Observations indicate that the magnitude and spatial distribution of ozone pre-cursor emissions have changed substantially across the globe in recent decades. However, the impacts of these changes on surface and tropospheric and ozone are not well known, and there are substantial differences in decadal-scale trends in ozone from in situ, ozone-sonde, and satellite measurements. Understanding how tropospheric ozone has responded to emissions changes is critical for quantifying the role of economic trends and regulatory policies on air quality and, in turn, their effects on human health and ecosystems. This session solicits presentations that discuss state-of-the-science approaches for quantifying changes in global ozone precursor emissions and in surface and tropospheric ozone, using both top-down and bottom-up approaches, and for understanding the relationships between them. We also solicit presentations on how changes in air quality over the past few decades have affected human and ecosystem health.