Why methane surged in the atmosphere during the early 2020s.
basic_science · Level V
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- Record sourced from PubMed, PMID 41642995.
- Also identified by DOI 10.1126/science.adx8262.
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Abstract
The atmospheric methane (CH<sub>4</sub>) growth rate surged after 2019, peaking at 16.2 parts per billion per year (ppb year<sup>-1</sup>) in 2020 before declining to 8.6 ppb year<sup>-1</sup> in 2023. Using multiple atmospheric inversions constrained by observation- and model-based prescribed hydroxyl radical (OH) fields and CH<sub>4</sub> 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<sub>4</sub> 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<sub>4</sub> per year (TgCH<sub>4</sub> year<sup>-1</sup>)] and then decreased between 2022 and 2023 (-9.9 ± 3.3 TgCH<sub>4</sub> year<sup>-1</sup>). 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.