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There was no hurricane swirling in the Atlantic on December 15, 2006, when Kerry Emanuel once again spoke at the American Geophysical Union meeting in San Francisco. It was just over a year since he’d issued his dramatic challenge to NOAA, telling the agency to stop censoring its scientists. A lot had changed since then. A lot hadn’t.
NOAA had, once again, been caught gaming the dissemination of scientific information. The agency’s lesson apparently had not been learned; perhaps the architecture of the Bush administration made such growth impossible. But Democrats had recently retaken Congress and stood poised to bring about a more significant shaming than either Emanuel or the news media could muster. Already, talk was circulating about congressional hearings to determine why political appointees seemed to be guiding the dissemination of sensitive scientific information across so many branches of the government. Democrats would be looking into the “war on science” that had been waged over the past six years, and NOAA and the Department of Commerce would not escape their attention. Democratic senator Frank Lautenberg of New Jersey, home to the GFDL, had said explicidy that he would press for hearings on the agency’s behavior.
On the scientific front, there were also signs of movement. For starters, Emanuel had to some extent modified his thinking over the course of the year. He’d become less confident about some of his previously published conclusions, while he stood strongly by others. And he’d shifted his outlook for what any scientist would recognize as the right reason: New research made him change his mind.
Both sides had been eagerly awaiting the aforementioned study by meteorologist Jim Kossin of the Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin-Madison. Kossin, too, had been a student of Gray’s at one time. As the hurricane-climate debate began to whirl wildly in 2005, he had volunteered to reanalyze the disputed storm-intensity data and help sort matters out. Both groups of scientists saw Kossin as a fair, unbiased arbiter.
The resulting study hadn’t been officially published when Emanuel spoke in December. But it had gotten around, and Kossin had presented the results publicly. He and his team had created a homogenous global database of hurricane satellite images from July 1983 through December 2005—169,000 pictures of some two thousand storms, all of them at the same coarse resolution. Then Kossin’s team applied an unvarying automated algorithm to each image to determine the storm’s intensity. The whole approach was designed to get around the problem of changing human measurement practices over time—“primate change,” as one of the study’s coauthors had jokingly put it. The method might not be as accurate as storm flights, but it had the advantage of being entirely consistent.
When Kossin’s results came out, they seemed to have something for everyone. Hurricane intensity had indeed been trending strongly upward in the Atlantic. And it had apparently been trending downward in the Northeast Pacific (the year 2006 had bucked both trends). This suggested that the data maintained by the National Hurricane Center, which tracks both basins and is the only global forecasting center to perform regular aircraft reconnaissance into storms, was highly reliable.
For the other basins, though, aircraft reconnaissance had either been canceled (as occurred in 1987 for the Northwest Pacific) or never carried out in the first place. And here Kossin’s analysis suggested—in marked contradiction to the Emanuel and Webster studies—no significant upward trend in storm intensity. At least based upon this slicing of the data, then, the hurricane response to global warming globally didn’t look nearly as predictable as anyone had thought. Kossin’s was just one attempt to reanalyze the contested records, but if nothing else it certainly showed that they remained contested. As this book went to press, debate over the global hurricane intensity record showed no signs of any quick resolution.
Kossin’s work had prompted Emanuel to modify his outlook. “I’d have to step back from part of those conclusions,” he told me frankly when we talked in late October 2006 and I asked how his 2005 study stood up in light of Kossin’s research. But Emanuel certainly wasn’t stepping down on the Atlantic, the basin where the data were the most reliable and the trend best documented. Alongside “Webster, Holland, and Curry, Emanuel increasingly suspected that when it came to hurricanes, the United States, Central America, and the Caribbean might be getting the worst of global warming—or at least might be seeing the effects of climate change in the most easily demonstrated fashion.
Storm numbers in the Atlantic basin had risen sharply since 1995, tracking rising tropical ocean temperatures; and more numerous storms had also meant more numerous intense ones (not because the proportion of intense to weak storms had changed, but simply because there were more storms in total). As Holland now put it in his presentations, looking toward the future, he could think of “no rational reason” to expect a decrease in Atlantic hurricane activity. Indeed, Holland’s and Webster’s growing confidence that the increase in Atlantic storm numbers could not be explained without invoking global warming had drawn them into a new data-centric argument with Landsea, this time over storm count records rather than storm intensity records.
