Coronavirus Partly Responsible For Dramatic Decrease In Nitrogen Dioxide Pollution Over China

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According to a report by NASA’s Earth Observatory, the Tropospheric Monitoring Instrument onboard the European Space Agency’s Sentinel-5 satellite and the Ozone Monitoring Instrument on NASA’s Aura satellite reveal a startling reduction in nitrogen dioxide concentrations in the atmosphere over parts of China since February 10, a few weeks after China began mandatory quarantine restrictions in several cities, beginning with Wuhan. It was the first city to report a major outbreak of COVID-19, otherwise known as the coronavirus. Starting January 23, China shut down all transportation routes into and out of Wuhan.

NO2 Pollution Over China
Image credit: NASA Earth Observatory images by Joshua Stevens, using modified Copernicus Sentinel 5P data processed by the European Space Agency.

Nitrogen dioxide is a gas emitted by gasoline and diesel powered vehicles, thermal generating plants, and industrial landfills. In other words, it is an indicator of commercial and industrial activity associated with the combustion of fossil fuels. It is normal for the concentration of NO2 to go down during the Lunar New Year celebration that takes place in many Asian countries every February. That’s when many factories close down and people spend less time commuting back and forth to work.

This year is different, however, in that NO2 levels did not go back up as they normally do after the holiday is over. The scientists theorize the difference can be accounted for by a decrease in industrial activity as a result of the coronavirus, which has forced millions of Chinese to stay home instead of going to work.

“This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event,” says Fei Liu, an air quality researcher at NASA’s Goddard Space Flight Center. Liu recalls there was a drop in nitrogen dioxide levels over several countries during the global economic slowdown that began in 2008 but that decrease was gradual. This one was sudden. “This year, the reduction rate is more significant than in past years and it has lasted longer,” she said. “I am not surprised because many cities nationwide have taken measures to minimize spread of the virus.”

There was a similar reduction around Beijing during the 2008 Olympics, but that effect was mostly localized around China’s capitol city and pollution levels rose again once the Olympics ended. “There is always this general slowdown around this time of the year,” said Barry Lefer, an air quality scientist at NASA. “Our long-term OMI data allows us to see if these amounts are abnormal and why.” Launched in 2004, OMI has been collecting global data on NO2 and various air pollutants for more than 15 years.

China NO2 polution
Image credit: NASA Earth Observatory images by Joshua Stevens, using modified Copernicus Sentinel 5P data processed by the European Space Agency.

The maps above show NO2 values over three periods in 2020: January 1-20 (before Lunar New Year), January 28-February 9 (around New Year celebrations), and February 10-25 (after the event). The 2020 values are compared to the same periods in 2019 for reference. Lefer noted that the overall values in 2020 were lower than 2019 due to new environmental regulations that China has enforced over the past few years.

What is the most important result of these numbers? Let me make a suggestion. These satellites have been providing this information continuously for 15 years, documenting how human activity is poisoning the environment. Yet nobody raises an eyebrow when this information is made public. “Ho, hum. Business is business. What can you do, huh?”

Actually, there is lots we could do. We could restructure our economic model to promote commercial and industrial processes that pollute less. That starts with making polluters pay for the damage they cause — the chronic illnesses and shortened lifespans associated with breathing in airborne crud. It begins with not excusing polluters for their crimes with the tired old excuse that the economy depends on doing violence to the environment.

If the coronavirus can teach us anything it is that we are all interconnected. What happens in China has knock on effects in Europe, North America, and everywhere else around the globe. We need to stop being oblivious to the fact that we are all part of a global community and start treating each other as brothers and sisters, to be cherished and nourished. Is that too much to ask?

[Note: NASA Earth Observatory images by Joshua Stevens, using modified Copernicus Sentinel 5P data processed by the European Space Agency.]

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Steve Hanley

Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. He is proud to be "woke" and doesn't really give a damn why the glass broke. He believes passionately in what Socrates said 3000 years ago: "The secret to change is to focus all of your energy not on fighting the old but on building the new."

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