Mapping Changes in Air Pollution During the Coronavirus Pandemic

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One phenomenon that is appearing globally due to the coronavirus (COVID-19) outbreak is air pollution, perhaps the first time in decades in some places, has dropped substantially. Some countries that had to routinely issue air quality alerts have not done so for multiple months now. Satellite imagery also confirms many countries are seeing a strong downward trend in air pollution, at least for now.

Drops in Nitrogen Dioxide During the Coronavirus Outbreak

When China was first hit by the coronavirus, and as it became severe in January, air pollution began to substantially decline. In Wuhan itself, a city with a high degree of air pollution, remote sensing analysis of pollutant levels provided by European Space Agency’s Sentinel-5P showed nitrogen dioxide (NO2)  at levels of a pre-industrial society, with no clear measurable reading of the pollutant for over two months.

Recently released results have confirmed that not only China but now throughout Europe, large drops of NOis evident based on measurements from the Sentinel-5P recent data. This decline is dramatic in Italy, South Korean, Spain, and China, but it is also evident in the UK and other countries as they begin to restrict movement.[1] In fact, some have begun to see a sort of silver lining with this pandemic; it many now force a stronger look at pollution reduction after the pandemic. With working at home and other remote working options becoming available, and factories begining to adjust to new ways to keep supplies up, there is a chance that lessons learned from the coronavirus could be translated to life after the pandemic, with countries adapting better than prior to the outbreak.[2]

Maps showing NO2 values across China from January 1-20, 2020 (before the quarantine) and February 10-25 (during the quarantine). The data from the Tropospheric Monitoring Instrument (TROPOMI) on ESA’s Sentinel-5 satellite. Source: NASA, 2020.
Maps showing NO2 values across China from January 1-20, 2020 (before the quarantine) and February 10-25 (during the quarantine). The data from the Tropospheric Monitoring Instrument (TROPOMI) on ESA’s Sentinel-5 satellite. Source: NASA: Airborne Nitrogen Dioxide Plummets Over China, 2020.

Drops in Traffic Related Pollution During the Coronavirus Outbreak

The California Department of Transportation has similarly seen large drops not only in traffic, but pollution monitors placed along major cities such as Los Angeles and Oakland show a dramatic decline in air pollution. While average speeds on motorways have picked up substantially, air quality over the San Francisco Bay area and Los Angeles have been generally better than they have been in decades.[3] In a recent article in the New York Times and in other major media outlets, Descartes Lab processed data from Sentinel-5P and release the results, where the data and mapping showed large drops in NO2 emissions across major cities in the United States, including Los Angeles, New York, and Seattle, where social distancing and restrictions in movement have been in place and are among the most affected cities.[4]

Nitrogen dioxide concentrations over France.  Maps: ESA -  Coronavirus lockdown leading to drop in pollution across Europe, 2020.
Nitrogen dioxide concentrations over France. Maps: ESA – Coronavirus lockdown leading to drop in pollution across Europe, 2020.

However, this might not be all good news for people celebrating the fact that at least there is less air pollution. Oil prices have plummeted, in large part due to decreasing oil demand, but that likely means once economic activity can pickup again, then people will likely take advantage of cheap oil prices, leading to a surge in consumption. Traditionally, vehicles with poor gas mileage are purchased in greater quantities when oil prices plummet. The challenge for environmentalist is to have policymakers see the benefits of clean air, while it is self-evident over major cities, but also create policies that promote clean air policies after the COVID-19 pandemic subsides. This might not be an easy challenge, as policymakers will want to see the global and local economies recover from a major economic disaster.[5]

For scientists, the hope is somehow these drops prompt an adaptation to a new way of doing business that can lead to cleaner cities in the future post COVID-19 outbreak. For those who can develop a work at home or remote work culture, the crisis may benefit employers to adapt to a new way that can help reduce pollution. Nevertheless, it is clear policymakers are pushing for a return to normal and, with that, a return to normal pollution levels. Cultural change in reducing air pollution may require further action. 

References

[1]    For more on recent Sentinel-5P data, see:  https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-5P/.


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[2]    For more on a recent story about possible adaptation to lower levels of pollution after the outbreak, see:  https://www.theguardian.com/environment/2020/mar/23/coronavirus-pandemic-leading-to-huge-drop-in-air-pollution

[3]    For more on California’s Department of Transportation monitors, see:  http://pems.dot.ca.gov/.

[4]    For more on the drop of nitrogen dioxide levels in major US cities, see: https://www.nytimes.com/interactive/2020/03/22/climate/coronavirus-usa-traffic.html.

[5]    For more on what might happen to air pollution after the COVID-19 pandemic, see:  https://www.usnews.com/news/business/articles/2020-03-24/oil-industry-cites-virus-in-seeking-broad-pollution-waivers

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