(NBC News)  Coronavirus stay-at-home orders and social distancing are having an unintended side effect: cleaner air.

Even in the world's most polluted capital city, New Delhi, monuments are visible against blue skies for the first time in generations.

At one moment last week Los Angeles, the U.S. smog capital and birthplace of car culture, had the cleanest air in the world.

NASA satellite pictures over China and the northeastern United States show dramatic drops in nitrogen dioxide pollution, but what you can see isn't the whole picture.

"It's important for people to understand that just because the particles are gone and the skies are nice and blue, that doesn't mean there aren't gases that are trapping heat and that's what's causing climate change," says NASA research meteorologist Dr. Lesley Ott.

Eliminating pollutants you can see doesn't necessarily mean the more crucial ones you cant see are also going away.

"Some of the pollutant problems that we have, ozone for example, do not seem to be changing and so this is an excellent opportunity to test hypotheses about why that is,” says University of California Riverside ozone researcher Kelley Barsanti.

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