COVID-19 lockdowns significantly impacting global air quality

American Geophysical Union

WASHINGTON–Levels of two major air pollutants have been drastically reduced since lockdowns began in response to the COVID-19 pandemic, but a secondary pollutant – ground-level ozone – has increased in China, according to new research.

Two new studies in AGU’s journal Geophysical Research Letters find nitrogen dioxide pollution over northern China, Western Europe and the U.S. decreased by as much as 60 percent in early 2020 as compared to the same time last year. Nitrogen dioxide is a highly reactive gas produced during combustion that has many harmful effects on the lungs. The gas typically enters the atmosphere through emissions from vehicles, power plants and industrial activities.

In addition to nitrogen dioxide, one of the new studies finds particulate matter pollution (particles smaller than 2.5 microns) has decreased by 35 percent in northern China. Particulate matter is composed of solid particles and liquid droplets that are small enough to penetrate deep into the lungs and cause damage.

The two new papers are part of an ongoing special collection of research in AGU journals related to the current pandemic.

Such a significant drop in emissions is unprecedented since air quality monitoring from satellites began in the 1990s, said Jenny Stavrakou, an atmospheric scientist at the Royal Belgian Institute for Space Aeronomy in Brussels and co-author of one of the papers. The only other comparable events are short-term reductions in China’s emissions due to strict regulations during events like the 2008 Beijing Olympics.

The improvements in air quality will likely be temporary, but the findings give scientists a glimpse into what air quality could be like in the future as emissions regulations become more stringent, according to the researchers.

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“Maybe this unintended experiment could be used to understand better the emission regulations,” Stavrakou said. “It is some positive news among a very tragic situation.”

However, the drop in nitrogen dioxide pollution has caused an increase in surface ozone levels in China, according to one of the new studies. Ozone is a secondary pollutant formed when sunlight and high temperature catalyze chemical reactions in the lower atmosphere. Ozone is harmful to humans at ground-level, causing pulmonary and heart disease.

In highly polluted areas, particularly in winter, surface ozone can be destroyed by nitrogen oxides, so ozone levels can increase when nitrogen dioxide pollution goes down. As a result, although air quality has largely improved in many regions, surface ozone can still be a problem, according to Guy Brasseur, an atmospheric scientist at the Max Planck Institute for Meteorology in Hamburg, Germany, and lead author of one of the new studies.

“It means that by just reducing the [nitrogen dioxide] and the particles, you won’t solve the ozone problem,” Brasseur said.

Worldwide emissions

Stavrakou and her colleagues used satellite measurements of air quality to estimate the changes in nitrogen dioxide pollution over the major epicenters of the outbreak: China, South Korea, Italy, Spain, France, Germany, Iran and the United States.

They found that nitrogen dioxide pollution decreased by an average of 40 percent over Chinese cities and by 20 to 38 percent over Western Europe and the United States during the 2020 lockdown, as compared to the same time in 2019.

However, the study found nitrogen dioxide pollution did not decrease over Iran, one of the earliest and hardest-hit countries. The authors suspect this is because complete lockdowns weren’t in place until late March and before that, stay-at-home orders were largely ignored. The authors did see a dip in emissions during the Iranian New Year holiday after March 20, but this dip is observed during the celebration every year.

Air quality in China

The second study looked at air quality changes in northern China where the virus was first reported and where lockdowns have been most strict.

Brasseur analyzed levels of nitrogen dioxide and several other types of air pollution measured by 800 ground-level air quality monitoring stations in northern China.

Brasseur and his colleague found particulate matter pollution decreased by an average of 35 percent and nitrogen dioxide decreased by an average of 60 percent after the lockdowns began on January 23.

However, they found the average surface ozone concentration increased by a factor of 1.5-2 over the same time period. At ground level, ozone forms from complex reactions involving nitrogen dioxide and volatile organic compounds (VOCs), gases emitted by a variety of household and industrial products, but ozone levels can also be affected by weather conditions and other factors.


