NASA says nitrogen dioxide emissions fell by 20% due to the blockade

The coronavirus blockade led to a 20% global reduction in the amount of nitrogen dioxide emitted into the atmosphere between February and June.

NASA’s analysis looked at the amount of greenhouse gases produced at 5,756 sites in 46 countries.

Nitrogen dioxide (NO2) is less common than carbon dioxide, but is 300 times more potent as a contributor to global warming.

Nitrogen dioxide is an air pollutant produced mainly by the combustion of fossil fuels, the main emitters of which are vehicles and industry.

The drop in concentration was greatest in cities, with NO2 drops of between 20 and 60 percent observed in 50 of the 61 metropolises analyzed.

Previous studies indicate that since the first wave of coronavirus restrictions were eased, air pollution has risen again as people have started traveling more.

In the photo, a graph showing the difference between observed NO2 and the predicted level based on past years. The red dashed line indicates when the spring lock has taken effect. It shows a drop in air pollution of more than a third immediately after the introduction of the restrictions

In the photo, the NO2 levels in London for more than two years. The block is indicated by the shaded gray area

In the photo, six NASA maps focusing on Wuhan reveal the nitrogen dioxide concentration in three periods, including before Lunar New Year, during celebrations, and after celebrations in 2019 and 2020.

Britain’s capital has experienced a nearly 60% reduction in air pollution since the start of the coronavirus lockdown in spring

“We all knew that the blocks would impact air quality,” said lead author Christoph Keller of NASA’s Goddard Space Flight Center in Maryland.

“It was also soon clear that it would be difficult to quantify how much of that change was related to the blocking measures, relative to general seasonality or pollution variability.”

NASA compared the average data on the ground from 2020 to the multi-year average, taking into account the natural variation of weather and atmospheric circulation.

The researchers took all the pre-existing data and modeled what 2020 emissions would have been like had the coronavirus pandemic not occurred.

This was then compared with the actual measurements.

“In a way, I was surprised at how much he fell,” said Dr. Keller.

“Many countries have already done a great job lowering their nitrogen dioxide concentrations over the past few decades thanks to clean air regulations, but what our results clearly show is that there is still a significant contribution driven by human behavior.” .

NASA captured the lighting changes in Jianghan District, a commercial part of Wuhan, after authorities suspended travel and placed restrictions on other activities, such as social gatherings. The two images were taken 16 nights apart

In the photo, cyclists meander across a deserted Westminster Bridge on March 24, the day after the blockade was announced

Observational data (solid line) reveal that Wuhan experienced a 60% reduction in NO2 from the expected value (dashed line) for February and March and Milan (pictured) saw a similar decrease (the gray area represents the block)

Wuhan, the Chinese city that is home to more people than London (11 million) was the initial site of the SARS-CoV-2 outbreak.

As a result, it was the first place to show a marked decrease in air pollution around the February period, recording a number that was 60% lower than expected.

This is due to the rapidly implemented strict blockade, which banned all forms of travel outside the city.

Shortly thereafter, a 60% decrease in Milan and 45% in New York followed, as local restrictions came into effect following their emergence as a viral epicenter.

“Sometimes you could even see a decrease in nitrogen dioxide before official policies went into effect,” said co-author Emma Knowland with NASA’s Universities Space Research Association (USRA).

“People were probably reducing transit because there was talk of the COVID-19 threat even before we were actually told to shut down.”

For London, there was no noticeable change in NO2 concentrations until March, when it was 14.2% below the expected level.

In April, this figure rose to more than a third, to 34.2% below forecast, and May was similar, with a reduction of 32.7%.

Although this, as well as previous studies, found that air pollution decreased during the coronavirus lockdown, it is on the rise again.

The Center for Energy and Clean Air Research (CREA) discovered in June found that air pollution levels in London, Paris, Rome and other European cities have all resurfaced following the easing of coronavirus lockdowns .

NO2 readings reached a low in the UK capital around the end of April in the midst of the county lockdown measures.

But the city recorded a 34% increase in NO2 from its lowest air quality reading during the lockdown to a June measurement.

Toxic NO2 in the air, which is linked to respiratory problems and inflammatory diseases, reached a low of around 20 µg / m3 at the end of April, CREA said.

CREA data shows a decline in NO2 levels in London which becomes particularly pronounced after the nationwide blockade measures on 24 March. NO2 levels reached a low of around 20 micrograms per cubic meter (µg / m3) in late April before steadily rising