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Rolling up the circus tent: Dispatch #7

Filed under: — raypierre @ 15 December 2007

There’s always a feeling of tristesse when they start pulling down the circus tents and loading the last of the elephants into their trailers. The last day of AGU feels a bit like that. AGU puts one much in mind of those medieval faires, or the Jokkmokk Vintermarknad, where people gathered (and still gather, in the latter case) from time to time to exchange goods and the latest news. Our own faire is a marketplace of ideas, though you can buy some nifty stuff here,too. Like a medieval faire, this is a social event as well — a time of feasting and revels, of renewing old friendships, and of making new ones. Happily, any brawls we have here are rather genteel ones.

But, it’s not over ’til it’s over especially in view of the fact that I was chairing (and giving the last talk at) the very last session of the whole shooting match — on evolution of extrasolar Large Earths. A dedicated group of extrasolar types stayed around for the fun. Closer to home, though, I dropped in on the session on Pliocene climate and the session on geoengineering.

The Pliocene was the latest warm time in the Northern Hemisphere before the great glaciations of the Pleistocene closed in. To some extent, as we increase the atmosphere’s CO2 content, we are traveling backward in time so far as climate is concerned. Hence the Pliocene, which ended about two million years ago, has attracted a lot of attention as an analog climate for what may lie ahead. It’s not a perfect analogy, but the challenge of understanding Pliocene climate provides another test of the operation of model physics in a warm climate. Another interesting feature of the Pliocene is that some paleoceanographic data indicates that the tropics were subject to a permanent El Nino configuration, with much more zonally symmetric Pacific temperatures.

Mark Chandler presented a talk raising the concern that explaining the warm Pliocene climate seems to require an assumption of high climate sensitivity (well above the IPCC mid-range). M. A. Medina-Elizalde discussed some new high-resolution data on the temperature of the late Pliocene tropical Pacific. This included alkenone proxy data as well as Mg/Ca. Something that particularly struck me about this data is that the Late Pliocene shows a pronounced 100,000 year cycle in tropical Pacific sea surface temperature. Since the Northern Hemisphere ice sheets had not yet formed at this time, they could not be playing a role in amplifying the effect of the eccentricity cycle. Being purely speculative, I’d suspect we’re seeing some kind of CO2 modulation connected with things going on in the Southern Ocean, or perhaps connected with partial land ice cover in coastal Antarctica. Anarctica was already glaciated at this time. There was also a modelling talk by M. Vizcaino, evaluating several factors proposed to have accounted for Pliocene warmth. The ones that seem to contribute the most to conditions unfavorable for Northern Hemisphere glaciation are elevated CO2, the orbital configuration, and a permanent El Nino.

I skipped the geoengineering talks that rehashed material already covered at the Harvard geoengineering workshop, but there were some new things. The authors of the talks I went to were all quite cautious and were careful to point out the many possible hazards of geoengineering. There was very little new attention, however, to the biggest issue, which is what happens to the planet if you have to suddenly stop the sulfate injection, and then hit the planet with 200 years worth of greenhouse forcing all in two decades. There was plenty to be concerned about, though. In my previous geoengineering post, I pointed out concern that a geoengineered world would have lower precipitation than the normal world, even if you got the temperature right. Kevin Trenberth presented additional support for this, based on analysis of response to volcanic eruptions. There was some concern expressed that these transient results were not representative of the equilibrated response. However, Alan Robock, in a paper subtitled Cooling but Drought, presented simulations that confirmed a sharp precipitation drop in a geoengineered world, and G. Bala re-examined his earlier simulations done with Ken Caldeira to confirm that the effect was there, but overlooked in their analysis.

Of particular interest to me were two papers presenting the first geoengineering simulations carried out with fully coupled dynamic ocean-atmosphere models. This is especially interesting in view of the importance of sea ice response in evening out the difference between the tropics-heavy solar radiation reduction vs. the more uniform CO2 radiative forcing. At the Harvard geoengineering workshop, David Battisti stated that mixed layer ocean simulations of geoengineering were of dubious utility, because they lack the most important processes governing sea ice formation and retreat. The two fully coupled simulations were presented by D.J. Lunt and co-workers, and C.M. Amman and co-workers. Sure enough, these simulations show that geoengineering is much less effective at restoring the natural temperature pattern than was suggested to be the case in the earlier simulations. In particular, if one tunes the global mean to have the right value, one fails to save the Arctic perennial sea ice. This is not a way to save the polar bears, as it has been sold, nor is it a reliable way to save Greenland. Another concern comes from atmospheric chemistry. In a talk substituting for a cancellation, the NCAR group showed that stratospheric warming in a geoengineered world increased ozone destruction — by a factor of 2-3 in the Arctic — even if one took into account the downward trend in stratospheric chlorine coming from the gradual reduction in CFC content of the atmosphere.

I continue to think that geoengineering is a big and unfortunate distraction, but since the cat is out of the bag, it is good that some people are doing the work to head off rosy and over-optimistic projections of sulfate geoengineering as a magic bullet that could substitute for the hard but necessary work of mitigation of CO2 emissions.

