Fig. 3.
Daily global ground-level (a) PM2.5, (b) O3, and (c) NO2 mean concentrations across all stations globally (N = 380) from the January 1, 2020 (Day of the Year, DOY = 1) to the June 28, 2020 (DOY = 180). The red line indicates the concentration of pollutants in 2020 (with trend line in black), while the blue line indicates the average concentration of pollutants in the baseline (2015–2019). The vertical black dashed line shows the onset of Wuhan's lockdown (January 23, 2020) and the red dashed line shows the average onset of the global lockdown (March 10, 2020) as identified in this analysis. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)