Illustration by Tom Bachtell

The chemist F. Sherwood Rowland is one of the few people in history about whom it can accurately be said: he helped save the world. In 1972, Rowland, a chemist at the University of California-Irvine, attended a talk on the compounds known as chlorofluorocarbons. At the time, these were being used as refrigerants, cleaning agents, and propellants in aerosol cans, and they had recently been detected in the air over the Atlantic. CFCs are unusually stable, but it occurred to Rowland that, if they were getting blown around the world, at very high altitudes they would eventually break down. He and one of his research assistants began to look into the matter, and they concluded that in the stratosphere CFCs would indeed dissociate. The newly liberated chlorine atoms would then set off a chain reaction, which would destroy the ozone layer that protects the earth from ultraviolet radiation.

Industry groups ridiculed Rowland’s findings—Aerosol Age accused him of being a K.G.B. agent—but other scientists confirmed them, and Rowland pressed for a ban on CFCs. As he said, “What’s the use of having developed a science well enough to make predictions if, in the end, all we’re willing to do is stand around and wait for them to come true?” The discovery, in the mid-nineteen-eighties, of an ozone “hole” over the South Pole persuaded world leaders, including Ronald Reagan, that the problem was, in fact, urgent, and a global treaty phasing out CFCs was approved in 1987.

Rowland’s question came to mind last week. At a meeting in Yokohama, the Intergovernmental Panel on Climate Change released its latest update on the looming crisis that is global warming. Only this time it isn’t just looming. The signs are that “both coral reef and Arctic systems are already experiencing irreversible regime shifts,” the panel noted. Composed in a language that might be called High Committee, the report is nevertheless hair-raising. The I.P.C.C.’s list of potential warming-induced disasters—from ecological collapse to famine, flooding, and pestilence—reads like a riff on the ten plagues. Matching the terror is the collective shame of it. “Why should the world pay attention to this report?” the chairman of the I.P.C.C., Rajendra Pachauri, asked the day the update was released. Because “nobody on this planet is going to be untouched by the impacts of climate change.”

Talk about standing around and waiting. As in the case of the destruction of the ozone layer, much of the key research on climate change was completed in the nineteen-seventies. (The first major report on the subject from the National Academy of Sciences was requested by President Jimmy Carter.) And, once again, it’s been clear since that time what needs to be done. Global warming is a product of carbon emissions produced by burning fossil fuels, so, if we want to limit warming, these emissions have to be phased out.

Economists on both sides of the political spectrum agree that the most efficient way to reduce emissions is to impose a carbon tax. “If you want less of something, every economist will tell you to do the same thing: make it more expensive,” former Mayor Michael Bloomberg observed, in a speech announcing his support for such a tax. In the United States, a carbon tax could replace other levies—for example, the payroll tax—or, alternatively, the money could be used to reduce the deficit. Within a decade, according to a recent study by the Congressional Budget Office, a relatively modest tax of twenty-five dollars per metric ton of carbon would reduce affected emissions by about ten per cent, while increasing federal revenues by a trillion dollars. If other countries failed to follow suit, the U.S. could, in effect, extend its own tax by levying it on goods imported from those countries.

Currently, instead of discouraging fossil-fuel use, the U.S. government underwrites it, with tax incentives for producers worth about four billion dollars a year. Those tax breaks are evidently ludicrous, and they should be repealed. According to the International Monetary Fund, the U.S. is the world’s largest single source of fossil-fuel subsidies; the I.M.F. has estimated that eliminating such subsidies worldwide could cut carbon emissions by thirteen per cent. Meanwhile, the tax credit responsible for much of the recent growth in wind generation in the U.S. has been allowed to lapse. This is more lunacy; that tax credit should be reinstated. On a state level, public-utility laws need to be revamped so that utility companies are rewarded for promoting energy efficiency rather than energy consumption. Building codes, too, need to be rewritten; according to the previous I.P.C.C. update, released in 2007, significant cuts in emissions from buildings could be achieved through measures, like improved insulation, that also save their occupants money.

When the first I.P.C.C. report was issued, back in 1990, George H. W. Bush was in the White House. Each of his successors, including Barack Obama, has vowed to address the problem, only to decide that he had better things to do. Obama had an opportunity early in his first term to make a real difference; legislation to impose a price on carbon emissions, through a cap-and-trade system, was approved by the House in 2009. But the President put little political muscle behind the bill, and it died the following year in the Senate. The White House is now trying to bypass Congress and reduce emissions through regulations. In January, the Environmental Protection Agency published rules governing emissions from new power plants; effectively, they prohibit the construction of coal-burning plants. In February, the Administration announced plans to tighten fuel-efficiency standards for vehicles like garbage trucks and tractor-trailers, and, this spring, it is expected to propose new regulations limiting emissions from existing power plants. These are all laudable efforts, but the last set of regulations, which should be the most consequential, are coming so late in Obama’s second term that they will be left to the next President to implement—or not, as the case may be. And, unfortunately, the Administration is undermining its own best efforts by pressing for more domestic fossil-fuel production.

The fact that so much time has been wasted standing around means that the problem of climate change is now much more difficult to deal with than it was when it was first identified. But this only makes the imperative to act that much greater, because, as one set of grim predictions is being borne out, another, even worse set remains to be written. ♦