What was really most exciting to me in today’s sessions (and last night’s Sagan lecture, presented by Ralph Lorenz) was all the great thinking about solar system and extrasolar planetary climate. The missions in the planning stage for Solar System exploration are really something to look forward to. Now that people think Europa has a thick ice crust (maybe 20km or more) there’s less talk of drilling through with mini-subs, but there’s an orbiter planned, and possibly a lander with a seismometer,which would settle a lot of questions about the nature of Europa’s ice crust. And Ralph Lorenz’s work on hot-air balloon missions to Titan is really cool (about 110K, to be precise).

That wraps it up for this year. I’m sitting in the airport waiting for the red-eye to Chicago. The spontaneously organized session on extrasolar planetary evolution was so productive I’m thinking of organizing a Union session on the subject for next year.

With best wishes to all for Happy Holidays!

96 Responses to “Rolling up the circus tent: Dispatch #7”

  1. 1

    Dear Raypierre,

    There seem to be other, more benign geo-engineering proposals around, more worthy of discussion and modelling than the sulphate into the stratosphere one.

    Prsonally I think there is a bit of mileage in adding extra cloud condensation nuclei (from sea water) into the marine boundary layer to increase low level cloud cover.

    I would be interested in contact details of the people that you mentioned who have done some modelling, in case they could do some more, on other ideas.

    I could supply papers on this, or a summary for your Realclimate site, if you are interested.

    Best Wishes, Colin Forrest

    If you don’t know

  2. 2

    Great summary! Unfortunately I have never been at an AGU meeting in spite of being a member.

    Has anybody really doubted that sulfate aerosol geoengineering is anything but a last-ditch attempt at saving our sorry asses after, conform human nature, doing too little too late? It does’t even undo the effects of climate change, just cancels numerically its most conspicuous manifestation. Almost everything else remains unfixed.

    One question though: how would preferential injection at high latitudes help? The stuff stays in circulation for some years. Would it spread much in latitude over that time?

  3. 3
    Nick O. says:

    It is a relief to see some of the possible disadvantages of
    geo-engineering being discussed, and especially some of the effects
    of ‘G-enge’ options on atmospheric chemistry. I’m not sure myself
    it’s a genie we want to let out of the bottle; after all, how do we
    judge the setting of the Earth’s thermostat in the first place? And then
    how do we decide what setting it should be (a trickier issue than it seems –
    just consider ‘Who benefits?’, or ‘Who benefits the most?’ – as not everyone
    sees local or regional warming as a problem). Perhaps worse is the possibility
    that G-enge will be used as an excuse to pollute even more i.e. it will be
    seen as a perpetual way to offset the results of our planetary mismanagement. It
    also has the difficulty that when it comes to proper maintenance, it becomes
    just another ‘built’ system that needs resourcing against other competing options.
    We only have to look at the errors – and negligence? – over the years relating to
    other (much smaller scale, admittedly) systems to appreciate the potential for
    serious mistakes and problems, e.g. as with nuclear power stations (remember Windscale, Three Mile Island, Chernobyl etc?), chemical plants or oil refineries(Flixborough, Seveso, Bhopal,
    BP Louisiana?), river/flood defences (New Orleans?), etc. etc. etc.

    Anyways, thanks for all the AGU posts – very informative. Over to Candide now,
    I think : ‘What’s next?’

  4. 4
    Thomas says:

    There have been a couple of recent papers (I’ve lost the links, they were in sciencedaily a couple of weeks back) about industrially enhanced silicate weathering. It would seem to me, that if something like this were to be found to be both economically affordable (cost per ton CO2) removed, and environmentally not too destructive, that this would be something we should look into. My gut feeling, we will probably come up with some schemes that remove CO2 at some rate, although that rate is probably much lower than current emissions. Even so it might provide a way for a post fossil fuel world to gradually reign in excess CO2.

    Any discussion of this? Im not equipped to judge whether this is realistic, or just a crude attempt to distract us from concentrating on emissions reductions.

  5. 5

    Geo-engineering is possibly an extension of human hubris, the same thing that got us into this mess. We need to restore the planet to pre-industrial state through negative population growth, forest expansion etc along with solar & wind energy. Let nature restore nature.

  6. 6
    Pete Dunkelberg says:

    Reminder: It is near the deadline for submissions to the Blog Articles Book

    What would you like people to know?

    Also, what are your Xmas book recommendations?

  7. 7
    Kevin Byrne says:

    Are there any climate models that incorporate permanent
    El Nino conditions?

  8. 8
    Aaron Lewis says:

    It is not global warming per se that is the problem, it is the rate of climate change. At a rate of 0.01C per century we can adapt to huge changes in climate. At a SLR of .02 meter per century we can adapt to almost any sea level change. However, rates of 0.1 C per year for climate change or .2 meter year SLR will destroy our civilization in a short time.

    Geo-engineering seeks to introduce changes in the global system that are so rapid as to reduce our rapid rate of climate change. To be effective in the limited time available, the geo-engineering effects would have to be very intense. This will introduce very rapid, intense, local weather changes.

