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Sherwood Rowland, CFCs, ozone depletion and the public role of scientists

Filed under: — group @ 13 March 2012

Many of you will have read the obituaries of the Nobel Prize-winning chemist Sherwood Rowland (Nature, BBC) who sadly died over the weekend. DotEarth has a good collection of links to papers, videos and tributes.

We have sometimes commented on the connections between the issue of CFC-driven ozone depletion and anthropogenic global warming. In both cases, there is a global atmospheric problem caused by specific emissions, that has a potential to be dangerous, for which the science provided strong evidence for (but never absolute proof), and for which observations ran ahead of predictions for many years. In the ozone case, this led to important preventative actions (via the Montreal Protocol and its amendments). There are of course links that go deeper than just analogies – ozone depletion itself has a small cooling effect, CFCs are important greenhouse gases, and prior to the Montreal protocol amendments, were a large component of the year on year increase in radiative forcing. Indeed, the Montreal Protocol has done more to reduce radiative forcing than any other climate mitigation measure – and it isn’t even a climate mitigation measure!

Going the other way, ozone depletion is a chemical process and is affected by temperatures and water vapour in the stratosphere. Ozone recovery in the tropical stratosphere is expected to be faster and the recovery of the polar ozone hole is expected to be slower because of the CO2-induced cooling of the stratosphere (and increase the number of polar stratospheric clouds). Another link is associated with the dynamical impact of the ozone hole around Antarctica increasing the westerly winds dramatically.

There are also links that are perceived in the broader public that are not actually true: CFCs are not aerosols (despite what the New York Times claims), global warming does not exist because of extra heat coming in through the ozone hole, and aerosol sprays do not cause global warming.

In the public debate, many of the climate contrarians (such as Fred Singer) got their start denying that CFCs were affecting ozone, using many of the same arguments they now use about climate change (CFCs are heavier than air! it’s all the sun! the science is uncertain! the scientists are KGB agents! any controls will cause untold misery in the developing world!), and for much the same reasons. But through this all, Sherry Rowland strode tall (literally – he was 6 ft 5 in), and played a large role in debunking some of the wild claims (such as the idea that it was all volcanoes).

Several of us at RealClimate had the honor of getting to know Sherry during the latter years of his career. And those of us who did know him can attest to the fact that he was not only a great scientist, but a great person, who displayed remarkable kindness and generosity. This is perhaps best demonstrated by a personal anecdote. One of us (Mike) got to spend some time with Sherry during a visit to the University of California-Irvine a few years back. The topic of Mike’s lecture was human-caused climate change, and at the end of the talk, one member of the audience – a local who had decided to attend the seminar – made a comment during the Q+A casting doubt on the greenhouse effect, suggesting that CO2, because it was heavier than other air molecules, would simply sink to the ground (a myth that is encountered surprisingly often). Mike pointed out to the questioner the obvious things–that the atmosphere is well-mixed, etc. and so the atmosphere does not stratify according to molecular weights of its constituents, and indicated that he’d be happy to discuss this with him further after the formal part of the lecture. At the reception after the lecture, Sherry could not immediately be found. While everyone else was enjoying a beverage, cookies, and conversation, Sherry had been off in the corner for about 30 minutes talking with the questioner, explaining basic principles of atmospheric science, how the greenhouse effect works, etc. It didn’t matter that one of the two of them had a Nobel Prize while the other may not have had any formal education. What mattered to Sherry is that he had an opportunity to educate someone about this important issue, and that mattered more than anything. It was an inspirational moment–likely one of many inspirational moments experiences by those who were fortunate enough to spend any time around him.

Sherry was deeply involved in advocating for policy restrictions on ozone-depleting substances, and made some very profound comments on the role of science in policy. Most notably, in his acceptance speech for the Nobel prize in a 1986 New Yorker interview he said:

“What’s the use of having developed a science well enough to make predictions if, in the end, all we’re willing to do is stand around and wait for them to come true?”

That is a line that continues to inspire new generations of scientists. He will be missed.

47 Responses to “Sherwood Rowland, CFCs, ozone depletion and the public role of scientists”

  1. 1

    And almost as a respectful followup, the draft report of assembled ozone studies by the EPA, details tremendous damage caused by tropospheric ozone. Ruling expected soon.

  2. 2
    Manning says:

    His name is spelled Rowland.

    [Response: oh my. yes. – gavin]

  3. 3
    William P says:

    Regarding work with CFCs it is important to also mention another truly great scientist, Royal Society member James Lovelock of the UK. From Wikipedia: “After the development of his electron capture detector, in the late 1960s, Lovelock was the first to detect the widespread presence of CFCs in the atmosphere.”

