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Wednesday, October 31, 2012

Was Global Warming Responsible for Sandy?

Short answer: no. 

From the New York Times, a discussion of whether global warming (in particular, the alleged man-made global warming) was responsible for making Sandy stronger than it otherwise would have been. (H/t Weasel Zippers).
There are several areas in which greenhouse-driven warming is thought to be a potential influence. The first is in the buildup of heat in southern surface waters. A paper published earlier this month in the Proceedings of the National Academy of Sciences was the latest to draw this conclusion, in this case through detailed analysis of storm surges recorded by Atlantic coast tide gauges:
We find that warm years in general were more active in all cyclone size ranges than cold years. The largest cyclones are most affected by warmer conditions and we detect a statistically significant trend in the frequency of large surge events (roughly corresponding to tropical storm size) since 1923.
But on longer time scales, the situation is murky because so many factors shape the formation and growth of tropical cyclones. I wrote in 2007 about a Nature paper by Jeff Donnelly of the Woods Hole Oceanographic Institution and others. Here’s the core conclusion:
Over the last 5,000 years, the eastern Caribbean has experienced several periods, lasting centuries, in which strong hurricanes occurred frequently even though ocean temperatures were cooler than those measured today, according to a new study.
That’s the Caribbean, of course.

What about the Northeast? Here’s Hurricane Sandy. Last year was Hurricane Irene and then there was Hurricane Floyd in 1999. But when you look back in time in this region, big questions arise about just what constitutes a superstorm.

As I’ve written before, the great tropical storm and floods that devastated Vermont in November 1927 (and after Irene) appear to have been minor compared to repeated past hill-scouring superfloods, according to an important study of lake-bed sediments revealing storm patterns and intensities in recent millenniums.

Here’s the lede from my story on that paper, published one decade ago:
Four times since the last ice age, at intervals roughly 3,000 years apart, the Northeast has been struck by cycles of storms far more powerful than any in recent times, according to a new study. The region appears to have entered a fifth era in which such superstorms are more likely, the researchers say.
 In an update to the author's post, he also includes the following:
Martin Hoerling, a meteorologist at the National Oceanic and Atmospheric Administration focused on the forces influencing extreme weather, sent this note:
Great events can have little causes. In this case, the immediate cause is most likely little more that the coincidental alignment of a tropical storm with an extratropical storm. Both frequent the west Atlantic in October…nothing unusual with that. On rare occasions their timing is such as to result in an interaction which can lead to an extreme event along the eastern seaboard. As to underlying causes, neither the frequency of tropical or extratropical cyclones over the North Atlantic are projected to appreciably change due to climate change, nor have there been indications of a change in their statistical behavior over this region in recent decades (see IPCC 2012 SREX report).

So, while it will rain like “black cats and Frankenweenies” over the midatlantic, this is not some spell conjured upon us by great external forces….unless you believe in the monster flicks of Universal Stuidios fame!
 Comments from other scientists also discount that Sandy was caused by man-made global warming.

So, in short, this is just another example that the 20th Century was actually rather benign in terms of extreme weather and other natural disasters, but we may be entering more "normal" periods. The greater destruction of property is simply a result of people building in flood-prone areas, and a greater concentration of people and buildings. If we had weather and climate events, earthquakes and tsunamis, comparable to the first two decades of the 19th century, we would be seeing hundreds of millions of people dead or displaced.

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