The greenhouse Effect

The effect produced as greenhouse gases allow incoming solar radiation to pass through the Earth's atmosphere, but prevent most of the outgoing infrared radiation from the surface and lower atmosphere from escaping into outer space. This process occurs naturally and has kept the Earth's temperature about 60 degrees Fahrenheit warmer than it would otherwise be. Current life on Earth could not be sustained without the natural greenhouse effect.
The Greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapor, carbon dioxide, nitrouse,oxide, and methane, for example).

Credits:

http://www.epa.gov/climatechange/kids/greenhouse.html

http://en.wikipedia.org/wiki/Greenhouse_effect

http://liftoff.msfc.nasa.gov/academy/space/greenhouse.html

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