Update on global ozone: past, present, and future

This chapter deals with the evolution of global ozone outside of the polar regions. The increase of ozone depleting substance (ODS) concentrations caused the large ozone decline observed from 1980 to the mid- 1990s. Since the late 1990s, concentrations of ODSs have been declining due to the successful implementation of the Montreal Protocol. As reported in the last Assessment, global ozone levels have remained stable since 2000. Ozone columns observed in the last four years have largely remained in the range observed since 2000. Over the next decades we expect increasing global-mean stratospheric ozone columns, as ODSs decline further. Climate change and emissions of greenhouse gases, especially carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), also affect the evolution of global stratospheric ozone, particularly in the second half of the 21st century, when ODS concentrations are expected to be low