Hurricane Sandy has ripped away any lasting doubt among scientists that climate change is causing an increasing number of natural disasters. Scientific American explains that Sandy got so large because the cold jet stream dropped down into the storm system and pushed more energy into her.
But there’s climate change, without a doubt, also played a big role:
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.
But that’s not all — warmer oceans also undoubtedly contribute by giving more energy to storms. The earth’s atmosphere is warmer too, meaning it holds in more moisture which is drawn into storms then poured out onto us when the storm hits.
James Hansen affirmed the link very strongly in a recent op-ed:
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.
So there you have it. If you had any doubt who was to blame for Sandy — and big storms past and those to come — you can put that to rest now. [Scientific American]