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Burt Rutan (the aviator) has put out a critique of climate change:

An Engineer's Critique of Global Warming "Science"

On page 7, this caught my eye:

Modern Human-Extinction Scares

...

• Hole in the Ozone layer, caused by CFCs, 1970s & 1980s (We now know that the Ozone changes were not caused by human CFCs)

I seem to have missed that memo. Wikipedia still mentions CFCs as a cause.

The details of polar ozone hole formation differ from that of mid-latitude thinning, but the most important process in both is catalytic destruction of ozone by atomic halogens. The main source of these halogen atoms in the stratosphere is photodissociation of man-made halocarbon refrigerants (CFCs, freons, halons). These compounds are transported into the stratosphere after being emitted at the surface. Both types of ozone depletion were observed to increase as emissions of halo-carbons increased.

Is there any credible backing for Mr. Rutan's offhand claim?

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    I find no sign of a challenge to the prevailing chlorofluorocarbon mechanism over the past three years at Google scholar: scholar.google.com/… There is much confirmation that CFC's remain the culprit.
    – user951
    Jan 5, 2012 at 19:38
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    He puts a We now know without giving an explanation, let alone some proper reference. Sounds to me like "trust me, although I don't have any proof it must be like that because it was a government plot".
    – nico
    Jan 5, 2012 at 22:36
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    As an engineer, I am deeply embarrassed that Ruttan would decide to critique something outside his field like this for political reasons...
    – Larian LeQuella
    Jan 7, 2012 at 20:30
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    Excepting of course that he has NO CLUE that any and all efforts will be in vain. He presumes that, and it's a totally inappropriate presumption on his part. He, and the many others who display this attitude seem to have not only made themselves victims of Learned helplessness, but want the rest of us to be its victims too. en.wikipedia.org/wiki/Learned_helplessness
    – user951
    Jan 9, 2012 at 2:12
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    Comments are not for chat or the expression of political views. Can we please keep the comments that serve no constructive purpose to chat.
    – Chad
    Jan 10, 2012 at 16:39

3 Answers 3

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While the consensus is that CFCs cause the ozone hole, there is recent evidence that we don't understand it as well as we thought

When I first read the Rutan comments I though he had simply gone nuts in his general skeptical approach to scares (on Skeptics.se we should applaud his skeptical approach unless his evidence is nonsense), but then I uncovered some recent science that might give some grounds for his claim (though not the degree of certainty he expresses).

As far as I can tell the original source is from a Nature news story in 2007 which points out that some recent reevaluations of the reaction kinetics of some of the key reactions involved in ozone depletion had given radically different results to those used in the original models of ozone depletion. As one of the scientists reviewing the results said:

If the measurements are correct we can basically no longer say we understand how ozone holes come into being.

This view had widespread coverage in the press and blogs. But perhaps the most significant comment on a related topic was by James Lovelock and reported on this blog. Lovelock (intimately involved in the science as he invented the key method for detecting small amounts of things like CFCs) is commenting on the recently revealed Climategate emails and their implication of disreputable behaviour by some climate scientists:

We should have been warned by the CFC/ozone affair because the corruption of science in that was so bad that something like 80% of the measurements being made during that time were either faked, or incompetently done.

His comments are interesting as they suggest we reached consensus on the ozone hole a little quickly and, once the bandwagon was established a lot of poor science was done (which, despite being a believer in the consensus of global warming he also thinks is happening there).

More significantly his comments have been widely reported in climate-related blogs and might be read as arguing that CFCs didn't cause the hole. A more careful reading would be that though most experts think they did, we are no longer clear how.

