Differences of the atmospheric CH₄ concentration between the Arctic and Antarctic regions in pre‐industrial/pre‐agricultural era

Air samples in ice cores from Site J, Greenland and Mizuho, Antarctica were analyzed to reconstruct the past concentrations of atmospheric CH 4 at northern and southern high latitudes. The results showed that the CH 4 concentrations were fairly constant in the pre‐industrial/pre‐agricultural era covered by this study, average values being 756±10 and 701±10 ppbv for the Site J and Mizuho cores, respectively, and then increased significantly with time. The pre‐industrial/pre‐agricultural levels of the CH 4 concentration obtained from the Site J core were higher by 55±20 ppbv than those from the Mizuho core, suggesting that natural CH 4 sources had been stronger in the northern hemisphere than in the southern hemisphere.