Greenhouse gases

Scientific consensus has identified carbon dioxide as the dominant greenhouse gas forcing. (The dominant greenhouse gas overall is water vapor. Water vapor, however, has a very short atmospheric lifetime (about 10 days) and is very nearly in a dynamic equilibrium in the atmosphere, so it is not a forcing gas in the context of global warming. Methane and nitrous oxide are also major forcing contributors to the greenhouse effect. The Kyoto Protocol lists these together with Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), and Sulphur hexafluoride (SF6), which contribute to climate change primarily by interfering with atmospheric ozone concentrations. The chart at right attributes anthropogenic greenhouse gas emissions to eight main economic sectors, of which the largest contributors are power stations (many of which burn coal or other fossil fuels), industrial processes (among which cement production is a dominant contributor, transportation fuels (generally fossil fuels), and agricultural byproducts (mainly methane from enteric fermentation and nitrous oxide from fertilizer use.