Some advocates have gone so far as to hack computers and steal the e-mails of Mann and other climate researchers in an effort to undermine global climate negotiations. A respected hydrologist retaliated by tricking a climate-skeptic group into releasing its internal documents.
Mann’s new book, “The Hockey Stick and the Climate Wars,” is part of a series of attempts by activists and others to answer the question of why global warming has become a political flash point. Mann has devised an analogy to explain why he and other researchers have become the objects of such fierce public scrutiny and vilification, which he terms “the Serengeti strategy.” Likening climate scientists to zebras, he writes, “The climate change deniers isolate individual scientists just as predators on the Serengeti Plain of Africa hunt their prey: picking off vulnerable individuals from the rest of the herd.” He asserts that he and others have become targets because their findings challenge the entrenched fossil-fuel industries, which have tried to discredit them.
There is no question that Mann has found himself in the crosshairs of those who promote the idea that global warming stems from nonhuman factors, such as sun spots and natural temperature variability. The hockey stick relied on proxy data derived from a range of sources — including tree rings, cores extracted from ice sheets, corals and lake sediments — to reconstruct temperatures from hundreds of years ago, times for which there is no written record. Mann and his team used a statistical tool called “principal component analysis” to tease out which factors are most responsible for a given change over time and to compare data from all over the globe.
Two Canadians, mining consultant Stephen McIntyre and economist Ross McKitrick, challenged the hockey stick on a variety of fronts. First they went after the proxy data; later they employed the same statistical tool that Mann and his colleagues did, but in what Mann considers an inconsistent way. The result was a smoothing out of the pattern embodied in the hockey stick. “If there is a lesson” in these sorts of fights, Mann writes, “it is that scientific findings that rest on such technical complexities are prone to abuse by those with a potential ax to grind.”
Herein lies the problem with the current climate debate: It’s an insider’s game. The average American doesn’t study principal component analysis and doesn’t need to. But when that’s what scientific experts — and lawmakers who have been briefed by their staffers — are talking about, it leaves most of the public in the dark. Mann makes this point several times, as when, for example, he describes Rep. Henry Waxman (D-Calif.) throwing around arcane scientific terms to challenge climate skeptics during a 2005 hearing: “I’m fairly certain that this was the first congressional hearing at which a representative uttered the phrase ‘regularized expectation-maximization.’ You could just hear statistics junkies everywhere doing their best Beavis and Butthead impressions: ‘Did he just say regularized expectation-maximization? Heh, heh, heh.’ ”