COVID-19 Lockdowns Helped Lower Global Nitrogen Dioxide By 20%, Discovers NASA

COVID-19-related restrictions significantly lowered the concentration of a key air pollutant while transport declined and industries slowed down globally. NASA researchers have detected a 20% dip in global nitrogen dioxide levels since February.

To find out how much of the nitrogen dioxide decline can be attributed to changes in human activity during the COVID-19 lockdowns, researchers at NASA compared data from recent observations to a model of a hypothetical coronavirus-free 2020, the space agency said.

Nitrogen dioxide is produced by the combustion of fossil fuels by numerous industries as well as transportation.

“We all knew the lockdowns were going to have an impact on air quality,” said lead author Christoph Keller of Universities Space Research Association (USRA) at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“It was also soon clear that it was going to be difficult to quantify how much of that change is related to the lockdown measures, versus general seasonality or variability in pollution," he continued.

In the model, researchers used an alternate reality of 2020 — one without a global pandemic — generated using computer models. Assuming there was no change in human activity, they subtracted the results of the current observations from the alternative outcome of this year.

"The researchers received data from 46 countries — a total of 5,756 observation sites on the ground — relaying hourly atmospheric composition measurements in near-real-time. On a city-level, 50 of the 61 analyzed cities show nitrogen dioxide reductions between 20-50%" NASA stated.

The results of the study revealed that a change in current-day practices can result in a massive change on Earth in just a short period of time, leaving hope for future generations and a reminder to adopt better practices in the years to come.

“In some ways, I was surprised by how much it dropped,” Keller said. “Many countries have already done a very good job in lowering their nitrogen dioxide concentrations over the last decades due to clean air regulations, but what our results clearly show is that there is still a significant human behavior-driven contribution.”

The researchers' findings were presented at the 2020 International Conference for High Performance Computing, Networking, Storage and Analysis, which was held from Nov. 9 to 19 in San Diego, California.