The price of a gallon of gasoline has declined noticeably over the last few months in concert with a decline in travel during the COVID-19 pandemic and a concurrent decrease in the demand for fuel. With less fuel being burned, the atmosphere has responded with significant short-term improvements in air quality.
In this video, which first aired on April 29, 2020 as part of Penn State's long-running weather magazine show Weather World, (seen weekdays on WPSU-TV and the Pennsylvania Cable Network), we explore some of these changes in air quality using both satellite and ground-based observations.
The satellite data, courtesy of NASA and the European Space Agency, focus on nitrogen dioxide (NO2), a pollutant created primarily through the burning of fossil fuels (such as gasoline, diesel and coal) that enters the atmosphere mainly through tailpipes of vehicles and smokestacks of electricity-generating plants. Though NO2 levels can vary from day to day due to changes in the weather and other factors, when the satellite data is processed and interpreted carefully, changes in NO 2 concentrations can be a gauge of changes in human activity.
Ground-based measurements of air quality in Pennsylvania (from the Environmental Protection Agency) also show signs of improvement in various pollutants, including PM2.5, tiny particulate matter generally 2.5 millionths of a meter or smaller in diameter (about 30 times smaller than the width of a typical human hair). In the atmosphere, PM2.5 contributes to reduced visibility, while its small size makes PM2.5 easily inhalable and thus potentially a serious health hazard. These particles come primarily from vehicle exhausts, other sources that require the burning of fuels, and chemical reactions in the air resulting from those emissions. In terms of PM2.5, data from the Pittsburgh and Philadelphia metropolitan areas clearly show the best air quality (for this time of year) in at least the last two decades.
For centuries, human activities have been changing the composition of the atmosphere, essentially performing an experiment on local, regional, and global scales. In a matter of months, the pandemic has changed the course of this experiment, in some ways simulating in the short term the impact that policy decisions could have on air quality in the long term. Take this time to look up and observe, not only during the day but also after dark, when better visibility may allow a clearer view of the nighttime sky. What an excellent – and more or less unprecedented for our current generation – opportunity to appreciate what the sky could look like with lower emissions. Time may be short – we know that as mobility increases, the cleaner air probably won’t last.