James Hansen, director of the NASA Goddard Institute for Space Studies, has [co-authored a] paper saying that [future global warming] is likely to turn out worse than most people think. The most recent major report from the Intergovernmental Panel on Climate Change in 2007 projects a temperature rise of three degrees Celsius, plus or minus 1.5 degrees-enough to trigger serious impacts on human life from rising sea level, widespread drought, changes in weather patterns, and the like. But according to Hansen and his nine co-authors ... the correct figure is closer to six degrees C. That's the equilibrium level," he says. "We won't get there for a while. But that's where we're aiming." And although the full impact of this temperature increase will not be felt until the end of this century or even later, Hansen says, the point at which major climate disruption is inevitable is already upon us. "If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted," the paper states, "CO2 will need to be reduced from its current 385 ppm [parts per million] to at most 350 ppm." The situation, he says, "is much more sensitive than we had implicitly been assuming." Back in 1998 ... Hansen was arguing that the human impact on climate was unquestionable, even as other leading climate scientists continued to question it. He was subsequently proved right, not only about the human influence but about the approximate pace of future temperature rise.