That debate, too, remained unresolved, but its very existence signaled an evolution in scientific thinking since the 2005 hurricane season, and since the first appearance of the Emanuel and Webster team studies. While those famous papers had sought to demonstrate trends across global hurricane basins, it now seemed possible that global warming was affecting different parts of the world differently. In short, there might be winners and losers; the Atlantic might respond much more sensitively to warming oceans than, say, the Northwest Pacific. Given the complexity of the ocean-atmosphere system and the varied environmental factors that affect hurricanes, such an unpredictable response did not seem at all implausible. In fact, a climate-modeling study performed using Japan’s powerful and high-resolution Earth Simulator had found a similar result: The Atlantic might have both more frequent and stronger storms, even as global storm numbers decreased on average (but global intensity increased).
If so, that probably meant only more trouble for the United States in the coming years.
It was in this context—of developing and changing knowledge—that Emanuel spoke in San Francisco. It was the day after Al Gore himself had held forth at the AGU conference, decrying political interference with climate science and telling thousands of geoscientists that they must learn to become better communicators, to explain and defend the knowledge they had brought into the world. So many scientists had shown up to hear Gore that they couldn’t all fit into the San Francisco Mariott’s giant lecture salon, and hundreds wound up watching the speech on video screens. For this crowd, global warming was a foregone conclusion.
Attendance at the meeting itself was higher than ever this year—more than 14,000—and the number of scientists giving papers on hurricanes and climate had also spiked. There were so many presenters that they’d been split up into separate panels. New results were coming in about everything from model-projected changes in future vertical wind shear to the quality of the hurricane database. This profusion of interest, more than anything else, showed that the process of science was ultimately working in the way it’s designed to—despite the many interferences over the past year by the media, government agencies, and special-interest groups, and despite scientists themselves sometimes making matters worse.
By the time Emanuel’s talk began, the presentation room at the Moscone Center was full. But anyone expecting fireworks this time around had come to the wrong place. Emanuel spoke in his trademark well-punctuated complete sentences and refrained entirely from political remarks. Matters were considerably calmer after the 2006 hurri cane season than they’d been after the 2005 one, and the talk reflected that mood.
Instead, Emanuel presented a sublimely simple review of what we know about hurricanes and climate, especially as it concerns the Atlantic. Storm numbers there had been rising; so had hurricane power dissipation; and it all closely followed a trend of rising sea temperatures. Emanuel particularly emphasized that we must stop focusing narrowly on traditional measurements, such as storm numbers and intensities, to gauge overall hurricane activity: “I happen to think that’s not what nature really cares about.” Weak tropical storms shouldn’t be viewed as “in the same league” as Category 5 hurricanes, Emanuel explained. Look at how much total power storms were dissipating in the Atlantic—that was the measure that followed sea surface temperatures most closely of all.
At this juncture Emanuel introduced an equation, a long and complicated hieroglyphic that governed the maximum theoretical wind speed that a given hurricane has the potential to achieve. For those who could not decipher it, he explained some of its terms: the sea-surface temperature, the outflow temperature, the speed of the trade winds, the greenhouse effect itself. The equation plainly showed that sea-surface temperatures aren’t the only factor controlling a hurricane’s theoretically achievable intensity. But for the Atlantic’s main hurricane-formation region, sea temperatures were unmistakably trending upward.
Some scientists, Emanuel had noted, had postulated a natural cycle to explain all this. In fact, the presenter who had preceded Emanuel, modeler Tom Delworth of GFDL, had argued that a global warming trend had been laid atop a natural oceanic cycle in the Atlantic. But Emanuel didn’t think Delworth’s more middling approach could cut it, at least when it came to the regions of the Atlantic critical to hurricanes. For as he explained in his talk, “You can’t see much difference between the tropical summertime North Atlantic, where the hurricanes develop, and the Northern Hemisphere temperature.” This suggested a simpler explanation, Emanuel said: Whatever was causing the Northern Hemisphere temperature change was also causing temperature changes in the hurricane development region.
