Hurricane Sandy—which was, technically, not a hurricane by the time it buzzed into the Jersey Shore—was a terribly destructive cyclone. But blaming it on global warming, as did Al Gore, New York Governor Andrew Cuomo, and NYC's Mayor Bloomberg, is scientifically ludicrous.
One has to be amazed at how little fact-checking the global warming alarmists do. I guess they don't want the latest storm crisis to go to waste, but they don't help their cause by mis-stating the obvious.
There's a pretty sizable scientific literature out there on hurricanes and global warming. From the "modeling" end, probably the most cited paper is a 2004 study by Tom Knutson from the government's Geophysical Fluid Dynamics Laboratory in Princeton. Although he's tweaked it a bit since then, the result remains the same. There should be a slight increase (8 per cent) in hurricane power by the end of this century. But the inter-annual variability of these storms is so great that this signal will not emerge from the noise until around 2080.
From the "real world" point of view, I published a bunch of papers in response to Tom's work in which we found, using his assumptions about the amount of oceanic warming, that there would be a similar—again 8 per cent—increase in the number of big (Category 3 or higher) storms in the same time frame. When we adjusted for the pokey rate of oceanic warming being observed, that figure dropped by half.
Chunzai Wang of the National Oceanic and Atmospheric Administration has performed a very interesting data-based analysis of Atlantic hurricane tracks showing that increasing the area of warm water results in a significant lowering of the likelihood that a storm will strike the U.S., something that should happen with continued oceanic warming. The reason is because storms form further out to sea, and there are more chances for a kink in the mid-atmospheric winds to direct them to the north.
A recent study in the Proceedings of the National Academy of Sciences (PNAS) purports to show an increase in hurricane-related storm surges that conveniently begins in 1923, which was during a decade-long lull in hurricane activity. Starting something at a low point pretty much insures a trend in any randomly distributed variable. This problem was noted by the above-mentioned Tom Knutson.
But the real killer to the hurricane-global warming hype comes from Dr. Ryan Maue (pronounced like the island) of Weatherbell Analytics. Using satellite data that gives global coverage beginning in 1972, Maue has calculated what is called the "Accumulated Cyclone Energy" (ACE) index. This is a mathematical integration of storm wind speed and longevity. There obviously is no change in hurricane energy that at all relates to warming, and it is currently near its lowest levels on record.
Ryan Maue's Accumulated Cyclone Energy (ACE) index for the globe (blue circles), Northern Hemisphere (black circles) and the Southern Hemisphere (area between the circles) shows no relationship between overall hurricane severity, frequency and global warming. Thanks to Ryan Maue and Weatherbell Analytics.
I trotted this out once in a discussion with Nick Kristof on CNN's Piers Morgan show on November 1. CNN, of course, cannot let go of the meme that Sandy (which was not a hurricane at landfall) was amped by global warming, so Kristof's substantive response was to accuse me of not publishing any scientific papers since 1992. (I emailed him the 8-page single spaced list beginning in 1992, presuming he will set the record straight with CNN—and also rag on whomever gave him that little bit of libel.). Morgan's producer also had copies of the papers dealing specifically with oceanic temperatures, climate change, and hurricane intensity.
What is really modulating Atlantic hurricanes is the distribution of temperature in the Atlantic. It was in an unfavorable mode in the 70s and 80s, which reversed in the mid-90s, concurrent with the start of a ten-year very active period. Since the big storm outbreak in 2005, the Atlantic hasn't been unusually energetic since then. In fact, we are now enjoying the longest interval in the modern record (seven years and counting) without a major (Category 3) hurricane strike in the U.S.
The bottom line is that, everything else being equal, warmer oceans should produce stronger or more frequent storms. But the change has clearly been so small that there is simply no detectable signal—and is likely to remain so for a long time. Further, everything else is almost never equal. It would have been nice if Mayor Bloomberg and Governor Cuomo had done a bit of fact-checking before stirring the global warming pot. As for Gore, the lack of any increase in hurricane energy related to global warming is just an inconvenient truth.