Influence of methane sources in Northern Hemisphere high latitudes on the interhemispheric asymmetry of its atmospheric concentration and climate

Numerical experiments with the INMCM4 climate model have shown that the observed 10% difference in the lower tropospheric methane concentration between the Arctic and the Southern Hemisphere can be reproduced in a climate model in which only the present-day spatial distribution of anthropogenic methane emissions and calculated emissions from wet ecosystems are considered. In model runs with an additional 50- or 100-Mt/year methane emission in the Arctic, the difference in atmospheric methane concentrations between the Arctic and the Southern Hemisphere is higher than the observed one. An additional methane emission of 4000 Mt/year in the Arctic is shown to result in an increase of 1.5A degrees in global mean surface air temperature. The spatial distribution of warming is similar to that induced by an increase in the carbon dioxide concentration, depends on the global mean methane concentration, and does not depend at all on where the additional methane source lies.