Wednesday, December 13, 2006

The hurricane season

I’m in New Orleans for a meeting. Naturally, it has me thinking about hurricanes, climate change, and just how toxic the subject has become.

The 2006 Atlantic cyclone season came and went with far fewer storms than originally forecast. Why? El Nino conditions caused greater upper-level wind shear, slowing hurricane development and helped divert the storms that did develop safely into the middle of the Atlantic. This was relief for many coastal dwellers in the Caribbean, the Gulf Coast and the Atlantic seaboard.

It should also be a cautionary tale for everyone out there talking about the threat posed by climate change.

Hurricane Katrina and the devastating 2005 hurricane season provided a legitimate opportunity to raise concerns about the possible future effects of climate change. Not because those events were caused by climate change, or that the overpopulation of vulnerable coastal areas is a huge, separate problem, but because some research suggested it was the type of event that could occur more frequently in a warmer climate.

Hurricanes have become a rallying cry for the greenhouse gas reduction movement – just look at the posters for An Inconvenient Truth. The 2006 hurricane season was promoted like the upcoming fall television season. As I remarked back in June, the press covered “opening day” of the hurricane season, a loose date not exactly etched in the climate’s schedule, as if we were all awaiting the opening pitch of the baseball season, and all the balls had been juiced.

It was crazy. Not because there is serious uncertainty in the science relating hurricane intensity and climate change (see the recent statement from a WMO meeting on tropical storms). But because even if future warming in the tropical Atlantic does increase the likelihood of more intense storms, there will still be weak hurricane seasons. Just like even if the planet warms by several degrees, there will still be cold days.

Everyone forgot the basic rule, the difference between weather and climate. You just can’t lean on an individual event, or an individual season, for proof of climate change. It is a house of cards. Your argument is doomed to collapse.

That doesn’t mean people should stop talking about hurricanes. It is important to continue to study and discuss the effect of climate change on hurricane intensity. Climate models can be used to investigate how warming could alter the probability of individual events like more powerful storms or storm seasons. Depending on those results, individual storms or storm seasons can continue to be legitimately seen as examples of events that some research suggests may be more common in the future.

But those working to promote concerns about climate change must not fall into trap of looking at individual storms or storm seasons as the smoking gun for climate change. It has emotional appeal - but it is fundamentally bad science. Hurricane Katrina and the 2005 Atlantic cyclone season did not end the “debate” about climate change, nor did the weak 2006 Atlantic cyclone season reignite the “debate”. Let’s not reduce it to that.

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