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    Ozone: A 2011 Update And A History Of Screwy Computer Models
    By Enrico Uva | December 28th 2011 04:56 PM | 30 comments | Print | E-mail | Track Comments
    About Enrico

    I majored in chemistry, worked briefly in the food industry and at Fisheries and Oceans. I then obtained a degree in education. Since then I have...

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    Assuming countries continue to comply with the 1989 (enforced) Montreal Protocol, the ozone layer is expected to recover in coming decades due to declining chlorofluorocarbon (CFCs)concentrations. Total recovery, however, is not predicted before 2050 or 2060.  Although in the past year (from 2010 to 2011) the hole has increased in size by five million kilometers, for most of the last two decades, the hole seems to have stabilized, oscillating between 20 and 25 million square kilometers---about three times the size of continental United States.

    But I'd like to focus most of this essay on some of the subtleties surrounding the chemistry and history of the hole. Before delving into details, I have to point out that it's still astonishing how many people with slight science-allergies still confuse the ozone hole with global warming. The only thing they have in common is that the freons that eventually release the atomic chlorine that catalyzes ozone destruction also happen to be minor greenhouse gases. But in the public imagination, it is incorrectly imagined that the extra ultraviolet that comes through the hole is what supposedly warms up the planet!

    1. What is the hole, really?

    Nowhere over Antarctica is there a complete absence of ozone(O3) in the upper stratospheric layer. Prior to 1979, concentrations of always exceeded 220 Dobson units(DU). The hole" is the area where the concentration dips below that threshold; the lowest seasonal minimum ever recorded was 92.3 DU in 1994.


    2. What technological device played a pivotal role in linking freons to ozone depletion?

    In 1957, James Lovelock of Gaia-fame invented the electron capture detector, which when mounted on a gas chromatograph, is capable of measuring extremely low concentrations of atmospheric gases in parts per trillion. By comparing the emissions of freons(CFC's)to those actually present in the atmosphere, it became clear that they were not being broken down. But interestingly, as Lovelock started to turn from inventor to theorist, he erroneously predicted in 1970 that the presence of CFCs in the air was completely innocuous.

    3. Why did it take so long to discover the hole, and how did computer models screw things up?

    The depletion should have become apparent before 1985 since measurements revealed that minimum concentrations kept dipping almost consistently from a 225 DU low in 1979 to as low as 163.6 DU in 1984. But in the same way that scientists had incorrectly assumed that CFCs were harmless, they assumed that the data was too low to be real, and they placed faith in computer models that predicted ozone to remain intact.

    4. Why is ozone depletion most pronounced over Antarctica?

    After CFC's release atomic chlorine it attacks O3 and generates O2 and a compound of chlorine and oxygen (ClO). ClO in turn attacks atomic oxygen which is needed to recycle ozone. This forms molecular oxygen and regenerates atomic chlorine, which is then free to attack more ozone.

    Fortunately for the rest of the planet, ClO reacts with another pollutant, nitrogen dioxide to generate ClONO2 . But a drain-like atmospheric effect called the polar vortex forms over Antarctica during their winter. This serves to remove nitrogen dioxide from the stratosphere above the southern pole. In addition, polar stratospheric clouds convert ClONO2 and HCl into nitric acid and atomic chlorine.

    5. What ozone depleting chemical was not included in the Montreal Protocol?

    Nitrous oxide (N2O) was not included. This byproduct of agricultural fertilizer forms NO (nitrogen monoxide) which like atomic chlorine also catalyzes the destruction of ozone gas. Ultraviolet light also dissociates a small percentage of water into hydroxyl radicals(OH.) which can also attack O3. Early computer models were not programmed with these effects and using only the so-called Chapman reactions based on the recycling abilities of diatomic and monoatomic oxygen, they predicted an excess of 30% of ozone. Interestingly many freshman college books also incorrectly ignore the pivotal role of hydroxyl radicals in forming acid rain, attributing it instead to simpler reactions that only occur with high concentrations of oxygen. (If you burn sulfur over a Bunsen burner and test the fumes with wet pH paper, sulfuric acid will not form*. Only when you place burning sulfur in an oxygen- filled flask is there an immediate reaction.)

    6. Why were people skeptical after Rowland and Molina linked CFCs to ozone depletion?

    Some surmised that
    hydrochloric acid (HCl) from volcanic emissions and subsequent formation of Cl played a more important role than freons. But the skeptics were proved wrong when studies of the El Chicon and Pinatubo eruptions of 1982 and 1991, respectively, revealed that the HCl emitted  never made it out of the troposphere, in the same way that HCl from swimming pool chlorine poses no threat to ozone.

