As I write, Hurricane Sandy is making its way through New Jersey and New York wreaking havoc. Some of the press is claiming this “Frankenstorm” is a result of global warming. Some proponents of anthropogenic global warming (AGW) claim that hurricanes will become either more frequent or more intense as the planet warms.
Let’s look at some real data from Dr. Ryan Maue (http://policlimate.com/tropical/ ).
First, we see that hurricane frequency is not increasing:
Next, we drop down the energy scale a bit to include tropical storms and see that they, as well as hurricanes are not becoming more frequent.
Finally, we look at storm intensity and see that although this is quite variable, there is no overall trend:
From these data we see that hurricanes fail to follow the AGW predictions. So, either AGW alarmists are wrong or there is no recent global warming.
Is Sandy unprecedented? No, but it is unusually strong and widespread because of the confluence of a hurricane with a major cold front from the north.
Sandy made landfall in New Jersey, so look at the history of such hurricanes from “Hurricanes and the Middle Atlantic States.” That source provides brief descriptions of 21 hurricanes that affected New Jersey between 1821 and 2011. That list includes Hurricane Hazel on October 15, 1954. So even October hurricanes are not unprecedented.
Dr. Judith Curry, in a very long assessment of lessons learned since Hurricane Katrina in 2005, notes that there is still uncertainty of exact causes of frequency and intensity. But, the Pacific Decadal Oscillation (PDO) and the North Pacific Gyre Oscillation (NPGO) have dominant impacts on hurricane variability in the Pacific, and modulates the frequencies of El Nino/La Nina. Curry says, “I suspect that the combination of the PDO and NPGO can explain much of the variability in Ryan Maue’s analysis of Accumulated Cyclone Energy diagram, given that the majority of global hurricanes occur in the Pacific.” “In the Atlantic, the Atlantic Multidecadal Oscillation (AMO), the North Atlantic Oscillation (NAO), and Atlantic Meridional Mode (AMM) have all been invoked to explain variability in the Atlantic …”
Although the science of exact attribution is not settled, it does seem that AGW is not the answer since natural variability provides an explanation.