That thing, of course, was global warming.
There Emanuel ended, without even driving home the point, because he didn’t really need to. The implication was clear, and what remained unsaid was just as powerful as what had been stated. The global picture of how hurricanes were responding to climate change still posed many mysteries; but for the Atlantic, much seemed to be coming into focus. And it didn’t look hopeful at all.
Something else remained unsaid, at least for the moment. It hadn’t yet been announced, but Emanuel had been named the 2007 recipient of the American Meteorological Society’s Carl-Gustaf Rossby Research Medal, the society’s highest honor and the meteorological equivalent of being inducted into baseball’s Hall of Fame. In Emanuel’s case, it was hard to imagine that the timing of the award could be purely coincidental. Not after the 2005 hurricane season, and the high-level science fight that had followed it.
Two decades earlier, Emanuel had fundamentally linked hurricanes to the climate, and to the greenhouse effect, through his thermodynamic account of how hurricanes work, why they intensify, and the maximum potential intensity they can achieve under different environmental conditions. And now, thanks to innumerable factors that included not only the significance of his work but also politics and the weather itself, these ideas had become some of the most influential in all of meteorology.
When two simultaneously churning hurricanes move close to one another, they can sometimes get drawn into an elaborate cyclonic dance known as a Fujiwhara interaction, in which the storms seem to lock arms (or at any rate, rain bands) and twirl around a central point even as they also move together in the same direction.
One theme that emerged from much of the research presented at the December 2006 AGU meeting was that hurricanes and the climate system might, in a very broad sense, be locked in their own in teractive dance. Even as the climate changed hurricanes, hurricanes might also change the climate. It was just the sort of idea you’d expect to see emerge as a bunch of climate scientists stampeded into a field like hurricane research. And once again, it represented a potential change in paradigm from what had gone before.
In the 1979 paper that introduced his famous six genesis parameters, and the even more famous 80-storms-per-year figure, Gray had discounted the idea that hurricanes play an essential role in the climate system on a mega-scale. “The tropical cyclones’ contribution to the globe’s mass, moisture and energy budget could probably be accomplished (were their formation not to occur) by a greater number of weaker tropical disturbances existing in their place,” he wrote. But scientists like Emanuel, Trenberth, Holland, and Webster had now begun to think about the matter very differently.
As usual, Emanuel had been the first. For half a decade, he’d been arguing that hurricanes shape the climate by stirring the seas and driving ocean heat transport, with stronger storms helping to drive more heat to the poles than weaker ones and with stronger storms occurring in warmer climates. New research on this subject now appeared at the AGU meeting, where it became apparent that Emanuel had inspired a number of younger scientists—his own band of proteges—to take up the matter. As one of them, Matthew Huber of Purdue University, put it to me, “The good news is that the world may have a tropical thermostat that helps keep the planet cool. And the bad news is that that may be tropical cyclones running around all the time.”
At the same time, Trenberth, Webster, and Holland had been advancing a complementary account of the role of hurricanes in the climate system. They started out from the fundamental observation that hurricanes are a powerful mechanism for extracting the ocean’s warmth and transporting it many miles into the air, using some of that energy to drive winds in the process. In short, hurricanes do a great deal to transport heat out of the tropics, where especially during the summertime, energy from the beating sun accumulates in the oceans. That heat cannot simply radiate back up to space due to the strong greenhouse effect of water vapor over the oceans. This makes convection—in the form of both tropical thunderstorms and hurricanes—a critical mechanism for keeping the system in balance.
Compared to individual thunderstorms, however, hurricanes do a far more efficient job of pumping heat above the lower parts of the atmosphere and cooling down the oceans. So the climate scientists reasoned that hurricanes might in some sense be a “release valve,” a way of ventilating the tropical oceans and redistributing heat. “Would the climate system notice if they didn’t occur? I think it would,” says Trenberth. If so, that could have a very large bearing on how hurricanes might change as the climate changes. Indeed, it suggested that they would have to change, perhaps quite dramatically, to keep pace with a warming world.
