Source: AGU Advances
Ozone in the free troposphere has increased across the Northern Hemisphere since the mid-1990s, up until 2020. Chang et al.  examine the association between the COVID-19 economic downturn and the observed anomalies in the 2020 tropospheric ozone above Europe and western North America, along with the resulting effect on long-term trends. The team developed a statistical framework to better quantify regional scale ozone anomalies throughout the depth of the troposphere and stratosphere, by combining multiple sources of vertical proﬁle records, such as ozonesonde, lidar, and commercial aircraft data. The authors show that regional anomalies, and their associated estimation uncertainty, can be consistently and systematically quantiﬁed. Their findings show that the positive 1994-2019 ozone trends above Europe and western North America are diminished when including the large negative anomalies in 2020. Further, 2020 is the only year in which both regions show coincident and profound negative anomalies since the benchmark year of 1994.
Citation: Chang, K-L., Cooper, O., Gaudel, A., Allaart, M., Ancellet, G., Clark, H., et al. . Impact of the COVID-19 economic downturn on tropospheric ozone trends: an uncertainty weighted data synthesis for quantifying regional anomalies above western North America and Europe. AGU Advances, 3, e2021AV000542. https://doi.org/10.1029/2021AV000542
—Donald Wuebbles, Editor, AGU Advances