Jim Hansen may be the most respected climate scientist in the world. He's been director of NASA's premier climate research center, the Goddard Institute for Space Studies (GISS), for 25 years and a member of the National Academy of Sciences (NAS) for 10. And he more or less single-handedly turned global warming into an international issue one sweltering June day in 1988, when he told a group of reporters in a hearing room, just after testifying to a Senate committee, "It's time to stop waffling so much and say that the greenhouse effect is here and is affecting our climate now."

It took the rest of the scientific community about eight years to catch up with him on that point. He was ahead of the pack in 1988, and he remains so. He's been accurately predicting the progress of global warming for 25 years. And as the science grows ever more solid, owing in no small part to his own work, Hansen's predictions about an issue some see as the greatest threat civilization has ever faced are becoming ominously precise.