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Definition of Terms Used Within the DDC Pages

Glossary B

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

B1 and B2

See SRES scenarios.


British Atmospheric Data Centre


The baseline (or reference) is the state against which change is measured. A baseline period is the period relative to which anomalies are computed. The baseline concentration ofa trace gas is that measured at a location not influenced by local anthropogenic emissions. WGI

In the context of transformation pathways, the term 'baseline scenarios' refers to scenarios that are based on the assumption that no mitigation policies or measures will be implemented beyond those that are already in force and/or are legislated or planned to be adopted. Baseline scenarios are not intended to be predictions of the future, but rather counterfactual constructions that can serve to highlight the level of emissions that would occur without further policy effort. Typically, baseline scenarios are then compared to mitigation scenarios that are constructed to meet different goals for greenhouse gas (GHG) emissions, atmosphereic concentrations, or temperature change. The term 'baseline scenario' is used interchangeably with 'reference scenario' and 'no policy scenario'. In much of the literature the term is also synonymous with the term 'business-as-usual (BAU) scenario', although the term 'BAU' has fallen out of favour because the idea of business-as-usual in century-long socioeconomic projections is hard to fathom. WGIII

See also Climate scenario, Emission scenario, Representative concentration pathways (RCPs), Socio-economic scenarios, and SRES scenarios.

Biosphere (Terrestrial and Marine)

The part of the Earth system comprising all ecosystems and living organisms, in the atmosphere, on land (terrestrial biosphere) or in the oceans (marine biosphere), including derived dead organic matter, such as litter, soil organic matter and oceanic detritus. WGIII

Black Carbon (BC)

Operationally defined aerosol species based on measurement of light absorption and chemical reactivity and/or thermal stability. It is sometimes referred to as soot. BC is mostly formed by the incomplete combustion of fossil fuels, biofuels, and biomass but it also occurs naturally. It stays in the atmosphere only for days or weeks. It is the most strongly light-absorbing component of particulate matter (PM) and has a warming effect by absorbing heat into the atmosphere and reducing the albedo when deposited on ice or snow. WGIII


Bundesminesterium für Bildung und Forschung / Federal Ministry of Education and Research