Countries across Europe are seeing a vast decline in air pollution as a result of their COVID-19 lockdown measures. 

New data, sourced by Royal Netherlands Meteorological Institute (KNMI), from the Copernicus Sentinel-5P satellite shows the reduction of air pollution over major cities in Spain, Italy and France.

The satellite images show nitrogen dioxide concentrations from 14 to 25 March 2020, compared to the monthly average of concentrations from 2019.

The images show a vast reduction in nitrogen dioxide, a gas usually emitted by power plants, cars and factories, in populated cities such as Madrid, Milan and Paris.

Henk Eskes of KNMI, explains why they used a 10-day were chosen, "The nitrogen dioxide concentrations vary from day to day due to changes in the weather. Conclusions cannot be drawn based on just one day of data alone."

"By combining data for a specific period of time, 10 days in this case, the meteorological variability partly averages out and we begin to see the impact of changes due to human activity." He added.

The Sentinel-5P satellite was built by Airbus in Britain and first launched in October 2017. It can detent the presence of many gases in the atmosphere including methane, carbon monoxide and of course, nitrogen dioxide. 

In order to reduce the spread of the COVID-19 pandemic, countries across Europe have implemented strict measures, from full lockdowns to partial lockdowns where only certain citizens can go to work.

Spain have implemented new, more stricter laws that came into force on Monday, whilst Italy and France have both been in lockdown for weeks.

The question is, will air pollution reduce further as lockdowns continue. And then if it can be continued when these measures are relaxed?