    * As a reader(D.Potter) pointed out, a weaker acid (bisulfite ion) will form instead.

    SOURCES:


    Wikipedia http://en.wikipedia.org/wiki/Ozone_depletion
    NASA: http://ozonewatch.gsfc.nasa.gov/meteorology/annual_data.html
    A transcript kindly sent to me by Jim Kasting of Pennsylvania State University

    Comments

    rholley
    What does happen if you burn sulfur over a Bunsen burner?
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    UvaE
    You do get sulfur dioxide, judging from the smell, but there's no evidence of much sulfuric acid forming immediately.  See Derek Potter's and my comment below for more details.
    Bonny Bonobo alias Brat
    Great article Enrico. Now can you please write one called 'Global Warming: A 2011 Update And A History Of Screwy Computer Models' please?
    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    UvaE
    The global warming computer programmers sure could have learned from the mistakes of ozone modelling! So many factors come into play with all forms of atmospheric pollution including photochemical smog, acidic precipitation, global warming and ozone depletion, and probably more factors await discovery.

    But in all cases there's no denying that human mass production of specific chemicals initiated each problem. The predictions though are shots in the dark; and the one I mentioned about the total ozone recovery could easily be off by several decades.
    Scientists need to stop predicting altogether, and start doing a better job of EXPLAINING. Your models rely on highly variable inputs, and thus can never have any robust predictive value.

    When you achieve a model that, year after year, inputs current values of these variables and outputs the correct measured size of the ozone hole, only then will you have the right to claim "there's no denying that human mass production of specific chemicals initiated each problem.". Until then, this arrogant statement disserves science and fosters more, not less, public skepticism.

    Ditto for global warming models.

    UvaE
    only then will you have the right to claim "there's no denying that human mass production of specific chemicals initiated each problem.". Until then, this arrogant statement disserves science and fosters more, not less, public skepticism.

    So what did initiate each problem?! Because explanations and models aren't perfect is no reason to go into complete denial.

    Also even though we initiated environmental problems, it doesn't mean we can't solve them, nor is it a symptom of political malaise. Acknowledging environmental problems makes people feel uncomfortable and guilty. But it's an irrational response. And by the way, hypothesizing with rational basis and looking for evidence is not a disservice to science.

    So what did initiate each problem?

    Whoa! Back up! By claiming "there's no denying...", you've made a statement of fact. The burden of proof is on you. You cannot defend your claim by pointing out that I don't know either. You are saying that YOU KNOW. I am saying that YOU DON'T KNOW, or at least haven't demonstrated your knowledge sufficiently. A good model, as I described above, hardly needs to be "perfect" to persuade me.

    And of course we've initiated, and solved, environmental problems. The air and water in the developed world is radically cleaner than 40 years ago. Good science and honest politics did that, and it's wonderful. Nothing uncomfortable about that.

    UvaE
    You are saying that YOU KNOW. I am saying that YOU DON'T KNOW, or at least haven't demonstrated your knowledge sufficiently.
    I know what you're saying even without the block letters. But you're confusing knowing the cause with attempting to evaluate the severity and with trying to predict outcome. It's the latter two that have blemished climate science and which have given ammunition to cranks and to people with hidden agendas.
    And, in fairness, some climate scientists also had their own agendas.
    It seems we've reached the point of agreeing to disagree. I hold as self-evident that one can't purport to know the cause(s) of phenomena until one can adequately explain outcomes and severity.

    Apologies for the gratuitous stridency. Peace.

    MikeCrow
    knowing the cause
    Knowing is actually a strong term, which in this case doesn't appear to be true.
    If it was true, wouldn't you expect that the amount of cooling on a daily/annual basis drop as co2 goes up?
    Because it doesn't.
    Never is a long time.
    Now explain how Freon 12, di-chloro-di-flouro-methane, makes it up into the stratosphere, when it is well known to people who have worked with it that it it is so much denser than normal atmospheric gases that it falls to the ground. In case of a an R-12 leak in a confined area, instructions are to walk out with your head held high. In case of accidental breathing in, hold the victim upside down to drain the R-12 out...

