Emissions of several ozone-depleting chemicals are larger than expected

Recovering and safely destroying the sources of these chemicals could speed ozone recovery and reduce climate change

Massachusetts Institute of Technology

In 2016, scientists at MIT and elsewhere observed the first signs of healing in the Antarctic ozone layer. This environmental milestone was the result of decades of concerted effort by nearly every country in the world, which collectively signed on to the Montreal Protocol. These countries pledged to protect the ozone layer by phasing out production of ozone-depleting chlorofluorocarbons, which are also potent greenhouse gases.

While the ozone layer is on a recovery path, scientists have found unexpectedly high emissions of CFC-11 and CFC-12, raising the possibility of production of the banned chemicals that could be in violation of the landmark global treaty. Emissions of CFC-11 even showed an uptick around 2013, which has been traced mainly to a source in eastern China. New data suggest that China has now tamped down on illegal production of the chemical, but emissions of CFC-11 and 12 emission are still larger than expected.

Now MIT researchers have found that much of the current emission of these gases likely stems from large CFC “banks” — old equipment such as building insulation foam, refrigerators and cooling systems, and foam insulation, that was manufactured before the global phaseout of CFCs and is still leaking the gases into the atmosphere. Based on earlier analyses, scientists concluded that CFC banks would be too small to contribute very much to ozone depletion, and so policymakers allowed the banks to remain.

It turns out there are oversized banks of both CFC-11 and CFC-12. The banks slowly leak these chemicals at concentrations that, if left unchecked, would delay the recovery of the ozone hole by six years and add the equivalent of 9 billion metric tons of carbon dioxide to the atmosphere — an amount that is similar to the current European Union pledge under the UN Paris Agreement to reduce climate change.

“Wherever these CFC banks reside, we should consider recovering and destroying them as responsibly as we can,” says Susan Solomon, the Lee and Geraldine Martin Professor of Environmental Studies at MIT, who is a co-author of the study. “Some banks are easier to destroy than others. For instance, before you tear a building down, you can take careful measures to recover the insulation foam and bury it in a landfill, helping the ozone layer recover faster and perhaps taking off a chunk of global warming as a gift to the planet.”

The team also identified an unexpected and sizable source of another ozone-depleting chemical, CFC-113. This chemical was traditionally used as a cleaning solvent, and its production was banned, except for in one particular use, as a feedstock for the manufacturing of other chemical substances. It was thought that chemical plants would use the CFC-113 without allowing much leakage, and so the chemical’s use as a feedstock was allowed to continue.

However, the researchers found that CFC-113 is being emitted into the atmosphere, at a rate of 7 billion grams per year — nearly as large as the spike in CFC-11, which amounted to about 10 billion grams per year.

“A few years ago, the world got very upset over 10 gigagrams of CFC-11 that wasn’t supposed to be there, and now we’re seeing 7 gigagrams of CFC-113 that wasn’t supposed to be there,” says lead author of the study and MIT graduate student Megan Lickley. “The two gases are similar in terms of their ozone depletion and global warming potential. So this is a significant issue.”

The study appears in Nature Communications. Co-authors with Lickley and Solomon are Sarah Fletcher, and Kane Stone of MIT, along with Guus Velders of Utrecht University, John Daniel and Stephen Montzka of the National Oceanic and Atmospheric Administration, Matthew Rigby of the University of Bristol, and Lambert Kuijpers of A/gent Ltd. Consultancy, in the Netherlands.

From top to bottom

The new results are based on an analysis the team developed that combines two common methods for estimating the size of CFC banks around the world.

The first method is a top-down approach, which looks at CFCs produced around the world, based on country-by-country reporting, and then compares these numbers to actual concentrations of the gasses and how long they persist in the atmosphere. After accounting for atmospheric destruction, the difference between a chemical’s production and its atmospheric concentrations gives scientists an estimate of the size of CFC banks around the world.

Based on recent international assessments that use this top-down approach, there should be no CFC banks left in the world.

“But those values are subject to large uncertainties: Small differences in production values or lifetimes or concentrations can lead to large differences in the bank size,” Lickley notes.

The second method is a bottom-up approach, which uses industry-reported values of CFC production and sales in a variety of applications such as refrigeration or foams, and estimates of how quickly each equipment type is depleting over time.

The team combined the best of both methods in a Bayesian probabilistic model — a hybrid approach that calculates the global size of CFC banks based on both atmospheric data, and country and industry-level reporting of CFC production and sales in various uses.

