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Uncertainty in polar ozone depletion?

Filed under: — group @ 28 September 2007

Guest commentary by Drew Shindell

The unique chemistry that causes dramatic ozone depletion in the polar springtime lower stratosphere has been studied intensely for the past 2-3 decades and much that was speculated about 30 years ago when the problem first emerged has been verified and made more coherent. However, a new report concerning laboratory measurements of a key molecule involved in this chemistry have raised questions about current understanding. The results (Pope et al., J. Phys. Chem., 2007) suggest a reduced ability for sunlight to break apart the chlorine monoxide dimer (Cl2O2) and have already led to a great deal of debate about their implications. I’ll try here to help assess what these new measurements really mean.

The past decades of study have developed a comprehensive understanding of how polar ozone depletion (“Ozone Holes”) takes place. In brief, human-produced halocarbons (chlorofluorocarbons (CFCs) and a few other molecules like methyl bromide) are broken down by sunlight in the stratosphere, releasing chlorine and bromine. These highly reactive atoms mostly go into fairly long-lived molecules that are not very reactive and therefore act as ‘reservoirs’. There are two situations in which a substantial amount of chlorine, the more important of the two, can come out of the reservoirs in large enough amounts to destroy a substantial amount of ozone. One is in the upper stratosphere around 40-50 km altitude, where strong sunlight forms reactive molecules that frees the chlorine. The other is the polar springtime lower stratosphere, where extremely cold temperatures lead to unique chemistry on the surface of ice particles that again transforms chlorine from its reservoirs into more reactive forms.

Atmospheric observations show that in both these situations, there is indeed enhanced reactive chlorine and simultaneous depletion of ozone. Measurements from satellites, aircraft, and ground-based instruments all give independent, consistent information verifying the links between cold temperatures in the polar springtime lower stratosphere and chlorine, and between chlorine and ozone. It’s important to note that none of the laboratory data on the direct chemical reactions that destroy ozone have been questioned. What has now been questioned is not the link between the chlorine released from CFCs and ozone loss, but rather the rate at which the chlorine atoms can destroy ozone via a particular cycle involving the Cl2O2 molecule.

Measurements of this molecule are exceedingly difficult to make in the laboratory as it is highly unstable. Several earlier measurements of the relevant rate have shown variations of a factor of 3 or so, so that the uncertainty in the rate is not new. However, we have substantial auxiliary evidence for what the rates must be i.e. observations of chlorine in the atmosphere provide independent constraints on Cl2O2. Limited direct observations of Cl2O2, as well as many measurements of total chlorine and of chlorine monoxide (ClO), constrain the amount of Cl2O2 (which can’t be greater than the total minus the amount in the ClO molecule). These observations are inconsistent with both the new measurements and earlier reports of a reduced ability of sunlight to break up Cl2O2 (Shindell and de Zafra, GRL, 1995, 1996; Stachnik et al., GRL, 1999; Stimpfle et al., JGR, 2004). Thus although the current state of knowledge is that the laboratory measurements on the stability of the Cl2O2 molecule vary by roughly a factor of 10 (including the newly reported values), the independent measurements suggest strongly that the upper half of that range is more likely to be correct, not the lower.

Given the difficulty in making the laboratory measurements, it is quite possible that these are wrong, and confirmation of the new results is certainly needed. Should the results hold up, the chemistry involved in polar ozone loss may need to be re-evaluated. As there are other cycles that do not involve the Cl2O2 molecule but cause similar dramatic ozone depletion, such as cycles including both ClO and BrO (its bromine-containing analogue), any revision to current understanding would most likely simply shift the relative importance of the various ozone-destroying cycles. However, as noted, it is not clear how one would reconcile these measurements with actual atmospheric observations, which are not consistent with a more stable Cl2O2 molecule.

