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

Abstract

Increasing global emissions of trace gases NO, CH 4, and CO, along with perturbations initiated by changes in stratospheric O 3 and H 2O, may cause tropospheric hydrogen peroxide (H 2O 2) levels to change. Specific scenarios of CH 4CONO emissions and global climate changes are used to predict HO 2 and H 2O 2 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 CH 4 and CO emissions continue to increase throughout the troposphere at current rates (1% yr −), there will be large increases in H 2O 2, for example, more than 100% in the urban boundary layer from 1985 to 2035. Globally, H 2O 2 will increase 22% with HO 2 increasing 8% and O 3 increasing 13%. When CH 4, 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 H 2O 2 and 18% for O 3. A global warming (with increased H 2O vapor) or stratospheric O 3 depletion superimposed on CH 4, CO and NO emissions changes will cut O 3 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 HO 2 and H 2O 2 in the atmosphere may signify a loss of gaseous oxidizing capacity in the atmosphere and an increase in aqueous-phase oxidizing capacity.