How Much Climate Change Was In Hurricane Sandy?

Jet stream winds on October 29, 2012, when Hurricane Sandy was still approaching New Jersey. The wind direction over New Jersey (black arrows) was from the southeast due to a trough of low pressure over the Eastern U.S.m which, in turn, was caused by a strong blocking ridge of high pressure over Greenland. Image credit: NOAA/ESRL.

There is a lot of loosey-goosey talk (e.g., this NYT piece) about the connection between Hurricane Sandy and climate change. So here are some more assertive facts, with no hedging:

Did climate change cause Hurricane Sandy? Absolutely not. Did climate change have anything to do with Sandy being as bad as it was? Absolutely so, say scientist bloggers whose bread and butter is understanding the physics of our atmosphere. What's more, there is very likely a connection with the storm track of Sandy and the record loss of Arctic Sea ice this year.

Meteorologist Dan Satterfield makes the following points in his most recent post:

1. Oceans are over a degree Celsius warmer than a century ago (and rising) and the planet is a degree Celsius warmer than a century ago (and rising), so the atmosphere is holding 5-7 percent more water vapor (and that's rising too).

2. There have been record warm waters, 2-3 degrees Celsius above normal, off the East Coast of North America for the last few months months.

3. Sea level rise and sinking coastlines in Delaware and Virginia mean the water level is more than 18 inches higher than 60 years ago. "Ask someone in Jersey who has a foot of water in their house if it would have been better if the water was 18 inches lower," wrote Satterfield.

4. Put the three previous points together and you can reason that if a twin of Sandy were to have occurred October of 1912, it would have been less wet and had a lower storm surge. Likewise, a twin of Sandy in the year 2100 will be much wetter, with water levels from 24 to 48 inches higher.

5. But that's not all. Here's the Arctic ice part: A huge, rare late October high pressure area over Greenland caused Sandy to take a hard left turn towards the coast. "The track of Sandy was very RARE," wrote Satterfield. "Nearly unheard of actually, especially for this time of year."

6. That Greenland high pressure block could very well be connected to the record melt of Arctic sea ice this year, according to Weather Underground's Dr. Jeff Masters, Dr. Jennifer Francis of Rutgers University and Andy Revkin at Dot Earth. How does it do this? By heating up the Arctic, altering the temperature difference between the equator to the poles and forcing the jet stream to slow down and get stuck in big looping meanders, exactly what was seen over eastern North America this week.