Always check the data - in most places, human-caused pollution is small relative to natural sources

Over the past couple of months I have seen a dozen or more pollyannish type articles claiming that the silver-lining to Covid-19 is cleaner air. It is such a plausible claim that it never crossed my mind to quibble. If people stop driving, working, manufacturing, of course there will be less air pollution. It follows logically.

I should have known better. For high-pollution cities such as New Delhi and Beijing, where I have seen most of the photographic before-and-afters, it makes perfect sense.

For developed countries, where the past thirty years have seen dramatic improvements in air and water quality, the hypothesis is much more questionable. No matter how logically plausible a hypothesis might be, you should always check the data.

I last encountered this in Trump's first year when many partisan pundits were making the claim, even during the campaign, that Trump's language was hateful, incendiary and causing a dramatic increases in hate crimes. That was obviously an expression of partisan hope rather than reality. The most complete hate crime figures are only released annually so anything short of a year is speculation not a factual claim. And sure enough, when the next batch of data was reported, there was no support for the confidently proclaimed accusation. Over the next three years, adjusting for increasing number of departments reporting, the rate of hate crime commission has continued its long slow decline.

But it was a good reminder - always look at the data behind the claim. Which is what Myers does.

From The Coronavirus Lockdown Has Not Made the Air Cleaner by Todd Myers.

Just about every day, someone claims that the air is cleaner. That, we are told, is a small benefit of the coronavirus-induced economic lockdowns. By reducing traffic on our roads, we are polluting the air less, providing a visible example of the supposed benefits of imposing more environmental regulation.

In my hometown of Seattle, one environmental activist told the local paper that people can “physically see that difference in the cleaner air.” The air-quality data tell a different story.

According to the EPA’s air-quality monitors, levels of particulate matter — known as PM 2.5 — are not lower now and have, in fact, been higher recently than the median level of the last five years. Consisting of particles smaller than 2.5 microns, PM 2.5 includes natural sources such as smoke or sea salt, as well as human-caused pollution from combustion.

In Philadelphia, a city health commissioner said, “I would expect our air pollution levels will probably go down because the number of vehicles in the streets are less.” Recent particulate-matter levels, however, have been close to the five-year average.

In Dallas, the levels of PM 2.5 are higher than average. In Boston, they are slightly lower.

This counterintuitive result could be due to a number of influences, including weather. The key factor, however, is that in most places, human-caused pollution is small relative to natural sources. Even a significant reduction in the human contribution makes only a small difference.

One more time - Always check the data!