Study Reveals Chemical Link between Wildfire Smoke and Ozone Depletion

If wildfires become larger and more frequent, they might stall ozone recovery for years.

Peer-Reviewed Publication


The Australian wildfires in 2019 and 2020 were historic for how far and fast they spread, and for how long and powerfully they burned. All told, the devastating “Black Summer” fires blazed across more than 43 million acres of land, and extinguished or displaced nearly 3 billion animals. The fires also injected over 1 million tons of smoke particles into the atmosphere, reaching up to 35 kilometers above Earth’s surface — a mass and reach comparable to that of an erupting volcano.

Now, atmospheric chemists at MIT have found that the smoke from those fires set off chemical reactions in the stratosphere that contributed to the destruction of ozone, which shields the Earth from incoming ultraviolet radiation. The team’s study, appearing in the Proceedings of the National Academy of Sciences, is the first to establish a chemical link between wildfire smoke and ozone depletion.

In March 2020, shortly after the fires subsided, the team observed a sharp drop in nitrogen dioxide in the stratosphere, which is the first step in a chemical cascade that is known to end in ozone depletion. The researchers found that this drop in nitrogen dioxide directly correlates with the amount of smoke that the fires released into the stratosphere. They estimate that this smoke-induced chemistry depleted the column of ozone by 1 percent.

To put this in context, they note that the phaseout of ozone-depleting gases under a worldwide agreement to stop their production has led to about a 1 percent ozone recovery from earlier ozone decreases over the past 10 years — meaning that the wildfires canceled those hard-won diplomatic gains for a short period. If future wildfires grow stronger and more frequent, as they are predicted to do with climate change, ozone’s projected recovery could be delayed by years. 

“The Australian fires look like the biggest event so far, but as the world continues to warm, there is every reason to think these fires will become more frequent and more intense,” says lead author Susan Solomon, the Lee and Geraldine Martin Professor of Environmental Studies at MIT. “It’s another wakeup call, just as the Antarctic ozone hole was, in the sense of showing how bad things could actually be.”

The study’s co-authors include Kane Stone, a research scientist in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, along with collaborators at multiple institutions including the University of Saskatchewan, Jinan University, the National Center for Atmospheric Research, and the University of Colorado at Boulder.

Chemical trace

Massive wildfires are known to generate pyrocumulonimbus — towering clouds of smoke that can reach into the stratosphere, the layer of the atmosphere that lies between about 15 and 50 kilometers above the Earth’s surface. The smoke from Australia’s wildfires reached well into the stratosphere, as high as 35 kilometers.

In 2021, Solomon’s co-author, Pengfei Yu at Jinan University, carried out a separate study of the fires’ impacts and found that the accumulated smoke warmed parts of the stratosphere by as much as 2 degrees Celsius — a warming that persisted for six months. The study also found hints of ozone destruction in the Southern Hemisphere following the fires.

Solomon wondered whether smoke from the fires could have depleted ozone through a chemistry similar to volcanic aerosols. Major volcanic eruptions can also reach into the stratosphere, and in 1989, Solomon discovered that the particles in these eruptions can destroy ozone through a series of chemical reactions. As the particles form in the atmosphere, they gather moisture on their surfaces. Once wet, the particles can react with circulating chemicals in the stratosphere, including dinitrogen pentoxide, which reacts with the particles to form nitric acid.

Normally, dinitrogen pentoxide reacts with the sun to form various nitrogen species, including nitrogen dioxide, a compound that binds with chlorine-containing chemicals in the stratosphere. When volcanic smoke converts dinitrogen pentoxide into nitric acid, nitrogen dioxide drops, and the chlorine compounds take another path, morphing into chlorine monoxide, the main human-made agent that destroys ozone.

“This chemistry, once you get past that point, is well-established,” Solomon says. “Once you have less nitrogen dioxide, you have to have more chlorine monoxide, and that will deplete ozone.”

Cloud injection

In the new study, Solomon and her colleagues looked at how concentrations of nitrogen dioxide in the stratosphere changed following the Australian fires. If these concentrations dropped significantly, it would signal that wildfire smoke depletes ozone through the same chemical reactions as some volcanic eruptions.

The team looked to observations of nitrogen dioxide taken by three independent satellites that have surveyed the Southern Hemisphere for varying lengths of time. They compared each satellite’s record in the months and years leading up to and following the Australian fires. All three records showed a significant drop in nitrogen dioxide in March 2020. For one satellite’s record, the drop represented a record low among observations spanning the last 20 years.

To check that the nitrogen dioxide decrease was a direct chemical effect of the fires’ smoke, the researchers carried out atmospheric simulations using a global, three-dimensional model that simulates hundreds of chemical reactions in the atmosphere, from the surface on up through the stratosphere.

The team injected a cloud of smoke particles into the model, simulating what was observed from the Australian wildfires. They assumed that the particles, like volcanic aerosols, gathered moisture. They then ran the model multiple times and compared the results to simulations without the smoke cloud.

In every simulation incorporating wildfire smoke, the team found that as the amount of smoke particles increased in the stratosphere, concentrations of nitrogen dioxide decreased, matching the observations of the three satellites.

“The behavior we saw, of more and more aerosols, and less and less nitrogen dioxide, in both the model and the data, is a fantastic fingerprint,” Solomon says. “It’s the first time that science has established a chemical mechanism linking wildfire smoke to ozone depletion. It may only be one chemical mechanism among several, but it’s clearly there. It tells us these particles are wet and they had to have caused some ozone depletion.”

She and her collaborators are looking into other reactions triggered by wildfire smoke that might further contribute to stripping ozone. For the time being, the major driver of ozone depletion remains chlorofluorocarbons, or CFCs — chemicals such as old refrigerants that have been banned under the Montreal Protocol, though they continue to linger in the stratosphere. But as global warming leads to stronger, more frequent wildfires, their smoke could have a serious, lasting impact on ozone.

“Wildfire smoke is a toxic brew of organic compounds that are complex beasts,” Solomon says. “And I’m afraid ozone is getting pummeled by a whole series of reactions that we are now furiously working to unravel.”

This research was supported in part by the National Science Foundation and NASA.


Written by Jennifer Chu, MIT News Office


Proceedings of the National Academy of Sciences


On the stratospheric chemistry of midlatitude wildfire smoke



Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases

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Mark Pawelek
February 28, 2022 10:17 pm

This chemistry is well-established
<- I think he means the “science is settled” and his model can not be questioned nor refuted, because that’s ‘climate denialism‘ a thought crime like “COVID denialism” which involved criticising anti-COVID lockdowns, .anti-viral medicine bans, mask and vaccine mandates. And we all know stopping COVID denialism was the main reason why humanity was saved from COVID

BTW: Were there any actual empirical chemistry studies cited? Especially empirical studies at the dilutions found near the ozone layers. Or is it all just pie-in-the-sky speculation like 99.9% of climate nihilism and climate modelling.

PS: I may have made a error of fact above. See if you can spot it.

PS 2: In future please publish the DOI number for every journal article you quote to make it easier for me to check.

Reply to  Mark Pawelek
February 28, 2022 10:52 pm

I spotted your error: not 99.9%, actually 100%.

Reply to  Mark Pawelek
February 28, 2022 11:28 pm

The DOI number leads to an error page and there is no sign of the paper on Solomons MIT profile or the PNAS website

Eurika probably made it up from an old press release

It may be this one

Reply to  Mark Pawelek
March 1, 2022 4:21 am

There are several airplane field studies being done to look at atmospheric constituents from wildfires, so it’s not all modeling. Keep in mind that every problem is exaggerated to some extent for funding reasons.

It would be nice if researchers would acknowledge that wildfires in general are infrequent events or at least seasonal, so the impacts stated may be very significant but only on relatively short time basis.

If one is interested in some of these field studies the following link is explanatory.

February 28, 2022 10:48 pm

Hmmmm. This study does not ring true. They claim that ten years of Montreal Protocol has a 1% effect on ozone. That’s pretty close to stuff-all. I doubt that anyone has ever established that ozone does not cycle. Until they do, studies like this have no merit.

