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http://online.wsj.com/article/SB20001424052748704188104575083681319834978.html

In the next few days, the world's leading authority on global warming plans to roll out a strategy to tackle a tough problem: restoring its own bruised reputation.

A months-long crisis at the Intergovernmental Panel on Climate Change has upended the world's perception of global warming, after hacked emails and other disclosures revealed deep divisions among scientists working with the United Nation-sponsored group. That has raised questions about the panel's objectivity in assessing one of today's most hotly debated scientific fields.
The problem stems from the IPCC's thorny mission: Take sophisticated and sometimes inconclusive science, and boil it down to usable advice for lawmakers. To meet that goal, scientists working with the IPCC say they sometimes faced institutional bias toward oversimplification, a Wall Street Journal examination shows.
Richard Alley, a geoscientist who helped write the IPCC's latest report, issued in 2007, described a trip that summer to Greenland's ice sheet with senators who urged him to be as specific as possible about the potential for sea-level rise. The point many of them made, he said: Give more explicit advice—because, if the sea rises, "the levee has to be built some height."
The tension within the IPCC stretches back a decade or more, according to interviews with scientists and a review of hundreds of IPCC documents and emails. It has complicated the panel's work on matters ranging from the study of tree rings to the proper use of massively complex climate computer models.
The IPCC has faced withering criticism. Emails hacked from a U.K. climate lab and posted online late last year appear to show scientists trying to squelch researchers who disagreed with their conclusion that humans are largely responsible for climate change. And last month, the IPCC admitted its celebrated 2007 report contained an error: a false claim that Himalayan glaciers could melt by 2035. The IPCC report got the date from a World Wildlife Fund report.
Even some who agree with the IPCC conclusion that humans are significantly contributing to climate change say the IPCC has morphed from a scientific analyst to a political actor. "It's very much an advocacy organization that's couched in the role of advice," says Roger Pielke, a University of Colorado political scientist. He says many IPCC participants want "to compel action" instead of "just summarizing science."
To restore its credibility, the IPCC will focus on enforcing rules already on the books, IPCC Chairman Rajendra Pachauri and other officials said in interviews. Scientific claims must be checked with several experts before being published. IPCC reports must reflect disagreements when consensus can't be reached. And people who write reports must refrain from advocating specific environmental actions—a political line the IPCC isn't supposed to cross.
Mr. Pachauri describes the IPCC's record as "impeccable." Still, he said, the IPCC's reforms will aim to "ensure that even the slightest possibility of someone not adhering to procedures is eliminated completely. We just have to act like monitors at every stage."
The IPCC shared a Nobel Peace Prize with former Vice President Al Gore in 2007 for its report that year declaring climate change "unequivocal" and "very likely" caused by emissions of greenhouse gases due to human activity. Formed in 1988, the group doesn't conduct or fund research, but filters the work of researchers world-wide.
About 30 paid staffers help thousands of scientists who volunteer to assemble voluminous "assessment reports" every five or six years. The goal is to be "policy-relevant" but "never policy-prescriptive," the IPCC says.
The IPCC's budget, about $7 million this year, comes mainly from contributions from the U.S. and other industrialized nations.
Critics also allege a conflict of interest by Mr. Pachauri, the IPCC's chairman, who heads an energy-research institute in India and has done consulting work for multinationals.
Taken together, the organization's troubles raise questions about its quality control in summarizing science. But many scientists say the crisis doesn't undermine independent research demonstrating man's influence on the climate.
"There is a very broad and deep consensus that I buy into that we're producing too much CO2 and it's going to cause problems eventually," said John H. Marburger III, former science adviser to President George W. Bush. Many details remain uncertain, he said, but "I think it's unequivocal that there is a human component."
The IPCC last month expressed "regret" for the erroneous Himalayan statement, traced originally to a magazine article. "The organization has an impeccable record of having performed," Mr. Pachauri said, and its work "always includes the quantifications of uncertainties."
Regarding conflict of interest, Mr. Pachauri said, "I don't take a single penny" from the consulting work. Proceeds go to his energy institute and not to him personally, he said.
As climate change gained public attention in recent decades, some IPCC-affiliated scientists privately expressed concerns that conclusions were risked getting oversimplified. Keith Briffa, a climate scientist at East Anglia, expressed this worry in emails to colleagues in 1999, as work intensified on the IPCC's third major report, published in 2001. Mr. Briffa's particular concern: tree rings.
Scientists use tree rings and other proxies to assess temperatures thousands of years ago, before thermometers existed. Wider rings indicate greater growth, generally suggesting warmer temperatures, or higher precipitation, or both. Mr. Briffa pioneered the technique.
"I know there is pressure to present a nice tidy story as regards 'apparent unprecedented warming in a thousand years or more,' " he wrote to other researchers in the email, among those hacked at East Anglia. "In reality the situation is not quite so simple," Mr. Briffa wrote.
He didn't identify the source of the pressure. A university spokesman said Mr. Briffa wouldn't comment.
The problem: Using Mr. Briffa's tree-ring techniques, researchers in the '90s built charts suggesting temperatures in the late 20th century were the highest in a millennium. The charts were dubbed "hockey sticks" because they showed temperatures relatively flat for centuries, then angling higher recently.
But Mr. Briffa fretted about a potential issue. Thermometers show temperatures have risen since the '60s, but tree-ring data don't move in tandem, and sometimes show the opposite. (Average annual temperatures reached the highest on record in 2005, according to U.S. government data. They fell the next three years, and rose in 2009. All those years remain among the warmest on record.)
