Glossary A

Glossary of acronyms and specialised terms on the IPCC-DDC website.
The definitions shown here are from the IPCC Fifth Assessment Report (AR5) working group glossaries: WGI, WGII and WGIII. The source working group is indicated on each definition.

A | B | C | D | E | F-G | H-I | J-K | L-M | N-O | P-Q | R | S | T | U-V | W-Z

A1, A1F1, A1T, A1B and A2

See SRES scenarios.

Adaptation

The process of adjustment to actual or expected climate and its effects. In human systems, adaptation seeks to moderate harm or exploit beneficial opportunities. In natural systems, human intervention may facilitate adjustment to expected climate and its effects. WGIII

Adaptation Capacity

The ability of systems, institutions, humans, and other organisms to adjust to potential damage, to take advantage of opportunities, or to respond to consequences. WGIII

Aerosol

A suspension of airborne solid or liquid particles, with a typical size between a few nanometres and 10 micrometres that reside in the atmosphere for at least several hours. For convenience the term aerosol, which includes both the particles and the suspendig gas, is often used in its plural form to mean aerosol particles. Aerosols may be of either natural or anthropogenic origin. Aerosols may influence climate in several ways: directly through scattering and absorbing radiation, and indirectly by acting as cloud condensation nuclei or modifying the optical properties and lifetime of clouds. WGI

Albedo

The fraction of solar radiation reflected by a surface or object, often expressed as a percentage. Snow-covered surfaces have a high albedo, the albedo of soils ranges from high to low, and vegetation-covered surfaces and oceans have a low albedo. The Earth's planetary albedo varies mainly through varying cloudiness, snow, ice, leaf area and land cover changes. WGI

AMIP

Atmospheric Model Intercomparison Project

Anthropogenic

Resulting from or produced by human activities. WGI

AR4

Fourth IPCC Assessment Report

ASCII

American Standard Code for Information Interchange. ASCII is a character encoding scheme

Atmosphere

The gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1% volume mixing ratio) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93% volume mixing ratio), helium and addiatively active greenhouse gases such as carbon dioxide (0.035% volume mixing ratio) and ozone. In addition, the atmosphere contains the greenhouse gas water vapour, whose amounts are highly variable but typically around 1% volume mixing ratio. the atmoshere also contains clouds and aerosols. WGI