The Storm at the Center of Climate Science

How did a quiet researcher on global warming upset so many people?

By RICHARD MONASTERSKY

James Hansen is tired of being one of the most misunderstood scientists on earth. The climate researcher who almost single-handedly drew attention to the global-warming issue, Mr. Hansen has recently started feeling the heat himself, but not because of the weather.

Instead, he's gotten quietly steamed as a flurry of press reports have

ALSO SEE: Colloquy Live: Join a live debate on global warming with James Hansen, director of the National Aeronautics and Space Administration's Goddard Institute for Space Studies, Thursday, November 9 at 1 p.m. U.S. Eastern time

claimed that he renounced his views concerning the need to curb carbon-dioxide pollution, something he had advocated in the past.

Yet, in the wake of the ruckus, it is apparent that reporters, environmentalists, lobbyists, scientists, and politicians -- including Gov. George W. Bush of Texas -- have all misinterpreted his recent work.

The question of what this prominent government scientist said in a recent paper has widespread repercussions, ranging from the presidential election to international negotiations culminating this week on how to carry out the global climate treaty called the Kyoto Protocol. Indeed, at a U.S. Senate hearing in late September, Sen. Chuck Hagel, a Nebraska Republican and a leading critic of the treaty, raised Mr. Hansen's work as one of the prime reasons for reconsidering the international agreement, which binds industrialized nations to cut emissions of greenhouse gases.

"Some of the earliest and strongest advocates of global warming have now revised their conclusions," said Senator Hagel, who later added that "just last month, Dr. Hansen issued a new analysis which said the emphasis on carbon dioxide may have been misplaced."

Meanwhile, environmentalists who once stood side-by-side with Mr. Hansen are wringing their hands. "His goal I think was to be helpful to the debate," says Daniel F. Becker of the Sierra Club. "What he's ended up doing is inadvertently creating a controversy which those hostile to any action are using to fuzzy up the debate."

In the aftermath of Mr. Hansen's bombshell, leaders of the United Nations' Intergovernmental Panel on Climate Change publicly criticized his paper as well, saying it could easily be misinterpreted.

Just how did this soft-spoken scientist from Iowa get himself into such a political pickle? Mr. Hansen's tribulations reveal how stormy the issue of climate change has grown and how dangerous it is for researchers to enter the policy arena. At the same time, it shows how ambiguous statements and political naivete can get even the most seasoned scientist into hot water.

At his office overlooking Broadway in New York City, Mr. Hansen was struggling last month to clear the air of all the smoke that had blown his way since August, when the Proceedings of the National Academy of Sciences published his most recent paper on climate change. With thinning, untamed hair and bleary blue eyes, Mr. Hansen was trying to decide how to get his real message out. He eventually circulated an open letter to scientists.

A member of the National Academy of Sciences, Mr. Hansen is director of the National Aeronautics and Space Administration's Goddard Institute for Space Studies, a relatively small outpost of federal scientists just south of Columbia University, which owns the building and is affiliated with the center. The building's only distinguishing characteristic is its lowest floor, occupied by Tom's Restaurant, made famous as the hangout on Seinfeld.

The atmosphere in Mr. Hansen's corner office seems a world removed from the cynical wit of that sitcom. The scientist, now 59 years old, came to the institute in 1969, shortly after obtaining his doctorate in physics from the University of Iowa. The son of a farmer-turned-bartender in Denison, Iowa -- the hometown of Donna Reed -- Mr. Hansen has not lost his slow, deliberate cadence, or his don't-speak-ill-of-your-neighbor reticence, in all his years in Manhattan. When he criticizes or complains, he doesn't come close to a New Yorker's sneer. The strongest he's willing to dish out is: "A lot of the interpretations of our paper have not been very accurate. The attempts to correct those inaccuracies have not been very successful."

Despite his laconic personality, Mr. Hansen is not new to the media spotlight. He first warned the nation about the dangers of global warming in 1982, when he testified at a Congressional hearing cochaired by a young representative named Al Gore Jr. Six years later, Mr. Hansen captured even more attention when he told a Senate committee that "the greenhouse effect has been detected, and it is changing our climate now."

