as
Operationally defined species based on
measurement of light absorption and chemical reactivity and/or
thermal stability; consists of soot, charcoal, and/or possible
light-absorbing refractory organic matter.
A poorly drained area rich in accumulated plant
material, frequently surrounding a body of open water and having a
characteristic flora (such as sedges, heaths, and sphagnum).
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.
A modeling approach that includes technological
and engineering details in the analysis. See also top-down
The total mass of a gaseous substance of concern
in the atmosphere.
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In the context of climate change, capacity
building is a process of developing the technical skills and
institutional capability in developing countries and economies in
transition to enable them to participate in all aspects of
adaptation to, mitigation of, and research on climate change, and
the implementation of the Kyoto Mechanisms, etc.
Aerosol consisting predominantly of organic
substances and various forms of black carbon.
A permit that allows an entity to emit a
specified amount of greenhouse gases. Also called emission permit.
Buying a carbon credit is like building a credit reserve for later
withdrawal of some type.
The term used to describe the flow of carbon (in
various forms such as carbon dioxide) through the atmosphere,
ocean, terrestrial biosphere, and lithosphere.
Carbon dioxide (CO2)
A naturally occurring gas, and also a by-product
of burning fossil fuels and biomass, as well as land-use changes
and other industrial processes. It is the principal anthropogenic
greenhouse gas that affects the Earth's radiative balance. It is
the reference gas against which other greenhouse gases are measured
and therefore has a Global Warming Potential of 1.
Carbon dioxide (CO2)
The enhancement of the growth of plants as a
result of increased atmospheric carbon dioxide concentration.
Depending on their mechanism of photosynthesis, certain types of
plants are more sensitive to changes in atmospheric carbon dioxide
concentration. In particular, plants that produce a three-carbon
compound (C3)during photosynthesis-including most trees and
agricultural crops such as rice, wheat, soybeans, potatoes, and
vegetables-generally show a larger response than plants that
produce a four-carbon compound (C4) during photosynthesis-mainly of
tropical origin, including grasses and the agriculturally important
crops maize, sugar cane, millet, and sorghum.
The amount of carbon an entity of any type (e.g.,
person, group, vehicle, event, building, corporation) emits into
A system for buying, selling and trading carbon
credits. The regulatory carbon market is based on government
regulations such as international Kyoto accords, or recent
legislation in California. A voluntary carbon market refers to
systems for trading carbon offsets as opposed to carbon credits
Being carbon neutral involves calculating your
total climate-damaging carbon emissions, reducing them where
possible, and then balancing your remaining emissions, often by
purchasing a carbon offset.
Paying to plant new trees or investing in "green"
technologies such as solar and wind power. Often these payments are
a monetary donation to an environmental fund and/or endowment.
Anything sequestering carbon such as trees and
other vegetation, forests, oceans and grasslands.
Anything emitting carbon into the atmosphere
including forest fires, car exhaust, factories, livestock.
A tax on energy sources which emit carbon dioxide
into the atmosphere.
An area that collects and drains rainwater.
Greenhouse gases covered under the 1987 Montreal
Protocol and used for refrigeration, air conditioning, packaging,
insulation, solvents, or aerosol propellants. Since they are not
destroyed in the lower atmosphere, CFCs drift into the upper
atmosphere where, given suitable conditions, they break down ozone.
These gases are being replaced by other compounds, including
hydrochlorofluorocarbons and hydrofluorocarbons, which are
greenhouse gases covered under the Kyoto Protocol.
Climate in a narrow sense is usually defined as
the "average weather" or more rigorously as the statistical
description in terms of the mean and variability of relevant
quantities over a period of time ranging from months to thousands
or millions of years. The classical period is 30 years, as defined
by the World Meteorological Organization (WMO). These relevant
quantities are most often surface variables such as temperature,
precipitation, and wind. Climate in a wider sense is the state,
including a statistical description, of the climate system.
Climate change refers to a statistically
significant variation in either the mean state of the climate or in
its variability, persisting for an extended period (typically
decades or longer). Climate change may be due to natural internal
processes or external forcings, or to persistent anthropogenic
changes in the composition of the atmosphere or in land use.
Note that the United Nations Framework Convention
on Climate Change (UNFCCC), in its Article 1, defines "climate
change" as: "a change of climate which is attributed directly or
indirectly to human activity that alters the composition of the
global atmosphere and which is in addition to natural climate
variability observed over comparable time periods." The UNFCCC thus
makes a distinction between "climate change" attributable to human
activities altering the atmospheric composition, and "climate
variability" attributable to natural causes. See also climate
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 (hierarchy)
A numerical representation of the climate system
based on the physical, chemical, and biological properties of its
components, their interactions and feedback processes, and
accounting for all or some of its known properties. The climate
system can be represented by models of varying complexity-that is,
for anyone component or combination of components a "hierarchy" of
models can be identified, differing in such aspects as the number
of spatial dimensions, the extent to which physical, chemical or
biological processes are explicitly represented, or the level at
which empirical parametrizations are involved. Coupled
atmosphere/ocean/sea-ice general circulation models (AOGCMs)
provide a comprehensive representation of the climate system. There
is an evolution towards more complex models with active chemistry
and biology. Climate models are applied, as a research tool, to
study and simulate the climate, but also for operational purposes,
including monthly, seasonal, and interannual climate
A climate prediction or climate forecast is the
result of an attempt to produce a most likely description or
estimate of the actual evolution of the climate in the future
(e.g., at seasonal, interannual, or long-term time-scales). See
also climate projection and climate scenario.
