Think Progress : By taking no serious action to slash carbon pollution and put the world on a path to 2°C warming (or less), humanity is voluntarily choosing to sharply boost the chances of the worst kinds of droughts — including the kind of multi-decade megadroughts that in the past have overturned entire civilizations.  

In a new study, researchers from Cornell, University of Arizona and U.S. Geological Survey conclude that “the risk of a decade-scale megadrought in the coming century [in the SW] is at least 80 percent, and may be higher than 90 percent in certain areas.”  

“The authors note that because of some simplifying assumptions that they made, ‘the view of risk presented here is quite conservative.’”