Mr. Hansen's comments might as well have been lighter fluid. On the day of that June hearing, Washington, D.C., was baking in a heat wave, a drought was withering crops in the Midwest, and unstoppable wildfires in the United States were on their way to scorching millions of acres, including sections of Yellowstone National Park.

At the time, other scientists suspected that Mr. Hansen was correct, but they lacked his certainty. Mr. Hansen became the darling of environmental activists and helped sear the issue of greenhouse-gas pollution into the public consciousness. By 1995, the United Nations' climate-change panel had issued a report backed by thousands of scientists that reached essentially the same conclusion as Mr. Hansen.

It was that history that made everybody take notice when Mr. Hansen and his colleagues published a paper this summer called "Global Warming in the Twenty-first Century: An Alternative Scenario." Most reporters and pundits decided that the scientist had shed his green skin.

"Mr. Hansen has changed his mind. In a paper published by the National Academy of Science [sic], he now says he was wrong," crowed an editorial in the Vancouver Sun that questioned concern over greenhouse-gas pollution.

Yet the real story was never that sexy, a point that eluded even The New York Times and the journal Nature, both of which reported that Mr. Hansen was shifting attention away from controlling carbon-dioxide emissions.

Like some enigmatic poem, the NASA paper requires close reading to tease out its true message. Written entirely by Mr. Hansen, who relied on his colleagues' calculations, the report makes its key point at the end of the introduction: "We suggest that it is more practical to slow global warming than is sometimes assumed."

Expanding on that theme at his office, Mr. Hansen says that his scenario is more hopeful than the dour projections filling the United Nations panel's reports and included in most discussions of the Kyoto Protocol. "These make you very discouraged because you end up concluding: Well, gee, it's very hard to get people to agree to Kyoto, and [other scientists] say it's going to reduce the warming only a small percentage," says Mr. Hansen. "I think of the alternative scenario as being more optimistic, and I think it's a plausible scenario."

To back up that premise, he looked at the problem from a banker's perspective, tallying up the factors altering the climate.

Mr. Hansen notes that many types of pollution drive earth's temperature upward, exerting what scientists call "positive forcings." Carbon-dioxide emissions are the biggest single forcing, accounting for about half of the warming power exerted by humans since the start of the Industrial Revolution. The buildup of that gas has added 1.2 watts -- about one and a half Christmas-tree light bulbs -- of heating to each square yard of the planet's surface. The other half of the warming power comes from emissions of methane (natural gas), chlorofluorocarbons (used in older air conditioners and formerly in spray cans), tropospheric ozone (smog), and nitrous oxide (from changes in land usage).

On the other side of the equation, factors called "negative forcings" are working to cool the climate. The combustion of fossil fuels prompts the growth of tiny sulfuric-acid particles that reflect sunlight back into space and thereby shade the earth. Scientists have yet to determine how strong those so-called aerosols are at cooling, but they may have just about the same strength as the carbon-dioxide forcing, about 1.2 watts per square yard.

Mr. Hansen argues that positive forcing from carbon dioxide and negative forcing from sulfate aerosols approximately cancel each other out. What's left are the other greenhouse gases, which he calculates have played the dominant role in warming the globe in recent decades.

That argument prompted a chorus of I-told-you-so's from greenhouse contrarians, who have long maintained that carbon dioxide is not a problem. But many climate scientists countered that the paper could just as easily have switched the argument, by having the lesser gases balance the aerosol forcing, leaving carbon dioxide the main source of trouble.

Tom M.L. Wigley, a climate scientist at the National Center for Atmospheric Research, in Boulder, Colo., calls Mr. Hansen's way of accounting "a con trick that I don't particularly like." He acknowledges that there may be some logic to grouping carbon dioxide and aerosols, because both come from the combustion of fossil fuels, but then again, so does ozone smog. "It's oversimplifying the issue to do it the way he's done it."

What's more, the positive and negative forcings don't truly balance out, say many scientists. Carbon-dioxide molecules, once they puff out of a tailpipe or a smokestack, survive in the atmosphere for a century or more, on average, spreading around the globe in a relatively even distribution. But aerosols last only a few days or weeks before they drop from the sky, so they concentrate near where they were emitted. In short, while the warming from carbon dioxide affects the entire globe, the shading from aerosols happens only downwind of their sources. "There's no way they can cancel out," says Donald J. Wuebbles, chairman of the atmospheric-sciences department at the University of Illinois at Urbana-Champaign.