Collectively, then, Webster, Trenberth, Holland, and Emanuel were postulating that hurricanes might play a role in the climate system similar to—if perhaps less obvious than—the role played by extra-tropical cyclones, which mix together warm tropical and cold polar air and thus also redistribute heat. Emanuel focused on how hurricanes might perform this climate-scale task through the oceans; Webster, Holland, and Trenberth focused on the atmosphere. But they converged on this point: Hurricanes might be having a nontrivial impact on the global climate system, and this effect had not previously been taken into account, especially in climate models.
This kind of thinking, in turn, seemed to finally promise a way of solving a great mystery: Why are there about 80 or 90 tropical cyclones per year, as opposed to 8 or 9, as opposed to 800 or 900? The climate scientists suspected this general regularity existed because, in some sense, that was the right number of storms to perform a particular “job” within the present climate. In the context of a changing climate, however, there was no guarantee these numbers would remain the same—especially since when it comes to stirring the oceans, or pumping heat out of them and into the atmosphere, all storms aren’t equal. “If you think of hurricanes as the cart horses of taking energy away from the tropics, then you need less of them if they’re stronger,” Webster explained. Along similar lines, Emanuel’s approach emphasized that the strongest hurricanes perform much more ocean mixing and thus theoretically ought to bring about much more heat transport.
To be sure, much of this reasoning remains at a fairly early and speculative stage. But we’ll get firmer answers about the role of hurricanes in the climate system soon enough, and some may come from the field of “paleotempestology”—also a prominent focus at the AGU meeting. The term, originally coined by Emanuel, refers to the study of how hurricanes have varied in past eras of the Earth’s history, including periods characterized by very different climates. It’s a new field and faces significant hurdles. Tracing hurricane activity back into the past, whether through historical archives or through other types of naturally preserved records (so-called proxies), is tough work. Yet here, too, intriguing results seem to be rolling in.
In particular, scientists have learned that some coastal lakes, marshes, and ponds preserve evidence of “overwash” events, in which powerful hurricane storm surges deposited sand layers that can be detected in sediments and dated, thus providing a sense of how frequently the strongest storm events recurred. Given enough paleotempestological records, a picture might emerge of how hurricane activity had varied in climatic regimes dating back thousands or even hundreds of thousands of years.
In fact, that’s starting to happen. Taking sediment cores in western Long Island, Jeff Donnelly of the Woods Hole Oceanographic Institution has been able to identify the sand record left behind by the 1821 hurricane that gave William Redfield the idea of rotary storms. Other cores from the northeastern United States reflect the impact of the great 1938 New England Hurricane, 1954’s Hurricane Carol, and others. Collectively, meanwhile, Donnelly’s sediment cores taken from New England as well as from Vieques, Puerto Rico, suggest an apparent period of strong hurricane activity up until a thousand years ago, followed by a period of inactivity, followed by another period of strong activity starting around the year 1700 and running to the present.
Just as with research on hurricane-climate feedbacks, the study of hurricane variations on long time scales remains in its infancy. Still, it’s hard to overstate the potential significance of this growing body of work. Call it the field of “hurricane climatology.” Thermodynamic theories like Emanuel’s and Hollands can calculate, for a given set of conditions, how powerful a single hurricane has the potential to become. But that’s just one hurricane. The ability to understand global hurricanes in a global climatic context, however, could lead to a far more satisfying and complete theory of how storm numbers and intensities alike would change—would have to change—under varying climatic regimes. As Webster and Holland have put it, without understanding how hurricanes fit into the climate system or whether there’s some type of trade-off between storm frequencies and storm intensities, “predicting the future characteristics of hurricanes in a warming world is merely statistical extrapolation.”
At last, then, hurricane climatology may offer a way of integrating two fields of research that have remained at odds for too long. Hurricanes—unwisely ignored for many years by most climate scientists and meteorological dynamicists and taken up instead by a group of tropical meteorologists, many of whom didn’t trust global warming—were finally being set into their grand climatic context.