“We also allow there to be some uncertainties, because there could be reporting errors from different countries, which wouldn’t be surprising at all,” Solomon says. “So it’s a much better quantification of the size of the bank.”

Chasing a lost opportunity

The CFC banks, and the sheer quantity of old equipment storing these chemicals around the world, seem to be larger than any previous estimates. The team found the amount of CFC 11 and 12 stored up in banks is about 2.1 million metric tons — an amount that would delay ozone recovery by six years if released to the atmosphere. This CFC bank is also equivalent to about 9 billion metric tons of carbon dioxide in terms of its effect on climate change.

Interestingly, the amount of both CFC-11 and CFC-12 that is being emitted from these banks is enough to account for the recently observed emissions in both gases.

“It really looks like, other than the extra amount being produced in China that seems to have stopped now, the rest of what we’re seeing is no mystery: It’s just what’s coming out of the banks. That’s good news,” Solomon says. “It means there doesn’t seem to be any further cheating going on. If there is, it’s very small. And we wanted to know, if you were to recover and destroy these building foams, and replace old cooling systems and such, in a more responsible way, what more could that do for climate change?”

To answer that, the team explored several theoretical policy scenarios and their potential effect on the emissions produced by CFC banks.

An “opportunity lost” scenario considers what would have happened if all banks were destroyed back in 2000 — the year that many developed countries agreed to phase out CFC production. If this scenario had played out, the measure would have saved the equivalent of 25 billion metric tons of carbon dioxide between 2000 and 2020, and there would be no CFC emissions lingering now from these banks.

A second scenario predicts CFC emissions in the atmosphere if all banks are recovered and destroyed in 2020. This scenario would save the equivalent of 9 billion metric tons of carbon dioxide emitted to the atmosphere. If these banks were destroyed today, it would also help the ozone layer recover six years faster.

“We lost an opportunity in 2000, which is really sad,” Solomon says. “So let’s not miss it again.”


This research was supported, in part, by VoLo foundation. Solomon is also supported by a Lee and Geraldine Martin Professorship.

Written by Jennifer Chu, MIT News Office

From EurekAlert!

54 thoughts on “Emissions of several ozone-depleting chemicals are larger than expected

  1. So CFC s are still causing global warming therefore CO2 does not cause as much as thought. Charney sensitivity of 0.85 K or less, anyone?

    • Has nobody asked the obvious question: Since these super banks or whatever they are monickered do exist and have existed …and the ozone hole over Antarctica is “repairing” doesn’t that indicate that perhaps these CFC super banks are not reason for the cyclical ozone hole size?

      • At least a significant part of the loss of stratospheric ozone was Mt. Pinatubo and El Chichon eruptions. Their sulfphate aerosols destroyed 5-8% of ozone at the time. Falsely attributing this to CFCs allowed “amazingly successful” Montreal protocol.

        “Healing” has been in large part due to the lack on any major eruptions on that scale since.

        Interestingly, the amount of both CFC-11 and CFC-12 that is being emitted from these banks is enough to account for the recently observed emissions in both gases.

        It is not “interesting” ( by which they are presumably trying to imply it proves they were right ) , it just means they tuned the largely uncertain parameters in their models to get the results they expected/wanted.

        Isn’t climate science easy? Start with your agenda and tweak to fit.

        • That 1991 Mt. Pinatubo eruption shot more “ozone depleting chemicals” (ODCs) into a single location in the upper atmosphere than all human emissions for the full year combined. NASA detected that massive amount of ODCs drifting toward Canada and warned that there would be massive depletion of ozone over Canada that summer. I well recall the three inch black headlines.

          It didn’t happen of course, and in the Autumn of that year, there appeared in the same newspaper, a small column in the back pages telling us that scientists couldn’t understand why. I knew why the scientists were puzzled – it was because they listened to enviro-doomsters instead of checking out the well known science about ozone.

      • I have pointed out numerous times that the ozone holes have an annular ring of much higher ozone density around them, this means ozone “depletion” is to a signicant extent really redistribution, like the rolled collar of a turtleneck sweater. How would a chemical cause do this? It wouldn’t.

      • Since ozone O1 is created from 02 by passing high current electricity thru 02 (think lightening, from thunderstorms) how do these geniuses figure anything can repair the hole in the Antarctic ozone layer? Thunderstorms are a summer phenomenon, and I am damn sure you won’t find thunderstorms in a region where the average daily “summer”temperature is 18 degrees below ZERO F! Along with that question, how will you MELT the block of ice known as the continent of Antarctica, when the average daily temperature is 59 degrees BELOW Zero F?
        Just a curious observer of the insanity called “glow bull warming”.

