greenhouse+gases

=**Greenhouse Gasses**= ====**Greenhouse gases** are components of the [|atmosphere] that contribute to the [|greenhouse effect]. Without the greenhouse effect the Earth would be uninhabitable; in its absence, the mean temperature of the earth would be about −19 °C (−2 °F, 254 K) rather than the present mean temperature of about 15 °C (59 °F, 288 K). Greenhouse gases include in the order of relative abundance [|water vapour], [|carbon dioxide], [|methane], nitrous oxide, and [|ozone]. Greenhouse gases come from natural sources and human activity.==== ====The major greenhouse gases are [|water vapor], which causes about 36–70% of the greenhouse effect on Earth ( not including clouds); [|carbon dioxide], which causes 9–26%; [|methane], which causes 4–9%, and [|ozone], which causes 3–7%. It is not possible to state that a certain gas causes a certain percentage of the [|greenhouse effect], because the influences of the various gases are not additive. (The higher ends of the ranges quoted are for the gas alone; the lower ends, for the gas counting overlaps.) Other greenhouse gases include, but are not limited to, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons and chlorofluorocarbons (see IPCC list of greenhouse gases).====

Anthropogenic greenhouse gases
The concentrations of several greenhouse gases have increased over time. [|Human] activity may increase the greenhouse effect through release of carbon dioxide, but human influences on other greenhouse gases can also be important. Some of the main sources of greenhouse gases due to human activity include: The seven sources of CO2 from fossil fuel combustion are (with percentage contributions for 2000–2004):
 * burning of [|fossil fuels] and deforestation leading to higher carbon dioxide concentrations;
 * livestock and paddy [|rice] farming, land use and wetland changes, pipeline losses, and covered vented landfill emissions leading to higher methane atmospheric concentrations. Many of the newer style fully vented septic systems that enhance and target the fermentation process also are major sources of atmospheric methane;
 * use of chlorofluorocarbons (CFCs) in refrigeration systems, and use of CFCs and  halons in  fire suppression systems and manufacturing processes.
 * agricultural activities, including the use of fertilizers, that lead to higher nitrous oxide concentrations.
 * 1) Solid fuels (e.g. [|coal]): 35%
 * 2) Liquid fuels (e.g.  gasoline): 36%
 * 3) Gaseous fuels (e.g. [|natural gas]): 20%
 * 4) Flaring gas industrially and at wells: <1%
 * 5) Cement production: 3%
 * 6) Non-fuel hydrocarbons: <1%
 * 7) The "international  bunkers" of shipping and air transport not included in national inventories: 4%