    It does not help wheat and rice farmers whose crops would be wiped out due to freak weather, that the freak weather was caused by geo-engineering to prevent additional climate change. Are you going to tell all the bees to stay inside because we are going to be “geo-engineering” next spring and there may be some freakish weather? Are you going to take almonds, apples, pears, cherries, squash, melons, potatoes, and etc off the global menu? (Well just for a few years until we get this global geo-engineering thing done, then if any bees and other pollinators have survived, we can get some seeds out of the repository, and go back to eating.)

    It does not help the people that would starve because crops were wiped out by geo-engineering, that the geo-engineering may help avoid the loss of some oil company’s infrastructure. And, if enough people starve, then the oil company will not need the infrastructure, because they will not have the customer base.

    Moreover, since Arctic Ice is melting faster than predicted by the models, we may not have as much time to complete geo-engineering as the models predict.

    If we are going to talk about public policy, we need the think through the details. I am not saying the above will come true in any geo-engineering scheme. I am say that the guys talking about geo-engineering have forgotten where their food comes from, and how it is produced.

  9. 9

    What data/papers point to a permanent El Niño during the Pliocene? How strong is that evidence? I know that some climate models seem show that we will get a permanent El Niño, while others don’t (I remember the RC posting on this a while back seemed to shrug it’s shoulders, suggesting confusion over what will happen to El Niño).

    And what was different about the Pliocene orbital configuration? Are there any reasons that we couldn’t use the Pliocene climate (world 3 degrees C warmer but CO2 only around 400ppm) as an example of what will happen over the long run? I guess, what I am saying, is there any reason that CO2 sensitivity would be higher in the Pliocene than today?

    I guess if I have such questions, I should really go to AGU myself…

    Thanks for all the great updates from conference.

  10. 10
    sue says:

    The warnings of scientists about the potential hazards of geoengineering are sobering. What is more sobering is concerns that politicians and industry people who resisted predictions of global warming based on modeling will also resist any predictions of hazards of geoengineering. They refused to acknowledge the predictions of global warming models, why should they acknowledge the predictions of geoengineering models??

  11. 11
    Jim Redden says:

    Again, Raypierre, much thanks for sharing.

    In the previous RC discussion of climate engineering, it was pointed out that we are already clearly inadvertently geoengineering climate. Besides CO2, we have urban and agrarian albedo changes; here in California, massive water projects change the desert of Sou Cal a land of lawns and ficus, and in the central valleys, field evaporation from farms change alter the microclimate by increasing the water vapor greenhouse effect–as it was explained to me… the polemics of geoengineering are complicated at best. Anyway…

    A somewhat tangential layman question-comment regarding Ralph Lorenz and Maximum Entropy Production (MEP) models: Has there been any practical application of MEP to Earth climate, in any predictive or practical sense?

    I seem to recall reading papers portraying anthropogenic climate change in less serious terms using MEP as a justification.

    On the other hand, my beginner interpretation of MEP seemed to indicate reasoning that the sustained application of a forcing may be subject to a protracted delay in observation. Until the system (in this case Earth climate) moved to a new equilibrium phase, climate sensitivity would be grossly underestimated.

    In both cases, the stability of climate and very rapid change seemed to fit MEP possibilities. The relative simplicity of MEP is what I found alluring, but wonder if anyone who has more refined thinking about this can comment?

  12. 12
    Chuck Booth says:

    Lest anyone think that geoengineering schemes to modify (or stabilize) climate, and concerns about those schemes, are something new, here are excerpts from a paper on this topic published in Science in 1974 [Note: The authors were concerned about food and water shortages ravaging Africa in the early 1970s – they were not talking about the nuclear winter scenarios or a new ice age that AGW skeptics keep suggesting were dominating the thinking of climatologists at that time]:

    W.W. Kellogg and S.H. Schneider (1974) Climate Stabilization: For Better or Worse? Science 186 (No.4170): 1164-1172

    …So far, we do not have a comprehensive climate theory that can explain- much less predict- these trends. Nevertheless, we understand enough about the earth-atmosphere system to recognize that humans can affect it, and surely have already, by pushing on certain “leverage points” that control the heat balance of the system. If we continue to expand our global activities, our influencess on future climates will be still greater.

    If we could forecast climate changes we would be faced with several options. First, do nothing. Second, to alter our patterns of land and sea use in order to lessen the impact of climate change. And third, to anticipate climate change and implement schemes to control it….

    It may be useful now to summarize some important points and questions we have discussed in connection with potential climate-related conflict situations: [Note: a colon was inserted in place of a period in the original text]

    1) The atmosphere is a highly complexe and interactive resource common to all nations.

    2) Decision-making with unsharpened tools (such as climate models) may become necessary.

    3) What if we could trace climatic cause and effect linkages? Accusations would abound.

    4) What if one nation perceived climatic cause and effect linkages? Could this be used as an excuse for hostility?

    5) What if one nation could predict climate? This would change entire international economic market strategies or might lead to pressure for climate control.

    6) Who would decide and who would implement climate modification and control schemes> The cost of miscalculation (or perception of miscalculation) are immense.

