Satellite data showing nitrogen dioxide emissions over northern Italy on March 7 (left) and February 8 (right).
Satellite data showing nitrogen dioxide emissions over northern Italy on March 7 (left) and February 8 (right).
Image: Sam Gassó

After China, Italy has been the second-hardest-hit by the covid-19 pandemic racing around the world. In an effort to staunch the number of cases, the Italian government severely restricted travel this week in northern Italy—the pandemic epicenter for the country—before extending restrictions to the entire country.

Under similar circumstances, scientists observed a huge drop in Chinese pollution that was visible from space. At the time, Fei Liu, an air quality researcher at NASA, said that “this is the first time I have seen such a dramatic drop-off over such a wide area for a specific event.” Now, it appears the same thing is happening in northern Italy, as the region grinds to a halt.

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The European Space Agency’s Sentinel-5 satellite is able to track all sorts of human-caused pollution, including nitrogen dioxide. Those emissions come from tailpipes and electricity generation, particularly coal-fired power plants. With Italy severely restricting travel and whole sectors of the economy essentially shutting down and using less power, it would seem to follow that nitrogen dioxide emissions would drop.

Before and after imagery from Santiago Gassó, a NASA atmospheric science researcher, shows the stark difference from before the covid-19 outbreak and after. The images at the top of the page show nitrogen dioxide emissions on March 7 and February 7, respectively. Santiago tweeted that the data still needed more formal verification, but he told Earther in an email that “in the last 48 hours, colleagues have been posting similar trends from other sensors, and even this morning ESA came out with a video confirming what I pointed out. So indeed the trend seems real.”

Indeed, the video in question shows the drop in pollution is extremely rapid. The Sentinel-5 data in the video from the ESA runs from January through mid-March. The bright red and orange spot of pollution over northern Italy goes dark shortly after the government issued the lockdown orders this past Sunday.

The drop in pollution is obviously a good thing, particularly at a time when people with pre-existing respiratory issues are facing increased risks from covid-19. But the cause for the drop is most definitely bad. Data tracked by Johns Hopkins shows that as of Friday afternoon, there have been more than 1,000 deaths in Italy amid more than 15,000 cases reported.

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The number of cases in other countries, particularly the U.S., continues to climb. So, too, are precautions to prevent the further spread of the coronavirus. Flights are beginning to be grounded after flying empty. The U.S. has declared a national emergency amid what is still a very sluggish, botched federal response. Even a number of Disney’s various properties are shutting down. All of this adds up to a likely sharp decline in pollution in other parts of the world, as people hunker down in an attempt to stop the disease from spreading further.

Managing editor, Earther

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