Global Climate Change Glossary (25 entries)

Paris, 26 February 2002

ENVISAT Information Note No. 6
Annex 1
GLOBAL CLIMATE CHANGE: GLOSSARY

Aerosols
A collection of tiny airborne solid or liquid particles, with a typical size between 0.01 and 10 microns (1 micron is one millionth of a metre). They stay in the atmosphere for at least several hours. Aerosols may be of either natural or anthropogenic origin. They may influence climate in two ways: directly through scattering and absorbing radiation, and indirectly through acting as condensation nuclei to assist cloud formation or modifying the optical properties and lifetime of clouds.

Albedo
The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. Clouds and snow-covered surfaces have a high albedo; the albedo of soils ranges from high to low; vegetation and oceans have a low albedo.

Anthropogenic
Resulting from or produced by human beings.

Atmosphere
The gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1% by volume) and oxygen (20.9% by volume), together with other trace gases such as argon (0.93%), carbon dioxide (0.035%) and ozone. Amounts of water vapour are highly variable but typically 1% by volume. The atmosphere also contains clouds and aerosols.

Biomass
The total mass of living organisms in a given area or volume. It includes dead organic matter.

Biosphere
The part of the Earth system comprising all living organisms - in the atmosphere, land (terrestrial biosphere), or oceans (marine biosphere) - as well as dead organic matter.

Carbon cycle
The flow of carbon in various forms (e.g. carbon dioxide) through the atmosphere, ocean terrestrial biosphere and lithosphere (Earth's crust and upper mantle).

Carbon dioxide (CO2)
A naturally occurring gas, also a by-product of burning fossil fuels and biomass, as well as land use changes and other industrial processes. The principal anthropogenic greenhouse gas.

Climate
The "average weather" as measured over a long period of time - typically 30 years.

Climate Change
A statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period of time, typically decades or longer.

Climate model
A numerical representation of the climate system which attempts to include the physical, chemical and biological properties of its components, their interactions and feedback processes, while accounting for all or some of its known properties. Such models are used not only to study and simulate the climate, but for monthly, seasonal and long term predictions.

Cryosphere
The component of the climate system consisting of all snow, ice and permafrost on or beneath the surface of the Earth.

Ecosystem
A system of interacting, living organisms together with their physical environment. They may range from the very small scale (e.g. a pond) to the entire Earth.

El Niño
A warm water current that periodically flows along the coast of Ecuador and Peru, disrupting the local climate and fishery. This oceanic event is associated with the Southern Oscillation - a fluctuation in the pattern of surface air pressure and circulation in the Indian and Pacific Oceans. It has climatic effects throughout the Pacific and in many other parts of the world. The opposite of an El Niño event is called La Niña.

Energy balance
A long term balance, averaged over the entire globe, between incoming solar radiation and outgoing radiation - reflected solar radiation and infrared radiation emitted by the climate system. Human induced or natural changes to these inputs and outputs

Fossil fuels
Fossil carbon deposits e.g. coal, oil, and gas that are burned to produce energy. Their combustion results in emissions of carbon dioxide.

Greenhouse effect
The entrapment of heat by various greenhouse gases in the atmosphere. This occurs through the absorption of infrared radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. The natural greenhouse effect can be enhanced by an increase in the concentration of greenhouse gases through human activity.

Greenhouse gases
The gaseous constituents of the atmosphere, both natural and anthropogenic that absorb and emit infrared radiation (heat). The most important of these are water vapour, carbon dioxide, nitrous oxide, methane and ozone. There are also a number of greenhouse gases that are solely of human origin, e.g.halocarbons

Halocarbons
Compounds containing either bromine, chlorine or fluorine and carbon. These can act as powerful greenhouse gases in the atmosphere. Those containing chlorine and bromine are also involved in the depletion of the ozone layer.

Infra-red radiation
Long wave radiation emitted by the Earth’s surface, atmosphere and clouds, which is generally recognised as heat.

Ozone
The triatomic form of oxygen (O3) which occurs in the troposphere and the stratosphere. Tropospheric ozone acts as a greenhouse gas. It is created both naturally and by photochemical reactions involving gases produced by human activities (“smog”). Stratospheric ozone is an important contributor to the Earth’s radiation balance. Its concentration is highest in the ozone layer.

Sink
Any process, activity or mechanism which removes a greenhouse gas, an aerosol or their precursors from the atmosphere.

Stratosphere
The region of the atmosphere above the troposphere, extending from about 10 km to about 50 km above the surface.

Troposphere
The lowest part of the atmosphere where clouds and weather occur. Its upper boundary (the tropopause) lies at an altitude of about 9 km near the poles, rising to 16 km in the tropics. In the troposphere, temperatures generally decrease with height.