    We have the impression that more schemes will be proposed for climate control than for control of the climate controllers. Whether or not purposeful climate control is ever needed or realized, the problems of inadvertant climate modification, climate prediction, and feeding a growing world population suggest the timeliness of studying potential climate-related crisis and conflict scenarios. This is the first step. In any case, the objective of understanding and anticipating natural, inadvertent, or purposeful climate change and its consequences for society must, in our view, continue to be a major interdisciplinary goal. While it is essential to work out international mechanisms to guarantee that any new knowledge of our climate system will have only constructive uses, the price of human suffering of continued ignorance of the causes of climate change may already have become unacceptably high.

  13. 13
    Anthony Leonard says:

    Another thanks for your reporting on the recent results from this meeting!

    Regarding geo-engineering, was there any discussion, or opinions, on the viability of producing biochar for carbon sequestration? From what I have seen it offers potential for significant help if it can be demonstrated that the charcoal remains stable as long as its backers claim. It has the potential to be widely implemented from the scale of single farms to much larger operations. Biochar also appears to be a highly valuable soil amendment, improving fertility with lower fertilizer and water requirements. Large scale implementation probably will rely on the IPCC, or other appropriate body, to recognize it as a validated carbon sequestration technology in order for its use to be eligible for carbon credits.

    I was wondering if the climate community has begun to discuss or evaluate this possibility. At this time I mostly only see its enthusiastic promotion by a smaller community.

  14. 14
    David B. Benson says:

    Thomas (3) — Emissions reductions are important, but there is a completely viable scheme to permanently and safely sequester carbon: produce biocoal via hydrothermal carbonification and bury the stuff in abandoned mines or carbon landfills. I don’t know about the cost, but it would be environmentally anti-destructive.

  15. 15
    David B. Benson says:

    Oops. Hydrothermal carbonization.

  16. 16
    Thomas says:

    (11) I would be interested in learning about the process. Especially if it could be made a byproduct of say geothermal power, or some other energy generating scheme. I’m not of the opinion that any of the schemes are a substitute for emissions reductions, but they might have a part to play in mitigating the damage after we discover we did too little too late.

  17. 17
    David B. Benson says:

    Thomas (13) — Yes, the reaction is exothermic.

    Popular accounts:,2144,2071791,00.html

    A demonstration plant, using forestry wastes, is described in the following link.

    A more technical article:

    M.-M. Titrisci, et al.,
    Back in the Black: hydrothermal carbonization of plant
    material as an efficient chemical process to treat the CO_2
    New Journal of Chemistry, 207, 31, 787–798 (25 references). (Linked below)

    or as a .pdf file


  18. 18
    John Wegner says:

    The 100,000 year cycle of Pacific sea surface temperatures might have something to do Milankovitch cycles.

    The overall cycle switched from 41,000 years to 100,000 years about 1.5 million years ago. Maybe it was sooner according to this data.

    I always thought the glaciation cycles started about 2.5 million years ago.

  19. 19
    Walt Bennett says:

    It is important not to assign specific definitions to the very general term “geo-engineering”. As David Benson suggests, sequestering carbon is a form of geo-engineering with no worries about unintended atmospheric effects. Methods may be developed to remove carbon from the atmosphere.

    “Cooling” the climate by blocking solar energy would be an extreme measure, to be taken only if the worst stage of the crisis has been reached.

    Realistic measures to transform the grid off of fossil fuels in a cost efficient way, combined with imaginative geo-engineering efforts, might end up being the cocktail that successfully balances science and social policy.

  20. 20
    Chuck Booth says:

    Re # 11 David B. Benson: “a completely viable scheme”

    Viable in what sense? Technologically? Environmentally? Economically? All three? How about providing some documentation on this?

  21. 21
    Andy Wickens says:

    Just wanted to reiterate the thanks as a “lay public non-scientist (Librarian)” – I appreciate your summaries and doubt any standard news outlet covered much, if any, of this conference (I heard nary a peep). I was particularly excited to be able to see Dr. Lonnie Thompson’s speech, as he’s a bit of a hero for me.

  22. 22
    Lou Grinzo says:

    Geo-engineering is the topic in the energy and environmental arenas that scares me spitless. If you look at where much of our CO2 emissions come from–coal-fired electricity generation–and how hard it will be to sequester those emissions or replace that generation with CO2-free ways to move electrons, it becomes clear that even with an enormous amount of political will and funding we’ll have one heck of a hard time reducing emissions in a reasonable time.

    I fear that we’re on a collision course with geo-engineering, and that much of the talk about it in mainstream circles will make it sound like a (relatively) cheap and safe fix, and therefore a “good” argument for us not to do the hard (and politically distasteful) work of reducing emissions aggressively.

  23. 23

    Reply to 2 Nick O. and 5 Pete Dunkelberg
    On Chernobyl: Alex Gabbard wrote to me: “The reactor that had the accident at Chernobyl was very out-of-date (1st generation) design that has to be precisely controlled to prevent cooling water from boiling. Water carries away heat and moderates far better than bubbles, and as bubbles form in water, the reactor goes increasingly unstable. What caused Chernobyl to blow its top was residual water in the core suddenly going to high pressure steam and erupting into a steam explosion. Since the building top was simply resting by its weight on the walls, not a containment vessel at all, the steam explosion burped the top off its position allowing outside air in, subsequently igniting a carbon fire.” The United States and other Western countries DO NOT now build and do not now posses or operate ANY reactors of such primitive design. Nor do we allow containment buildings to have easily removable tops. Containment buildings in the Western hemisphere are required to be pressure vessels.
    The Chernobyl accident released only 200 tons of radioactive material, as much as a coal-fired power plant would release in 7 years and 5 months. The Chernobyl accident had a shorter “stack” than coal-fired power plants. The radioactive material was released in a short time at ground level. That is why the Chernobyl accident had impact. Only 52 people died at Chernobyl , mostly fire fighters, a hazardous job in any case. The Three Mile Island incident did NOT release a noticeable amount of radiation into its neighborhood, it was just expensive to clean up the inside of the reactor. Nobody died and nobody was injured at Three Mile Island.

