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Elementa: Science of the Anthropocene

New article in "Elementa: Science of the Anthropocene" by Brett Thornton et al.

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

Thornton, B.F., Etiope, G., Schwietzke, S., Milkov, A.V., Klusman, R.W., Judd, A., Oehler, D.Z., 2021. Conflicting estimates of natural geologic methane emissions. Elementa: Science of Anthropocene 9(1).

Global natural versus anthropogenic fossil CH4 emission estimates.Saunois et al. (2020) reported annual bottom-up fossil fuel emissions of approximately 180 Tg, 25% of which were natural emissions (Etiope and Schwietzke, 2019), out of a global annual total of 747 Tg. In contrast, Hmiel et al. (2020) suggested median annual geo-CH4 emissions of only 1.6 Tg. DOI: