Hi Sam: There were several problems with that post, but the fundamental one is that the CO2 absorption bands are NOT saturated in the upper cold atmosphere, so arguments about warm, moist sea level conditions are beside the point. In order for IR to make it out into space it must go through all the atmosphere, so who cares what the first 10 meters does? When the IR final reaches the upper atmosphere it indeed sees a difference if the CO2 is more or less than current conditions. Note that saturation for IR from the surface is not the issue, its the final IR energy transport out the upper atmosphere that counts. The cascade of surface emission, and various atmospheric transport methods that get the energy to the upper atmosphere have lots of detailed complications, but in the end, its the upper atmosphere which must provide the final IR window out to space, so hence its conditions are the key here.
The longer answer involves the fact that the "bands" look smeared out and continuos in the higher pressure, warmer lower atmosphere, but look comb like (a sequence of narrow bands) in the cold upper low pressure atmosphere, and that is why H20 does not in fact saturate the CO2 bands as well, hence increased C02 in fact has an effect even in the H20 "bands". The H20 comb fingers don't in fact exactly overlap the C02 combs in the broad regions where the smeared bands do. Details... |
