The greenhouse effect is a process by which an atmosphere causes a planet to retain more heat than would be retained by a planet with no atmosphere.
To oversimplify a bit, what happens is that the sun's radiation (which is mostly at relatively high wavelengths – visible and ultraviolet) passes through the atmosphere relatively efficiently, but the corresponding radiation caused by the earth's increased heat (from absorption) is at longer wavelengths which are less efficiently transmitted (i.e. more efficiently absorbed). This causes the earth's surface to be warmer than it would be if it had no atmosphere.
- Can the greenhouse effect be looked at as equivalent to painting the earth a darker color? Or is it somehow more extreme than that? This point isn't explained clearly. --Woozle 13:22, 9 July 2006 (EDT)