Editor's note: This story was corrected to acknowledge that Al Gore's slide show used data from a hockey-stick study other than Michael Mann's, that Mann made all the data germane to the study available online, and that Mann's study data stopped at 1980.
One of the most impressive visuals in Al Gore's now famous slide show on global warming is a graph known as the "hockey stick." It shows temperatures in the Northern Hemisphere rising slowly for most of the last thousand years and turning steeply upward in the last half of the 20th century. As evidence of the alarming rate of global warming, it tells a simple and compelling story. That's one reason the U.N.'s Intergovernmental Panel on Climate Change included a similar graph in the summary of its 2001 report. But is it true?
The question occurred to Steven McIntyre when he opened his newspaper one morning in 2002 and there it was—the hockey stick. It was published with an article on the debate over whether Canada should ratify the Kyoto agreement to curb greenhouse-gas emissions. McIntyre had little knowledge of the intricate science of climate change; he didn't even have a Ph.D. He did have a passion for numbers, however. He also had some experience in the minerals business, where, he says, people tend to use hockey-stick graphs when they are trying to pull one over on you. "Reality usually isn't so tidy."
As every climate scientist must know by now, McIntyre's skepticism of the hockey stick launched him on a midlife career change: he has become the granddaddy of the global warming "denial" movement. McIntyre asserted that the data of Michael Mann, head of Penn State's Earth System Science Center, did not support his conclusions, and that a true graph of temperatures would suggest a cyclical cause of recent warming. Following in his footsteps, a cottage industry of amateur climatologists have dug into the climate literature, tried to poke holes in the arguments, and demanded supporting data from scientists, sometimes under the auspices of Freedom of Information Act requests.
The scientists have resisted these efforts just as fiercely. For the past six years the conflict has played out in blogs, in the halls of Congress, and in deliberations of the IPCC. It came to a crescendo with the theft of private e-mails from the University of East Anglia in England in November, which raised questions about the scientific objectivity of several prominent researchers, including Phil Jones, who resigned in December as head of the Climatic Research Unit.
The battle between "alarmists" and "deniers" has taken a huge toll, not just on the reputations of Jones and the other "climategate" scientists. It has also damaged the credibility of climate science itself, and threatened more than a decade of diplomatic efforts to engineer a global reduction in greenhouse-gas emissions. The effort, which has kept a forward momentum since the Kyoto meeting in 1997, came to a cold stop in Copenhagen in December. The conference was originally intended to bring the U.S. and China into a global agreement, but produced nothing of substance. Indeed, the climate project bears a striking resemblance to health-care reform in the United States—stalled by a combination of political resistance and hubris.
What went wrong? Part of the blame lies, of course, with those who obstructed the efforts of the IPCC and the individual scientists, including bloggers who tried to sandbag scientists with spurious FOIA requests, and the perpetrators (as yet unknown) of the hack at the Climatic Research Unit. Part of the blame also falls on the climate scientists themselves. Many of them—including perhaps Rajendra Pachauri, the IPCC head—may have stepped too far over the line from science to advocacy, undermining their own credibility. Some scientists, as a result, are now calling for a change in tone from antagonism to reconciliation. Climate science, they say, needs to open its books and be more tolerant of scrutiny from the outside. Its institutions—notably the IPCC—need to go about their business with greater transparency. "The circle-the-wagons mentality has backfired," says Judith Curry, head of Georgia Tech's School of Earth and Atmospheric Sciences.
The first thing to fix is the institution that has borne the brunt of the recent public-relations disaster: the IPCC itself. Recently there have been several minor revelations of sloppiness. A line in the group's 2007 report stating that glaciers in the Himalayas will melt entirely by 2035 turns out to have come not from the peer-reviewed literature, but from a 1999 article in New Scientist, a popular magazine in the U.K. More damaging, IPCC chairman Pachauri has been acting as a consultant to financial institutions, including Deutsche Bank and Pegasus, an investment firm. Although he says he has donated the proceeds to the nonprofit organization he founded in Delhi to promote charitable programs in sustainability, many people have wondered whether the head of a scientific organization that calls itself "policy neutral" should be consulting with banks. Some have called for his resignation.
Other scientists have gone further than Pachauri in casting aside the appearance of impartiality. James Hansen—head of the NASA Goddard Institute for Space Studies and adjunct professor in the department of earth and environmental sciences at Columbia University—has unimpeachable scientific credentials. He was a pioneer in building computer simulations of climate and piecing together the temperature record. But in recent years he's become an unabashed advocate for draconian cuts in greenhouse gases, coming out against cap-and-trade—the preferred mechanism of the IPCC and its parent, the U.N. Framework Convention on Climate Change, to limit greenhouse--gas emissions by setting a ceiling and allowing countries to trade emissions credits. He has also gotten himself arrested while protesting mountaintop coal mining in West Virginia last summer. Has his and his colleagues' advocacy come at the expense of their scientific reputations? "Absolutely," says Hansen. "But what are we supposed to do? Tell our grandchildren to buzz off, that we don't give a darn about them?"
