Head of NASA's Goddard Institute of Space Studies

James Hansen, of New York City, is head of NASA's Goddard Institute of Space Studies and an adjunct professor in the department of geological sciences at Columbia University. He has been at the center of one of the most important scientific debates of the last quarter century. In 1988 he testified before a Senate subcommittee that the earth's average global temperature was rising and that the warming could be attributed to a build-up of industrial gases in the atmosphere. He used the term "greenhouse effect" to describe what was happening to the planet. This historic testimony made headlines around the world and began the debate on global warming that continues today. Hansen was elected to the National Academy of Sciences in 1996.