The Climate Expert Who Delivered News No One Wanted to Hear | The New Yorker
Hansen, who is sixty-eight, has greenish eyes, sparse brown hair, and the distracted manner of a man who’s just lost his wallet. (In fact, he frequently misplaces things, including, on occasion, his car.) Thirty years ago, he created one of the world’s first climate models, nicknamed Model Zero, which he used to predict most of what has happened to the climate since. Sometimes he is referred to as the “father of global warming,” and sometimes as the grandfather.
Hansen has now concluded, partly on the basis of his latest modelling efforts and partly on the basis of observations made by other scientists, that the threat of global warming is far greater than even he had suspected. Carbon dioxide isn’t just approaching dangerous levels; it is already there. Unless immediate action is taken—including the shutdown of all the world’s coal plants within the next two decades—the planet will be committed to change on a scale society won’t be able to cope with. “This particular problem has become an emergency,” Hansen said.
Hansen’s revised calculations have prompted him to engage in activities—like marching on Washington—that aging government scientists don’t usually go in for. Last September, he travelled to England to testify on behalf of anti-coal activists who were arrested while climbing the smokestack of a power station to spray-paint a message to the Prime Minister. (They were acquitted.) Speaking before a congressional special committee last year, Hansen asserted that fossil-fuel companies were knowingly spreading misinformation about global warming and that their chairmen “should be tried for high crimes against humanity and nature.” He has compared freight trains carrying coal to “death trains,” and wrote to the head of the National Mining Association, who sent him a letter of complaint, that if the comparison “makes you uncomfortable, well, perhaps it should.”
Hansen insists that his intent is not to be provocative but conservative: his only aim is to preserve the world as we know it. “The science is clear,” he said, when it was his turn to address the protesters blocking the entrance to the Capitol Power Plant. “This is our one chance.”
When Hansen began his modelling work, there were good theoretical reasons for believing that increasing CO2 levels would cause the world to warm, but little empirical evidence. Average global temperatures had risen in the nineteen-thirties and forties; then they had declined, in some regions, in the nineteen-fifties and sixties. A few years into his project, Hansen concluded that a new pattern was about to emerge. In 1981, he became the director of GISS. In a paper published that year in Science, he forecast that the following decade would be unusually warm. (That turned out to be the case.) In the same paper, he predicted that the nineteen-nineties would be warmer still. (That also turned out to be true.) Finally, he forecast that by the end of the twentieth century a global-warming signal would emerge from the “noise” of natural climate variability. (This, too, proved to be correct.)
Throughout the nineteen-eighties and nineties, the evidence of climate change—and its potential hazards—continued to grow. Hansen kept expecting the political system to respond. This, after all, was what had happened with the ozone problem. Proof that chlorofluorocarbons were destroying the ozone layer came in 1985, when British scientists discovered that an ozone “hole” had opened up over Antarctica. The crisis was resolved—or, at least, prevented from growing worse—by an international treaty phasing out chlorofluorocarbons which was ratified in 1987.
“At first, Jim’s work didn’t take an activist bent at all,” the writer Bill McKibben, who has followed Hansen’s career for more than twenty years and helped organize the anti-coal protest in D.C., told me. “I think he thought, as did I, If we get this set of facts out in front of everybody, they’re so powerful—overwhelming—that people will do what needs to be done. Of course, that was naïve on both our parts.”
What is now happening, Hansen explained to the group in New Hampshire, is that climate history is being run in reverse and at high speed, like a cassette tape on rewind. Carbon dioxide is being pumped into the air some ten thousand times faster than natural weathering processes can remove it.
“So humans now are in charge of atmospheric composition,” Hansen said. Then he corrected himself: “Well, we’re determining it, whether we’re in charge or not.”
Among the many risks of running the system backward is that the ice sheets formed on the way forward will start to disintegrate. Once it begins, this process is likely to be self-reinforcing. “If we burn all the fossil fuels and put all that CO2 into the atmosphere, we will be sending the planet back to the ice-free state,” Hansen said. “It will take a while to get there—ice sheets don’t melt instantaneously—but that’s what we will be doing. And if you melt all the ice, sea levels will go up two hundred and fifty feet. So you can’t do that without producing a different planet.”
Once you accept that CO2 levels are already too high, it’s obvious, Hansen argues, what needs to be done. He displayed a chart of known fossil-fuel reserves represented in terms of their carbon content. There was a short bar for oil, a shorter bar for natural gas, and a tall bar for coal.
“We’ve already used about half of the oil,” he observed. “And we’re going to use all of the oil and natural gas that’s easily available. It’s owned by Russia and Saudi Arabia, and we can’t tell them not to sell it. So, if you look at the size of these fossil-fuel reservoirs, it becomes very clear. The only way we can constrain the amount of carbon dioxide in the atmosphere is to cut off the coal source, by saying either we will leave the coal in the ground or we will burn it only at power plants that actually capture the CO2.” Such power plants are often referred to as “clean coal plants.” Although there has been a great deal of talk about them lately, at this point there are no clean-coal plants in commercial operation, and, for a combination of technological and economic reasons, it’s not clear that there ever will be.
Hansen continued, “If we had a moratorium on any new coal plants and phased out existing ones over the next twenty years, we could get back to three hundred and fifty parts per million within several decades.” Reforestation, for example, if practiced on a massive scale, could begin to draw global CO2 levels down, Hansen says, “so it’s technically feasible.” But “it requires us to take action promptly.”
“In nearly all areas, the developments are occurring more quickly than had been assumed,” Hans Joachim Schellnhuber, the head of Germany’s Potsdam Institute for Climate Impact Research, recently observed. “We are on our way to a destabilization of the world climate that has advanced much further than most people or their governments realize.”
Scientifiques et responsablité : une véritable question à dépasser. Si on se limite à ce qui est « acceptable politiquement », est-on encore un scientifique quand la réalité de l’évolution de la planète est en jeu ? C’est à ce moment là qu’on devient un sciento-politique conservateur. La « communauté scientifique » a peur de son ombre, et pas seulement dans ce domaine. Hansen a raison de dire les conséquences politiques de ce que son travail scientifique lui a permis de découvrir.
But if Hansen’s anxieties about D.A.I. and coal are broadly shared, he is still, among climate scientists, an outlier. “Almost everyone in the scientific community is prepared to say that if we don’t do something now to reverse the direction we’re going in we either already are or will very, very soon be in the danger zone,” Naomi Oreskes, a historian of science and a provost at the University of California at San Diego, told me. “But Hansen talks in stronger terms. He’s using adjectives. He has started to speak in moral terms, and that always makes scientists uncomfortable.”
Hansen is also increasingly isolated among climate activists. “I view Jim Hansen as heroic as a scientist,” Eileen Claussen, the president of the Pew Center on Global Climate Change, said. “He was there at the beginning, he’s faced all kinds of pressures politically, and he’s done a terrific job, I think, of keeping focussed. But I wish he would stick to what he really knows. Because I don’t think he has a realistic view of what is politically possible, or what the best policies would be to deal with this problem.”