Jeff Severinghaus is a professor of geosciences in the Geosciences Research Division at Scripps Institution of Oceanography, University of California, San Diego. His current research interests center on using trapped bubbles of gases contained in ice cores to track changes in ancient climate.

Born in Kentfield, CA, on Aug. 26, 1959, Severinghaus received a bachelor’s degree in geology from Oberlin College in 1983, a master’s degree in geological sciences from UC Santa Barbara in 1988, and a Ph.D. in geological sciences from Columbia University’s Lamont-Doherty Earth Observatory in 1995.

Severinghaus uses krypton and xenon in the atmosphere to detect past ocean temperature change, taking advantage of the high solubility of these gases. The krypton and xenon are trapped along with air in the bubbles in glacial ice.

Severinghaus has developed a "horizontal ice core" in Antarctica for large-volume samples of the past atmosphere. He uses this to measure carbon-14 in atmospheric methane, which requires one ton of ice per sample, an amount more than is available from most ice cores. This measurement reveals the contribution of fossil sources of methane (such as seafloor methane hydrates) to the atmosphere during times of abrupt methane concentration increase.

Severinghaus’ team’s study of historic temperatures at an ice core site on the West Antarctic Ice Sheet using nitrogen and argon isotopes continues. Researchers also use measurements of the temperature in the borehole from which the core was extracted. A "memory" of temperature remains in the borehole due to the very slow diffusion of heat in ice, and this allows the researchers to infer the past surface temperature history. Using this borehole technique, Severinghaus’ team recently found that the Little Ice Age, a cold period from 1400-1850 A.D., occurred in Antarctica as well as in the Northern Hemisphere. The work demonstrated that the Little Ice Age was a global event and supports the idea that variations in the energy output of the Sun caused the Little Ice Age.

Current projects include construction of a "rapid access ice drill" to explore the three-dimensional interior of the Antarctic ice sheet in search of the oldest possible ice, which may allow a record of atmospheric carbon dioxide dating back 1.5 million years. This rapid access drill would allow drilling to the bed of an ice sheet in a few days, instead of the typical three to five years needed for a deep ice core.

Severinghaus has also performed extensive research in Greenland. His analysis of isotopes of nitrogen and argon contained in Greenland ice core bubbles have revealed that the earth went through a period of rapid warming at the end of the last ice age, some 11,000 years ago. He found that the region experienced a 15-degree-Fahrenheit jump in temperature in less than a decade, the impact of which was felt throughout the Northern Hemisphere.

His research raises the question of whether the addition of carbon dioxide to the atmosphere through the burning of fossil fuels could also produce a rapid change in climate, rather than the slow, steady rise in temperature many computer models of global climate now predict.

In other work, Severinghaus and Wallace Broecker, a geochemist at Lamont-Doherty, uncovered the cause of a life-threatening loss of oxygen from the Biosphere 2 project in Arizona. The two discovered that an excess of organic matter in the self-contained ecosystem’s soil set off uncontrolled growth of bacteria that feed on oxygen.

Severinghaus is the recipient of the 2011 Claire C. Patterson Medalist of the Geochemical Society, an award given annually for a breakthrough in environmental geochemistry. Severinghaus was also awarded a Comer Science and Education Fellowship (2002), a Packard Foundation Fellowship (2001), a NOAA Climate and Global Change Graduate Fellowship (1992), and a University of California Regents Fellowship (1985).

He worked in Nepal 1989-1991 to assist in a rural development project with World Neighbors.

Severinghaus and his family reside in Solana Beach, CA.

(August 2012)