First the monstrous Katrina, now the evil Rita, and we still have two months of hurricane season to go. Will we spend them looking to the heavens not in wonder but in mortal fear? Dear sky: Is it something we said?
Since the sky seems too angry to have a civil conversation, let's seek answers in science and poetry. In two newly published studies, climatologists use graphs, formulas and carefully hedged sentences to explain how the interlocking phenomena that non-scientists call "global warming" may be turning little nuisance hurricanes into Katrina-style killers. And as for poetry, the party-hearty rapper Nelly (I use a broad definition of poetry) issued his warning years ago: "It's gettin' hot in heerrre. . ." Somehow I doubt there's a Nelly playlist on George W. Bush's iPod, so I'll stick to the science -- and hope some of this penetrates the president's adamantine resistance to inconvenient facts.
The sky's wrath begins in the sea. Most scientists agree that the surface temperatures of the world's tropical seas -- where hurricanes, which form only over warm water, are spawned -- have increased by about 1 degree Fahrenheit over the past 30 years. That doesn't sound like much. But given the vastness of the oceans blue, this slight difference translates into an enormous amount of energy to nourish developing storms.
A group of researchers led by Peter J. Webster, a professor of earth and atmospheric sciences at Georgia Tech, took a detailed look at data on hurricanes worldwide between 1970 and 2004. The one piece of comforting news is that the group's paper, published this month in the journal Science, finds no solid evidence that rising sea-surface temperatures have resulted in more hurricanes.
But the rest of the news from the study is alarming: While the overall number of hurricanes is unchanged, a lot more of those hurricanes are Category 4 or Category 5 behemoths -- the Katrinas and Ritas of the meteorological world. Webster compared data for five-year periods beginning in 1970. In the first five years of the 1970s, there were fewer than 50 behemoth hurricanes worldwide; in the first five years of the new century, there were almost 90.
In other words, if it's your city's turn to get raked by a hurricane, it's more likely now than in years past to be a big one.
Separately, Kerry A. Emanuel, a professor of atmospheric science at MIT, published a paper in the journal Nature last month that reaches a similar conclusion. Emanuel uses a more arcane measure called the "power dissipation index" that is related to both the duration and intensity of tropical storms, but the bottom line is the same: much more destructive power being released by hurricanes, an increase that is "highly correlated" with sea-surface temperatures.
Global warming theorists have been predicting more Category 4 and Category 5 storms for years. Neither of these studies claims to definitively prove that the theorists are right, and neither tells us anything about the genesis of the evil sisters Katrina and Rita or any other specific storm. The butterfly-flapping-its-wings-in-China explanation is as good as any.
Nor does either study wade into the argument over whether human activity -- burning fossil fuels, mostly -- contributes to the rising temperatures. The White House, if it wants, can continue to ignore the scientific consensus that the carbon dioxide our cars and factories spew with such abandon is trapping heat in the atmosphere and the oceans, with results that are unpredictable and potentially disastrous. In the real world, outside of the president's cone of silence, the question is pretty much settled. Some business leaders are already beginning to come around, and eventually they'll drag the administration along.
Two mega-storms in a row ought to help concentrate the mind. It's chilling to see those satellite photos of the entire Gulf of Mexico filled with an angry swirl of cloud. Everyone involved in rebuilding New Orleans and the Gulf Coast ought to have that menacing image tacked to his or her wall.
A new New Orleans will be in trouble from the beginning if no attempt is made to restore the wetlands south of the city, which would serve as a buffer from big storms. Putting people back into the worst-flooded neighborhoods might be just a guarantee that soon they'll get flooded again. And as officials, corporations and homeowners -- including Trent Lott -- think about rebuilding their Riviera along the Mississippi and Alabama coast, they'd better keep in mind that "once in a lifetime" storms now come in a new package.
It's buy one, get one free, and they're jumbo-size.