The Truth About Global Warming

For the past five years, Richard Lindzen and his wife have summered in Paris, always staying with family or borrowing an empty apartment from a friend. This year, however, Lindzen decided to splurge. His wife found a modest but airy flat on a noisy street near the Cimetiere du Pere Lachaise. The neighborhood is not the most fashionable, but it has other qualities. When outraged citizens declared their independence from France after the war with Prussia in 1871 and the government sent in the Army to quell the rabble-rousers, the last of them held out in Belleville, a few blocks east of Lindzen's flat. This same district of Paris, he points out, also includes the Bastille. "I think it's safe to say that this area has had more than its share of defiance," he says.

Lindzen doesn't seem capable of rabble-rousing. Sitting on his sofa in black-stockinged feet, he looks like a shorter, nerdier Orson Welles. He became a meteorologist back in the 1960s, when it was a backwater among the sciences. Little did he know how fashionable a weatherman could become. These days the highest levels of government consult meteorologists and other "climatologists" on one of the most urgent issues of the day, global warming. If you believe that science is a polite, orderly march to the truth, you will be surprised at how sharp the disagreements are, and at the magnitude of Dick Lindzen's defiance.

When climate scientists got on board the global-warming movement in the late 1980s, Lindzen remained steadfastly on the fringe. Back then he took issue with the notion that the earth is headed for catastrophe, and nothing has happened in a decade of climate research to convince him otherwise. With the Kyoto plan to reduce carbon-dioxide emissions effectively dead and environmentalists up in arms, Lindzen, Alfred P. Sloan Professor of Meteorology at the Massachusetts Institute of Technology, has become the most well-respected voice of dissent. Colleagues praise his scientific work and do not assign political motives. And yet his scientific views have led him, a Democrat, into the lonely position of defending George W. Bush's Kyoto stance. "Bush is guilty of nothing more than being honest," he says. "There's no current Western leader who's as well informed on the issue as Bush, as strange as that may seem. European politicians are just using Kyoto for cheap virtue." Lindzen was one of a handful of authors of a recent study requested by the White House. After Bush's Kyoto about-face, Lindzen was summoned to Pennsylvania Avenue. Even if you accept the doomsday forecasts, he told Bush, Kyoto would hardly touch the rise in temperatures. "Kyoto would be to do nothing at great expense," he says.

Lindzen is not a complete skeptic. He acknowledges that the earth is getting warmer, and that human activity might have something to do with it. Over the past century, cars and factories have released carbon dioxide and other greenhouse gases into the air, trapping the sun's energy and warming the atmosphere. The key question is, how warm will it get? Lindzen doesn't think scientists have a very good handle at all on how the earth's atmosphere will respond to increased levels of carbon dioxide. He doesn't think much of the half-dozen or so gigantic computer programs, or models, that simulate what the earth's climate will be like 100 years from now--and form the basis of all the predictions of doom. Whereas most models predict a warming of 3 or 4 degrees centigrade in the next 100 years, Lindzen's calculations show less than 1 degree, a figure that makes Kyoto seem downright hysterical. Most climate scientists, it's fair to say, disagree. They stick by their models, despite the flaws. "It's easy for Lindzen to criticize," says one. "But he's a theorist, not a modeler. He points out errors, but he's not the one who necessarily has to correct them." Annoying as he may be, his defiance serves as a reminder that climate scientists, despite their newfound relevance to policy and public renown, are still grappling with huge gaps in their knowledge.

Lindzen may raise his colleagues' hackles by criticizing their science, but when it comes to politics, he strikes a chord. Last week the Independent, the British newspaper, summarized the report of the Intergovernmental Panel on Climate Change (IPCC), a United Nations-sponsored group: "Global warming is happening now, caused by human actions, and threatens the Earth with disaster, the world's leading atmospheric scientists insisted yesterday." This is news to Lindzen, who literally is one of those scientists. He was coauthor of the IPCC report, but did not participate in writing the widely cited "summary for policymakers." "The 'consensus of scientists' is a very weird thing," he says. "The summary is written by 14 of the hundreds of scientists that contributed. Is that a consensus? I don't think so." Many scientists agree that the IPCC, in its zeal to build the case for doing something about global warming, plays fast and loose with the science, glossing over uncertainty and pushing its conclusions too far.

Lindzen clearly relishes the role of naysayer. He'll even expound on how weakly lung cancer is linked to cigarette smoking. He speaks in full, impeccably logical paragraphs, and he punctuates his measured cadences with thoughtful drags on a cigarette. His parents arrived in the United States from Germany in 1938, two years before his birth. His father, a bootmaker, worked in a shoe factory in Massachusetts but eventually moved his family to the Bronx in New York City to live in a Jewish community. Lindzen won a scholarship to Rensselaer Polytechnic Institute and tranferred to Harvard a year later. An interest in ham radio piqued his curiosity about how the atmosphere affects radio waves, and this led him to meteorology.

