Climategate: What Really Happened?
ENVIRONMENT, 25 Apr 2011
How climate science became the target of “the best-funded, best-organized smear campaign by the wealthiest industry that the Earth has ever known.”
IT’S DIFFICULT TO IMAGINE how a guy who spends most of his time looking at endless columns of temperature records became a “fucking terrorist,” “killer,” or “one-world-government socialist.” It’s even harder when you meet Michael Mann , a balding 45-year-old climate scientist who speaks haltingly and has a habit of nervously clearing his throat. And when you realize that the reason for all the hostility is a 12-year-old chart, it seems more than a little surreal.
Back in 1999, Mann—then a newly minted Ph.D.  (PDF)—and a pair of colleagues constructed a chart that plotted historical climate data, spanning from 1000 to 1980. Because recorded temperatures only begin in the late 19th century, Mann and his team largely relied on so-called proxy records—measurements of tree rings, coral, and ice cores whose variations illustrate temperature changes over the years. The graph showed that after nearly 900 years of relatively stable temperatures, there was a sharp uptick starting in the 20th century.
You may have seen a version of the graph, known as the “hockey stick,” in the film An Inconvenient Truth —the rise in carbon dioxide levels* is so steep, Al Gore  uses a mechanical ladder  to reach the most recent readings. The graph was featured prominently in a seminal 2001 report from the United Nations’ Intergovernmental Panel on Climate Change  (IPCC) that concluded, for its first time, that “the balance of evidence suggests a discernible human influence on global climate.”
The film and the IPCC report made the chart famous, but Mann’s version  (PDF) appeared in the journal Geophysical Research Letters . There, he and his colleagues explained the complex methodology, and the uncertainties, involved in their study; but let’s face it, phrases like “multiproxy data network” and “extensive cross-validation experiments” are lost on most of us. “This,” Mann says with an upward swoop of the arm, “the public understands.” The chart tells “a very simple story.” 
In fact, some complained that it was too simple, glossing over  uncertainties in historical climate readings in order to make a more dramatic point . Yet numerous other reconstructions of historical temperature records made since Mann’s graph have also shown a dramatic uptick in the 20th century, and a 2006 assessment from the National Academy of Sciences concluded  (PDF) that while Mann’s methodology wasn’t perfect, the story the chart told was accurate.
Yet global warming skeptics have made the graph exhibit A in their cause. Congressional hearings  have focused on it, and it has been the impetus for multiple  critical  books  and blog posts. Skeptics have dismissed the graph  as “little more than paleo-phrenology” and claimed that “Mann-made warming is real , while man-made warming remains at best a theory, more likely a hypothesis.”
And Mann himself has become a target. Virginia’s crusading Republican attorney general  has suggested that he may have committed research “fraud.” The 2011 Conservative Political Action Conference  had a booth where attendees could throw eggs at his picture. There was a flood of hate mail, much of it containing death threats: “Your work is finished. YOU ARE GOING TO HANG SOON!”
“Climate science has basically been at the receiving end of the best-funded, best-organized smear campaign by the wealthiest industry that the Earth has ever known—that’s the bottom line,” Mann told me when I visited him at his Penn State office last November. Near his desk, Mann keeps an actual hockey stick, signed by Middlebury College’s championship hockey team to show the school’s support for his work.
Things really heated up for Mann in late 2009, when more than 1,000 emails from him and other climate scientists were lifted from a server at the Climatic Research Unit  (CRU) of the UK’s University of East Anglia, the world’s leading research institution focused on climate change. The emails offered a window into the climate-science bunker, with a view of Mann and his fellow researchers growing increasingly defensive. One scientist wrote  that he was “tempted to beat the crap out of” a skeptic at the libertarian Cato Institute. Another joked that the way to deal with skeptics was “continuing to publish quality work in quality journals (or calling in a Mafia hit).” Scientists suggested that they would rather destroy data than provide them to their critics. They also discussed using “tricks” in their research, debated how to frame uncertainties in some of their data, and attempted to control access to peer-reviewed journals.
Within days, the heist—soon dubbed “Climategate ”—was all over the news. Glenn Beck called it  a “potentially major scandal”; Fox News crowed  that the emails “undercut the whole scientific claim for man’s impact on global warming.” Rep. James Sensenbrenner (R-Wis.) decried  (PDF) them as evidence of “scientific fascism.”
The immediate impact on public opinion was dramatic. A poll by Yale and George Mason University  (GMU) found that in November 2008, 71 percent of respondents agreed that the planet is warming (PDF). Five weeks after Climategate, only 57 percent believed it. The emails, said a Yale report  (PDF), had “a significant effect on public beliefs in global warming and trust in scientists.”
IF A SINGLE PERSON CAN BE credited with setting the stage for Climategate, it’s Stephen McIntyre, the retired mining consultant behind the popular skeptic blog Climate Audit . Over the past decade, McIntyre has built a reputation for finding methodological errors—some real, some perceived—in climate studies. The Wall Street Journal heralded McIntyre  as “global warming’s most dangerous apostate.”
Indeed, McIntyre has made goading scientists—particularly Mann—close to a full-time job. Like Mann, McIntyre is genial in interviews, but on his blog, his tone toward the scientists targeted by his audits ranges from inquisitive to openly hostile.
