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Climate Change Terms

Climate Change Terms


Abrupt Climate Change


Adaptive Capacity

Small particles or liquid droplets in the atmosphere that can absorb or reflect sunlight depending on their composition.



Alternative Energy

Annex I Countries/Parties
Group of countries included in Annex I (as amended in 1998) to the United Nations Framework Convention on Climate Change, including all the developed countries in the Organization of Economic Co-operation and Development, and economies in transition. By default, the other countries are referred to as Non-Annex I countries. Under Articles 4.2 (a) and 4.2 (b) of the Convention, Annex I countries commit themselves specifically to the aim of returning individually or jointly to their 1990 levels of greenhouse gas emissions by the year 2000.



Atmospheric Lifetime
Atmospheric lifetime is the average time that a molecule resides in the atmosphere before it is removed by chemical reaction or deposition. In general, if a quantity of a compound is emitted into the atmosphere at a particular time, about 35 percent of that quantity will remain in the atmosphere at the end of the compound's atmospheric lifetime. This fraction will continue to decrease in an exponential way, so that about 15 percent of the quantity will remain at the end of two times the atmospheric lifetime, etc. (Some compounds, most notably carbon dioxide, have more complex lifecycles, and their atmospheric lifetimes are not defined by a simple exponential equation.) Greenhouse gas lifetimes can range from a few years to a few thousand years.




Biogeochemical Cycle



Black Carbon Aerosol
Black carbon (BC) is the most strongly light-absorbing component of particulate matter (PM), and is formed by the incomplete combustion of fossil fuels, biofuels, and biomass. It is emitted directly into the atmosphere in the form of fine particles (PM2.5).

Any exploratory hole drilled into the Earth or ice to gather geophysical data. Climate researchers often take ice core samples, a type of borehole, to predict atmospheric composition in earlier years. S



Carbon Cycle

Carbon Dioxide
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 human caused 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 Equivalent


Carbon Dioxide Fertilization

Carbon Footprint

Carbon Sequestration
Terrestrial, or biologic, carbon sequestration is the process by which trees and plants absorb carbon dioxide, release the oxygen, and store the carbon. Geologic sequestration is one step in the process of carbon capture and sequestration (CCS), and involves injecting carbon dioxide deep underground where it stays permanently.

Carbon Capture and Sequestration

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: hydrochlorofluorocarbons, an interim replacement for CFCs that are also covered under the Montreal Protocol, and hydrofluorocarbons, which are covered under the Kyoto Protocol. All these substances are also greenhouse gases.


Climate Change

Climate Feedback
A process that acts to amplify or reduce direct warming or cooling effects.

Climate Lag
The delay that occurs in climate change as a result of some factor that changes only very slowly. For example, the effects of releasing more carbon dioxide into the atmosphere occur gradually over time because the ocean takes a long time to warm up in response to a change in radiation.

Climate Model

Climate Sensitivity

Climate System (or Earth System)

Coal Mine Methane
Coal mine methane is the subset of coalbed methane that is released from the coal seams during the process of coal mining.

Coalbed Methane

The benefits of policies that are implemented for various reasons at the same time including climate change mitigation acknowledging that most policies designed to address greenhouse gas mitigation also have other, often at least equally important, rationales (e.g., related to objectives of development, sustainability, and equity).


Conference of the Parties
The supreme body of the United Nations Framework Convention on Climate Change (UNFCCC). It comprises more than 180 nations that have ratified the Convention. Its first session was held in Berlin, Germany, in 1995 and it is expected to continue meeting on a yearly basis. The COP's role is to promote and review the implementation of the Convention. It will periodically review existing commitments in light of the Convention's objective, new scientific findings, and the effectiveness of national climate change programs.

Coral Bleaching
The process in which a coral colony, under environmental stress expels the microscopic algae (zooxanthellae) that live in symbiosis with their host organisms (polyps). The affected coral colony appears whitened.

One of the interrelated components of the Earth's system, the cryosphere is frozen water in the form of snow, permanently frozen ground (permafrost), floating ice, and glaciers. Fluctuations in the volume of the cryosphere cause changes in ocean sea level, which directly impact the atmosphere and biosphere.





Dryland Farming
A technique that uses soil moisture conservation and seed selection to optimize production under dry conditions.



The extent to which the Earth's orbit around the Sun departs from a perfect circle.


El Niño - Southern Oscillation (ENSO)


Emissions Factor

Energy Efficiency
Using less energy to provide the same service.


