A paper published yesterday in Climate Dynamics illustrates just a few of the large unresolved problems in modeling clouds, the largest source of climate modelling uncertainty. The authors attempted but were unable to reconcile cloud radiative effects with global precipitation and the atmospheric energy budget due to doubled CO2 concentration, unless the sign of cloud radiative effects is changed from positive [as falsely assumed by all IPCC models] to strongly negative.
According to the paper,
"because clouds are a large source of modelling uncertainty, we consider whether resolving errors in cloud simulation could reconcile modelled global mean precipitation trends of about 1–3 % K−1 with some estimates of observed trends of 7 % K−1 or more. This would require the radiative effect of clouds to change from one that increases atmospheric radiative absorption by about 0.5 Wm−2 K−1 to one that decreases it by −3.5 Wm−2 K−1 . Based on our results, this seems difficult to achieve within our current rationale for the tropics at least."
In other words, the net radiative effect of increased clouds from warming & increased evaporation of water vapor would be to decrease IR radiative absorption & increase IR radiative cooling of the atmosphere, an anti-greenhouse effect. Thus, IPCC climate models don't have either the magnitude or even the sign of radiative forcing from clouds correct, one of several reasons why the models greatly exaggerate warming and have been falsified at confidence levels of 95-98%+.
As Dr. Roy Spencer notes,Climate Dynamics May 2014
"The most obvious way for warming to be caused naturally is for small, natural fluctuations in the circulation patterns of the atmosphere and ocean to result in a 1% or 2% decrease in global cloud cover. Clouds are the Earth’s sunshade, and if cloud cover changes for any reason, you have global warming — or global cooling."