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, futures CIO-economic
and technological developments that may or may not be realized, and
are therefore subject to substantial uncertainty.
A plausible and often simplified representation
of the future climate, based on an internally consistent set of
climatological relationships, that has been constructed for
explicit use in investigating the potential consequences of
anthropogenic climate change, often serving as input to impact
models. Climate projections often serve as the raw material for
constructing climate scenarios, but climate scenarios usually
require additional information such as about the observed current
climate. A "climate change scenario" is the difference between a
climate scenario and the current climate.
The climate system is the highly complex system
consisting of five major components: the atmosphere, the
hydrosphere, the cryosphere, the land surface and the biosphere,
and the interactions between them. The climate system evolves in
time under the influence of its own internal dynamics and because
of external forcings such as volcanic eruptions, solar variations,
and human-induced forcings such as the changing composition of the
atmosphere and land-use change.
Climate variability refers to variations in the
mean state and other statistics (such as standard deviations, the
occurrence of extremes, etc.) of the climate on all temporal and
spatial scales beyond that of individual weather events.
Variability may be due to natural internal processes within the
climate system (internal variability), or to variations in natural
or anthropogenic external forcing (external variability). See also
The benefits of policies that are implemented for
various reason sat the same time-including climate change
mitigation-acknowledging that most policies designed to address
greenhouse gas mitigation also have other, often at least equally
important, rationales (e.g., related to objectives of development,
sustainability, and equity). The term co-impact is also used in a
more generic sense to cover both the positive and negative sides of
the benefits. See also ancillary benefits.
The use of waste heat from electric generation,
such as exhaust from gas turbines, for either industrial purposes
or district heating.
The variation in climatic stimuli that a system
can absorb without producing significant impacts.
The paling in color of corals resulting from a
loss of symbiotic algae. Bleaching occurs in response to
physiological shock in response to abrupt changes in temperature,
salinity, and turbidity.
A criterion that specifies that a technology or
measure delivers a good or service at equal or lower cost than
current practice, or the least-cost alternative for the achievement
of a given target.
The component of the climate system consisting of
all snow, ice, and permafrost on and beneath the surface of the
earth and ocean. See also glacier and ice sheet.
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Occurs when seawater freezes to form sea ice. The
local release of salt and consequent increase in water density
leads to the formation of saline coldwater that sinks to the ocean
Conversion of forest to non-forest.
Combines a deposit or fee (tax) on a commodity
with a refund or rebate (subsidy) for implementation of a specified
An ecosystem with less than 100 mm precipitation
Land degradation in arid, semi-arid, and dry
sub-humid areas resulting from various factors, including climatic
variations and human activities. Further, the United Nations
Convention to Combat Desertification defines land degradation as a
reduction or loss in arid, semi-arid, and dry sub-humid areas of
the biological or economic productivity and complexity of rain-fed
cropland, irrigated cropland, or range, pasture, forest, and
woodlands resulting from land uses or from a process or combination
of processes, including processes arising from human activities and
habitation patterns, such as: (i) soil erosion caused by wind
and/or water; (ii) deterioration of the physical, chemical, and
biological or economic properties of soil; and (iii) long-term loss
of natural vegetation.
Detection and attribution
Climate varies continually on all time scales.
Detection of climate change is the process of demonstrating that
climate has changed in some defined statistical sense, without
providing a reason for that change. Attribution of causes of
climate change is the process of establishing the most likely
causes for the detected change with some defined level of
Frequency, intensity, and types of disturbances,
such as fires, inspect or pest outbreaks, floods, and droughts.
Diurnal temperature range
The difference between the maximum and minimum
temperature during a day.
The phenomenon that exists when precipitation has
been significantly below normal recorded levels, causing serious
hydrological imbalances that adversely affect land resource
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Economic potential is the portion of
technological potential for greenhouse gas emissions reductions or
energy efficiency improvements that could be achieved
cost-effectively through the creation of markets, reduction of
market failures, or increased financial and technological
transfers. The achievement of economic potential requires
additional policies and measures to break down market barriers. See
also market potential, socio-economic potential, and technological
A system of interacting living organisms together
with their physical environment. The boundaries of what could be
called an ecosystem are somewhat arbitrary, depending on the focus
of interest or study. Thus, the extent of an ecosystem may range
from very small spatial scales to, ultimately, the entire
Ecological processes or functions that have value
to individuals or society.
El Niño Southern Oscillation
El Niño, in its original sense, is a warmwater
current that periodically flows along the coast of Ecuador and
Peru, disrupting the local fishery. This oceanic event is
associated with a fluctuation of theintertropical surface pressure
pattern and circulation in the Indian and Pacific Oceans, called
the Southern Oscillation. This coupled atmosphere-ocean phenomenon
is collectively known as El Niño Southern Oscillation, or ENSO.
