james e. hansen (born march 29, 1941 in denison, iowa) headed the nasa goddard institute for space studies in new york city, a part of the goddard space flight center in greenbelt, maryland, earth sciences division until early 2013. he is currently an adjunct professor in the department of earth and environmental sciences at columbia university. hansen is best known for his research in the field of climatology, his testimony on climate change to congressional committees in the 1980s that helped raise broad awareness of the global warming issue, and his continuing advocacy of action to limit the impacts of climate change. he has been a critic of the bill clinton and george w. bush administration's stances on climate change.