06/30/2011
Future Projections of Aerosols and Ozone Indicate General Improvement in Air Quality
Summary
Fossil fuel combustion generates greenhouse gases, such as carbon dioxide, that contribute to warming the climate, as well as particles and ozone precursors. Particles and ozone affect both climate and air quality. In this DOE-supported study, researchers present simulation results for future pollution (years 2000 to 2100) in a chemistry-climate model. Four different emissions scenarios for different energy futures are considered, ranging from reduced to increased carbon dioxide emissions. These simulations focused on changes in atmospheric composition and associated environmental parameters, such as nitrogen deposition. The study showed that tropospheric ozone is projected to decrease between 2000 and 2100 for all cases except for the case with the largest increase in greenhouse gases, with variations in methane contributing strongly to this spread. Surface ozone in 2100 is projected to change little compared to its 2000 distribution, with a smaller impact compared to previous (high emission scenario) estimates. In addition, globally-averaged stratospheric ozone (the ozone hole) is projected to recover at or beyond pre-1980 levels. Anthropogenic aerosols, as well as sulfate deposition, are projected to strongly decrease in the 21st century, due to decreased emissions. However, nitrogen deposition is projected to increase over certain regions because of the projected increase in ammonia emissions. The study suggests that while short-lived species such ozone (which modestly warms the lower atmosphere) and aerosols (which currently have a strong cooling effect) are expected to be reduced due to implementation of air quality standards, warming from greenhouse-gas build-up will have a more dominant role in future climate change.
References
Lamarque, J.-F., G. P. Kyle, M. Meinshausen, K. Riahi, S. J. Smith, D. P. van Vuuren, A. Conley, F. Vitt. 2011. “Global and Regional Evolution of Short-Lived Radiatively-Active Gases and Aerosols in the Representative Concentration Pathways,” Climatic Change 109, 191–212. DOI 10.1007/s10584-011-0155-0.