During an El Niño event, the prevailing trade winds weaken and the
equatorial countercurrent strengthens, causing warm surface waters
in the Indonesian area to flow eastward to overlie the cold waters
of the Peru current. This event has great impact on the wind, sea
surface temperature, and precipitation patterns in the tropical
Pacific. It has climatic effects throughout the Pacific region and
in many other parts of the world. The opposite of an El Niño event
is called La Niña.
In the climate change context, emissions refer to
the release of greenhouse gases and/or their precursors and
aerosols into the atmosphere over a specified area and period of
An emissions permit is the non-transferable or
tradable allocation of entitlements by an administrative authority
(intergovernmental organization, central or local government
agency) to a regional (country, sub-national) or a sectoral (an
individual firm) entity to emit a specified amount of a
The portion or share of total allowable emissions
assigned to a country or group of countries within a framework of
maximum total emissions and mandatory allocations of resources.
Emissions Reduction Unit
Equal to 1 tonne (metric ton) of carbon dioxide
emissions reduced or sequestered arising from a Joint
Implementation (defined in Article 6 of the Kyoto Protocol) project
calculated using Global Warming Potential. See also Certified
Emission Reduction Unit and emissions trading.
Levy imposed by a government on each unit of
CO2-equivalent emissions by a source subject to the tax. Since
virtually all of the carbon in fossil fuels is ultimately emitted
as carbon dioxide, a levy on the carbon content of fossil fuels-a
carbon tax-is equivalent to an emissions tax for emissions caused
by fossilfuel combustion. An energy tax-a levy on the energy
content of fuels-reduces demand for energy and so reduces carbon
dioxide emissions from fossil-fuel use. An ecotax is designated for
the purpose of influencing human behavior (specifically economic
behavior) to follow an ecologically benign path. International
emissions/carbon/energy tax is a tax imposed on specified sources
in participating countries by an international agency. The revenue
is distributed or used as specified by participating countries or
the international agency.
A market-based approach to achieving
environmental objectives that allows, those reducing greenhouse gas
emissions below what is required, to use or trade the excess
reductions to offset emissions at another source inside or outside
the country. In general, trading can occur at the intracompany,
domestic, and international levels.
Ratio of energy output of a conversion process or
of a system to its energy input.
Energy intensity is the ratio of energy
consumption to economic or physical output. At the national level,
energy intensity is the ratio of total domestic primary energy
consumption or final energy consumption to Gross Domestic Product
or physical output.
The application of useful energy to tasks desired
by the consumer such as transportation, a warm room, or light.
The change from one form of energy, such as the
energy embodied in fossil fuels, to another, such as
Environmentally Sound Technologies
Technologies that protect the environment, are
less polluting, use all resources in a more sustainable manner,
recycle more of their wastes and products, and handle residual
wastes in a more acceptable manner than the technologies for which
they were substitutes and are compatible with nationally determined
socio-economic, cultural, and environmental priorities. ESTs in
this report imply mitigation and adaptation technologies, hard and
Equivalent CO2 (carbon
The concentration of carbon dioxide that would
cause the same amount of radiative forcing as a given mixture of
carbon dioxide and other greenhouse gases.
The process of removal and transport of soil and
rock by weathering, mass wasting, and the action of streams,
glaciers, waves, winds, and underground water.
Eustatic sea-level change
A change in global average sea level brought
about by an alteration to the volume of the world ocean. This may
be caused by changes in water density or in the total mass of
water. In discussions of changes on geological time scales, this
term sometimes also includes changes in global average sea level
caused by an alteration to the shape of the ocean basins. In this
report, the term is not used in that sense.
The process by which a liquid becomes a gas.
The combined process of evaporation from the
Earth's surface and transpiration from vegetation.
The nature and degree to which a system is
exposed to significant climatic variations.
Used to define the costs arising from any human
activity, when the agent responsible for the activity does not take
full account of the impacts on others of his or her actions.
Equally, when the impacts are positive and not accounted for in the
actions of the agent responsible they are referred to as external
benefits. Emissions of particulate pollution from a power station
affect the health of people in the vicinity, but this is not often
considered, or is given inadequate weight, in private decision
making and there is no market for such impacts. Such a phenomenon
is referred to as an "externality," and the costs it imposes are
referred to as the external costs.
Extreme weather event
An extreme weather event is an event that is rare
within its statistical reference distribution at a particular
place. Definitions of "rare" vary, but an extreme weather event
would normally be as rare as or rarer than the 10th or 90th
percentile. By definition, the characteristics of what is called
extreme weather may vary from place to place. An extreme climate
event is an average of a number of weather events over a certain
period of time, an average which is itself extreme (e.g., rainfall
over a season).
