Did Climate Change Cause Hurricane Sandy?

If you’ve followed the U.S. news and weather in the past 24 hours you have no doubt run across a journalist or blogger explaining why it’s difficult to say that climate change could be causing big storms like Sandy. Well, no doubt here: it is.

The hedge expressed by journalists is that many variables go into creating a big storm, so the size of Hurricane Sandy, or any specific storm, cannot be attributed to climate change. That’s true, and it’s based on good science. However, that statement does not mean that we cannot say that climate change is making storms bigger. It is doing just that—a statement also based on good science, and one that the insurance industry is embracing, by the way. (Huh? More on that in a moment.)

Scientists have long taken a similarly cautious stance, but more are starting to drop the caveat 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 gotten very good in the past decade at determining what affects the variables that create big storms. 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.