As a scientist in a field where consensus is constantly challenged, I'm a bit sensitive about being pitted against a colleague. Case in point, a recent USA Today article, which includes the following quotes:

“Mostly, it’s a natural thing,” climate scientist Gerald North of Texas A&M called the storm in an interview with the Associated Press. Others, such as Texas Tech climate scientist Katharine Hayhoe, noted that warmer Atlantic waters and Arctic weather that helped steer the storm were juiced by global warming and played a significant role.

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Here's the funny thing: I actually agree with Gerry (a well-respected colleague and one who is just as concerned about the potential impacts of climate change as I am). Yup, I do. What do I mean by that?

First, large hurricanes in October are not at all unusual. About one of them hits the US every 5 years. This time, it was Sandy.

So did climate change cause Sandy? No: there is absolutely no evidence that it did. In fact, several future modeling studies suggest climate change may actually *decrease* hurricane frequency (although increasing the number of Cat 4 and 5 storms).

Second, while climate change more than likely exacerbated the impacts of the storm, the influence of climate change on sea level and ocean temperature is clearly *less than* natural variability at this time.

I estimated earlier (see previous twitter feed for references) that long-term 7 inch global sea level rise could have enhanced Sandy's storm surge by 4% and sea surface temperature increases by something on the order of 1oC. Compare that to the 14 foot storm surge measured during the storm, and the >5oC natural SST temperature anomaly present this month.

So Gerry's quote is entire consistent with both my and other mainline scientific understanding of this issue: the data does suggest most of Sandy was natural. But I would bet that Gerry would also agree with me, that it's not likely that the impact of climate change on Sandy was zero.

For now, though, we have absolutely no way to quantify or put a number on the impact of climate change on Sandy. We do know it wasn't zero, and we do know it wasn't 100% and probably not even 50% (which would qualify as "most").

Now, in between 0 and 100% is a big range and you can bet that many scientists will be working on narrowing down that gap in the next few years. Stay tuned to the glacial pace of scientific journals over the next three years to find out more :)

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