Impacts of Climate Change and Global Emissions on PM2.5 and Ozone Levels in the United
States: A Sensitivity Assessment and Development of an Integrated Modeling Framework

Peter J. Adams
Department of Civil and Environmental Engineering; Carnegie Mellon
University; 5000 Forbes Ave; Pittsburgh, PA 15213
Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA

John P. Dawson
Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA
Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA

Pavan Nandan Racherla
Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA

Barry H. Lynn,
Department of Atmospheric Sciences, The Hebrew University of Jerusalem

Spyros N. Pandis
Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA
Department of Chemical Engineering, University of Patras, Patras, Greece

Future changes in climate and global pollutant emissions provide additional challenges to air quality management in the US. Changes in meteorological variables including temperature, clouds, precipitation, wind speed, circulation patterns will impact PM2.5 and ozone concentrations in the US via changes in chemical reaction and photolysis rates, gas-aerosol partitioning, dry and wet deposition, pollutant transport, and emissions of climate-sensitive species such as isoprene.
Numerous questions arise. How much will climate change affect US air quality over the next half century? How will its impacts compare to those arising from domestic emissions changes and intercontinental transport of pollution globally? Which meteorological variables and physical processes are responsible for most of the sensitivity? What are the associated uncertainties in these projections? This talk will summarize answers to these questions arising from a 4-year project undertaken by the authors using a variety of modeling tools. Atmospheric models utilized in this research include a global “unified” model of climate, ozone, and aerosols based on the GISS general circulation model, the MM5 regional meteorological model, and the PMCAMx regional chemical transport model. We have designed a research program to draw on the respective strengths of the individual models. For example, PMCAMx has been used to quantify the sensitivity
of ozone and PM2.5 to each of a full suite of meteorological variables. We have used the GISS “unified” global model to perform multi-year simulations of future air quality under a variety of realistic future scenarios of climate, domestic and international emissions. Finally, we have developed the Global-Regional Climate Air Pollution Modeling System (GRE-CAPS) by integrating the GISS, MM5, and PMCAMx models. GRE-CAPS performance has been evaluated against
present-day observations and applied to study the relative impacts of climate change, intercontinental transport, and domestic emissions on US air quality in the 2050s decade.