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Energy supplied that is available to the consumer
to be converted into usable energy (e.g., electricity at the wall
A situation that exists when people lack secure
access to sufficient amounts of safe and nutritious food for normal
growth and development and an active and healthy life. It may be
caused by the unavailability of food, insufficient purchasing
power, inappropriate distribution, or inadequate use of food at the
household level. Food insecurity may be chronic, seasonal, or
A vegetation type dominated by trees. Many
definitions of the term forest are in use throughout the world,
reflecting wide differences in bio-geophysical conditions, social
structure, and economics. For a discussion of the term forest and
related terms such as afforestation, reforestation, and
Fossil CO2 (carbon dioxide)
Emissions of carbon dioxide resulting from the
combustion of fuels from fossil carbon deposits such as oil,
natural gas, and coal.
Carbon-based fuels from fossil carbon deposits,
including coal, oil, and natural gas.
Policy designed to reduce carbon dioxide
emissions by switching to lower carbon-content fuels, such as from
coal to natural gas.
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The large scale motions of the atmosphere and the
ocean as a consequence of differential heating on a rotating Earth,
aiming to restore the energy balance of the system through
transport of heat and momentum.
Efforts to stabilize the climate system by
directly managing the energy balance of the Earth, thereby
overcoming the enhanced greenhouse effect.
A mass of land ice flowing downhill (by internal
deformation and sliding at the base) and constrained by the
surrounding topography (e.g., the sides of a valley or surrounding
peaks); the bedrock topography is the major influence on the
dynamics and surface slope of a glacier. A glacier is maintained by
accumulation of snow at high altitudes, balanced by melting at low
altitudes or discharge into the sea.
Global surface temperature
The global surface temperature is the
area-weighted global average of (i) the sea surface temperature
over the oceans (i.e., the sub-surface bulk temperature in the
first few meters of the ocean), and (ii) the surface air
temperature over land at 1.5 m above the ground.
Global Warming Potential
An index, describing the radiative
characteristics of well-mixed greenhouse gases, that represents the
combined effect of the differing times these gases remain in the
atmosphere and their relative effectiveness in absorbing outgoing
infrared radiation. This index approximates the time-integrated
warming effect of a unit mass of a given greenhouse gas in today's
atmosphere, relative to that of carbon dioxide.
Greenhouse gases effectively absorb infrared
radiation, emitted by the Earth's surface, by the atmosphere itself
due to the same gases, and by clouds. Atmospheric radiation is
emitted to all sides, including downward to the Earth's surface.
Thus greenhouse gases trap heat within the surface-troposphere
system. This is called the "natural greenhouse effect." Atmospheric
radiation is strongly coupled to the temperature of the level at
which it is emitted. In the troposphere, the temperature generally
decreases with height. Effectively, infrared radiation emitted to
space originates from an altitude with a temperature of, on
average, -19°C, in balance with the net incoming solar radiation,
whereas the Earth's surface is kept at a much higher temperature
of, on average, +14°C. An increase in the concentration of
greenhouse gases leads to an increased infrared opacity of the
atmosphere, and therefore to an effective radiation into space from
a higher altitude at a lower temperature. This causes a radiative
forcing, an imbalance that can only be compensated for by an
increase of the temperature of the surface-troposphere system. This
is the "enhanced greenhouse effect."
Greenhouse gases are those gaseous constituents
of the atmosphere, both natural and anthropogenic, that absorb and
emit radiation at specific wavelengths within the spectrum of
infrared radiation emitted by the Earth's surface, the atmosphere,
and clouds. This property causes the greenhouse effect. Water vapor
(H2O), carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4),
and ozone (O3) are the primary greenhouse gases in the Earth's
atmosphere. Moreover there are a number of entirely human-made
greenhouse gases in the atmosphere, such as the halocarbons and
other chlorine- and bromine-containing substances, dealt with under
the Montreal Protocol. Besides CO2, N2O, and CH4, the Kyoto
Protocol deals with the greenhouse gases sulfur hexafluoride (SF6),
hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs).
The process by which external water is added to
the zone of saturation of an aquifer, either directly into a
formation or indirectly by way of another formation.
The particular environment or place where an
organism or species tend to live; a more locally circumscribed
portion of the total environment.
An area within an urban area characterized by
ambient temperatures higher than those of the surrounding area
because of the absorption of solar energy by materials like
The conversion of organic matter to CO2 by
organisms other than plants.
Among the six greenhouse gases to be curbed under
the Kyoto Protocol. They are produced commercially as a substitute
for chlorofluorocarbons. HFCs largely are used in refrigeration and
semiconductor manufacturing. Their Global Warming Potentials range
from 1,300 to 11,700.
The component of the climate system composed of
liquid surface and subterranean water, such as oceans, seas,
rivers, freshwater lakes, underground water, etc.
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A dome shaped ice mass covering a highland area
that is considerably smaller in extent than an ice sheet.
A mass of land ice that is sufficiently deep to
cover most of the underlying bedrock topography, so that its shape
is mainly determined by its internal dynamics (the flow of the ice
as it deforms internally and slides at its base). An ice sheet
flows outward from a high central plateau with a small average
surface slope. The margins slope steeply, and the ice is discharged
through fast-flowing ice streams or outlet glaciers, in some cases
into the sea or into ice shelves floating on the sea. There are
only two large ice sheets in the modern world, on Greenland and
Antarctica, the Antarctic ice sheet being divided into East and
West by the Transantarctic Mountains; during glacial periods there
A floating ice sheet of considerable thickness
attached to a coast (usually of great horizontal extent with a
level or gently undulating surface); often a seaward extension of
(Climate) Impact assessment
The practice of identifying and evaluating the
detrimental and beneficial consequences of climate change on
natural and human systems.