Enhanced Greenhouse Effect
The concept that the natural greenhouse effect has been enhanced by increased atmospheric concentrations of greenhouse gases (such as CO2 and methane) emitted as a result of human activities. These added greenhouse gases cause the earth to warm.

Enteric Fermentation
Livestock, especially cattle, produce methane as part of their digestion. This process is called enteric fermentation, and it represents one third of the emissions from the agriculture sector.

The process by which water changes from a liquid to a gas or vapor.




Feedback Mechanisms

Fluorinated Gases
Powerful synthetic greenhouse gases such as hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for stratospheric ozone-depleting substances (e.g., chlorofluorocarbons, hydrochlorofluorocarbons, and halons) and are often used in coolants, foaming agents, fire extinguishers, solvents, pesticides, and aerosol propellants. These gases are emitted in small quantities compared to carbon dioxide (CO2), methane (CH4), or nitrous oxide (N2O), but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases (High GWP gases).


Forcing Mechanism

Fossil Fuel

Fuel Switching
In general, this is substituting one type of fuel for another. In the climate-change discussion it is implicit that the substituted fuel produces lower carbon emissions per unit energy produced than the original fuel, e.g., natural gas for coal.



General Circulation Model (GCM)



Global Average Temperature
An estimate of Earths mean surface air temperature averaged over the entire planet.

Global Warming

Global Warming Potential

Greenhouse Effect
Trapping and build-up of heat in the atmosphere (troposphere) near the Earths surface. Some of the heat flowing back toward space from the Earth's surface is absorbed by water vapor, carbon dioxide, ozone, and several other gases in the atmosphere and then reradiated back toward the Earths surface. If the atmospheric concentrations of these greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase.

Greenhouse Gas (GHG)
Any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include, carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride.



Habitat Fragmentation
A process during which larger areas of habitat are broken into a number of smaller patches of smaller total area, isolated from each other by a matrix of habitats unlike the original habitat.


Heat Island

Heat Waves


Hydrochlorofluorocarbons (HCFCs)

Hydrofluorocarbons (HFCs)

Hydrologic Cycle




Ice Core

Indirect Emissions
Indirect emissions from a building, home or business are those emissions of greenhouse gases that occur as a result of the generation of electricity used in that building. These emissions are called "indirect" because the actual emissions occur at the power plant which generates the electricity, not at the building using the electricity.

Industrial Revolution

Infrared Radiation
Infrared radiation consists of light whose wavelength is longer than the red color in the visible part of the spectrum, but shorter than microwave radiation. Infrared radiation can be perceived as heat. The Earths surface, the atmosphere, and clouds all emit infrared radiation, which is also known as terrestrial or long-wave radiation. In contrast, solar radiation is mainly short-wave radiation because of the temperature of the Sun.

Intergovernmental Panel on climate Change (IPCC)

The submergence of land by water, particularly in a coastal setting. 





Least Developed Country
A country with low indicators of socioeconomic development and human resources, as well as economic vulnerability, as determined by the United Nations.

Longwave Radiation
Radiation emitted in the spectral wavelength greater than about 4 micrometers, corresponding to the radiation emitted from the Earth and atmosphere. It is sometimes referred to as 'terrestrial radiation' or 'infrared radiation,' although somewhat imprecisely.



Cities with populations over 10 million.

Methane (CH4)

Metric Ton


Mount Pinatubo

Municipal Solid Waste (MSW)



Natural Gas

Natural Variability
Variations in the mean state and other statistics (such as standard deviations or statistics of extremes) of the climate on all time and space scales beyond that of individual weather events. Natural variations in climate over time are caused by internal processes of the climate system, such as El Niño as well as changes in external influences, such as volcanic activity and variations in the output of the sun.

Nitrogen Cycle
The natural circulation of nitrogen among the atmosphere, plants, animals, and microorganisms that live in soil and water. Nitrogen takes on a variety of chemical forms throughout the nitrogen cycle, including nitrous oxide (N2O) and nitrogen oxides (NOx).

Nitrogen Oxides (NOx)

Nitrous Oxide (N2O)

Natural emissions of N2O are mainly from bacteria breaking down nitrogen in soils and the oceans. Nitrous oxide is mainly removed from the atmosphere through destruction in the stratosphere by ultraviolet radiation and associated chemical reactions, but it can also be consumed by certain types of bacteria in soils.

Non-Methane Volatile Organic Compounds (NMVOCs)



Ocean Acidification
Increased concentrations of carbon dioxide in sea water causing a measurable increase in acidity (i.e., a reduction in ocean pH). This may lead to reduced calcification rates of calcifying organisms such as corals, mollusks, algae and crustaceans.

