Graphic Wall Words

I used to read liberal magazines, and one thing I noticed was a lot of articles and book ads, about controlling a debate by manipulating the words used (except they'd call it something like "take back the language")

As shown by the small graphic at the lower right, only 1/6th of the energy received from the sun is directly re radiated back from the surface. The other 5/6th leaves as thermal radiation. This would be convection and conduction transferring heat to the upper atmosphere, were it would freely radiate to space (a near vacuum is nearly transparent to IR energy - its a form of light).

Greenhouses hold in heat largely by blocking convection. A glass wall makes a poor greenhouse, because the heat rises away. An analogy should help visualize an effect, not ignore the largest factor. Any ideas for a better analogy?

http://www.globalwarmingart.com/wiki/Image:Atmospheric_Transmission_png