Climate of east Africa 6000 C-14 yr BP as inferred from pollen data

International audienceThis paper presents a spatial reconstruction of climate in East Africa at 6000 C-14 yr B.P. Two different approaches using pollen data have been used, the standard ``best modern analogues'' method and the new ``plant functional type'' method, based on groups of pollen taxa. Both methods have been applied to 32 fossil pollen spectra dated at 6000 C-14 yr B.P. For each site, we have estimated two climatic parameters (annual precipitation and mean annual temperature), three bioclimatic parameters (ratio of actual to potential evapotranspiration, and the mean temperature of the coldest and warmest months). Results show that the temperature lapse rate was less steep at 6000 C-14 yr B.P. than it is today. The climate was wetter north of 3 degrees S (precipitation anomalies >+50 mm/yr) and slightly drier farther south (precipitation anomalies less than or equal to+50 mm/yr). The ratio of actual to potential evapotranspiration also indicates conditions similar to or wetter than today north of 3 degrees S (anomalies >10%). The climate was warmer than today by 2 degrees C north of the equator and was cooler southward (less than or equal to-1 degrees C). Although both methods indicate similar climatic patterns, the plant functional type method provides more consistent results. (C) 2000 University of Washington