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U.S. Drought is Most Severe Since 1950s, Report Says

The drought that is delivering a punishing blow to corn growers, farmers, and ranchers across the Midwest and High Plains is among the most intense drought events to occur in the U.S. since the 1950s, according to a federal report released on Monday, placing it among the top 10 droughts in U.S. history.

According to the most recent drought outlook, the drought is likely to persist — if not further intensify — during the next few months.

Palmer Z drought index for June 2012, showing the extent and intensity of drought conditions across the U.S. Credit: NOAA.

On Monday, the National Climatic Data Center (NCDC) released its latest State of the Climate report on U.S. drought conditions, finding that record heat and a lack of widespread rainfall during June caused the drought to rapidly expand and intensify. 

In the Midwest, for example, areas in drought quadrupled during June, and areas in the “severe drought” category jumped from less than 2 percent at the end of May to more than 15 percent of the region at the end of June, the NCDC reported. Drought also greatly expanded across the High Plains during June as well, with the area affected by “extreme” to “exceptional” drought conditions going from just 8 percent at the end of May to 47 percent at the end of June.

Palmer Z drought index for June 1953, showing the extent and intensity of drought conditions across the U.S. at that time, which were comparable to June, 2012. Credit: NOAA.

The NCDC found that as of the end of June, the geographical extent of the drought, as well as its pattern and intensity, most closely matched the conditions present in June 1956. However, the current drought event has not lasted as long as the droughts of the 1950s.

Currently, about 71 percent of the U.S. is now considered to be in the “abnormally dry” to “exceptional” drought categories, the highest percentage in the 12-year history of the U.S. Drought Monitor. Researchers turn to other indices, such as the Palmer Drought Severity Index, which measures the balance between moisture demand and moisture supply, to compare modern drought events to historical conditions dating back more than a century.

Based on the Palmer Index, at the end of June the U.S. had the largest moderate-to-extreme drought area since the 1950s, with about 56 percent of the lower 48 states in moderate-to-extreme drought at the end of the month.

“The last time drought was this extensive was in December 1956 when about 58 percent was in moderate to extreme drought,” the NCDC said.

The nation’s corn belt is being hit especially hard by the recent hot and dry conditions, and food prices on everything from soda to beef are expected to rise in response to a corn harvest that, while a record high for the U.S., will be much below initial expectations. 

The main corn and soybean agricultural region has had its seventh warmest and 10th driest April-to-June period on record this year, the NCDC said. “Topsoil has dried out and crops, pastures, and rangeland have deteriorated at a rate rarely seen in the last 18 years, yet drought barely registers for the region on the longer-term PDSI [Palmer Drought Severity Index] because the previous several years have been very wet.”

The heat this year, particularly the record-breaking heat wave that baked a broad portion of the country from the Plains to the Mid-Atlantic during late June into early July, have played a major role in hastening the development of drought conditions. “The dryness has been accompanied by abnormally warm temperatures at all timescales,” the NCDC said. “. . . Excessive heat increases evapotranspiration and exacerbates drought.”

Palmer drought index for the corn and soybean agricultural region, dating back to 1900. This graphic shows that the current drought is one of the most severe droughts on record for this area. Credit: NOAA.

The U.S. recorded its warmest January-to-June period on record, as well as its warmest 12-month period on record. Globally, June was the fourth-warmest such month on record.

Studies have shown that manmade global warming increases the odds of heat waves and precipitation extremes, although natural variability also plays a key role in influencing regional weather and climate patterns.

There is recent scientific evidence showing that global warming may have tilted the odds in favor of one of the costliest U.S. droughts on record. A report released on July 10 found that global warming boosted the odds that the 2011 Texas drought and heat wave would occur. The drought and associated wildfires cost farmers in the state billions in agricultural losses. The study concluded that, due to manmade global warming, heat waves and drought in Texas are now 20 times more likely to occur under similar large-scale climate conditions than they were just 50 years ago. Another report released on July 10 provided evidence that the global water cycle is intensifying, which means an increased occurrence of both wet and dry climate extremes worldwide.