    To read more from Alex Gabbard, go to:

    Please give this book for Xmas: “Environmentalists for Nuclear Energy”, by B. Comby
    English edition, 2001, 345 pp. (soft cover), 38 Euros
    TNR Editions, 266 avenue Daumesnil, 75012 Paris, France;
    ISBN 2-914190-02-6
    order from:
    Read a review of this book by the American Health Physics Society at:
    Association of Environmentalists For Nuclear Energy [EFN]

    Please give this book for Xmas as well: “Six Degrees” by Mark Lynas. Read a summary at:

    Please give this book for Xmas: “How to Tell Which New Car Will Last Longer” by Edward Greisch. It is available only as an Adobe Acrobat (.pdf) download from:

    We don’t recycle nuclear fuel because spent fuel is valuable and people steal it. The place it went that it wasn’t supposed to go to is Israel. This happened in a small town near Pittsburgh, PA circa 1970. A company called Numec was in the business of reprocessing nuclear fuel. I almost took a job there, designing a nuclear battery for a heart pacemaker. [A nuclear battery would have the advantage of lasting many times as long as any other battery, eliminating many surgeries to replace batteries.] Numec did NOT have a reactor. Numec “lost” half a ton of enriched uranium. It wound up in Israel. The Israelis have fueled both their nuclear power plants and their nuclear weapons by stealing nuclear “waste.” It could work for any other country, such as Iran or the United States. It is only when you don’t have access to nuclear “waste” that you have to do the difficult process of enriching uranium.

    There are other climate engineering options, such as placing mirrors or other obstructions at the first Earth-Sun Lagrangian Point to block sunlight. Doing this would use up as much money as our military budget. I would guess that it would result in less food because there would be less sunlight reaching the Earth.

  24. 24
    Dick LaR says:

    Reducing GHG emissions to the atmosphere is necessary but not sufficient because atmospheric GHG concentrations will still increase, albeit at a slower rate. Solar input to Earth already exceeds IR radiation to space, so the oceans will continue to store heat. Ice melting will continue to accelerate.

    We need additional help, like pumping up deep cold water and distributing it at the surface at the rate of one million cubic meters per second. In addition to surface cooling, the up-welled water will supply nutrients to increase food production and slow down ocean acidification.

  25. 25
    Ray Ladbury says:

    David #11, wouldn’t the process you are talking about also remove nutrients from the soils for each ton of carbon sequestered? Would that not render it ultimately unsustainable? And if we are relying on biofuels as well as bio-sequestration, isn’t that going to tax the abilities of agriculture to feed 12 billion people as well?

  26. 26
    Nick Gotts says:

    Raypierre, thanks for your reports – for me, reading them was in at least two ways better than being there: no transatlantic flight, and an expert interpreter of the science.

  27. 27
    Hank Roberts says:

    Me too, Raypierre.

    I’ve been reading your blogging from AGU in parallel with Tom Athanasiou’s blogging from Bali, for example

    Some week the scientists and government representatives should do one of these events in the same place at the same time with a shared program.

  28. 28
    Mike Tabony says:


    Thank you very much for all of the time, knowledge, and energy you gave to your reports. In a country where GW is virtually ignored by the major news oganizations your reports were a treasure for the layman. I’m saving them as information sources for my high school lectures on AGW and its consequences. Have a good rest and a happy holiday.

  29. 29
    James says:

    Re #11: […produce biocoal via hydrothermal carbonification and bury the stuff in abandoned mines or carbon landfills.]

    Might be interesting in the long term, but it seems kind of pointless, even wasteful, to bury biocoal at the same time other people are busily digging up natural coal and burning it.

  30. 30
    David B. Benson says:

    Chuck Booth (16) — Technically and environmentally. As I stated, I don’t know the costs. See my post #14.

    Ray Ladbury (18) — No more than cutting down trees to make logs does, which is very little. (Most nutrients are in the leaves.) One can always fertilize as required. I don’t know about 12 billion people, but feeding 9 billion plus bio-fuels leaves a sizable excess capacity of non-agricultural (too degraded), non-bio-fuel land which could be utilized for the produce of biocoal.

  31. 31
    per says:

    Re #11

    Hydrothermal carbonized biocarbon is by the way, due to it’s supercritical washed out quality, sometimes used as absorbant of smelly volatile organic compounds found in drinking water; chlorine, petrol fumes etc.. and should not be buried untill loaded with the maximum amount of smelly pollutants.

