Climate Change Could Push Risk of ‘Megadrought’ to 99% in American Southwest

A megadrought spanning several decades could be almost certain to hit the American southwest this century if greenhouse gas emissions are not curbed, a new study says.

Rising temperatures will “load the dice” in favor of a megadrought in the region, the researchers say. Combined with a decline in rainfall, warming conditions could put risk levels at 99% for much of the region, the study finds, while moderate increases in rainfall would still leave risk levels above 70%.

But there is a “glimmer of hope” another scientist tells Carbon Brief.  The study also shows that keeping global temperature rise to no more than 2C above pre-industrial levels would cut this risk by half.

Megadrought
In the last few days, state officials have confirmed that California’s drought has now ticked over into its sixth year. The costs of the ongoing dry spell have run into billions through lost crops and livestock, and the energy demands of pumping water from ever-retreating groundwater stores. Today, more than 60% of the state remains in “severe” drought or worse.

Now a new study, published in Science Advances, says unchecked climate change is upping the risk that California and the wider American southwest could see droughts in future that persist a lot longer.

The study looks specifically at “megadroughts”.  These are 35-year periods that are at least as dry, on average, as the worst droughts experienced in the 20th century – such as the “Dust Bowl” droughts of midwest America in the 1930s.

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