AGU is an international association of more than 60,000 advocates and experts in Earth and space science. Through our initiatives, such as mentoring, professional development and awards, AGU members uphold and foster an inclusive and diverse scientific community. AGU also hosts numerous conferences, including the largest international Earth and space science meeting as well as serving as the leading publisher of the highest quality journals. Fundamental to our mission since our founding in 1919 is to live our values, which we do through our net zero energy building in Washington, D.C. and making the scientific discoveries and research accessible and engaging to all to help protect society and prepare global citizens for the challenges and opportunities ahead.


62 thoughts on “COVID-19 lockdowns significantly impacting global air quality

  1. “It is some positive news among a very tragic situation.”

    So all we need to do is lose our jobs, our income , our homes, our independence our liberty to go outside and in return we get less NOx, PM2.5 and we will gain 6 statistical days of longevity as senile incontinents as interns in “care homes”.

    Hey WIN-WIN for humanity !!

    • Yes… except you won’t get those six days, because any government powerful enough to lock you down won’t allow you to enjoy your golden years, you useless eater.

      • Exactly!! We have all heard about Andrew Cuomo’s executive order to kill off the elderly by requiring nursing homes to allow admittance to CV19 positives.

        Seriously, gotta go way out of your way to do that… And so obvious!!

        • That’s what his brother CNN’s Chis Cuomo will doubtlessly be calling out as “murder”, and it is.

          But there again not wearing a mask in public is much more serious than legislating that the most at risk group are exposed to known, tested, COVID infected patients. N’est pas ?

      • Water pollution, e.g. from sewage, is significantly reduced when citizen’s intake of food is reduced. A 60% reduction in food causes an even greater reduction in consumption because some citizens cease consumption all together.

      • Mike Bryant said, “Yes… except you won’t get those six days, because any government powerful enough to lock you down won’t allow you to enjoy your golden years, you useless eater.”

        But I’m already in my not-so-golden years, and I likes to eat, one of my favoritestest things.

        Stay safe and healthy, All.

      • When they get around to thinning the human herd to 500 million, I’ve a feeling that “useless” category is going to get pretty wide.

        • In any practical sense, it would be impossible to get the population that low.

          And even if they did, they themselves would find themselves back in the dark ages with no amenities very quickly.

  2. At ground level, ozone forms from complex reactions involving nitrogen dioxide and volatile organic compounds (VOCs), gases emitted by a variety of household and industrial products, but ozone levels can also be affected by weather conditions and other factors.

    So if there’s a drop in NO2 and VOCs the resulting ozone must be mainly natural.

    Failure to produce NO2 is apparently allowing naturally occurring ozone levels to get back to their more natural levels.

    • allowing naturally occurring ozone levels to get back to their more natural levels.

      Our brilliant government employees better do something quick ……. otherwise the Ozone Hole will quickly fill up and start overflowing on top of those Antarctica scientists.

    • yeah that caught me to
      and ozone causes pulmonary/heart issues(doubleplus wordage?)
      so then all the non industrial places with clean air are then harmful for health , as overly endowed with ozone by that statement?

      dont see overly many happy people at living without the transport cars and jobs right now
      welcome to the GND reality
      or not;-(

    • “So if there’s a drop in NO2 and VOCs the resulting ozone must be mainly natural. ” Surface ozone is created by the interaction of NOx, CO and volatile organic compounds and UV radiation, and most of the NOx, CO and VOCs in the atmosphere are anthropogenic. What’s probably happening here is that ozone has increased despite the reduction in atmospheric NOx because particulate emissions are also down, resulting in increased UV radiation reaching the surface.

    • Many studies have found that VOCs are the limiting factor for ground ozone in many places, not NOx. And apparently there is evidence of an inverse relationship with NOx. The pseudoscientists at the EPA didn’t let that stop them from enacting outrageously draconian limits on NOx emissions for cars – those standards that VW rightly cheated.

