Climate change, ozone recovery, and the stratosphere

From a climate perspective, changes to circulation of the stratosphere are important for two main reasons. The stratosphere contains Earth's protective ozone layer, and changes to the circulation of the lower stratosphere affect tropospheric weather and climate. During the past 25+ years the composition of the stratosphere has changed significantly, with higher concentrations of greenhouse gases and ozone-depleting substances (ODSs), and decreases in global ozone. With recent reductions in ODSs following the Montreal Protocol, we are nearing a turnaround in ozone depletion, so that the recent climate impacts of ODSs and ozone depletion are about to change sign, against a background of continued increases in greenhouse gases concentrations. Understanding and predicting these changes to the troposphere and stratosphere requires a coupled modeling perspective that is not yet practical.