Influence of vegetation changes during the Last Glacial Maximum using the BMRC atmospheric general circulation model

The influence of different vegetation distributions on the atmospheric circulation during the Last Glacial Maximum (LGM, 21 000 years before present) is investigated. The atmospheric general circulation model of the Bureau of Meteorology Research Center was run using a modern vegetation and in a second experiment with a vegetation reconstruction for the LGM. It is found that a change from conifer to desert and tundra causes an additional LGM cooling of 1-2 degreesC in Western Europe, up to -4 degreesC in North America and -6 degreesC in Siberia. An expansion of dryland vegetation causes an additional annual cooling of 1-2 degreesC for Australia and northern Africa. On the other hand, an increase of temperature (2 degreesC) is found in Alaska due to changes in circulation. In the equatorial region the LGM vegetation leads to an increased modelled temperature of 0.5-1.5 degreesC and decreased precipitation (30%) over land due to a reduction of the tropical rainforest, mainly in Indonesia, where the reduction of precipitation over land is associated with an increase of precipitation of 30% over the western Pacific.