David T.C. Davies

To ask the Secretary of State for Energy and Climate Change what information his Department holds on the percentage contribution of (a) carbon dioxide, (b) water vapour and (c) methane to the greenhouse gas effect. ( 310485 )

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Joan Ruddock

Scientific publications on the subject, for example, Kiehl and Trenberth (1997, Bulletin of the American Meteorological Society) report that carbon dioxide contributes around 27 per cent. to the globally averaged greenhouse gas effect, water vapour around 60 per cent., and methane about 3 per cent. The amount of water vapour present, and hence its contribution to the greenhouse gas effect, depends on the temperature of the atmosphere. It therefore acts to amplify the contribution of the other greenhouse gases.

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