Satellite images published by NASA and the European Space Agency (ESA) show a dramatic drop in levels of air pollution over China following the outbreak of the new coronavirus, which forced the shutdown of industry and transport.
Images taken by pollution monitoring satellites compare air quality between Jan. 1 and Jan. 20 with air quality between Feb. 10 and Feb. 25, and show a significant decrease in nitrogen dioxide (NO2), a toxic gas that gets into the air from the burning of fuel from vehicles, power plants and factories.
According to NASA scientists, the reduction in NO2 pollution was first apparent near Wuhan, which shut down transportation going into and out of the city, as well as local businesses by Jan. 23, in order to reduce the spread of the disease.
NASA said there is evidence that the change in air pollution is “at least partly related to the economic slowdown following the outbreak of coronavirus.”
“This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event,” research scientist Dr. Fei Liu said.
However, scientists also noticed the reduction in the toxic gas also spread across the rest of China and coincided with the Lunar New Year celebrations in January, which they said usually sees businesses and factories close from the last week of the month to celebrate the festival.
Previous observations found that air pollution generally decreases during this period before again increasing after the celebrations are over.
But while the Lunar New Year may have played a role in the recent decrease, researchers believe it is more than a holiday effect or weather-related variation.
“In a preliminary analysis, NASA researchers compared NO2 values detected by OMI in 2020 with the average amounts detected at this time of year from 2005-2019. In 2020, NO2 values in eastern and central China were significantly lower (from 10 to 30 percent lower) than what is normally observed for this time period,” they said.
Additionally, researchers have not seen a rebound in NO2 after the holiday and noted that in 2020, the reduction rate is “more significant than in past years and it has lasted longer.”
Satellite images of Wuhan, China, taken in January and February 2019 (top) and 2020 showing an absence of the usual rebound in nitrogen dioxide after the Chinese New Year. (NASA)
This is not the first time researchers have noticed such a drop in air pollution in China, noting a significant reduction around Beijing during the 2008 Olympics, as authorities closed down factories and limited automobile traffic to clear up the smog for the games. However, the effect was mostly limited to the city and its surrounds. Pollution levels increased again after the games had ended.
As of March. 1, there have been a reported 79,827 cases of the virus and 2,870 deaths in China, but experts and eyewitness accounts have indicated that the true number of cases and deaths in China is far greater than officially reported.
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