Variability in Atmospheric Methane From Fossil Fuel and Microbial Sources Over the Last Three Decades

Abstract Atmospheric measurements show an increase in CH 4 from the 1980s to 1998 followed by a period of near‐zero growth until 2007. However, from 2007, CH 4 has increased again. Understanding the variability in CH 4 is critical for climate prediction and climate change mitigation. We examine the role of CH 4 sources and the dominant CH 4 sink, oxidation by the hydroxyl radical (OH), in atmospheric CH 4 variability over the past three decades using observations of CH 4 , C 2 H 6 , and δ 13 C CH4 in an inversion. From 2006 to 2014, microbial and fossil fuel emissions increased by 36 ± 12 and 15 ± 8 Tg y −1 , respectively. Emission increases were partially offset by a decrease in biomass burning of 3 ± 2 Tg y −1 and increase in soil oxidation of 5 ± 6 Tg y −1 . A change in the atmospheric sink did not appear to be a significant factor in the recent growth of CH 4 .