The climate change glossary

By S.M. Enzler MSc

Note: this website also contains a water glossary!



Adaptive capacity

The ability of a system (e.g. ecosystem) to adapt to climate change or other environmental disturbances. This may mean moderating potential damages, taking advantage of opportunities or coping with the consequences. In discussions on global warming adaptive capacity often refers to a country. In this case it is currently much lower in developing countries, consequential to poverty.


Collection of airborne solid or liquid particles that reside in the air for at least several hours. Aerosols have a typical size between 0,01 and 10 nm. Aerosols may influence climate in two ways: directly through scattering and absorbing radiation, and indirectly through acting as condensation nuclei for cloud formation or modifying the optical properties and lifetime of clouds.


The ratio of reflected to incident light; albedo can be expressed as either a percentage or as a fraction of 1. Snow covered areas have a high albedo (up to about 0,9 or 90%) because of their white color, while vegetation has a low albedo (generally about 0,1 or 10%) because of its dark colors and because of the light that is absorbed for photosynthesis. Clouds have an intermediate albedo and are the most important contributor to the earth's albedo. The Earth's aggregate albedo is approximately 0,3.


A state-of-the-art radar technique that measures global elevation of sea, land or ice surfaces compared to the centre of the earth.

Annex 1 Parties

Countries that have agreed under the UNFCCC to reduce their greenhouse gas emissions. These are both OECD countries and economies in transition.

Anthropogenic emissions

Emissions of particles or substances resulting from human activities, such as industry and agriculture.

Arrhenius, Svante

Swedish scientist that was the first to claim in 1896 that fossil fuel combustion may eventually result in enhanced global warming. He proposed a relation between atmospheric carbon dioxide concentrations and temperature. He found that the average surface temperature of the earth is about 15oC because of the infrared absorption capacity of water vapor and carbon dioxide. This is called the natural greenhouse effect. Arrhenius suggested a doubling of the CO2 concentration would lead to a 5oC temperature rise.


A blanket of 560 m of air surrounding the earth that supports life. The atmosphere absorbs energy from the sun, recycles water and other chemicals and works with electrical and magnetic forces to provide a moderate climate. It also protects us from high-energy radiation and the frigid vacuum of space.

The atmosphere is primarily composed of nitrogen (78%), oxygen (21%), and argon (1%). Other components include water (0-7%), ozone (0-0,01%) and carbon dioxide (0,01-0,1%).

The atmosphere changes from the ground up and consists of four distinct layers: troposphere (8-14,5 km), stratosphere (14,5-50 km), mesosphere (50-85 km) and thermosphere (85-600 km). Temperatures are different for each layer. In the troposphere temperatures drop from about 17 to -52 degrees Celcius, in the stratosphere temperatures increase gradually to -3 degrees Celcius, in the mesosphere temperatures fall to -93 degrees Celcius as altitude increases, and in the thermosphere temperatures can be as high as 1727 degrees Celsius (figure 1).

Above the thermosphere, the exosphere starts and continues until it mixes with interplanetary gases or space. This layer primarily consists of low-density particles such as hydrogen and helium.

Source: Exploration 1995

Attribution of climate change

The process of establishing the most likely causes for the detected climate change with some defined level of confidence.


Baseline emissions

The emissions that would occur without policy intervention. Baseline estimates are needed to determine the effectiveness of emissions mitigation strategies.


Total mass of living matter within a given unit of environmental area. Also: plant material, vegetation, or agricultural waste used as a fuel or energy source.


The part of the earth and its atmosphere in which ecosystems and living organisms exist or that is capable of supporting life. The biosphere includes the atmosphere, land (terrestrial biosphere) and water (marine biosphere).


The total mass of a certain gaseous substance in the atmosphere.


Carbon cycle

The flow of carbon through the atmosphere, lithosphere, biosphere and hydrosphere. See the carbon cycle page for more information.

Carbon dioxide

A colorless, odorless, incombustible gas (CO2), formed during respiration, combustion, and organic decomposition and used in food refrigeration, carbonated beverages, inert atmospheres, fire extinguishers, and aerosols. It is the principal anthropogenic greenhouse gas that affects the earth's radiative balance. It has a Global Warming Potential (GWP) of 1 and is used as the reference gas for GWPs of other greenhouse gases.

Carbon flux

Shifts or flows of carbon over time from one pool to another.

Carbon sequestration

The uptake and storage of carbon, for example by fossil fuels.


Community Climate System Model version 3. The world's most advanced climate model used extensively by organizations to predict the consequences of climate change.


Chlorofluorocarbons, compounds containing chlorine and fluorine bonds that have been used as refrigerants before the Montreal Protocol. These compounds have been shown to deplete stratospheric ozone. These compounds can also act as greenhouse gases.

Clean Development Mechanisms

Investments of developed countries in emissions reducing projects in developing countries to obtain credit to assist in meeting their assigned amounts. The details of the CDM have yet to be negotiated at the international level.


The meteorological conditions, including temperature, precipitation, and wind, that characteristically prevail in a particular region. Climate in a wider sense is the state, including a statistical description, of the climate system.

Climate change

A change in the world's climate, persisting for an extended period of time (typically decades or longer). Climate change occurs as a result of natural conditions or anthropogenic sources changing the composition of the atmosphere or the land use type.

Climate change commitment

Term introduced by researchers of the National Centre of Atmospheric Research (NCAR) in Boulder, Colorado to clarify the seriousness of climate change to non-climatologists. It means the amount of climate change that will inevitably occur in the coming century as a result of human behavior in the 20th century.

Climate feedback

An interaction mechanism between processes in the climate system. A primary process causes changes in a second process which in turn influences the primary process. A positive feedback intensifies the original process, and a negative feedback reduces it.

Climate forecast

The result of an attempt to produce a most likely description or estimate of the actual evolution of the climate in the long term.

Climate model

A numerical representation of the climate system that is based on the physical, chemical and biological properties of its components, their interactions and feedback processes and accounts for its known or inferred properties. A climate model is used to study climate characteristics. Climate models used to be fairly simple, but now there is an evolution towards more complex models with active chemistry and biology.

Climate modeling

The simulation of climate using computer-based models.

Climate projection

A description 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 subject to uncertainty, because they are typically based on assumptions concerning future socio-economic and technological developments that may or may not be realized.

Climate sensitivity

Equilibrium change in surface air temperature following a unit change in radiative forcing (°C/Wm-2). According to the IPCC climate sensitivity refers to the equilibrium change in global mean surface temperature following a doubling of the atmospheric CO2 concentration.

Climate (change) scenario

A climate scenario consists of projections of possible climate futures, containing developments of driving forces, greenhouse gas emissions, temperature change and sea level rise and their key relationships. A climate change scenario is the difference between a climate scenario and the current climate.

Climate system

The highly complex system consisting of the atmosphere, the hydrosphere, the lithosphere and the biosphere and the interactions between them. The evolution of the climate system is a consequence of volcanic eruptions, solar variations and anthropogenic alterations, such as land use change.

Climate variability

Mean state and other statistical variations in climate on all temporal scales and spatial scales beyond that of individual weather events. Variations may be caused by natural internal processes within the climate system or by variations in natural or anthropogenic forcing.


A metric measure used to compare the emissions of various greenhouse gases based upon their Global Warming Potential (GWP). The concentration of CO2 that would give the same amount of radiative forcing as the given mixture of CO2 and other greenhouse gases. Essentially, they sum the radiative forcing of all trace gases and treat the total forcing as if it comes from an equivalent CO2 concentration.

CO2 fertilization

Te enhancement of plant growth as a result of elevated atmospheric CO2 concentrations.

Concentration scenarios

Projections of greenhouse gas concentrations derived from emission scenarios and used as input into a climate model to compute climate projections.


Trails of dangerous chemicals left behind in air by aviation. These were shown in 2003 to contribute to the greenhouse effect and global warming.



A land use change induced by removal of forest by humans for various purposes.


Land degradation into dry areas caused by climatic variations and human activities. This often causes a loss of biological and economic productivity of the land. Processes that enhance desertification are for example soil erosion, deterioration of soil properties and long-term loss of natural vegetation.

Detection of climate change

The process of demonstrating that climate has changed in some defined statistical sense, without providing a reason for that change.

Driving forces

Climate scenarios contain various driving forces of climate change, including population growth and socio-economic and technological development. These drivers encompass various future scenarios that might influence greenhouse gas sources and sinks, such as the energy system and land use change.

Diurnal temperature range

The difference between the maximum and minimum temperature during a day.

Dobson Unit (DU)

This unit measures the total amount of ozone in a vertical column above the earth. One DU corresponds to a column of ozone containing 2,69 x 1020 molecules per square meter. The number of Dobson Units is the thickness in units of 10-5 m, that the ozone column would occupy if compressed into a layer of uniform density at a pressure of 1013 hPa, and a temperature of 0°C.



