The global-warming God: must it now be appeased?(HURRICANE KATRINA II)

FOR years, I have been concerned that a major hurricane strike on New Orleans could provoke legislation on global warming that will do absolutely nothing about tropical cyclones, but harm the U.S. economy for decades. We began seeing the shape of things to come when Robert F. Kennedy Jr. claimed that Katrina's severity was related to President Bush's reluctance to cap carbon-dioxide emissions, and Hillary Clinton declared she wanted to establish a commission to investigate the government's response to the hurricane.

Hurricane Katrina's magnitude was not changed by global warming. In fact, despite a hundred news stories to the contrary, it's not at all clear that any such warming will result in more frequent, let alone more intense, tropical cyclones. Take, for example, the recent rise in hurricane frequency in the Atlantic Basin; it's as if we have returned to the 1930s, '50s, and '60s, when storm activity reached a ferocious height before settling down for several decades.

Keep in mind, however, that there are some differences between now and then. Today's hurricanes tend to concentrate in Florida and the Gulf of Mexico, whereas in mid-century they repeatedly struck the Atlantic coast--all the way to Canada. This is worth noting because, in a warming world, simple reasoning predicts that activity should have moved north, not south. Obviously things are not so simple with hurricanes and climate change.

But the North Atlantic is just one of the world's many hurricane basins. In general, there are more tropical cyclones per year in the eastern North Pacific--off the Mexican coast--but few notice them because they rarely hit land as consequential cyclones. Instead, they peter out as they migrate westward into cooler waters. In fact, only one subtropical ocean, the South Atlantic, has virtually none of these storms.

So, rather than focusing exclusively on what's happening in our provincial part of the North Atlantic, we should be asking what is happening to hurricane activity around the planet. And the answer is ... nothing. More specifically, there has been no significant movement in either frequency or strength despite a warming trend since 1975, a cooling trend in mid-century, and a warming trend in the early 1900s that was similar to what we see today.

Yes, there is a much-cited paper in the scientific magazine Nature by Kerry Emanuel that claims that hurricanes have doubled in power in the last 30 years. But there are at least tour manuscripts in review at Nature that challenge this result. Indeed, people who normally stay out of the global-warming catfight, like the University of Colorado's Roger Pielke Jr., have been blogging that the peer-review process at Science--Nature's American competitor--has been badly compromised on the subject of global warming and weather-induced damages.

The Emanuel argument simply does not stand up to scrutiny. Put it this way: Since Atlantic hurricanes have a roughly equal chance of striking the U.S., and if they had doubled in power, then surely the amount of damage they have caused--after adjusting for population and property-value changes--would show an obvious upward trend. But, when allowing for these factors, as Pielke has, we cannot detect any such tendency. In any case, if hurricanes had actually doubled in power, then the insurance companies would already have been blown to smithereens. They're still here.