Four corners: The largest US methane anomaly viewed from space

Methane (CH 4 ) is a potent greenhouse gas and ozone precursor. Quantifying methane emissions is critical for projecting and mitigating changes to climate and air quality. Here we present CH 4 observations made from space combined with Earth‐based remote sensing column measurements. Results indicate the largest anomalous CH 4 levels viewable from space over the conterminous U.S. are located at the Four Corners region in the Southwest U.S. Emissions exceeding inventory estimates, totaling 0.59 Tg CH 4 /yr [0.50–0.67; 2 σ ], are necessary to bring high‐resolution simulations and observations into agreement. This underestimated source approaches 10% of the EPA estimate of total U.S. CH 4 emissions from natural gas. The persistence of this CH 4 signal from 2003 onward indicates that the source is likely from established gas, coal, and coalbed methane mining and processing. This work demonstrates that space‐based observations can identify anomalous CH 4 emission source regions and quantify their emissions with the use of a transport model.