Reply to  Mike Jonas
February 28, 2022 11:33 pm

I read a report that stated the Montreal Protocol was created by the chemical/mechanical industry to sell alternate refrigerants? Billions, if not trillions were spent replacing all the mechanical chillers using R-11, 12, and 22.

Reply to  Brad
March 1, 2022 2:38 am

How many people have died in fires caused by modern refrigerators with inflammable coolant?

Reply to  Roger
March 1, 2022 7:48 am

Roger, please provide the number and reference.

Tom in Florida
Reply to  Brad
March 1, 2022 6:17 am

All new residedntial refrigerators must now us R600A as the coolant.
See here for more info:

Reply to  Mike Jonas
March 1, 2022 6:29 am

“This study does not ring true”

I agree. It is my understanding the ozone “scare” is established nonsense.

The fluctuating, pulsing polar holes of the ozone layer were regarded as evidence of its depletion from human activity. Some industrial compounds (chlorofluorocarbons or CFC’s) chemically react with the O3 molecule of the ozone layer of the stratosphere thus depleting it. There are other explanations; the ozone layer is relatively thin (at 1 atm it would be less than 1/8 of an inch thick) and in a constant state of replenishment as well as depletion. 12 to 25 miles up high energy UV splits the O2 molecule into two atomic O1 molecules that then combine with O2 to form the unstable, temporary O3 ozone molecule which absorbs low energy UV.  

I thought it was understood the main reasons for the changing polar ozone hole sizes are natural and include the seasonal lack of light, the atmospheric fluid dynamics of the polar vortices, fluctuations with naturally occurring nitrous oxide and most importantly, the solar variances in UV radiation. 

February 28, 2022 10:48 pm

Complete negation of reality? “ They assumed that the particles, like volcanic aerosols, gathered moisture. They then ran the model multiple times and compared the results to simulations without the smoke cloud.”
How many times did they run the models, and what tweaks did they perform to get the answer they wanted?

Geoff Sherrington
Reply to  Brad
February 28, 2022 11:13 pm

Another study found ” Furthermore, the injected mass of water was estimated to be very high (27±10 Tg, about 3% of the total mass of stratospheric overworld water vapor in the southern extratropics).” Australian wildfire smoke in the stratosphere: the decay phase in 2020/21 and impact on ozone depletion. Kevin Ohneiser et al, 2022.
The products of the fire were examined in the stratosphere. There were not many prior studies with appropriate instruments from earlier large fires, so new ground is being broken and it is prudent to read and learn.
That said, as a chemist, I have never been satisfied that the ozone chemistry story is accurate, complete or well-understood. What is known does not appear to be adequate for making global policies.
Also, a number of studies and opinion pieces poured out after these 2019-10 Australian fires, noting that one cause of their size and duration was not climate change.
It was the accumulation of fuel in the forests following decades of little management of excess fuel, as through timber harvesting, thinning and controlled burning for fuel reduction. Therefore, logically, it was nothing to do with climate change and all to do with the natural growth of forest species over many decades. Hard to manage. Geoff S

Reply to  Geoff Sherrington
February 28, 2022 11:27 pm

Yes, it was not a yearly occurrence. It would take decades to “rebuild” the fuel source for it to happen again.
The USA also has terrible forest management, preventing sustainable harvesting that would eliminate the problem. I think we import much of our lumber from Canada?

Clyde Spencer
Reply to  Geoff Sherrington
March 1, 2022 5:22 pm

There are invariably rings of anomalously high ozone outside the depleted zone. It is because the polar vortex keeps the ozone generated in the tropics from mixing with the ozone-depleted air resulting from extreme cold. When the vortex breaks up in the Spring, the high-ozone-content air moves in and restores the O3 concentration to the Summer values.

February 28, 2022 11:23 pm

The very same Susan Solomon who argued for the 1,000 year residence time of CO2 from a model.

“One of the leading figures in the IPCC, Susan Solomon, has argued for a thousand-year residence time, but her paper starts with a model, and ignores observations. It is a good example of the ‘scary’ AGW paper that assumes that it is completely right, despite the lack of supporting evidence.”

