Stratospheric ozone response to a solar irradiance reduction in a quadrupled CO 2 environment

We used the Goddard Space Flight Center (GSFC) global two‐dimensional (2D) atmospheric model to investigate the stratospheric ozone response to a proposed geoengineering activity wherein a reduced top‐of‐atmosphere (TOA) solar irradiance is imposed to help counteract a quadrupled CO 2 atmosphere. This study is similar to the Geoengineering Model Intercomparison Project (GeoMIP) Experiment G1. Three primary simulations were completed with the GSFC 2D model to examine this possibility: (A) a pre‐industrial atmosphere with a boundary condition of 285 ppmv CO 2 ( piControl ); (B) a base future atmosphere with 1140 ppmv CO 2 ( abrupt4xCO2 ); and (C) a perturbed future atmosphere with 1140 ppmv CO 2 and a 4% reduction in the TOA total solar irradiance ( G1 ). We found huge ozone enhancements throughout most of the stratosphere (up to 40%) as a result of a large computed temperature decrease (up to 18 K) when CO 2 was quadrupled (compare simulation abrupt4xCO2 to piControl ). Further, we found that ozone will additionally increase (up to 5%) throughout most of the stratosphere with total ozone increases of 1–2.5% as a result of a reduction in TOA total solar irradiance (compare simulation G1 to abrupt4xCO2 ). Decreases of atomic oxygen and temperature are the main drivers of this computed ozone enhancement from a reduction in TOA total solar irradiance.