In his same 1999 email, Mr. Briffa said tree-ring data overall did show "unusually warm" conditions in recent decades. But, he added, "I believe that the recent warmth was probably matched about 1,000 years ago."
In other words, maybe the chart shouldn't resemble a hockey stick.
The data were the subject of heated back-and-forth before the IPCC's 2001 report. John Christy, one of the section's lead authors, said at the time that he tried in vain to make sure the report reflected the uncertainty.
Mr. Christy said in an interview that some of the pressure to downplay the uncertainty came from Michael Mann, a fellow lead author of that chapter, a scientist at Pennsylvania State University, and a developer of the original hockey-stick chart.
The "very prominent" use of the hockey-stick chart "overrules what tentativeness some of us actually intended," Mr. Christy wrote to the National Research Council in the U.S. a month after the report was published. Mr. Christy, a climate scientist at the University of Alabama in Huntsville, provided that email.
"I was suspicious of the hockey stick," Mr. Christy said in an interview. Had Mr. Briffa's concerns been more widely known, "The story coming out of the [report] may have been different in tone and confidence."
Mr. Mann said in an email interview, "I was not pushing 'hard' for anything of the sort." The chapter's authors, he said, "engaged in a robust, good faith discussion of what the level of certainty was." Mr. Mann also noted that his original 1998 hockey-stick paper stressed the uncertainties involved in reconstructing past temperatures.
Complicating matters, a simplified version of the hockey-stick chart appeared prominently in the 2001 report's "summary for policy makers"—a 34-page distillation of the full report. Thomas Stocker, a climate scientist at the University of Bern and member of the team that wrote the summary, said the team wrestled with how to make the summary "faithful to the full report and yet still comprehensible" to policy makers.
The hockey-stick chart is "the textbook example" of "how difficult the job really is" to summarize the full report, said Mr. Stocker, one of the top scientists overseeing the IPCC's next report, due in 2013 and 2014.
In retrospect, he said, the simplified version should have had more detail. It could suggest a clearer conclusion than the actual chart appearing deeper in the full report. "I think that was part of the problem—that we simplified it," he said. "It's not suppressing information, but it's making it harder for the rapid reader to have the full picture."
Another big issue: The accuracy of complex computer models that underpin the science. Run on supercomputers, these models try to predict how greenhouse-gas emissions might affect temperatures, and how temperatures might affect everything from glaciers to hurricanes.
In September 2000, Filippo Giorgi of the International Center for Theoretical Physics in Trieste, Italy, wrote a worried email. He said he felt pressure to cite simulations that hadn't yet been published in a scientific journal. He worried it showed a relaxation of standards.
The IPCC's rules "have been softened to the point that in this way the IPCC is not any more an assessment of published science (which is its proclaimed goal)," he wrote in the email. Mr. Giorgi added: "At this point there are very little rules and almost anything goes. I think this will set a dangerous precedent."
In an interview, Mr. Giorgi said the pressure he felt came from the panel overseeing his part of the report. The panel was co-chaired by Sir John Houghton, a scientist who previously had chaired the IPCC as a whole.
Mr. Houghton defended his panel's oversight. "Nobody was arguing for 'anything goes,'" he said this week. "Nobody was arguing for making choices that selected anything more dramatic or with a particular message," he said. "Everybody wanted to present the results in the most helpful as well as honest way."
Mr. Giorgi said that including the data ultimately did no harm, because the IPCC report included a disclaimer noting it hadn't appeared in a scientific journal. Eventually, he added, the work appeared in a journal.
Some researchers continued to feel pressure to boil down science as work began on the IPCC's fourth major report, published in 2007. Things that are "very difficult to quantify must be quantified to keep the policy makers happy," Mr. Alley, the geoscientist, who teaches at Penn State, said in an interview. "It's a very frustrating thing."
Mr. Alley walked that tightrope in helping write the chapter covering his specialty: the degree to which massive Greenland and antarctic ice sheets might melt, raising sea levels. The problem, he said: "Ice-sheet models are not very good."
Many conversations with policy makers—including Mr. Gore, the senators in Greenland and Christian Gaudin, a French senator—left the clear impression that "we scientists had better get better numbers," said Mr. Alley, adding that he understands their desire for detail.
So the scientists put numbers into the 2007 study, along with a big caveat—what Mr. Alley calls a "punt." The study took into account things like glacier melt in most of the world, but it noted that it excluded what's happening in the Greenland and Antarctic ice sheets, which "we can't predict," Mr. Alley said.
Inevitably, Mr. Alley said, some people have cited the numbers without that caveat.
A spokeswoman for Mr. Gore said he understands the uncertainties, and that he pointed out in statements "that there was essentially an asterisk" on the 2007 report's sea-level projections. "As he understands the situation from the ice-science community, the uncertainty in sea level applies in both directions," meaning sea-level rise could be greater or smaller than projected, her statement said.
In an interview, Mr. Gaudin, the French senator, recalled having lunch with Mr. Alley on a visit to Penn State where they discussed the interplay between scientists and politicians on the "big questions that interest society," notably climate change. Scientific reports, including the IPCC's, "need to have more precision," Mr. Gaudin said. It is "difficult for politicians to make a decision" otherwise.
Mr. Marburger, the former Bush science adviser, said he frequently heard policy makers express frustration at the lack of certainty in many areas of science, including climate. "'Why can't we get better numbers?' Everybody asks that," he said. "But science rarely gives you the right answer. Science tells you what the situation is, but it doesn't tell you what to do."