Worst ‘Megadrought’ in 1,000 Years in U.S. Due to Global Warming

(Bloomberg) — 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.”

To contact the reporter on this story:
Justin Doom in New York at
jdoom1@bloomberg.net

To contact the editors responsible for this story:
Reed Landberg at
landberg@bloomberg.net
Will Wade

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