    Also, when people tell me that refrigerants cause all this chlorine to enter the arctic and Antarctic atmosphere to aid in ozone destruction, I ask a simple question that none have answered. Di-chloro-di-flouro-methane. All the banned refrigerants have flourine as part of the compound. Where's the flourine? Did it take a wrong turn on the way up and get lost? It apparently disappeared, because it certainly isn't measured. If refrigerants, the most popular of which was R-12, were responsible for the ozone hole, the flourine would be there also.

    Now explain how Freon 12, di-chloro-di-flouro-methane, makes it up into the stratosphere, when it is well known to people who have worked with it that it it is so much denser than normal atmospheric gases that it falls to the ground.

    The pure gas/vapour is dense and will form layers but it soon dilutes with air and then there is no way it will unmix.

    Gravity is not enough to pull molecules out of a mixture in any meaningful sense. The mean thermal energy in the vertical direction divided by the gravitational potential gradient is about 2 km which means that a column 2 km high would eventually settle with 2.7 times higher concentration at the bottom than the top. However this would take about 40,000 years. Any breeze exceeding a metre in 20 years would simply stir it all up again.

    In case of accidental breathing in, hold the victim upside down to drain the R-12 out...
    Har-har-har.   I do hope you are joking.
     

    rholley
    Nicely explained.  The same, of course, with miscible liquids.  At school we were shown a demonstration of three layers, at the bottom a solution of some kind of salt in water, then a layer of water, and at the top alcohol.  At the start, they just sat there.
     
    Over time, the alcohol would mix down into the salt solution below, and because the process was so gentle, bi-i-i-g crystals of the salt would form.  Whether the mixing was mainly by diffusion or tiny convection currents, I don’t know.

    But once they’re mixed, the Boltzmann distribution comes in, which I see you have calculated to get that concentration figure.  But please do not ruffle any feathers while the experiment is in progress.

    This paper is very good on how it took so many years to work all this stuff out:

    Gadflies and Geniuses in the History of Gas Theory
    Stephen G. Brush
    Synthese Vol 119 Issue 1-2 pp 11-43 (1999)


     * * * * * * * * * * * *

    However, I think Gospace is right about the refrigerants and pouring them out of the person’s lungs.  If done gently enough, that should avoid significant diffusive mixing.  In our microscopy centre, the big transmission electron microscope uses sulfur hexafluoride, and in case of leakage the layout is designed so that it will flow down and escape across the floor and through some kind of air brick.
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    However, I think Gospace is right about the refrigerants and pouring them out of the person’s lungs. If done gently enough, that should avoid significant diffusive mixing.
    Well, using reasonable figures :) if you could empty a couple of litres from a victim in 15 seconds you might manage to achieve counter-flow in the trachea  without the onset of turbulence at a Reynolds number of ~3000  but any rough handling and you'd lose it.  And I'm not sure whether laminar flow is sufficient anyway, I mean you can stir honey and cream together with purely viscous mixing. There's all the complication around the larynx for a start - that's got to be equivalent to a stirring spoon or two. I can't see how you could possibly hope to maintain the counter flow. 

    But what's the point? With anything like normal breathing flow rates the Reynolds number is going to be in the high thousands, ensuring very rapid, turbulent mixing. The best strategy is surely successive dilutions - just a couple of AR cycles and most of the gas would be removed far more reliably than trying to empty the victim like a teapot.

    rholley
    Regarding fluorine and the ozone layer, I have just found this:

    USES OF HALOGENOALKANES

    From which I extract this:

    Hydrofluorocarbons, HFCs

    These are compounds containing only hydrogen and fluorine attached to carbon. For example:

    HFC-134aCH2F-CF3

    Because these HCFCs don't contain any chlorine, they have zero effect on the ozone layer. HFC-134a is now widely used in refrigerants, for blowing foamed plastics and as a propellant in aerosols.

    I don’t know how accurate this is, but it does attempt to answer the question about fluorine.

    Robert H. Olley / Quondam Physics Department / University of Reading / England
    UvaE
    The F remains bonded to CFC's carbon(s). It's because the C-F bond energy is 448 kJ/mole, as opposed to C-Cl's 330 kJ/mole.

    The most important reaction of the CFCs is the photo-induced scission of a C-Cl bond:

    CCl3F → CCl2F. + Cl.
    That doesn't answer where the flourine is. If the entire R-12 molecule makes it into the stratosphere, and is the source of chlorine destroying the ozone layer, then the flourine should also be there in the same measurable quantities. 2 flourines, 2 chlorines. The flourine isn't there. Where is it?