An ecological community together with its environment, functioning as a unit. The scale of an ecosystem largely depends on the type of study that is conducted and may range from a small number of populations and their environment to the entire earth.

Emission permit

Tradable allocation of entitlements by a government to an individual firm to emit a specific amount of a substance.

Emission standard

An amount of emission that may not be exceeded legally.


The release of gaseous substances, such as greenhouse gases, into the atmosphere.

Emissions scenario

Representation of the future development of emissions of greenhouse gases based on a set of assumptions about driving forces and their key relationships.


The combined process of evaporation from the earth's surface and transpiration from vegetation.


By-products of activities that affect the well-being of people or damage the environment, where those impacts are not reflected in market prices.

Extreme weather event

A manifestation of weather which is rare within its statistical distribution on a particular location. By rare one usually means rarer than the 90th percentile. The characteristics of extreme weather vary according to the location.


Forestry/ forestation

The science and art of cultivating, maintaining, and developing forests.

Fossil fuels

Fuels from fossil carbon deposits such as oil, natural gas and coal. These are burned in order to gain energy. During these combustion processes greenhouse gases are released.



A huge mass of ice slowly flowing over a land mass, formed from compacted snow in an area where snow accumulation exceeds melting and sublimation.

Global radiation Balance

A balance, which implies that globally the amount of incoming solar radiation must on average be equal to the sum of outgoing reflected solar radiation and outgoing infrared radiation emitted by the climate system.

Global surface temperature

The average of the sea temperature in the first few meters of the oceans and the temperature 1,5 m above ground on land surfaces.

Global warming

The warming of the earth's surface, driven by either natural or anthropogenic forces.

Global Warming Potential

GWP, an index describing radiative characteristics of greenhouse gases relative to that of carbon dioxide (GWP of 1). It represents the time greenhouse gases remain in the atmosphere and their potential to absorb infrared radiation.

Greenhouse effect

The sun radiates solar energy on earth. The larger part of this energy (45%) is radiated back into space. Greenhouse gases in the atmosphere contribute to global warming by adsorption and reflection of atmospheric and solar energy. This natural phenomenon is what we call the greenhouse effect. It is agreed that the greenhouse effect is correlated with global temperature change. If greenhouse gases would not exist earthly temperatures would be below –18 oC.
After the industrial revolution of the 1700’s the greenhouse effect was enhanced by greenhouse gas emissions of anthropogenic nature. The main source of anthropogenic greenhouse gas emissions is fossil fuel combustion. The contribution of greenhouse gases to the greenhouse effect varies. The enhanced greenhouse effect is said to cause a cascade of impacts on both environment and society. How and when these effects will take place is still under discussion.

Greenhouse gases

Also referred to as GHG. Gases that absorb atmospheric and solar infrared radiation and reflect it back to earth to increase global warming, causing climate change. Natural greenhouse gases include water vapor, carbon dioxide, methane, ozone and nitrous oxide. Past and future anthropogenic emissions of the greenhouse gases carbon dioxide, methane and nitrous oxide enhance global warming.

Gross Domestic Product (GDP)

The value of all goods and services produced or consumed within a nation’s borders.

Gross Primary Production (GPP)

The amount of carbon fixed from the atmosphere through photosynthesis.



Also referred to as decay constant. The term is used to quantify a first-order exponential decay process.


Greenhouse gases containing either chlorine, bromine or fluorine and carbon. The chlorine and bromine containing halocarbons are also involved in the depletion of the ozone layer.


The waters of the earth's surface as distinguished from those of the lithosphere and the atmosphere and the water vapor in the atmosphere.


IMAGE model

The Integrated Model for Assessment of the Greenhouse Effect. This is one of the climate models applied for the construction of the IPCC SRES scenarios.

Indirect aerosol effect

Aerosols may lead to an indirect radiative forcing of the climate system through acting as condensation nuclei or modifying the optical properties and lifetime of clouds.

Industrial revolution

The complex of radical socioeconomic changes starting in the early 18th century. Extensive mechanization of production systems resulted in a shift from home-based hand manufacturing to large-scale factory production. The industrial revolution marks the beginning of a strong increase in the use of fossil fuels resulting in an increase in greenhouse gases in the atmosphere and therefore contributed to the enhanced greenhouse effect.

Infrared radiation

Radiation emitted by the earth's surface, atmosphere and clouds. Infrared radiation has a distinctive range of wavelengths called a spectrum. Greenhouse gases strongly absorb this radiation in the atmosphere, and reradiate some back towards the surface, creating the greenhouse effect.

