Runaway tipping points of no return

A translation into Slovak is available.

207 comments on this post.
  1. Todd Albert:

    Great summary. My favorite use of “tipping points” thusfar was by Al Gore in a recent interview on PBS. He stated that he (I am paraphrasing here) “understands less about climate than many climatologists have forgotten, but he understands politics, and in politics there are tipping points, too.” He then continues to say that great things can happen almost suddenly when enough people get on board. This is the justification he gives for his new movie and his desire to train more people to give his slide show. Does anyone know where he is going to recruit the 1000 people from? I’d love to be trained to give his slideshow. The graphics are far better than those of my own slide show that I give fairly often.

  2. Edward Wolf:

    I’m not sure about Al Gore’s “presentation training” plans, but it may be a large part of the nonprofit Alliance for Climate Protection that he is organizing.

    Another source for presentation training is the nonprofit Green House Network (, which since 2000 has organized low-cost speaker training workshops in many parts of the country, including climate scientists, resource scientists, activitsts, and communicators among its trainers. These workshops have trained hundreds of presenters from many walks of life, who collectively have given thousands of presentations on campuses, to community and business groups, etc. The next workshop, billed as a “Global Warming Solutions Weekend Retreat,” is scheduled for Spring Green, Wisconsin on July 14-16. See the Green House Network’s Website for details.

  3. Jan Theodore Galkowski:

    fabulous posting! i have long wished for a blog entry or article that described this clearly. i had it on a list of things to do myself, but never got to it. i alluded to this idea frequently in discussions, the “tunneling” phenomena in some non-linear systems, but had nowhere to send people except things like Hirsch, Smale, Differential Equations, Dynamical Systems, and Linear Algebra, ISBN 0-12-349550-4, 1974.

    thanks very much!

  4. John Fleck:

    Excellent discussion, Gavin. Realclimate readers might also be interested in Gabrielle Walker’s discussion of this topic in the 15 June Nature:

  5. Hank Roberts:

    Link for abstracts of the two papers Gavin refers to:

  6. Coby:

    Re glacial cycle CO2 and temp correlation, it is useful to remember that the timescale of that record is 100’s of thousands of years, where as the CO2 rise today has occurred over ~100. The temporal resolution of the ice core records is also very coarse, millenia between samples, so one would have to wait maybe 10K yrs and look back to see if we have the same T and CO2 correlation (assuming there is ice left to core at that time). We may still see very good correlation on the one or two century scale but don’t forget that thermal inertia, mostly in the oceans, causes a long delay before T can catch up to CO2.

    Gavin’s point about the physical mechanisms being totally different now still stands.

  7. Coby:

    I think that this record also shows a significant tipping point scenario at ~12, ~22 and ~34 Myr bp with the formation and disintegration of the Antarctic ice sheet.

    I suppose that one is still pretty far off, but I would not be surprise if a few hundred thousand years from now, or less, there was no ice left anywhere. If Greenland “tips”, the WAIS may follow then temperatures would go high enough to eventually melt the EAIS to the bedrock.

  8. tapasananda:

    It is not for nothing that Al married Tipper.

  9. Wacki:

    “Eemian/Stage 5e period (about 120,000 years ago) when temperatures may have been a degree or so warmer than now ”

    Just curious, since the CO2 levels are much higher now than they were back then, why was it hotter back then?

    Also, CO2 and temperatures seem to line up very well in this graph:

    They also seem to line up here:

    So if CO2 levels are so much higher now (26% higher than any point since 420K years before the industrial era), why aren’t temperatures lining up?

    [Response: The orbital configuration was different, with warmer NH summers than today (or even the early Holocene). That seasonal change may have been crucial for the ice sheets. See the recent Overpeck et al and Otto-Bliesner et al papers in Science for what climate differences one would expect. With respect to today’s CO2, that is not being changed by anything like the same mechanism, and so simply correlations with past data are not going to help. -gavin]

  10. John Bolduc:

    Regarding Hansen’s advice about 10 years, it seems like you are softening his statement. In his recent article in the New York Review of Books (see he states “…we have at most ten years — not ten years to decide to decide upon action, but ten years to alter fundamentally the trajectory of greenhouse gas emissions.” So I take him to mean that we have to “start” seroiusly to reduce emissions somewhere between now and 10 years, not by 10 years from the present. Obviously Hansen’s is one very informed scientist’s opinion, so maybe 10 years is overly conservative. But given your description of tipping points and points of no return, a conservative approach seems to be in order.

  11. Thomas Lee Elifritz:

    A few hundred thousand years?

    You are several orders of magnitude off with that comment. Current rates of carbon dioxide increase indicate total global deglaciation in the order of ~1000 years.

  12. Jeffrey Davis:

    A name for the phenomenon?

    widespread panic
    cower tipping
    defrost on the punkin’

  13. Mark J. Fiore:

    Excellent post.Take that factor down by 10 to complete deglaciation and loss of all ice at poles within 100 years. Long before that thermohaline shutdown and superstorms and 20 foot sea rise. If co2 emmissions not reduced by 80 % NOW there is very little hope of bypassing the tipping point. Good post, good comments. Hope the Republicans(who hold all the power in all three branches) are listening.Some disappointment on lack of support for AB32 here in CA by certain “Democratic” state legislators.
    Thankyou to all the posts and comments from your site. You guys are cool, and should be mandatory reading at Senate briefings.

  14. Wacki:

    “You guys are cool, and should be mandatory reading at Senate briefings.”

    Senator Inhofe has already made Crichton’s “State of Fear” mandatory reading for Senators. I’m being dead serious btw.

  15. Wacki:


    “The orbital configuration was different”

    Do you have any suggested reading on this? How exactly do they know what the orbital configuration was like 120K years ago?


    Hank Roberts,

    Thankyou very much for the direct links.

  16. Tom Huntington:

    This discussion of tipping points is very timely, as you point out, the press seems to be quite keen on it as people seem to be able to relate particularly well to this concept compared with some others such as “dangerous anthropogenic influence” or “catastrophic change”. Some other analogies:

    “The horse has left the barn”

    “Crossing the Rubicon” From Wikipedia — “The use of crossing the Rubicon derives from the crossing of the river Rubicon by Julius Caesar in 49 BC, who thereby violated Roman law and rendered armed conflict inevitable. As Caesar said at the time: “alea iacta est” (“the die is cast”).”

