Led by Loretta Mickley, this project is using the lens of oxidative capacity to better quantify the potential impacts of geoengineering on surface air quality and atmospheric composition. For example: (1) how will stratospheric aerosol injection affect the oxidative capacity of the troposphere? Here they define oxidative capacity as the tropospheric mean concentration of the hydroxy radical OH. (2) Accounting for these long-term changes in oxidative capacity, how will this method of geoengineering influence surface air quality and what are the associated health impacts? How spatially heterogeneous are these impacts? (3) Will the perturbation of tropospheric OH from geoengineering significantly affect the atmospheric lifetime of methane? OH is the main sink of methane, and a longer methane lifetime would increase the global concentration of this greenhouse gas.