Stratospheric ozone depletion from future nitrous oxide increases

Abstract. We have investigated the impact of the assumed nitrous oxide (N₂O) increases on stratospheric chemistry and dynamics using a series of idealized simulations with a coupled chemistry-climate model (CCM). In a future cooler stratosphere the net yield of NO_y from N₂O is shown to decrease in a reference run following the IPCC A1B scenario, but NO_y can still be significantly increased by extra increases of N₂O over 2001–2050. Over the last decade of simulations, 50% increases in N₂O result in a maximal 6% reduction in ozone mixing ratios in the middle stratosphere at around 10 hPa and an average 2% decrease in the total ozone column (TCO) compared with the control run. This enhanced destruction could cause an ozone decline in the first half of this century in the middle stratosphere around 10 hPa, while global TCO still shows an increase at the same time. The results from a multiple linear regression analysis and sensitivity simulations with different forcings show that the chemical effect of N₂O increases dominates the N₂O-induced ozone depletion in the stratosphere, while the dynamical and radiative effects of N₂O increases are overall insignificant. The analysis of the results reveals that the ozone depleting potential of N₂O varies with the time period and is influenced by the environmental conditions. For example, carbon dioxide (CO₂) increases can strongly offset the ozone depletion effect of N₂O.