I ran across an article, in The National Business Review (NZ), that (attempts to) explain why the climate is not highly sensitive to CO2 warming.

In December last year . . . (the author) heard . . . a paper . . . that showed while the IPCC models predict that greenhouse gases would produce an extensive "hot spot" in the upper troposphere over the tropics, the satellite measurements show no such hotspots have appeared. . . .

a large part of this discrepancy is the result of some basic errors in the IPCC's assessment of the Stefan-Boltzmann equation. When they applied their revised factor to the effect of greenhouse gases, the temperature rise was about a third of that predicted by the IPCC. . . .

The findings that the predicted "tropical hot spots" do not exist are important because the IPCC models assume these hot spots will be formed by increased evaporation from warmer oceans leading to the accumulations of higher concentrations of water vapour in the upper atmosphere, and thereby generating a positive feedback reinforcing the small amount of warming that can be caused by CO2 alone. . . .