Increase in CFC-11 emissions from eastern China based on atmospheric observations

The recovery of the stratospheric ozone layerrelies on the continued decline in the atmospheric concentrations of ozone-depletinggases such as chlorofluorocarbons1. The atmospheric concentration of trichlorofluoromethane(CFC-11), the second-most abundant chlorofluorocarbon, has declined substantially since the mid-1990s2. A recently reported slowdown in the decline of the atmospheric concentration of CFC-11 after 2012, however, suggests that global emissionshave increased3,4. A concurrent increase in CFC-11 emissionsfrom eastern Asia contributes to the global emissionincrease, but the location and magnitude of this regional source are unknown3. Here, using high-frequency atmospheric observations from Gosan, South Korea, and Hateruma, Japan, together with global monitoring data and atmospheric chemical transport modelsimulations, we investigate regional CFC-11 emissionsfrom eastern Asia. We show that emissionsfrom eastern mainland Chinaare 7.0 ± 3.0 (±1 standard deviation) gigagrams per year higher in 2014–2017 than in 2008–2012, and that the increase in emissionsarises primarily around the northeastern provinces of Shandong and Hebei. This increase accounts for a substantial fraction (at least 40 to 60 per cent) of the global rise in CFC-11 emissions. We find no evidence for a significant increase in CFC-11 emissionsfrom any other eastern Asian countries or other regions of the world where there are available data for the detection of regional emissions. The attribution of any remaining fraction of the global CFC-11 emissionrise to other regions is limited by the sparsity of long-term measurements of sufficient frequency near potentially emissiveregions. Several considerations suggest that the increase in CFC-11 emissionsfrom eastern mainland Chinais likely to be the result of new production and use, which is inconsistent with the Montreal Protocolagreement to phase out global chlorofluorocarbonproduction by 2010.