A wealth of observational data supports the role of chlorine and bromine in polar ozone loss, and uncertainty in a single step of the relevant chemistry does not undermine the Montreal Protocol controlling substances that release these atoms into the stratosphere. It is important, however, that the new results be tested so that we can be confident we understand the potential effects of future changes in temperature on polar ozone loss (as different chemical reactions have different sensitivities to temperature). This will allow us to better understand the effects of climate change on the stratospheric ozone layer, and to verify the effectiveness of the Montreal Protocol, which has already shown signs of success in reducing the growth of atmospheric concentrations of CFCs, and seems to have lead to at least a leveling off of ozone depletion over most of the planet. Full recovery is not expected for a few decades though.

85 Responses to “Uncertainty in polar ozone depletion?”

  1. 51
    Timothy Chase says:

    RE: How do you define “runaway”?

    Personally I think that “runaway global warming” is vague enough it should probably be retired. It is more useful for those who would wish to deny that global warming may be anything other than a minor inconvenience than it is for anyone else.

    To see what part of the problem with it is, take the example of Venus. Our sister planet received only about 15% more radiation than the earth early on in its evolution, but this was enough to result in a positive feedback loop which resulted in the evaporation of its oceans and sublimation of carbon from it minerals, resulting in an atmosphere that is rich in carbon dioxide at a temperature roughly sufficient to melt lead. Now this sort of thing could never happen on earth I am told given our moist air convection. So if this is runaway global warming, then I believe it is fair to say that it couldn’t happen here.

    But is Venus actually an instance of a runaway effect? Certainly not in the sense of process going on without limit. Afterall, it has stabilized.

    Perhaps a more useful way of interpreting “runaway effect” would be that the positive feedback has become sufficient that the process can take place largely independently of what we do. Thus for example, one we raise the temperature of the permafrost or the shallow ocean enough that large quantities of methane are released which increase global warming, resulting in a process which takes on a life of its own, this might be a runaway effect.

    But its not exactly clear that the response will be all that independent of what we do. It may be the case that we could pretty much always make it much worse by doing just a little bit more of a bad thing. (I actually suspect this is pretty much where we are today – with respect to the consequences for the next few centuries.)

    But there is another problem with this: what about earlier instances of what we might call “runaway global warming”? The Permian Triassic Extinction event, for example? We weren’t there, so it was independent of what we did, but then again, so was any other instance of global warming prior to our arriving on the scene.

    It may be the case that the further we push the system the more our “push” will be amplified, or it may be the case that we will reach various tipping points of one form or another, but I am not sure that this is what people have in mind when they think of a “runaway effect.” I believe what they have in mind is Venus – where it does not seem entirely clear that the term can be usefully employed.

    I suppose I would speak of “tipping points” where some are more significant than others. But of course there has been some discussion as to how useful that particular phrase may be.

  2. 52
    Jim Cripwell says:

    I realize that this is OT, but I feel readers of RC might be interested in the rebuttal by Svensmark and Frie-Christensen (?sp) to the recent paper by Lockwood and Frohlich. I am sure this paper has not been peer reviewed, but I hope it will read it for it’s scientific content.

  3. 53
    beyondtool says:

    It’s an interesting topic, because everyone can set the “runaway” bar at different levels. Not to sound negative or anything, but I think we are already past the point where we can expect to continue living life as normal even with zero emissions tomorrow (our lives and our children’s lives are already affected, and we can’t change that). What we can change is the seriousness of this future and the long term impact after we are gone.

    I don’t think we could kill the planet, our species would be extinct long before cockroaches, bacteria or algae were in serious danger. We could upset the biosphere for 100,000s of years, but I believe in time it would recover, at least our fossil record suggests that great extinctions have occurred on the planet before.

    The problem is that we are in the middle of a great extinction event right now, and noone seems to be paying attention. We could all survive on a planet 5 degrees hotter (might be able to get better use of the beach), but the changes to the environment would cause a biosphere collapse, which would result in food shortages, changes to atmospheric gases, widespread fighting over resources etc. Humans love to think we can totally control and manufacture our environment, but at the end of the day our critical needs are sustained by our natural living environment. Back in the nineties we though we could setup a biosphere and mimic the earth’s living systems, but it was a dismal failure.

