Researchers from the National Aeronautics and Space Administration (NASA) published the first empirical analysis that connects global warming to recent high summer temperatures observed in 2010 and 2011 in the journal Proceedings of the National Academy of Sciences on August 6, 2012.
The key to the reliability of the interpretation lies in the fact that surface temperature data from June, July, and August in 2010 and 2011 were compared to the same data for a base period of 1951 to 1980.
The researchers also compared the number of high temperature anomalies like the heat waves in Texas and Oklahoma that have produced recent record breaking droughts to the number of similar anomalies occurring in the base period.
“Their findings revealed that extremely hot summers -- those with temperatures 3 standard deviations greater than the mean temperature in the base period -- occurred much more frequently in the past several years than during the base period, when they were practically absent.†Three standard deviations means a 97 to 99 percent chance of correlation depending on the method used.
The fact that ten percent of the Earth’s surface has experienced extreme surface temperatures in 2010 and 2012 compared to one percent in 1951 to 1980 adds sufficient weight to the argument.
Recent high summer temperatures have been the result of global warming.
Paper
Authors
James Hansen A,1 , Makiko Sato A , and Reto Ruedy B
A National Aeronautics and Space Administration Goddard Institute for Space Studies and Columbia University Earth Institute, New York, NY 10025; and b Trinnovim Limited Liability Company, New York, NY 10025
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