We know that more open water will put more water vapor in the air, and increase the sunlight absorbed each summer, both of which will lead to yet more warming. (hubpages.com)
For instance, on p187 «higher temperature means more water vapor in the air and therefore fewer clouds» — Presumably, he meant that if the temperature is higher, the relatively humidity could be lower (and so there might be less clouds). (realclimate.org)
However, higher temperatures do cause an increased chance of heavy precipitation events, and it is likely that the flooding in some of this year's U.S. flooding disasters were significantly enhanced by the presence of more water vapor in the air due to global warming. (dotearth.blogs.nytimes.com)