    Or, related to having passed that tipping point, more figuratively, “he who mounts the wild elephant goes where the wild elephant goes” — I apologize for not knowing the proper credit for this.

    I think that Figure 1 in [Falkowski, P. G. and others. 2000. The global carbon cycle: A test of our knowledge of the Earth as a system. Science 290: 291-294.] is useful in making this point. It shows the correlation between atmospheric partial pressure of CO2 for the last 420,000 years and the deuterium-based air temperature anomaly. I think it is appropriate that the figure is a little dated in that ‘modern’ atmospheric pCO2 (plotted on the figure) is now literally off the graph and if you mentally plot a reasonable assumption for an atmospheric pCO2 stabilization in the future it is hard to imagine how we will return to a climate experienced in the last 420,000 years, much less a ‘pre-industrial’ climate in the foreseeable future.

    As intriguing a concept as it is, a ‘tipping point’ is less useful if poorly defined quantitatively or largely unknown, as apparently is the case with two key examples that you cite: thermohaline circulation and substantial melting of ice sheets leading to ‘dangerous’ sea level rise.

    I agree that it is important to point out that there can be many tipping points depending on your frame of reference. For islanders that have already been forced to relocate 20th century sea-level rise has already passed a tipping point of no return.

  17. Gerald:

    A name for the phenomenon?


  18. Isaac Held:

    Re #15: Here is one link on orbital parameters

    One of the major reasons that the ice ages are potentially such a useful test of our understanding of climate sensitivity is that we know, from celestial mechanics, with remarkable precision, exactly how the Earth’s orbit has evolved in time, at least for the past few million years

  19. Dan Hughes:

    With respect to the complete collapse of the Atlantic thermohaline circulation will you kindly clearify the following for me.

    It is my understanding that a fluid initially at rest on a rotating mostly sphere-like surface which in turn is revolving around a sun cannot remain at rest. If this is not correct let me know. Otherwise will you summarize the patterns of the induced motions for fluid bounded by the same boundries that now bound the ATC. That is, for fluid between North-Central-South America on the Western edge and Europe-Africa on the Easten edge.

    Additionally, what are the expected consequences of a “complete collapse”? This article ( seems to indicate that significant changes in weather/climate are not expected. Let me know if I have not correctly understood the article.


  20. Hank Roberts:

    This is a bit surprising — I wonder if this is why the Russian astronomer predicts a drastic change in climate in the next few decades? The change illustrated is over a far longer time span, but it’s striking in the graphic. I have no idea if this is one individual’s work or a consensus among astronomers.
    Gavin, Ray, worth at least a glance I suggest, I just stumbled on it:

  21. Robert A. Rohde:

    In the IPCC TAR, the report of Working Group II suggested that it is unlikely that we would reach any global scale tipping points (they used the terms “singularities” and “discontinuities”) before temperatures rose at least 2-3 C about 1990 levels. In the middle of the road projections, this corresponds to sometime in the latter third of this century.

    I realize Hansen is talking about the head long plunge of human and climate commitment, rather than the transition itself, but are there new results since the TAR to suggest that a tipping point might come earlier than previously expected? It seems rather severe to think a catastrophe is 60 or 100 years in the future, but we only have 10 years to ensure that it won’t happen. (Of course one does want to stay on the careful side in case the model results are too conservative.)

    I guess I am also surprised by how much press is devoted to tipping points, if, as the IPCC suggest, most of us may not actually live long enough to see such events. Not that I want my grandchildren to have to worry about it either, but it would seem more natural to spend more time on the problems we will already have before we get to the IPCC’s reported tipping threshold.

  22. Robert A. Rohde:

    Re: #15. I’d suggest Wikipedia is a good place to start: Milankovitch cycles.

    Orbital mechanics is very precise, and we can reliable describe the changes in the Earth orbit going back more than 10 million years. The present interglacial occurs during a period of low orbital eccentricity, and consequently the scale of the orbital forcing is lower now than during the last several interglacials.

  23. Mitch Golden:

    Re: #19 That is a very interesting article, and I certainly learned quite a bit from it. However, I don’t think you can read it to say that “significant changes in weather/climate are not expected”. What he points out is that the differences between London’s and New York’s climate are not caused by the heat transfer via the Atlantic current. As I read the article *both* New York and London would be somewhat (not hugely) colder if the current were turned off. Plus the equator would be warmer, and one could therefore assume that there would be more storms in the equatorial region and perhaps fewer in the mid-Atlantic.

    Not that I’m an expert or anything, but that seems to me what he’s saying.

  24. Nate:

    Aloha all. This is my first post here and actually my first visit here. I followed a link from to a list of the recently ranked Top 5 science blogs and this was one of them. After a good read, I can see why.

    I run a blog that is almost entirely political in nature but recently I decided to expand its horizons to include personal exeriences as someone who has spent so much time on and under the ocean.

    It’s titled: “The Canary is Dead!. The title of a movie put together by the PCRF.

    I am NOT a scientist by any stretch of the imagination. I’m a Navy vet who never graduated from college. But I have spent more time underwater by age 34 than most people will spend on or near the water in their lifetimes. So I would love to hear feed back from some of you smart folks. And possibly either encouragement to continue or suggestions to stop because it’s not my intention to put out any bad information.

    Thanks in advance everyone!

  25. cwmagee:

    Professional divers with the ability to operate underwater machinery are in demand by some, if not all paleoclimate labs. When I was a grad student, my officemate was an ex-diver who had come back to school to do a PhD. But because he was one of the few people at the school with the requisite hours to operate underwater drill corers, he went on every other reseacher’s field trips as a technician. I have no idea who, if anyone, is currently doing paleoclimate research in Hawaii. But if you are interested in getting involved and volunterring, they could probably use your know-how.

  26. Nate:

    cwmagee… Thanks for the follow up comment. For the past several years I have been building websites and media/marketing consulting to help companies improve their image and increase their bottom line and its been killing my soul a little bit each day. About a month ago I started selling off many of my “things” and wrapping up my yuppie condo lifestyle and I was planning on sending my resume’ out far and wide to organizations doing ocean and paleo-climate research.

