When it comes to key warriors in America’s battle over the causes of climate change, few rival Pennsylvania State University professor Michael E. Mann. Mann, who directs the Penn State Earth System Science Center, led a 1998 reconstruction of temperature records going back thousands of years and showing that global averages had shot up in recent decades.
Featured in a 2001 report by the U.N. Intergovernmental Panel on Climate Change, the chart resembled a hockey stick, with the ancient temperatures running along the handle and the latest figures rising sharply at the base. It sparked intense debate over the human contribution to global warming and transformed Mann from a geeky geophysicist into a public fighter in a bruising political and legal war over how to conduct science and public policy.
"The Hockey Stick and the Climate Wars: Dispatches from the Front Lines" by Michael E. Mann
Much of the industrial and developing world accepts the scientific consensus that the burning of fossil fuels, and other activities that release heat-trapping greenhouse gases, contribute to climate change; on Friday, the International Energy Agency announced that global carbon dioxide emissions from fossil fuel burning had reached a record high of 31.6 gigatons in 2011, up 3.2 percent from 2010. A March survey by Gallup shows that 53 percent of Americans attribute global warming to human activity. But in the past three years, some Americans have challenged this view, particularly conservative Republicans, and the political elite is sharply divided.
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.