Megadroughts to plague the Southwest as climate warms, study says
Excerpt from this USA Today story:
Megadroughts – defined as intense droughts that last for decades or longer – once plagued the Desert Southwest. In fact, from the 9th to the 15th centuries, at least a dozen medieval megadroughts occurred across the region, scientists said.
Now, a study suggests that because of the drying influence of climate change, megadroughts could return to the region.
Megadroughts are defined more by their duration than their severity. They are extreme dry spells that can last for a decade or longer, according to the National Oceanic and Atmospheric Administration.
They’ve parched the West, including present-day California, long before Europeans settled the region in the 1800s.
How do scientists know how wet or dry it was centuries ago? Though no weather records exist before the late 1800s, scientists can examine paleoclimatic “proxy data,” such as tree rings and lake sediment, to find out how much – or little – rain fell hundreds or even thousands of years ago.
If scientists can understand why megadroughts happened in the past, it can help better predict whether, how and where they might happen in the future, the new study said.
“In our paper, we present the first comprehensive theory for what caused historical megadroughts, which happened during the medieval period but not after about the year 1600,” said study lead author Nathan Stieger of Columbia University’s Lamont-Doherty Earth Observatory. “We find that they were caused by severe and frequent La Niñas, a warm Atlantic Ocean, and a net increase in energy from the sun.”
The study also suggests an increasing risk of future megadroughts in the American Southwest because of climate change.
Megadroughts to plague the Southwest as climate warms, study says