Lindzen's contrarian attitude about global warming first stirred in 1988. In the heat of an atypically hot summer in the United States, Sen. Al Gore held hearings in which prominent scientists raised fears of rapid warming. The IPCC was formed to assess the need for action. "I wrote a piece for the Bulletin of the American Meteorological Society saying that perhaps we should go easy on this because the case wasn't strong," Lindzen recalls. "I got people telling me that perhaps, as a Democrat, I shouldn't say that." In 1989 he spoke to an Earth Day gathering at Tufts University. "I was put down immediately," he says. "Scientists can have doubts, but environmentalists can't."

In the early 1990s Lindzen was asked to contribute to the IPCC's 1995 report. At the time, he held (and still does) that untangling human influences from the natural variation of the global climate is next to impossible. When the report's summary came out, he was dismayed to read its conclusion: "The balance of evidence suggests that there is a discernible human influence on global climate." "That struck me as bizarre," he says. "Because without saying how much the effect was, the statement had no meaning. If it was discernible and very small, for instance, it would be no problem." Environmentalist Bill McKibbon referred to this phrase in an article in The Atlantic in May 1998: "The panel's 2,000 scientists, from every corner of the globe, summed up their findings in this dry but historic bit of understatement." In an angry letter, Lindzen wrote that the full report "takes great pains to point out that the statement has no implications for the magnitude of the effect, is dependent on the [dubious] assumption that natural variability obtained from [computer] models is the same as that in nature, and, even with these caveats, is largely a subjective matter."

This statement contains the crux of Lindzen's beef with the global-warming establishment. What is the relationship between nature, on the one hand, and the gigantic computer models that churn out climate predictions for 100 years hence? "In the scientific methodology," he says, "simulation is the weakest link. To say you've simulated something is to say very little." To appreciate why requires a brief foray into the world of climate science.

When it comes to meteorology, data can be very iffy. The United Nations specifies that thermometer readings in harsh polar climates, for instance, should be taken in a shelter that is freshly painted, of a specified height, ventilated in a certain way and so forth. When the Soviet Union fell and Siberian data collectors stopped being paid, did they continue to maintain the shelters? In the oceans, sometimes data collectors take the temperature of water drawn in a bucket over the side of a ship. Other times they put their thermometers in the water that enters the ship's engine intakes. Such inconsistent practices may have something to do with why observations show a warming at the North Pole but not at the South, while some areas even seem to be cooling. The overall warming trend of 0.6 degrees centigrade in the past 100 years is just discernible above these messy readings. "The observations are not great, but there's a consistency in the trend," Lindzen says.

Back in the 1980s, climate models were very crude simulations of the greenhouse effect. The main test of a climate model is to start sometime in the past and "predict" the present, with all the temperature swings and ice ages and so forth in between. When scientists tried this out on their early models, they got silly results, such as severe ice ages occurring in the 20th century. To avoid this kind of "drift," scientists applied a sort of fudge factor to ensure a sensible outcome. This doesn't do much good when it comes to predicting the future, which may be why 1988 predictions of rapid warming by 2000 never panned out. The average temperature hasn't climbed at all.

In recent years climate scientists have added a great deal of complexity to their models in the hope of capturing the essential behavior of the earth's climate. They have tried to account for clouds, water vapor, ocean currents, dust particles in the air (aerosols), sea ice and variations in ground cover. They have coupled the oceans to the atmosphere so that changes in one affect the other, and vice versa. Only recently have the better models, such as that of the Hadley Centre in Britain, abandoned the practice of fudging.

The change adds to the models' credibility, but does it mean they are reliable in predicting the future? It doesn't, Lindzen argues. For one thing, added complexity does not ensure that the models reflect what nature is doing. Take the case of aerosols--dust and other particles in the atmosphere. Scientists realized only a few years ago that aerosols reflect light and may exert a cooling influence; their effects are poorly understood. Putting them in climate models is essentially the same thing as adding a fudge factor. "There are no records of aerosol production before the 1960s," Lindzen says. "So you have complete freedom to adjust the amount of aerosols to make the models replicate the temperature record."

Aerosols are small potatoes when you consider the effects of clouds and water vapor. Water vapor is a far more powerful greenhouse gas than carbon dioxide--a change of a few percentage points in the atmosphere's humidity could wipe out, or amplify, the effects of a rise in carbon dioxide. Even a doubling of carbon dioxide from preindustrial levels (which is expected to happen in 100 years if no effort is made to reduce carbon emissions) would probably, by itself, increase temperature only about 1 degree centigrade by the end of the century--warmer, to be sure, but probably short of doomsday. True catastrophe would require a helping hand from water vapor. That's exactly what most models depict.

