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ome gases in the atmosphere keep the Earth warm enough for life to exist at all. Otherwise, our planet would be cold and lifeless. Carbon dioxide and other heat-trapping gases retain part of the Sun's energy and reflect back the rest, keeping us from being scorched during the day and from freezing at night. This natural warming of the lower atmosphere by about 60 degrees Fahrenheit (15.6 degrees Celsius) is called "the greeenhouse effect."

The Greenhouse Effect: How Does it Work?

Heat-trapping or greenhouse gases include carbon dioxide along with water vapor, methane, chlorofluorocarbons (CFCs), ozone and nitrous oxide. These gases cause the atmosphere to act like the glass in a greenhouse or car window which lets in light or short-wave radiation from the Sun and traps the heat inside. Some of the solar radiation is absorbed by the rocks, waters, living organisms and manmade structures on the Earth's surface, while the rest is reradiated back from the warm surface into the atmosphere in the form of long-wave, infrared radiation called heat energy. Part of this heat energy is reabsorbed by the greenhouse gases which keeps the lower atmosphere much warmer--without these heat-trapping gases, our the planet would be as inhospitable as the moon. The rest of the heat energy escapes back out into space. This balance of incoming and outgoing radiation determines the Earth's temperature.

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