Perturbations to tropospheric oxidants, 1985-2035: 2. Calculations of hydrogen peroxide in chemically coherent regions

Increasing global emissions of trace gases NO, CH₄, and CO, along with perturbations initiated by changes in stratospheric O₃ and H₂O, may cause tropospheric hydrogen peroxide (H₂O₂) levels to change. Specific scenarios of CH₄CONO emissions and global climate changes are used to predict HO₂ and H₂O₂ changes from 1985 to 2035 in a one-dimensional model that simulates different chemically coherent regions (e.g. urban, non-urban continental and marine mid-latitudes; marine and continental low latitudes). If CH₄ and CO emissions continue to increase throughout the troposphere at current rates (1% yr^-), there will be large increases in H₂O₂, for example, more than 100% in the urban boundary layer from 1985 to 2035. Globally, H₂O₂ will increase 22% with HO₂ increasing 8% and O₃ increasing 13%. When CH₄, CO and NO emissions are specified on a regionally varying basis and are parameterized for high and low potential growth rates, globally averaged increases in surface concentrations are 12% for H₂O₂ and 18% for O₃. A global warming (with increased H₂O vapor) or stratospheric O₃ depletion superimposed on CH₄, CO and NO emissions changes will cut O₃ increases but add to peroxide, increasing levels as much as 150% above present day in some regions. Both globally uniform and region-specific scenarios predict a 10-15% loss in global OH from 1985 to 2035. Thus, conversion of OH to HO₂ and H₂O₂ in the atmosphere may signify a loss of gaseous oxidizing capacity in the atmosphere and an increase in aqueous-phase oxidizing capacity.