Sensitivity of tropospheric hydrogen peroxide to global chemical and climate change

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‐NO_x 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 H₂O₂ except in very low NO_x 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.