sensitivity.brian

First I downloaded a climatology from Cecile Hannay. It is the CAM with a slab ocean model (SOM). There is a control and a double-CO2 run, and the "sensitivity" is calculated at each point by taking the difference in temperature at 900 hPa (not quite the surface, but close enough for me)[png][eps]. Also, the same calculation was performed at 200 hPa, just to see how it compares [png][eps]. The globally averaged (area-weighted) response at 900 hPa is 4.4e-3 K ppmv^{-1}. That should be about a 1.56 K warming for doubling CO2 from 1990 levels.

Next, I tried doing the same thing with my prescribed SST (no sea-ice) aqua planet. The difference, besides the lower boundary, is that my perturbed climate here was given double preindustrial CO2, i.e., 560 ppmv, instead of 710 ppmv. By standardizing the response, that won't matter much. The global mean change at 900 hPa is 0.12e-3 K/ppmv, much smaller than with continents and a thermodynamic SST. That difference would be about 0.04 K warming with doubling CO2. [png][eps]