    In fact, with the increasing use of halogenated flourocarbons w/o the chlorine, there should be an increasing amount of flourine up there.

    rholley
    Because fluorine is not discussed in the main article, that does not automatically mean that people do not measure it.  However:
    The [Montreal] treaty[4] is structured around several groups of halogenated hydrocarbons that have been shown to play a role in ozone depletion. All of these ozone depleting substances contain either chlorine or bromine (substances containing only fluorine do not harm the ozone layer). For a table of ozone-depleting substances see: [2]
    http://en.wikipedia.org/wiki/Montreal_Protocol

    Robert H. Olley / Quondam Physics Department / University of Reading / England
    You will find all the answers if you read this 1992 paper: J. Atmospheric Chemistry Volume 15, Number 2, 171-186. "The 1985 chlorine and fluorine inventories in the stratosphere based on ATMOS observations at 30° north latitude" by R. Zander, M. R. Gunson, C. B. Farmer, C. P. Rinsland, F. W. Irion and E. Mahieu.

    All the CFCs and non-CFCs and all of their breakdown products, chlorine and fluorine, were observed, measured and accounted for.

    If you burn sulfur over a Bunsen burner and test the fumes with wet pH paper, acid will not form. Only when you place burning sulfur in an oxygen- filled flask is there an immediate reaction.
    Are you sure? Last time I burned some sulphur it stank the place out. Very pretty blue sparkles if you flick flowers of sulphur into a flame and a rather insipid blue flame if you just burn sulphur on its own. I was only about 9 mind you, but I invented a firework called The Blue Choker. I suspect it was much the same as those old sulphur candles they used for sterilising. Surely no hydroxyl is needed for SO2 to react with water and create sulphurous acid to turn pH paper?
     


    UvaE
    It stinks up the place because of sulfur dioxide, but that won't immediately form sulfuric acid, unless it gets further oxidized in a more oxygen-rich environment. While I tried it several times, I thought the water was just evaporating from the indicator paper, but when I re-wet the paper on the spot, I obtained the same negative result.

    But when I repeated the experiment with increasing levels of oxygen, the amount of acidity was proportional to how much oxygen I delivered into the flask, presumably because an increasing amount of sulfur trioxide was being generated.
    I didn't say sulphuric I said sulphurous.

    My school (and photographic) chemistry agree with Wikipedia:
    There is no evidence that sulfurous acid exists in solution... The conjugate bases of this elusive acid are, however, common anions, bisulfite (or hydrogensulfite) and sulfite.

    Raman spectra of solutions of sulfur dioxide in water show only signals due to the SO2 molecule and the bisulfite ion, HSO3−. The intensities of the signals are consistent with the following equilibrium:
    SO2 + H2O <-> HSO3− + H+
    Ka = 1.54×10−2; pKa = 1.81
    I hate to suggest this but do you think the paper over the bunsen was being bleached?
    UvaE
    Thanks for enlightening me, Potter, and sorry for the sloppy reading of your comment.

    I should have thought of the equilibrium you quoted--it's the same one involved in treating white wine. Maybe the paper did get bleached above the burner flame, and if concentrations of sulfur dioxide increased with the higher concentrations of oxygen I tried, then the equilibrium
    SO2 + H2O <-> HSO3 + H+ shifted to the right, creating higher concentrations of H+.

    But  in the atmosphere I wonder how much of a role bisulfite formation actually plays.

    The reference, by the way, for the hydroxyl role is Wikipedia, which in turn[5] is from(
    Seinfeld, John H.; Pandis, Spyros N (1998). Atmospheric Chemistry and Physics — From Air Pollution to Climate Change. John Wiley and Sons, Inc. ISBN 978-0-471-17816-3 )

    In the gas phase sulfur dioxide is oxidized by reaction with the hydroxyl radical via an intermolecular reaction:

    SO2 + OH· → HOSO2·

    which is followed by:

    HOSO2· + O2 → HO2· + SO3

    In the presence of water, sulfur trioxide (SO3) is converted rapidly to sulfuric acid:

    SO3(g) + H2O(l) → H2SO4(l)
     "Derek" please :)

