Is Pollution Clearing While We're Staying Home?

In this time of self-quarantine, exponential viral spread, and so much uncertainty, we could all use some positive news. With a large fraction of the population staying in their homes and only venturing out for essential items, many businesses shuttered, and only the most essential of us still commuting and traveling, how has nature responded?

Just in my little corner of the world, my car sits almost entirely quiet, unheard of for a resident of Los Angeles, and with the absence of all the hustle and bustle, my coyote neighbors have gotten more brazen with their visits. Let’s look at what this slow-down has meant around the world.

Air pollution is clearing up drastically 

NASA posted 2 maps of the mean tropospheric density of nitrous oxide (or NO₂₎ over China and Hong Kong from their Earth Observatory program. Nitrous oxide is a particularly nasty greenhouse gas. It’s produced via the combustion of fossil fuels and emitted during agricultural and industrial activities. It’s not as abundant as CO₂ in the atmosphere, but it lasts a lot longer and so its contribution is on the rise. NO₂ also works to deplete the ozone layer, even more reason we don’t want it in the atmosphere.

The first map, dated January 1-20, 2020, shows the amount of NO₂ gas observed in the troposphere (a layer of the Earth’s atmosphere) before widespread quarantine orders were enacted in Wuhan and other large cities in China. The second map, dated February 10-25, 2020 shows the same region after quarantine orders were in place. The polluting gas has been reduced by as much as 30 percent. 

Such a clear and persistent reduction [in nitrous oxide emissions] is likely due to the decreased traffic and industrial activity.

The gap in time between the two maps marks the days around the Chinese Lunar New Year celebrations when pollution levels normally decrease as factories and businesses close for the holiday. But pollution levels usually rebound by mid February as seen in maps from last year. That rebound didn’t happen this year, very likely due to the quarantine. 

Coal use is also down in China, dropping by as much as 36 percent in the month since the Lunar New Year celebrations. With demand...

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