Hurricanes Irene and Before

Now that Hurricane Irene has hit New York city as only a tropical storm (not to minimize the great damage such a storm can do -- it landed in North Carolina and then New Jersey as a legitimate (Cat 1) hurricane), I wonder if Bill McKibben will rethink his recent column that blamed global warming for Hurricane Irene. Remember, it's hardly unprecedented for a major hurricane to hit that area -- this is from Wikipedia:

• "The Great September Gale of 1815 (the term hurricane was not yet common in the American vernacular), which hit New York City directly as a Category 3 hurricane, caused extensive damage and created an inlet that separated the Long Island resort towns of the Rockaways and Long Beach into two separate barrier islands.

• "The 1821 Norfolk and Long Island Hurricane, a Category 4 storm which made four separate landfalls in Virginia, New Jersey, New York and southern New England. The storm created the highest recorded storm surge in Manhattan of nearly 13 feet and severely impacted the farming regions of Long Island and southern New England.

• "The 1869 Saxby Gale affected areas in Northern New England, decimating the Maine coastline and the Canadian Outer Banks. It was the last major hurricane to affect New England until the 1938 storm.

• "The 1893 New York hurricane, a Category 2 storm, directly hit the city itself, causing a great storm surge that pummeled the coastline, completely removing the Long Island resort town of Hog Island."

• The Great Hurricane of 1938, which made landfall as a Category 3 hurricane and killed upwards of 800 people with $41 billion (2011 dollars) in damage.

Again, I'm not minimizing this hurricane, which as I write this has killed 22 people (16 in the U.S.) with $7 B in damage. But, storms happen.

PS: Thanks to commenter Steve Bloom for mentioning Kerry Emanuel's Power Dissipation Index as an alternative to Accumulated Cyclone Energy. (Also see Steve's comment here.) PDI essentially adds up the cube of a storm's velocity, while ACE adds up the square. Emanuel has a reason for this (details here), which I'm still trying to understand. It's not intuitively obvious to me that that's a better measure; it does, though, track sea surface temperatures:

This graph is from Emanuel's 2007 paper in Journal of Climate.