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.
At the end of 2019, medical professionals in Wuhan, China, were treating dozens of pneumonia cases that had an unknown source. Days later, researchers confirmed the illnesses were caused by a new coronavirus (COVID-19). By Jan. 23, 2020, Chinese authorities had shut down transportation going into and out of Wuhan, as well as local businesses, in order to reduce the spread of the disease. It was the first of several quarantines set up in the country and around the world.
The accompanying map shows concentrations of nitrogen dioxide—a noxious gas emitted by motor vehicles, power plants and industrial facilities—across China from Jan. 1-20, 2020 (before the quarantine) and Feb. 10-25, 2020 (during the quarantine). The data were collected by the Tropospheric Monitoring Instrument (TROPOMI) on ESA’s Sentinel-5 satellite. A related sensor, the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite, has been making similar measurements.
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. As of Feb. 28, 2020, the virus had been detected in at least 56 countries.
Image Credit: NASA Earth Observatory images by Joshua Stevens, using modified Copernicus Sentinel 5P data processed by the European Space Agency.