Greenhouse gases (GHGs) are the gases present in the earth's atmosphere which reduce the loss of heat into space and therefore contribute to global temperatures through the greenhouse effect.
Greenhouse gases are essential to maintaining the temperature of the Earth; without them the planet would be so cold as to be uninhabitable.[1][2]
However, an excess of greenhouse gases can raise the temperature of a planet to lethal levels, as on Venus where the 90 bar partial pressure of carbon dioxide (CO2) contributes to a surface temperature of about 467 °C (872 °F).
Greenhouse gases are produced by many natural and industrial processes, which currently result in CO2 levels of 380 ppmv in the atmosphere.
The most important greenhouse gases are:
* water vapor, which causes about 36–70% of the greenhouse effect on Earth. (Note clouds typically affect climate differently from other forms of atmospheric water.)
* carbon dioxide, which causes 9–26%
* methane, which causes 4–9%
* ozone, which causes 3–7%
Global Carbon Emission by Type to Y2004
This figure shows the relative fraction of man-made greenhouse gases coming from each of eight categories of sources, as estimated by the Emission Database for Global Atmospheric Research version 3.2, fast track 2000 project
Annual Greenhouse Gas by Sector
Per Capita emission by Country : year 2000
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Sunday, August 3, 2008
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