In the fullest sense, the storms were being made part of the world.
In late 2006, Bill Gray, man of the Rockies, could be found hanging out in the swamps of Washington, D.C., a lot.
First, in October, the lifelong Democrat gave a talk at the Capitol Hill Club—also known as the “National Republican Club of Capitol Hill”—a predictably glitzy place with oil paintings of George H. W. Bush and Ronald Reagan on the walls, and a huge blown-up photograph of a grinning W in the lobby. Behind a podium adorned with an elephant, in a room whose walls boasted still more paintings of great Republicans (Eisenhower and environmentalist Teddy Roosevelt this time), Gray discussed the 2006 hurricane year, his busted forecast (“we didn’t do so well this season”), and of course, global warming. The talk was sponsored by the George C. Marshall Institute, a conservative think tank that had been undermining global warming con cerns for over a decade, and that has been partly funded in recent years by ExxonMobil.
Despite his professed financial independence from fossil fuel interests, Gray has no problem doing events with industry-supported think tanks. As he sees it, the global warmers—especially the high-tech modelers with their expensive computers—get so much government research funding that this is just a way of evening out the ledger (though he says he doesn’t accept direct industry payments). And to be fair, despite the many special interests circling the climate debate like sharks, it’s impossible to believe Gray has in any sense been bought off. Clearly, his scientific conclusions about global warming spring from his particular empiricist philosophy and the course his career has taken, not from any sort of quid pro quo. Still, the help he gets in disseminating his arguments isn’t necessarily disinterested.
At least by Gray’s usual standards, the Marshall Institute talk didn’t seem to go over very well. No one kept him to time, so he just kept on going for at least an hour as the lunchtime audience steadily dwindled. Many people had difficulty hearing him, because Gray kept lowering the hand-held microphone away from his mouth, sometimes all the way down to his waist, or even holding it behind his back. Later, he started trying to stuff the mike into his blazer breast pocket to free his hands. But it kept drooping, and once tumbled all the way to a floor with a loud crash. Gray also messed up the slide show. “I get worked up and press the wrong button,” he said.
He had added some new content to his talk this time—theological content. One slide discussed “The Ascendancy of the Religion of Numerical Modeling and the loss of Meteorological Judgment and Reality.” “I’m an older guy,” Gray explained. “But when the computer came along . . . the younger people started to build models.” Then came a cartoon depicting the “Climate Model Department” of the Oracle at Delphi, with stick-figure modelers bowing before a computer framed amid Greek columns.
“We prostrate ourselves before our all knowing GOD,” said the scientific supplicants. “We humbly accept your GLOBAL WARMING judgment.”
Back in Colorado a few weeks after the Marshall Institute speech, Gray unsurprisingly got into a spat with Kevin Trenberth at a workshop on the subject of climate diagnostics and prediction. The Rocky Mountain News was there watching, eating it up:
Colorado State University’s William Gray, one of the nation’s preeminent hurricane forecasters, called noted Boulder climate researcher Kevin Trenberth an opportunist and a Svengali who “sold his soul to the devil to get (global warming) research funding.”
Trenberth countered that Gray is not a credible scientist.
“Not any more. He was at one time, but he’s not any more,” Trenberth said of Gray. . . .
Then, on November 7, 2006, the Democrats swept back into control of Congress. A week later, there was Gray—the secular scientist who didn’t go to church, who’d accused climate modelers and even his own student Holland of having “come to religion,” of believing on faith rather than evidence—standing beside Republican James Inhofe at a press conference on Capitol Hill. In addition to being a global warming denier, Inhofe is a right-wing evangelical Christian who has stated on the Senate floor:
I believe very strongly that we ought to support Israel; that it has a right to the land. This is the most important reason: Because God said so. As I said a minute ago, look it up in the book of Genesis . . . This is not a political battle at all. It is a contest over whether or not the word of God is true.
