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II. The Greenhouse Effect

Here is the basic idea of the greenhouse effect. When sunlight hits the earth it

warms its ground temperature. The warm earth then emits infrared radiation to cool

itself. This escaping radiation is absorbed by greenhouse gasses (GHGs) in the

atmosphere. These gasses do not absorb most of the incoming shortwave radiation but

do absorb most of the outgoing longwave radiation. The cooling earth warms the

atmosphere, which then radiates some of that heat back down to the earth. This is

Fig. 1. The basic principle of the greenhouse effect. Source: IPCC. "Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change" FAQ 1.3.