Consequences of climate change on natural and
human systems. Depending on the consideration of adaptation, one
can distinguish between potential impacts and residual impacts.
Potential impacts: All impacts that may occur given a projected
change in climate, without considering adaptation. Residual
impacts: The impacts of climate change that would occur after
adaptation. See also aggregate impacts, market impacts, and
Implementation refers to the actions (legislation
or regulations, judicial decrees, or other actions) that
governments take to translate international accords into domestic
law and policy. It includes those events and activities that occur
after the issuing of authoritative public policy directives, which
include the effort to administer and the substantive impacts on
people and events. It is important to distinguish between the legal
implementation of international commitments (in national law) and
the effective implementation (measures that induce changes in the
behavior of target groups).
Compliance is a matter of whether and to what
extent countries do adhere to the provisions of the accord.
Compliance focuses on not only whether implementing measures are in
effect, but also on whether there is compliance with the
implementing actions. Compliance measures the degree to which the
actors whose behavior is targeted by the agreement, whether they
are local government units, corporations, organizations, or
individuals, conform to the implementing measures and
A species occurring in an area outside its
historically known natural range as a result of accidental
dispersal by humans (also referred to as "exotic species" or "alien
An introduced species that invades natural
Isostatic land movements
Isostasy refers to the way in which the
lithosphere and mantle respond to changes in surface loads. When
the loading of the lithosphere is changed by alterations in land
ice mass, ocean mass, sedimentation, erosion, or mountain building,
vertical isostatic adjustment results, in order to balance the new
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See El Niño Southern Oscillation.
The total of arrangements, activities, and inputs
undertaken in a certain land cover type (a set of human actions).
The social and economic purposes for which land is managed (e.g.,
grazing, timber extraction, and conservation).
A change in the use or management of land by
humans, which may lead to a change in land cover. Land cover and
land-use change may have an impact on the albedo,
evapotranspiration, sources, and sinks of greenhouse gases, or
other properties of the climate system, and may thus have an impact
on climate, locally or globally.
A mass of material that has slipped downhill by
gravity, often assisted by water when the material is saturated;
rapid movement of a mass of soil, rock, or debris down a slope.
Leapfrogging (or technological leapfrogging)
refers to the opportunities in developing countries to bypass
several stages of technology development, historically observed in
industrialized countries, and apply the most advanced presently
available technologies in the energy and other economic sectors,
through investments in technological development and capacity
The upper layer of the solid Earth, both
continental and oceanic, which is composed of all crustal rocks and
the cold, mainly elastic, part of the uppermost mantle. Volcanic
activity, although part of the lithosphere, is not considered as
part of the climate system, but acts as an external forcing
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Mean Sea Level (MSL)
Mean Sea Level is normally defined as the average
relative sea level over a period, such as a month or a year, long
enough to average out transients such as waves. See also sea-level
A hydrocarbon that is a greenhouse gas produced
through anaerobic (without oxygen) decomposition of waste in
landfills, animal digestion, decomposition of animal wastes,
production and distribution of natural gas and oil, coal
production, and incomplete fossil-fuel combustion. Methane is one
of the six greenhouse gases to be mitigated under the Kyoto
Method by which methane emissions (e.g., from
coal mines or waste sites) are captured and then reused either as a
fuel or for some other economic purpose (e.g., reinjection in oil
or gas reserves).
An anthropogenic intervention to reduce the
sources or enhance the sinks of greenhouse gases.
The social, political, and economic structures
and conditions that are required for effective mitigation.
The upper region of the ocean well-mixed by
interaction with the overlying atmosphere.
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Net carbon dioxide emissions
Difference between sources and sinks of carbon
dioxide in a given period and specific area or region.
Enhancement of plant growth through the addition
of nitrogen compounds.
Nitrogen oxides (NOx)
Any of several oxides of nitrogen.
Nitrous oxide (N2O)
A powerful greenhouse gas emitted through soil
cultivation practices, especially the use of commercial and organic
fertilizers, fossil-fuel combustion, nitric acid production, and
biomass burning. One of the six greenhouse gases to be curbed under
the Kyoto Protocol.
Pollution from sources that cannot be defined as
discrete points, such as areas of crop production, timber, surface
mining, disposal of refuse, and construction. See also pointsource
North Atlantic Oscillation
The North Atlantic Oscillation consists of
opposing variations of barometric pressure near Iceland and near
the Azores. On average, a westerly current, between the Icelandic
low pressure area and the Azores high pressure area, carries
cyclones with their associated frontal systems towards Europe.
