The Impact of Continuing CFC‐11 Emissions on Stratospheric Ozone

AbstractTrichlorofluoromethane (CFC‐11, CFCl3) is a major anthropogenic ozone‐depleting substance and greenhouse gas, and its production and consumption are controlled under the Montreal Protocol. However, recent studies show that CFC‐11 emissions have been near constant or increasing since 2002. In this study, we use a two‐dimensional chemistry‐climate model to investigate the stratospheric ozone response to a range of future CFC‐11 emissions scenarios. A scenario with future emissions sustained at 10 gigagrams per year (Gg/year) above the baseline WMO (2018) A1 scenario results in minor additional global (90°S–90°N) ozone depletion of 0.13% by 2100, and a 1.5‐year delay in the global ozone recovery to 1980 levels, relative to the baseline. A scenario with 72.5 Gg/year (the 2013–2016 average) sustained to 2100 results in a substantial 15% increase in effective equivalent stratospheric chlorine and nearly 1% additional global ozone depletion by 2100, with a 7.5‐year delay in the recovery to 1980 global ozone levels, relative to the baseline. The ozone response averaged over time has a strong linear dependence on the cumulative amount of future CFC‐11 emissions under a wide range of scenarios. The resulting ozone response sensitivity gives a simple metric relating the time‐averaged ozone change to the cumulative CFC‐11 emissions. This sensitivity has an inverse dependence on future greenhouse gas concentrations (CO2, CH4, and N2O). For the medium Intergovernmental Panel on Climate Change Representative Concentration Pathway‐6.0 scenario, the sensitivity per 1,000 Gg of cumulative CFC‐11 emissions is −0.1% and −1% for global and Antarctic spring ozone, respectively.