      • IIRC, when I lived in southern California, something like 5% (the oldest cars) were emitting 90% of the vehicle pollution. Older cars get a pass during vehicle inspection. Therefore, tightening regulations on new cars and trucks won’t have much effect.

  3. Oooh, please can I have $1M to model the forthcoming Ozone-catastrophe? It must be man’s fault…

    • “can I have $1M to model the forthcoming Ozone-catastrophe?” I hear Professor Neil Ferguson has some code you could use.

  4. Why no mention of carbon dioxide (CO2) in this AGU article? The decrease in some of these monitored gases suggests the lockdowns/shutdowns are having a (mixed) effect, but what is CO2 doing? No change over Mauna Loa? Since the AGU has morphed into a CAGW supporter their comments can’t be trusted, without other verification. I sense a disturbance in the Force. Stay sane and safe.

    • Why no mention of carbon dioxide (CO2) in this AGU article? …… No change over Mauna Loa?

      The AGU “jumped-the-gun” on publishing that article.

      Iffen they had waited 5 to 7 more days the bi-yearly (seasonal) decrease in atmospheric CO2 would have begun …… and they could have claimed it was the result of the Covid-19 shutdown.

      • Sam wrote:
        “If they had waited 5 to 7 more days the bi-yearly (seasonal) decrease in atmospheric CO2 would have begun …… and they could have claimed it was the result of the Covid-19 shutdown.”

        Good comment Sam – and the CAGW/climate fraudsters will probably do exactly that! That’s how they roll.

      • Yes, CO2 likely peaked last week at ~418 ppm. They have to tread lightly with regard to this because it will raise the issue of why a real reduction in CO2 concentration is not observed, other than that due to the natural cycle. They may not want the public to ask some questions.

        • Scissor – yes, and what about those contentious CO2 residence / decay times?

    • Ron,
      417.1ppm on the 11th May
      416.4ppm on the 7th May

      It’s been bobbing around 417 or a bit less for most of the last month, but the hourly measurement can be anywhere from 412 to 420. It’s almost impossible to see any variation due to lockdown at all. Very soon the level will start to drop (toward 410ppm Sep/Oct?) as it does every year during spring/summer in the NH- expect to see headlines bleating about that being due to WuFlu very soon.

      (I had an exchange with someone a week or two ago here. S/he said there would be a visible ‘dink’ due to lockdown, and I think I’ll concede that if you squint – maybe 2ppm through the last half of April.)

      • Asia is the largest pollutant, and they didn’t shut down. Clearly they’re more of a factor and Western society is less of a factor than we’ve been less to believe.

        Funny thing is I’ve been arguing this exact point since the Paris Waste of Paper Project. “You can completely remove the USA off the face of the earth, and unless China and India so something you won’t notice a difference.” What we are forgetting is that China and India promised to continue to increase, while the rest of industrial nations promised to disappear.

      • There is a barely discernable dip in the seasonally adjusted data but it is smaller than other wiggles in recent years. The last dot seems firmly above the mean slope.

        ERSL data processing very well documented , with code:

        I removed the 2.44 ppm/year linear trend from their deseasonalised data and got this:

        Not the slightest sign of a dip this year. Grab your copy of this dataset before it gets “recalibrated” later this year.

        • Correction, the latter graph was their longer filter so would smother any subannual change.

          They don’t provide data with the annual cycle removed it seems.
          Here is 40d filtered daily data minus the linear trend and the interannual variations above:

          The secondary peak which happens at this time of year is slightly smaller than last year but this in not unique. It is very similar to what happened three years ago.

          There is no discernible difference this year, for all our pain. No reason to continue this stupidity under the delusion that it will affect global CO2 and thus weather in 2050.

          If this finally blows the lid on the CAGW scammers, we may get some payback for the shutdown.

      • Amos
        You remarked, “… maybe 2ppm through the last half of April.” Along with pronouncements about “Hottest April on record!”