    Lovelock is also a wonderful human being, in addition being a brilliant scientist and inventor. He is the originator of the Gaia law showing earth is a self regulating entity. At least earth did self regulate, before man changed that seemingly miraculous system.

  4. 4
    Dave Werth says:

    There appears to be a typo where you said “he was now only a great scientist”. Replace “now” with “not”?

    [Response:oops. thanks. – gavin]

  5. 5
    Alastair McDonald says:

    Thinking about the myth that the CO2 should sink to bottom of the atmosphere, I did a quick calculation. Assuming that the height of the atmosphere is 30,000 feet then there would be a layer of CO2 12 feet thick at the surface of the Earth which would smother us all!

    Obviously the height of the atmsophere is not 30,000 feet. Does anyone else have a better estimate for the depth of the layer of CO2 would be?

    BTW. Don’t panic! The CO2 would collect mostly over the oceans and anyone living above 3m asl will be safe :-)

    [Response:30,000 ft is probably good enough actually. scale hight of the atomsphere is about 10 km but the difference (very roughly) accounts for density.-eric]

  6. 6
    B Eggen says:

    Wonderful personal anecdote ! The Vega Science Trust has a 3/4hr video recorded back in 2006. Sherwood Rowland talks about ozone and also climate change.

  7. 7
    JamesA says:

    We’ve undoubtedly lost one of the all-time greats of atmospheric chemistry.

    On the topic raised about denial, it is troubling how some people still actively buy into the ozone depletion denialism, in spite of the science standing the test of time and inaction not being an option any more. I’ve seen it used to try to discredit individuals working in climate who previously worked on the ozone issue (e.g. Sue Solomon) or to have a pop at tree hugging scientists in general (along the same lines as DDT denial). Further down the rabbit hole, they even use it as an example of *insert global conspiracy theory here*.

    Point being I think it we owe it to Rowland to make sure that his work isn’t forgotten or allowed to be distorted, even if the problem isn’t as in our face any more. It deserves to be placed on one hell of a pedestal because it is one of the great scientific triumphs of the 20th century.

  8. 8
    Mike Roddy says:

    That’s a great quote from Rowland at the end, and I’m glad that you at Realclimate appreciated it.

    We might be moving into a different phase now. The failures of our media and government appear to be structural, and permanent. Scientists may not be temperamentally inclined to lead us, but, by default, may have to.

    Political activism among our brightest minds has a long history in this country. Before Rowland, we had Jefferson, Lincoln, and Einstein, deep thinkers all. Events drove them to the public sphere.

    Climate change is a far greater threat than King George or even Adolph Hitler. Scientists need to tap their creativity, and work from the heart. Your work on unraveling the mysteries of the atmosphere is ongoing, but the conclusions, and the needed actions, are clear. We need you for this fight, and some of you (Schneider was my inspiration) have awakened us for good. Let’s go forward, shoulder to shoulder, until we win. There is no other alternative.

  9. 9
    Anna Haynes says:

    How do you respond to the objection (which I’ve heard, to past use of the Rowland quote in my .sig) that in climate it’s projections, not predictions, so Rowland’s point is less applicable?

    [Response: Not relevant. All of the predictions for ozone depletion were contingent on scenarios of CFC emissions continuing to increase – which they would have done absent the Montreal protocol and amendments. Thus in IPCC-speak they were actually projections. The same thing is true of the climate issue. – gavin]

    (…besides to point out that “the uncertainty in climate projections associated with the physical climate model is smaller than the uncertainty associated with the models of emission scenarios that are used to project carbon dioxide emissions”)

    [Response: Why is this problematic? It says that we know less about economic development and technology in 2050 than we know about the response of the climate to CO2. I don’t know anyone who would dispute this. But that isn’t to say we know nothing about what CO2 trends will be like in the future – mainly because the inertia in our use of fossil fuels and the carbon cycle itself mean that our ability to strongly affect CO2 concentration pathways before around 2050 is limited. Obviously scenario uncertainty increases after that, but the only vaguely benign scenario that has been produced (RCP2.6) actually requires active removal of CO2 from the atmosphere by 2080 or so and I’m not sure how likely that is. (Actually, I’m pretty sure it’s very unlikely). – gavin]

    Also, a likely typo: “observations ran ahead of predictions”?

