Evaluating the effects of climate warming and precursor emission changes on surface ozone air quality over coming decades: a case study for Austria

<p>Ozone production and loss in surface air is determined by ambient temperature, &#160;chemical conditions and precursor emissions. Despite efforts to abate surface ozone air pollution, the daily maximum 8-hour average ozone target value for the protection of human health &#160;is regularly exceeded at several monitoring sites in Austria especially during the warm seasons.&#160;</p> <p>Here we investigate projected changes in the surface ozone burden and effects of climate warming and changes in precursor emissions over the next decades in a series of tailored chemistry-transport model (CTM) experiments, performed with WRF-Chem and CAMx. Specifically we contrast changes in ozone air quality in decadal time slices for 2026-2035 and 2046-2055 with the recent past (2007-2016). Our CTM ensemble comprises simulations following the Representative Concentration Pathways (RCPs) 2.6, 4.5 and 8.5. Our results show a persistent large variability in ozone abundances driven by the large intra- and interannual &#160;variability in meteorological conditions. Overall we find general improvements in the surface ozone burden for low emission scenarios (RCP2.6 and RCP4.5) driven by ambitious NOx controls. In contrast under RCP8.5 we find, on the one hand an increase in the frequency of non-attainment days and on the other a shift in the prime ozone season from summer towards spring. These increases are driven by both a climate penalty and changes in the chemical production regime (NOx vs. VOC limitation) and increasing methane and ozone backgrounds. Furthermore, we investigate impacts of projected ozone changes on human health at the municipal level in Austria.</p>