      • Very soon the level will start to drop (toward 410ppm Sep/Oct?) as it does every year during spring/summer in the NH-expect to …

        Amos E., …. but don’t forget, …. it is also fall/winter in the SH and it is those COLD ocean waters that are “sucking” that CO2 out of the atmosphere and causing the Mauna Loa measurements to decrease.

        Amos, the following was posted by Donald L. Klipstein – January 9, 2020 at 10:43 am

        I looked at the Barrow CO2 graph linked by Samuel C Cogar . It appears that there is a seasonal CO2 sink in that area in the summer. I suspect the nearby part of the Arctic Ocean which is frozen over most of the time other than summer (July, August & September), but in the summer it is liquid but colder than most of the world’s sea surface so it is sucking CO2 out of the lowest part of the troposphere in that area. I have seen imagery from the OCO2 satellite showing CO2 being less than the overall atmospheric average in cold ocean areas where and when there is cold liquid water.

        So, getting a clue from what Klipstein stated above, I extracted 2 consecutive years of “monthly CO2 data” from NOAA’s data bases as noted below, to wit

        NOAA monthly average CO2 ppm 1971 – 1972

        @ Barrow, Alaska ……. @ Mona Loa, Hawaii …… BRW is > MLO
        BRW 1972 1 333.49 —— MLO 1972 1 326.77 …….. 6.72 ppm difference
        BRW 1972 2 334.17 —— MLO 1972 2 327.63 …….. 6.54
        BRW 1972 3 334.11 —— MLO 1972 3 327.75 …….. 6.36
        BRW 1972 4 334.52 —— MLO 1972 4 329.72 …….. 4.80
        BRW 1972 5 335.58 —— MLO 1972 5 330.07 …….. 5.51
        BRW 1972 6 333.54 —— MLO 1972 6 329.09 …….. 4.45
        BRW 1972 7 324.88 —— MLO 1972 7 328.05 …….. -3.17 (BRW < MLO)
        BRW 1972 8 318.78 —— MLO 1972 8 326.32 …….. -7.54 (BRW < MLO)
        BRW 1972 9 321.86 —— MLO 1972 9 324.93 …….. -3.07 (BRW < MLO)
        BRW 1972 10 327.08 —– MLO 1972 10 325.06 ……. 2.02
        BRW 1972 11 330.51 —– MLO 1972 11 326.50 ……. 4.01
        BRW 1972 12 333.37 —– MLO 1972 12 327.55 ……. 5.82
        BRW 1973 1 334.67 —— MLO 1973 1 328.54 ……. 6.13
        BRW 1973 2 335.34 —— MLO 1973 2 329.56 ……. 5.78
        BRW 1973 3 336.44 —— MLO 1973 3 330.30 ……. 6.14
        BRW 1973 4 336.94 —— MLO 1973 4 331.50 ……. 5.44
        BRW 1973 5 336.54 —— MLO 1973 5 332.48 ……. 4.06
        BRW 1973 6 334.28 —— MLO 1973 6 332.07 ……. 2.21
        BRW 1973 7 327.83 —— MLO 1973 7 330.87 …… -3.04 (BRW < MLO)
        BRW 1973 8 322.30 —— MLO 1973 8 329.31 …… -7.01 (BRW < MLO)
        BRW 1973 9 323.48 —— MLO 1973 9 327.51 …… -4.03 (BRW < MLO)
        BRW 1973 10 328.36 —– MLO 1973 10 327.18 ……. 1.18‬
        BRW 1973 11 331.93 —– MLO 1973 11 328.16 ……. 3.77
        BRW 1973 12 334.92 —– MLO 1973 12 328.64 ……. 6.28

        According to the above “monthly” CO2 ppm data, both the Barrow and Mauna Loa data has an identical bi-yearly (seasonal) cycle, wherein the CO2 ppm increases from the end of month 9 (September) to mid-May (month 5), ….. at which time the CO2 ppm starts decreasing and will bottom out at the end of September, thus completing its “yearly cycle”.

