Two years after Hurricane Katrina, and what have we learned?
Strictly speaking, global warming did not cause Katrina, any more than you can pin a case of lung cancer on one specific cigarette. It's the additive impact of injecting more heat energy into the atmosphere that has some scientists concerned.
But two years after Katrina struck the Gulf Coast and flooded New Orleans, the state of the science on global warming and hurricanes remains in flux.
Kerry Emanuel at MIT says evidence suggests that global warming is boosting the power of hurricanes. He explains thus: As sea surface temperatures rise in the tropics, hurricane intensity rises. The warming of tropical sea surface temperatures over the past 50 years seems unprecedented over the last several thousand years, Emanuel says.
The temperature record is based on direct measurements going back to the mid-19th century and proxy evidence based on geochemical methods (for example, examining corals and the shells of marine microorganisms yields clues about the surrounding ocean temperature). Other scientists are not so sure about Emanuel's conclusion. Chris Landsea of the National Hurricane Center, for example, says his read of the evidence is that the impact of global warming on hurricanes is likely to be small.
How Joe Average Makes Sense Of Science
So what are lay people, especially those living in hurricane country, to make of this tempest in the field of tempestology? As is the case with any discussion of science, there is more to it than meets the eye, which makes it easy for ideologues with political agendas to demagogue the issue.
Americans naturally focus on Atlantic hurricanes that strike the United States. The climate change denial lobby points to last year's mild storm season in the U.S. as proof that climate change is a lot of hooey.
A hurricane is a hurricane, however, regardless of where it blows. Emanuel points out that his work is based on worldwide records. North Atlantic hurricanes make up only 11% of all tropical cyclones. He cautions that the incidence of Atlantic hurricanes that have made landfall in the U.S. is too small to draw statistically valid conclusions about tropical cyclones and global warming.
The Heart Of The Problem Is Coastal Development
But Emanuel and his critics in the hurricane science community agree on one thing. Regardless of whether global warming is boosting hurricane power or not, hurricane damage is likely to get worse because of the intensive scale of coastal development. Both Emanuel and Landsea signed an extraordinary statement last year declaring that land development in hurricane-prone areas is the leading hurricane problem facing the United States.
The statement says: Scores of scientists and engineers had warned of the threat to New Orleans long before climate change was seriously considered, and a Katrina-like storm or worse was (and is) inevitable even in a stable climate.
Eventually, the scientists wrote, they'll come up with definitive answers on how climate change will affect hurricanes. In the meantime, however, our lemming-like march to the sea requires immediate and sustained attention.
Hurricanes sweeping ashore over unpopulated swamps and barrier islands don't kill a lot of people. Cover empty lowlands with trophy homes, casinos, hotels, and office parks, however, and the next Katrina will come with a much higher price tag, even if Chris Landsea is right. If Kerry Emanuel's read of the evidence is closer to the mark, future generations will wonder at the scale of our carelessness.
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