Unraveling the sources of uncertainty in China's top-down methane emission estimates

Accurate quantification of methane emissions is critical for setting and tracking the mitigation goals. However, previously estimated anthropogenic methane emissions in China differ by up to 50% among different studies. Satellite observations are expected to reduce the uncertainty, but large discrepancies still exist in earlier quantifications. Here, using satellite observations from the blended TROPOMI+GOSAT product, we conducted an ensemble of high-resolution (~50 km) inversions to assess the sources of uncertainty in the quantification. Overall, satellite observations can provide robust constraints on China’s total emissions but are less effective in quantifying individual sources with lower emission magnitudes. Of all sectors, emissions from coal mines and livestock can be well constrained due to frequent satellite observations, higher emission magnitudes, and lower prior uncertainty. Furthermore, we constructed marginal cost curves for emission reductions from each source to better inform future mitigation measures.