The decline in economic activity in China is now visible from space. Many experts had already observed a reduction in gas emissions in the country, but now the satellites of the European Copernicus agency have registered an unusual drop in nitrogen dioxide levels. The data was collected by NASA's ground observation team, SIA reports referring to Euronews.
Air quality experts have focused their observations on nitrogen dioxide (NO2), which is only detected near the sources of emissions: mainly the burning of fossil fuels from road traffic and industry. In the midst of the Chinese New Year holiday period, it was difficult to know if it was a reduction linked to the restrictions of the coronavirus epidemic or simply the "truce" of activity of the holidays.
Then also, the meteorological factor has a lot of influence on the concentrations of this gas. To avoid it as much as possible, they have measured on a longer period of a dozen days. Now scientists are sure that the activity has not resumed as usual after the New Year holidays.
This trend is confirmed in other big cities. In the second half of February, there was hardly no activity. Liu commented that there was a fall of NO2 in several countries during the 2008 crisis, but it was a gradual phenomenon. He also cited a decrease in Beijing during the Olympic Games, although pollution levels recovered after the Olympics ended.
Regarding the typical fall of the New Year holidays, Fei Liu explains that "this year, the reduction is more significant than in previous years and has lasted longer," he said. To perform these measurements, NASA's air quality experts have used the Ozone Monitoring Instrument (IMO) of NASA's Aura mission.
Launched in 2004, this mission has been collecting global data on NO2 and various air pollutants for more 15 years. Experts have also used data from the Sentinel 5 satellite of the European Copernicus ground observation program.
Researcher Simon Gascoin has put it into graphics. In Beijing and Hubei province, emissions have clearly fallen in February, although they are beginning to recover. This visualisation created in mid-February by scientists from the Finnish meteorological agency also shows an important difference in NO2 emissions.
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