A study of 26 atmospheric chemistry models compared present-day and near-future tropospheric ozone distributions, budgets, and radiative forcings. The models were used to simulate three 2030 emissions scenarios representing "optimistic," "likely," and "pessimistic" options, compared to a base year 2000 simulation. Ensemble mean changes in ozone burden between 2000 and 2030 ranged from a 5% decrease to a 15% increase, with intermodel uncertainty of ±25%. The results showed that ozone and methane changes produced radiative forcings of -50, 180, and 300 mW m⁻², compared to a CO₂ forcing of 800–1100 mW m⁻². These values highlight the importance of air pollution emissions in short- to medium-term climate forcing. The model sensitivity of ozone to climate change varied, modulating zonal mean mixing ratios by ±5 ppbv via feedback mechanisms. Climate change also reduced methane lifetime by around 4%. The ensemble mean 2000 tropospheric ozone budget indicated chemical production, chemical destruction, dry deposition, and stratospheric input fluxes of 5100, 4650, 1000, and 550 Tg(O₃) yr⁻¹, respectively. These values differ from the IPCC TAR estimates, with a 10% larger mean ozone burden and a 10% shorter mean ozone lifetime. The study also identified uncertainties in model treatments of deep tropical convection, isoprene emissions, stratosphere-troposphere exchange, biomass burning, and water vapor concentrations. The results emphasize the importance of air pollution emissions in climate forcing and the potential for stringent or lax control measures to improve or worsen future climate forcing. The study also highlights the need for further validation of ozone precursors and the importance of considering climate change in future projections.A study of 26 atmospheric chemistry models compared present-day and near-future tropospheric ozone distributions, budgets, and radiative forcings. The models were used to simulate three 2030 emissions scenarios representing "optimistic," "likely," and "pessimistic" options, compared to a base year 2000 simulation. Ensemble mean changes in ozone burden between 2000 and 2030 ranged from a 5% decrease to a 15% increase, with intermodel uncertainty of ±25%. The results showed that ozone and methane changes produced radiative forcings of -50, 180, and 300 mW m⁻², compared to a CO₂ forcing of 800–1100 mW m⁻². These values highlight the importance of air pollution emissions in short- to medium-term climate forcing. The model sensitivity of ozone to climate change varied, modulating zonal mean mixing ratios by ±5 ppbv via feedback mechanisms. Climate change also reduced methane lifetime by around 4%. The ensemble mean 2000 tropospheric ozone budget indicated chemical production, chemical destruction, dry deposition, and stratospheric input fluxes of 5100, 4650, 1000, and 550 Tg(O₃) yr⁻¹, respectively. These values differ from the IPCC TAR estimates, with a 10% larger mean ozone burden and a 10% shorter mean ozone lifetime. The study also identified uncertainties in model treatments of deep tropical convection, isoprene emissions, stratosphere-troposphere exchange, biomass burning, and water vapor concentrations. The results emphasize the importance of air pollution emissions in climate forcing and the potential for stringent or lax control measures to improve or worsen future climate forcing. The study also highlights the need for further validation of ozone precursors and the importance of considering climate change in future projections.