On February 25, a deep brown cloud was emblazoned on the map, showing the region of Wuhan. Deep brown means: extremely high levels of nitrogen dioxide (NO2). That was in 2019. A few days ago, the satellites of NASA and the European Space Agency (ESA) collected data that resulted in a very bright sky blue – and thus a very low concentration of NO2, the toxic gas that comes from power plants, factories and heating systems and cars are ejected.
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The drastic difference could be the coronavirus outbreak in Wuhan. Or how the scientists of the UFormulate NASA’s space agency more carefully: “There is evidence that the change is at least partially related to the economic slowdown after the coronavirus outbreak.”
Using satellite data, NASA initially saw a decrease in NO2 pollution near Wuhan, which eventually spread across the country.
“This is the first time that I have seen such a dramatic decline across such a wide area for a particular event,” said Fei Liu, an air quality researcher at NASA’s Goddard Space Flight Center. At the beginning of the economic crisis in 2008, NO2 pollution had decreased in several countries, but much more slowly. The 2008 Olympic Games also had an impact on air pollution – limited around Beijing and only temporarily.
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From the end of January to the beginning of February this year – at the same time as the Covid 19 outbreak – the New Year celebrations also took place in China. Since factories and other companies are closing for this reason alone, a decrease in NO2 values can be observed regularly. However, NASA researchers assume that the decline is more than a holiday effect or a weather-related variation. In a preliminary analysis, they compared the numbers from 2005 to 2020 and found: “In 2020, NO2 levels in east and central China were significantly lower (10 to 30 percent lower) than was normally observed for this period.”
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Even after the Chinese New Year holiday period, NO2 air pollution from industry and traffic has not increased again. “This year, the reduction rate is more significant than in previous years and has taken longer,” said researcher Liu. “I’m not surprised because many cities across the country have taken steps to minimize the spread of the virus.”
In December, medical professionals in Wuhan noticed an accumulation of pneumonia cases with unknown causes – the corovirus Covid-19 was discovered. The city was quarantined, other locations in China followed, and millions were affected. Infections have now occurred in more than 50 countries.
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