TEMPERATURE AND RAINFALL ESTIMATES FOR THE PAST 40,000 YEARS IN EQUATORIAL AFRICA

THERE has been considerable debate about the magnitude of the decrease in temperature1,2 and the change in precipitation3 in the African tropics during the last glacial period. With the advent of fossil pollen studies in equatorial regions, it is now generally agreed that the temperature did decrease at this time in tropical regions4, but the magnitude of the temperature fluctuations and discrepancies between the continental5 and marine6 temperature records have yet to be resolved7. Here we present new quantitative estimates of temperature and precipitation using a multivariate analysis8 of pollen time-series data from peat deposits in Burundi for the past 40,000 years9. For the last glacial period, our estimate of a temperature decrease of 4 ± 2 °C is less than those (ranging from 5 to 8 °C) derived from snow-line and tree-line records5,7. Model simulations7 indicate that the snow-line and tree-line estimates (from high-elevation sites at ̃4,000 m above sea level) are incompatible with the marine temperature record. Our lower estimate from a site of intermediate elevation may help resolve the differences between these records. We also estimate that the mean annual rainfall decreased by 30% during the last glacial period, in agreement with the rainfall history inferred from lake level fluctuations10. © 1990 Nature Publishing Group.