    I don’t even mean to suggest that’s all I want to do. PCRF, research organizations of any kind. All I know is I want to use my talents to do something that won’t make me ashamed of what I’m doing with my life. Something I can actually do that would make me proud of myself again.

  27. Hank Roberts:

    #18, Nat’l Climate Data Center, includes a link to the same site I noted in #20 among many others, as a good recent calculation. Apparently the dating of geological epochs is now accurate to approximately 40,000 years (plus or minus, I think?), based on the best calculations of Earth’s orbit and the changes tied to that. Past 100k years chaos takes its toll.

  28. Scottzi:

    “I wonder if any else has noticed that we appear to have crossed a threshold in the usage of the phrase ‘tipping point’ in discussions of climate? We went from a time when it was never used, to a point (of no return?) where it is used in almost 100% of articles on the subject. Someone should come up with a name for this phenomena….”

    [Someone should hire an editor to check someone’s grammar.]

    Do you think that the fact that Malcolm Gladwell wrote a recent best-seller named ” The Tipping Point” might account for the increased usage of the phrase? I do. You might as well simply acknowledge the obvious. Add that to “An Inconvenient Truth,” and, well…duh.

    [Response: Possibly you might want to check your humour detection algorithms… -gavin]

  29. Johnno:

    I’m not sure I agree with CO2 levels .. are .. very unlikely to revert to pre-industrial values ..the next few hundred years . Actually I mean flows not levels. Oil depletion could have a dramatic slowing effect on economic activity taking coal burning with it. This seems to introduce the case of a flow variable (industrial CO2) perhaps passing a ‘tipping point’ but then slowing.

  30. Ethan Tiliakos:

    The progenitor of nonlinear dynamics was the -equally celebrated and at the conclusion disappointing, but nevertheless enlightening- concept of Catastrophe Theory, back in the ’70s. The name itself is appropriate and revealing, identifying “tipping” points as “catastrophe” points, whose configuration depends on specific multi-dimensional geometric structures that best describe the phenomenon of interest according to the number of relevant parameters.
    Nevertheless, the concept underlines the fact that these catastrophe points are not, actually, points of no return; they are rather points of not-feasible return, where the energy and time (or any other crucial governing factor) required to revert the system (like a planetary climate system) to a previous state is by far greater than the energy (or time, or…) that initially served as a feedback to drive it to the beyond-catastrophe state.
    In other words, whatever scope we look at the climate problem, it is at least uneconomical to expect to remedy the system after the damage is done.
    This is not doom-seering. A system of this magnitude, with this huge number of identified and unidentified governing factors, corresponds to a multi-dimensional geometric structure with proportionally numerous catastrophe points… When one of them is reached and crossed over, a new system state is reached, which rapidly leads to the next catastrophe point in line. And then to the next… and so on…
    My point is: if the debate really stalls at the question whether it is viable to act now or not, simply think: we may not be able to prevent the first wave of catastrophe events that will upset the system initially. But, we have to start considering what we can do about the next set of catastrophe points, which will probably be much more drastic than expected. Change may be abrupt, but it also happens gradually, one could say quantumly.
    Think about it. I am open to suggestions.

  31. Wacki:

    Thankyou for those that responded with the Milankovitch cycle links. I am aware of the fact that planets wobble, earths tilt effects seasons, mars caps are melting via topographic forcing, etc.

    However, I simply don’t see a pattern regarding to orbital configuration vs. global temperature in this image:

    I’m trying to find proof that those cycles were caused by a changing orbit and I’m having trouble doing so.

    [Response: Hays, Imbrie and Shackleton, 1974. (or read The Ice Ages by Imbrie and Imbrie – highly recommended). -gavin]

  32. SteveF:

    The following review by Mark Maslin is worth a read:

  33. Risto Linturi:

    I have been an appreciative reader of this site, not having anything useful to add. I have done quite much work on future research and virus marketing and this “Tipping point” -subject now seems a suitable place to try and perhaps contribute something.

    It seems to me that the Tipping point -concept would be much more useful when studying how to win converts to join the work. Basically what the world needs is a “phase change” in the attitudes of politicians, voters and bureaucrats. The most efficient conversion method is not through media but through social networks and small world phenomena – you change your opinion when your friends or collagues change their opinions and express their opinions to you directly. This happens one by one and it succeeds, if on the average, each convertee succeeds more than once (within short enough time if we have only ten years). Al Gore’s concept of spreading good slides seems to be very efficient as lecturers always need good material and make many converts.
    This site is also supplying very good material for all of us who wish to convince others. Especially important is the cautious avoidance of overextending the facts for a shock effect. This very easily leads to a backslash as happened in Finland with H5N1. (People generally think that the threath is passed as everything did not happen at once and then newspapers stopped reporting on the developments almost totally. And reality is that due to the events in Indonesia and few other places the probability has continuously risen. It may still take years for H5N1 to realize as a pandemic if ever and the popular support for efficient measures against the threath should last equally long as the threath.)

    Critical mass is required for efficient action against global warming and some of it has to be gained by other means than direct facts. Professionals can be converted by facts. Amateurs like me are unable to follow all the facts and know that one can be mislead. What convinces us is partially things that we believe to be facts and this kind of open high quality discussion, which one in principle could join. But most laypeople do not follow this kind of discussions. They may instead see one soothing article, which says that there is nothing to worry. And then they cling to this belief as it makes their life so much easier. It may also be that they just do not care what happens after they die. It requires a networked approach – each person needs to be converted by someone they can trust. Social pressure is also important. You do the right thing because your friends expect you to do it. Here the Tipping point -metaphor, Meme theory, Virus marketing and other related approaches may be very useful. Naturally getting converts will become easier when people have seen some major changes but then precious time has been lost.

  34. CobblyWorlds:

    The BBC have gathered a panel to consider climate change. The unanimity of agreement in some of their conclusions have surprised me (OK stunned me). See here: Perhaps we could be approaching a tipping point in public acceptance of this as an issue? I’ll put my inate cynicism on hold and cross my fingers. :)

    I suspect RC may have some comment on this to come, but thought posters/readers here might find it as interesting as I have. I do NOT want to spark off comments on this issue under this thread.