However, the pressure difference between Iceland and the Azores
fluctuates on time scales of days to decades, and can be reversed
at times. It is the dominant mode of winter climate variability in
the North Atlantic region, ranging from central North America to
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Ocean conveyor belt
The theoretical route by which water circulates
around the entire global ocean, driven by wind and the thermohaline
Aerosol particles consisting predominantly of
organic compounds, mainly C, H, and O, and lesser amounts of other
Ozone, the triatomic form of oxygen (O3), is a
gaseous atmospheric constituent. In the troposphere it is created
both naturally and by photochemical reactions involving gases
resulting from human activities (photochemical "smog"). In high
concentrations, tropospheric ozone can be harmful to a wide-range
of living organisms. Tropospheric ozone acts as a greenhouse gas.
In the stratosphere, ozone is created by the interaction between
solar ultraviolet radiation and molecular oxygen (O2).
Stratospheric ozone plays a decisive role in the stratospheric
radiative balance. Its concentration is highest in the ozone layer.
Depletion of stratospheric ozone, due to chemical reactions that
may be enhanced by climate change, results in an increased
ground-level flux of ultraviolet-B radiation. See also Montreal
Protocol and ozone layer.
The stratosphere contains a layer in which the
concentration of ozone is greatest, the so-called ozone layer. The
layer extends from about 12 to 40 km. The ozone concentration
reaches a maximum between about 20 and 25 km. This layer is being
depleted by human emissions of chlorine and bromine compounds.
Every year, during the Southern Hemisphere spring, a very strong
depletion of the ozone layer takes place over the Antarctic region,
also caused by human-made chlorine and bromine compounds in
combination with the specific meteorological conditions of that
region. This phenomenon is called the ozone hole.
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Perennially frozen ground that occurs wherever
the temperature remains below 0°C for several years.
The process by which plants take carbon dioxide
(CO2) from the air (or bicarbonate in water) to build
carbohydrates, releasing oxygen (O2) in the process. There are
several pathways of photosynthesis with different responses to
atmospheric CO2 concentrations. See also carbon dioxide
The plant forms of plankton (e.g., diatoms).
Phytoplankton are the dominant plants in the sea, and are the bast
of the entire marine food web. These single-celled organisms are
the principal agents for photosynthetic carbon fixation in the
ocean. See also zooplankton.
Aquatic organisms that drift or swim weakly. See
also phytoplankton and zooplankton.
Pollution resulting from any confined, discrete
source, such as a pipe, ditch, tunnel, well, container,
concentrated animalfeeding operation, or floating craft. See also
A process that results in an amplification of the
response of a system to an external influence. For example,
increased atmospheric water vapor in response to global warming
would be a positive feedback on warming, because water vapor is a
The vertical movement of the continents and sea
floor following the disappearance and shrinking of ice sheets-for
example, since the Last Glacial Maximum (21 thousand years before
the present). The rebound is an isostatic land movement.
Energy embodied in natural resources (e.g., coal,
crude oil, sunlight, uranium) that has not undergone any
anthropogenic conversion or transformation.
Categories of costs influencing an individual's
decision making are referred to as private costs. See also social
cost and total cost.
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The term radiative forcing refers to changes in
the energy balance of the earth-atmosphere system in response to a
change in factors such as greenhouse gases, land-use change, or
solar radiation. The climate system inherently attempts to balance
incoming (e.g., light) and outgoing (e.g. heat) radiation. Positive
radiative forcings increase the temperature of the lower
atmosphere, which in turn increases temperatures at the Earth's
surface. Negative radiative forcings cool the lower atmosphere.
Radiative forcing is most commonly measured in units of watts per
square meter (W/m2).
Unimproved grasslands, shrublands, savannahs, and
The renewal of a stand of trees through either
natural means (seeded onsite or adjacent stands or deposited by
wind, birds, or animals) or artificial means (by planting seedlings
or direct seeding).
Rapid climate change
The non-linearity of the climate system may lead
to rapid climate change, sometimes called abrupt events or even
surprises. Some such abrupt events may be imaginable, such as a
dramatic reorganization of the thermohaline circulation, rapid
deglaciation, or massive melting of permafrost leading to fast
changes in the carbon cycle. Others may be truly unexpected, as a
consequence of a strong, rapidly changing, forcing of a non-linear
Occurs because, for example, an improvement in
motor efficiency lowers the cost per kilometer driven; it has the
perverse effect of encouraging more trips.
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.
Relative sea level
Sea level measured by a tide gauge with respect
to the land upon which it is situated. See also Mean Sea Level.
(Relative) Sea level secular
Long-term changes in relative sea level caused by
either eustatic changes (e.g., brought about by thermal expansion)
or changes in vertical land movements.
Energy sources that are, within a short time
frame relative to the Earth's natural cycles, sustainable, and
include non-carbon technologies such as solar energy, hydropower,
and wind, as well as carbon-neutral technologies such as
Energy obtained from sources such as geothermal,
wind, photovoltaic, solar, and biomass.
