Jeff Severinghaus is a professor of geosciences at the Scripps Institution of Oceanography, UC San Diego. He received his Ph.D. from Columbia University’s Lamont-Doherty Earth Observatory in 1995, in isotope geochemistry. Severinghaus is an environmental geochemist working on gases trapped in ice cores, to reconstruct past variations in atmospheric composition and climate. His research often takes him to Antarctica and Greenland. Severinghaus is the 2011 Claire C. Patterson Medalist for environmental geochemistry and is a fellow of the American Geophysical Union.