Reductions in Nitrogen Dioxide Air Pollution Presumably Associated with Reductions in Fossil Fuel Use

Over the past several weeks, the Northeast US has seen significant reductions in air pollution over its major metropolitan areas. These recent improvements in air quality have come at a high cost, as communities grapple with widespread lockdowns and shelter-in-place orders as a result of the spread of COVID-19.

One air pollutant, nitrogen dioxide (NO₂ ), is primarily emitted from burning fossil fuels (diesel, gasoline, coal). If processed and interpreted carefully, NO₂ levels observed from space serve as an effective proxy for NO₂ levels at Earth's surface.

The images show satellite data of NO₂ from the Aura Ozone Monitoring Instrument (OMI) over the Northeast US in March. The top image shows the mean of the period from 2015 through 2019, while the bottom image on the right shows the mean for 2020.

Though variations in weather from year to year cause variations in the monthly means for individual years, March 2020 shows the lowest values as compared to any of the monthly values for March during the OMI data record, which spans 2005 to present. In fact, the data indicate that the NO₂ levels in March 2020 are about 30% lower on average across the region of the I-95 corridor from Washington, DC to Boston than when compared to the mean of 2015 to 2019. The images are free and publicly-available and may be downloaded.

Caution: Further analysis is required to rigorously quantify the amount of the change in NO₂ levels associated with changes in pollutant emissions versus natural variations in weather.

Pandemic Before and After: Nitrogen Dioxide data 2017-2019 versus 2020

• View NASA image feature
• Go to NASA's Air Quality web site
• High resolution images downloadable at NASA's Scientific Visualization Studio

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Technical description of figure:

The images above shows satellite data of NO₂ from the Aura Ozone Monitoring Instrument (OMI) over the Northeast United States in March. The image on the left shows the mean of the period from 2015 through 2019, while the image on the right shows the mean for 2020. Though variations in weather from year to year cause variations in the monthly means for individual years, March 2020 shows the lowest values as compared to any of the monthly values for March during the OMI data record, which spans 2005 to present. In fact, the data indicate that the NO₂ levels in March 2020 are about 30% lower on average across the region of the I-95 corridor from Washington, DC to Boston than when compared to the mean of 2015 to 2019. Caution: Further analysis is required to rigorously quantify the amount of the change in NO₂ levels associated with changes in pollutant emissions versus natural variations in weather. The images are free and publicly-available and may be downloaded.

Scientific significance, societal relevance, and relationships to future missions:

The OMI NO₂ data will enable scientific and applied research. The following are a few examples: :

• Air Quality: While air pollution is decreasing around the world due to lockdown orders, the US government has relaxed pollution emission restrictions on some industrial sectors (e.g., power plants). Therefore, the changes in air pollution associated with the pandemic will serve as a natural experiment in how the atmosphere responds to changes in pollutant emissions from various sources.
• Climate: Several recent studies by the proposers have shown that NO₂ emissions inferred from satellite data serve as an effective proxy for co-emitted CO₂ emissions from cities and power plants. Therefore, researchers may be able to assess the impact of the pandemic on climate gas emissions.
• Economics: Given that most world economies are driven by fossil fuels, economists may use NO₂ data, a non-traditional source of data for this community, to assess the impact of the pandemic on economic activity around the world, including in countries without reliable economic data.
• Intelligence Agencies: The global intelligence community will likely find interesting uses of the NO₂ data for assessing the impact of the pandemic on world countries, including with world governments that purposely misrepresent or withhold the true extent of the pandemic’s impact.
• Health Professionals: The NO₂ data may be used to gauge the effectiveness (e.g., reduction in emissions from traffic and industry) of lockdown efforts to contain or slow the pandemic in a given area.

Data Sources:

Satellite-derived emission estimates are based on NO₂ measurements from the Aura Ozone Monitoring Instrument (OMI). OMI is a Dutch–Finnish contribution to the NASA Aura mission.

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References: Joanna Joiner (NASA), Bryan Duncan (NASA), GSFC Aura Ozone Monitoring Instrument (OMI) Team

5.2020