The effectiveness of N 2 O in depleting stratospheric ozone

Recently, it was shown that of the ozone‐depleting substances currently emitted, N 2 O emissions (the primary source of stratospheric NO x ) dominate, and are likely to do so throughout the 21st century. To investigate the links between N 2 O and NO x concentrations, and the effects of NO x on ozone in a changing climate, the evolution of stratospheric ozone from 1960 to 2100 was simulated using the NIWA‐SOCOL chemistry‐climate model. The yield of NO x from N 2 O is reduced due to stratospheric cooling and a strengthening of the Brewer‐Dobson circulation. After accounting for the reduced NO x yield, additional weakening of the primary NO x cycle is attributed to reduced availability of atomic oxygen, due to a) stratospheric cooling decreasing the atomic oxygen/ozone ratio, and b) enhanced rates of chlorine‐catalyzed ozone loss cycles around 2000 and enhanced rates of HO x ‐induced ozone depletion. Our results suggest that the effects of N 2 O on ozone depend on both the radiative and chemical environment of the upper stratosphere, specifically CO 2 ‐induced cooling of the stratosphere and elevated CH 4 emissions which enhance HO x ‐induced ozone loss and remove the availability of atomic oxygen to participate in NO x ozone loss cycles.