Originally Posted By: Paul
but you cannot say that the air is always colder than the ground.


You missed the "In daylight" part. That is the key. Or is your problem with the 'always' being too strict?

Originally Posted By: Samwik
To repeat, someone's taken a graph of an IR extinction coefficient in an absorbing medium (CO2) and relabelled it, IMHO.


I am sorry, but I don't understand. What is an extinction coefficient? The way I see it is CO2 will absorb 100% of the IR radiation at about 15 microns. It is difficult to read from that graph, so for argument's sake, I will say that CO2 will only absorb 30% of the energy at 18 microns. As the concentration increases, more of the 18 micron energy will be absorbed, but the amount absorbed at 15 microns will not change. Is this what you mean by a graph of extinction coefficient?