Anthropogenic Chloroform Emissions from China Drive Changes in Global Emissions.

Emissions of chloroform (CHCl), a short-lived halogenated substance not currently controlled under the Montreal Protocol on Substances that Deplete the Ozone Layer, are offsetting some of the achievements of the Montreal Protocol. In this study, emissions of CHCl from China were derived by atmospheric measurement-based "top-down" inverse modeling and a sector-based "bottom-up" inventory method. Top-down CHCl emissions grew from 78 (72-83) Gg yr in 2011 to a maximum of 193 (178-204) Gg yr in 2017, followed by a decrease to 147 (138-154) Gg yr in 2018, after which emissions remained relatively constant through 2020. The changes in emissions from China could explain all of the global changes during the study period. The CHCl emissions in China were dominated by anthropogenic sources, such as byproduct emissions during disinfection and leakage from chloromethane industries. Had emissions continued to grow at the rate observed up to 2017, a delay of several years in Antarctic ozone layer recovery could have occurred. However, this delay will be largely avoided if global CHCl emissions remain relatively constant in the future, as they have between 2018 and 2020.