Journalists and bloggers tend to prefer the cautious route in explaining these natural disasters (perhaps partially due to our atmosphere of intense climate science denial) and remind us that weather and climate are not the same, therefore, as they correctly espouse, the link between Hurricane Sandy and climate change is rather complex. However, the link is still there and the short and correct answer to the aforementioned question is yes - absolutely.
Hurricane Sandy got large 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.
Here’s where climate change comes in. The atmospheric pattern that sent the Jet Stream south is colloquially known as a “blocking high”—a big pressure center stuck over the very northern Atlantic Ocean and southern Arctic Ocean. And what led to that? 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. The climate kicker? 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.”
He went on to write that the Russian heat wave of 2010 and catastrophic droughts in Texas and Oklahoma in 2011 could each be attributed to climate change, concluding that “The odds that natural variability created these extremes are minuscule, vanishingly small. To count on those odds would be like quitting your job and playing the lottery every morning to pay the bills.”
Hanson also argued a year ago that Earth is entering a period of rapid climate change, so radical weather will be upon us sooner than we’d like. Scientific American just published a big feature article detailing the same point.