I am somewhat curious about the basis for their conclusion that increasing heat will decrease cloud cover, if anything it seems it would have the opposite effect in that global atmospheric humidity would increase...increased clouds would of course increase the planetary albedo, and thus tend to moderate the warming, all other things being equal.
That's the thing about their models. Increase air temperature enough, and yes, it does tend to not hold water as well, but well before that, the ocean is going to evaporate quite a lot adding moisture to the air, which would temporarily cause a green house effect, then it would all come back down rather quickly after moisture forced cloud formation.
Basically, their models call for less cloud cover, or not, either way it can be claimed to be global warming.