  4. 54
    Michael says:

    So what is the optimal temperature for the planet? Flora and fauna have adapted to live at our current temperature and change would be bad for current inhabitants, but theoretically speaking, is there a climate ‘sweet spot’ as far as atmosphere chemistry and temperature that would be best suited for life? By coincidence are we living in such a time? Just theoretically speaking. Notice I am not suggesting we have any business tampering with global climate.

  5. 55
    Dan says:

    re: 52. I leave it to others much more qualified than me for the specifics but it seems amusing that the authors conveniently refer to the surface temperature trend since around 1998 as being essentially flat (supposedly in line with the solar muon signal), completely ignoring the fact that 1998 was an exceptional El Nino year which added to the global average temperature that year. Otherwise, that trend is anything but flat. The focus on 1998 is classic data trend cherry-picking, erroneously (purposely?) trumpeted throughout Denialist-land.

  6. 56
    Ray Ladbury says:

    Jim Cripwell,
    The main problem with Svensmark’s ideas is that GCR flux is not changing overall–not during the space era and not during the past 50 years based on neutron fluxes. Presumably the rule that a cause must be extant for an effect to occur is still in force. Moreover, Svensmark’s mechanism has always been rather vague–somehow you get fewer clouds with a lower GCR flux, but there is no evidence that there is any lack of nucleation sites for condensation in the first place. Bottom line, if you look hard enough for correlations, you’ll find them whether they are there or not. That is why it is essential to have a well worked out physical mechanism as well. Anthropogenic ghg is the only such mechanism proposed to date.

  7. 57
    Ray Ladbury says:

    Michael, You are asking the wrong question. The planet doesn’t care. Some organisms would like it warmer, some cooler, some wetter, some drier. The question is what will conditions have to be like for us to support >9 billion humans–and the best answer to that is “predictable”. Adding energy to the climate is bound to make it less predictable, and that cannot bode well for humans on Earth.

  8. 58
    James says:

    Re #54: [So what is the optimal temperature for the planet?]

    I think it could be argued, as James Lovelock does, that the optimal temperature for life as a whole is actually somewhat cooler than today. Cold seas are more productive than warm tropical waters. More water locked up in polar glaciers would lower the sea level, giving more usable land area. Areas like Australia, North Africa, and the part of the western US where I live were much wetter during the last Ice Age…

  9. 59
    David B. Benson says:

    James (58) — During LGM, the last stadial, the Amazon basin was a warm and dry savanna; the tropical rain forest in Africa considerable shrunken in extent. There was a vast desert (some semi-desert) extending from the Sahara right across to Outer Mongolia; huge dust storms in North China and also where I live. The Mammoth Steppe extended from Spain across Europe to Siberia and beyond to Beringa and interior Alaska.

    While I agree that somewhat colder is better, not that much colder, please…

  10. 60
    Andrew Sipocz says:

    We’re already in the middle of a major extinction event caused by the landscape changes associated with hosting 6 billion plus humans on Earth. Even without AGW, we are on track to lose a lot of the Earth’s species. I’ve seen extinction numbers tossed around, but most seem to settle on 30 to 50% of all named species, without AGW’s negative effects. See any of E.O. Wilson’s work for good references on this. I think it will be much worse than most, but hey, my glass broke a long time ago (not even half empty). And many of us won’t be spending more time at the beach as we won’t have beaches to go. Our Texas beaches required centuries (at least) of stable sea levels to accumulate and submerged barrier island/beach systems 20 miles offshore in the Gulf are testaments to past rapid sea level rise episodes. My point is this: when you realistically look at the mechanics of long term species survival (where are they now, what they will be faced with, etc.) or coastline processes; it is easy to see that most AGW projections tossed out by the general press or even mainstream conservation groups are way to rosy. One last example: much of NA’s migratory waterbirds such as whooping cranes, waterfowl, herons, ibis, etc. reside or winter in Gulf of Mexico fringing wetlands. Often these are in National Wildlife Refuges. There are at least 400,000 acres of federal and state refuges on the Texas coast alone. Most of this preserve acreage is less than 1 meter above sea level. The coastal wetlands that host these birds took thousands of years of nearly stable sea levels to form. Draw your own conclusions but I think the consequences of AGW for fish, wildlife and plants etc. are going to be catastrophic.

