Tell Me Why?

The Earth is heated by the Sun’s radiation (shortwave radiation) that passes through the earth's atmosphere where a small portion (about 30 percent) is reflected back into space (by clouds and other reflective surfaces) and the rest (70 percent) is absorbed at Earth's surface (land, oceans, plants, buildings and other objects) and its atmosphere. The absorbed short wave radiation heats (warms) up the earth. Eventually it is readily re-emitted from the earth surface in the form of long wave radiation that goes back into the atmosphere.
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This is necessary since eventually the earth would be too hot to support life. Some of the re-emitted radiation escapes into space (a small amount) while the rest is reflected back to earth by gases in the atmosphere. These gases (called green houses gases) traps the heat (radiation) that would normally escape the atmosphere and goes back into space. These gases act in a way similar to the glass in a greenhouse whereby the Sun’s heat is allowed in but cannot get out thus, the 'Greenhouse Effect'. The green houses gases acting as a form of blanket helps to keep the earth an average of 33 °C warmer. If this greenhouse effect did not occur then Earth would be at least 33°C cooler and too cold to sustain life on Earth. Life on earth would not exist since it would be freezing cold and covered in ice. Therefore, the greenhouse effect keeps the Earth warm.

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Labels: Geography, Physical Geography, Science