Sustained Decline in CFC-12 Emissions from China: Evidence for Successful Phase-out under the Montreal Protocol and Global Implications

The production and consumption of CFC-12 (dichlorodifluoromethane; CCl₂F₂), a major ozone-depleting substance and potent greenhouse gas, were globally phased out by 2010 under the Montreal Protocol. Observation-based (top-down) verification of this phase-out requires quantification of the CFC-12 emissions using atmospheric observations, which have been notably lacking post-2020 for China. In this study, 6814 new high-frequency <i>in situ</i> atmospheric observations of CFC-12 from three Chinese stations in 2024 were analyzed. Combining these observations with inverse modeling, we quantified China's most recent CFC-12 emissions and revealed a 72% decline, from 12.7 ± 2.2 gigagrams per year (Gg yr^-1) in 2016 to 3.6 ± 0.8 Gg yr^-1 in 2024. We also developed a new bottom-up inventory, which generally reconciles the discrepancy between observation-based estimates and previous inventories. From a global perspective, this study provides the first country-specific, observation-based estimates of CFC-12 emissions for 2024, accounting for 22.6% of the global CFC-12 emissions. In contrast, for other countries, no observation-based CFC-12 emissions exist, or only a few pre-2022 data are available. Approximately three-quarters (77.4%) of global CFC-12 emissions remain unattributed. These findings highlight both China's success in mitigating CFC-12 emissions, contributing to ozone layer protection and climate mitigation, and the need for enhanced emission quantification across other regions.