Atmospheric remote sensing for anthropogenic methane emissions: Applications and research opportunities

Methane is the second most significant greenhouse gas (GHG) only after carbon dioxide. Human activities substantially increase the atmospheric methane concentration globally, but little is known about the distribution and characteristics of anthropogenic methane emissions. Remote sensing approaches can identify, geolocate, and quantify near-surface methane emissions. This literature review summarizes the devices, methods, implementations, and potential research opportunities for atmospheric remote sensing of anthropogenic methane emissions. Specifically, this literature review has identified that methane emissions are primarily generated from three key sectors and one key area: the energy sec-tor, the waste sector, the agriculture sector, and the general urban area. Regional and point source emission quantifi-cations are two major study challenges. This review concludes that different sectors have different emission patterns, and therefore, proper remote sensing instruments and platforms might be chosen according to different study tasks. Among the paper reviewed, the energy sector is the most well-studied, while the emissions in the waste sector, the ag-riculture sector, and the urban areas are less clear. In the future, new methane observation satellites and portable re-mote sensing instruments provide opportunities to improve understanding of methane emissions. Moreover, the synergistic applications among several different remote sensing instruments and cooperation between top-down and bottom-up measurements can mitigate the limitation of each individual instrument and can achieve better monitoring performance.