The U.S. is facing the worst drought in 1,000 years, “driven primarily” by man-made climate change.
By the end of this century, researchers are predicting years-long dry spells exacerbated by higher temperatures, creating conditions worse than so-called megadroughts that have been linked to the decline of American Indian cultures in the U.S. Southwest, according to an article published Thursday in the journal Science Advances.
The conclusion is further evidence that human activity is having profound, harmful and long-lasting impacts on the planet, and will continue to threaten the environment even if carbon emissions are significantly curtailed.
“The bad news is, these past megadroughts -- and we don’t use ‘mega-’ lightly -- when we compare the characteristics of those to the projections from future models, the future’s worse,” said Jason Smerdon, a climate scientist at Columbia University in New York and one of the authors of the report.
If carbon emissions don’t start declining by 2050, the risk of a decade-long drought in the Southwest and Central Plains doubles in the second half of the century, the researchers found. The study looked at historical tree-ring patterns to evaluate past environmental conditions, combined with climate models to predict the future impact of rising temperature.
Hot and Dry
“What we really did in this paper was stitch the past together with the future model projections and say, ’OK, we know this warming is happening, we know it’s been dry in the past, how do those two things compare?’” Smerdon said in an interview.
Even if emissions begin tapering by mid-century, the risk of drought will remain higher than previously thought because the climate will continue to get warmer.
Past megadroughts ravaged food supplies and may have contributed to Indian tribes in the Southwest migrating or dying off.
California’s drought is entering its fourth year, with snowpack levels about one-quarter of historical averages. San Francisco went without rain in January for the first time in 165 years. The drought is affecting more than 64 million people in the Southwest and Southern Plains, according to NASA data cited in the study.
Droughts toward the end of this century are unlikely to force mass migrations, but food shortages and escalating energy prices are legitimate concerns, said Amir AghaKouchak, a civil and environmental engineering professor at the University of California at Irvine. Rising temperatures already are a significant risk to humans without adding in reduced rainfall, he said.
“Even if droughts don’t increase, because of this increase in temperature you have more and more concurrent extremes,” he said in an interview. “If you have two extremes happening at the same time, you’ll have this compound impact. It makes a big, big difference.”