Reply to  lee
March 1, 2022 4:25 am

Her rise in the scientific ranks benefited from being a woman and being a women willing to stretch the truth. I’m glad she’s not in Boulder any more.

Well, actually prior to Covid she still traveled to Boulder quite a bit. In fact, travel is a relatively large percentage of researchers budgets, one that gets swept under the rug.

Peta of Newark
February 28, 2022 11:24 pm

Quote:”smoke could have a serious, lasting impact on ozone.

So what. UV from the sun will simply make some more.
The amount of Ozone in the stratosphere is always in perfect equilibrium with its rate of production ** and its rate of natural decomposition.

** production rate is dependant on the strength of the UV output of the sun – which rather unfortunalty flickers on timescales ranging from minutes to centuries. Slightly sunspot dependant.

Solomon: your work is perfectly contrived shyte and has been since forever.
The DuPont Chemical Company made a complete ass out of you.
Learn some basic 10th Grade school chemistry.

You are doing humankind a mind blowing epic disservice ## with your continued ravings.

Grow up. Admit your mistake. Move on, Retire. Quit

DuPont’s money grubbing & lies, aided abetted by Solomon and her ilk is a crime against humanity yet stupid pride won’t let any of them admit they were fooled

And how many others, including ,any supposedly clear thinking ask answer awkward questions supposed skeptix also?

What a complete fugging mess

## Without Freon inside them, all fridges, freezers and air-cons are using twice as much electricity/energy as they need to.
No other refrigerant gas comes even close to the performance of Freon

Yet these clowns professing care & concern for The Global Climate ignore that.
At which point does stupidity become evil & malicious?

Reply to  Peta of Newark
February 28, 2022 11:45 pm

Very well stated! The replacement refrigerants reduced existing chiller capacity by ~10%, causing existing buildings to be unable to adequately cool the buildings for optimum tenant productivity. Couple that with the Urban Heat Island effect in large cities, and you have a problem. Existing buildings have only one option when tenants complain about it being too warm, they close the outside air dampers to reduce the cooling load. You end up with “sick buildings”. But no one EVER admits that is what they do. IMAGINE THE RESULTING LAWSUITS…

Reply to  Peta of Newark
March 1, 2022 4:36 am

Susan is 66 years old. She’s finished growing up and her shrinking (physically and mentally) began some time ago. She is actually very intelligent and understands atmospheric chemistry at a very high level. She also understands the politics of academic-government science very well and stretches the truth as necessary to play the game.

I’ve attended at least a couple of her talks over the years and she slings propaganda with the best of them.

February 28, 2022 11:51 pm

I thought modern man had decreased wildfires over last 100yrs or so.

Reply to  Macha
March 1, 2022 12:31 am

Then they started rewilding…

Reply to  Macha
March 1, 2022 7:58 am

Yes, plus only a few thousand years ago, there were no wildfires anywhere glaciers covered where today’s boreal forests are located…..
And today’s forests seem to average about 100 years old by tree rings, which might indicate forest fires about that often….

March 1, 2022 12:29 am

So according to their model my fridge was innocent

Reply to  fretslider
March 1, 2022 5:43 am


Reply to  fretslider
March 1, 2022 7:37 am

Frigid-aires Matter

March 1, 2022 3:18 am

Really? So humans, yet again, are not causing climate to change. It is the climate stupid.

March 1, 2022 5:23 am

Ozone? OMG, that is so yesterday and long ago. Not to mention that “science” has been relegated to the back of the bus due to the crap pushed by the Fauxi and that crowd.
“Scientists”? So over with believing what they proclaim. Look for who’s paying them and then use common sense to see who it benefits. Unfortunate outcome of the scamdemic.

Tom Halla
March 1, 2022 5:53 am

Another issue is that wildfires big enough to form pyrocumulonimbus clouds are management failures, of allowing fuel to accumulate too long.
As the Green Blob opposes active wildlands management, it is largely their fault through policy or lawfare.

March 1, 2022 7:02 am

Wildfires sends giant cloud of ash across southern Paraguay | Paraguay | The Guardian

Well there’s ANOTHER once in a century drought with wildfires and huge amounts of smoke…

How long can you keep pretending all these events are just coincidence?

