zzedzz, it appears that the reason water vapour is dismissed as a major effect is because of it's short residence time in the atmosphere. Whilst that may be the case it seems that the fact that a large volume remains there all the time, even though individual molecules come and go fairly quickly, is not considered relevant. The amount of water vapour that can remain in the atmosphere at any point of time is directly related to the temperature of the atmosphere. Higher temperature allows a higher percentage, and as the percentage increases the more radiation it shields or reflected back from reaching the earths surface. It stands to reason that there will be an equilibrium point reached where as the amount of radiation falls, the amount of evapouration drops and so too the amount of vapour starting the whole cycle over again.
