The New York Review of Books
Volume 54, Number 4 · March 15, 2007

Warning on Warming

By Bill McKibben

Climate Change 2007: The Physical Science Basis: Summary for Policymakers

Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC, 18 pp., available at

When the Intergovernmental Panel on Climate Change (IPCC) issued its latest report in early February, it was greeted with shock: "World Wakes to Climate Catastrophe," reported an Australian paper. But global warming is by now a scientific field with a fairly extensive history, and that history helps set the new findings in context— a context that makes the new report no less terrifying but much more telling for its unstated political implications.

Although atmospheric scientists had studied the problem for decades, global warming first emerged as a public issue in 1988 when James Hansen, a NASA scientist, told Congress that his research, and the work of a handful of other scientists, indicated that human beings were dangerously heating the planet, particularly through the use of fossil fuels. This bold announcement set off a scientific and political furor: many physicists and chemists played down the possibility of serious harm, and many governments, though feeling pressure to react, did little to restrain the use of fossil fuel. "More research" was the mantra everyone adopted, and funding for it flowed freely from governments and foundations. Under the auspices of the United Nations, scientists and governments set up a curious hybrid, the IPCC, to track and report on the progress of that research.

From roughly 1988 to 1995, the hypothesis that burning coal and gas and oil in large quantities was releasing carbon dioxide and other gases that would trap the sun's radiation on earth and disastrously heat the planet remained just that: a hypothesis. Scientists used every means at their disposal to reconstruct the history of the earth's climate and to track current changes. For example, they studied the concentration of greenhouse gases in ancient air trapped in glacial cores, sampled the atmosphere with weather balloons, examined the relative thickness of tree rings, and observed the frequency of volcanic eruptions. Most of all, they refined the supercomputer models of the earth's atmosphere in an effort to predict the future of the world's weather

By 1995, the central Herculean tasks of both research and synthesis were largely complete. The report the IPCC issued that year was able to assert that "the balance of evidence suggests" that human activity was increasing the planet's temperature and that it would be a serious problem. This was perhaps the most significant warning our species, as a whole, has yet been given. The report declared (in the pinched language of international science) that humans had grown so large in numbers and especially in appetite for energy that they were now damaging the most basic of the earth's systems—the balance between incoming and outgoing solar energy. Although huge amounts of impressive scientific research have continued over the twelve years since then, their findings have essentially been complementary to the 1995 report—a constant strengthening of the simple basic truth that humans were burning too much fossil fuel.