There has been much discussion about what caused the 2012 drought in the USA. The drought has now eased somewhat but it was the most severe drought since measurements began in 1895, even worse than the the driest summers that occurred during the Dust Bowl years. By early September 2012 more than 75% of the contiguous USA was experiencing abnormally dry conditions and 50% including the Central Plains was undergoing severe drought.
A report from the NOAA Drought Task Force and compiled by 19 atmospheric scientists suggested that global warming did not play a significant part in the drought, but it has been difficult to find a direct cause for the lack of precipitation. There are plenty of theories about indirect causes, ranging from disrupted weather systems due to melting ice in the Arctic Ocean, reduced snowpack in the mountains and consequently reduced river flows into the Great Plains, plus an increased risk of heatwaves which dry out the soil and are due to higher temperatures.
Kevin Trenberth who is a climate scientist with the National Center for Atmospheric Research (NCAR) commented on the report saying that the report ?has?some useful material in it . . . But it is quite incomplete in many respects, and it asks the wrong questions. Then it does not provide very useful answers to the questions that are asked.??
Other scientists point to the possibility of several different causes for the drought, which when considered alongside natural variations make it nearly impossible to tease out specific causes.
Image courtesy of NOAA
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