GCMs=General Circulation ModelsThis paper (and all of the other papers based on empirical data) finds increased CO2 leads to a negative feedback upon water vapor, rather than positive as assumed by the IPCC. The 0.5°C sensitivity is in very close agreement with all of the other papers based on empirical data rather than virtual computer models. Meanwhile, Gavin Schmidt et al at NASA/GISS continue to fiddle with their computer models rather than test them against inconvenient satellite data, and lo and behold come to the conclusion that the IPCC models underestimate sensitivity 30-50%. Gavin makes this proclamation on the basis of computer modeling of the climate 3 million years ago, which given the unproven assumption that CO2 controls all, would require higher climate sensitivity to account for higher temperatures during the Pliocene (2.5-5.5 million years ago). However, had Gavin done the same with the rest of the geologic record -600 million years of which are shown below - he could not possibly come to the same conclusion since CO2 levels show no correlation with temperatures, and CO2 levels were up to 18 times higher than the present throughout an entire ice age about 450 million years ago:
The NASA/GISS/IPCC models are disproven by satellite and balloon data and by the geologic record.
UPDATE: Dr. Roy Spencer's post today also finds climate sensitivity to be 0.5°C and states:
"These results suggest that the sensitivity of the real climate system is less than that exhibited by ANY of the IPCC climate models. This will end up being a serious problem for global warming predictions. You see, while modelers claim that the models do a reasonably good job of reproducing the average behavior of the climate system, it isn’t the average behavior we are interested in. It is how the average behavior will CHANGE.
And the above results show that not one of the IPCC climate models behaves like the real climate system does when it comes to feedbacks during interannual climate variations…and feedbacks are what determine how serious manmade global warming will be."