  32. 32
    Bryan S says:

    “Since the Northern Hemisphere ice sheets had not yet formed at this time (Pliocene)”

    Raypierre, your statement is likely not correct. There is considerable sedimentary evidence that glaciation was firmly established on Greenland during the Middle to Late Pliocene, and its beginnings can be traced all the way back to at least the Middle-Late Miocene. If not, then one has some explaining to do. During the Late Miocene, global sea levels fell 50-100 meters below present during at least one short event. With no ice sheet in the NH, it begs the question of where is the missing ocean volume? To some degree, it is likely taken up in the Antarctic Ice Sheets, but possibly to a lesser degree in the NH. It is also important to note that as a whole, the Miocene was even warmer than the Pliocene, but was nevertheless typified by rapid growth of the SH Ice sheets.

    [Response: Written somewhat in haste. I should have made it clear that the transition period under discussion is the stretch beween about 3.1 million years ago and 2.5 million years ago, and it would be fairer to say the Northern hemisphere ice sheets were not yet fully formed, as there is indeed evidence for some NH ice at this time. I suppose there’s the question of how big the NH ice sheets have to get before they can have the kind of rectification effect that some people have proposed for selecting out a 100Kyr cycle. In any event, a 100Kyr cycle in tropical temperature is very interesting in the Pliocene, since 100K doesn’t set in as an important rhythm in ice volume until the mid-Pleistocene. –raypierre]

  33. 33
    Andrew says:

    “I continue to think that geoengineering is a big and unfortunate distraction, but since the cat is out of the bag, it is good that some people are doing the work to head off rosy and over-optimistic projections of sulfate geoengineering as a magic bullet that could substitute for the hard but necessary work of mitigation of CO2 emissions.”

    There really isn’t a qualitative difference between a “geoengineered” solution and reduction in GHG emissions.

    You have an imperfectly known high dimensional nonlinear system in front of you, and you have some things that you can regard as control inputs (sulfate or CO2 emissions, etc.), and some things (e.g. global average temperature, arctic ice volume, etc.) that can be regarded as outputs. Even if you are skeptical of AGW, you can at least agree that the problem can be formulated this way – presumably skeptics just feel the transfer function from some inputs is smaller than other people think.

    Now the plant is imperfectly known, and the future of the control inputs is not certain (hence the scenario based approach we have seen with GHG projections).

    So fine. I think everyone can agree that this is a formulation that leaves out nothing and includes nothing extraneous. It is particularly well suited to plants that have feedbacks that are not completely identified.

    What does it get you? Well, when we consider the question of whether “geoengineering” or GHG reduction is preferred, it is really in terms of the cost of control for some performance specification. This formulation allows you to objectively and rigorously compare, to the extent that your knowledge supports such inference, different approaches to climate control.

    One really important thing that you would get from this formulation is that it would provide with estimates of the cost of uncertainty – in other words, you get bounds on the cost of control which include the effect of uncertainty; you can view this as a lower bound on the value of reducing the uncertainty. For parties who had differences in their idea of what is the right performance specification (“why should WE pay to preserve YOUR climate”) they can use this as a guide to how they should invest their resources.

    The thing that I would look for first in this sort of approach is whether one or another time scale ended up dominating the contollers that got synthesized for various reasonable performance specifications. That would tell you a lot about which atmospheric species to pay attention to. Offhand I would guess that the long lifetime of CO2 would make it the most economical control variable, but at least this would be an objective way to test that notion.

    [Response: There’s a huge difference between sulfate geoengineering and CO2 mitigation. In the latter, you’re restoring the system to a previous state, whose behavior was known. In the former, you’re taking it into a new kind of state, with a fundamentally different kind of energy balance, and you have no good analogue in nature to help you make sure there isn’t a disaster lurking. Now if by “geoengineering” you’re including things like pulling CO2 out of the atmosphere and sequestering it, there I’d agree with you; there’s not much difference there between mitigation and CO2 removal. The decision between the two comes down to cost, feasibility and side effects –raypierre]

  34. 34
    Harold Ford says:

    I like the biocoal idea. What this all seems to boil down to, for me anyway, is this: CO2 still has positive uses no matter the fact that we seem to have too much of it. It’s part of the carbon cycle system, we need to determine how much is too much or too little. I would guess that means deterimining how much to burn or store over a 2 year cycle assuming we have some decent feedback as to the density of CO2 and methane in the atmosphere. Does it produce methane if stored for long periods of time?

    The idea of using aerosoles to control the greenhouse effect is… well, about as good an idea as saying global warming is ok. The aerosoles would, as I understand it, erode our atmosphere’s natural tendancy to block harmful cosmic rays which is said to be a source of natural mutations. It sounds like aerosoles would help make the planet a microwave. My tax dollars could be spent better elsewhere.

    Anywho, I’m still in favor of this process, whatever it is: growing plants such as trees and grass to collect CO2 and using the mature trees for building or store them with the decaying in a natural gas collector. Various stages of decay would yield products that could be used in farming. The idea being not to increase the time of decay but to store the carbon in the form of decaying grass and wood chips/trees. The natural gas produced would have to be burned, oh darn, probably to produce electricity or somthing.

  35. 35
    Mike Tabony says:

    Thanks for the time, experience, and energy you have given for your reports. I’m saving them as references for my high school lectures on AGW. At a time when the major news organizations say so little about the subject your posts have been very educational.
    Thanks again.

