Towards verifying and improving estimations of China's CO2 and CH4 budgets using atmospheric inversions.

This paper reviews the application of atmospheric inversions for estimating national CO₂ and CH₄ fluxes with a focus on China. After describing the fundamental principles and methodologies of the technique, we synthesize recent progress in estimating China's CO₂ and CH₄ budgets through atmospheric inversion, and compare these estimates with national greenhouse gas (GHG) inventory (NGHGI) reports. The inverted estimates for China's total CO2 and CH4 emissions amount to 8.35 ± 1.39 Pg CO2 a-1 and 60.8 ± 5.9 Tg CH4 a-1, respectively, in the last decade, which are in general consistent with NGHGIs. However, large uncertainties in spatial and temporal disaggregation of national budgets hinder the effectiveness of the method in verifying China's GHG budgets and improving NGHGI estimates. These uncertainties are largely driven by differences in inversion models, observational coverage and methodological assumptions. We recommend improving observational networks, conducting model intercomparison exercises and refining inversion methods to better support China's GHG reporting and future climate goals.