Quote (inkanddagger @ Dec 9 2009 09:37pm)
I looked through all of them myself and still came up with an average of between 60 and 66% from them. The only one that mentions 90% is one studying different sorts of cloud formations and their effects on radiative forcing at the surface.
I am saying 66% to be on the high end, but also because 66% is the number used by the IPCC.
Upon further review, now I know you're lying. I just looked through every one of them that had links, and googled the rest that I could find, and the
LOWEST figure I could find was 86% for combined water vapor and cloud cover. (Not local cloud cover, but global, since we're discussing global climate change, and there is always cloud cover over significant portions of the world). Most pin the figure between 95-97%.
Subsequently, taking into consideration the saturation level of radiation absorption, the increases in CO2 necessary to raise temperature become exponential. That would mean that if we assume the high side of your estimate of 1.8C, it would require a doubling of the CO2 level to obtain another 1.8C.
From one of those references:
Note added 1/5/2008:
Some authors [15] suggest that the percentage of warming attributable to CO2 is not 5%, but is closer to 26%. It is easy to show why the 26% estimate (and estimates similar to it) are almost certainly wrong. We know that the total warming from greenhouse gases is 33K. If 26% of this was from CO2, then doubling CO2 would raise temperatures by 0.26*33 or 8.6K. Since the 26% estimate is based on total radiation absorbed, and not the amount of warming, we would have to add secondary feedback effects to this figure. This would double or even triple the value, giving us a predicted temperature increase of up to 25° C, or a predicted global average temperature of 40°C (104°F). Balmy!