        Also according to the above “monthly” CO2 ppm data, the Barrow CO2 ppm is consistently greater than the Mauna Loa “monthly” CO2 ppm data, ….. with the difference denoted in the right-hand column.

        Consistently greater than ….. except for the summer months of July (7), August (8) and September (9) …. at which time the Barrow atmospheric CO2 ppm “goes negative”, decreasing below the Mauna Loa CO2 ppm quantities.

        And the only actual, factual, logical reason for the Barrow CO2 ppm to go “negative” (compared to Maun Loa) …… is exactly what Donald L. Klipstein stated in his above quoted comment.

        The temperature of the ocean surface waters is the ‘control knob’ for atmospheric CO2 ppm.

    • The population has not been decimated enough to lower the CO2. “They” will have to try harder with the next pandemic.

  5. Ohio has confirmed through anti-body testing that the first cases in Ohio were as early as January 7. They say 6 people in 6 separate counties in Ohio on January 7, that is a full 60 days earlier than the previous origin date in Ohio of March 6.

    Now let’s all use common sense. If COVID-19 was in at least 6 separate counties in Ohio as early as January 7 and Ohio didn’t shut down until March 20th that’s a lot of time for the virus to spread. Where was the widespread death in Ohio in January, February and early March?

    Also take note that Ohio and Michigan had schools close for a few days to a full week in late January and early February because so many students were out sick.

    This virus sat in Ohio for nearly 90 days before the Governor shut Ohio down and did nothing? Huh? It didn’t start doing anything until after the shutdown? huh? Oh it did things before the shutdown, like get schools closed and the death rate wasn’t outrageous so nothing was really noticed. The question now is, why was Ohio shutdown for part of March, all of April and now soon to be all of May for a virus that was here for at least 90 days before the shutdown and no one noticed.

    • Asking the question is answering it: no hype, no panic, flu-business as usual.
      The media is the virus.

    • Good questions. It would be interesting to learn if the school closings in January/February were due to COVID-19 or flu. Are there plans to do that?

    • Ohio has confirmed through anti-body testing that the first cases in Ohio were as early as January 7.

      You need to avoid rewriting facts which you read to fit your bias.

      The Ohio cases were people who found to have sars-cov-2 anti-bodies recently. That is reason to *suspect* they may have suffered from COVID in January. It does not prove or “confirm” that was the case.

      It is equally possible that they have had some contact with virus in the 90 days since.
      If those people were infected, what R0 would be needed for them to account for current infections in the state?

      Don’t build your arguments/opinions on such flimsy evidence.

      • Well, using Governor DeWine and Dr. Amy Acton’s own COVID-19 Chart of expected peak from onset. March 1 onset to peak mid-April. 1 1/2 months from onset to peak. Well guess what happened mid-February in Ohio? 1 1/2 months from onset that you try to dispell. Well everybody was super sick in mid-Feb. Remember your facebook feed on Feb. 14th, everyone saying how sick they were and no kisses or date nights cause they are out with sickness. The peak was clearly in mid-February. Don’t throw obvious life facts out to build your argument that the gov’t is saving your life.

    • Don’t worry, the “authorities” in Ohio are still using the Imperial model, and wondering “where is the huge peak?” They keep counting “cases”, the number of positive tests, but not telling us how many are active, and counting “hospitalizations” as a total, and not the number actually in the hospital. They either can’t, or don’t want to see that there aren’t ever going to be 200,000 cases in Ohio, no matter how hard the numbers are bent.

    • Jared
      A couple of observations: In the beginning, no one was aware that it was present in Ohio. Would you expect a reaction to to something that no one knew was here? The other thing is that the governor has already started to open things and virtually everything (except schools) will be open in two days — NOT all of May!

      Exponential growth is difficult to discern in the early stages because the numbers are small, and what growth is present appears linear. Numbers alone aren’t sufficient to justify an unprecedented reaction.

