Scientists Benjamin I. Cook (NASA Goddard Institute for Space Studies), Toby R. Ault (Cornell University) and Jason E. Smerdon (Columbia University’s Lamont-Doherty Earth Observatory) forecast an “unprecedented 21st century drought risk” in the Southwestern United States due to climate change. The report is published in the new peer-reviewed journal Science Advances, by the American Association for the Advancement of Science. Their methodology:
To gather evidence of past megadroughts, the scientists used thousands of tree-ring records collected over many years by other researchers, as well as the histories of ancient droughts that affected the long-puzzling history of the Anasazi people in the American Southwest.
Those people and their widespread cultures disappeared around 1300 A.D. and the cause of their disappearance has long been disputed by archaeologists. But the tree-ring records and the radiocarbon dates of their plant remains show that they did undergo centuries of alternating heat-induced droughts — climaxed by what has been called the “great drought” of 1276 to 1299 A.D.
In his discussion of the megadrought report, Caldeira recalled visiting Anasazi ruins like Mesa Verde in Arizona and said “it looks like the droughts in store for us later this century will make the droughts that did in the Mesa Verde civilization look like child’s play.”
I think the best response to this forecast comes from Ken Caldeira, a climate scientist at the Carnegie Institution for Science and Stanford University:
“When you stack these model projections against the reconstruction of past climates, the results are so sobering that they have me ready to go out for a drink.”