By Alan Prendergast
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A key scene in the film An Inconvenient Truth is the moment Al Gore reveals that we are literally reaping the whirlwind. He stands on a stage, palms up in silent supplication, while images of a flooded New Orleans play on a big screen behind him. Pump enough crap in the air, the ocean warms up, and boom! -- Katrina trashes the Gulf Coast.
Such oversimplified notions of cause and effect exasperate Bill Gray. The scientists who've tackled the global-warming/ hurricane connection -- currently one of the hottest questions in science -- have stopped far short of blaming any one storm or season on CO2 emissions. But some have concluded that rising temperatures over the past three decades have produced more intense storms, and that a growing number of monster hurricanes should be expected in an increasingly warmer world. Such statements are greeted in Gray's office like a shot across the bow. The global-warming crowd has taken the battle to his turf.
The first major salvo was fired two years ago by Kevin Trenberth, head of climate analysis at NCAR, who suggested that warmer oceans were producing stronger hurricanes. That was followed by a paper last summer from Kerry Emanuel, a well-respected hurricane expert at MIT, who re-examined historical data and found the intensity of storms in the Atlantic had basically doubled in thirty years, a phenomenon he attributed to rising water temperatures linked to global warming. Then came a study by NCAR's Holland, Webster and two other Georgia Tech researchers, Judith Curry and H.R. Chang, who'd set out to challenge Trenberth's work but concluded that the number of intense tropical storms had doubled around the world since 1970.
Gray took them all on. There are too many factors besides sea-surface temperature that influence hurricane intensity, he insisted. The data his colleagues were using was suspect, he told reporters, because of erratic weather information-gathering methods in certain parts of the world in the 1970s. They were playing with numbers and ignoring the cyclical nature of hurricane seasons. You want to talk busy hurricane seasons? How about 1933? From 1933 until 1965, the Florida peninsula was hit by major storms eleven times. From 1966 until 2003, it was hit only once. Up until the last two seasons, in fact, there'd been a great downturn in major storms making landfall, despite increased activity in the Atlantic.
"Had the last two years not had such bad hurricane damage, we wouldn't be talking about it now," he says.
Gray was hardly alone in his dissent. NOAA officials denied that global warming had anything to do with current hurricane patterns, which were "due to natural fluctuations and cycles." Chris Landsea, a former Gray student who now works as science operations officer at NOAA's National Hurricane Center in Miami, re-crunched the numbers and found no increase in the number or intensity of Category 4 and 5 hurricanes globally over the past fifteen years; by his calculations, even a four-degree increase in ocean temperature by the end of this century would have only a small effect on hurricane intensity. CSU's Klotzbach zeroed in on the past twenty years of storm data, considered more reliable than that of previous years, and found a large increase in major North Atlantic storms and a large decrease in Northeast Pacific ones, but no global trend that would support the notion that global warming is whipping up stronger hurricanes.
The rebuttals have prompted a flurry of additional papers and responses; Georgia Tech's Curry, for example, has suggested that Klotzbach is "cherry-picking" his data. But the most biting exchanges have involved Gray's critiques and the counter-volleys. Gray has "brain fossilization," Curry told a Wall Street Journalreporter a few weeks ago, and "nobody except a few groupies wants to hear what he has to say."
Stung, Gray has responded in kind. "I've always liked her, but she doesn't know a damn thing about tropical storms," he says. "They want to put me on the fringe, sure. My brain is fossilized. I'm an old curmudgeon who doesn't change with the times. They use anything they can against you."
Webster says he's tried to keep the debate with Gray on the scientific high ground, without success. "Bill, for some very good reasons, has been the go-to man on hurricanes for the last 35 years," he says. "All of a sudden there are a lot of people saying things Bill doesn't agree with. And they're getting a lot of press -- more press than I like, actually. I like the ivory tower. But he's become more and more radical."
Shortly after his paper was published, Webster recalls, "I had a conversation with Bill in which he said he'd have to 'take me down.' Then I started getting messages from reporters, asking, 'What's this about you taking money? What's this about voodoo science?'"
After Gray questioned Emanuel's motives in a debate at an American Meteorological Society meeting in Florida, other researchers began to avoid public dialogue with him. Holland withdrew from a joint appearance with Gray on an AMS panel in Atlanta last February.
"Bill has always been a natural thinker, the sort of person who asks difficult questions," Holland says. "The unfortunate difference now is the way personalities are being brought into it -- and the denigration of perfectly good scientific techniques."