NASA says nitrogen dioxide emissions have dropped 20% due to lockdown

The coronavirus lockdown led to an overall reduction of 20% in the amount of nitrogen dioxide released into the atmosphere between February and June.

The NASA 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 it is 300 times more potent as a contributor to global warming.

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

The drop in concentration was greater in cities, with NO2 reductions of between 20 and 60% in 50 of the 61 metropolises analyzed.

Previous studies indicate that since the easing of the first wave of coronavirus restrictions, air pollution has increased again as people have started to travel more.

“We all knew the lockdowns were going to have an impact on air quality,” said lead author Christoph Keller at NASA’s Goddard Space Flight Center in Maryland.

“It also quickly became clear that it was going to be difficult to quantify how much of this change is related to foreclosure measures, versus general seasonality or variability in pollution.

NASA compared the 2020 ground average data to the multi-year average, taking into account natural variations in weather and atmospheric circulation.

Researchers took all the pre-existing data and modeled what the 2020 emissions would have looked like had the coronavirus pandemic not taken place.

This was then compared to the actual measurements.

“In some ways, I was surprised how much he dropped,” Dr. Keller said.

“Many countries have already done a very good job of lowering their nitrogen dioxide concentrations over the past decades due to clean air regulation, but what our results clearly show is that it There is still a significant contribution induced by human behavior.

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

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

This is due to the strict lockdown which was quickly put in place, which prohibited any form of movement outside the city.

A 60% decrease in Milan and 45% in New York followed shortly thereafter, as their local restrictions took effect after their emergence as a viral epicenter.

“Sometimes you might even see nitrogen dioxide decrease before official policies are in place,” said co-author Emma Knowland of the NASA Universities Space Research Association (USRA).

“ People were probably reducing their transit because discussions about the COVID-19 threat were already happening before we were told to shut down. ”

In London, there was no noticeable change in NO2 concentrations until March, when they were 14.2% lower than expected.

In April, that figure climbed to more than a third, or 34.2% less than expected, and May was similar, with a reduction of 32.7%.

Although this, along with previous studies, has found air pollution to have dropped amid the coronavirus lockdown, it is on the rise again.

The Clean Air and Energy Research Center (CREA) discovered in June found that air pollution levels in London, Paris, Rome and other European cities had all picked up in the wake of the easing of coronavirus lockdown.

NO2 readings hit a low in the UK capital in late April amid the county’s lockdown measures.

But the city saw a 34% increase in NO2, from the 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.