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AIRBORNE NITROGEN DIOXIDE PLUMMETS OVER CHINA

NASA and European Space Agency (ESA) pollution monitoring satellites have detected significant decreases in nitrogen dioxide (NO2) over China. There is evidence that the change is at least partly related to the economic slowdown following the outbreak of coronavirus.

The maps on this page show concentrations of nitrogen dioxide, a noxious gas emitted by motor vehicles, power plants, and industrial facilities.

The maps above show NO2 values across China from January 1 to January 20, 2020 (before the quarantine), and February 10 to February 25 (during the quarantine).

According to NASA scientists, the reduction in NO2 pollution was first apparent near Wuhan, but eventually spread across the country. Millions of people have been quarantined in one of the largest such actions in human history.

“This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event,” said Fei Liu, an air quality researcher at NASA’s Goddard Space Flight Center. Liu recalls seeing a drop in NO2 over several countries during the economic recession that began in 2008, but the decrease was gradual.

Scientists also observed a significant reduction around Beijing during the 2008 Olympics, but the effect was mostly localised around that city, and pollution levels rose again once the Olympics ended.

The drop in nitrogen dioxide in 2020 also coincided with Lunar New Year celebrations in China and much of Asia.

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 with the same periods in 2019 for reference.

NASA Earth Observatory images by Joshua Stevens, using modified Copernicus Sentinel 5P data processed by the European Space Agency. Story by Kasha Patel.