  2. Can someone explain how surface CFC emissions from eastern China reach the stratosphere over Antarctica?

          • The ozone depletion happens in the Antarctica due to the very low temperature, -80°C is what kills ozone.
            Ozone is being continuously produced by UV and the molecules have a lifetime of several weeks if I correctly remember, however during South hemisphere winter there is no UV in the area…

        • It’s not, though there are differences between poles.

          The Arctic has an ocean, the Antarctic has a continent. Among other things, these impact temperature, wind, clouds, humidity, weather basically.

        • The ozone “hole” is caused by sunlight hitting the polar atmosphere, due to the Earth’s orbital tilt. Hence the seasonality. The variablity during the year is high, +/- 50%. So the measures calculated in this study are mostly conjecture. Yes, there obviously are reservoirs of scrapped materials breaking down and emitting CFC’s. The decision to bury the stuff was a cheap concession to get a treaty, instead of destroying the CFC containing materials and the CFC at the time.

        • The circumpolar current that flows around Antarctica tends to not only isolate the land mass from the warm waters flowing southward, but it also tends to create wind patterns that isolate the air mass sitting on top of Antarctica.

          In the case of the Northern pole, no such major current of flowing water isolates the Arctic Ocean or the air mass above it. Ergo, there is more mixing in the North.

        • Scouser
          “What’s the South Pole, not the North Pole”
          Temperature. The Antarctic is much colder, for longer, surface and vertically.

    • NASA has satellite and aircraft instruments that can detect stratospheric CFC’s over Antarctic (and elsewhere). Read links below for more details. What is puzzling to me is why has this problem only manifested itself over the Antarctic, the furthest point from ‘culprits’ emitting these gases? I believe there is an ozone-destroying process going on here, but its effects have been hyped up and politicized. The antarctic ozone holes appear to be affected more by stratospheric vortexes than CFCs.

      “Scientists discover the source of new CFC emissions [using detector in South Korea]”

      “Large amounts of reactive stratospheric chlorine in the form of chlorine monoxide (ClO) that could only result from the destruction of ozone by the CFCs in the stratosphere were observed by instruments onboard the NASA ER-2 aircraft and UARS (Upper Atmospheric Research Satellite) over some regions in North America during the winter of 1992”


      • As I know it is because Arctic and Antarctic are pure Ozone sinks. Ozone is created by lightning in tropical and moderate areas and transported to poles.
        So lower concentration of Ozone is most profound in polar areas.

        • LOL, it’s a natural depletion. The Antarctic ozone “hole” appears in the winter and disappears in the summer. Why? Because ozone is formed by the action of UV light on oxygen. In the polar regions there is a dearth of sunlight (which is where the UV comes from) in winter, so the ozone turns back to oxygen. At the same time, every winter there is a weather pattern that forms, the Antarctic polar vortex, that prevents ozone from coming in from the north. In the Arctic there is not ozone hole forming. Why? Because there is no similar arctic polar vortex in the north to keep it out.

          • Scissor, yeah I’ve seen a few of those studies that claim to support the lie. I’ve also seen a couple of them debunked so I don’t trust any of them. They all come up with one excuse or another to explain why the “hole” is still there decades later.

            Occam’s Razor – it’s natural. Human influence on Ozone is about as effective as human CO2 emissions are on global temperature.

      • Hydrogen fluoride has been a known product of volcanic eruptions since at least 1984

        Impact of volcanic fluoride and SO2 emissions from moderated activity volcanoes on the surrounding vegetation

        Human toxic fluorosis results from volcanic emissions Review here,

        E.g., “One of the main sources [of HF] is represented by volcanic activity, which releases magmatic fluorine generally as hydrogen fluorine through volcanic degassing. For example, Mt. Etna in Italy is considered the greatest point source at the global scale, releasing on average 70 Gg of HF each year.

        Human Fluorosis Related To Volcanic Activity: A Review

        Ten Gg of CFC-11 provides 1.4 Gg of fluoride to the environment, assuming complete breakdown. Etna all by itself produces 50 times more than that annually.

        Seven billion grams of CFC-113 provides 2.1 Gg of fluoride. Etna alone produces 33 times more than that annually.

        Etna and other volcanoes have been releasing huge amounts of fluorine all through recorded history. And yet the ozone layer survived into modern times.