    And FYI, email bounces when sent to the Climate 101 “Report Problems” address (forecast-admin)
    (and for anyone else registering, a heads-up: “non-alphanumeric” means “non-alphanumeric”)

  10. 10
    Karen Kohfeld says:

    Thanks for this touching post about Sherwood Roland – I will share it with my students. It’s sad that Rowland’s death coincides with a time when Canada is making drastic cuts to their ozone monitoring program, following a year when the depletion of Arctic ozone is reportedly the largest it has ever been. Indeed, what’s the use of having developed science, if all we’re willing to do is stand around…

  11. 11
    Christopher Hogan says:

    The scariest thing I ever read about CFCs and the ozone layer is here:

    It boils down to this: If bromine had been cheaper than chlorine, DuPont would have used it. The higher efficacy of bromine at ozone destruction, and the long lag time in reaching the stratosphere, means that if bromine had been cheaper, we’d likely have destroyed the ozone layer planet-wide before we’d gotten a handle on restricting halocarbon production. It’s not clear that society would have survived that.

    Not sure if all that is true — the bromine analogs of CFCs are heavier, for example — but it seems plausible.

    There’s no necessary relationship between cost and atomic weight within a column in the periodic table. In that sense, we were just lucky that the chance association of cost and atomic weight led to the use of the less destructive halogen. And so let us survive long enough for scientists to alert us to the danger.

  12. 12
    Unsettled Scientist says:

    My condolences on the loss of a beloved colleague. From beyond the grave he is continuing to educate and inspire, at least me.

  13. 13
    Hank Roberts says:

    > the bromine analogs of CFCs are heavier
    and comparably persistent?

    It’d be an interesting market study — has anyone described the reasons the choice was made at the time?

    “Business response in the United States … indicates that a world with limited use of CFCs will not be catastrophically expensive.”
    Cutting the Cost of Environmental Policy: Lessons from Business Response to CFC Regulation
    Daniel J. Dudek, Alice M. LeBlanc and Kenneth Sewall
    Vol. 19, No. 6/7, CFCs and Stratospheric Ozone (Oct., 1990), pp. 324-328

    Article Stable URL:

  14. 14
    gavin says:

    Rick Piltz has an excellent blog post related to this.

  15. 15
    dbostrom says:

    The item Gavin points out is almost too irritating to read when it comes to the denouement. Singer. Baliunas. CEI. “The road not traveled” and all that. Arrgh.

    Ironically named, that ATI. “Keeping the traditions alive.”

  16. 16
    Thomas says:

    Alastair @5, Even if we had both no bulk air movement (no mixing via fluid flow), and started with all the CO2 as a layer at the surface, it wouldn’t stay there (that isn’t the minimum entropy state of the system). It would instead diffuse via random collisions, until each atmospheric constituent had a scale height inversely proportional to it’s molecular weight. A typical atmospheric scale height is 18,000 feet for halving the pressure (the scale height depends on temperature with varies with height so its gets messier). The scale height of CO2 would thus be 18,000*28/44 = 11500feet. I.E. it would be a bit more concentrated at the ground, but not so much. Of course diffusion is a random walk process, and diffusion across tens of thousands of feet would be an extremely slow process, it takes very little turbulence flow to overcome it.

  17. 17

    There is no time as now. Legacies are built on, Newton said it, on Rowland’s shoulders we see further. I am Canadian, proud from Montreal and the Arctic, being there in the building exactly when the protocol was being negotiated. It was a legendary moment in humanity, when people from all stripes and everywhere were united for Earth. The 1987 protocol was done in a small uncontroversial way, pretty much as insignificant as ozone concentration itself. I must tell again ozone is a trace gas, for those who openly refuse to understand the implications of a trace gas; Ozone has huge importance over climate, even meteorological mechanics not even thought about, to be revealed (one paper awaits). Check out one idea which i tossed out at my blog in progress

    Thank You Sherwood Rowland 12 feet 9 inches high by you.

  18. 18
    Pete Dunkelberg says:

    Supposing CO2 stayed at the bottom of the atmosphere, what would the warming effect be?

    [Response: Zero. The GHE only works if there is a temperature differential between the surface and the atmospheric emitter. – gavin]

  19. 19
    Chris Dudley says:

    Mike Mann will be performing a public duty at noon on the east coast by joining the Kojo Nnamdi Show on WAMU to discuss the efforts of the rouge Virginia Attorney General. The program is streamed

  20. 20
    Jonathan Gilligan says:

    “aerosol sprays do not cause global warming”

    Maybe not the aerosols, but most propellants (CFCs in the olden days; alkanes, N2O, and HFCs for medical aerosols today) have decently large GWPs. On the other hand, they do constitute a pretty small fraction of total GHG emissions, so your statement is correct in the sense that “contribute to global warming” would be more accurate than “cause global warming.”

