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From The Economist:
One example of pollution falling is that satellites looking down on China's large cities have witnessed a dramatic drop since January in levels of nitrogen dioxide, a gas generated by machinery such as internal-combustion engines. This fall coincides with the imposition of a countrywide quarantine, travel restrictions, and the shutting down of power stations and factories. Nitrogen dioxide causes respiratory problems. A drop in its levels therefore brings benefits. The concentration of another pulmonary irritant-fine soot particles-was also lower in those cities, by 20-30%, in February of this year compared with levels in the previous three years.
Clearing the air
Similar patterns have shown up elsewhere, as the virus spreads and lockdowns follow. Satellite data from Italy reveal a marked decline in nitrogen-dioxide concentrations, particularly in the Po valley, the original focus (see article) of the country's epidemic, and where Italy's shelter-at-home rules were first imposed. South Korea also saw a drop, starting in mid-February. And in New York City, data collected by TomTom, a gps-navigation firm, show peak-hour traffic down between 13.5% and 26%. Not surprisingly, carbon-monoxide levels in the city are half those during the corresponding period last year, according to researchers at Columbia University.
Drops like these, in pollutants that are directly harmful to human health, would be expected to be matched by falling emissions of those more-subtly harmful pollutants, the greenhouse gases produced by human activity. And the team at Columbia did indeed find that carbon-dioxide concentrations over New York have fallen. They dropped by 8-10% this month compared with March 2019. In China, meanwhile, industrial shutdowns are estimated to have caused a 25% drop in emissions of CO2 in February, compared with the same month in 2019.
One example of pollution falling is that satellites looking down on China's large cities have witnessed a dramatic drop since January in levels of nitrogen dioxide, a gas generated by machinery such as internal-combustion engines. This fall coincides with the imposition of a countrywide quarantine, travel restrictions, and the shutting down of power stations and factories. Nitrogen dioxide causes respiratory problems. A drop in its levels therefore brings benefits. The concentration of another pulmonary irritant-fine soot particles-was also lower in those cities, by 20-30%, in February of this year compared with levels in the previous three years.
Clearing the air
Similar patterns have shown up elsewhere, as the virus spreads and lockdowns follow. Satellite data from Italy reveal a marked decline in nitrogen-dioxide concentrations, particularly in the Po valley, the original focus (see article) of the country's epidemic, and where Italy's shelter-at-home rules were first imposed. South Korea also saw a drop, starting in mid-February. And in New York City, data collected by TomTom, a gps-navigation firm, show peak-hour traffic down between 13.5% and 26%. Not surprisingly, carbon-monoxide levels in the city are half those during the corresponding period last year, according to researchers at Columbia University.
Drops like these, in pollutants that are directly harmful to human health, would be expected to be matched by falling emissions of those more-subtly harmful pollutants, the greenhouse gases produced by human activity. And the team at Columbia did indeed find that carbon-dioxide concentrations over New York have fallen. They dropped by 8-10% this month compared with March 2019. In China, meanwhile, industrial shutdowns are estimated to have caused a 25% drop in emissions of CO2 in February, compared with the same month in 2019.
