A new joint study from the University of Arizona, Cornell University, and the U.S. Geological Survey predicts that the chances of a Southwestern “megadrought”– a drought that lasts for 35 years — are now anywhere between 20 and 50 percent.
The study also estimates the chances of a decade-long drought in the Southwest to be “at least 80%”
California is in the midst of one of the worst droughts in state history; scientists estimate that 63 trillion gallons of water have been lost over the past 18 months. According to the U.S. Drought Monitor, 58.4% of the state is in “exceptional” drought, the most severe level possible.
Toby Ault, the study’s lead author and a professor of earth and atmospheric sciences at Cornell University, attributes the increased chances of a “megadrought” to climate change.
“For the southwestern U.S., I’m not optimistic about avoiding real megadroughts,” Ault told the Cornell Chronicle. “As we add greenhouse gases into the atmosphere — and we haven’t put the brakes on stopping this — we are weighing the dice for megadrought.”
However, Ault contradicts himself and points out in the San Jose Mercury News that prolonged droughts have occurred throughout history, even well before the advent of carbon emissions. In fact, megadroughts are thought to occur every 400 to 600 years. Ault said in the report that due to increased greenhouse gas emissions, “the drought models — and their underlying statistics — are now in a state of flux.”
The study used “state-of-the-art climate model projections” and observational information to determine the chances of prolonged drought in the future. Yet the study’s own summary points out that these models do not take key information, like hydroclimate variablity, into consideration when building projections.
“State-of-the-art global climate models do not capture this characteristic of hydroclimate variability, suggesting that the models underestimate the risk of future persistent droughts,” the report says.