THE END OF THE PRESENT INTERGLACIAL - HOW AND WHEN

Despite the large decline in Northern Hemisphere summer insolation dur ing the last 8000 years, neither sea level nor polar temperatures have as yet undergone any significant downturn. This behavior is consisten t with the prediction by Kukla and Matthews (1972) that the Holocene i nterglacial will terminate suddenly with a jump to another of the clim ate system's modes of operation. This is what happened at the end of t he last period of peak interglaciation. However, complicating the situ ation is evidence that ice sheet growth during the transition from mar ine stage 5e to 5d preceded the shut down of the Atlantic's conveyor c irculation which is thought to have brought Europe's Eemian to a close . If so, then in the natural course of events, the end of the present interglaciation awaits the onset of ice cap growth. However, it must b e kept in mind that the ongoing buildup of greenhouse gases may alter the natural course of events. In particular, the warming and wetting o f the planet will gradually reduce the density of surface waters in th e regions where deep waters form. As this reduction is not likely to b e symmetrical between the northern Atlantic and the margin of the Anta rctic continent, the current near balance between deep water productio n in the north and south may be disrupted causing an abrupt reorganiza tion of the ocean's thermohaline circulation. Based on the paleoclimat ic record, such a reorganization would have had a profound impact on t he planet's climate. (C) 1998 Elsevier Science Ltd. All rights reserve d.