A model study of the impact of source gas changes on the stratosphere for 1850–2100

The stratospheric impacts of changing atmospheric loading of ozone depleting substances (ODSs) and the greenhouse gases (GHGs) CO2, CH4, and N2O for 1850-2100 are investigated using a two-dimensional (2D) model. Simulations with the ODSs and GHGs varied time dependently show that the 2D model simulates long term changes in stratospheric temperature, ozone, and age of air that are mostly similar to the Goddard Earth Observing System chemistry-climate model (GEOSCCM). 2D simulations with the ODSs, CO2, CH4, and N2O varied individually illustrate the relative roles of these gases in driving long term stratospheric changes. The past and future changes in temperature and age of air are dominated by the ODS and CO2 loading, with CH4 loading also important in the lower mesosphere. For ozone, the impacts due to ODS, CO2, CH4, and N2O loading all play important roles in different regions of the stratosphere. Model simulations also illustrate that much smaller stratospheric changes occur during 1850-1950 compared to the recent past and future (1950-2100). Calculations of ozone depletion potential (ODP) reveal that the impacts of N2O, CH4, and CO2 strongly depend on the time period considered. We also examine the time dependent photochemical lifetimes of N2O, CFCl3, CF2Cl2, and CCl4. Model simulations show that the lifetimes decrease by 11-13% over 1960-2100 due to changes in the Brewer-Dobson circulation, with much smaller changes (<4%) due to the changing photochemical loss rates.