    CobblyWorlds, aka Chris Reed.

  35. Jeffrey Davis:

    It seems rather severe to think a catastrophe is 60 or 100 years in the future, but we only have 10 years to ensure that it won’t happen.

    A parachutist insures the soundness of his silk well before getting into the plane.

  36. Stormy:

    To the Editors of RealClimate

    Other than studies detailing anthropogenic forcings for present global warming, are there well-document, peer-reviewed, well-accepted studies showing that are other factors at work as well?

    [Response: Papers that look at the 20th Century tend to include all forcings – though not just anthropogenic ones (i.e. volcanoes and solar are included) – see Hansen et al for an individual assessment of almost all the forcings we can think of. Prior to that, the natural mechanisms are obviously more prominent. Going back to the mid Holocene and further, orbital forcings figure strongly. Did you have anything specifically in mind? – gavin]

  37. Nils Harder:

    Thanks for the article! It’s a bit better to read than some of the latest posts, since the technobabble has been reduced. Not that I’m not intested in the details, but it takes me some time when it’s becoming too flux-compensator-warp-core-like. I nevertheless dig through all of the more complex posts, since I can learn a lot from you guys. I usually find helpful references here to papers I can use in building up climate-related articles in the German-language Wikipedia. I don’t know if there are any German-speaking people here, but if you are, it would be great to see more of you working on articles like Globale Erwärmung (global warming) or my newest ambitions on Folgen der globalen Erwärmung (effects of global warming), and whatever climate-related article you can find. Don’t hesitate to get involved, it’s fun (or isn’t it, William!)

  38. Spencer Weart:

    A DANGER IN TALKING ABOUT TIPPING POINTS is shown in Paul Samuelson’s poorly thought-out opinion column (Washington Post 7/5, free registration)

    He argues that our knowledge and our political and economic systems make it impossible to “relieve global warming.” So we can do nothing… except pray for a magical deus ex machina (invention of free energy, geoengineering, whatever). Samuelson’s error is that he thinks climate change is an all-or-nothing matter. Talk of a tipping point, a point-of-no-return, etc. is only too likely to encourage this fallacy. It just doesn’t occur to him that there could be a range of policies, with a policy that keeps the temperature in 2100 only five degrees higher better than a policy that lets it get six degrees higher, etc. Hansen & others have shown that there are economically and politically feasible policies with current technology that will reduce the problem. And even if it is already too late to avoid some damage, the sooner we start the better.

  39. Alastair:

    Re 31 – IMHO, the reason that the Eemian was warmer was because the Arctic sea ice had melted, and so the amount of solar radiation absorbed in the northern hemisphere was greatly increased. The fact that the Greenland ice cores can only reach back as far as the Eemian shows that the Greenland ice may also have melted then too.

    As Gavin mentioned in his post, the Greenland ice is self sustaining, but so is the Arctic sea ice! When it disappears, we will have to lower global temperatures well below those of today to get it to reform.

    Gavin, you do not seem to have resolved the problem of what a tipping point is. Is it when the Arctic sea ice goes and we can’t get it back, or was it when the ice started to melt and made it inevitable that it would go?

  40. Jeffrey Davis:

    Re: 38

    Samuelson’s editorial seems to me to be either a counsel of despair or a stalking horse for the nuclear industry. By dismissing the moral aspects of continuing behavior that may lead to a disaster of global proportions, he minimizes one of our most potent sources of motivation: conscience. And he is simply wrong in saying that people won’t make sacrificies. People have accepted draconian change in the past once their leaders have shown an understanding of the dangers and made a committment to eqalitarian sacrifice. By dismissing the possibility of shared sacrifice, he’s attempting to rhetorically finesse away any objection to a nuclear solution.

  41. Brian Gordon:

    Re: 33: ‘Converting’ people:

    I entirely agree with this post. Someone suggested that we need an “environmental Winston Churchill”; someone with credibility who speaks well. Gore has little credibility with many because of US government and industry efforts to attack him (rather than the science) and the general willingness of ‘free’ Americans to reduce everything to a partisan issue. I also entirely believe that the time has come to stop arguing with ‘climate change skeptics’ and start doing things. I think we need a ‘Gandhi for the planet,’ or better, many of them. Climate change skeptics are irresponsible but powerful fools, and need to be treated as such.

    Think of it this way: as severe climate events happen and thus the evidence becomes unignorable, the majority of people will realise they’ve been duped. If we also happen to have passed some tipping points and PONR’s along the way, then how will those people react? The BBC article suggests that people may give up and live in the now, or despair and commit suicide. How about anger? Do you think anyone will be just a little upset, and perhaps may want to take out their anger on the world’s largest contributor both to climate change and to suppressing the truth about it?

    I find it fascinating that many fields are converging: the hard sciences, ethics, religion, social sciences, and so on. Climate change cannot be considered just a ‘science’ problem.

  42. Brian Gordon:

    PS – the BBC article stated that ‘experts convened by the BBC concludes [sic] that climate change is “real and severe”, but maybe not “catastrophic”,’ where Lovelock leaned toward the latter.

    What is “severe” climate change?

  43. David Goforth:

    If Al Gore’s movie, which was quite favourably reviewed here, is a possible ‘tipping point of no return’ on public awareness of climate change, perhaps someone with knowledge and credentials can comment on the inevitable negative feedback loop in public debate, e.g.,


  44. PHEaston:

    “Someone should come up with a name for this phenomena (sic)….”

    Its called ‘climbing on the bandwaggon’. The biggest threat to the case for AGW is ‘crying wolf’.

  45. Timothy:

    Re: T. Elifritz
    Due to the thermal inertia of the Greenaland and Antarctic ice sheets won’t it be several millenia before they could completly melt away even under conditions much hotter than now?

