Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental. Panel on Climate Change. Figure 10.18 (b), Cambridge University Press.

Because a warmer planet will boost evaporation and change atmospheric moisture circulation, many dry areas will become drier and wet areas wetter. In North America, on average, precipitation is likely to be less frequent but more intense when it does fall.

Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental. Panel on Climate Change. Figure 10.18 (d), Cambridge University Press.

This may mean that the American Southwest becomes drier. Indeed, we have already begun to see these trends in the past few decades. And along with increased droughts comes an increased potential for wildfires.