Calmer Weather: The Spin on Greenhouse Hurricanes

Calmer Weather: The Spin on Greenhouse Hurricanes

May 01, 1997

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Somehow, the public has been convinced that the future will include an increasing number of hurricanes of greater intensity that will cause substantial damage throughout the world. Worries about hurricanes have been added to concerns regarding heat stress, sea level rise, droughts, pestilence, crop failures, water shortages, wildfires, and all the other components of the greenhouse disaster.

What is most surprising about the claims regarding the increasing hurricane numbers and intensity in the greenhouse world is the general lack of theoretical or empirical evidence that can be found in support of the claim, particularly if one deals with the issue of hurricane numbers. Much of the evidence we have to date argues against the link between global warming and increased hurricane activity.

Concerns about warming-induced hurricanes got their start in 1986 when noted M.I.T. scientist Kerry Emanuel published a paper showing that a fall in sea-surface temperatures could prevent intense hurricanes, and that a warmer sea-surface could theoretically increase the upper limit of a storm's intensity. This publication set the stage for several more important Emanuel papers that would ultimately have a large impact on the greenhouse link to increased hurricane activity and the formation of "hypercanes" - particularly intense hurricanes. Emanuel's research never predicted increased hurricane activity, but instead provided a theoretical discussion of the upper limit of hurricane intensity, given a very large increase in sea surface temperatures. Nonetheless, it was enough to encourage fear mongering about warming-induced hurricanes.

Shortly thereafter several articles appeared in the professional literature that cast serious doubts to the notion that hurricane activity was on the rise. This research showed that Atlantic hurricane activity over the period 1970 to 1987 was less than half of the activity observed for the period 1947 to 1969. Additional research suggested that a warmer world would actually produce fewer storms.

Throughout the 1990s, articles have appeared in major journals supporting and challenging the prediction of increased hurricane activity in the greenhouse world. Researchers found great year-to-year variability in the hurricane data, but no significant evidence to link hemispheric temperatures to variations in hurricane activity. Scientists examining long term hurricane trends found a clear downward trend over the past 50 years. The Intergovernmental Panel on Climate Change, often represented as the scientific consensus, concluded in 1995 that: "Although some models now represent tropical storms with some realism for present day climate, the state of the science does not allow assessment of future changes." Scientific research into hurricanes has not produced ringing endorsements for the popular claim that global warming is causing or will cause more hurricane activity.

One of the most interesting ironies in the claims that recent hurricane activity is linked to warming is that the warming itself may not have occurred - there is strong evidence from satellite measurements that the planet has actually cooled over the past few decades. Blaming hurricanes on recent warming is flawed on all fronts - not only is there little to no linkage between global warming and hurricane activity, but there seems to have been no warming in recent decades either.

A highly popular view has developed that the buildup of greenhouse gases will cause the sea-surface and atmospheric temperatures to rise, and that this will result in an increase in the number and intensity of damaging hurricanes around the world. But, as with so many other elements in the greenhouse debate, the theoretical and empirical evidence is not very supportive of this claim. Indeed, there is plenty of evidence to argue that the greenhouse effect will suppress hurricane activity. In the end, there is little reason to expect an increase in hurricane activity throughout the upcoming century.