How bad is the western drought? One study says it’s the worst in 12 centuries.
There would have been a drought regardless of climate change, but scientists estimate its severity would have been only about 60% of what it currently is.
ALBUQUERQUE, N.M. — The megadrought in the American Southwest has become so severe that it’s now the driest two decades in the region in at least 1,200 years, scientists said Monday, and climate change is largely responsible.
The drought, which began in 2000 and has reduced water supplies, devastated farmers and ranchers and helped fuel wildfires across the region, had previously been considered the worst in 500 years, according to the researchers.
But exceptional conditions in the summer of 2021, when about two-thirds of the West was in extreme drought, “really pushed it over the top,” said A. Park Williams, a climate scientist at the University of California, Los Angeles, who led an analysis using tree ring data to gauge drought. As a result, 2000-21 is the driest 22-year period since A.D. 800, which is as far back as the data goes.
The analysis also showed that human-caused warming played a major role in making the current drought so extreme.
There would have been a drought regardless of climate change, Williams said. “But its severity would have been only about 60% of what it was,” he said.
Julie Cole, a climate scientist at the University of Michigan who was not involved in the research, said that while the findings were not surprising, “the study just makes clear how unusual the current conditions are.”
Cole said the study also confirms the role of temperature, more than precipitation, in driving exceptional droughts. Precipitation amounts can go up and down over time and can vary regionally, she said. But as human activities continue to pump greenhouse gases into the atmosphere, temperatures are more generally rising.
As they do “the air is basically more capable of pulling the water out of the soil, out of vegetation, out of crops, out of forests,” Cole said. “And it makes for drought conditions to be much more extreme.”
Although there is no uniform definition, a megadrought is generally considered to be one that is both severe and long, on the order of several decades. But even in a megadrought there can be periods when wet conditions prevail. It’s just that there are not enough consecutive wet years to end the drought.
This article originally appeared in The New York Times.
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