    [Response: Dynamics are as important as thermodynamics here. Recent evidence (e.g. as reviewed by us a few months back) suggests that the demise of large parts of the major ice sheets could potentially take place far faster–on timescales of perhaps several centuries–due to the influence of ice sheet dynamics. For example, crevices at the surface of the ice sheet are now known to sometimes penetrate all the way down to the bottom of the ice sheet forming channels (“moulins”) that allow surface meltwater to reach the bottom of the ice sheet, where it lubricates the ice, allowing it to stream into the ocean at velocities potentially far greater than once envisioned. These processes are still far from perfectly understood, because they require a representation of the fairly complicated rheology involved in ice sheet dynamics. But it appears far more likely that a better understanding of these processes will act to revised our estimates of ice sheet collapse timescales downward, rather than upward. – mike]

  46. DHelfrich:

    re: #38 I take heart in the Samuelson piece’s two concluding statements:

    “The trouble with the global warming debate is that it has become a moral crusade when it’s really an engineering problem. The inconvenient truth is that if we don’t solve the engineering problem, we’re helpless.”

    In his (lame) attempt to redefine the term “inconvenient truth” and dispossess Al Gore of it, he endorses the Gore stance that the issue is not partisan, but moral. And he steps up to the need to fix the threats to our climate or be lost–for Mr. Samualson at least, the “debate” is over. And finally, no publicity is bad publicity.

  47. pete best:

    So this is now where the climate debate is headed, towards the non linear dynamics of the earth system and whether they can magnify climate change to make it suddenly flip to a new state. these sub systems being

    The Amazon and other rainforests drying out
    The Siberian bogs (the size of germany, france and the UK combined) start to release methane in accelerating annual volumes
    Ice Albedo decreasing
    Ocean conveyor (thermohaline systems to some)weakening due to freshening of the seas

    And there are probably more sub systems that can feedback and potentially acelerate warming which accelerates the disturbance of the subsystem which accelerates overall warming.

    I would imagne that climate has been treated as a linear system since the early days of climate modelling until recently when observed changes are not being picked up by the simulations as much as was hoped and hence the real climate might be taking on a suprisingly rapid (non linear) warming that is yet to be accounted for in the models.

    Non linear dynamics and far from equilibrium thermodynamics of which the climate is one such system is a relatively young science and hence maybe as the parameters are pushed from the equilibium to the far from we may see what dynamicists call more interesting system behaviour Doom as people like Lovelock are predicting.

  48. Brian Gordon:

    What are the chances of natural, negative feedbacks kicking in at some point? An example of a positive feedback is Arctic sea ice melting, which exposes the ocean, which absorbs far more energy than the snow and ice did, causing the ocean to heat (or the air to cool?). Do similar negative feedbacks occur that tend to keep the climate in its current state?

  49. Mark Hadfield:

    The phrase “tipping point of no return” has now been used twice in this discussion, once in the title and again in comment 16. I sincerely hope this phrase never escapes into the wild and propagates, You wouldn’t want that on your conscience, now would you Gavin?

  50. Hank Roberts:

    >similar negative feedbacks
    That was the question that started Lovelock on his research decades ago. There’s a whole lot out there; one simple model is here:

    But if acidity goes too high in the oceans, the organisms that produce the sulfates that produce the clouds that cool the ocean could die off, and we’d lose a major feedback loop when most needed, one that’s been observed from space when it blooms: February, 2005, 16:31 GMT

    “Complex climate

    Dr Carol Turley, from Plymouth Marine Laboratories told this week’s Met Office and UK government-organised climate conference in Exeter she was very worried.

    Countless species, she said, depend on a relatively stable pH to extract calcium to build their shells or skeleton. These include shellfish, snails, starfish, sea urchins and some sea worms that play an important part in cycling minerals in the ocean mud.

    Tiny coccolithophorids form vast populations
    She is particularly concerned about the effects of acidification on plankton at the bottom of the fisheries food chain called coccolithophorids.

    These precipitate calcium to make tiny shells called liths. Each lith is only about 2.5 micrometres (millionths of a metre) across but when the algae bloom en masse the effects can be seen from space.

    Unpublished research from Norway suggests that increasing acidity harms the coccolithophorids. This might have consequences for fisheries. Scientists think coccolithophorids will probably be replaced if they drop out of the food chain but they cannot be sure.

    Coccolithophorids also play a role in climate change. The algae give off CO2 when they bloom and thus contribute to climate change. But they also produce dimethyl sulphide when they bloom which helps the formation of clouds which reflect back heat from the Sun. The science here is still in its early stages….
    —–End quote—-

  51. cwmagee:

    Related to the runaway tipping point of no return is the magic number of 2 degrees. It has been suggested that this is the limit of warming that we should aim for, in order to rein in the tippy runaways. What is the precision on this number, and where does it come from?

  52. Hank Roberts:


    By typing “two degree” into the Search box at the top of the home page, I found this quickly:

    In the main entry there you’ll find: “… Setting a limit to global warming at 2ºC above pre-industrial temperature is the official policy target of the European Union, and is probably a sensible limit in this sense. But, just like speed limits, it may be difficult to adhere to….”

    If you read a bit more you’ll find why; see the links in that thread.

  53. Mark Hadfield:

    Re 50 and the magic number of 2 degrees…

    As I understand it, this number is due to James Hansen and appears in a New York Review of Books article at

    Note that this is two degress *Fahrenheit*.

    Hansen justifies the figure there. He srgues out that the warmest interglacials in the last million years or so were about 2 degF warmer than today and that a larger warming, of around 5 degF, would lead eventually lead to the disnitegration of the ice sheets. But read it for yourself.

    I sincerely hope that the full phrase “runaway tipping point of no return” will never be used again. Doh, I’ve just done it!

    [Response: Hansen is talking about the change from today. The 2 deg C number comes from the Eurpoean Union and refers to the change from the pre-industrial. -gavin]

  54. Mark Hadfield:

    These thresholds are becoming confusing. Hansen’s use of 2 deg Fahrenheit is particularly unfortunate when a threshold of 2 deg Celsius has already been promulgated to the public.

