The shades of grey denote the lockdown periods in 2020, moving progressively from strict (dark grey) to loose (light grey) measures. The percentages shown in red represent the reduction in 2020 compared to 2019 over the same period.
The data shows that the strongest reductions of 40–50% were seen in the first stage of the lockdown in southern Europe, specifically Spain, Italy and France. In July and August 2020, the data suggests that the concentrations are still 10% to 20% lower than pre-COVID levels.
Bas Mijling, atmospheric scientist at KNMI, comments, “Quarantine measures implemented in Berlin led to a drop of about 20% with small variations seen until August 2020. In eastern Europe, the impact of the measures has been generally less dramatic than in southern Europe, and in France, where reductions of approximately 40–50% were observed during the strict lockdowns of March and April.
“More research is currently taking place as part of ESA’s ICOVAC project, or impact study of COVID-19 lockdown measures on air quality and climate.”
Jenny Stavrakou, atmospheric scientist at BIRA-IASB, adds, “The impact of meteorology on the nitrogen dioxide observations could be significant and should not be overlooked. This is why it is necessary to analyse data over longer periods of time, to better estimate the impact of human activity on the observations.”
She continues, “For the monthly mean comparison of 2019 and 2020, we estimate an uncertainty on the COVID-19 induced reduction of around 15–20%. By comparing the reductions in satellite based data and ground-based data for different cities, we find a satisfactory agreement differences lying well within the uncertainties due to meteorological variability.”
ESA’s Copernicus Sentinel-5P Mission Manager, Claus Zehner, says, “What is really remarkable is the good agreement between the Sentinel-5P satellite data and the ground-based measurements. This demonstrates that air quality monitoring from space can contribute to regular air quality reporting in European countries, which has been only done, so far, using ground-based measurements.”