Reply to  griff
March 1, 2022 8:51 am

Where is CO2 in the fire triangle? In fact, CO2 is used to extinguish fires.

Fire triangle consists of ignition, fuel load, and oxygen. If anything, the greening of the earth attributed to higher, more healthy levels of atmospheric CO2 has increased the fuel load across the planet. So green is bad, and it’s worse than we thought (/sarc).

More likely, though, is the forests are not being managed in a manner to prevent catastrophically large fires from happening. How is CO2 to blame for this, exactly?

Reply to  brentc
March 1, 2022 11:10 am

brentc, you have it exactly right. People seem to forget the fundamentals of the fire triangle.

For example, the Marshall wildfire in the Boulder area was due to excess fuel load from our wet drought (that’s a drought that isn’t really a drought) and an ignition source (some ass burning down a utility shed). It was all sustained and made worse by high winds.

Investigators have gone quiet on the burning shed hypothesis, probably because lawyers for that party made some kind of threat. It would appear that Boulder is somewhat culpable for not properly maintaining the “open space” and apparently the fire department drove right by the burning shed at least once without stopping.

Reply to  griff
March 1, 2022 8:57 am

The Guardian is an excellent source of scientific thought. Asking again, Griff where do you get your funding?

Matt Kiro
Reply to  griff
March 1, 2022 10:19 am

If things keep happening , then they aren’t once in a century.

But really, you don’t quite understand what the phrase means

H. D. Hoese
March 1, 2022 11:09 am

The bad thing is that Sigma Xi, Research Honor Society publisher of American Scientist just put this out in their Smart Brief (Your World of Science News). A valuable service, but they too much use second hand sources like CNN, BBC without any commentary other than in link. The don’t even say –“…are not responsible for the accuracy of news releases”

“More People in More Places Trust BBC News than any other news source.” Trust in places like NAS also a serious problem. Wildfires may slow recovery of ozone layer – study

tom hewitt
March 1, 2022 11:53 am

For the time being, the major driver of ozone depletion remains chlorofluorocarbons, or CFCs — chemicals such as old refrigerants that have been banned under the Montreal Protocol, though they continue to linger in the stratosphere.

Chloroflourocarbons are very heavy molecules. The molar mass of R-12 is 120.91 g·mol−1. The molar mass of N2, which makes up almost 80% of the earth’s atmosphere, is 28.0135 g/mol, less than 1/4 of the mass of R-12. Would it be practical to use R-12 rather than helium in the Goodyear blimp? A possible analogy would be that bowling alleys lock their doors at night to keep the balls from drifting off to the stratosphere.

Clyde Spencer
March 1, 2022 5:14 pm

… they note that the phaseout of ozone-depleting gases … has led to about a 1 percent ozone recovery from earlier ozone decreases over the past 10 years.

In case anyone speed-read past that, what it implies is that, at current rates, it will take about 1,000 years for the ozone depletion to ‘recover’ to past levels. The problem, however, is that the ‘recovery’ isn’t consistent. It varies widely, as in, “… the 2020 ozone hole has grown rapidly since mid-August, and covers most of the Antarctic continent – with its size well above average. What is also interesting to see is that the 2020 ozone hole is also one of the deepest and shows record-low ozone values…”

It is commonly recognized that Antarctic weather — cold stratospheric temperatures and strong winds associated with the austral circumpolar vortex — dominates the behavior of Winter-Spring ozone depletion. “The monitoring of the ozone hole over the South Pole must be interpreted carefully as the size, duration and the ozone concentrations of a single hole are influenced by the local wind fields, or meteorology, around the South Pole.”

I think that Solomon and others are engaging in wishful thinking and putting too much faith in their models. The size of the ozone holes has varied considerably since 1987 and doesn’t show the monotonic decrease that would give one a justified reason to extrapolate to even 2050.

March 6, 2022 2:20 am

Peer-Reviewed Publication


Normally, dinitrogen pentoxide reacts with the sun to form various nitrogen species

Stopped reading.

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