    I think maybe I'm a tad *too* familiar with that particular oxide! Not only did I create a "fountain" by pouring nitric acid on sodium sulphite - those poor molecules must have got very confused with an acid-base reaction as well as redox at the same time - AND large quantities of sulphur consumed in pyrotechnics AND more yet released by careless disposal of photographic chemicals... These were usually mixed with my failed attempts at making batteries for my radio controlled model plane which I didn't finish because I spent years messing about designing the radio system from scratch (it had to be the lightest in the world and the world kept changing) and the battery had to be silver-zinc which involved a lot of nitric acid and scrap silver (or rather scrapped silver: I suspect my mother was quite fond of that little silver box) and electrolysis, and the radio involved home etching of circuit boards with ferric chloride reinforced with chlorine generated in-situ from bleach and HCl to make it go faster, plus designing the best oscilloscope in the world (well it would have been the best forty five years earlier) in order to see why the radio wasn't working..... where was I? Oh yes, with all that going on and everything's success dependent on everything else, basically nothing came out of it all except a whole load of nasty chemical waste mostly with a pH << 0 and a pile of sulphites of one kind or another. Hence clouds of SO2 became something of a norm around the Potter household. But the project of them all was my decision to make a refrigerator. Why would I want to make something I could have retrieved off a rubbish tip? I have no idea. But I wanted to make a refrigerated cupboard big enough to store "exhibition-size" colour photographic paper, which in those days meant 20 by 16 inches. I decided to make an absorbtion refrigerator using silica gel, bought as a dessicant, plus I reckoned about 200 gm of liquid SO2. Oh yes, very practical. So I made my gas generator out of copper (couldn't afford glassware) which was quite simple as I'd already made a water still. You see, I needed gallons of deionised water for my tropical fish farm ... yes, the fish died. Condensing the SO2 took many kilos of ice and salt and resulted in a toxic swamp in the kitchen. Eventually, after consuming most of my stock of photographic sodium sulphite and a Winchester of conc HCl, I had a 250ml bottle of liquid SO2. And a swathe of death in the garden which I never quite explained to my father who was a keen gardener. The summer came and I decided to check the vapour pressure from my ancient handbook of something or other and realised it was only by a miracle (or more likely some water in the SO2) that the bottle hadn't burst, so I gingerly immersed it in the rain water butt and released the lid, gently. As reactions go it was quite tame for a change, but the mosquito larvae all died - which was a Good Thing. I had to 'fess up to my long-suffering father that it probably wouldn't be a very good idea to water the garden with what was rapidly turning into dilute sulphuric acid. It would probably have been ok, but I was beginning to learn and I couldn't face the thought of all his competition-winning Irises going black and keeling over in another mystery plague. He was quite sangine about it - it was, after all, he who had given me that little book of chemistry in the first place. And he loved the fireworks even when the neighbours complained :)

    Hmm, I don't think atmospheric chemistry had been invented when I was a kid. Those highly oxidizing species seem to be happy to form some really wierd stuff. Who ever heard of HO2, for Pete's sake? I wouldn't even know what to call it... But Goopedia does: "Hydroperoxyl". Another world has just opened up for me :/
    Bonny Bonobo alias Brat
    Ha ha, very funny. I also had a few chemical experiments that went wrong when I was a child but the best one by far was a school experiment to create Nitrous Oxide (N2O) or laughing gas, when the small 'school for young ladies' naturally did not have any gas chambers to cope with an out of control experiment. We had to form a human chain and pass dozens of glass containers of laughing gas out to the last girl who was standing in the orchard and then emptied the gas there. In the end we were all laughing hysterically, even the chemistry teacher! 

    So when are you going to write that explanation you promised about 'the complete (ahem) solution to the Grandfather Paradox'? Sorry if I'm nagging.

    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    It's already been written in a few weeks time, it just hasn't arrived here from the future yet. :)
     
    Too many interesting ideas being kicked around on this site...
    UvaE
    That's quite a set of recollections, Derek! You were lucky to have a dad who gave you a chemistry book and who enjoyed your pyrotechnics.
    UvaE

    Now that the holidays are over and I got a chance to get back into the lab....

    After running several blanks (placing wet indicator paper above a bunsen flame) and subsequently testing it with 0.1 M HCl, it was obvious that the indicator still works. So bleaching was not the issue. Even with the strong possibility of bisulfite ion forming, the concentration was simply too low to change the paper.

     
    Can Geoengineering solve the problem of ozone layer depletion?

    UvaE
    Can Geoengineering solve the problem of ozone layer depletion?
    I once saw a plan to release large amounts of ethane(which can react with chlorine) in the stratosphere. But it sounds expensive and who knows of the unforeseen consequences. The alternatives to CFCs made more sense, and the Mtl Protocol can be further improved by addressing nitrous oxide, which is also a greenhouse gas.