The Impact of Continuing CFC-11 Emissions on Stratospheric Ozone

摘要

Trichlorofluoromethane (CFC-11, CFCl_3) 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 (CO_2, CH_4, and N_2O). 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.