The Future Ozone Layer Conundrum

Future concentrations of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) will determine stratospheric ozone levels by 2100. We examine the range of possible ozone recovery with the Whole Atmosphere Community Climate Model by individually varying these three concentrations from strict mitigation scenarios to business as usual. If the increase in CO2 concentration slows down, then mitigating additional ODSs like N2O is important for avoiding further ozone depletion. However, if CO2 emissions continue as usual, reducing N2O will only exacerbate the extratropical ozone increase while marginally reducing tropical ozone depletion. We would thus face the conundrum of simultaneously protecting the tropics from increased ultraviolet (UV) exposure and the extratropics from reduced UV exposure. Future changes in methane can also have substantial consequences for ozone recovery.