        It appears fluorine shares a special property with CO2. When they’re natural, HF and CO2 are harmless. When humans produce them, the planet dies.

    • It´s very intelligent molecule. It goes to place where it makes no harm.
      Isn´t this ozone hole thing related to sun? Because I think all these protocol things has always something to do with politics and taxes and benefits to a good pal.

    • That warm air moves to the cold areas seems logical to me. It’s schoolboy science.

      Not sure how it crosses the equator though.

    • The answer is NO, NO, no one can explain that anymore than they could explain how CFC emissions from the US and Canada could reach that same hole. 30 years ago.
      It is a scam supported by grants to study it. If they admit there is nothing we can do about it, because it is a natural phenomenon, they lose funding for their farce, and have to find a real job.

  3. It turns out there are oversized banks of both CFC-11 and CFC-12.

    OMG! It’s the Attack of the Giant Freon Banks! What will we do? Who will save us?

    • First run, then let UN take care of it because UN have very cost-effective solution to everything.

      • But this is based on starting values that
        1 “are subject to large uncertainties”
        2 use ” industry-reported values of CFC production and sales in a variety of applications such as refrigeration or foams, and estimates of how quickly each equipment type is depleting over time.”

        These less-than certain figures (‘estimates’) are combined in a model – ” The team combined the best of both methods in a Bayesian probabilistic model”; the writer, Jennifer Chu, of MIT News Office, didn’t explain how ‘the best’ bits were selected.
        Is it select your outcome, then select – or torture – your data to fit?

        As an aside – “the researchers found that CFC-113 is being emitted into the atmosphere, at a rate of 7 billion grams per year ” – 7 billion grams is 7 million Kg – or 7,000 tonnes – over a year, that is the slightly less scary-sounding 20 tonnes or so each day [globally]. CFCs are probably not good, but the emotive use of billions perhaps indicates a need for more study – sent grants?


  4. Seven billion grams? Who uses grams for very large numbers, except to make it seem big and scary? That’s just 7000 metric tons in an atmosphere weighing 5×10^15 metric tons, or a bit over a part per trillion. Can they even measure a substance to that accuracy averaged throughput the atmosphere?

    • Can they even measure a substance to that accuracy averaged throughput the atmosphere?

      Remarkably, Yes!
      The invention of the ECD created the ability to see things that no-one ever knew were there. Which seemed to worry people far more than than the sweet ignorance we lived through before.

      It was invented by Lovelock of Gaia Hypothesis fame. This is not a coincidence.

    • Why I am shocked, shocked, I say, at your lack of credulity when confronted by expert models supported by illustrious MIT professors! If practitioners of homeopathic medicine think that one part in a trillion can have a significant therapeutic effect, who are we to question comparable enviro-modelling assessments as applied to the atmosphere?

      Aside from the reliance on ‘small fractions as significant’ that we see in this head posting, it really jumps out that the attribution of cause and effect is in no way corroborated (the true causes of environmental happenings being hard to establish in any case). Indeed, the article here seems confused, contradictory, without even a consistent story to tell here!

      The article, or head posting, starts by saying,

      “In 2016, scientists at MIT and elsewhere observed the first signs of healing in the Antarctic ozone layer. This environmental milestone was the result of decades of concerted effort by nearly every country in the world..”

      Then an MIT graduate student is quoted as saying,

      “A few years ago, the world got very upset over 10 gigagrams of CFC-11 that wasn’t supposed to be there, and now we’re seeing 7 gigagrams of CFC-113 that wasn’t supposed to be there,”

      So what these very finely calibrated measurements seem to be telling us is that the 1987 Montreal Protocol was basically *unsuccessful* at removing *all* or even *most* of the “suspect” CFC molecules! If one is optimistic about the above grad student’s statement, one might think that possibly the “damaging” emissions have been reduced by 30 percent? However, where is the proof or the plausibility that this would put the ozone layer “on the road to recovery’? Do they really have any idea as to what the normal or usual ozone concentration over Antarctica is, or any idea as to what the natural trends over many decades ever were to begin with?

    • Pflashgordon

      Let us look at the whole whole equation. Well… there isn’t space so how about a couple of other factors: Bromine and bromocarbons.

      Emission of Methyl Bromide from Biomass Burning

      Biomass puts up 10-50 gigagrams per year and the oceans produce more than twice that. The ocean around Antarctica is a major source of bromocarbons that affect the atmosphere nearby.