But here's the rub: water vapor is not well understood. Models, for instance, assume that a warmer atmosphere would hold more water vapor, but it wouldn't necessarily, says Lindzen. Another wild card is the role of clouds in regulating humidity. Cumulus clouds draw moist air from the surface and carry it skyward. Some of the moisture falls back to the ground as rain, and what's left over is taken high up in the atmosphere, where it freezes into cirrus clouds. These clouds drift hundreds of miles raining ice particles into the lower atmosphere; these evaporate and raise humidity. But how much? Lindzen asserts that as the atmosphere warms, cumulus clouds will produce rain more efficiently, thereby leaving less for humidity-causing cirrus clouds. The result would be drier air. Rather than amplifying the greenhouse effect of carbon dioxide, this would counteract it.

Even if scientists understood climate perfectly, the models would still contain another type of error inherent in the way computers do the calculations. In an ideal world, models would account for everything, down to each molecule of water. In practice, compromises are made. The Hadley Centre's model, for instance, dices the atmosphere into 250-kilometer squares, and then crunches equations that describe scientists' best approximation of the atmosphere's aggregate behavior. Making the squares smaller would reduce error, but it's expensive: shrink the squares to 125km, and the calculation balloons 16-fold. Even so, much of what goes on at the scale of clouds is lost.

Modelers concede both types of uncertainty but insist that their predictions are still valid. "There are many things we're uncertain about in climate modeling," says David Griggs, director of climate research at Hadley. "But there are a lot of things we can say with confidence. Our estimates take all of these uncertainties into account." The IPCC report agrees: "Confidence in the ability of models to project future climate has increased." Nonsense, says Lindzen. "The argument that the models are continu-ally improving is a kind of motherhood statement that international reports al-ways make. But there's no evidence of that."

Another way of estimating how much the climate will warm is a matter of dispute. By looking at events that disrupt climate and measuring the amount of time it takes for temperatures to change in response, scientists can calculate how sensitive the global climate might be to a change in carbon dioxide. When Mount Pinatubo erupted in 1991, for instance, it spewed ash into the atmosphere, which reflected sunlight and caused a discernible cooling across the globe. Lindzen studied volcanic eruptions and found that cooling tends to kick in pretty quickly, which suggests that the climate is relatively insensitive to disruptions. From this he concludes that a doubling of carbon-dioxide levels would lead to a warming of less than 1 degree centigrade.

Case closed? Hardly. James Hansen, a climate scientist at the Goddard Institute for Space Studies in New York City, has studied the end of the most recent ice age, when temperatures rose to the level they've more or less maintained for the last 10,000 years. (The data come from ice-core samples taken in Antarctica and Greenland, an approximate record of past climate change.) He found a sensitivity consistent with a warming of 3 or 4 degrees centigrade, which jibes with current models. "Dick's idea that climate sensitivity is low is simply wrong," says Hansen. "The history of the earth proves him wrong."

In the face of such disagreement, it is difficult--for scientists and nonscientists alike--to decide who is right. Should Lindzen be discounted as some lunatic on the fringe? Or is it foolish to wish too hard for a consensus? Perhaps what's needed is a dispassionate look at the research. This is a big part of what Hans-Joachim Schellnhuber does. As director of the Potsdam Institute for Climate Studies in Germany, where he oversees the work of oceanographers, meteorologists, mathematicians and biologists, he is a practiced synthesizer of disparate scientific specialties.

Schellnhuber acknowledges the difficulty of interpreting the IPCC's temperature-increase predictions for the end of the century, which range from 1.4 degrees centigrade to 5.8 degrees. "There is a certain arbitrariness," he says. "Two Japanese models, one showing a 9-degree warming and the other showing zero warming, were thrown out because they were felt to be too far outside the range. So you take all these models and average them out, and you get a 3- or 4-degree warming. What does it mean?" He shrugs. "If one model is operating on wrong principles, all of them are off."

In light of the uncertainty, Schellnhuber takes a very European view of climate policy. He favors cutting emissions, a la Kyoto, just in case the pessimistic majority is correct. He believes in consensus. "Science really comes down in the end to the scientists," he says. "You have to make your best judgment." What does he make of Lindzen? "People like him are very useful in finding the weak links in our thinking," says Schellnhuber. It may take many years to sort out just where those weak links are. But it's worth being reminded that the answers will come in their own time, no matter how badly the world wants them now.

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