Conflicting estimates of natural geologic methane emissions

Global bottom-up and top-down estimates of natural, geologic methane (CH4) emissions (average approximately 45 Tg yr–1) have recently been questioned by near-zero (approximately 1.6 based on measurements 14CH4 trapped in ice cores, which imply that current fossil fuel industries’ CH4 are underestimated 25%–40%. As we show here, such a global emission estimate is incompatible with multiple independent, from individual natural seepage areas, each the order 0.1–3 yr–1. Further research urgently needed to resolve conundrum before rejecting either method or associated accounting.