    Re the 2 degC number, I have just been reading the Steering Committee Report from the Conference on Avoiding Dangerous Climate Change, Exeter Feb 2005:

    Here I read:

    “…a regional increase above present levels of 2.7 degC may be a threshold that triggers melting of the Greenland ice-cap”

    with the footnote that

    “This [regional 2.7 degC increase] would be associated with a global temperature rise of about 1.5 degC above present or about 2 degC above pre-industrial temperature”

    and then

    “In general, surveys of the literature suggest increasing damage if the globe warms about 1 to 3 degC above current levels. Serious risk of large scale, irreversible system disruption, such as reversal of the land carbon sink and possible destabilisation of the Antarctic ice sheets is more likely above 3 degC. Such levels are well within the range of climate change projections for the century.”

    Later they talk about options for “limiting climate change to 2 C above pre-industrial”.

    OK so they seem to have settled on 2 degC above pre-industrial as a useful policy target and they’re saying that 3 degC above present would be really bad.

    Is this the source of the 2 degC threshold or has it appeared elsewhere?

    And Hansen is saying we shouldn’t risk 2 degF (1.1 degC) above present, which is 1.8 degC above pre-industrial (assuming present minus pre-industrial is equal to the 20th Centrury warming of 0.7 degC)

    Like I said, these threshold are becoming confusing.

    Not that anyone’s going to take any notice of me, but I think it unwise to use pre-industrial global temperature as a baseline when the global-average surface temperature seems to have varied by several tenths of a degC during the half-millenium or so preceding the industrial era. On the other hand, pre-industrial CO2 was relatively stable and is a sensible baseline.

  55. Robert A. Rohde:

    As I noted way up in #21, the IPCC TAR picked a number of 2-3 C from 1990 as the level at which tipping points start to become a significant risk. However, one can cause significant damage to the environment even without reaching a tipping point, so the threshold at which climate change becomes subjectively dangerous may well be below this.

  56. S Molnar:

    As one who has taken Gavin to task on his English usage in the past (Gavin, people are trying to tell you that “phenomena” is plural. Pay attention.), I am obliged to confess admiration for his delightful pleonasm “runaway tipping points of no return” – I fully intend to plagiarize it. I am also charmed by his fanciful plural form “genii”, which is really the plural of “genius”, of course. Full marks.

    [Response: A little idiosyncracy in language should be allowed I think…. – gavin]

  57. Thomas Lee Elifritz:

    Surely at a CO2 rise of 2 to 3 ppm/y, and rising, we will go crashing through every so called ‘tipping’ point like there is no day after tomorrow. At that rate, I would be very surprised to have any of our descendents see any vestige of continental or polar ice in 1000 years. Clearly 1000 years of fossil fuel combustion defines the concept of unsustainability, considering that almost everyone on the planet is already observing the local macroscopic effects of climate change. I’m not real confident of Paul Hearty’s 30 foot line, but I can clearly see the seven foot line, and the 19 foot line (the two meter and six meter fluxes), etched into my back yard. I’ve got 18 feet, most of it is at or just above sea level (mean high tide) that’s all I’ve got, and we’ve been into beach erosion now for almost 10 years, whereas things have been fairly static previously since the 30’s. On the Wisconsin side, well, the change in the snow line is nothing less than stunning. Everything is rapidly shifting north, even the relatively uneducated country folk in my area can easily discern it with just casual observations.

    Everything points to a shock associated with the spike. We’ve got one more hurricane seasons until another election, three more until another president. Local observations indicate this is supposed to be an off year for hurricanes, so we shall see. When the house of cards we have constructed for ourselves falls, well, it’s all over.

  58. Steve Latham:

    From the original:
    “… if an initial change to a parameter is D, and the feedback results in an additional rD then the final change will be the sum of D+rD+r2D…etc. ). This series converges if |r|<1, and diverges (‘runs away’) otherwise. You can think of the Earth’s climate (unlike Venus’) as having an ‘r’ less than one.”

    But Venus’ climate has stabilized (“converged”, right?) — so really the Earth and Venus are similar (currently) in terms of this discussion because neither is currently running away. Correct?

    [Response: Point taken. I was implicitly thinking about the theoretical situation of two similar planets to Earth, one in Venus’s orbit, one here. – gavin]

    Re: 49 — I’m not worried about the meme “turning point of no return” — if it was so successful I think the Malaysians would already be saying it. A common Department of Redundancy Department phrase there is “another one more.”

  59. Alastair:

    Re 58 Steve, you are right to say that Venus has stabilised, and so is similar to the Earth.

    The stabilistaion of Venus is caused by the surfur dioxide clouds which formed when the surface became hot enough to vaporise the sulfur. The Earth’s climate is also stabilised by its albedo, viz. clouds and ice sheets. When the size of the ice sheets change, the climate becomes unstable until the cloud system has altered to compensate. Continental ice sheets change slowly because of their uneven relief, and their slow retreat due to great thickeness. Sea ice sheets change suddenly because of their even relief, thinness, and the forcing of the ice albedo effect. They cause rapid climate change.

    When the Arctic sea ice suddenly disppears the climate will warm until it settles into a new state where there is increased cloud to compensate for the loss of albedo from the sea ice. One would assume that this would be a climate like that of the Eemian, when tropical animals cavorted in London’s river Thames. But what was the climate like in the mid-west of the USA?

  60. Stephan Harrison:

    I think a much better phrase is “catastrophic runaway tipping points of no return” which is easily reduced to CRTPNR. Rather elegant I think.

  61. pete best:

    In the alarmist climate science book called “the last generation” linear climate change is labelled as Type I whilst the non linear type is labelled Type II. Apparantly the IPCC like type I more than Type II so as to not appear to alarmist in order to offend the climate skeptics.

  62. Simon Donner:

    Mass coral bleaching is a non-linear response to stress; an individual event could be thought of as pushing a coral ecosystem past a “tipping point”. Corals may bleach – a breakdown of the symbiosis between the reef-building animal and the microalgae in its tissue – when the seawater warms past a threshold (e.g. temperatures are ~1-2 deg C warmer than the usual annual maximum for a whole month). Bleaching events, however, are individual episodes. As the oceans warm, the concern is that the frequency of events will surpass the rate at which coral reef ecosystems can either adapt (to warmer temperatures) or recover (from bleaching events).

  63. Bruce Marshall:

    Re: #38, the Washington Post columnist in question is the conservative Robert Samuelson, not the great economist Paul Samuelson.