  6. A good question to ask about such findings is “So what?” The results are not especially surprising, and the present circumstance is unsustainable without increasing levels of government coercion. What lessons does one learn from such a study? That “scientists” have an absurdly narrow focus? Do we need confirmation of that?

    • Trump needs to put tariffs on importing jap motorcycles as well. Should have been done long ago.

      • It was done many years ago. Do you remember all of the 700cc Japanese bikes? That was because there was a tariff placed on bikes bigger than 700 cc to protect Harley Davidson which only produced large capacity bikes.

  7. Info from Germany: In more towns the official measuring stations could not detect any changes (or only very small changes) concerning the concentration of NO2 and PM2.5 although the car traffic was reduced up to 80%. For this reasons some German towns will now lift up (abandon) the diesel ban.

  8. “AGU is an international association of more than 60,000 advocates and experts in Earth and space science………live our values, which we do through our net zero energy building…”

    When the first round of renewable saviors occurred I took (1970s) a NSF sponsored short course in thermodynamics. As a biologist I guess I need to take the modern version. I wasn’t taught to be an advocate, just try to keep learning on the expert route.

  9. The climate modelers have used air pollution as the reason the atmosphere has not warmed to the degree that the models have projected. So shouldn’t we soon be seeing a rapid increase in warming now that air pollution has declined?

  10. From the article: “Fundamental to our [AGU] mission since our founding in 1919 is to live our values, which we do through our net zero energy building in Washington, D.C.”

    I wonder if the AGU put “live our values” in the 1919 version of their description? I have a feeling this phrase is a more recent addition to their description. It looks like modern-day, “lefty”, virtue signalling lingo to me.

  11. When our children were small, we lived for a year about 500 metres from the chimney of a major copper smelter, just a neat distance to be immersed in sulphur dioxide hundreds of times a day, every day. Before SO2 scrubbers were installed.
    This was a demonstration of the natural resilience of the human body, to cope with various substances that are now generically labelled as pollutants, in their thousands.
    So it is with oxides of nitrogen and with ozone. From time to time and place to place, the human body meets elevated levels that evolution has allowed it to handle. Until the dose gets “dangerous”.
    At this point, politics enters the equation. We have 2 types of practical dangerous doses, one that makes most people physically unwell and one that makes bureaucratic health regulators imagine that people are unwell. The second is a much lower level, as in we must take action when we detect small levels, or we regulators will have no jobs and no reason for them.
    It is a sham. There is a huge cost for satellite sensing systems of dubious accuracy whose main political purpose is to alarm the populace.
    It is like dangerous snakes in Australia. If you leave them alone and move away, you minimise harm. If you hang around and play with them, you can die. Nature at work.
    For goodness sake, leave alone our current obsessions to measure sciencey things for the purpose of spreading bureaucratic fear. We are up to the eyeballs with such misuse of science a la global warming, radioactivity, pesticides and just about every chemical ever made by mankind. So sad. Geoff S

  12. If all this stuff is now reduced in the atmosphere, why can’t the new global cooling be measured? Aren’t we supposed to be worried about global warming? which is supposed to be caused by emissions? Which are lower?

  13. What didn’t happen is any reduction in the rate of rise of Atmospheric CO2 concentrations. They continue to rise unabated by the shutdowns.

  14. Absolutely SUPER! At the cost of trillions of dollars and millions of jobs, the number of dust particles in some heavily-urbanized areas has dropped some! Go, lockdown!

  15. And yet they still say we had the hottest April in all of recorded history.

    It was actually quite cool here in most of the US, and in India and in China. So we are to take it on faith that the overall world temperature was warm, based on readings taken in places where most people don’t live.

    One (or both) of two things can be inferred from this:
    1. Man-made global warming cannot possibly be true, or we would have seen at least a small dip in warming. Not a huge effect, but at least a tenth of a degree of cooling or a leveling off, or something, or;
    2. They are lying about how hot it is.

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