ORIGINAL: Climate Central
July 19th, 2012
For U.S. farmers and ranchers facing economic peril due to the blistering heat and drought this summer, the latest drought data released Thursday offered no reasons for optimism. The drought that has already prompted the largest natural disaster declaration in the history of the U.S. Department of Agriculture has grown worse in terms of both extent and intensity during the past week. Not only that, but new climate outlooks for the next three months show above-average chances for a hot and dry remainder of the summer in the Midwest and Central States.
“We don’t have a reason to say that it’s about to improve,” said Kelly Helm Smith of the National Drought Mitigation Center in Nebraska.
According to the July 19 edition of the U.S. Drought Monitor, a whopping 81 percent of the lower 48 states were experiencing “abnormally dry” to “exceptional drought” conditions, and about 64 percent of the contiguous U.S. was experiencing moderate to exceptional drought conditions, a record high for the 12-year history of Drought Monitor data. Data that stretches further back in time shows that the current drought is one of the top 10 most severe droughts in U.S. history in terms of extent and intensity, although it has not lasted as long as other major droughts, including the Dust Bowl droughts of the 1930s.
"We continue to see drought spreading and intensifying," said Brian Fuchs, climatologist and Drought Monitor author at the National Drought Mitigation Center said in a press release. "Even though we've made improvements in places like Texas where they've had rain, drought has expanded in other areas, like eastern Iowa."
The drought prompted the U.S. Department of Agriculture to expand its natural disaster declaration on July 18 to direct federal aid to more farmers who are already suffering economic losses from this event. The USDA cut its estimate for the U.S. corn crop by 12 percent, and noted that food prices have already begun to increase.
Last week the drought prompted the USDA to issue the largest natural disaster declaration in the agency’s history, covering more than 1,300 counties in 29 states.
In many parts of the drought region, the parched conditions came on suddenly — a phenomenon known as a “flash drought.” Key factors behind this event include a back-to-back La Niña event in the tropical Pacific Ocean, which has only recently begun to subside in the ocean and the atmosphere. La Niña events, which are characterized by cooler-than-average sea surface temperatures in the tropical Pacific Ocean, are known to favor dry conditions in parts of North America.
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| Temperature outlook for August 2012, showing above average chances for warmer than average conditions across much of the country. Credit: NOAA/CPC. |
In addition, last winter was milder than average with scant snowfall, which may have helped dry soils faster during the spring and early summer. In addition, there were several record heat waves during March, June and July. The U.S. experienced its warmest January-to-June period on record, and during June more than 170 all-time temperature records were broken, according to the National Oceanic and Atmospheric Administration (NOAA).
Droughts are expected to become more frequent and severe as the climate continues to warm in response to man made emissions of greenhouse gases. In fact, large-scale drying trends have already been observed and linked to global warming since the 1970s, but the role warming is playing in this particular drought has not yet been studied. One possibility is that the background warming that has taken place during the past several decades is serving to intensify both the heat extremes and the drought itself.
“I think what we’re seeing is largely a naturally occurring event, but it’s occurring against the background of a warming environment,” said Richard Seager, a professor who specializes in drought at Columbia University’s Lamont-Doherty Earth Observatory.
During a conference call with reporters on Thursday, NOAA scientists said the extremely dry conditions in the Midwest will favor more heat extremes and less rainfall during August, which will only exacerbate the drought conditions. Such feedbacks between drought and air temperatures can help make a severe drought extremely difficult to break out of. This is the reason behind a common saying among meteorologists: "drought begets drought."
