Ongoing CO monitoring verify CO emissions and sinks in China during 2018-2021.

Accurate estimating CO emissions and sinks is crucial in achieving carbon neutrality in China. However, CO emissions from bottom-up inventories are uncertain at regional scales and lack independent verification from atmospheric perspectives. Here we integrated 39 high-precision CO stations in China to top-down invert emission-sink variations at 45 km × 45 km and achieved a full range of inventories verification. The results show that China's CO emissions are 15% higher than those of five bottom-up inventories, to an annual total of 3.40 Pg C a for 2018-2021. After deducting human and livestock respiration, the annual CO emissions were 3.13 Pg C a (11.48 Pg CO a). The annual increase in emissions slowed from 3.7% in 2019 to 1.1% in 2020 and resumed growth to 4.0% in 2021, consistent with observed CO growth rates in China. China's land CO sink, deducting farmland sinks and lateral fluxes, was 0.57 Pg C a (2.09 Pg CO a) for 2018-2021 (higher than most global inverse models), accounting for ∼16.9% of anthropogenic CO emissions. The land sink in China decreased by -19.3% in 2019 due to a weak El Niño event and increased by 3.2% in 2020 and 13.7% in 2021. It is worth noting that inverse CO emissions and sinks in western China still face large uncertainty due to limited CO monitoring. Overall, our top-down estimates demonstrate spatiotemporal variations in CO emissions and sinks from atmospheric perspectives and highlight challenges for different provinces in achieving 2060 carbon neutrality with verified estimates.