On average, the Earth is in radiative balance with outgoing infrared radiation equaling absorbed solar radiation. Because there are greenhouse gases in the cooler atmosphere above, the EarthΓÇÖs surface is warmer than it would be without those gases.
The natural greenhouse effect causes the mean temperature of the EarthΓÇÖs surface to be about 33 degrees Celsius warmer than it would be if natural greenhouse gases were not present. This is fortunate, for the natural greenhouse effect creates a climate in which life can thrive and humans can live under relatively benign conditions.
You can see how the greenhouse gases absorb radiation in this simplified diagram illustrating the greenhouse effect. Shortwave solar radiation can pass through the clear atmosphere relatively unimpeded, but longwave infrared radiation emitted by the warm surface of the Earth is absorbed partially and then re-emitted by a number of trace gases ΓÇôparticularly water vapor and carbon dioxideΓÇôin the cooler atmosphere above.
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Some solar radiation is reflected by the Earth and the atmosphere whereas some of the infrared radiation is absorbed and
re-emitted by the greenhouse gases. The effect of this is to warm the surface and the lower atmosphere.
