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