ATMOSPHERIC CO2 CONCENTRATION AND MILLENNIAL-SCALE CLIMATE-CHANGE DURING THE LAST GLACIAL PERIOD

The analysis of air bubbles trapped in polar ice has permitted the rec onstruction of past atmospheric concentrations of CO2 over various tim escales, and revealed that large climate changes over tens of thousand s of years are generally accompanied by changes in atmospheric CO2 con centrations(1). But the extent to which such covariations occur for fa st, millennial-scale climate shifts, such as the Dansgaard-Oeschger ev ents recorded in Greenland ice cores during the last glacial period(2) , is unresolved; CO2 data from Greenland(3) and Antarctic(4) ice cores have been conflicting in this regard, More recent work suggests that Antarctic ice should provide a more reliable CO2 record, as the higher dust(5) content of Greenland ice can give rise to artefacts(1,6,7). T o compare the rapid climate changes recorded in the Greenland ice with the global trends in atmospheric CO2 concentrations as recorded in th e Antarctic ice, an accurate common timescale is needed. Here we provi de such a timescale for the last glacial period using the records of g lobal atmospheric methane concentrations from both Greenland and Antar ctic ice. We find that the atmospheric concentration of CO2 generally varied little with Dansgaard-Oeschger events (<10 parts per million by volume, p.p.m.v.) but varied significantly with Heinrich iceberg-disc harge events (similar to 20 p.p.m.v.), especially those starting with a long-lasting Dansgaard-Oeschger event.