If permits are auctioned, this gives considerable
sums of money to be recycled back into the economy, either through
a lump sum payment of offsetting other taxes. If the existing taxes
that are correspondingly reduced were very inefficient, this allows
this allows the possibility of both environmental and economic
benefits from the trading system, commonly called the 'double
Research, development, and
Scientific and/or technical research and
development of new production processes or products, coupled with
analysis and measures that provide information to potential users
regarding the application of the new product or process;
demonstration tests; and feasibility of applying these products
processes via pilot plants and other pre-commercial
Refer to those occurrences that are identified
and measured as economically and technically recoverable with
current technologies and prices. See also resources.
A component of the climate system, other than the
atmosphere, which has the capacity to store, accumulate, or release
a substance of concern (e.g., carbon, a greenhouse gas, or a
precursor). Oceans, soils, and forests are examples of reservoirs
of carbon. Pool is an equivalent term (note that the definition of
pool often includes the atmosphere). The absolute quantity of
substance of concerns, held within a reservoir at a specified time,
is called the stock. The term also means an artificial or natural
storage place for water, such as a lake, pond, or aquifer, from
which the water may be withdrawn for such purposes as irrigation,
water supply, or irrigation.
Amount of change a system can undergo without
Resource base includes both reserves and
Resources are those occurrences with less certain
geological and/or economic characteristics, but which are
considered potentially recoverable with foreseeable technological
and economic developments.
The process whereby living organisms converts
organic matter to carbon dioxide, releasing energy and consuming
The response time or adjustment time is the time
needed for the climate system or its components to re-equilibrate
to a new state, following a forcing resulting from external and
internal processes or feedbacks. It is very different for various
components of the climate system. The response time of the
troposphere is relatively short, from days to weeks, whereas the
stratosphere comes into equilibrium on a time scale of typically a
few months. Due to their large heat capacity, the oceans have a
much longer response time, typically decades, but up to centuries
or millennia. The response time of the strongly coupled
surface-troposphere system is, therefore, slow compared to that of
the stratosphere, and mainly determined by the oceans. The
biosphere may respond fast (e.g., to droughts), but also very
slowly to imposed changes. See lifetime for a different definition
of response time pertinent to the rate of processes affecting the
concentration of trace gases.
That part of precipitation that does not
evaporate. In some countries, runoff implies surface runoff
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The accumulation of salts in soils.
Displacement of fresh surfacewater or groundwater
by the advance of saltwater due to its greater density, usually in
coastal and estuarine areas.
An increase in the mean level of the ocean.
Eustatic sea-level rise is a change in global average sea level
brought about by an alteration to the volume of the world ocean.
Relative sea level rise occurs where there is a net increase in the
level of the ocean relative to local land movements. Climate
modelers largely concentrate on estimating eustatic sea-level
change. Impact researchers focus on relative sea-level change.
A human-made wall or embankment along a shore to
prevent wave erosion.
Ecosystems that have more than 250 mm
precipitation per year but are not highly productive; usually
classified as rangelands.
The process of increasing the carbon content of a
carbon reservoir other than the atmosphere. Biological approaches
to sequestration include direct removal of carbon dioxide from the
atmosphere through land-use change, afforestation, reforestation,
and practices that enhance soil carbon in agriculture. Physical
approaches include separation and disposal of carbon dioxide from
flue gases or from processing fossil fuels to produce hydrogen- and
carbon dioxide-rich fractions and long term storage in underground
in depleted oil and gas reservoirs, coal seams, and saline
aquifers. See also uptake.
Unconsolidated or loose sedimentary material
whose constituent rock particles are finer than grains of sand and
larger than clay particles.
Development and care of forests.
Any process, activity or mechanism that removes a
greenhouse gas, an aerosol, or a precursor of a greenhouse gas or
aerosol from the atmosphere.
A seasonal accumulation of slow-melting snow.
The social cost of an activity includes the value
of all the resources used in its provision. Some of these are
priced and others are not. Non-priced resources are referred to as
externalities. It is the sum of the costs of these externalities
and the priced resources that makes up the social cost. See also
private cost and total cost.
Water stored in or at the land surface and
available for evaporation.
The Sun exhibits periods of high activity
observed in numbers of sunspots, as well as radiative output,
magnetic activity, and emission of high energy particles. These
variations take place on a range of time scales from millions of
years to minutes. See also solar cycle.
Solar ("11 year") cycle
A quasi-regular modulation of solar activity with
varying amplitude and a period of between 9 and 13 years.
Radiation emitted by the Sun. It is also referred
to as shortwave radiation. Solar radiation has a distinctive range
of wavelengths (spectrum) determined by the temperature of the
Particles formed during the quenching of gases at
the outer edge of flames of organic vapors, consisting
predominantly of carbon, with lesser amounts of oxygen and hydrogen
present as carboxyl and phenolic groups and exhibiting an imperfect
graphitic structure (Charlson and Heintzenberg, 1995). See also
Any process, activity, or mechanism that releases
a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or
aerosol into the atmosphere.
See El Niño Southern Oscillation.
The economic effects of domestic or sectoral
mitigation measures on other countries or sectors. In this report,
no assessment is made on environmental spillover effects. Spillover
effects can be positive or negative and include effects on trade,
carbon leakage, transfer, and diffusion of environmentally sound
technology and other issues.
The achievement of stabilization of atmospheric
concentrations of one or more greenhouse gases (e.g., carbon
dioxide or a CO2-equivalent basket of greenhouse gases).
