2026/06/01 by Xueying Yu, Dylan B. Millet, Daven K. Henze +5 · 1 voice
Environmental Science · Earth and Planetary Sciences · #Atmospheric and Environmental Gas Dynamics #Atmospheric chemistry and aerosols #COVID-19 impact on air quality
paper · doi:10.1029/2025ef007067
Abstract Satellite observations show that atmospheric methane (CH 4 ) increased by a record‐breaking 19 ppb in 2020, but the causes are unclear because of uncertain impacts from COVID‐related pollutant shifts on hydroxyl (OH) radical concentrations. Here we employ an ensemble of constraints to simultaneously quantify methane sources and sinks for 2020 in a manner consistent with space‐based measurements of its oxidation products (formaldehyde, HCHO; carbon monoxide, CO) and with in situ measurements of methyl chloroform (MCF, an OH proxy). We find that resolving methane source and sink changes requires constraints from the CH 4 ‐HCHO‐CO cascade and from MCF: reliance on either alone causes overfitting. The optimized year‐2020 global methane sources (557 [514–601] Tg/y) and sinks (505 [459–550] Tg/y) are at the low end of Global Carbon Project ensemble estimates. We further resolve the 2020 methane increase into two distinct periods. During March‐May, inversions reveal that methane emissions and global‐mean OH values are both lower than predicted; the latter likely reflects offsetting impacts from methane and other pollutants. From June‐August, inversions identify methane emission underestimates that mainly reflect temperature‐driven biogenic sources. Our study highlights the methane lifetime increase that can accompany reduced pollutant emissions, and demonstrates the necessity of multi‐species, satellite‐based observations for understanding and attributing future methane trends.