The sensitivities of tropospheric HO2 and hydrogen peroxide (H2O2) levels to increases in CH4, CO and NO emissions and to changes in stratospheric O3 and tropospheric O3 and H2O have been evaluated with a one-dimensional photochemical model. Specific scenarios of CH4-CO-NOx emissions and global climate changes are used to predict HO2 and H2O2 changes between 1980 and 2030. Calculations are made for urban and nonurban continental conditions and for low latitudes. Generally, CO and CH4 emissions will enhance H2O2 (as OH is converted to HO2); NO emissions will suppress HO except in very low NOx regions. A global warming (with increased H2O vapor) or stratospheric O3 depletion will add to H2O2. Hydrogen peroxide increases from 1980 to 2030 could be 100% or more in the urban boundary layer.

Increases in CH4, CO and O3 that have occurred in the industrial era (since 1800) have probably produced temporal increases in background HO2 and H2O2. It might be possible to use H2O2 in ice cores to track these changes. Where formation of sulfuric acid in cloudwater and precipitation is oxidant limited, H2O2 and HO2 increases could be contributing to increases in acid precipitation. ¿ American Geophysical Union 1989