The recovery of the stratospheric ozone layer relies on the continued decline in the atmospheric concentrations of ozone-depleting gases such as chlorofluorocarbons. The atmospheric concentration of trichlorofluoromethane (CFC-11), the second-most abundant chlorofluorocarbon, has declined substantially since the mid-1990s. However, a slowdown in the decline of the atmospheric concentration of CFC-11 after 2012 was reported in the scientific literature in 2018, suggesting that global emissions have increased. In the past, CFC-11 had been used primarily as a propellant in aerosol products and as a foam plastic blowing agent. The production and consumption (use) of CFC-11 are controlled by the global Montreal Protocol. CFC-11 consumption has been banned in developed countries since 1996, and worldwide since 2010.

This presentation will show the results of a paper published in 2019 in the journal Nature that used atmospheric observations from a global network combined with inverse modelling techniques to pinpoint the source of the rogue emissions. According to these results, 40-60% of the increase in global emissions seen since 2013 is due to possibly illegal industrial activity in the Chinese provinces of Shandong and Hebei.