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Lockdown Has Not Made the Air Cleaner in the US

May 15, 2020

By Paul Homewood


An interesting report from the US, which seems to back up what I’ve been saying over here:



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.

So, why do so many activists claim the air is ‘physically cleaner’ in the United States?

In part because they want to believe it. Opposition to cars is a major theme in left-wing environmental politics, and it is simply assumed, without looking at the data, that less driving equals cleaner air. The large gap between the political rhetoric and scientific reality is a reminder that costly environmental regulations should be based in real-world data, not ideologically driven assumptions.

Full story here.


As over here, the article goes on to note that NO2 levels have dropped a little over lockdown, but as Dan Goldberg, an atmospheric researcher at Argonne National Laboratory, explains, this is probably largely weather related:



It is worth reading the rest of Dan’s comments on his twitter feed, which go into more detail. But the key point is that sunlight breaks down NO2. He says that you would normally expect a 25% reduction between March and April, purely because of the angle of the sun, hence the fall from January to February above.

As Dan notes, the rise during March reflects the very cloudy conditions at the time.

Although reduced traffic and industrial activity may have contributed to reduction in NO2, it is clear that this is very tiny in comparison to the natural factors involved.

  1. May 15, 2020 10:11 am

    Most greenblob & libmob news
    is based on what they want the world to be
    .. rather than what it actually is

    Cherry picking certain metrics, whilst OMITTING to talk about others
    is a characteristic of this.

  2. May 15, 2020 10:18 am

    UK Pollution decreased 70% from 1970-2015 after Clean Air Act in 1970.
    What today’s claimers should do is add their readings to the traditional graph
    my guess is it will be little different.×360

  3. Graeme No.3 permalink
    May 15, 2020 10:25 am

    And from today’s racing news.
    Wishful Thinking comes second to Real World Data

    • John Cullen permalink
      May 15, 2020 11:51 am

      Not if you are a rent-seeking crony capitalist!

      • Graeme No.3 permalink
        May 15, 2020 12:25 pm

        True. I forgot that from L*rd Deb*n downwards (if that is possible) they have worked to be prominent race judges.

  4. Devoncamel permalink
    May 15, 2020 10:28 am

    As ever the green lobby doesn’t want to let the facts get in the way of their narrative.

  5. Jonathan Scott permalink
    May 15, 2020 10:31 am

    Well Saint Greta of Stockholm can see CO2 so I suppose it is no surprise that claims of what they see and feel are paramount and over promoted by the “impartial” left wing propaganda machine. It is just more of the BS of a belief system which is encouraged and amplified by an obscene about of cash stolen from the public purse which is after all what this is all about.

  6. jack broughton permalink
    May 15, 2020 11:16 am

    Talking about real spinners (not cricket), there was an article in about a USA survey that provided the result that 62 % of people surveyed (no doubt loaded questions too) did not believe that Global Warming would impact the American economy. Also, 65% believe that no more money should be spent on subsidising climate change actions.

    The sponsoring company (Inerjys Ventures, a RE company) said that “only 38% of Americans believe that climate change is damaging” they then go on to say that “The fact that so few understand the damage climate change will cause….”. Thus, they totally ignore that fact that despite a deluge of daily-brainwashing, and double-duckspeak, people in the USA are totally unconvinced by the climate disaster mantra.

  7. MrGrimNasty permalink
    May 15, 2020 11:31 am

    Politicians are already using the supposedly cleansed air as excuses for crazy policies – witness Grant Shapps on last night’s covid press conference – talking about locking in the dividend of massively cleaned air with cycle/walking cash, EV charging point binges, and lethal e-scooter trials/legalisation.

    As I said before, I think the only real improvements are right on the kerbside on massively busy roads in the biggest cities where the roads are very enclosed. And only NOXs, nothing else – other measured pollutants often seem worse after lockdown. People only get brief exposures here and it’s no worse than standing near a gas hob, and far better than being near a BBQ, char-grill restaurant, bonfire etc. You need some perspective.

    The China/N.Italy examples are very specific topological/meteorological cases and how much was due to the shutdowns or a change in the weather would have to be investigated – although given how polluting industry is in China you would expect a positive change there for sure. Comparing one instance with the same time last year, or a 5 year average, or before/after without considering other factors is just scientific fraud.

    Even allocating any alleged improvements to private cars is problematic – what was the change in weather, GCH use, industry, and taxi/bus/hgv transport etc.

    The contribution of private cars to city air pollution has long been wildly exaggerate, and banning them will not make any worthwhile difference IMO.

  8. May 15, 2020 11:32 am

    Driving along the A40 and M5 yesterday evening, the distant views of and from the Cotswolds were crystal clear, far more so than normal.
    But then it had been a truly amazing day, weather wise. Beautiful blue skies, warm in the sunshine, but really cold in the shade. No doubt the High to the west of us was responsible, but that wont be the line that is fed.
    Come to think of it, we’ve been having this glorious weather ever since lockdown began. It’s been a huge help to morale but unwittingly has been feeding in to the green blob narrative of less traffic = clear air.

    • MrGrimNasty permalink
      May 15, 2020 11:38 am

      We’ve been flooded by Arctic air, that’s why. The UK is usually polluted by European continental air.

