Heatwaves ‘caused by climate change’
HUMAN-DRIVEN climate change is to blame for a series of increasingly hot summers and the situation is already worse than was expected just two decades ago, says a top NASA scientist.
James Hansen, who directs the NASA Goddard Institute for Space Studies, wrote in the Washington Post on Saturday, August 4, that even his “grim” predictions of a warming future, delivered before the United States Senate in 1988, were too weak.
“I have a confession to make: I was too optimistic,” Dr Hansen writes.
“My projections about increasing global temperature have been proved true.
“But I failed to fully explore how quickly that average rise would drive an increase in extreme weather.”
Dr Hansen and his colleagues have published in the Proceedings of the National Academy of Sciences an analysis of the past six decades of global temperatures, revealing a “stunning increase in the frequency of extremely hot summers,” he writes.
Describing “deeply troubling ramifications for not only our future but also for our present”, Dr Hansen says the analysis is based not on models or predictions, “but actual observations of weather events and temperatures that have happened”.
The peer-reviewed study shows global temperature has been steadily rising because of a warming climate, about 0.8C in the past century, and that extreme events are more frequent.
The study echoes the findings of international research released last month that climbing greenhouse gas emissions boosted the odds of severe droughts, floods and heatwaves in 2011.
Dr Hansen says the European heatwave of 2003, the Russian heatwave of 2010 and massive droughts in Texas and Oklahoma last year can each be attributed to climate change.
“And once the data are gathered in a few weeks’ time, it’s likely that the same will be true for the extremely hot summer the US is suffering through right now,” he says.
Another well-known US scientist and former skeptic of global warming, Richard Muller, last week made a very public turnaround, saying a close look at the data has convinced him that his beliefs were unfounded.
“Call me a converted sceptic,” writes Professor Muller, of the University of California Berkeley, in an opinion piece in the New York Times.
“I’m now going a step further: Humans are almost entirely the cause,” he writes.
Professor Hansen, too, while being a long-time proponent of humans as the main cause of global warming though pollution and fossil fuel consumption, expresses his increasing certainty that other causes cannot be blamed.
“The odds that natural variability created these extremes are minuscule, vanishingly small,” professor Muller writes.
“To count on those odds would be like quitting your job and playing the lottery every morning to pay the bills.”