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Pollution From Diesel Cars Grossly Overhyped

April 15, 2020

By Paul Homewood


Pierre Gosselin has an interesting post about NO2 pollution:



The Corona crisis is bringing it to light: car traffic has decreased significantly, but the air quality in city centers has hardly changed,” Tichy comments.

Environmental claim exposed as false

Recall that a major reduction of diesel engines was supposed to improve air quality. After all, experts at the Baden-Württemberg State Institute for the Environment (LUBW), for example, have attributed a large 80 percent share of air pollutants especially to diesel vehicles – so they have to be banned soon.

Yet Tichy notes: “If this is true, the ‘shutdown’ would have to have a drastic effect. But it does not.”

It turns out that the involuntary “corona experiment” with its widespread stop of car traffic has exposed bare the false claim made by environmental activists: Diesel cars are responsible for polluting the air of German cities.

Diesel car bans “pointless”

According to Tichy, the “Corona Experiment” exposes just how pointless driving bans issued by the green transport ministers can be. “They obviously have no effect on the NO2 concentrations in the air.”

“The measured values, for example, at the Am Neckartor station in the Stuttgart city center were already below the limit value of 40 µg/m3 in February and March, ” writes Tichy. “At that time, traffic was still flowing and ‘shutdown’ had not yet been announced.”

Other larger factors

Tichy adds that engineer and measurement expert Martin Schraag accuses proponents of car bans of data “manipulation” and reminds that today’s “newer vehicles and those retrofitted with software updates hardly emit any exhaust gases. This should also have been reflected in the results.”

Schraag notes that NO2 values fluctuate strongly and depend heavily on Stuttgart’s weather conditions and wintertime  heating can be the cause.

“The weather, if you look at the data, has a decisive influence,” Tichy comments. “The experts of the LUBW environment office obviously did not care about these influences and officially know nothing about them. They still assume that traffic accounts for 80 percent of air pollutants.”

Read the full post here.


I looked at one of the Sheffield monitoring sites last week to see what the effect of the lockdown might have been. It showed a drop in NO2 this month, but if anything an increase in PMs.

To get a fuller picture, I have now got graphs for the other Sheffield site on Barnsley Road.

Unlike the other site on Devonshire Green, this one is bang next to a busy road. I actually know it well, as I used to work a few hundred yards away!





Although we see a drop in NO2 levels this month, they don’t appear to be hugely lower than the equivalent time last year.

What is much more significant though is the increase in NO2 levels in winter months, backing up Tichy’s claims that much of the NO2 arises from heating of homes.

While it would be silly to pretend that cars emit no NO2 at all, it appears that they only play a minor role.



As for PMs, the lockdown appears to have had absolutely no effect at all. Day to day variation, presumably due to weather conditions, dominate.



  1. April 15, 2020 11:37 am

    I cannot claim this observation to be scientific, but here it is for what its worth. We live on a fairly busy road on the edge of Valencia, Spain. We use our balconies regularly and clean them and the chairs and tables thereon every day. The chairs and tables are always dirty. Since the lockdown there has been no noticeable dirt on them. I assume the dirt consists of particulates from tyres, brakes, the road surface and car fumes. Though I wish no ill on those relatives and friends who have lost loved-ones in the pandemic, a bonus for us has been absolute quiet, and clear air.

    • MrGrimNasty permalink
      April 15, 2020 12:09 pm

      I expect your observation (if not due to weather changes rather than traffic) is mostly coarser dust than that measured for air pollution.

      11:00 am April 15th 2020

      “Valencia air quality index (AQI) and PM2.5 air pollution is 51, Moderate.”

      I live on a main road and get dust on windows etc., can’t say I’ve noticed any difference and traffic has gone from continuous to perhaps a couple of cars a minute.

      Perhaps you can find a data source like the UK DEFRA one and get some graphs – it would be interesting to see if the air quality changes are just anecdotal or real in your area, all adds to the picture.

      • Gamecock permalink
        April 15, 2020 1:53 pm

        “Valencia air quality index (AQI) and PM2.5 air pollution is 51, Moderate.”

        Steve Milloy has proven PM2.5 is not hazardous. I.e., it is NOT pollution.

