Atmospheric CO2 and climate change on millennial time scales during the last glacial period

How atmospheric CO2 varies and is controlled on millennial time scale is an important question for understanding how the carbon cycle and climate change are linked. Common time scales for climate proxies and atmospheric CO2 are needed to answer this question. Here we provide atmospheric CO2 records from ~90 to 20 ka BP (thousand years before 1950) from the Byrd ice core, on a chronology synchronized with Greenland ice core records, allowing direct comparison of CO2 with Greenlandic and Antarctic temperature proxies, Heinrich events and atmospheric CH4. Atmospheric CO2 rose several thousand years before abrupt warming in Greenland associated with Dansgaard- Oeschger events, 2, 4, 8, 12, 14, 17, 19, 20, and 21, and the start of CO2 increases predates massive ice discharge events (H events 2, 3, 4, 5, 5a, 6) by 0 to 3 ka. The CO2 increase rate was rapidly reduced at the Greenland warming (which also corresponds to a maximum in Antarctic temperature) for each of these events, implying a global mechanism that can simultaneously affect atmospheric CO2 and temperature in both hemispheres. The CO2 decrease following Antarctic temperature maxima/abrupt Greenland warming event lagged those features by several centuries. CO2 variations during millennial events of the last ice age have features in common with the CO2 rise during the last glacial termination, including tight correlation with Antarctic warming, a several thousand year lead relative to Greenland warming, and possibly small jumps in CO2 at the time of abrupt Greenland warming.