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CO2 and Climate During the Last Glacial Period
A new paper has been published in Science magazine entitled: ‘Atmospheric CO2 and Climate on Millennial Time Scales During the Last Glacial Period,’ by Jinho Ahn and Edward J. Brook.
The Abstract states:
Reconstructions of ancient atmospheric carbon dioxide (CO2) variations help us better understand how the global carbon cycle and climate are linked. We compared CO2 variations on millennial time scales between 20,000 and 90,000 years ago with an Antarctic temperature proxy and records of abrupt climate change in the Northern Hemisphere. CO2 concentration and Antarctic temperature were positively correlated over millennial-scale climate cycles, implying a strong connection to Southern Ocean processes. Evidence from marine sediment proxies indicates that CO2 concentration rose most rapidly when North Atlantic Deep Water shoaled and stratification in the Southern Ocean was reduced. These increases in CO2 concentration occurred during stadial (cold) periods in the Northern Hemisphere, several thousand years before abrupt warming events in Greenland.
The paper concludes:
Our results support the idea that atmospheric CO2 concentration is controlled by oceanic processes, especially those associated with proxies for the reduction of stratification in the Southern Ocean, but also affected by the Northern Hemisphere climate. Reductions in overturning circulation in the Northern Hemisphere appear to be associated with increases in atmospheric CO2. On the basis of these data, if global warming causes a decrease in the overturning circulation, we might expect a positive feedback from additional CO2 emissions to the atmosphere. However, the application of those observations to the future carbon cycle should be done cautiously because of differences between glacial and interglacial climate boundary conditions. It is likely that higher-resolution records of CO2 will reveal more details about precise timing between Antarctic and Greenlandic temperature and atmospheric CO2.