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Published November 16, 2021 | Published + Supplemental Material
Journal Article Open

Societal shifts due to COVID-19 reveal large-scale complexities and feedbacks between atmospheric chemistry and climate change

Abstract

The COVID-19 global pandemic and associated government lockdowns dramatically altered human activity, providing a window into how changes in individual behavior, enacted en masse, impact atmospheric composition. The resulting reductions in anthropogenic activity represent an unprecedented event that yields a glimpse into a future where emissions to the atmosphere are reduced. Furthermore, the abrupt reduction in emissions during the lockdown periods led to clearly observable changes in atmospheric composition, which provide direct insight into feedbacks between the Earth system and human activity. While air pollutants and greenhouse gases share many common anthropogenic sources, there is a sharp difference in the response of their atmospheric concentrations to COVID-19 emissions changes, due in large part to their different lifetimes. Here, we discuss several key takeaways from modeling and observational studies. First, despite dramatic declines in mobility and associated vehicular emissions, the atmospheric growth rates of greenhouse gases were not slowed, in part due to decreased ocean uptake of CO₂ and a likely increase in CH₄ lifetime from reduced NO_x emissions. Second, the response of O₃ to decreased NO_x emissions showed significant spatial and temporal variability, due to differing chemical regimes around the world. Finally, the overall response of atmospheric composition to emissions changes is heavily modulated by factors including carbon-cycle feedbacks to CH₄ and CO₂, background pollutant levels, the timing and location of emissions changes, and climate feedbacks on air quality, such as wildfires and the ozone climate penalty.

Additional Information

© 2021 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND). Edited by Akkihebbal R. Ravishankara, Colorado State University, Fort Collins, CO, and approved September 29, 2021 (received for review June 10, 2021). We thank the Keck Institute for Space Studies for organizing and supporting the study "COVID-19: Identifying Unique Opportunities for Earth System Science" that led to the writing of this manuscript. We also acknowledge the use of data from the Port of Oakland and Port of LA website, Apple mobility data, and US EIA electricity-use data. We also thank Charles Carter for his artwork in Fig. 1. We thank the TCCON science team for their effort in providing data. Support for operation of the Park Falls TCCON site is provided by NASA. The Lauder TCCON programme is funded by NIWA (National Institute of Water & Atmospheric Research Ltd.) through Aotearoa New Zealand's Ministry of Business, Innovation and Employment's Strategic Science Investment Fund. The views expressed in this manuscript are solely those of the authors and do not necessarily reflect those of the South Coast Air Quality Management District. A portion of this research was carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under a contract with NASA. This work was supported by NASA Grant NNX17AE15G (to J.L.L. and P.O.W.), NASA Carbon Monitoring System Grant 80NSSC20K0006 (to A.C.), NASA Grant 80NSSC18K0689 (to D.K.H. and H.C.), NASA Aura Science Team Program 19-AURAST19-0044 (to K.M. and K.W.B.), NASA Grant 80NSSC20K1122 (to D.L.G. and S.A.), NASA Grant 80NSSC21K0508 (to R.V.M.), NSF RAPID Grant 2030049 (to K.B.), NSF Grants OCE-1752724 and OCE-1948664 (to N.S.L.), and NSF Grant OCE-1948624 (to G.A.M.). A.J.T. was supported as a Miller Fellow with the Miller Institute for Basic Research in Science at the University of California Berkeley. K.R.G. was supported by Northern Arizona University startup funds. C.E.I. was supported by the University of California Institute of Transportation Studies. S.P.S. and Z.-C.Z. were supported by the California Air Resources Board, NASA Science Mission Directorate/Earth Science Division, and JPL Earth Science and Technology Directorate. Y.L.Y. was supported in part by JPL OCO-2 Grant JPL.1613918 (to the California Institute of Technology). J.L. was supported by the NASA OCO science team program. Data Availability: GEOS-Chem Model Output data have been deposited in Zenodo (https://zenodo.org/record/4849416) (71). Publicly available datasets are listed along with data generated from this study and stored in public-facing repositories in SI Appendix, Table S1. Emissions data for Figs. 3 and 9 are given in SI Appendix, Table S2. Data for the OPE values in Fig. 7 are given in SI Appendix, Table S4. Emissions and OPE data are also included as Datasets S1 and S2. In addition, previously published data (1, 2, 13, 25, 29–31, 35, 72–84) were used for this work. Author contributions: J.L.L., K.B., K.W.B., A.C., B.E.C., H.L.F., D.K.H., J.K., E.A.K., Z.L., K.M., A.J.T., S.A., J.A., H.C., D.C., J.d.G., A.E., J.C.F., D.L.G., K.R.G., S.H., F.H., C.E.I., D.B.A.J., J.L., N.S.L., R.V.M., G.A.M., L.O., B.P., M.R., S.P.S., N.S., Y.L.Y., and Z.-C.Z. performed research; J.L.N., D.S., and P.O.W. designed research; J.L.L., J.L.N., D.S., P.O.W., K.B., K.W.B., A.C., B.E.C., H.L.F., D.K.H., J.K., E.A.K., Z.L., K.M., A.J.T., S.A., J.A., H.C., D.C., J.d.G., A.E., J.C.F., D.L.G., K.R.G., S.H., F.H., C.E.I., D.B.A.J., J.L., N.S.L., R.V.M., G.A.M., L.O., B.P., M.R., S.P.S., N.S., Y.L.Y., and Z.-C.Z. analyzed data; J.L.L., J.L.N., D.S., and P.O.W. wrote the paper; and K.B., K.W.B., A.C., B.E.C., H.L.F., D.K.H., J.K., E.A.K., Z.L., K.M., A.J.T., S.A., J.A., H.C., D.C., J.d.G., A.E., J.C.F., D.L.G., K.R.G., S.H., F.H., C.E.I., D.B.A.J., J.L., N.S.L., R.V.M., G.A.M., L.O., B.P., M.R., S.P.S., N.S., Y.L.Y., and Z.-C.Z. edited and approved the manuscript draft. The authors declare no competing interest. This article is a PNAS Direct Submission. This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2109481118/-/DCSupplemental.

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Additional details

Created:
September 15, 2023
Modified:
October 23, 2023