A new scientific paper says that more and more of the earth is being affected by extreme heat in the summer. Prior to 1980, extreme heat covered less than 1 percent of the earth’s land surface while, in recent decades, it now covers 13 percent. The paper goes on to say that it can be stated “with a high degree of confidence, that extreme anomalies [heat waves] such as those in Texas and Oklahoma in 2011 and Moscow in 2010 were a consequence of global warming because their likelihood in the absence of global warming was exceedingly small.”
The paper, which was published online on Monday in the Proceedings of the National Academies of Sciences, not only makes a case for humans’ role in causing climate change, but also goes “beyond the established scientific consensus about the role of climate change in causing weather extremes,” says the New York Times.
In particular since 1980, scientists have noted a rise of 2.5 degrees Fahrenheit over land in the past century. At issue is whether the extreme weather events singled out in the paper can be directly and definitely attributed to human activity. The paper’s findings are based on an analysis of statistics and, for these reasons, some scientists have expressed reservations about it. The title of the paper is “Perception of climate change” and, as Martin P. Hoerling, a researcher with the National Oceanic and Atmospheric Administration whose research focuses on the causes of extreme weather says, it is “mainly about perception” and “perception is not a science.”
James E. Hansen, a prominent NASA climate scientist, is one of the paper’s authors and, as the New York Times notes, has “discomfited some of his fellow researchers, who fear that his political activities may be sowing unnecessary doubts about his scientific findings and climate science in general.” Hansen has marched, and been arrested in, protests demanding that the government pursue new policies on energy and the climate.
The new paper, Hoerling notes, “confuses drought, caused primarily by a lack of rainfall, with heat waves” but other scientists assert that there is a link between global warming and drought. On Science Blogs, Greg Laden lists a number of studies that argue for a link between recent warming and widespread drought in, notably and tragically, Africa. Using the Palmer Drought Severity Index, one study finds that there has been “widespread drying over Africa, East and South Asia, and other areas from 1950 to 2008″ and that “most of this drying is due to recent warming.” In fact, around the globe, the percentage of dry areas has “increased by about 1.74 percent (of global land area) per decade from 1950 to 2008.”
It may never be possible to directly link particular extreme weather events, like the 2011 droughts in Texas and Oklahoma. But for those of us sweating through summer days on which the mercury has risen to new records (and with the US in its worst drought since 1956), it seems something like folly not to keep pushing for lowering greenhouse gas emissions; for encouraging people to drive less and bike and walk or take public transportation (provided, of course, that public transportation is available); and for government policies promoting sustainable energy alternatives. How hot does it have to get to take serious action?
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