About.

Methane (CH₄) is a potent greenhouse gas contributing significantly to climate change. Due to its relatively short lifetime mitigation efforts on CH₄ emissions could rapidly and efficiently pay-off to limit climate change. Targetted mitigation efforts should rely on a solid understanding of sources and sink of CH₄ at all scales, from the global scale to local scales. Dedicated monitoring and modelling efforts are on-going to improve our understanding of the methane budget, including satellite platforms. The main satellite instruments contributing to the current understanding of the methane budget are TANSO on-board GOSAT, TROPOMI on-board Sentinel 5P, and IASI on-board METOP-B and METOP-C. Another category of satellite has recently been added to the existing constellation of CH₄-monitoring platforms. These satellites (e.g., GHGSat, PRISMA, MethaneSat) provide very high-resolution data focusing on specific areas.

Satellite instruments for observation of methane (from Jacob et al., 2022)

Average TROPOMI CH₄ concentrations (from Lorente et al., 2021)

The ESA initiative SMART-CH4 (Satellite Monitoring of Atmospheric Methane) is part of the EC-ESA JOINT EARTH SYSTEM SCIENCE INITIATIVE. It builds upon previous experience and projects (e.g., Methane+, HighResCH4, MethEO, MethaneCAMP, etc.) in satellite-based methane quantification, aiming to enhance emission products derived from satellites. The key objectives and tasks of SMART-CH4 include:

• Enhancing TROPOMI retrievals and multi-sensor products, incorporating SWIR/TIR data from IASI and TROPOMI. Advancing fine-scale emission detection using mid-resolution mappers like TROPOMI and high-resolution imagers such as GHGSat, MethaneSAT, EnMAP, or PRISMA. These improvements will lower detection thresholds, enabling the identification of smaller emitters like landfills, wetlands, and agricultural sources.
• Utilizing improved products to deepen our understanding of regional methane budgets, focusing on three key target regions: (i) Bucharest, Romania, for its landfill super-emitters; (ii) the Arctic, with its scientific interest in peatland and wetland emissions, alongside technical detection challenges arising from Arctic night and albedo effects (from snow and cloud cover); and (iii) South America, concerning tropical wetlands, forest fires, and anthropogenic emissions from landfills and agriculture.
• Contributing to the attribution of recent trends in CH₄ concentrations to specific sectors on a global scale.