We demonstrate the capabilities of the GHGSat satellite constellation to detect and quantify offshore methane emissions using a sun glint observation mode. Using this technique, we observe offshore methane emissions from space ranging from 180 kg h⁻¹ to 84 000 kg h⁻¹. We further assess the instrument performance in offshore environments, both empirically and using analytical modelling, and find that the detection limit varies with latitude and season.

Using two machine learning models, which were trained on TROPOMI methane satellite data, we detect 2974 methane plumes, so-called super-emitters, in 2021. We detect methane emissions globally related to urban areas or landfills, coal mining, and oil and gas production. Using our monitoring system, we identify 94 regions with frequent emissions. For 12 locations, we target high-resolution satellite instruments to enlarge and identify the exact infrastructure responsible for the emissions.

We review the capability of satellite observations of atmospheric methane to quantify methane emissions on all scales. We cover retrieval methods, precision requirements, inverse methods for inferring emissions, source detection thresholds, and observations of system completeness. We show that current instruments already enable quantification of regional and national emissions including contributions from large point sources. Coverage and resolution will increase significantly in coming years.