CO2 measurements from polar ice cores: more data from different sites

Air in the bubbles of polar ice has in principal the same composition as the atmospheric air at the time of ice formation. Based on this relationship, an increase in atmospheric CO₂ since the beginning of industrialisation has been documented (Neftel et al. 1985, Pearman et al. 1986) in Antarctic ice cores. It has also been shown that the CO₂ concentration was much lower during the glacial period than in the preindustrial Holocene (Neftel et al. 1982, Barnola et al. 1987). These two results are well established. In this paper, we will discuss possible small deviations of the CO₂ concentration in air bubbles from that of the atmosphere at the time of enclosure. To do this, new results from Crête (Central Greenland) ice cores, covering the period since the beginning of industrialisation are presented, showing a good agreement with the data from Antarctic ice cores. In addition, the record of the atmospheric CO₂ concentration during the transition from the last glaciation to the Holocene and the fast variations in the concentration of atmospheric CO₂ during parts of the last glaciation, as suggested by Greenland ice core data, will be discussed.