To chemically transform a substance by combining it with oxygen.

Ozone, the triatomic form of oxygen (O3), is a gaseous atmospheric constituent. In the troposphere, it is created by photochemical reactions involving gases resulting both from natural sources and 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. Depletion of stratospheric ozone, due to chemical reactions that may be enhanced by climate change, results in an increased ground-level flux of ultraviolet (UV-) B radiation.

Ozone Depleting Substance (ODS)

Ozone Layer

Ozone Precursors



Particulate matter (PM)

Parts Per Billion (ppb)

Parts Per Million by Volume (ppmv)

Parts Per Trillion (ppt)
Number of parts of a chemical found in one trillion parts of a particular gas, liquid or solid.

Perfluorocarbons (PFCs)

Perennially (continually) frozen ground that occurs where the temperature remains below 0ºC for several years.

The timing of natural events, such as flower blooms and animal migration, which is influenced by changes in climate. Phenology is the study of such important seasonal events. Phenological events are influenced by a combination of climate factors, including light, temperature, rainfall, and humidity.


The wobble over thousands of years of the tilt of the Earths axis with respect to the plane of the solar system.




Radiative Forcing


The ability of a surface material to reflect sunlight including the visible, infrared, and ultraviolet wavelengths.


Relative Sea Level Rise
The increase in ocean water levels at a specific location, taking into account both global sea level rise and local factors, such as local subsidence and uplift. Relative sea level rise is measured with respect to a specified vertical datum relative to the land, which may also be changing elevation over time.

Renewable Energy
Energy resources that are naturally replenishing such as biomass, hydro, geothermal, solar, wind, ocean thermal, wave action, and tidal action.

Residence Time
The average time spent in a reservoir by an individual atom or molecule. With respect to greenhouse gases, residence time refers to how long on average a particular molecule remains in the atmosphere. For most gases other than methane and carbon dioxide, the residence time is approximately equal to the atmospheric lifetime.





Salt Water Intrusion
Displacement of fresh or ground water by the advance of salt water due to its greater density, usually in coastal and estuarine areas.


Sea Surface Temperature
The temperature in the top several feet of the ocean, measured by ships, buoys and drifters.


Short Ton


A seasonal accumulation of slow-melting snow.

Soil Carbon

Solar Radiation

Storm Surge


Stratospheric Ozone
See ozone layer.


The downward settling of the Earth's crust relative to its surroundings.

Sulfate Aerosols
Particulate matter that consists of compounds of sulfur formed by the interaction of sulfur dioxide and sulfur trioxide with other compounds in the atmosphere. Sulfate aerosols are injected into the atmosphere from the combustion of fossil fuels and the eruption of volcanoes like Mt. Pinatubo. Sulfate aerosols can lower the Earth's temperature by reflecting away solar radiation (negative radiative forcing). General Circulation Models which incorporate the effects of sulfate aerosols more accurately predict global temperature variations. See particulate matter, aerosol, General Circulation Models.

Sulfur Hexafluoride (SF6)
A colorless gas soluble in alcohol and ether, slightly soluble in water. A very powerful greenhouse gas used primarily in electrical transmission and distribution systems and as a dielectric in electronics. The global warming potential of SF6 is 22,800. This GWP is from the IPCC's Fourth Assessment Report (AR4). See Global Warming Potential.



1 trillion (1012) grams = 1 million (106) metric tons.

Thermal Expansion
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, which leads to an increase in sea level.

Thermohaline Circulation

Trace Gas


Tropospheric Ozone (O3)
See ozone.

Tropospheric Ozone Precursors
See ozone precursors.

A treeless, level, or gently undulating plain characteristic of the Arctic and sub-Arctic regions characterized by low temperatures and short growing seasons.



Ultraviolet Radiation (UV)

United Nations Framework Convention on Climate Change (UNFCCC)
Under the Convention, governments:

  • cooperate in preparing for adaptation to the impacts of climate change

The Convention entered into force on 21 March 1994.







Water Vapor
The most abundant greenhouse gas, it is the water present in the atmosphere in gaseous form. Water vapor is an important part of the natural greenhouse effect. While humans are not significantly increasing its concentration through direct emissions, it contributes to the enhanced greenhouse effect because the warming influence of greenhouse gases leads to a positive water vapor feedback. In addition to its role as a natural greenhouse gas, water vapor also affects the temperature of the planet because clouds form when excess water vapor in the atmosphere condenses to form ice and water droplets and precipitation. See greenhouse gas.



100-Year Flood Levels
Severe flood levels with a one-in-100 likelihood of occurring in any given year.

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