As bad as recent droughts have been in California and elsewhere in the Southwestern and Midwestern parts of the country, scientists say far worse “megadroughts” are coming — and they’re projected to last for decades.
“Unprecedented drought conditions” — the worst in more than 1,000 years — are likely to come to the Southwest and Central Plains after 2050 and stick around because of global warming, according to a new study published Thursday in the journal Science Advances.
During the years 2050 to 2100, the Southwest and Great Plains will face a persistent “megadrought” worse than anything seen in the past 1,000 years, and the dry conditions will be “driven primarily” by human-induced global warming, scientists said.
“The future of drought in western North America is likely to be worse than anybody has experienced in the history of the United States,” said Dr. Benjamin Cook, the study’s lead author and a climate scientist at NASA’s Goddard Institute for Space Studies in New York City. “These are droughts that are so far beyond our contemporary experience that they are almost impossible to even think about.”
There’s more than an 80 percent chance that much of this part of the country will have a 35-year-or-longer “megadrought” later this century if climate change continues unabated, said Dr. Cook. A megadrought is defined as a drought that lasts for decades or longer, such as those that scorched portions of the West in the 12th and 13th centuries. Dr. Cook said megadroughts should be considered a natural hazard on par with earthquakes and hurricanes.
Megadroughts will be ‘worse than anybody has experienced in the history of the United States’
The new research is based on current increasing rate of rising emissions of carbon dioxide and complex simulations run by 17 different computer models, which generally agreed on the outcome, Dr. Cook said.
The regions Dr. Cook’s team looked at include California, Nevada, Utah, Colorado, New Mexico, Arizona, northern Texas, Oklahoma, Kansas, Nebraska, South Dakota, most of Iowa, southern Minnesota, western Missouri, western Arkansas, and northwestern Louisiana.
To identify past droughts, scientists studied tree rings to find out how much — or little — rain fell hundreds or even thousands of years ago. Scientists used that historical data in combination with the computer simulations to predict what changes we may see this century.
The models showed robust and consistent drying in the Southwest and Plains, due to a combination of reduced precipitation and warmer temperatures that dried out the soils, the researchers said.
Historical data showed there were megadroughts in the Southwest and Central Plains in the 1100s and 1200s that lasted for decades, but these will be worse, said Dr. Cook. Those were natural and not caused by climate change, unlike those forecast for the future, he explained.
Scientists predict ‘bleak future’ if climate change is left unchecked
Though previous studies have predicted climate change would increase the odds of worse droughts, this study predicts an even bleaker future, showing “more convincingly than ever before that unchecked climate change will drive unprecedented drying across much of the United States—even eclipsing the huge megadroughts of medieval times,” said Jonathan Overpeck, co-director of the Institute of the Environment at the University of Arizona, who was not involved in the study.
Drought, of course, will have serious consequences, including the potential for water shortages throughout the country. According to the National Resource Defense Council’s “Climate Change, Water, and Risk” report, at least 1,100 U.S. counties – one-third of all counties in the lower 48 states – face higher risks of water shortages by mid-century as a result of climate change. More than 400 of these counties will face extremely high risks of water shortages.
As temperatures rise and precipitation decreases, water quality can also be jeopardized. Shrinking water levels can concentrate contaminants such as heavy metals, industrial chemicals and pesticides, and sediments and salts. Additionally, droughts make drinking water supplies more susceptible to harmful algal blooms and other microorganisms.
Changes in precipitation and water availability will also have serious consequences for commercial agriculture – crops yield less in dry seasons, and food security suffers. In fact, scientists have warned that the effects of climate change will threaten the global food supply unless urgent action is taken. Drought conditions can also help fuel out-of-control wildfires.
But it’s not too late to mitigate some of these effects, scientists say. “The good news is that we have ample warning and know what to do to stop the unprecedented drying from becoming reality—we just need to make serious cuts in greenhouse gas emissions,” said Dr. James Famiglietti, a researcher from the University of California, Irvine.
“Otherwise,” he warned , “the next generations of Americans are going to have a huge problem on their hands.”