Megadroughts due to global warming
Published in the journal Science Advance on Thursday, the study predicts that should things continue as usual, California, the Midwest and the Southwest will have very little precipitation and “Dust Bowl” conditions will prevail by as early as 2050. An extended drought of a kind not previously seen in the region for more than 1,000 years will be the result.
Lead author Ben Cook, a climate scientist at NASA’s Goddard Institute for Space Studies and at the Lamont-Doherty Earth Observatory at Columbia University, said that the real kicker is that any droughts created by human-produced greenhouse gas emissions could last a long time.
“Natural droughts like the 1930s Dust Bowl and the current drought in the Southwest have historically lasted maybe a decade or a little less,” said Ben Cook. “What these results are saying is we’re going to get a drought similar to those events, but it is probably going to last at least 30 to 35 years.”
If greenhouse gas emissions continue without impediment, the chances of a megadrought in the region are as high as 80 percent. Smith said they looked at several indicators over a long period rather than, as other studies have done, looking only at droughts occurring in the past 100 or so years.
“We can’t really understand the full variability and the full dynamics of drought over western North America by focusing only on the last century or so,” Cook said.
“We have to go to the paleoclimate record (to view) much longer timescales when much more extreme and extensive drought events happened, to really come up with an appreciation for the full potential drought dynamics in the system.”
High carbon dioxide concentrations
A NASA press release said “the scientists analyzed a drought severity index and two soil moisture data sets from 17 climate models” run from both a model of green house gas emissions being reduced and one of green house gas emissions continuing unchecked.
“The high emissions scenario projects the equivalent of an atmospheric carbon dioxide concentration of 1,370 parts per million (ppm) by 2100,” the press release said. “While the moderate emissions scenario projects the equivalent of 650 ppm by 2100. Currently, the atmosphere contains 400 ppm of CO2.”
Either way, unless the complete elimination of human-produced greenhouse gas emissions occurs, and soon, weather in California, the American Midwest and Southwest will be changing dramatically.
“Nearly every year is going to be dry toward the end of the 21st century compared to what we think of as normal conditions now,” Cook said. “We’re going to have to think about a much drier future in western North America.”