  11. 61
    Michael says:

    Ray, I was trying to stay away from the AGW vs Denier debate but, I’ll take the bait as usual.

    Adding energy to the climate is a fact of life. No matter what we do we will have a carbon footprint. To think that we could reduce total human impact enough to bring the climate back to something resembling a natural cycle is not realistic. And a natural cycle is still fraut with variability. Saying we need to stop adding energy to the climate is a marginal solution to a significant problem. If we want predictability we are going to have to become masters of our domain, and begin devising massive geoengineering solutions. I think this will eventually happen, and unfortunately will include dead ends and catastrophic failures.

    Regardless, you will not gain support from most people by suggesting a marginal solution to a significant problem. And considering a best case scenario where everyone sacrifices and participates, we will still have warming in our future.

    I know I have said all of this before, but if someone were to seriously take on this issue, it would be the biginning of winning over people like myself.

  12. 62
    Welsh Citizen says:

    Hi to all,
    Just wonding if any of you have come across this;

    The 3 guys from wales, 1 Organic Chemist and 2 Engineers.
    They have found away to capture CO2 and release it to make Oil-Methane Gas-Fertilizer, in short recycling the CO2 we generate into energy.

    Intersting prospect I thought, Radical thinking on a major scale?

    Look forward to any comments.

  13. 63
    David B. Benson says:

    Welsh Citizen (62) — The Greenbox appears to be innovative and, at the least, could be used to capture caron dioxide and nitrous oxides for sequestration deep underground.

    As for feeding to algae, Biopact is not impressed with the results so far and sees little prospect for improvement:

    We may hope they are wrong in their negative assessment.

  14. 64
    Hank Roberts says:

    I’d like to re-ask the question I asked in respl. #2, whenever Dr. Shindell or someone knowledgeable can answer what the experiment was actually trying to do.

  15. 65
    Jim Eager says:

    Re 54 Michael: “So what is the optimal temperature for the planet?”

    That’s a meaningless question. Life has adapted to exist over a rather large range of temperature and climatic conditions throughout Earth’s history, including some that would be lethal to most of life as it exists today.

    The real question is: What is the ideal temperature for life as it exist here and now, including current humans and their civilizations?

    You go on to answer this question yourself:
    “Flora and fauna have adapted to live at our current temperature and change would be bad for current inhabitants.”

    Which includes us and our civilizations.

    “By coincidence are we living in such a time?”

    We are living in the time and conditions that we evolved in, period.

  16. 66
    Ray Ladbury says:

    I don’t believe I said we should go back to the stone age. I merely said that if we add energy to the climate it will become less predictable. Predictability is a really good thing, especially if you are a farmer–or a consumer of farm produce or of water…
    This is not a matter of “going along” or not. This is physics. It is a mathematical certainty that if we keep going down the road we’re on, we will make things very, very difficult for our descendents. You either accept the evidence and resolve to struggle to change the current path or you live in denial and consign your descendents to a world none of us would want to live in.
    So if you have concerns about the effects of mitigation on the economy (and you should, because we won’t succeed without a strong economy to fund research into mitigation), then I would suggest you start working for common sense measures that buy us time and allow smart people time to develop solutions to our predicament.

  17. 67
    Hank Roberts says:

    > Greenbox

    Nah. If they had a way to hold CO2 in such a dense form, the carbonated beverage companies would be all over this just to reduce the cost of shipping big compressed tanks of gas.

    If there were an “intert” form of CO2.

    If something that looks like a furnace filter could hold in such a dense state and release it later, at no great energy cost.

    Could they have Maxwell’s Demons working in their boxes?

  18. 68
    Timothy Chase says:

    Jim Eager (#65) wrote:

    Re 54 Michael: “So what is the optimal temperature for the planet?”