  9. Paul permalink
    May 15, 2020 11:37 am

    I very much doubt that the green lobby has even looked at the data. Their theories and their models say that less traffic leads to better air, ergo it does.

  10. MrGrimNasty permalink
    May 15, 2020 11:50 am

    Just when people are safest in cars, Kahn decides to force more onto buses/trains.

  11. ThinkingScientist permalink
    May 15, 2020 11:55 am

    If NO2 is broken down by sunlight, does the record level of sunshine this April explain the decrease in NO2 that Paul reported a few weeks back?

    Another thought occurred to me recently concerning air quality. I recall that it was reported after the VW emissions scandal that Academics/Researchers claimed that this explained why their measured pollutants weren’t falling with new legislation. Now I wonder if its because traffic has a much smaller contribution than claimed.

  12. Broadlands permalink
    May 15, 2020 1:42 pm

    Is it not true that particulate aerosols leave the atmosphere quickly…gravity? The air could appear cleaner yet still have gases, especially CO2 which just reached another new record at Mauna Loa. CO2 will necessarily increase simply because the world cannot stop using ICE fuels instantly. The same should apply to other exhausts.

  13. Harry Passfield permalink
    May 15, 2020 2:01 pm

    This theory of why there are higher levels of PM2.5 just came to me. And the reason why is because I have just recovered my (ornamental) fish-pond from the winter floods which badly silted it up. As many pond-keepers will know, the enemy is green water where – amongst other things – very fine particles of silt – get through physical foam filters and keep recycling into the pond. It’s a never-ending headache as to the solution.
    In my case, I realised that the lamp in the UV filter I’d built into my waterfall must have failed and the simple answer was to replace the bulb. That done, within a week the pond was crystal clear.
    For those who don’t know, UV filters allow the pond to recycle water across the 20cm length of the bulb and the UV light causes very small particles to floculate (I love that word!) – they effectively amalgamate with others to form larger particles that can be trapped in the foam filters. The indication that it works, apart from clearer water, is the amount of ‘mud’ that the filters collect.
    So….is the increase in PM2.5 a result of low floculation caused by lower UV? It’s counter-intuitive because I would have expected there to be more UV in clear, sunny weather….

  14. Broadlands permalink
    May 15, 2020 2:16 pm

    It is worth adding that a restriction to particles no greater than 2.5 microns is ‘cherry-picking’ because the bulk of vehicle exhaust ‘soot’ is much greater. It is those larger exhaust aerosols that fall out and leave the air cleaner. Smaller ones also agglomerate. There should be more UV reaching the ground when these larger particles are missing. Solar UV is what is responsible for coral ‘bleaching’, not sea surface warming.

  15. Gamecock permalink
    May 15, 2020 3:14 pm

    ‘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.’

    NG: ‘Pollution is the introduction of harmful materials into the environment.’

    PM2.5 is not harmful. Hence, it is NOT pollution.

  16. Gerry, England permalink
    May 15, 2020 3:42 pm

    Yes, TfL will make it more expensive to do business in London with a measure forced on them as part of their bailout from bankruptcy. No mention of not paying their furloughed staff the remaining 20% of their salary. They are also helping the City of London to make the square mile a no-go area for motor vehicles – including battery ones. That should help ease the recession no end. Still if everyone brought in a pack lunch and a flask of tea or coffee then most the food places can close down anyway. No hanging around after work in bars and pubs – straight off home.

  17. Thomas Carr permalink
    May 15, 2020 5:01 pm

    Mr GrimNasty’s explanation at 11.38am today is entirely sane. The days when my view of the horizon on the North Sea is clear and ‘hard’ is when the wind is from the North and North East – cold Arctic air with low humidity. The opposite i.e. relatively hazy horizon with reduced visibility, can be seen on the Dawlish webcam which faces south west) when the wind is from between East to West.

    • jack broughton permalink
      May 15, 2020 5:20 pm

      In Birmingham we get sand depositions on the cars when the wind is from the south. Apparently, this fine sand has been identified as Saharan in origin….. bloody nuisance.

      This low activity spell ought to give the car-makers the ammunition to shoot-down the government policy on diesels, except for the CO2 of course.

  18. Keith Harrison permalink
    May 15, 2020 7:08 pm

    PM2.5 is used as a descriptor of human pollution. Has anyone actually analyzed collected samples before, during and after the lockdowns? What is human and what is natural?

    • David Virgo permalink
      May 16, 2020 11:32 am

      The PM2.5 particles are monitored because that size of particle can be inhaled all the way into the alveoli of the lungs and may stay there. They are not necessarily human pollution but they are not considered good for your health wherever they come from.

  19. Gary Kerkin permalink
    May 15, 2020 11:09 pm

    As has been noted earlier, actual fact overrules wishful thinking. I thought the explanation is plain. The atmosphere is a very big “pond” into which pollution is adding some grains of sand every day. If the addition is perturbed to less grains of sand for a few days what would we expect to see? A large change in the average grains of sand in the pond?

  20. MrGrimNasty permalink
    May 16, 2020 10:46 am

    Brighton still exploiting the emergency – given that the comments are usually eco/left-wing dominated, the amount of criticism is telling.

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