The earth is like a greenhouse. The mixture of gases in the earth's atmosphere, called Greenhouse Gases (GHG), traps the sun's heat near the surface of the earth, helping to provide a life support environment for the planet. Over thousands of years, the level of GHG in the atmosphere has changed very little. However, the increasing GHG emissions from human activities, in the last one and a half centuries, appear to be breaking this balance.
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