  64. Eric Swanson:

    – In discussing “tipping points”, the THC may be one of the most important. It’s worth noting that this year (2006) the sea-ice cover in the Greenland Sea was reduced considerably compared to that seen in recent decades. The so-called “Odden Ice Tongue” did not appear in January, February or March, as may be seen from these graphics depicting monthly extent derived from satellite images:

    One may select individual months and years for viewing. The purple curve outlines the median extent. The Odden Ice Tongue is the “hook” seen in this curve just to the west of Greenland and north of Iceland. This feature has been associated with deep convective events or “chimneys”, which have been seen in the Greenland Sea in past years. Whether there is a direct link between the deep convection and the Odden Ice Tongue is a question of great interest and study. Previous measurements of the Greenland Sea indicated that there was a near shutdown of deep convection exhibited there during the late 1970’s and early 1980’s. Recent studies have shown variation in this feature and there have been other years in which it did not prominently appear.

    J. C. Comiso, P. Wadhams, L. T. Pedersen, R. A. Gersten, Seasonal and interannual variability of the Odden ice tongue and a study of environmental effects JGR. 106, Number C5, 9093-9116, May 15, 2001.

    This apparent change in sea-ice may be part of a multi-year oscillation, such as the NAO, or it may be an indication that larger changes are underway. If the disappearance of the Odden Ice Tongue is evidence of a weakening or shutdown of the deep convection, this may be a cause for immediate worry.

  65. sidd:

    Re: 64 — the Odden ice tongue
    I cannot exactly tell from the picture in the link but it appears that the Odden ice hook forms north of the West Jan Mayen Ridge and Jan Mayen Island ? Can someone say if that is the case ? I ask because I notice that there is a hook in the 1000 fathom contour right about there.


  66. Lynn Vincentnathan:

    It’s not tipping points for the climate I’m worried about. (Does weather die or feel pain? Or do ice sheets & other inorganic matter?) It’s people, other biota, and ecosystems & their death/harm & collapse I’m more worried about (which this article does suggest as the more common realm of discussing tipping points).

    So, what I’d be intersted in is how many people will die from all effects of GW if the average temp increases 1, 2, 3, 4, 5, or 6 degrees. And I’m more interested in “runaway” in human terms than geological terms — the point at which nature takes over the warming via positive feedbacks, even if people reduce GHGs 50% or 80% or 100%. That is, runaway from any human control — not that we shouldn’t keep reducing so as to reduce the harms even if we do lose our ability to halt and/or reverse the warming.

    Then there are social tipping points — when the material world gets really bad, society may devolve into a chaos of each man for himself (skip the women & children), or rachet up to some totalitarian regime, or both. Why would the contrarians want to risk the very things they fear???

    As the article rightly points out, contrarians may take “tipping point” as something not to worry about until we get right up to it, or not to worry about because it’s too late & already reached. And since no one really knows when we’ll reach the real tipping points (no matter how you define them), then contrarians would argue that it’s best to continue business as usual, without any concern.

    Where there’s life, there’s hope, and we should never give up efforts to reduce our GHGs, regardless of whatever tipping point or point of no return we reach, or how far away or close those tipping points are, until we reach our own personal tipping point of death. I suggest this be motivated not by a STATE OF FEAR, but by a STATE OF LOVE.

  67. Vicki Lesley:

    Have been reading all the above comments with great interest. I am developing a documentary series based around the concept of tipping points in relation to climate change but am finding much of the information confusing/contradictory (no doubt some of this can be put down to lazy journalism but even amongst the climatologists I have been talking to there doesn’t seem to be much consensus).

    I have many questions and if any of you could spare the time to correspond with me via email I would be very grateful. In the meantime, could I just throw out one question which may seem a bit basic but which I am having trouble nailing.

    If we assume that there is some global tipping point that can be generally agreed on (perhaps 10-20 years in the future?), can we also assume that by bringing down carbon emissions to an agreed level, we can push this tipping point away into the future by a measurable amount (say to 50-60 years for example)? Or is it the case that we will either reach the tipping point, or avoid it?


    [Response: Interesting point. Essentially you are asking whether any such point might be related to the rate of warming rather than the absolute level of warming. For the ice sheets the answer is probably no (but experts on the subject might have a better idea), but for the overturning circulation or the ecosystem changes, the answer is probably yes – i.e. a slower rate of warming could lead to a different response (allowing time for ocean mixing to mitigate the effects, or adaptation of species to the new conditions). It would need to be a large slow down in the rate of warming though, I think, to make a significant difference (i.e. 20 years versus 10 years isn’t going to do it, but 100 years vs 10 years might). – gavin]

  68. wayne davidson:

    Its rather further back to the past, comparing present day climate with….:

    “The Eemian/Stage 5e period (about 120,000 years ago) when temperatures may have been a degree or so warmer than now but where sea level was 4 to 6m ”

    …… May be good, but should we be well versed with the climate further back in time, when CO2 concentrations were about 400 ppm, several million years ago I take it. When there was sub-tropical forest, still in exixtence today on Axel Heiberg Island 500 nm from the North Pole. It is likely to this climate we are returning towards, a brief world wide climate description of that time would be rather important.

  69. Eric Swanson:

    Re: #65

    Here’s some additional information on the Odden Ice Tongue, including some nice graphics.

  70. Gar Lipow:

    I want to thank you a lot for this thread. This is going to come up repeatedly; it is really to good to have it all in one place.

  71. Ike Solem:

    This was a great post on an important topic and I found it very helpful in thinking about these issues. Thanks! Especially for the discussion of ‘system return after perturbation’.

    Here’s another simple tipping point analogy –

    Put a pot of water on the burner, and wait for it to heat up -eventually, it reaches a ‘tipping point’ and starts to boil. It’s impossible to predict exactly where each bubble will form, however. This is somewhat analogous to the hurricane issue – there is a temperature threshold, and the hurricane tracks are chaotic. The ‘boils’ are also a dynamic effect which computer models of heated water pots might have missed – similar to ice sheet dynamics.