The 63-year-old squash enthusiast from Toronto made his money in mining. He has also consulted for the Canadian oil and gas exploration company CGX Energy . He says his mining ties don’t affect his views on climate change and insists that his prolific blogging on the topic has not benefited him financially—rather, it’s taken time away from more profitable business.
* Correction: An earlier version of this piece stated that the graph featured in the film showed temperature rise. It actually shows rise in CO2 levels. We regret the error.
McIntyre belongs to the school of skeptics known as “lukewarmers”—those who believe the planet is warming and humans are playing a role (see our Field Guide to Climate Change Skeptics ), but don’t think this is as much of a problem as it has been made out to be.
“I’m not particularly comfortable with either side of the US debate,” McIntyre told me. “There are obviously competent and intelligent people that view it as a serious problem. That doesn’t mean that they’re right, but it’s not a hoax.” Nor does he oppose government regulations on principle, as do some of the free-market think tanks that regularly invite him to DC for speaking engagements. “I’m a Canadian,” says McIntyre. “I think governments can do things.”
McIntyre’s entrée into the climate debate came with a paper he coauthored with economist Ross McKitrick that critiqued an earlier version of Mann’s  (PDF) hockey-stick graph. The paper was published in the November 2003 issue of Energy and Environment . It’s a publication known for providing a platform to skeptics—which is why, among the trove of hacked emails, there’s one from Mann urging  colleagues to “dismiss this as [a] stunt, appearing in a so-called ‘journal’ which is already known to have defied standard practices of peer-review.” Mann predicted that “the usual suspects are going to try to peddle this crap.”
Sure enough, McIntyre and McKitrick were soon invited to Washington for a briefing  (PDF) arranged by the George C. Marshall Institute and the Competitive Enterprise Institute (CEI), both free-market think tanks that have been heavily funded by ExxonMobil and other oil interests. They were also asked to meet with Sen. James Inhofe  (R-Okla.), who has called climate change  “the greatest hoax ever perpetrated on the American people.”
The targets of McIntyre’s audits were less enthralled. “I wouldn’t send him anything,” Mann emailed CRU head Phil Jones  in February 2004. “I have no idea what he’s up to, but you can be sure it falls into the ‘no good’ category…There is no reason to give them any data, in my opinion, and I think we do so at our own peril!”
In February 2005, McIntyre and McKitrick published  (PDF) another critique of the hockey-stick chart in the more-respected Geophysical Research Letters. They argued, essentially, that the chart underestimates the uncertainties about historical temperatures and relies on proxy data that they believe are “no more informative about the distant past than a table of random numbers.”
McIntyre isn’t alone in his skepticism about proxy data—in fact, it’s at the heart of the climate debate. Recorded temperature measurements only go back about 160 years , so scientists use data from tree rings, ice cores, and coral  to reconstruct what the climate was like  before that. For two millennia, those data sets align to show swings of about one degree Fahrenheit in either direction. But then, in the 1960s, some tree-ring data diverge  (PDF) and suggest declining temperatures—even as actual temperatures show a dramatic rise. No one knows quite why this is; some researchers suggest the trees may actually be showing the stress from human activities. This divergence is one reason that many skeptics argue against using temperature reconstructions in climate change research.
McIntyre’s paper made headlines. A few days after publication, he was featured in a front-page piece in the Wall Street Journal that pitted  (PDF) his hockey-stick critique against the whole of global warming science, saying he had “helped to reopen the debate.”
Few scientists will ever get that kind of coverage for their life’s work, let alone for a single article on someone else’s research. But McIntyre’s critique came at a time when those seeking to block action on climate change were on the defensive—many had been pilloried for their ties to industry (PDF ) and right-wing think tanks, and public opinion was turning toward action on climate change. At this pivotal moment, reopening the debate was just what the skeptics, and their industry backers, needed. McIntyre and McKitrick were flown to Washington for another briefing with the Marshall Institute and CEI  (PDF).
Congressional conservatives swung into action. Rep. “Smokey” Joe Barton  (R-Texas), then the chairman of the House Energy and Commerce Committee, launched a formal inquiry into the work of Mann and other climate scientists in June 2005. As part of the inquiry, Barton—who believes acting on global warming is “absolute nonsense ” and said in a hearing that “when it’s hot, we find shade ”—enlisted George Mason University statistician Edward Wegman  to produce a report on the hockey stick. (In doing so, Barton eschewed  (PDF) the more traditional route of requesting  (PDF) a report from the National Research Council, a branch of the National Academy of Sciences.)
The Hockey Game
600 years of temperature data can’t be wrong. Or can it?
MICHAEL MANN’S hockey-stick graph shows average temperatures over the past 1,000 years based on “proxy data” reconstructions from tree rings, ice cores, sediment, coral, and some instrumental data. The last 600 years of Mann’s proxy data are shown below in blue. Actual temperatures, starting in the 1850s, are shown in red. (The darker trend lines are based on 40-year averages.) Both sets of data show a sharp temperature spike after the Industrial Revolution and a slight dip in the 1960s followed by a continued rise in recorded temperatures. Other climatologists have done their own studies of historic climate variations, and there is much debate over the fact that some of those studies—specifically those focusing on certain sets of tree-ring data—suggest that modern temperatures are continuing to decline.
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