The drought of 2012 keeps getting worse. On July 26, the federal government reported that more than two-thirds of the continental U.S. is drier than normal, with 20% of the country in one of the two most extreme stages of drought, up from just 7% a week before. In key agricultural states like Illinois, the situation is dire: nearly three-quarters of that corn-producing region’s land is in exceptional or extreme drought. Iowa, Illinois and western Indiana have had less than half the normal amount of rain over the past 30 days, and the extended dry weather has hurt production, with less than a third of U.S. corn and soybean crops in good or excellent condition as of July 22, the worst rating since 1988. The epic drought that year reduced the U.S. corn harvest by 31%. The government has already cut this year’s projected corn yield by 12%, and the crop is trading at record high prices.
The extended dry spell and the record-breaking temperatures that have gripped much of the U.S. this year have brought climate change back to the attention of the public. Some 70% of Americans now say they believe that the world is growing warmer, up from 58% two years ago. Richard Muller, a physicist at the University of California-Berkeley and a longtime climate change skeptic, took to the pages of the New York Times this week to announce that he is now convinced that global warming is real and that man-made greenhouse gas emissions are responsible for most of it. Of course, the added public attention hasn’t translated into public will to actually do something about climate change—a subject that has mostly been ignored by both presidential campaigns. But at least global warming as an issue is heating up along with the daily temperature readings, fueled in part by fears that this year’s drought could be the coming attraction for new Dust Bowls in the hotter, drier years to come.
Still, it’s far from clear exactly what role climate change may be playing in the drought of 2012. Attributing a weather event to global warming in real time is impossible, and natural phenomena like the recent La Nina, which usually produces hotter and drier weather to the southern U.S., likely play a much more immediate role than broad-scale, climate patterns. But all that means is that there are at least two engines—short-term and long-term—driving the thermometer up. And to those you can actually add a third—one writ deep in our continent’s history.
Using geochemical indicators that can reveal precipitation levels centuries or even thousands of years ago, scientists have reconstructed the meteorological past of the American West before Europeans arrived on the scene—and it’s one that was marked by massive droughts that make Dust Bowl Oklahoma in the 1930a look like Seattle on a rainy spring day. In a paper published in Nature in early 2011, researchers at the University of New Mexico analyzed massive lake sediment cores from the Valles Caldera in northern New Mexico and found that the American southwest experienced abrupt climate shifts during the warm periods of the Pleistocene Epoch, which lasted from 2.5 million years ago to 11,700 years ago. Those shifts included extended dry periods that sometimes lasted for millennia—the sort of mega-mega drought that would unimaginably change human life in the fastest growing region in the U.S. if it were to unfold today.
(MORE: When the Rains Stop)
Of course, those droughts took place well before any human beings lived in North America, so far in the past that it might be easy to imagine that nothing like that would happen during our time. But scientists like Richard Seager of Columbia University’s Lamont-Doherty Earth Observatory have used tree-ring data to find evidence that the Plains and the Southwest were struck by a series of severe droughts that went on for multiple decades between 800 A.D. and 1500 A. D. as well. How mega were these droughts? There’s evidence that there were widespread blowing sand dunes across the Great Plains during the Medieval period, creating dust storms on a level that weren’t seen again until the 1930s—though in that more recent case, the dust was due more to poor soil erosion by farmers of the period than the dry weather.
The multi-decadal droughts of the Medieval period had a devastating impact on the indigenous civilizations of the continent—especially the Anasazi people of the Southwest. Their astounding cliff cities can still be seen in settlements like Mesa Verde, but the Anasazi themselves are long gone, virtually abandoning the region by the 14th century. While scientists still don’t know why Anasazi left, a drought that stretched for decades in an already arid region may well have been more than enough.
What does the climatological past of the western U.S. tell us about the future? We don’t know for sure that the conditions that led to the massive droughts that once were will be repeated in the 21st century, but it’s notable that a new paper in Nature Geoscience argues that the lingering drought that hit the western U.S. between 2000 and 2004 was the worst since those great dryings of 800 years ago—and that what we’re experiencing now could represent a new normal for the coming century. That should be alarming. The U.S. built both the great farms of the Midwest and the new population centers of the Southwest on the idea that there was more than enough water to go around, but that clearly hasn’t always been the case. As a society we’re always failing to plan for the future, but when it comes to drought and climate, our true mistake may be the failure to learn from the past.