For more than two years, a devastating drought has gripped a huge swath of the U.S.—drying up groundwater, killing crops and choking shipping lanes. One part of that drought, dubbed the “2012 Great Plains Drought” for its effect on middle America, says Climate Central, was worse than the Dust Bowl droughts of the 1930s. For many places, the drought is far from over.
With high temperatures and low rain taking a staggering economic toll—with billions of dollars in losses—a federal task force set out to figure out what caused the drought and to sort out if we should have seen it coming.
It seems that every time horrible weather hits, people turn and ask, “Is this climate change?” Typically, the answer you’ll get goes something like this: climate change is defined as a long-term statistical change in the weather, and so you can’t say that is any one disaster is “because of climate change.” That response is about as common as it is outdated.
In the past few years, a new concept has entered the discussion among climate scientists. Spear-headed in large part by the work of English scientist Peter Stott, the field of “event attribution” uses climate models to try to say how much we can attribute a natural disaster to global climate change. The famine-inducing drought that struck East Africa two years ago, a plight that lead to the deaths of hundreds of thousands of people, for instance, has been attributed to climate change: higher sea temperatures made the spring rains fail, driving the drought.
There’s never an all-or-nothing relationship between climate change and a particular extreme event. But what event attribution allows us to say is how much more likely a particular weather event was or how much stronger it ended up being because of shifts caused by climate change.
According to the Associated Press, the federal task force’s investigation says that the U.S. drought couldn’t be predicted by climate models and that the drought wasn’t due to climate change.
“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.”
“There was a change in the large-scale, slowly evolving climate that made drought severity more likely” in the past decade or so, Hoerling said” to Climate Central, “but nothing that pointed to a severe drought in 2012 specifically.”
The report may leave more open questions than answers, given that it found that no known source of natural climate variability can shoulder most of the blame for the drought, nor can man-made global warming, which over the long run is projected to make droughts more likely in some parts of the U.S., particularly the Southwest.
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