greenhouse gas

A gas that contributes to the greenhouse effect. The six recognized by the Kyoto protocol are the naturally occurring carbon dioxide, methane and nitrous oxide, and the synthetic hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). Water vapour is also a major contributor to the natural greenhouse effect but its concentration in the atmosphere is not directly affected by human activity.

This definition is abridged from A – Z of tree terms: A companion to British arboriculture.
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