Definition: Greenhouse gas
Greenhouse gases (GHG) make up less than 0.1 % of the total atmosphere, which consists mostly of nitrogen and oxygen. Carbon dioxide is by far the most common greenhouse gas. The main greenhouse gases include: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), as well as ozone depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) - these latter two groups of gases are not covered by the Kyoto Protocol.
Source: "Using Official Statistics to Calculate Greenhouse Gas Emissions. A Statistical Guide"
A gas that contributes to the natural greenhouse effect. The Kyoto Protocol covers a basket of six greenhouse gases (GHGs) produced by human activities: Carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride. Annex I Parties' emissions of these gases taken together are to be measured in terms of carbon dioxide equivalents on the basis of the gases' global warming potential. An important natural GHG not covered by the Protocol is water vapour.
Source: "The Environmental Goods and Services Sector"
Eurostat, "Using Official Statistics to Calculate Greenhouse Gas Emissions. A Statistical Guide", Publications Office of the European Union, Luxembourg, 2010