Capability of current observing systems to monitor CH₄ emissions from the regional to the global scales

Abstract. Top-down methane CH₄ flux estimates involve large uncertainties stemming from three main sources: (1) the coverage of the observing system, (2) systematic and random errors in the observation data and the priors and (3) errors in the atmospheric transport model. Quantifying these uncertainties is challenging, and methodological studies suggest they can be substantial. While global-scale uncertainties in total CH₄ emissions are relatively small (±5%), they increase significantly at regional scales exceeding ±20% for high latitudes. Differences in satellite and in situ measurement uncertainties, as well as variations in data density, further influence the precision of CH₄ flux estimates. Sectoral disaggregation of uncertainties improves error attribution, leading to more reliable regional flux assessments and trend detection. Its benefits are amplified in high-emission regions due to larger absolute uncertainties and more complex source mixtures.