Abstract: Unregulated very short-lived halogenated substances (VSLSs) are playing an increasingly important role in global stratospheric ozone depletion as emissions of long-lived ozone-depleting substances such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) decline due to the controls of the Montreal Protocol on Substances that Deplete the Ozone Layer. The impacts of VSLSs on the stratospheric ozone layer could be more significant when their emissions are from regions with strong convective pathways from the surface to the stratosphere, such as occur in East and South Asia, compared to other regions.

Dichloromethane (CH₂Cl₂) and chloroform (CHCl₃) are the two most abundant chlorine containing VSLSs, whose global emissions have increased substantially in the last two decades. In this study, the emissions of CH₂Cl₂ and CHCl₃ over 2011-2020 in China were derived by atmospheric measurements and a “top-down” inverse modelling method. Emissions of CH₂Cl₂ from China increased substantially throughout the period, while emissions of CHCl₃ increased through 2017 and then decreased afterwards. The derived distributions of emissions of both substances in China are consistent with anthropogenic origins, which can also be validated by the “bottom-up” inventories compiled in this study. The inter-annual variations of emissions in China of the two substances can explain nearly the entire global emission changes of each substance, indicating the dominant role of China in driving global emission changes.