Anthony Watts claims a scientist ignored his own work on US droughts

Anthony Watts latest claim (archived here, latest here) is that a scientist ignored his own research. At Anthony's climate conspiracy blog today, he copied and pasted a press release about a new paper on the Californian drought. Anthony wrote his article under the headline "Ridiculous claim from Columbia University: ‘Warming climate is deepening California drought". He thinks that it's ridiculous to think that evaporation will be higher under hotter conditions. He doesn't understand the basics of science at all. He also wrote:

From the THE EARTH INSTITUTE AT COLUMBIA UNIVERSITY and the department of “intense droughts only occur in the age of the SUV” department, where they apparently failed to take the climatic history of the region into account:

And he put up a chart that he claimed came from from one of the authors of the new paper (though Anthony clearly didn't know that), in an attempt to dismiss this new work. In any case, it didn't. His graphic wasn't in the 2007 paper and the graphic didn't refute the new paper:

Human influence on the Californian drought

A much more acute situation

Daniel Swain and Noah Diffenbaugh and colleagues have been looking at the current drought in California to see if global warming has played a part. Earlier this year, their work was reported by Stanford:

The current drought is different from many of California's previous droughts. For example, the state's last major dry spell occurred in the early 1990s and was characterized by below-average amounts of rain and snowfall for several years.

"That's what we typically think of when we think of drought – a few years when precipitation is below normal. We don't conceptualize that the precipitation would just shut off," Swain said. "That's what's so remarkable about this drought. It's not a multi-year drought that's getting progressively worse as the years go by. It's that it has barely rained at all this year. That's a much more acute situation in a lot of ways."

Source: US Drought Monitor
(Click image to enlarge it.)

Three times more likely now than before industrialisation

Daniel Swain coined the term "Ridiculously Resilient Ridge" or Triple R, to describe the large region of high atmospheric pressure that's preventing rains from getting to California and is causing the current drought. Results from their work have recently been published in a special supplement to this month's issue of the Bulletin of the American Meteorological Society (BAMS). It turns out that the conditions causing the current drought are three times more likely to occur with global warming than without.