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Sahara and Tundra - Hotspots" in climate research

Potsdam, 12 March 2003


Heat and aridity in the Sahara, cold and snow in the tundra - clearly defined landscape types which have something in common: in both regions climate and the land surface interact particularly strongly with one another. "Man-made" climate change could cause savannahs to spread into the Sahara and coniferous forest to invade previously treeless tundra. This is shown by computer simulations produced by scientists from the Potsdam Institute for Climate Impact Research (PIK).


The Potsdam scientists, together with colleagues from the Belgian Université catholique de Louvain and the American National Center for Atmospheric Research, used an Earth system model to investigate the interactions between climatic warming and the shifting of vegetation zones in North Africa and Siberia. Earth system models are expanded climate models which describe the interplay between atmosphere, ocean, vegetation and ice masses. Atmosphere and land surface interact particularly strongly in the Sahara and the tundra; these regions are thus termed "hotspots" by the scientists.

The models show that increased concentrations of carbon dioxide in the atmosphere, together with associated warming and with increasing precipitation in tropical regions, may have an especially strong influence on the vegetation at the southern margins of the Sahara and in the tundra. Thereby parts of the Sahara and the tundra may possibly change. A grass-and-tree-covered savannah could expand into the desert and the wooded taiga could invade the tundra with its rich variety of mosses and lichens. The models show that the shifting of the vegetation zones has in turn an influence on the atmosphere: the savannah attracts greater amounts of precipitation and the expansion of coniferous forests leads to additional warming in northern latitudes. These changes could take place quite abruptly, in the case of the Sahara within a few decades.

Sudden climate and vegetation changes have occurred before in the Earth's history. Around 11,000 to 6,000 years ago the Sahara was significantly greener and the taiga migrated northward. The advance of vegetation in the northern hemisphere was caused by climatic warming. The question therefore arises as to whether there are parallels between the past climate and possible changes in climate and vegetation in the future. "The changes look similar, but the underlying physical mechanisms play a differing role. The important point is that our models are able to describe shifts of vegetation. Such studies help us to understand the past and to test the value of our climate models" says Victor Brovkin, PIK scientist and first author of the tundra study. Martin Claussen, Director of PIK and lead author of the Sahara study, adds "It is important for us to recognise that climatic change does not simply mean a gradual warming, but could contain some surprises". The shifting of vegetation zones seems to be one such surprise: judging by the simulations, vegetation has a tendency to make more abrupt changes than was previously supposed.

Both studies were published in the March edition of the journal "Climatic Change".

The Potsdam Institute for Climate Impact Research (PIK) was founded in 1992 and employs 121 scientists. Its research on climate change, climate impacts and sustainable development is of international renown. PIK is a member of the Leibniz Association.

Contacts:
Sahara Study: Prof. Dr. Martin Claussen, martin.claussen@pik-potsdam.de, Tel. +49-331-288-2522
Tundra Study: Dr. Victor Brovkin, victor.brovkin@pik-potsdam.de, Tel. +49-331-288-2592

Press office:
Anja Wirsing, anja.wirsing@pik-potsdam.de, Tel. +49-331-288-2507

Original articles:
Claussen, M., Brovkin, V., Ganopolski, A., Kubatzki, C., Petoukhov, V., 2003: Climate Change in Northern Africa: The past is not the future. Climatic Change. 57 (1), 99-118.
Brovkin, V., Levis, S., Loutre, M.F., Crucifix, M., Claussen, M., Ganopolski, A., Kubatzki, C., Petoukhov, V., 2003: Stability analysis of the climate-vegetation system in the northern high latitudes. Climatic Change. 57 (1), 119-138.

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