    [Response: You would be surprised how many people think that not using aerosol cans are the main issue in global warning. The ‘contribution’ you mention is, I agree, non-zero, but frankly it is completely irrelevant in the larger scheme of things, so the correct phrasing might be better as “aerosol spray propellents are only very minor contributors to global warming”. – gavin]

  21. 21

    #18–“The GHE only works if there is a temperature differential between the surface and the atmospheric emitter. – gavin

    “…because if there weren’t, radiational efficacy would not differ much between surface and emitter, either.”

    Correct, more or less?

  22. 22
    Jonathan Gilligan says:

    Gavin: Thanks for the clarification on people thinking aerosol propellants are a significant or even dominant factor. Wow!

    If you happen to have a citation handy to any survey or study reporting the prevalence of this belief, it would be useful because I am collecting instances of mistaken beliefs and their effects on misdirecting people’s actions on GHG mitigation.

  23. 23

    Sherry was a graceful man, a wonderful fellow. He carried himself with the mix of assurance and humility that made him utterly believable. And if you think about it, he really has about as good a claim as anyone who ever lived to having “saved the planet.”

  24. 24
    Martin A says:

    I am not sure if this is the right place to post questions, so please excuse me if I should have posted the following query elsewhere.

    My radiocarbon question: Are there records (publicly accessible via the internet) of atmospheric 14C going up to the present? If not, where could I request such information?

    I am aware of records going up to 1996 but nothing more recent. 1959 – 1983 1976 – 1996

    Many thanks for any help.

  25. 25
    Chris Dudley says:

    Martin (#23)

    There are some measurements up to 2002 here:

  26. 26
  27. 27
    Chris Dudley says:

    Pete (#18),

    Adding a well mixed greenhouse gas increases the altitude of the effective layer which balances absorbed radiation with emitted radiation. Hydrostatic equilibrium requires a lapse rate in the atmosphere which is essentially suspended from a higher altitude leading to surface warming. The lapse rate is the origin of the temperature differential Gavin mentioned.

    If you confine the greenhouse gas to the surface, there is no change in altitude for that layer. The layer and the surface are identical and radiation balance occurs there. If the surface is highly reflective in the infrared, the greenhouse gas could change the albedo owing to its infrared opacity and cause some warming that way, but that is not the greenhouse effect.

  28. 28
    Martin A says:

    Thank you for your help. In, I found data in graphical form but I did not find any machine readable data. I think I should contact ERSL.

  29. 29
    Martin A says:

    OK – I found their ftp downloadable data and I’m poring over it.

  30. 30

    #26–Thanks, Chris, for a helpful expansion.

  31. 31
  32. 32
    Chris Dudley says:

    Martin (#27)

    No problem. There are software packages for turning figures back into data tables, but you can also just use a cursor readout in gimp. Glad you found the ftp site.

  33. 33
    Geoff Wexler says:

    Contribution of CFC’s to GW if the growth rate * had continued.

    Isn’t this a major beneficial and unforseen consequence of Rowland et al’s work? (Ref.1)

    The slowdown in the growth rate of GHG climate forcing from the peak in the 1980s is due mainly to the phase-out of CFC production. If the 10% per year exponential growth of CFC production that existed until the 1970s had continued for several more years, the MPTG climate forcing (mostly from CFC-11 and CFC-12) now would exceed that of CO2 (15).

    Its was low but growing very fast indeed (Ref.2)


    Ref.2 </a

    * I take it that this was not being produced primarily by aerosol propellants(See Gavin's comment following #20) but by heavier industrial activity.

  34. 34
    Geoff Wexler says:

    Contribution of CFC’s to GW if the growth rate * had continued.

    Isn’t this a major beneficial and unforseen consequence of Rowland et al’s work? (Ref.1)

    The slowdown in the growth rate of GHG climate forcing from the peak in the 1980s is due mainly to the phase-out of CFC production. If the 10% per year exponential growth of CFC production that existed until the 1970s had continued for several more years, the MPTG climate forcing (mostly from CFC-11 and CFC-12) now would exceed that of CO2 (15).

    Its was low but growing very fast indeed (Ref.2)


    Ref.2 andr

    * I take it that this was not being produced primarily by aerosol propellants(See Gavin’s comment following #20) but by heavier industrial activity.

  35. 35
    Martin A says:

    Kevin – thank you. I found that Scripps also have downloadable numeric C14 data – looks very promising.

