Recent satellite observations show a significant decrease in airborne nitrogen dioxide over China. Nitrogen dioxide (NO₂) is a pollutant gas emitted by vehicles, power plants and industrial facilities. Scientists say there is evidence to show that the decline is at least, in part, a result of the economic slowdown due to the outbreak of coronavirus.
Pollution-monitoring satellites operated by both NASA and the European Space Agency track the concentration of gases in the troposphere (lower level of the atmosphere). Scientists first observed the cut in NO₂ levels near Wuhan before the declination became apparent country-wide.
IN DEPTH: According to the Environmental Protection Agency, nitrogen dioxide interacts with water, oxygen and other chemicals in the atmosphere to form acid rain and haze, while also contributing to nutrient pollution in the ocean. Breathing air with a high concentration of NO₂ can also lead to coughing, wheezing, difficulty breathing and/or respiratory issues in humans.
The significant reduction in NO₂ is said to be unlike previous drops, with January-February 2020’s numbers more pronounced and longer-lasting. By comparison, other events that have also resulted in lower NO₂ concentrations include the 2008 economic recession and the annual Lunar New Year… both coinciding with a general slowdown of businesses and factories in China. But NASA researchers say the Lunar New Year is typically followed by an increase once the holiday is over… and there has been no sign of a returned increase this year. (More on this below.)
Scientists have also compared current NO₂ levels with the 2005-2019 average in eastern and central China, finding that this year’s levels were significantly lower by 10%-30% than what is normally observed for the time period.
IN DEPTH: The 2020 Lunar New Year may have played a small part in the lowering of the country’s NO₂ levels, but researchers still believe the decrease is an effect of a bigger influence. This is evident when comparing three periods in 2019 vs 2020 — January 1st-20th (before Lunar New Year), January 28th-February 9th (during Lunar New Year) and February 10th-25th (after Lunar New Year):
It is evident by the maps above that there is a notable decrease in all three periods in 2020. While some scientists say this is linked to the spread of coronavirus and the majority shutdown of China’s factories / transportation / industries, etc. .. others attribute this year’s decline to new environmental regulations enforced over the past few years. Further analysis is needed.
For more information, visit the Earth Observatory link here.