      Climate-induced change in biogenic bromine emissions from Antarctic coastal waters

  5. In equally alarming news, ~7 billion humans are exhaling CO2 in unprecedented quantities.

    The same solution as proposed in this paper (put the sources into a landfill) would be acceptable to UN no doubt.

  6. “Wherever these CFC banks reside, we should consider recovering and destroying them as responsibly as we can,” says Susan Solomon,

    Hang about….why was the EU paying China to “destroy” co-production of the “wrong” sort of CFC’s for so long? When it comes to such “offsets” there is more horseplay can one can shake a stick at. Chinese factories producing the right kind of CFC’s were producing as a byproduct some of the wrong kind. The factories were paid by the EU $100,000 per ton to destroy it which means putting it back in the production process as a pre-cursor. Of course tuning the production system could alter the amount of accidental production. The result? 2.7 billion clean air dollars.

    So who is going to destroy these CFC Banks?
    And by which method?

    Is this paper really a roundabout way to explain why the ozone hole is not change in size save fluctuating from year to year? There are many contributing chemicals to braking down O3 including bromine. The main source of bromine in the atmosphere are the oceans which emit it, together with H2S and all sorts of other things. I appreciate their enthusiasm over the control of CFC’s but perhaps it can be ignored until there is a means of capping the oceans. Drop in the bucket and all that.

  7. A million grams is more familiarly called a ton. Why the heck are we talking about gigagrams?

  8. “the first signs of healing in the Antarctic ozone layer.”

    Yeah, right. Every year for the past 30 years, someone announces the “first signs of healing”. How many “first signs” can there be before it “heals”?

    A more relevant question – how many years until they admit it was all a hoax?

    • Maybe Willis E. can put together a post on the eleventy-leventh first sign of a healing ozone hole. 🙂

  9. When the Montreal Protocol was adopted, there was no convincing scientific evidence that the ozone “hole” above Antarctica was due to the CFC effect. Moreover, this assumption did not explain the obvious fact of the absence of an ozone “hole” in the stratosphere over the regions where CFCs were produced.
    The Molina and Rowland hypothesis, published more than 40 years ago, contained neither experimental evidence of the reaction of CFCs with ozone in the stratosphere conditions, nor an explanation of how CFC molecules, which are 4-5 times heavier than air, enter the stratosphere. These authors used the binding energy in an oxygen molecule to calculate the maximum wavelength of the radiation that breaks down this bond (240 nm). However, they “forgot” to apply the same method to CFC molecules, because it turns out that the C-CI bond in these molecules is cleaved photochemically at wavelengths of 350 – 390 nm. In other words, CFCs decay photochemically already in the lower troposphere, not in the stratosphere.
    In fact, this means that the Montreal Protocol was adopted without proper scientific justification.
    The article under discussion does not contain any new scientific facts confirming the hypothesis about the role of CFCs in the destruction of the ozone layer. The same goes for the greenhouse effect.

  10. As soon as I read the magic words “reduce climate change”, my mind switches off the article and onto other real matters. I immediately recall that the Montreal Protocol was rushed in without any research science. Since then the ‘Ozone Hole’ has gone on as usual.

  11. I would be more convinced this was not a natural fluctuation if we had data on ozone for more than the relatively short data set that is available, and if it was demonstrated that the chlorine radical showed a coinciding decrease that was of the amount that a physical model would predict was required to achieve the change. I didn’t see anything in the article about any real data showing that the active agent had even decreased in the atmosphere in Antarctica. This is essential if one wants to show a scientific relationship between the cause and the effect.

  12. I have always understood it , that the ozone was created by the interaction of the UV rays and oxygen atoms. The ozone is the result of ,,and the process provides the protection from the harmful rays, the ozone is the byproduct. if this is the case should we not want less ozone and more free molecules to interact with the UV rays. The whole Hole in the ozone layer, just another major hoax.

  13. “to recover the insulation foam and bury it in a landfill”

    Because landfill won’t allow CFC’s through?

  14. A) Scientists “discovered” the ozone hole and immediately activists declared it to be a problem and caused by CFCs.

    B) all of their all alleged data is derived from estimates of estimates…

    This is just a renewal of the specious claim OMG CFCs destroy our ozone over Antarctica.

  15. The Rowland and Molina ozone depletion theory was proved wrong even before the Montreal Protocol was signed. This was simply the first time the UN tried to get an international agreement covering the atmosphere. A trial run for the climate scam.

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