On the Davies paper, there's little doubt that if high cloud cover decreases in height, that can serve as a negative feedback mechanism. (realclimate.org)
in turn higher cloud cover can increase night time temperatures... (answers.com)
Clouds are one of the big unknowns about global warming as they can have a range of effects, warmer temperatures caused by global warming will result in higher rates of evaporation and therefore will result in higher cloud cover. (answers.com)