Martin Claussen, Professor of Climate Physics, Head of the Climate System Department, Managing Director, Potsdam Institute for Climate Impact Research, Potsdam University

Description: Climate change does not unfold gradually or in a linear way. Peering back 11,000 years in our own Holocene era, Martin Claussen sketches a picture of abrupt and brutal shifts in the biosphere. His work involves modeling complex interactions among atmosphere, ocean, sea ice and vegetation. The Sahara Desert was once a green oasis, but dramatic disruptions in the last six thousand years led to its very rapid browning. Claussen's models demonstrate that a slow evolution in the earth's orbit and its tilt toward the sun triggered a reaction that led to swift loss of moisture and vegetation in North Africa. Claussen believes that interactions within Earth's climate system — specifically between vegetation cover and sea ice — amplified the impact of the orbital shifts. "If the system gets a slight kick, it can jump from green to desert," says Claussen. As a result of this change, humans may have been forced to migrate from the devastated Sahara region to the fertile Tigris, Euphrates and Nile River valleys, where new civilizations sprang up. Looking forward, Claussen notes that triggers such as an excess of human-generated carbon dioxide or deforestation might provoke similar dramatic climatic changes in global hotspots.

About the Speaker(s): Claussen received his Diploma in Meteorology from the University of Hamburg in 1981, was awarded his Ph.D. at the Max-Planck Institute for Meteorology in 1984, and received his Habilitation at the University of Hamburg in 1991. He was on the faculty at Free University of Berlin and has held research scientist appointments at Max-Planck Institute for Meteorology, GKSS Research Center in Geestacht, and the Massachusetts Institute of Technology.

Claussen has served as chair of the German Meteorological Society since 2003 and Secretary (Climate Modelling) of the European Geosciences Union since 2004. He is a member of the German National Committee on Global Change Research, the German Meteorological Society, the European Geosciences Union and the American Geophysical Union.

Host(s): School of Science, Center for Global Change Science

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