Jim Hansen, director of NASA's Goddard Institute for Space Studies (Credit: Ben Baker)

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."

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