Criticism also comes from those who dispute predictions of significant warming, such as Patrick Michaels, a professor of environmental science at the University of Virginia. He argues that Mr. Hansen has overestimated the strength of aerosol cooling. "This is not science, it's philosophy," he says, referring to the aerosol issue.

Mr. Hansen acknowledges that he could have grouped the forcings differently, balancing aerosols against other greenhouse gases instead of against carbon dioxide. "You can do it either way. I thought it was an interesting point to make. It got some attention, didn't it? That's part of the point," he says with a mischievous chuckle. "I think in the end it is probably useful. Even though it requires these clarifications, it's forcing people to think."

In that response lurks the curious split personality of the scientist. Although unassuming in person and careful in his speech, Mr. Hansen has a habit of making his quiet voice heard around the world when he has something important to say.

"This latest paper is consistent," says Rafe Pomerance, former assistant secretary of state for environment and development, who helped negotiate the Kyoto Protocol. "He always tries to look at things a little differently and to provide interesting ways to think about the problem."

In his recent paper, Mr. Hansen drew the fiercest fire for his vision of how the world might change over the next half-century. Having implicated forcings other than carbon dioxide as the drivers of global warming, he says that those less-famous gases are now accumulating in the atmosphere at a slower rate than they were in previous decades. So Mr. Hansen proposes a scenario for the future that builds on the recent success. Nations could curtail the atmospheric buildup of those factors, he contends, keeping the non-carbon dioxide forcings from getting any worse in the next 50 years than they are today.

Right now, nations are emitting too much of those gases to keep their atmospheric concentrations stable. Achieving those targets would mean cutting emissions of methane from rice fields, landfills, and the intestinal tracts of livestock. It would mean curbing soot -- made up of black specks of carbon -- belched out by diesel trucks and power plants. It would mean reining in ozone smog that threatens human health and crops. Such actions "could lead to a decline in the rate of global warming, reducing the danger of dramatic climate change," he says in his paper.

In the past, developed and developing countries have bickered about who should take the first step in curbing greenhouse gases, but Mr. Hansen says that his suggestions should appeal to both because they would produce immediate and tangible results, reducing air pollution that directly harms people and making livestock and rice production more efficient. "What we're saying should be more attractive to all parties," says Mr. Hansen.

News stories portrayed him as arguing against the need to limit carbon-dioxide emissions. According to The Guardian, in Britain, Mr. Hansen and his colleagues "urge the world's governments radically to re-think climate change strategy. They claim that the emphasis on carbon dioxide (CO₂) may have been misplaced."

Those opposed to the Kyoto Protocol seized on that point. "This is one of the most significant scientific reports since the Kyoto Protocol was negotiated," Nebraska's Senator Hagel told a conference at Rice University in early September.

The paper even made its way, obliquely, into the second presidential debate, when Mr. Bush said, "I think there's been some -- some of the scientists, I believe, Mr. Vice President, haven't they been changing their opinion a little on global warming? A profound scientist recently made a different, different ..." Mr. Bush's sentence was cut off by the moderator, but the candidate seemed ready to discuss Mr. Hansen's work, says a campaign spokesman, Ray Sullivan.

Despite such reactions, Mr. Hansen has not actually let nations off the hook. Buried in his paper's scenario is the stipulation that the world keep carbon-dioxide emissions constant at today's levels, and probably even reduce them by 2050.

"You could argue that Jim had his little poison pill in the paper, but nobody noticed it," says Jerry D. Mahlman, a professor of oceanic and atmospheric sciences at Princeton University.

He and many other scientists view Mr. Hansen's carbon-dioxide scenario as quite stringent and one requiring significant government action, especially given the projections for population growth and industrialization around the world. "I think he's wrong there," says Mr. Wigley of the National Center for Atmospheric Research. "To meet his target would require a very substantial effort. It's wrong to imply even in a vague and indirect way that this is going to be easy to do."

