Specifically attributing a particular weather event to climate change has been difficult – as one famous analogy goes, it’s like determining which of Mark McGwire’s home runs were because of steroids and which weren’t. But climate attribution science is slowly becoming more accurate and accepted. In “Explaining Extreme Events of 2011 From a Climate Perspective,” a new study appearing in July’s Bulletin of the American Meteorological Society, editors Thomas C. Peterson, Peter A. Stott, and Stephanie Herring provide a review of six extreme weather events from last year and offer “some illustrations of a range of possible methodological approaches” to the process of attribution. Among their conclusions, the editors note that, due to climate change, the extreme heat and drought that suffocated Texas in 2011 was 20 times more likely to occur than 40 years earlier. However, the devastating floods that swept across Thailand last year are blamed on a number of other non-climatic factors.

Further evidence in support of climate attribution appeared in the August 6 edition of the Proceedings of the National Academy of Sciences. “Perceptions of Climate Change,” written by James Hansen, Makiko Sato, and Reto Ruedy, asserts that temperature anomalies, particularly those that deviate from expected weather patterns by three or more standard deviations on a conventional Gaussian distribution, have increased markedly in the years since the study’s base period of 1951 to 1980. The authors thus conclude, with a “high degree of confidence,” that events such as the 2011 Texas drought and 2010 heat wave and accompanying wildfires that decimated Russian agriculture were indeed precipitated, or at least exacerbated, by climate change, “because their likelihood in the absence of global warming [is] exceedingly small.” However, the article’s methodology has been questioned by some scientists, who feel that the paper’s bold conclusions are not adequately supported by the evidence it presents.

Sources: Climate Central, The New York Times.