Rising methane: is warming feeding warming? [Introduction]

Introduction to discussion meeting issue. Methane is the second-most important anthropogenic greenhouse gas after carbon dioxide. The atmospheric burden is rising rapidly. CH4 growth from about 720 ppb in pre-industrial times to nearly 1900 ppb now has predominantly been caused by human activity. This is proportionately a much greater rise than the increase in CO2. With a direct heating impact of about 0.5 Wm−2 and around 1 Wm−2 if indirect impacts are included, the climate warming consequences of anthropogenic methane emissions are very important.

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