Well you need heat to melt snow, glaciers, and ice caps. The warming waters and increasing GHGs allow for more evaporation and moisture to be trapped in the troposphere. But we've been wetter too so we precipitate a lot of it out. I haven't followed global humidity and precipitation trends enough though....at least not since I was in school. I'm sure Will and others can comment more on that. It is what it is. We're warming, but the extremists usually need to be ignored. The answer is usually somewhere in the middle.