Last year's huge drought was a freak of nature that wasn't caused by man-made global warming, a new federal science study finds.
Scientists say the lack of moisture usually pushed up from the Gulf of Mexico was the main reason for the drought in the nation's midsection.
Thursday's report by dozens of scientists from five different federal agencies looked into why forecasters didn't see the drought coming. The researchers concluded that it was so unusual and unpredictable that it couldn't have been forecast.
"This is one of those events that comes along once every couple hundreds of years," said lead author Martin Hoerling, a research meteorologist at the National Oceanic and Atmospheric Administration. "Climate change was not a significant part, if any, of the event."
Researchers focused on six states - Wyoming, Kansas, Nebraska, Colorado, Missouri and Iowa - but the drought spread much farther and eventually included nearly two-thirds of the Lower 48 states. For the six states, the drought was the worst four-month period for lack of rainfall since records started being kept in 1895, Hoerling said.
He said the jet stream that draws moisture north from the Gulf was stuck unusually north in Canada.
Other scientists have linked recent changes in the jet stream to shrinking Arctic sea ice, but Hoerling and study co-author Richard Seager of Columbia University said those global warming connections are not valid.
Hoerling used computer simulations to see if he could replicate the drought using man-made global warming conditions. He couldn't. So that means it was a random event, he said.
The study was titled, "An Interpretation of the Origins of the 2012 Central Great Plains Drought," but when it comes to climate, you can be sure that there are always other conflicting "interpretations." The folks over at the left-leaning ThinkProgress blog cite a furious push back against the conclusion of the NOAA study by National Center for Atmospheric Research climatologist Kevin Trenberth. Among other criticisms, Trenberth notes:
In the experiments performed with climate models, no indication is given that the model used or the forecast results from several other models, have any skill or utility at the task set them. The distinctive La Niña pattern in 2011 giving extremes of dryness in Texas and wetness further north was not simulated or predicted either! In the lower 48, it has been distinctly wetter after about the 1970s in all seasons other than winter, but none of the models simulate this. Not one! The model biases are not dealt with and their skill, or lack of it, is not given. They are not shown to be appropriate to the task at hand. There is a complete failure to provide any reasons to believe the results. Moreover the experiments are woefully incomplete. SSTs [sea surface temperatures] were specified but no attempt was made to include soil moisture, snow cover anomalies, or vegetation health, for instance.
Models, models everywhere, and not a drop to drink (at least not in Texas).