At the event with Gray, Inhofe declared that even though the Senate and House of Representatives had changed hands, “our government is not going to embrace economy-killing carbon caps next Congress.” He pledged to fight to kill them. As for Gray and the two other scientists who joined him, Inhofe offered them as proof that “climate skepticism—or evidence-based science—is alive and well.”
And then Gray did his routine again—the water-vapor feedback was wrong, the thermohaline circulation controlled everything, the models were worthless. Cooling would come again soon. He was joined on the occasion by meteorologist Joe D’Aleo, who had co-founded the Weather Channel and also questioned the scientific consensus on global warming. As part of his presentation, D’Aleo flashed a slide declaring, “Only Constant in Nature is Change.” The presentation added that “a great many climate scientists who work with the actual data see natural cycles at work.”
It was all getting a little old by now.
Inhofe had made a stand with a few scientists backing him, but it was increasingly clear that he—and they—were the losers now. Soon Senator Barbara Boxer, who had given Gray some “real hell” of his own on the Senate floor a year earlier, would take control of what had been Inhofe’s committee. Meanwhile, the UN’s Intergovernmental Panel on Climate Change would, in its soon-to-be-released Fourth Assessment Report, attribute a greater than 90 percent certainty to the conclusion that human activities were driving the recent global warming trend—and even the Bush administration would start pretending that it had always accepted this scientific conclusion.
In short, although the world was changing, Gray hadn’t. Whereas Emanuel had modified his view on global hurricane intensity trends in the face of new evidence, Gray—never reluctant to admit when he’d busted a forecast—couldn’t seem to give any ground on global warming. Here was a man who never wanted to stop talking and arguing—and so he didn’t. But he didn’t seem to realize that his own words could hurt him.
Still, I’d come to admire Gray. After seeing him speak in locations across the country, having long talks with him about the history of hurricane research, and experiencing the occasional ribbing from him myself, I’d developed a liking for a man who, in his late seventies, had much more life to him than some people ever do, and could still overwhelm those around him by his sheer presence. Even as I knew I could never agree with Gray, I recognized that on some level I wanted him for my own mentor. I envied the scientists who’d had the fortune of studying under him.
That’s what made it so hard to draw the line that had to be drawn.
No matter how much I might like Gray—or want to hang out with him and hear his jokes and stories—I couldn’t recommend his view of the science of global warming to the public, or to the people in power who make decisions on behalf of us all. There’s just too much at stake, and too little support for Gray’s views among the broader scientific community.
For despite Gray’s and Michael Crichton’s sneering at scientific “consensus,” it’s really all we have—we laypersons, we journalists, we politicians—to go on. We watch scientists battle, and no matter how much of their debates we think we understand, if we’re honest we know they’re always a little bit ahead of us, knowing a little bit (or a lot) more. We can’t presume to reliably guess which scientist is right and which is wrong as it all unfolds in real time. That would be the height of arrogance and foolishness. We can’t pick winners—not unless the broader scientific process, in which they all participate, pulls them (or the bulk of them) together in a conclusion they strongly and collectively accept. On global warming itself, that has happened already. On global warming and hurricanes, it hasn’t yet.
When it comes to this critical question of determining what science to trust if you’re not a scientist yourself, Peter Webster likes to cite the philosopher Bertrand Russell:
The scepticism that I advocate amounts only to this: (1) that when the experts are agreed, the opposite opinion cannot be held to be certain; (2) that when they are not agreed, no opinion can be regarded as certain by a non-expert; and (3) that when they all hold that no sufficient grounds for a positive opinion exist, the ordinary man would do well to suspend his judgment.
Russell added, “These propositions may seem mild, yet, if accepted, they would absolutely revolutionize human life.”
Implicit in Russell’s pithy statement is the principle that even when the “experts are agreed,” it remains wholly possible that their consensus conclusion will turn out to be entirely wrong. It might, at any time, be overturned by other scientists who successfully initiate a true paradigm shift. Unless and until that happens, though, the “consensus” represents, better than anything else, the most fully developed scientific understanding that humanity possesses at a given point in time. It’s synonymous with knowledge itself, as best we can discern it.