What Can the COVID-19 Pandemic Tell Us About the Energy Transition? A Nitrogen Dioxide and Ground-Level Ozone Study

The lockdown measures imposed in Lisbon during the COVID-19 pandemic offered an unprecedented opportunity to observe abrupt changes in tropospheric NO2 and O3 concentrations, providing information on air quality improvements in a future dominated by electric vehicles. This study used deweathering modelling to account for meteorological influences in the data, analysing pollution changes throughout the baseline (2016–2019), COVID-19 (2020), recovery (2021), and post-COVID-19 (2022) periods. In summary, significant decreases in NO2 concentrations were observed at both traffic and background locations, with reductions up to 30% during the COVID-19 year. This is similar to what would be expected in an aggressive energy transition scenario. Concentrations of O3 increased by up to 20% at traffic locations; however, background O3 concentrations remained virtually unchanged, indicating that O3 formation is not primarily driven by NO2 but possibly VOC. The findings in this paper suggest that future reductions in NO2 due to vehicle electrification are unlikely to result in considerably high regional O3 concentrations.