    That’s a meaningless question. Life has adapted to exist over a rather large range of temperature and climatic conditions throughout Earth’s history, including some that would be lethal to most of life as it exists today.

    The real question is: What is the ideal temperature for life as it exist here and now, including current humans and their civilizations?

    The way that I sometimes like to think of it is that just as our civilization hs a great deal investment and infrastructure which is largely grounded in the the assumption that the climate would remain stable, other species and entire ecological systems have done much the same, and when the assumption gives way to climate change a great deal will be lost. (Sorry – I like economic analogies.) Entire cities (from their buildings, to their sewers to their subway systems) were laid down on the assumption that the sea level wouldn’t rise several meters in any given century.

    Domesticated species of plants were breed over centuries with the assumption that there would exist a certain mix of soil, precipitation and temperatures – and we will have a great deal of difficulty adapting these species as conditions change. Fish, coral and the ecological systems in which they participate have evolved with the assumption that the acidity and oxygen levels of the ocean would remain relatively constant.

    But are already changing quite rapidly in the northern latitudes. Places like Australia and California are experiencing longer and more severe droughts. In many parts of the world, some of the richest ecological systems based around coral reefs are already under severe strain. And it is not simply the existence of climate change or its magnitude which we or other life must worry about – but the rate of climate change – which is (as I understand it) over a hundred times faster than anything which we have experienced since the dawn of human civilization.

    PS The above might not be that well thought out – just trying out my new laptop… (I even like the feel of the keyboard!)

  19. 69
    Pete DeSanto says:

    Wayyy OT here, but this is comment >60 so I think I’m not out of line(?). Has anybody seen Stu Ostro’s post at titled “A CONNECTION BETWEEN GLOBAL WARMING AND WEATHER”?

  20. 70
    Michael says:

    The impression I get, is we are living in optimum or slightly warmer than optimum temps. Warming causes more extreme weather, hurricanes, droughts, etc. Slightly cooler would mean more benign weather patterns, while still being warm enough to keep most of the planet green.

    Another impression I get is most environmentalists are more concerned about harming the planet than they are about harming civilization.

  21. 71
    catman306 says:

    “By coincidence are we living in such a time?”
    We are living in the time and conditions that we evolved in, period.
    Comment by Jim Eager

    Except that we’ve cut down so many of the forests that existed while we evolved. The optimum climates for large forests full of trees are the optimum climates for prehistoric man. And now we’ve learned to use fire, and mechanical energy that uses fossil fuels, to add CO2 and other pollutants to the atmosphere. We no longer live in the optimum climates for our species. Severely curtailing the use of fossil fuels, using every available non-fossil fuel alternative (weighing in the complete carbon footprint of the alternative fuel) and the planting of many billions of trees would seem very prudent measures at this time. We all want to see our species and civilization survive another millennium, don’t we?

    On the other hand, someone cut down the last tree on Easter Island, didn’t they?

  22. 72
    Timothy Chase says:


    According to some recent NASA estimates I saw, we are talking about a rise in temperature along the east coast of about 5F without any additional carbon dioxide vs 10F with Business As Usual – by the 2080s. And thats just the east coast. And it is worth keeping in mind the fact that each additional degree is going to be harder on the economy than the preceding degree. In terms of the world economy and various ecological systems, the damage will be roughly an exponential function of the change in temperature. (Something similar is probably true regarding the rate of change.)

    According to the analysis of a former leading economist from the World Bank, the consequences of BAU will be roughly comparable to that of the period from World War I to World War II. I myself strongly suspect that we are talking about a crisis that will be considerably deeper and of greater duration than the Great Depression. The longer we put off changing our trajectory the harder it will be to do so with the growing economies of China, India and other developing nations as become more invested in current technologies.

  23. 73
    Lynn Vincentnathan says:

    I think # 53 makes a good point: “We could all survive on a planet 5 degrees hotter (might be able to get better use of the beach), but the changes to the environment would cause a biosphere collapse, which would result in food shortages, changes to atmospheric gases, widespread fighting over resources etc. Humans love to think we can totally control and manufacture our environment, but at the end of the day our critical needs are sustained by our natural living environment.”

