Although the dramatic climate disruptions of the last glacial period have received considerable attention, relatively little has been directed toward climate variability in the Holocene (11,500 cal yr B.P. to the present). Examination of ?50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000"8000, 6000"5000, 4200"3800, 3500"2500, 1200"1000, and 600"150 cal yr B.P. Most of the climate change events in these globally distributed records are characterized by polar cooling, tropical aridity, and major atmospheric circulation changes, although in the most recent interval (600"150 cal yr B.P.), polar cooling was accompanied by increased moisture in some parts of the tropics. Several intervals coincide with major disruptions of civilization, illustrating the human significance of Holocene climate variability.

24The stable carbon isotope ratio of atmospheric CO 2 (! 13 C atm ) is a key parameter to decipher 25 past carbon cycle changes. Here we present ! 13 C atm data for the last 24,000 years derived 26 from three Antarctic ice cores. We conclude that a pronounced 0.3‰ decrease in ! 13 C atm 27 during the early deglaciation can be best explained by upwelling of old, carbon-enriched 28 waters in the Southern Ocean. Later in the deglaciation, regrowth of the terrestrial 29 biosphere, changes in sea surface temperature, and ocean circulation governed the ! 13 C atm 30 evolution. During the Last Glacial Maximum, ! 13 C atm and CO 2 were essentially constant, 31suggesting that the carbon cycle was in dynamic equilibrium and that the net transfer of 32 carbon to the deep ocean had occurred before then. showing pronounced differences in atmospheric CO 2 rates of change in the course of the 47 last glacial/interglacial transition (3). Many processes have been involved in attempts to 48 explain these CO 2 variations, but it has become evident that none of these mechanisms 49 alone can account for the 90 ppmv increase in atmospheric CO 2 . A combination of 50 processes must have been operating (4, 5), with their exact timing being crucial. However, 51 a unique solution to the deglacial carbon cycle changes has not been yet found. 52 53

A detailed reconstruction of West African monsoon hydrology over the past 155,000 years suggests a close linkage to northern high-latitude climate oscillations. Ba/Ca ratio and oxygen isotope composition of planktonic foraminifera in a marine sediment core from the Gulf of Guinea, in the eastern equatorial Atlantic (EEA), reveal centennial-scale variations of riverine freshwater input that are synchronous with northern high-latitude stadials and interstadials of the penultimate interglacial and the last deglaciation. EEA Mg/Ca-based sea surface temperatures (SSTs) were decoupled from northern high-latitude millennial-scale fluctuation and primarily responded to changes in atmospheric greenhouse gases and low-latitude solar insolation. The onset of enhanced monsoon precipitation lags behind the changes in EEA SSTs by up to 7000 years during glacial-interglacial transitions. This study demonstrates that the stadial-interstadial and deglacial climate instability of the northern high latitudes exerts dominant control on the West African monsoon dynamics through an atmospheric linkage.