  36. 36
    Ferris says:

    Ray #18 – No, it’s exactly the opposite. Biochar was initially created in an attempt to reproduce the Terra Preta soils found in the Amazon Basin. These soils are uncharacteristically productive and have very high naturally occurring nutrient levels because of biochar.

    If biochr can be produced efficiently and economically, it will be a win-win for everyone involved.

    Wiki has some good info on Terra Preta.

  37. 37
    raypierre says:

    It’s just been pointed out to me that one of the AGU geoengineering talks I missed — the historical talk by James R. Fleming on Harry Wexler, the ozone hole, and geoengineering ideas circa 1962 — actually presented new material beyond what I’d seen before. I really regret having missed this, as James is always illuminating to listen to. You can find some of the contents of his talk at

  38. 38
    Florifulgurator says:

    Terra Preta, biochar…
    This can be done efficiently and economicly, but perhaps not in the large scale super duper tech that big biz likes: Teach the poor small farmers to make charcoal instead of burning down forests. There are ovens where to put in wood and get out char coal. Wood gas driven automobiles are known since WWII. The next real innovation in car technology after Ford’s Model T (1909) would be the wood gas hybrid: Get wood pellets at the gas station, dump the charcoal there, and voila: Drive carbon negative.

  39. 39
    pete best says:

    I bet that at some point over the next 50 years having failed to mitigate CO2 enough we will attempt geoengineering projects of some kind. James lovelocks recent attempt via tubes places in the ocean with valves to allow colder waters to rise to the surface to stop the oceans from stopping abosrbing CO2.

    how much CO2 could be removed from the atmosphere and what would power the machines that did it (even if it is possible)?

  40. 40
    Lawrence Coleman says:

    I thought the bali meeting was a virtual waste of time, with the usa as usual showing absolutely no leadership and almost vetoing the whole process. It clearly shows the white house still doesn’t understand it’s responsibily in the issue. For the vast part of last century the usa was the single biggest emitter of greenhouse gasses therefore it should stand to reason that it is also the usa that should take greatest responsibilty in initiating meaningful emission cuts. Yes! Mr Bush- emission cuts might slightly strain the economy..but it was largely that same reckless polluting economy that has plunged the world to the edge of the abyss. So if any country should take the lead in this dilemma it’s america. If the usa only had displayed more guts and leadership rather than it’s typical self serving approach- china and india would have probably have had the confidence to go with achievable and immediate emission targets.

  41. 41
    Alexander Harvey says:

    Re Jim #8:

    There are of critisms of the MEP principle, when it was used by Patridge (1975) it was novel and the theoretical under-pinnings weak. Also it was criticised for being a little light on both mechanism and results. I feel it became a bit of a backwater.

    Since then the MEP and the maximum caliber principles have gained much stronger foundations.

    I do not think that there is much of a problem with the principles any longer.

    MEP does involve a shift in the way that problems are handled. Particularly the reduction of information to its relevent content. For instance, it was shown by Paltridge that the zonal temperature distribution and the corresponding fluxes could be reproduced assuming a very small number of constraints. The implication being that the vast amounts of nitty-gritty that are the hallmark of the best climate models are irrelevent “when considering zonal distributions”. They are however vital when predicting the weather.

    An implication of the principle is that the difference between our initial MEPP values and observed values are a measure of the unknown constraints. As the initial fit can be viewed as pretty close then the major constraints must be as used by Paltridge. I think that many find the idea that an important measure of the general climate can be largely explained in such a simple way to be unplatable.

    At the basis of MEPP is how to make inferences from partial information and may represent a brickwall as to what can be inferred regaring the climate given our limited knowledge. That is it could have something to say about the limits of predictions.

    That sounds a bit negetive. On a more positive note it will be of interest to see if the output of various models do conform to the MEPP and to maximum caliber and if they don’t why not.

    Alexander Harvey

  42. 42
    Ray Ladbury says:

    Andrew, you claim there is no difference between CO2 reduction and sulfate/aerosol geoengineering. Hmmm, if we look at the IPCC summaries, where are the biggest uncertainties? Yup, aerosols. Where are they among the smallest? GHG forcing. I’d call that strike one against aerosols.
    What timescale do GHGs act on? Hundreds to thousands of years. And sulfates? months to years. Strike 2.
    And sulfates will likely be much more effective in acidifying the oceans than CO2. Strike 3. Thanks, for trying.

  43. 43
    Andrew says:

    Raypierre: “There’s a huge difference between sulfate geoengineering and CO2 mitigation. In the latter, you’re restoring the system to a previous state, whose behavior was known. In the former, you’re taking it into a new kind of state”

    From the point of view of control theory, and for that matter, from the point of view of public policy, there is no qualitative difference between geoengineering and “mitigation”. You have a system which will approximately do X, you want it to do something closer to Y instead, and you want to know if that can be achieved, and if so, how should it be most efficiently done, and what will it have to cost?

