Global warming didn’t cause the historic drought that covered nearly two-thirds of the country last year, a new study by scientists from several federal agencies found.
Instead, the drought was caused by “natural variations in weather,” the study concluded.“Neither ocean states nor human-induced climate change, factors that can provide long-lead predictability, appeared to play significant roles in causing severe rainfall deficits over the major corn producing regions of central Great Plains,” wrote lead author Martin Hoerling, a research meteorologist at the National Oceanic and Atmospheric Administration. The unpredictably dry summer was caused by a lack of moisture from the Gulf of Mexico, which usually carries water vapor north to the Central Plains states, the researchers said. Because the jet stream that pushes up the moisture was stuck in Canada, it failed to bring the spring rain and summer storms that water the middle of the country. But when the scientists tried to reproduce the drought with a computer simulation using global warming conditions, they couldn’t. “This is one of those events that comes along once every couple hundreds of years,” Hoerling told the Associated Press. “Climate change was not a significant part, if any, of the event.” The report may disappoint climate activists who have blamed the report on man-made global warming. Climate change bore the blame for the drought at the confirmation hearing for Gina McCarthy, President Obama’s nominee to head the Environmental Protection Agency. Sen. Bernie Sanders, D-Vt., blamed the drought, a wave of severe storms, and wildfires on global warming, and called climate change one of the most serious crises the world faces. Scientists have also been quick to point to global warming. “This is what global warming looks like at the regional or personal level,” Jonathan Overpeck, professor of geosciences and atmospheric sciences at the University of Arizona, told AP last July. “The extra heat increases the odds of worse heat waves, droughts, storms and wildfire. This is certainly what I and many other climate scientists have been warning about.” Another scientist told the Associated Press Thursday’s report didn’t take all the possible effects of global warming into account.Kevin Trenberth, climate analysis chief at the federally-funded National Center for Atmospheric Research, said the report failed to account for the lack of snowfall in the Rockies the previous winter or how global warming exacerbated the high pressure system that kept the jet stream stuck in Canada, he said.
“This was natural variability exacerbated by global warming,” Trenberth said. “That is true of all such events from the Russian heat wave of 2010, to the drought and heat waves in Australia.”