    It’s not so much coping with days and nights that are on the whole 5 degrees hotter (stay hydrated, stay in the shade, get an AC, go to the library), as it is all the impacts, the storms, food loss. And Mark Lynas’s SIX DEGREES pretty much spells out the hell we would be in at 5 degrees. He also writes (if I remember) that if we get to 3C degrees warmer, then that will tip us into “runaway” positive feedbacks that will get us (despite all our efforts to reduce our GHG emissions) up to 4 degrees, which in turn will push us up to 5 degrees, then 6 degrees — over a long time span, to be sure, but it would probably be a done deal.

    It might have been better to have written “we could EACH survive…” since certainly not ALL will survive. That’s the whole point of mitigating GW, so that we all or most can survive.

  24. 74
    john says:

    One question I never see addressed:
    Does depletion of stratospheric ozone,
    leading to increased UV in the troposphere,
    increase ground-level warming? Thank you.

    [Response: No. It leads to a slight cooling. This is included in the classic IPCC forcing diagrams. The increase of tropospheric ozone due to ground-emitted pollution is however a significant warming effect, but that is not related to stratospheric depletion. – gavin]

  25. 75
    Jim Eager says:

    Re 70 Michael: “Jim, The impression I get, is we are living in optimum or slightly warmer than optimum temps.

    We definitely are living during the peak of the current interglacial, but that peak is eventually destined for a long decent into the next glaciation, unless the current warming is sufficient to disrupt the cycle that has held for the past 650,000 years. We know it’s not impossible as there have been long interruptions of the glacial cycles in the past.

    Michael: “Warming causes more extreme weather, hurricanes, droughts, etc. Slightly cooler would mean more benign weather patterns, while still being warm enough to keep most of the planet green.”

    But given enough time, life as a whole and even some individual species would evolve and adapt to those climate states, which would make those states “ideal” for those adapted species. But as Tim said, the current rate of change will outstrip many species’ ability to adapt, quite possibly including our own.

    Michael: “Another impression I get is most environmentalists are more concerned about harming the planet than they are about harming civilization.”

    Some do, I’m sure, but I consider myself an environmentalist and I recognize that there is really not much we can do to harm the planet or even life itself beyond its ability to recover, it’s just that we may not be around to see how great the change is because we most certainly can change the environment and climate system sufficiently to threaten our own survival in that environment, not to mention the survival of civilization as we know it.

    And re 71 catman306, yes, I realize that we ourselves have substantially altered the environment and climate from what it was when we first left the forest for the savanna (I thought that would be understood as a given), but environment and climate have also been altered radically by natural changes over the past 2-3 million years of our evolution. It is civilization that has evolved in the most recent relatively stable period.

  26. 76
    Aaron Lewis says:

    RE 72
    Your optimism in the face of such temperature changes borders on irrational exuberance.

    At such rates of temperature change, agriculture does not have an experience baseline for the prediction of crop rotation and fieldwork schedules. Suddenly, localities have the climate for new crops, but not the infrastructure, to produce and store such crops. Look at the recent bumper crop of wheat in parts of Colorado that ended up sitting in piles in the open because the infrastructure to put it in storage was not in place. While in some traditional wheat growing areas, such infrastructure sat idle as a result of drought.

    The critical difference between GW and the Dustbowl Years was that, in the 1940s, much of that dust bowl went back to being good farmland for the same crops that it produced prior to the Dustbowl Years. Certainly, farming methods had to change to prevent a reoccurrence. Still, the heat of the 1930s was a matter of a few hot years, and then farmers were back to a familiar climate for which they had experience. With GW, we cannot expect that return to normalcy.

    The faster the rate of climate change, the more agricultural crop failures we can expect. The more absolute change in climate, the more likely crop failures will increase exponentially. The more crop failures, the more drag on the economy. Food is going to get expensive, to a degree that will dismay modern economists, shock the public, and force politicians from office.