Amid the news media's faulty reactions, even some scientists missed Mr. Hansen's point about carbon dioxide. "The paper is unclear. I didn't remember that being there," says Michael Oppenheimer, an atmospheric scientist who works for Environmental Defense and who appeared at the same Senate hearing in 1988.

Several scientists have blamed the confusion on the Proceedings of the National Academy of Sciences, which lets academy members submitting papers choose two scholars to review them. That contrasts with the practice at most other scientific journals, where editors select reviewers anonymously. "If it had been properly peer-reviewed, it wouldn't have appeared that way in the first place, and they would have corrected the way they were making their statements," says Mr. Wuebbles of Illinois.

Mr. Hansen, though, defends the practice of the Proceedings. "It allows academy members to say something which might not be popular, but it still is refereed."

What would have happened if he had sent the paper to a different journal? "It might have gotten less attention," says Mr. Hansen.

He argues that most scientists have taken too pessimistic a view of the future and have failed to note that carbon dioxide has accumulated much more slowly than the U.N. panel anticipated a decade ago. The real world, in short, has not followed the predicted track in the past, which calls into question scenarios projecting large future increases in emissions. "In fact, in the last two years, the amount of carbon-dioxide emissions declined slightly," he says, although he notes that the economic crisis in Asia may have played a role in that trend.

In keeping with his optimistic outlook, Mr. Hansen wants to call attention to the progress made in recent years. "It's important to stick your head out the window every once in a while when you're trying to do forecasting."

But sticking your head out, especially in the war zone surrounding the climate-change debate, raises the risk of of decapitation.

One of those gunning for Mr. Hansen is George M. Woodwell, an ecologist and director of the Woods Hole Research Center, who tore into the Proceedings paper in an opinion piece in The Christian Science Monitor. "My conclusion is that the paper was a mistake and not a constructive contribution," Mr. Woodwell said later in an interview with The Chronicle.

He and others note that the Kyoto Protocol already takes a broad approach, looking beyond carbon dioxide. The treaty requires industrialized nations by 2012 to reduce combined emissions from six greenhouse gases to 5 percent below their 1990 levels. Mr. Hansen responds that the treaty doesn't cover smog and soot, two major warmers in his calculations.

Even as critics have attacked Mr. Hansen over his recent paper, however, they have praised his scientific contributions. "Jim Hansen has done magnificent work. Without any question," Mr. Woodwell says.

Mr. Mahlman of Princeton calls Mr. Hansen an "ethnic scientist," shaped by the culture and discipline of the profession. As such, he doesn't shy away from making controversial statements if that's where the evidence leads him. "That's the part that isn't understood about Jim. He's still trying to figure out how Mother Nature works. It's an ethnic thing. It's just part of our culture to pursue the truth and go where it takes us."

Yet some accuse Mr. Hansen of following that path into an arena outside his expertise, where he underestimated the difficulty of achieving the strict emissions limits required by his scenario. "Most of the critiques that I've heard from colleagues on the policy side are that from a policy perspective, [Mr. Hansen's] paper is a fairly naive one," says Mr. Mahlman.

That starry-eyed nature comes out when Mr. Hansen describes why his prescription should go down much easier than previous strategies for moderating global warming. "It's a common-sense approach to reducing greenhouse-gas emissions which everyone could agree to because of the multiple benefits for doing it. I really think it should be nonpartisan," he says. As for the politics, he says, "this shouldn't be such an adversarial issue between conservative people and liberal people."

Yet when he offers ways to control emissions, say by increasing automobile efficiency, he wades into the roiling waters of a political tempest, where automakers and environmentalists have been battling for years. "It does require that the sport-utility-vehicle path -- with great inefficiencies in going to the grocery store -- is not going to work. We will have to make some changes. The government probably has to be involved. You're going to have to have some regulation," he says, as if such rules had not spawned decades of debate.

Mr. Hansen brushes aside the issue of naivete, saying that science will prevail in the end. "What we need on some of these issues is really hard science, and then coming to a common agreement becomes a lot easier. It's not that somebody who has an economic interest won't continue to object, but if the scientific evidence becomes sufficiently overwhelming, then you can overcome the self-interests of some parties."

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