A sense of apocalypse hangs low over Elizabeth Kolbert’s Field Notes From a Catastrophe and Tim Flannery’s The Weather Makers, two important new books on global warming. Flannery, the director of the South Australian Museum in Adelaide and an accomplished science writer, warns: “If humans pursue a business-as-usual course for the first half of this century, I believe the collapse of civilization due to climate change becomes inevitable.” Kolbert, a writer at The New Yorker (where I also work), quotes a despairing New York University professor of physics, Marty Hoffert: “We’re going to just burn everything up; we’re going to heat the atmosphere to the temperature it was in the Cretaceous, when there were crocodiles at the poles. And then everything will collapse.”
But in many ways, the most striking thing that emerges from reading these two books and indeed from contemplating the larger phenomenon of global warming is that the earth has often been warmer than it’s likely to become in the next century–and not just for brief periods of time but for long swatches of its history. The question therefore becomes less one of apocalyptic endings–the biological world will no doubt survive global warming in some perhaps significantly altered form–than a political one of trying to parse just what kinds of changes we’ll have to make to adjust to what promises to be a brave new world.
Flannery and Kolbert are clear on the fundamentals. Greenhouse gases including not just carbon dioxide but also methane and water vapor have always existed in the earth’s atmosphere in a delicate balance with climate. By allowing solar radiation to reach the earth’s surface but trapping some of it before it radiates back out again, these gases have played a significant role in stabilizing the climate within the temperature bands that have allowed human life to flourish and expand over the past 10,000 years. Flannery points out that this 10,000-year period has been one of unusual climate stability and that it essentially includes the entire history of human civilization. He refers to it as “the long summer” and argues that climate stability may have been an essential factor in allowing humans to develop as they have.
But since the industrial revolution, we have been pumping increasing amounts of carbon dioxide into the atmosphere. By the mid-twenty-first century the atmosphere is expected to contain close to twice the carbon dioxide it did in the pre-industrial eighteenth century. This buildup of carbon dioxide has caused a rapidly accelerating warming of the earth’s atmosphere. As Kolbert notes, “1990 was the warmest year on record until 1991, which was equally hot. Almost every subsequent year has been warmer still…1998 ranks as the hottest year since the instrumental temperature record began.” The early years of this millennium were the second, third and fourth hottest until the figures came in for 2005, which established yet another record. “The world is now warmer,” Kolbert observes, “than it has been at any point in the last two millennia, and, if current trends continue, by the end of the century it will likely be hotter than at any point in the last two million years.”
The relationship between carbon dioxide buildup and the accelerating rise in the earth’s temperature is well established. It can seem almost binary–and therefore both predictable and controllable. It’s the kind of thing Americans have traditionally been good at: figure out the point at which the temperature rise becomes a problem, invent new technology, cut the levels of carbon emissions accordingly and presto, no more problem! But what renders the equation far more volatile are what Kolbert and Flannery refer to as “feedback loops,” a generic term for the many ways in which the simple carbon dioxide buildup tends to feed on itself within the larger, almost impossibly complex, climate system. These feedback loops include the fact that the Arctic ice sheet is melting and that the open water thus exposed absorbs more heat than the ice-covered ocean. The more the Arctic Ocean is exposed, therefore, the faster the heat rises. The resulting rise in Arctic temperatures has already begun to melt the Arctic permafrost, which is then likely to release enormously more carbon–frozen in place since the last ice age. An increasingly warmed atmosphere holds more water vapor (another greenhouse gas), and thus the cycle is further accelerated. As part of the general warming, the ocean too will warm, which will result in alterations to prevailing currents that are expected to cause regional droughts. One such drought is predicted for the Amazon, where, in some climate models, rainfall will decline by more than 60 percent, the temperature will rise ten degrees centigrade and the world’s largest rain forest will be transformed into an arid savannah. This in turn will release the carbon suspended in the forest into the atmosphere, further accelerating what seems like a distressingly unstoppable cycle. In other words, even if the relationship between atmospheric carbon dioxide and temperature is well established, the ways in which it plays out over the entire climate system are not. Kolbert notes that much of the interaction between the almost infinite variables involved in climate prediction can only usefully be examined in computer models of such complexity that running a single climate simulation can occupy a supercomputer for a month. The knowledge that derives from such modeling is necessarily esoteric, and it has left the scientists who run these computer studies tremendously concerned. A Princeton engineering professor, Robert Socolow, tells Kolbert that “in most of the cases, it’s the lay community that is more exercised, more anxious…. But, in the climate case, the experts–the people who work with the climate models every day…they are more concerned. They’re going out of their way to say, ‘Wake up!’ ”