Ozone air quality and radiative forcing consequences of changes in ozone precursor emissions

Abstract

Changes in emissions of ozone (O(3)) precursors affect both air quality and climate. We first examine the sensitivity of surface O(3) concentrations (O(3)(srf)) and net radiative forcing of climate (RF(net)) to reductions in emissions of four precursors - nitrogen oxides (NO(x)), non-methane volatile organic compounds, carbon monoxide, and methane (CH(4)). We show that long-term CH(4)-induced changes in O(3), known to be important for climate, are also relevant for air quality; for example, NOx reductions increase CH(4), causing a long-term O(3) increase that partially counteracts the direct O(3) decrease. Second, we assess the radiative forcing resulting from actions to improve O(3) air quality by calculating the ratio of Delta RF(net) to changes in metrics of O(3)srf. Decreases in CH(4) emissions cause the greatest RFnet decrease per unit reduction in O(3)srf, while NOx reductions quality, therefore, CH(4) abatement best reduces climate forcing.