EGU21-10636, updated on 16 Jan 2024
EGU General Assembly 2021
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Global Impacts of COVID-19 Lockdowns on Short-Lived Climate Forcers: Highlights from a Critical Review

Georgios Gkatzelis1, Jessica Gilman2, Steven Brown2, Henk Eskes3, Rita Gomes1, Anne Lange1, Brian McDonald2, Jeff Peischl2,4, Andreas Petzold1, Chelsea Thompson2,4, and Astrid Kiendler-Scharr1
Georgios Gkatzelis et al.
  • 1IEK-8: Troposphere, Forschungszentrum Jülich GmbH, Jülich, Germany
  • 2NOAA Chemical Sciences Laboratory, Boulder, Colorado, United States
  • 3Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands
  • 4Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado, United States

The coronavirus-19 (COVID-19) pandemic led to government interventions to limit the spread of the disease that are unprecedented in the last decades. Stay at home orders and other measures led to sudden decreases in atmospheric emissions, most visibly from the transportation sector. We present a review of the current knowledge and understanding of the influence of these emission reductions on atmospheric pollutants concentration and notably air quality with a focus on NO2, PM2.5, and O3 based on more than 200 papers utilizing observations from ground-based and satellite remote sensing instruments. We use the government stringency index as an indicator for the severity of lockdown measures and show how key air pollutants change as the stringency index increases. Changes in NO2 and PM2.5 mass concentration are well-studied globally. The observed decrease of NO2 with increasing stringency index is in general agreement with emission inventories that account for the lockdown. Due to the important influence of atmospheric chemistry on O3 and PM2.5 concentrations, their responses may not be linear with respect to primary pollutants. At most sites, we found O3 increased, whereas PM2.5 decreased slightly, with increasing stringency index. Changes in the PM2.5 composition are found to be understudied and not well-quantified so far. We highlight future research needs for utilizing the emerging data sets covering a full seasonal cycle as a preview of a future state of the atmosphere in a world with targeted permanent reductions of emissions. Finally, we emphasize the need to account for the effects of meteorology, long-term trends, and atmospheric chemistry when determining the lockdown effects on pollutant concentrations, especially on PM2.5.

How to cite: Gkatzelis, G., Gilman, J., Brown, S., Eskes, H., Gomes, R., Lange, A., McDonald, B., Peischl, J., Petzold, A., Thompson, C., and Kiendler-Scharr, A.: The Global Impacts of COVID-19 Lockdowns on Short-Lived Climate Forcers: Highlights from a Critical Review, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10636,, 2021.


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