CENTURY-SCALE EVENTS IN MONSOONAL CLIMATE OVER THE PAST 24,000 YEARS

BOTH the marine sediment record and numerical modelling of the atmosph eric summer circulation over the northern Indian Ocean and southeast A sia have shown that the monsoonal climate exhibits a direct but nonlin ear response to the intensity of solar insolation during summer, with a time lag of several thousand years1,2. Here we present evidence from a high-resolution record of oxygen isotopes and carbonate spanning th e past 24,000 calendar years that the response of the southwest monsoo n over the Arabian Sea to long-term, gradual insolation changes occurr ed in several distinct events of less than 300 years duration, at 14,3 00, 13,500, 13,060, 9,900, 8,800 and 7,300 C-14 yr BP. Thus, during th is transitional period from glacial to post-glacial conditions the slo w solar forcing seems to have induced very rapid changes in local clim ate. We speculate that the rapid response may be related to albedo cha nges in Asia.