Ozone in the troposphere plays a central role in atmospheric chemistry. It is a major greenhouse gas and a harmful air pollutant to human respiratory health and vegetation. Long-term observations of ozone reveal diverse and significant trends around the world. Interplay among precursor emissions, complex non-linear chemistry, and climate determines the abundance and trends of ozone. In this session, we solicit presentations of (1) tropospheric ozone studies in association with long-term climate change, (2) studies that explore the impact of short-term climate variability (e.g. ENSO), and 3) studies that quantify the impacts of rapid changes in emissions, on the time scale of a decade (e.g. recent increase of surface ozone in China), or on the time scale of one or two years (e.g. changes observed during the COVID-19 pandemic). Analyses that range from global scale modeling to process studies at the urban and vegetation canopy scale are welcome.