the basis for the claim that CO2 is the more important greenhouse gas seems to be based on it's longer residence time in the atmosphere. Water vapour is dismissed because of it's short residence time, yet the water vapour constantly transports heat absorbed on earths surface to the atmospher where it is released. As the atmospheric temperature rises so does the ability of it to suspend a higher concentration of water vapour. The short residence time is therefore irrelevant as there is always percentage of water vapor in the atmosphere relative to the temperature and thus it's impact on reflecting solar radiation in turn then reduces the heat reaching the earths surface which in turn reduces the amount of evaporation taking place. CO2 will complement the effects but the water vapour is part of a self limiting process.
