Posted by: bmeverett | November 13, 2012

Hurricane Sandy and Climate Change


As always, the Climate Community sees in every hurricane an obligation to warn the public about the dangers of global warming, and Sandy was no exception. New York Governor Andrew Cuomo could be counted on to join the chorus, and he didn’t disappoint us. Cuomo’s reaction to Hurricane Sandy was to opine that “Climate Change is a reality.” Advance organization of proper emergency responses and preparation for the inevitable natural disasters were not on the Governor’s agenda. Thousands of his constituents have been without light and heat for two weeks, and he’s concerned mainly with scoring political points. Good job.

Before we get too excited about the latest undeniable proof of climate change, let’s just bear a few facts in mind.

First, it is NOT TRUE that hurricanes have become more frequent. This assertion, like much of the climate agenda, is becoming conventional wisdom without a critical look. I always encourage my students to look at the data whenever possible, rather than rely on other people to tell them what’s true. There is an excellent data set maintained by Unisys Corporation at http://weather.unisys.com/hurricane/index.php. The data are naturally incomplete. We have pretty good data for Atlantic storms since 1851, although I suspect that many storms that did not make landfall were not recorded. In the Eastern and Western Pacific, we have data since the late 1940s. In the South Pacific and Indian Oceans, however, data before satellites became available in the 1970s are scattered and anecdotal and lack wind or pressure measurements. We are therefore limited to essentially a 60-year data series including the Atlantic and the Western and Eastern Pacific. Fortunately, most hurricanes (or cyclones or typhoons as they are called in the Pacific) are found in these areas.

Between 1949 and 2012, a total of 1,936 hurricanes were recorded, an average of 31 per year. During the six decades from the 1950s through the 2000s, the averages were as follows: 29, 30, 30, 32, 35 and 31. So far in the decade of the 2010s, we are on track for 29. Although the 1990s were higher than average, there is no obvious trend here.

Second, it is NOT TRUE that hurricanes have become more intense. Mayor Bloomberg recently claimed, “What is clear is that the storms we’ve experienced in the last year or so around this country and around the world are much more severe than before.” Really? Let’s look at the data. Between 1949 and 2012, there have been 214 recorded Category 5 hurricanes – the killer storms that cause the most damage – an average of 3.4 per year. The averages for the six decades from the 1950s through the 2000s were as follows: 4.2, 4.1, 2.1, 2.4, 4.1 and 3.8. If you are looking for a great talking point, you can claim that major storms have increased by 80% since the 1970s. It’s more likely, however that the 1970s and 1980s were unusually quiet. So far in the 2010s, we are on track for only 2.3 Category 5 storms per year.

Mayor Bloomberg has, I believe, succumbed to the “fallacy of the grocery store line.” How many times have you heard people in the grocery store exclaim, “Why do I always end up in the slowest line?” The reality is that they don’t. Finding yourself in a slow-moving line is annoying and therefore memorable. When people pick a fast-moving line at the store, however, they go on their way and pay no attention. Their data set is skewed by the irritating events they experience. It’s certainly true that Hurricanes Irene and Sandy have caused more fatalities and damage in New York City than any storms of the last 50 years. Climate change, however, is a global phenomenon, and New York City is too small a sample to draw any worldwide conclusions.

Third, it is NOT TRUE that hurricanes are becoming more destructive. One of the common arguments in favor of the catastrophic climate change hypothesis is that even insurance companies are recognizing the dangers of climate change by charging more for coastal storm insurance or even exiting this business segment altogether. Insurance companies may in fact be pricing into their premiums the risk of climate change. Insurance company risk pricing, however, says nothing about whether the climate change is natural or man-made – a point on which insurance companies can be agnostic.

Comparing the damage done by hurricanes is a difficult job, since the country undergoes dramatic changes over time. Roger Pielke, et al. have done an excellent job in “Normalized Hurricane Damage in the United States: 1900–2005” which can be found at http://www.nhc.noaa.gov/pdf/NormalizedHurricane2008.pdf. Pielke and his colleagues have reviewed the damage caused by hurricanes between 1900 and 2005 and adjusted these damage estimates for general inflation and for population and per capita wealth at the county level. In other words, they have estimated what damage major storms would have caused if they had hit their victims as they are today instead of as they were at the time. By decade, the damage from the 50 largest hurricanes was as follows (greatest to least): 1920s, 2000s, 1960s, 1940s, 1900s, 1990s, 1910s, 1950s, 1930s, 1970s, 1980s. No obvious pattern here.

The disaster modeling company Eqecat estimates the damage from Hurricane Sandy at about $50 billion. If true. Sandy would be only number 6 on the all-time list, behind not only (in $2005) Katrina ($81 billion in 2005) and Andrew ($58 billion in 1992) but also the two devastating Galveston hurricanes in 1900 ($78 billion) and 1915 ($62 billion) and the 1926 Miami hurricane – most destructive storm ever recorded in the US at $157 billion.

Pielke’s work suggests that the big issue regarding hurricane damage is coastal community development, not CO2 emissions.

Finally, we need to point out (yet again) the weakest argument that the Climate Community uses – one that Al Gore particularly abuses in his infamous An Inconvenient Truth. The argument goes like this: Hurricane Sandy may or may not have been caused by global warming, but this is what will happen to us if we don’t take urgent action. Pictures of hurricane damage are frightening, but have nothing at all to do with the argument over whether climate change is man-made, how much the climate will respond to greenhouse gas emissions and what exactly we should do about it. These are important questions. Let’s at least stick to the facts in our discussion.

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