    • Phoenix44 permalink
      April 15, 2020 5:17 pm

      PMs we are talking about are tiny – the size of a grain of pollen. General dirt in cities is much larger particles.

  2. MrGrimNasty permalink
    April 15, 2020 11:47 am

    Preston Park Brighton again.Yes the correlation to traffic is still completely unconvincing (hover cursor over individual pollutant name in key on the right to isolate).

    NO2 drops up to 30Mar and after 13Apr correspond to European air being blown away by the wind veering. The worst PM peaks in this 2 month period are well into the shutdown.

  3. ianprsy permalink
    April 15, 2020 1:01 pm

    My local council could use this news to push their proposed move to electric-only heating as part of their climate change policy. Any port in a storm.

  4. Steve permalink
    April 15, 2020 1:03 pm

    In the Central London ULEZ zone the reduction in diesel cars was calculated as giving an extended life span of a week over eighty years for a person living there for a lifetime. This was obtained by using the TFL and King’s calculated figure for NO2 at 5% of the total of all sources. Following this criticism the next version of the campaign against diesel produced a new pie chart showing the NO2 jumping to 40%. This was achieved by omitting the 50% of background NO2, which is everywhere, and moving the date forward to 2025 by which time they assume that other forms of transport and heating will be drastically reduced. But of course the improvement to diesel engines such as the already used ad blue would not result in the a reduction from cars.

  5. It doesn't add up... permalink
    April 15, 2020 1:11 pm

    Don’t encourage them to ban non electric heating!

    The NAEI mapping suggests that only motorways produce higher levels of NO2.

    It is interesting to note that if you look at the contributions sector by sector on the maps you can pick out diesel hauled rail routes, major airports… and NHS hospitals as major point sources.

    • MrGrimNasty permalink
      April 15, 2020 3:38 pm

      Then we definitely need to ban the use of nitrous oxide in hospitals, and backup diesel generators.

      • It doesn't add up... permalink
        April 15, 2020 4:42 pm

        I thought you were going to suggest banning the use of oxygen. Without that you can’t make NOx!

  6. Athelstan. permalink
    April 15, 2020 5:26 pm

    A first class post Paul.

    Although, as I said, our air over the UK is some of the cleanest in the western world and therefore, the world full stop.

    All the rest is climastrology delusional extrapolation and false assignation, UN loony ’emission’s pollution’ bloviating twaddle and doctors on the make, so called air pollution like man made CO2 – causing runaway warming another mythologized but false threat – and btw our kids – this generation breathe the cleanest air since records began according to legend and fire – we saw the light.

  7. edwardrodolph1891 permalink
    April 15, 2020 5:44 pm

    No-one should hold their breath waiting for a retraction or even an apology!

  8. April 15, 2020 11:35 pm

    Paul and the regulars I have a question
    For me Chris Smith has always been a hero science communicator
    yet on Global Warming he sides with the crowd
    On Saturday Chris Smith said “Yeh these reductions in CO2 can be seen from satellite”
    Is that true ? can NASA and EU CO2 satellites actually spot such a difference ?

    Natural sources must be huge as we come into Spring
    Plus I would expect that we are actually still outputting almost the same CO2
    especially at Drax and other biofuel etc

    Maybe he means they are inferring from reading NOx ?

  9. April 15, 2020 11:36 pm

    There is this weather site that gets NOx from Copernicus EU Sat,no2,54.728,17.314,4

    Look at the NoX blobs in the sea.. eg straits of Gibraltar
    is that actual shipping exhausts ?

    Belgium is on hard lockdown .. yet it has the biggest concentration.

    • Victor Hanby permalink
      April 16, 2020 10:52 am

      Thanks Stew, this is a really interesting link. Back in the late nineties I had two grants from the UK EPSRC to look at Nox emissions from commercial (>300 kW) and domestic boilers. It seems as though emissions from stationary sources have dropped off the radar in favour of bashing diesel engines – much more fun I guess.

  10. April 16, 2020 11:37 am

    Note this French conversation
    First guy “here is a map of CO2″
    Second guy ..”that is a map of NO2”

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