Climate science is losing ground with the public, at least in the U.S. In April 2008, 47 percent of Americans believed that human activity is the cause of climate change and 34 percent thought the warming was due to natural geological causes. According to the polling firm Rasmussen Reports, the numbers in recent months have flipped: the anthropogenic crowd dropped to 34 percent, and 47 percent now blame nature.
The hockey-stick saga is an example of why advocacy and hubris may have been the wrong reaction to the assault of McIntyre & Co. The original idea—conceived by Penn State's Mann while still a postdoctoral researcher—was to surmise temperatures, going back 1,000 years, from such data as the thickness of the rings of bristlecone pine trees, which grow faster in warm summers than in cool ones. The data that Mann had available only went as far as 1980. It also required some massaging of the data. This is not to say Mann was conspiring to deceive; the National Academy of Sciences gave this work a thumbs-up in a 2006 review. The troubles started after the results were published, when McIntyre began asking Mann for his data. McIntyre says Mann gave him raw data, but not the meta-data needed to make sense of them. Mann says, and the National Science Foundation confirmed, that he had already made the study's data available online. Some of the most damning passages in the climategate e-mails, however, involve some of the scientists discussing ways of fending off requests from McIntyre and other bloggers. Penn State recently cleared Mann of wrongdoing.
Rather than shun the amateurs, climate scientists might find that giving them access to their data goes a long way to building trust. It might even lead to better science. New Zealand computer programmer John Graham-Cumming found errors in temperature data of the U.K.'s Met Hadley research center that an official acknowledged early this month. "I'm not a climate skeptic," Graham-Cumming told The Times of London. "I think it's pretty sure that the world is warming up, but this does show why the raw data, and not just the results, should be available." That also jibes with Curry's personal experience. As coauthor of a 2005 paper arguing that the frequency of severe hurricanes has doubled in the past 30 years due to a warming climate, she felt the sting of criticism from bloggers who questioned her science and demanded to see her data. "I know what it's like to be attacked, and it isn't pleasant," she says. Unlike Jones and the other climategate scientists, however, Curry obliged her critics. She emerged from the experience chastened (they found mistakes), but also convinced that her fellow climate scientists are doing themselves and the public a disservice by ignoring bloggers and skeptics.
Another way to build trust might be to toughen up standards on the science itself. In an issue as intensely politicized as climate, where billions of dollars are riding on policy decisions based on the outcome of the next study, maintaining scientific objectivity cannot be easy. In particular, climate scientists are often doing what's known as meta-analyses, which are studies that draw together data from other studies. They could be more vulnerable to charges of bias.
Plans to cut greenhouse-gas emissions and institute cap-and-trade measures are now mired in politics and a poor global economy. In the U.S. the House cap-and-trade bill is almost certain to die in the Senate. The Obama administration will probably be able to push through measures to cut greenhouse-gas emissions, mainly through the EPA, but until jobs recover it isn't likely to press too hard toward the goal of 17 percent reductions by 2020. Any new initiatives on climate, say White House aides, are going to have to come as part of an energy bill that emphasizes the development of new green technologies, such as alternative forms of energy and energy-efficiency improvements. President Obama's $8 billion in loan guarantees for nuclear-power plants is a case in point.
The climate woes will make it harder for the West to push Beijing to curb emissions when the two sit down at the negotiation table in Cancún, Mexico, in December. China isn't likely to commit to any big cuts unless the U.S. agrees to follow suit. "To get a deal in Cancún, insofar as the Chinese see it, the first thing on the list is that the U.S. has to act," says William Chandler, an expert on China's energy policy at the Carnegie Endowment for International Peace. That's a new twist on the old standoff: one reason the U.S. never ratified Kyoto was because it let China and India off the hook.
That leaves the U.N. Framework Convention on Climate Change, which has focused climate talks almost exclusively on emissions cuts and cap-and-trade, with no viable program. What's needed is a Plan B: promoting new energy technologies, helping poor countries adapt to a warmer world, developing aerosols that could lower temperatures should warming go haywire. The resignation last week of Yvo de Boer, who led the U.N. organization through the Copenhagen talks, offers the opportunity for a fresh start.
Twenty years ago, before anybody outside a small circle of meteorologists cared about climate, Phil Jones completed a study that reads like a parody of dull science. Called "Assessment of Urbanization Effects in Time Series of Surface Air Temperature Over Land," it was essentially a look at thermometers around the world. Even Al Gore probably gave it a miss. For the past few months, however, tabloid headlines (climategate chaos and how climategate boss broke rules by hiding key data) have screamed at Jones for missing documents that don't have an impact on the study's results, among other indiscretions. Last week Jones told Nature that his team's handling of the missing documents from the 1990 study was "not acceptable." It was a welcome moment of contrition from one of the world's eminent scientists. If we're lucky, it will mark a turning point.