Frank Dentener, Lisa Emberson, stefano galmarini, Giovanni Capelli, Anisoara Irimescu, Denis Mihailescu, Rita Van Dingenen, Maurits van den Berg

We suggest that the unprecedented and unintended decrease of emissions of air pollutants during the COVID-19 lockdown in 2020 could lead to declining seasonal ozone concentrations, and positive impacts on crop yields. An initial assessment of the potential effects of COVID-19 emission reductions was made using a set of six scenarios that variously assumed annual European and global emission reductions of 30 % and 50 % for the energy, industry, road transport and international shipping sectors, and 80 % for the aviation sector. The greatest ozone reductions during the growing season reached up to 12 ppb over crop growing regions in Asia and up to 6 ppb in North America and Europe for the 50 % global reduction scenario. In Europe, ozone responses are more sensitive to emission declines in other continents, international shipping and aviation than to emissions changes within Europe. We demonstrate that for wheat the overall magnitude of ozone precursor emission changes could lead to yield improvements between 2 % and 8 %. The expected magnitude of ozone precursor emission reductions during the Northern Hemisphere growing season in 2020 presents an opportunity to test and improve crop models and experimentally-based exposure response relationships of ozone impacts on crops, under real-world conditions.