During the 1930s, America's High Plains were ravaged by an 8-year long drought, resulting in the dreaded Dust Bowl. Scientists now warn that, owing to global warming, this could happen again — and that by next century many parts of the world could experience "megadroughts" lasting for several decades.
The new study, which was conducted by Cornell University, the University of Arizona, and U.S. Geological Survey researchers, used climate model simulations and paleoclimate data to predict that the chances of the southwestern United States experiencing a decade-long drought is at least 50%. The analysis suggests that the risk is at least 80%, and possibly as high as 90%, in certain areas.
Frighteningly, the chances of a megadrought — one that lasts up to 35 years or more — ranges from 20% to 50% over the next century. And the risk of an unprecedented 50-year megadrought was assessed at 5% to 10%, but under the most severe warming scenarios.
Indeed, portions of the United States could already be in the early stages of a prolonged drought. As of August 12th, most of California is in the midst of an exceptional D4 drought — the most severe category.
Other areas of the U.S., including Oregon, Arizona, New Mexico, and Oklahoma, are currently experiencing a substantially less severe category D1 moderate drought. According to lead author Toby Ault, climatologists aren't sure whether the severe western and southwestern drought will continue, but "with ongoing climate change, this is a glimpse of things to come. It's a preview of our future," he noted in a Cornell statement.
Megadroughts do happen, but not very often — about every 400 to 600 years or so. Australia recently suffered a "Big Dry" period, as did sub-Saharan Africa. Back in the 1150s, a megadrought struck the Colorado River area. But these events fall within the "natural" period; owing to the advent of the anthropocene era and the cumulative influence of greenhouse gas in the atmosphere, drought models are now in a state of flux.
The models suggest that California, Arizona, and New Mexico will face severe drought conditions, while the chances for drought in parts of Washington, Montana, and Idaho are likely to decrease.
It's difficult to predict what a 35-year-long drought would look like, but it's safe to assume that it would be tremendously disruptive. It could spark a mass population migration on a scale never before seen in the United States — one that would dwarf the Dust Bowl conditions of the 1930s. It's important to note, however, that antiquated farming practices contributed (in-part) to the dust storms. But a drought that lasts for nearly 40 years — as opposed to eight — is an order of magnitude greater than what was experienced back in the 1930s.
"For the southwestern U.S., I'm not optimistic about avoiding real megadroughts," said Ault. "As we add greenhouse gases into the atmosphere – and we haven't put the brakes on stopping this – we are weighting the dice for megadrought conditions."
The researchers say that the West and Southwest must look for mitigation strategies to cope with the dreaded prospect, including better ways of using and preserving water.
"This will be worse than anything seen during the last 2,000 years and would pose unprecedented challenges to water resources in the region," he said.
Needless to say, the U.S. is not the only country at risk. The climate models suggest that southern Africa, Australia, and the Amazon basin are also vulnerable to megadroughts.
Owing to increased temperatures, drought severity will worsen, "implying that our results should be viewed as conservative," the study concludes.
Read the entire study at American Meteorological Society: "Assessing the Risk of Persistent Drought Using Climate Model Simulations and Paleoclimate Data". Additional information via Berkeley (1) (2).
Top image: kwest/shutterstock.
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