Twenty years ago on Monday, James E. Hansen testified before the Senate Energy Committee -- in a room kept intentionally warm by committee staff -- that the atmospheric buildup of carbon dioxide and other greenhouse gases from burning fossil fuels and forests was already perceptibly influencing Earth's climate.
Then, as now, Dr. Hansen, the director of NASA's Goddard Institute for Space Studies, was pushing beyond what many of his colleagues in climatology were willing to say -- at least publicly. His supporters say that, given how science and events appear to be catching up with his projections of two decades ago, the world had better heed his new recommendations. His critics show few signs of ever accommodating the ideas he now presses, which include a prompt moratorium on new coal-burning power plants until they can capture and store carbon dioxide and a rising tax on fuels contributing greenhouse-gas emissions, with the revenue passed back directly to citizens, avoiding the complexities of "cap and trade" bills.
Watch Hanson in an interview with Andrew C. Revkin: