One of the wild cards in thinking about the effect of climate change on the southwest is the summer monsoon, the rainy season that brings parts of New Mexico, especially in the south, a significant part of their annual precipitation in a few summer months. A new analysis by Benjamin Cook and Richard Seager at Lamont-Doherty suggests no overall change in the amount of precipitation, but a shift to later in the year.
Ben and Richard have done a nice layperson’s writeup (something the Lamont Doherty climate group does as a matter of practice, which I think is a great practice):
The reduced precipitation in April, May and June is very widespread including all of Central America and western and eastern Mexico. The increase in precipitation in September and October is equally widespread.
You can see from their maps that the effect is far greater to the south, in Mexico, but it is nevertheless noticeable in Arizona and New Mexico:
If you’re interested in the monsoon, I recommend a visit to their writeup.