Effects of intercontinental transport on surface ozone over the United States: Present and future assessment with a global model

Future changes in intercontinental transport (ICT) of European and Asian (EURA) pollutants can have substantial consequences on U.S. pollution. This is investigated with 27 simulations using a newly improved version of the Model for OZone And Related chemical Tracers to simulate ICT contributions to summertime U.S. surface ozone for 1999, 2049 and 2099, with future climate and emissions perturbations following the Intergovernmental Panel on Climate Change A1fi and B1 scenarios. We find that projected ICT changes are primarily affected by changes in EURA anthropogenic emissions, whose increases under A1fi lead to 3–8 ppb, 2–6 ppb due to Asian emissions increases alone, more ozone from 1999 to both 2049 and 2099 over the western U.S.; whereas EURA emissions changes under B1 lead to 0–0.7 ppb and 1–2 ppb less ozone by 2049 and 2099, respectively. Therefore global, especially Asian, emission control is important for U.S. pollution mitigation.