SIMULATED CLIMATE AND BIOMES OF AFRICA DURING THE LATE QUATERNARY - COMPARISON WITH POLLEN AND LAKE STATUS DATA

New compilations of African pollen and lake data a.re compared with cl imate (CCM1, NCAR, Boulder) and vegetation (BIOME 1,2, GSG, Lund) simu lations for the last glacial maximum (LGM) and early to mid-Holocene ( EMH). The simulated LGM climate was ca 4 degrees C colder and drier th an present, with maximum reduction in precipitation in semi-arid regio ns. Biome simulations show lowering of montane vegetation belts and ex pansion of southern xerophytic associations, but no change in the dist ribution of deserts and tropical rain forests. The lakes show LGM cond itions similar or drier than present throughout northern and tropical Africa. Pollen data indicate lowering of montane vegetation bells, the stability of the Sahara, and a reduction of rain forest. The paleoenv ironmental data are consistent with the simulated changes in temperatu re and moisture budgets, although they suggest the climate model under estimates equatorial aridity. EMH simulations show temperatures slight ly less than present and increased monsoonal precipitation in the east ern Sahara and East Africa. Biome simulations show an upward shift of montane vegetation belts, fragmentation of xerophytic vegetation in so uthern Africa, and a major northward shift of the southern margin of t he eastern Sahara. The lakes indicate conditions wetter than present a cross northern Africa. Pollen data show an upward shift of the montane forests, the northward shift of the southern margin of the Sahara, an d a major extension of tropical rain forest. The lake and pollen data confirm monsoon expansion in eastern Africa, but the climate model fai ls to simulate the wet conditions in western Africa. (C) 1998 Elsevier Science Ltd. All rights reserved.