In addition to these orbital variations, we also know that carbon dioxide content covaries with these glaciations, withCO2 variations constituting what is known as a positive feedback of orbital variations. Nevertheless, the exact role of the greenhouse effect is still uncertain, particularly for the rapid episodes of deglaciation.
With American colleagues (Shakun et al. 2012), we have precisely studied the evolution of temperatures during the last deglaciation from -21,000 to -8,000 years before present: a period recent enough to be studied with precision. We have compiled a hundred or so records from all over the planet, including those already published for the Atlantic and Indian Oceans.
The first major result of our study is that the global average temperature has generally followed the increase inCO2 measured in the bubbles contained in the Antarctic ice cores. To understand the mechanisms, it is necessary to consider the different latitude bands separately. In fact, the last deglaciation took place in five major stages.
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Article reprinted in La Lettre du Collège de France n° 35, December 2013
