“A few months ago, James Hansen, the director of NASA’s Goddard Institute for Space Studies, in Manhattan, took a day off from work to join a protest in Washington, D.C. The immediate target of the protest was the Capitol Power Plant, which supplies steam and chilled water to congressional offices, but more generally its object was coal, which is the world’s leading source of greenhouse-gas emissions. As it happened, on the day of the protest it snowed. Hansen was wearing a trench coat and a wide-brimmed canvas boater. He had forgotten to bring gloves. His sister, who lives in D.C. and had come along to watch over him, told him that he looked like Indiana Jones…

Thirty years ago, Hansen, who is sixty-eight, created one of the world’s first climate models, nicknamed Model Zero, which he used to predict most of what has happened in the climate since. Hansen has now concluded, partly on the basis of his latest modeling 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. 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 climate change on a scale society won’t be able to cope with.”