Why methane surged in the atmosphere during the early 2020s

The atmospheric methane (CH 4 ) growth rate surged after 2019, peaking at 16.2 parts per billion per year (ppb year −1 ) in 2020 before declining to 8.6 ppb year −1 in 2023. Using multiple atmospheric inversions constrained by observation- and model-based prescribed hydroxyl radical (OH) fields and CH 4 atmospheric data, we show that a drop of OH radicals in 2020–2021, followed by recovery in 2022–2023, accounted for 83% of year-on-year variations in the CH 4 growth rate, the rest being explained by wetland and inland water emissions, which increased between 2019 and 2020–2022 +8.6 ± 2.6 teragrams of CH 4 per year (TgCH 4 year −1 ) and then decreased between 2022 and 2023 (−9.9 ± 3.3 TgCH 4 year −1 ). Most emission changes from 2019 to 2023 occurred in northern tropical wetlands in Africa and Asia, whereas South American wetlands emissions declined and Arctic emissions increased after 2019.