New satellite data from EU Earth observation program Copernicus EU shows a decline in air pollution, especially nitrogren dioxide — a reactive gas that forms from car emissions — from Jan. 1 to March 11.
"The decline in [NO2] emissions over the Po Valley in northern Italy is particularly evident," Claus Zehner, ESA’s Copernicus Sentinel-5P mission manager, said in a statement.
"Although there could be slight variations in the data due to cloud cover and changing weather, we are very confident that the reduction in emissions that we can see, coincides with the lockdown in Italy causing less traffic and industrial activities," he added.
Areas that appear to have seen the most significant decrease in emissions are countries that were most severely impacted by COVID-19 and where many residents have been told to avoid travel and work from home.
An earlier observation derived from NASA and European Space Agency satellites found a similar trend in China but perhaps on a more jarring scale, according to a blog post from NASA's Earth Observatory website.
The satellites show a significant decrease in NO2 emissions between Jan. 1 and Feb. 25. China shut down all transportation out of Wuhan and local businesses starting on Jan. 23.
"This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event," Fei Liu, air quality researcher at NASA’s Goddard Space Flight Center, said in a statement.
While NASA air quality scientist Barry Lefer said it's normal for NO2 emissions to drop in winter, Liu said "the reduction rate is more significant than in past years and it has lasted longer," pointing to a correlation between the reduced emissions and COVID-19 travel precautions.
"I am not surprised because many cities nationwide have taken measures to minimize spread of the virus," she said.
There has also been a drop in airplane and boat travel, as well as factory usage, thus curbing other kinds of emissions, as well.
The World Health Organization declared COVID-19 a pandemic on March 11, and a number of countries have enacted domestic and international travel restrictions.