Anthropogenic Chloroform Emissions from China Drive Changes in Global Emissions

Abstract

Emissions of chloroform (CHCl 3 ), 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 3 from China were derived by atmospheric measurement-based "top-down" inverse modeling and a sector-based "bottom-up" inventory method. Topdown CHCl 3 emissions grew from 78 (72−83) Gg yr −1 in 2011 to a maximum of 193 (178−204) Gg yr −1 in 2017, followed by a decrease to 147 (138−154) Gg yr −1 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 3 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 3 emissions remain relatively constant in the future, as they have between 2018 and 2020.

Measurements and Modeling of the Interhemispheric Differences of Atmospheric Chlorinated Very Short‐Lived Substances

“…(2019) and An et al. (2023) have shown that the changes in anthropogenic emissions can explain the recent changes in global concentrations.…”

“…The detailed emission inventories for CH 2 Cl 2 and C 2 Cl 4 by Claxton et al (2020) are used in the model. The CHCl 3 is prescribed as surface boundary condition (vs. emissions) as it is largely emitted by natural sources, and its emissions are less well known although recent studies have tried to constrain its growing anthropogenic emissions (An et al, 2023;Fang et al, 2019). Similarly, 1,2-dichloroethane (1,2-DCA) is prescribed as surface boundary conditions as its emissions are even less well known than CHCl 3 .…”

“…This is in contrast to constant CHCl 3 mixing ratios between 30 and 90°N shown by Prinn et al (2000), which is used in our model. The global emissions of CHCl 3 showed a rapid increase between 2010 and 2017 (Laube et al, 2022), which is attributed to anthropogenic emission increases in China (An et al, 2023;Fang et al, 2019). On the other hand, CHCl 3 has major natural sources with higher emissions in the mid-latitude regions (Khalil & Rasmussen, 1999).…”

“…Nevertheless, the strong correlation between CHCl 3 and CH 2 Cl 2 , in particular in the tropics and NH (Figure S6 in Supporting Information S1), also suggests that maybe anthropogenic sources dominate CHCl 3 emissions sources. Fang et al (2019) and An et al (2023) have shown that the changes in anthropogenic emissions can explain the recent changes in global concentrations.…”

Sustained growth of sulfur hexafluoride emissions in China inferred from atmospheric observations

“…We quantify the uncertainty reduction of the hierarchical Bayesian inversion with non-Gaussian prior probability distributions following a previous approach 65 , by Eq. ( 1 ): where represents the uncertainty reduction in a specific region, which is calculated based on posterior uncertainty ( ) and prior uncertainty ( ).…”