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Was Hurricane Sandy caused by climate change?


22/11/2012

Image courtesy of NASA Goddard Institute for Space Studies

While the aftermath of Hurricane Sandy is devastating, there is a silver lining: the world is beginning to realize that climate change not only exists, but requires urgent, drastic action to prevent future destruction.

Recent studies are showing that Americans, who are notoriously slow to accept climate change science, are changing their attitudes because of Hurricane Sandy. For example, according to a November 15, 2012 article on Mother Nature Network, a study commissioned by Climate Nexus and conducted by Penn Schoen Berland shows that that 60% of Americans agree that Hurricane Sandy was worsened by global warming. Seventy-three percent of respondents agreed that global warming is affecting extreme weather events.

More scientists are starting to drop the caveat of other variables and link climate change directly to intense storms and other extreme weather events, such as the warm 2012 winter in the eastern U.S. and the frigid one in Europe at the same time. They are emboldened because researchers have become more apt in the past decade at determining what affects the variables that create big storms. Hurricane Sandy increased considerably because it wandered north along the U.S. coast, where ocean water is still warm this time of year, pumping energy into the swirling system. But it got even larger when a cold Jet Stream made a sharp dip southward from Canada down into the eastern U.S. The cold air, positioned against warm Atlantic air, added energy to the atmosphere and therefore to Sandy, just as it moved into that region, expanding the storm even further.

The atmospheric pattern that sent the Jet Stream south is colloquially known as a “blocking high”—a big pressure centre stuck over the very northern Atlantic Ocean and southern Arctic Ocean which was caused by a climate phenomenon called the North Atlantic Oscillation (NAO)—essentially, the state of atmospheric pressure in that region. This state can be positive or negative, and it had changed from positive to negative two weeks before Sandy arrived.

Recent research by Charles Greene at Cornell University and other climate scientists has shown that as more Arctic sea ice melts in the summer—because of global warming—the NAO is more likely  to be negative during the autumn and winter. A negative NAO makes the Jet Stream more likely to move in a big, wavy pattern across the U.S., Canada and the Atlantic, causing the kind of big southward dip that occurred during Sandy.

Climate change amps up other basic factors that contribute to big storms. For example, the oceans have warmed, providing more energy for storms. And the Earth’s atmosphere has warmed, so it retains more moisture, which is drawn into storms and is then dumped on us.

These changes contribute to all sorts of extreme weather. In a recent op-ed in the Washington Post, James Hansen at NASA’s Goddard Institute for Space Studies in New York blamed climate change for excessive drought, based on six decades of measurements, not computer models: “Our analysis shows that it is no longer enough to say that global warming will increase the likelihood of extreme weather and to repeat the caveat that no individual weather event can be directly linked to climate change. To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change.

While the public is slowly but surely warming to the idea of climate change, global leaders have seized Sandy’s aftermath as an opportunity to take serious action. The Independent reported that an alliance of 200 international financial institutions, including HSBC and Scottish Widows, have called the world’s largest economic powers, including the U.S., U.K., and China, to increase their efforts to combat climate change. Considering that the 200 groups control $21 trillion worldwide, their call for a “clear, consistent and predictable policies that encourage low carbon investment” is very powerful.

Chris Davis, a member of the alliance, said, “Hurricane Sandy, which caused more than $50bn in economic losses, is typical of what we can expect if no action is taken and warming trends continue”.

Information courtesy of Scientific American and Green-Buildings.com  

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