Instrumental period

Period after 1855 that allowed us to reconstruct temperatures because thermometers were producing reconstructable data. Before 1855 proxy indicators were used to determine temperatures.

Integrated Environmental Assessment

The work field that researches causes and impacts of environmental issues and policy measures (solutions) by combining economic, environmental and social sciences. It is a subdivision of the work field of Environmental Systems Analysis. This is a type of Environmental Science that applies many different tools, including environmental models, environmental impact assessment and environmental indicators, to describe and find solutions for environmental problems.

Inverse modeling

Modeling technique by which modeling input is estimated from modeling output, rather than vice versa. This is for example used to determine the causes of enhanced greenhouse gas concentrations in the atmosphere and for computing atmospheric transport.


Intergovernmental Panel on Climate Change, the international organization founded by the United Nations that tries to predict the impact of the greenhouse effect according to existing climate models and literature information. The Panel consists of more than 2500 scientific and technical experts from more than 60 countries all over the world. It is therefore referred to as the largest peer-reviewed scientific cooperation project in history.

IPCC SRES scenarios

Special Reports on Emission scenarios by the IPCC, containing information on possible future climate developments and consequences for society and the environment. Emissions scenarios are a central component of any assessment of climate change. See for more information the IPCC SRES scenarios page.


Joint Implementation

Richer countries have the opportunity to achieve their emission reduction goals, formulated in the Kyoto Protocol, by financing energy saving projects for poorer countries that have also signed the treaty.


Kyoto Protocol

Protocol adopted in 1998 in Kyoto, Japan. It requires participating countries to reduce their anthropogenic greenhouse gas emissions (CO2, CH4, N2O, HFCs, PFCs, and SF6) by at least 5% below 1990 levels in the commitment period 2008 to 2012. The Kyoto Protocol was eventually signed in Bonn in 2001 by 186 countries. Several countries such as the United States and Australia have retreated. More information can be found on the Kyoto Protocol emission reductions page.


Land use

The management practice of a certain land cover type (a set of human actions). Land use may be forest, arable land, grassland, urban area or other.

Land use change

Alteration of the management practice on a certain land cover type. Land use changes may influence the climate system because they impact evapotranspiration and sources and sinks of greenhouse gases.


The outer part of the earth, consisting of the crust and upper mantle, approximately 100 km thick.



Climate model that calculates average atmospheric temperatures and sea levels. It is used by IPCC for the construction of the SRES scenarios.

Mean Sea Level (MSL)

The average Relative Sea Level over a period, such as a month or a year, long enough to average out transients such as waves.

Medieval Warm Period

Term introduced by the British meteorologist Hubert Lamb in 1965, for a period between the 9th and 13th century during which it was extremely warm on many locations in and around Europe. Wine was grown in Scandinavia and agriculture was possible on Greenland. This was determined by studying snow lines in the mountains and temperatures in deep boreholes and has given us the impression that temperature changes may have occurred before. Geochemist Wallace Broecker thinks that cyclic processes in the oceans cause a warmer period once in every 1500 years.


A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 24,5. Methane (CH4) is 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.


A human intervention to reduce the sources or enhance the sinks of substances that pollute the environment, for example greenhouse gases.

Mole fraction

The ratio of the moles of one component of a system to the total moles of all components present. Typical values for long-lived greenhouse gases are in the order of mmol/mol (parts per million: ppm) or nmol/mol (parts per billion: ppb). Mole fraction differs from volume mixing ratio, often expressed in ppmv.

Montreal Protocol

Protocol on substances that deplete the ozone layer, signed in Montreal in 1987. It controls the consumption and production of chlorine- and bromine-containing chemicals that destroy stratospheric ozone, such as CFCs, methyl chloroform, carbon tetrachloride, and many others.


Nitrogen oxides

Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced in the emissions of vehicle exhausts and in power stations. In the atmosphere, nitrogen oxides can contribute to formation of photochemical ozone (smog) and to the greenhouse effect.

Nitrous oxide

A powerful greenhouse gas with a global warming potential of 320. Major sources of nitrous oxide (N2O) include soil cultivation practices, fossil fuel combustion and biomass burning.


Process without a simple proportional relation between cause and effect. The climate system contains many non-linear processes, resulting in a system with very complex behavior which may lead to rapid climate change.



An unstable, poisonous allotrope of oxygen; O3, that is formed naturally in the ozone layer from atmospheric oxygen by electric discharge or exposure to ultraviolet radiation, also produced in the lower atmosphere by the photochemical reaction of certain pollutants. It is a highly reactive oxidizing agent used to deodorize air, purify water, and treat industrial wastes. It also is a greenhouse gas.



