Various methods have been used to test whether the codes adequately simulate these processes. The example given above in Figure 22 of cooling and subsequent warming due to the Mt. Pinatubo eruption is a modest test that was successful. In addition both seasonal and latitudinal change, which are adequately simulated require correct modeling of these processes. On the other hand, one failing of most climate models is that they produce an upper troposphere in the tropics that is both too moist and too warm. This deficiency, if it is amplified by warming, would cause over estimation of the positive feedback due to water vapor.
Cloudiness is also of concern.
At present it is estimated that a GHG warmed climate will not strongly change the relative cloud feedback. Still only small differences in cloudiness can have a strong influence on the Earth's energy budget. Thus, while these processes are thought to be adequately simulated, our inability to handle them more precisely remains the primary source of uncertainty in attributing the observed warming to human influence.