Overview
- The temporary global decline in OH in 2020–2021—triggered by COVID-era reductions in NOx from transport, aviation and shipping—accounts for roughly 80% of year-to-year changes in methane growth, with OH recovering in 2022–2023.
- A prolonged La Niña expanded flooded areas and boosted microbial emissions from wetlands and inland waters, especially in tropical Africa and Southeast Asia, with additional increases in Arctic regions.
- Atmospheric methane growth peaked at about 16.2 ppb per year before easing to 8.6 ppb per year in 2023, and global concentrations reached roughly 1921 ppb in 2023.
- Isotopic fingerprints show microbial sources dominated the surge, while fossil fuel and wildfire contributions were comparatively small.
- An international team updated the 2019–2023 methane budget by integrating three inverse models with NOAA surface networks, GOSAT satellite data and inventories, concluding that cleaner-air NOx cuts must be paired with stronger direct methane reductions.