    Cotton is the crop that consumes more pesticides, fertilizer, and fuel than any other single crop. Also, cotton has specific water requirements. Expect a change in climate to impact cotton production. A surprising amount of synthetic fibers are produced very near sea level, or in areas where critical infrastructure is at or near sea level. In a feedback loop, the fuel, fertilize, and pesticides for cotton farming are commonly made near sea level. Moreover, sea level rise will cause saltwater intrusion into prime cotton growing areas. Thus, expect small changes in sea level to have a disproportionate impact on fiber production. Expect clothing to be far more expensive.

    Walk through a local drug store, and look at how many products on the shelves contain organic chemicals made in a chemical plant that is within a few feet of sea level. Automotive supplies are made in sea level plants. My computer uses parts from such plants. Repair parts used by cell phone service providers come from such plants. Airplanes and their repair parts come from such plants. The two largest airports near me are within a meter of sea level. Finally, a rise in sea level would play havic with a great many cities’ underground utilities. Certainly, all of these facilities can be flood proofed or moved. However, that is a large capital investment that managers and stakeholders are going to delay making until after global warming intrudes into their planning horizon.

    The usual problem with a runaway horse is not how far it goes, but that surprised riders or bystanders are injured in the first mad dash. The problem with global warming is not that it is coming in the distance, but that it is catching us off-guard and unready. I expect sea level change to be episodic, and that the first event will change our paradigm. We still have too much infrastructure and too many manufacturing facilities at sea level. We have too many people living in lowland areas. Our climate and weather prediction systems are too crude to help farmers plan multi-year crop rotation schedules in an era of rapid climate change. The data quality of our sea level predictions is inadequate as a basis of design for engineering.

    In short, we do not have a plan. We do need to stop emitting greenhouse gases. We also need to deal with the ongoing effects of the greenhouse gases we have already emitted. We need to start mitigating impacts on our economy. And, I do mean OUR economy. The developed world could lose everything to GW. So could China, India and the other developing nations. We can only win this game if everybody works together, so that everybody wins. A group of nations can spoil it so that nobody wins, but no nation can win without the everyone’s cooperation. On the other hand, wining will be a relative thing, and any win will involve great effort and much loss.

  27. 77
    James says:

    Re #61: [Adding energy to the climate is a fact of life. No matter what we do we will have a carbon footprint. To think that we could reduce total human impact enough to bring the climate back to something resembling a natural cycle is not realistic.]

    The energy humans directly add to the climate is insignificant. I don’t recall the exact figures (you can probably find them here if you’re better at framing search terms than I am), but IIRC its several orders of magnitude less than the additional solar energy trapped by a relatively small change in CO2.

    It’s certainly possible to envision a world that could sustain present populations & living standards without emitting significant amounts of CO2. It’s even possible to work out the technical ways of getting there without invoking too much hand-waving. The only real problem lies in getting a sufficient number of people to go along.

  28. 78
    john says:

    Thanks for answering, Gavin. What does “the increase of tropospheric UV due to ground-emitted pollution” mean?

    [Response: Sorry, I meant ozone. I corrected the comment. – gavin]

  29. 79
    john says:

    Gavin- Does an increase in tropospheric UV from stratospheric ozone depletion lead to an increase in tropospheric ozone? Thank you.

  30. 80
    JohnLopresti says:

    I appreciate the collected links for working to understand ozone chemistry, and will investigate them. I was reminded of agriculture’s many millions of pounds use of methyl bromide to sterilize soils, and the ban of it but repeated government agency waivers of phaseout. Alternative methods of soil treatment and crop management as well as development of substitute chemicals are difficult vectors to pursue, but the impetus to ban methyl bromide for such uses has been underway for decades in our prominent ag producing state in the US. At the time I last studied the state EIR monograph for methyl bromide, granary fumigation and even structural insecticide use of methyl bromide were prominent though second tier sources for its release into the atmosphere. Our state court mandated an EIR for the use of pesticides of all stripe; the overseer of the development of separate monographs for each of the seven most widely used compounds continues to have an agrichemical toxicity law practice, though now situated in the eastern part of the US; the methyl bromide EIR monograph was about 200p.; his current website references none of his firm’s prior work in that EIR, but is there: In the comments about iodine I was reminded of that halogen’s use in the airplane seeding of clouds to cause rain. With respect to the statements about population control and seeking a way to step outside the inertial box in which we have our civilization, to glimpse at the wide implications of tipping points or “runaway” interactions, I recalled seeing an outsize experiment conducted by a graduate seminar student in a chemistry lecture I attended; the apparatus was much larger than the prepackaged elementary experiments in fun science, resulting in enhanced impact on the observers; what the advanced chemistry student had assembled was a double Ehrlenmeyer flask connecting many liters of ammonia solution in what is known as the ammonia fountain; a consumer grade animation is shown there: with tiny flasks. The concept was the feedback loop drove the reconstitution of the solution as the color tinted solution traveled in waterfall resembling motion between the reservoirs, until equilibrium and binding of the molecules which fueled the reaction. Rocket motors operate on similar principles, except the burn is a one-time event only. The ammonia fountain demo was a bit risky, it seemed, as the gifted chemist who assembled the components, like the students in attendance simply had to watch while the process, once launched, traveled to endstate.

  31. 81
    Paul Dietz says:

    and Robert Parson cited Paul Dietz

    Cited me as an example of someone who was convinced by the evidence in spite of possibly contrary political preconceptions. I feel good about that, but, really, reading the relevant papers in the atmospheric physics/geophysics literature made it difficult to come to any other conclusion.

    It was good training, though, and I now recognize the same general kind of cognitive errors in the denialists this time around. With ozone and CFCs, the denialism eventually migrated out to the manifestly lunatic fringe and left serious public debate. I suspect the same process is at work with fossil fuels, but the economic interests are much larger so it will take more time.

  32. 82
    Greg Weisbrod says:

    As a lazy layman, not a scientist, not having researched the above links,
    all I can do is share my ignorance and mistrust of modern atmospheric
    science. The cutting edge of science seemed to abound abound with
    reversals and flip-flops, as I remember from the articles in My Weekly
    Reader. This I now see is part of the process of science, peer review.
    Atmospheric science has come a long way since Carl Sagan. It has come even
    further since investigators pointed spectrometers at the sky and found
    sodium lines. This unexpainable discovery was promptly dismissed as error.
    In fact, ocean sloshed salt became airborn and ionized. How is the
    associated chlorine dismissed by today’s science? They claim it recombines
    before it passes the tropospheric barrier. I would want a better explaination
    of why oceanic chlorine is less depleting than man made CFC’s. Perhaps the
    sugested diminished Cl2O2 pathway and its resulting stability amounts
    to sucking the oxygen out of the air. Plus, what does OD have to do with
    global warming? I guess I’ll have to go see that Al Gore movie.

  33. 83

    Greg Wiesbrod posts:

    [[ I would want a better explaination
    of why oceanic chlorine is less depleting than man made CFC’s.

    Because oceanic chlorine is water-soluble, and rains out before it reaches the stratosphere, while chlorine in CFCs is water-insoluble and survives to be lofted into the stratosphere by atmospheric turbulence.

  34. 84
    Paul Dietz says:

    In fact, ocean sloshed salt became airborn and ionized

    The conventional scientific theory is that the atomic sodium in the upper atmosphere (high above the stratosphere) comes from micrometeorites, not a terrestrial source (and the sodium atoms are neutral, not ionized, otherwise they wouldn’t show those strong yellow lines.) The contrary view was being pushed by the pseudoscientists back before they lost the CFC war.

    The source of chlorine in the stratosphere is know to be mostly from CFCs and related compounds, btw, since we’ve detected the other breakdown products of there (HF, COF2, etc.) in consistent amounts. These fluorine species have no significant natural sources.

  35. 85
    Hank Roberts says:

    > and Robert Parson cited Paul Dietz

    Yep. I appreciate that you’ve been thinking hard for a long time in public about science. Thank you.