    Now you claim that the behavior of the previous state is “known”. I would suggest that it is preferable to regard the previous state as possibly less uncertain. This uncertainty is probably much larger than might be thought at first sight. Suppose we thought it were as simple as choosing a year and “dialing the climate back to that year”. Well if you pick a year in the industrial era, then that “climate state” is a point on a trajectory of a forced system, not necessarily having any unforced stability properties (and in fact very likely not having any). So to control the system to that state (extended perhaps as a constant in time), you may have to spend a lot to stabilize it. Yes it’s nice to know that we have attempted to measure the sensitivity of that sort of state to forcing, but that is not the same as computing the minimum cost of artificially stabilizing that state.

    Suppose on the other hand you dial your wayback machine back further, then the cost likely increases and your knowledge of that state and the dynamics decreases.

    I think you might be pretty optimistic about what “previous state” actually entails in terms of the entire climate system – who is going to “reset” the abyssal circulation to that previous state? This is an example of part of the system which is very expensive to control, unless we are cognizant of controlling that part of the system on a different timescale than we seek to control other parts of the system such as the global average temperature.

    But as soon as we recognize that we are going to control different parts of the system on different timescales, then we also recognize that it will be a very long time before we actually return the system to a close analog of any past state that we know to any great degree. But over the longer timescales that it will necessarily require to get close to any previous state, the biosphere is going to change quite a bit. In particular, how many humans will be there when we arrive at that previous climate, and what gases will they choose to emit? Will there be an asteroid impact over that timescale?

    What occurs here is a situation called “recourse”. It means that the control policy itself is sensitive to the system under control. The computational complexity of controllers with recourse is often prohibitive. In human reality, the politics probably do not admit controllers that are held constant over centuries, let alone millenia. So it appears necessary to restrict attention to a relatively short time – such as a century, during which time it is unlikely that we are going to control the system to anything close to a constant state, and over which period large and important aspects of the climate system will be essentially uncontrolled.

    So we will not be “going home again”. At least not any time soon.

  44. 44
    Martin Vermeer says:

    #43 Andrew,

    if you strayed into a minefield, what would you do? Carefully retrace your steps? Step where there are other footprints? Or rush the shortest — or any plausible-looking — way out?

    What Raypierre meant by previous/known state, was a collection of states or ‘regime’. Even the current state of the climate system is still similar to, or within the regime, where it operated during periods of time in the recent geological past. Nothing very weird happened then, which is somewhat comforting.

    Continued build-up of GHG would put us deeper and deeper in ‘uncharted territory’, with no real (recent) paleo analogues. Some of that will happen anyway, because of what’s in the pipeline. Yes, it is about risks and probabilities. Not mitigating (which is actually well affordable if you start in good time, cf. IPCC AR4 WG3) is simply not on the table for prudent decision makers, with or without geo-engineering.

    The only valid reason I see for using aerosol geo-engineering would be as a semi-desperate symptomatic treatment, like giving the patient a fever suppressant to keep him alive until the antibiotics start having their effect. Aerosols work immediately, mitigation is a long term systematic effort.

  45. 45
    Greg says:

    As a college student in one of these cities:, I feel it is my duty to help publicize this list. If everyone in the country went and got their Carbon Footprint score from and then took just one pledge I think we could stop global warming. Not only is it fun to see where you land compared to these cites, but you can compare to your state, US etc…This tool is vital to the international fight against global warming.

  46. 46
    Greg says:

    Hey can you believe Chicago is number one on this list of top green cities? This article talks about the greenest cites. put together this list; it is a sample of like over a million people. I took my personal carbon test and blew the national average out of the water! I took some of their pledges too so I will be getting further and further below the average. It feels good being one of the people helping to lower my cities average rather than raising it, and I think all people can contribute if they take a pledge or two.

  47. 47
    David B. Benson says:

    Andrew (43) — That was a well-done warning. Thank you.

    As an example, it will be feasible, even economically so according to Biopact, to remove about 350 Gt of carbon from the active carbon cycle in the next 70 years, while at the same time not adding any by the use of bio-fuels, etc. However, this may well not restore the ocean chemistry and biology, hence not returning the planet to the state enjoyed during the 1950s.

  48. 48
    Ralph Smythe says:

    Couldn’t we remove CO2 from the atmosphere by increasing the amount of biomass and topsoil to create a greater sink fairly easily? What does the research into AGW say about how much is now being sunk and how to increase that (and one would imagine, food production if the biomass is edible).

  49. 49
    Hank Roberts says:

    > 350 Gt
    Net, or gross?
    That would be almost half the total CO2 in the atmosphere, if they mean net. It sounds like magic.

  50. 50
    David B. Benson says:

    Hank Roberts (49) — My understanding is that since the beginning of the industrial revolution, humans have added about 500 Gt of carbon to the active carbon cycle. As 350/500 = 0.7, this means the removal of about 70% of what has been added since 1750 CE.

    Not magic. Biopact’s assumption is that carbon capture (in the form of carbon dioxide) and sequestration (as liquidfied CO2 in deep saline formaions) is going to work, both technically and economically. Then using biocoal in CCS coal reactors is carbon-negative as indeed are any of the means of producing bio-fuels which has a utilized CCS capacity.

    For simplicity, assume it was possible to instantly convert completely now. Then removing 350 Gt in 70 years only requires successfully sequestering 5 Gt per year.