The International Summit on Hurricanes and Climate Change was held in May of 2007 on the Greek island of Crete, where 77 academics and stakeholders from 18 countries participated in a free-ranging discussion of hurricanes and climate change, as reported by Elsner (2008) in the Bulletin of the American Meteorological Society. In introducing his synopsis of the four-day meeting, the Florida State University researcher says that certain studies "suggest that tropical cyclones are becoming more powerful with the most dramatic increase in the North Atlantic," and that "the increase is correlated with an increase in ocean temperature." However, he notes there is "a debate [our italics] concerning the nature of these increases," with "some studies attributing them to natural fluctuations, and others suggesting climate change related to anthropogenic increases in radiative forcing from greenhouse gases."

Well, a debate over something suggests that the subject in question is about as far from being settled as it could possibly be; and Elsner rightly reports that "the question of whether we can ascribe a change in tropical cyclone intensity to anthropogenic climate change is still open." And on the question of a warming-induced increase in hurricane frequency, the science is even more unsettled. Although "most models," in his words, indicate "an overall decrease in the number of storms," he notes that not even all models agree on the change in individual basin tropical cyclone numbers, "with some models showing an increase in the Atlantic and others a decrease."

So what should governments conclude -- as well as actually do -- about the matter? How about not concluding anything, and doing likewise? The first of these two suggestions, in fact, appears to be the strategy of the hurricane researchers themselves, as they plan to hold a second summit on the subject sometime in 2009. Until then, at least, it would appear that the debate will continue, as it obviously should, while researchers continue to gather more data; for what is at stake is clearly too important for scientists and governments alike to leap to a premature "consensus" on the issue.

In this regard, for example, Elsner says that what he calls paleotempestology -- which he defines as the study of prehistoric storms based on geological and biological evidence -- indicates the presence of more hurricanes in the northeastern Caribbean Sea "during the second half of the Little Ice Age when sea temperatures near Puerto Rico were a few degrees (Celsius) cooler than today, which provides some evidence that today's warmth is not needed for increased storminess." Similarly, he reports that "sedimentary ridges in Australia left behind by ancient tropical cyclones indicate that activity from the last century under-represents the continent's stormy past."

On the other hand, Elsner notes that a spatially-limited set of hurricane proxies or historical records may be insufficient "to distinguish changes in overall activity from changes in local activity due to shifts in [storm] tracks." As a result, he rightly concludes that in order "to understand how climate influences local changes in tropical cyclone activity, more research is needed to identify factors influencing tropical cyclone tracks," as well, we would add, as more paleotempestology studies from a more diverse set of localities.

Consequently, although people on both sides of the climate-change/hurricane debate might like to see their particular views of the subject accepted as things stand right now, it would appear that considerably more real-world data is needed before a valid consensus on the issue can be reached.

Sherwood, Keith and Craig Idso

Reference
Elsner, J.B. 2008. Hurricanes and climate change. Bulletin of the American Meteorological Society 89: 677-679.