Source: AGU Advances
Automobile emissions declined throughout much of the world following COVID stay-at-home orders in 2020 and then rebounded in 2021. Yañez et al.  measured these dynamics both by mobile lab CO2 measurements and by radiocarbon measurements of roadside plant tissues. The plants revealed a 5 ppm reduction in Los Angeles’ fossil fuel carbon dioxide levels in 2020, which was in broad agreement with the mobile lab measurements. While the temporary decline in emissions due to COVID has since passed, the methodological methods could have a more lasting role. In countries without CO2 monitoring infrastructure, further development of the method of using plants as witnesses of emissions through their radiocarbon content could aid efforts to monitor progress in decarbonization.
Citation: Yañez, C. C., Hopkins, F. M., Xu, X., Tavares, J. F., Welch, A., & Czimczik, C. I. . Reductions in California’s urban fossil fuel CO2 emissions during the COVID-19 pandemic. AGU Advances, 3, e2022AV000732. https://doi.org/10.1029/2022AV000732
—Eric Davidson, Editor, AGU Advances