  36. 36
    Hank Roberts says:
    Severe 2011 ozone depletion assessed with 11 years of ozone, NO2, and OClO measurements at 80°N
    Unprecedented low ozone and NO2 columns were observed in 2011
    Low ozone and NO2 columns are attributed to dynamics as well as chemistry
    47% maximum column ozone loss observed, the largest loss in the 11-year record

  37. 37
    Alastair McDonald says:

    Re #5

    Eric, Thanks for your response. I always find it nice to be told I am correct. It happens so seldom.

    I did another calculation based on there being 7e16 moles of CO2 in the atmosphere. If that was all concentrated at the surface of the earth it would occupy 22.4 * 7e16 = 1.5e18 litres

    Divide that by the area of the surface of the Earth which is 5e8 sq km and you get 3e3 litres per sq m.

    So in cm that gives a height of 3,000,000/10,000 = 300 cm or 3m the same as before. But this method can give a more accurate answer should anyone want it :-(

    Cheers, Alastair.

    Cheers, Alastair.

  38. 38
    wili says:

    Hank, thanks for the link on ozone. I would appreciate it if you could call to our attention any new study that examines the behavior of the NH ozone hole (of there is one) this year. I haven’t been able to find anything on it through google scholar (which they just made more difficult to find, I noticed), but your legendary web searching skills far outstrip mine.

    (reCaptcha–dim heGreat)

  39. 39
    Rick Brown says:

    wili @38: It seems to me that Scholar, with its focus on published literature, is unlikely to provide much about what’s happening now. I don’t know whether the following are along the lines of what you’re looking for.

  40. 40
    Hank Roberts says:

    > legendary
    Mythical is a more accurate description. I ask reference librarians for help on ever possible occasion, as reality changes far faster than any individual can keep up.

    Start with an early paper, and work forward following citing papers; here’s one:

    Nature 360, 221 – 225 (19 November 1992); doi:10.1038/360221a0

    Possibility of an Arctic ozone hole in a doubled-CO2 climate

    John Austin*, Neal Butchart† & Keith P. Shine‡
    *Meteorological Office, London Road, Bracknell, RG12 2SZ, UK
    †Hadley Centre for Climate Prediction and Research, London Road, Bracknell, RG12 2SY, UK
    ‡Department of Meteorology, University of Reading, 2 Earley Gate, Reading, RG6 2AU, UK

    Increased atmospheric carbon dioxide concentrations are expected to cause cooling of the lower stratosphere. This could enhance the formation of polar stratospheric clouds, which convert potential ozone-depleting species to their active forms. In an idealized three-dimensional numerical simulation of the Northern Hemisphere winter stratosphere, doubling the CO2 concentration leads to the formation of an Arctic ozone hole comparable to that observed over Antarctica, with nearly 100% local depletion of lower-stratospheric ozone.

    Or look for +arctic, -antarctic, this year:

  41. 41
    Dr. Graham says:

    RIP Dr. Rowland. Climate changes will disrupt the agricultural processes which will cause havoc in the developing world. Areas that grew rice before will not be able to and so on. Fighting over food and water is our future.

  42. 42
    Rick Brown says:

    wili @38: And this, about winter 2010/2011, just made it into print:

  43. 43
  44. 44
    wili says:

    Thanks, hank and rick, for the links. Now I just have to figure out what they mean :-/

  45. 45
    David MacKay says:

    Like #9, I wonder whether “observations ran ahead of predictions” is a typo? If you mean to say “theory made predictions and then the observations came along and confirmed many of these predictions later”?

    [Response: No. Observations of the polar ozone hole were not predicted. The theory (heterogeneous chemistry on PSCs was only developed afterwards. Predictions of ozone loss were initially too small. – gavin]

  46. 46
    Hank Roberts says:

    A good history that brings out the sequence of events as Gavin described:

    The Ozone Layer
    Maureen Christie
    Cambridge U. Press (2001)

  47. 47
    wili says:

    “Observations of the polar ozone hole were not predicted. The theory (heterogeneous chemistry on PSCs) was only developed afterwards. Predictions of ozone loss were initially too small.”

    An important point. I’m guessing that, as things spin ever more wildly out of whack, we will start having a number of ‘observations’ that run well ahead of predictions. We have already seen this with ice melt in the Arctic. Other developments–related to that and not–are also likely to run ahead of predictions, sometimes in dramatic and unpredicted ways (cf. “black swans”).

    Science may learn something from some of these events. Unfortunately, policy makers don’t seem to be as fast studies in learning from experience, however brutal that ‘experience’ is to their constituents. R