RayP Explains It All

Obi-Wan described the Mos Eisley Spaceport as a place to be cautious, that a Bunny could never find a more wretched den of scum and villainy.  In Eli's humble opinion and that of many others, Obi-Wan never visited USENET.  But even at USENET, one can encounter a passing Jedi, in this case RayP who provides the most economical explanation of the greenhouse effect that the Rabett has seen

For an optically thick atmosphere, it is the Top of the Atmosphere budget plus the lapse rate that dominantly control the surface temperature.  The surface budget is relatively unimportant.  Another way of looking at it is that the atmosphere is so opaque to IR that the radiation to space is determined by just the first one optical depth from the top, which, loosely speaking, reaches into the mid trop.

Perhaps too terse, so let's go to the pictures,