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    To be fair, the article also says that: "The new measurements raise “intriguing questions”, but don't compromise the Montreal Protocol as such, says John Pyle, an atmosphere researcher at the University of Cambridge. “We're starting to see the benefits of the protocol, but we need to keep the pressure on.” He says that he finds it “extremely hard to believe” that an unknown mechanism accounts for the bulk of observed ozone losses."
    – Sklivvz
    Jan 8, 2012 at 20:56
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    I personally don't find ad-hominems against scientists and accusations of deception to be a satisfactory answer to what is a scientific question. Answers like this tend to raise my skepticism, rather than answer it.
    – user18604
    Mar 1, 2014 at 16:13
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    The quote from Lovelock says that some results were faked, that is very obviously an accusation of deception. The second part of your answer is just an ad-hominem with no real evidence that any results were actually faked.
    – user18604
    Mar 2, 2014 at 21:39
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    @matt_black, saying that results were "either faked, or incompetently done" is still an accusation of deception on the part of those producing the faked results, but not the producers of the "incompetently done" results. As I said, the more you try to use rhetoric (e.g. " These are important issues unless you believe scientists form some new, privileged, priesthood and cannot be criticised") instead of discussing the actual scientific point, the less satisfying your argument is.
    – user18604
    Mar 3, 2014 at 11:56
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    I have no problem with the idea that there has been over-confidence in scientific understanding of CFCs, the point I am making is that the ad-hominems and accusations of deception in your answer detract from the point you are making about the science, and only serve to make the discussion partisan and rhetorical, rather than neutral and scientific.
    – user18604
    Mar 3, 2014 at 11:59
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Yes, it is indeed. The ozone hole is still there, and will not recover for another 40 years. Meanwhile, CFCs and other ozone depletion substances (ODS) are banned by the Montreal Protocol.

A 2011 study on the implementation of the Montreal protocol and the effectiveness of the ban is "Science and Diplomacy: Montreal Protocol on Substances that Deplete the Ozone Layer":

The Montreal Protocol on Substances that Deplete the Ozone Layer seeks worldwide phaseout of the production and consumption of ODS. Scientists confirmed that the protocol is working and that the ozone layer is on its way to recovery around the year 2050.

The Ozone Hole web site provides reporting on the ozone layer hole, and as you can see, it's still there in 2011.

Ozone Hole 2011

Then, there is the UN-backed "International Day for the Presevation of the Ozone Layer", to keep the attention up. In reality, HCFCs are hundreds of different substances that need to be phased out. We are gradually getting there.

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    Although you cited very good refs about what has been done to fix the problem, I think your answer does not really tackle the problem of "what caused the ozone hole"? The fact that removing CFC makes the hole get smaller does not imply that the CFC were the cause (correlation is not causation).
    – nico
    Jan 7, 2012 at 11:47
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    As much as I do believe CFC were the cause, I personally don't think that "a single variable change" was what we did. So many things have changed in the last 30 years in terms of how we care for the environment, and some of those may have also affected the ozone hole. Earth is not a gigantic lab where you can change one single variable. Maybe CFCs were causing something else to produce an ozonolytic subtance. What you should really show is some study showing, for instance, that CFCs can break up ozone, they should not be difficult to find.
    – nico
    Jan 7, 2012 at 12:29
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    Is the 1995 Nobel Prize in Chemistry enough proof?
    – Sklivvz
    Jan 7, 2012 at 15:44
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    Sorry, I'm not really much into the subject, so could someone explain: if human produced CFCs are too blame, why is the ozone hole located over the non-populated continent in the middle of less populated hemisphere? Wouldn't it be expected to be much bigger on northern hemisphere, given that most developed countries which were using CFCs are located there?
    – vartec
    Jan 9, 2012 at 9:55
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    @Sklivvz: well, thing is that it's not CFCs, but halogens contained withing them, that affect ozone. There are natural sources of halogens (eg. chloromethane from oceanic biomass). For example it's produced by algae like Gigartina skottsbergii which grows (surprise) in the antarctic region.
    – vartec
    Jan 9, 2012 at 12:18
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alas ... since oxygen-2 is diamagnetic it will be attracted to the poles. the more oxygen-2 up there the larger the area or volume of the oxygen-2. when oxygen-3 breaks down into oxygen-2 the -2 heads to the poles and forces the -3 away from the poles forming a 'hole' for lack of better terms.

oxygen-3 (Ozone) breaks down for many reasons. CFCs are just one. but the problem is the chlorine is a catalyst and can cause a geometrically larger increase for contribution than say CME coronal mass ejections. the shift to FCs has helped return the o-2/0-3 to the natural state.

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