James ("Jim") Hansen at a 1995 panel discussion and in 2009. One of seven children of a tenant farmer, Hansen saved his money and went to the University of Iowa, where he came under the spell of an outstanding scientist, James van Allen. Hansen eventually became adjunct professor at Columbia University and the director of a NASA institute specializing in the atmospheres of planets. As decades passed, his predictions of how materials added to the atmosphere would change the climate proved to be correct. Predicting dangerous future changes, Hansen reluctantly became outspoken in warning that it was essential to restrict emissions.

                Upper photo by Joe Pineiro, Columbia University Record, 19 Jan. 1996. Lower: Scanpix, 2009.