In this report, this refers to analyses or
scenarios that address the stabilization of the concentration of
Person or entity holding grants, concessions, or
any other type of value that would be affected by a particular
action or policy.
Set of rules or codes mandating or defining
product performance (e.g., grades, dimensions, characteristics,
test methods, and rules for use). International product and/or
technology or performance standards establish minimum requirements
for affected products and/or technologies in countries where they
are adopted. The standards reduce greenhouse gas emissions
associated with the manufacture or use of the products and/or
application of the technology. See also regulatory measures.
All the elements of climate change, including
mean climate characteristics, climate variability, and the
frequency and magnitude of extremes.
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.
Water within a river channel, usually expressed
in m3 sec-1.
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
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.
A rise in the water level in relation to the
land, so that areas of formerly dry land become inundated; it
results either from a sinking of the land or from a rise of the
The sudden sinking or gradual downward settling
of the Earth's surface with little or no horizontal motion.
Direct payment from the government to an entity,
or a tax reduction to that entity, for implementing a practice the
government wishes to encourage. Greenhouse gas emissions can be
reduced by lowering existing subsidies that have the effect of
raising emissions, such as subsidies to fossil-fuel use, or by
providing subsidies for practices that reduce emissions or enhance
sinks (e.g., for insulation of buildings or planting trees).
Small dark areas on the Sun. The number of
sunspots is higher during periods of high solar activity, and
varies in particular with the solar cycle.
The water that travels over the soil surface to
the nearest surface stream; runoff of a drainage basin that has not
passed beneath the surface since precipitation.
Development that meets the needs of the present
without compromising the ability of future generations to meet
their own needs.
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The broad set of processes that cover the
exchange of knowledge, money, and goods among different
stakeholders that lead to the spreading of technology for adapting
to or mitigating climate change. As a generic concept, the term is
used to encompass both diffusion of technologies and technological
cooperation across and within countries.
The erosion of ice-rich permafrost by the
combined thermal and mechanical action of moving water.
In connection with sea level, this refers to the
increase in volume (and decrease in density) that results from
warming water. A warming of the ocean leads to an expansion of the
ocean volume and hence an increase in sea level.
Large-scale density-driven circulation in the
ocean, caused by differences in temperature and salinity. In the
North Atlantic, the thermohaline circulation consists of warm
surface water flowing northward and cold deepwater flowing
southward, resulting in a net poleward transport of heat. The
surface water sinks in highly restricted sinking regions located in
Characteristic time for a process to be
The terms "top" and "bottom" are shorthand for
aggregate and disaggregated models. The top-down label derives from
how modelers applied macro-economic theory and econometric
techniques to historical data on consumption, prices, incomes, and
factor costs to model final demand for goods and services, and
supply from main sectors, like the energy sector, transportation,
agriculture, and industry. Therefore, top-down models evaluate the
system from aggregate economic variables, as compared to bottom-up
models that consider technological options or project specific
climate change mitigation policies. Some technology data were,
however, integrated into top-down analysis and so the distinction
is not that clear-cut.
The boundary between the troposphere and the
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.
A treeless, level, or gently undulating plain
characteristic of arctic and subarctic regions.
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Ultraviolet (UV)-B radiation
Solar radiation within a wavelength range of
280-320 nm, the greater part of which is absorbed by stratospheric
ozone. Enhanced UV-B radiation suppresses the immune system and can
have other adverse effects on living organisms.
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.
The addition of a substance of concern to a
reservoir. The uptake of carbon-containing substances, in
particular carbon dioxide, is often called (carbon) sequestration.
See also sequestration.
Transport of deeper water to the surface, usually
caused by horizontal movements of surface water.
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."
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The net output of a sector after adding up all
outputs and subtracting intermediate inputs.
Worth, desirability, or utility based on
individual preferences. The total value of any resource is the sum
of the values of the different individuals involved in the use of
the resource. The values, which are the foundation of the
estimation of costs, are measured in terms of the willingness to
pay (WTP) by individuals to receive the resource or by the
willingness of individuals to accept payment (WTA) to part with the
An organism, such as an insect, that transmits a
pathogen from one host to another.
The degree to which a system is susceptible to,
or unable to cope with, adverse effects of climate change,
including climate variability and extremes. Vulnerability is a
function of the character, magnitude, and rate of climate variation
to which a system is exposed, its sensitivity, and its adaptive
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A country is water-stressed if the available
freshwater supply relative to water withdrawals acts as an
important constraint on development. Withdrawals exceeding 20% of
renewable water supply has been used as an indicator of water
Carbon gain in photosynthesis per unit water lost
in evapotranspiration. It can be expressed on a short-term basis as
the ratio of photosynthetic carbon gain per unit transpirational
water loss, or on a seasonal basis as the ratio of net primary
production or agricultural yield to the amount of available
Amount of water extracted from water bodies.
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The animal forms of plankton. They consume
phytoplankton or other zooplankton. See also phytoplankton.
Credit: (2010) Climate Change
Glossary. Retrieved February 2, 2010, from