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A one‐dimensional photochemical model has been used to calculate future changes in tropospheric O 3 and OH due to CO/NO x /CH 4 emissions and to possible changes in stratospheric O 3 and tropospheric H 2 O. Perturbations are simulated for various chemically coherent regions (e.g., urban and continental mid‐latitudes, and marine and continental low latitudes) from 1985 to 2035. Estimates of global changes in O 3 and OH are made by averaging over these regions. Two types of scenarios are simulated. “Global” scenarios assume that increases of CH 4 and CO continue at current rates in all regions. A second set of scenarios, based on an analysis Of CH 4 , CO, and NO budgets in each region, assumes that emissions will be controlled in some regions and not in others. Both global and region‐specific scenarios predict a global tropospheric O 3 increase of ∼10–15% from 1985 to 2035 with OH decreasing 10–15%. In the regionally varying scenarios, O 3 will increase in some regions and decrease in others; for examples in regions of rapid CH 4 and CO increase, growth in boundary layer O 3 may be as high as 40%. Calculations that assume stratospheric O 3 depletion and climate warming from 1985 to 2035 show near cancellation of the tropospheric O 3 enhancement and OH loss. All scenarios of CH 4 /CO/NO changes considered in this study imply a 1–1.5% increase in total ozone from 1985 to 2035, assuming that tropospheric O 3 is 10% of the total O 3 column. This may complicate detection of stratospheric O 3 change by monitoring of total O 3 .
Thompson et al. (Wed,) studied this question.