Overview of Atmospheric Methane Detection Methods

Human activities since the First Industrial Revolution have more than doubled the concentration of methane in the atmosphere. While methane emissions account for 3% of total greenhouse gas emissions by mass, their radiative forcing (or climate forcing) accounts for 23% of total radiation. The 2023 Methane Emissions Report released by GHGSat shows that by the end of 2023, global methane emissions reached approximately 378 MtCO2e, double the amount emitted in 2022. Currently, methane is the second largest greenhouse gas after carbon dioxide and is receiving significant attention in all major economies worldwide.

Systematic detection of atmospheric methane began in the 1880s with the World Meteorological Organization's (WMO) Global Atmosphere Watch (GAW). Based on the platform on which the detector is mounted, atmospheric methane detection methods can be categorized into ground-based, space-based, and space-based methods.

△TCCON Global Site Distribution Map

Ground-based detection

Ground-based detection started earliest, and currently the major global ground-based methane observation networks include the Total Carbon Column Observation Network (TCCON) and the National Disturbance and Change in Atmosphere Detection Network (NDACC).

Ground-based detection has high sensitivity and can provide high-precision atmospheric methane detection data, but the number of ground stations distributed globally is limited and their spatial distribution is uneven, with low coverage of observation stations in South America, Africa, Oceania and Asia.

△Machine-based atmospheric methane detection

Space-based detection

In the field of airborne detection, a series of airborne detectors have been developed, including the Airborne Laser Infrared Absorption Spectrometer (ALIAS), the Airborne Atmospheric Trace Gas Chromatograph (ALIAS-II), the Gas Monitoring Lidar (GML), NASA's Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-NG), GHGSat's Airborne Spectrometer (GHGSat-AV), and the MethaneSAT Airborne Simulator (MethaneAIR).

Airborne detection enables real-time, on-site detection, allowing for rapid flight surveys within a certain range and quick responses to suspected atmospheric methane leaks. Airborne detection can consistently quantify methane emissions exceeding 10 kg/h, and some spectrometers can even quantify emissions below 5 kg/h.

△Space-based atmospheric methane detection capability

Star-based exploration

Since 1990, satellite remote sensing has been increasingly widely used for monitoring atmospheric composition. The United States, European Union countries, Japan, Canada, and China have successively launched multiple satellites with atmospheric methane detection capabilities, gradually forming a multi-scale spatial methane detection system covering the globe, regions, and point sources. As the performance of satellite-based sensors improves, detection accuracy is gradually increasing.

Space-based detection compensates for the low spatial coverage of ground-based and space-based detection. Ground-based and space-based detection provide verification data for the accuracy of space-based detection. The three detection methods of ground-based, space-based and space-based detection complement each other, providing a data foundation for atmospheric methane detection. They also provide verification and support for bottom-up emission inventories through a top-down approach.