Dr. Roy Spencer has compared the output of 73 climate models to actual recent temperature measurements. He has focused on temperatures in the mid-troposphere in the tropics -- this is not the same as global surface temperatures but is of course related. The reason for this focus is 1) we have some good space-based data sources for temperatures in this region that don't suffer the same biases and limitations as surface thermometers and 2) This is the zone that catastrophic anthropogenic global warming theory says should be seeing the most warming, due to positive feedback effects of water vapor. The lines are the model results for temperatures, the dots are the actuals.
I continue to suspect that the main source of disagreement is that the models’ positive feedbacks are too strong…and possibly of even the wrong sign.
The lack of a tropical upper tropospheric hotspot in the observations is the main reason for the disconnect in the above plots, and as I have been pointing out this is probably rooted in differences in water vapor feedback. The models exhibit strongly positive water vapor feedback, which ends up causing a strong upper tropospheric warming response (the “hot spot”), while the observation’s lack of a hot spot would be consistent with little water vapor feedback.
The warming from manmade CO2 without positive feedbacks would be about 1.3C per doubling of CO2 concentrations, a fraction of the 3-10C predicted by these climate models. If the climate, like most other long-term stable natural systems, is dominated by negative feedbacks, the sensitivity would be likely less than 1C. Either way, the resulting predicted warming from manmade CO2 over the rest of this century would likely be less than 1 degree C.