A rough approximation of current climate processes on average effects of the larger-scale variables in climate models. This is done when processes cannot be modeled explicitly, for example when they are much smaller than the computer grid.


The process in green plants and certain other organisms by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source. Most forms of photosynthesis release oxygen as a byproduct.


Atmospheric compounds that are no greenhouse gases but can enhance greenhouse gas induced processes by contributing to physical or chemical processes regulating greenhouse gas production or destruction rates.

Proxy climate indicator

Variables that are an indirect measure of some combination of climate-related variations back in time. These are used to determine temperature in a time when the thermometer was not yet invented. Examples include tree ring records, characteristics of corals, fraction of melted ice, concentration of salts and acids and the load of pollen trapped in air bubbles.


Radiative forcing

A perturbation of the global radiation balance. This may be human-induced or natural.

Relative Sea Level (RSL)

Sea level measured by a tide gauge with respect to the land upon which it is situated.


Component of the climate system other than the atmosphere that can store certain quantities of substances, such as greenhouse gases and precursors. Examples are oceans, soils and forests.


The process whereby living organisms convert organic matter to CO2, releasing energy and consuming oxygen.

Response time

The time needed for the climate system or its components to re-equilibrate to a new state.


Sea level alteration

A change in global average sea level brought about by volume changes in the world ocean. This may be caused by changes in water density or changes in the total mass of water.


Any process, activity or mechanism which removes a greenhouse gas, an aerosol or a precursor from the atmosphere. It is now possible to achieve Kyoto emission reduction goals by planting forests that take up a sufficient amount of carbon dioxide emissions in a country.


Any process, activity or mechanism which releases a greenhouse gas, an aerosol or a precursor into the atmosphere.

Spatial scale

Climate may vary on a large range of spatial scales. Spatial scales can be local (less than 100.000 km2), regional (100.000-10.000.000 km2), or even continental (10-100.000.000 km2).

Stabilization triangle

Space in de graph depicting greenhouse gas emissions (tones per year) over the past century, between the trend line and the line representing stability at current levels.


A qualitative description of a climate scenario based on extensive literature research and model results. This is often a quite simple description used to fill in policy makers on climate change developments.

System vulnerability

The degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes. This 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.


Temporal scale

Climate may vary on a large range of temporal scales. Temporal scales may be seasonal to even geological, which goes up to hundreds of millions of years.

Thermal expansion

An decrease in water density of oceans that results from global warming. This leads to an expansion of the ocean volume and hence an increase in sea level.

Tide gauge

Device at a coastal location or deep-sea location for continuous measurement of the sea level with respect to the adjacent land.

Turnover time

The ratio of the mass M of a a gaseous compound in the atmosphere and the total rate of removal S of the compound: T = M/S. For each removal process separate turnover times can be defined.



An expression of the degree to which a value (future state) is unknown. Contrary to risk, uncertainty suggests unknown probability of occurrence. Uncertainty can result from lack of information or from disagreement about what is known. It may have many types of sources, from quantifiable errors in the data to ambiguously defined concepts or terminology, or uncertain projections of human behavior. Uncertainty can therefore be represented by quantitative measures or by qualitative statements.


United Nations Framework Convention on Climate Change. A treaty was signed at the Rio Earth Summit in 1992 in which 150 countries promised stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.


Wedge Theory

The theory of opportunities for limiting or diminishing the greenhouse effect and global warming. Wedges include: decarbonised electricity, decarbonised fuels, fuel displacement by alternative energy sources (e.g. solar energy, nuclear energy), methane management, and natural carbon sinks (e.g. forests).


- English dictionary:

- Environmental Protection Agency (EPA)

- IPCC (Intergovernmental Panel on Climate Change)

- Lenntech:

- National Oceanic and Atmospheric Climate Administration (NOAA)

- UNFCCC climate info:

- Van Dale dictionary:

Related pages

Fossil fuels: characteristics and effects

The greenhouse effect mechanism

Emissions and infrared absorption by greenhouse gases

Explanation of the IPCC SRES scenarios

The IPCC SRES scenarios: causes of climate change

The IPCC SRES scenarios: consequences of climate change

Overview of emission reductions for each country according to Kyoto

Possible policy measures to achieve Kyoto targets

Trading emission permits to achieve Kyoto targets

Discussions of the greenhouse effect

History of global warming

Perspectives on the greenhouse effect

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