Impacts of Potential CO₂‑Reduction Policies on Air Quality in the United States

Impacts of emissions changes from four potential U.S. CO₂ emission reduction policies on 2050 air quality are analyzed using the community multiscale air quality model (CMAQ). Future meteorology was downscaled from the Goddard Institute for Space Studies (GISS) ModelE General Circulation Model (GCM) to the regional scale using the Weather Research Forecasting (WRF) model. We use emissions growth factors from the EPAUS9r MARKAL model to project emissions inventories for two climate tax scenarios, a combined transportation and energy scenario, a biomass energy scenario and a reference case. Implementation of a relatively aggressive carbon tax leads to improved PM_2.5 air quality compared to the reference case as incentives increase for facilities to install flue-gas desulfurization (FGD) and carbon capture and sequestration (CCS) technologies. However, less capital is available to install NO<i>_X</i> reduction technologies, resulting in an O₃ increase. A policy aimed at reducing CO₂ from the transportation sector and electricity production sectors leads to reduced emissions of mobile source NO_<i>X</i>, thus reducing O₃. Over most of the U.S., this scenario leads to reduced PM_2.5 concentrations. However, increased primary PM_2.5 emissions associated with fuel switching in the residential and industrial sectors leads to increased organic matter (OM) and PM_2.5 in some cities