    Now drop in a fresh egg. It heats up, and at some point the egg proteins reach a ‘tipping point’ and denature(unfold), and you have yourself a hard-boiled egg. Now cool the whole system down. The bubbles disappear and the water returns to its initial state, but the egg proteins remain unfolded – now you have a cool hard-boiled egg. The two tipping points had different long-term effects. I’m unsure, but this seems analogous to the ice sheet issue – for example, under what climate regime would tropical high-altitude glaciers re-form? Are they best viewed as ice age remnants that wouldn’t form today (or yesterday)?

    RE#48 and #59: The long-term negative feedbacks are described by gavin in the first section; however the notion that increased water vapor leads to an increase in cloudiness and that this net effect is a negative feedback – this has been a topic of discussion for a very long time now, hasn’t it? However, a warmer atmosphere means less cloudiness even with more water vapor and then there are seasonal effects. I suppose this can only be addressed via high-resolution modelling – I’d hold off on notions of a tropical paradise in Britain. I searched RealClimate for cloud albedo and came up with these posts.

    I wish there was a RealEnergy site to go along with this one.

  72. Hank Roberts:

    >wish there was a RealEnergy site … along with this one

    Me too. Closest I’ve found, not associated with RC, is this:

    That site was recommended in comments here:
    where Tom Athanasiou and Paul Baer wrote:

    “… we prefer to stay in the reality-based world of those (the E.U., the Climate Action Network) who draw the line at 2ºC maximum …. the all-important Who Pays? question has to be answered …. We believe that, if climate mitigation is to be adequate, …. the rich in the South have to pay for real development (which is also fundamental to real climate adaptation), even as the rich in the already developed world pay for accelerated decarbonization…. This is, to be sure, not a realistic position, not in the short term, but there is more to this than short-term politics….”

    That seems to me the basic energy question, written before ocean acidification was found to be heading us toward a food chain collapse by 2100.

    Lovins perhaps would answer that the market pays, because efficient energy is cheaper. Maybe.

    Energy questions, economics questions, intertwingled.

  73. Grant:

    Re: #66

    Where there’s life, there’s hope, and we should never give up efforts to reduce our GHGs, regardless of whatever tipping point or point of no return we reach, or how far away or close those tipping points are, until we reach our own personal tipping point of death. I suggest this be motivated not by a STATE OF FEAR, but by a STATE OF LOVE.

    Not very “scientific,” but Lynn, I agree completely. Thanks

  74. Isaac Held:

    You briefly mention the disappearance of summertime Arctic sea ice as a potential candidate for a “tipping point”. What is the best evidence from GCMs or other kinds of models that there is hysteresis or multiple equilibria at this point? I have heard speculation over the years about the possibility of changes in oceanic statification creating strong nonlinearity, but where does this discussion stand?

    In the 1970’s work with very simple diffusive energy balance climate models focused on the “small icecap instability” as well as the “large icecap (snowball earth) instability”. If there is an ice-free climate that consistently produces a temperature at the pole that is greater than freezing, then putting an ice cube at the pole, even if the ice reflects all solar radiation, will not be stable, since the warm air will simply diffuse in from the sides. So ice covers smaller than a critical size are unstable, which produces hysteresis and multiple equilibria. The critical size is dependent on the diffusivity. You can google ‘small icecap instability” for some references. But this instability tends to disappear when there is a substantial seasonal cycle in the ice, even in these simple models. Does sea ice in comprehensive climate models produce hystersis at or near the point of zero summertime ice? (I am not implying that I think that the disappearance of summertime ice is not of great concern, nor do I think that the models are necessarily right, I am just curious as to what models are currently telling us about nonlinearity near this point.)

    [Response: Isaac, there are a couple of analyses making their way through the process that look at the IPCC AR4 model behaviour and see evidence for rapid transitions in the sea ice cover. I’m not aware of all the details though. – gavin]

  75. Paul Duignan:

    The current dialogue around climate sometimes seems to go like this:

    Public: What’s with this climate change, should I be worried?
    Climate Scientist: Well there’s a reasonable chance that if we don’t make serious changes that temperatures will rise by between 2-5 degrees late this century.
    Public: OK, well I suppose we need to start thinking about it some time soon, and as the temperature starts to track up that will motivate people to do something about it, so thanks for letting us know, keep in touch, I’ll let you know when I get some free time to concentrate on it.

    An alternative version fo the dialogue could be:

    Public: What’s with this climate change, should I be worried?
    Climate Scientist: Well, for a start we know that if we don’t make serious changes soon the chances are that the temperature will rise at least 2-5 degrees. But that’s only the start, we know that there are tipping points which, if triggered would push the temperature way beyond that. We don’t know when these might be triggered, we haven’t factored them into our estimate of a 2-5 degree rise. Worse still, we now have clear evidence that the assumptions in our models are wrong (for example how fast Greenland will melt) and we are seeing things happen much faster than we expected.
    Public: So you can’t give me any guarantee that we are not right on track to trigger tipping points within a matter of years?
    Climate Scientist: No I can’t, one of the reasons is that we are already committed to a significant temperature rise which is in the pipeline. So even if I told you that I could see a tipping point coming up in the future, there may be no way to stop us crossing it as the temperature rise in the pipeline plays out. Frankly I am extremely worried about this it is a very very dangerous situation for the world.
    Public: Right, who should I vote for, what do I turn off, where can I park up my SUV?

  76. S Molnar:

    Re RealEnergy, it would also be nice if there were a good introductory book on the subject to complement the recent slew of climate change books (Recommendations, anyone?). There’s a rumor that the estimable Gar Lipow, whose thoughts can be found here, on, and elsewhere, is working on one. I hope there is some truth to the rumor.

  77. Gar Lipow:

    The rumor is correct. Actually it is finished, and is a solicited submission to a publisher – so I am in hope of seeing it published.

  78. Ike Solem:

    As far as renewable energy science goes, the real problem is the lack of a scientific base of expertise in this country – ocean science departments, earth science institutes, meteorology departments – these are all very common. However, there are virtually no renewable energy research programs at any of the major research universities (people always seems surprised by this), and that’s because there is so little funding. There are people who do some research on the side, but it tends to be individual efforts, not ‘organized research units’. Then you have all the intellectual property issues to deal with as well – if you do come up with something useful, who ends up owning it? ExxonMobil has a 5-yr monopoly on any patents produced by Stanford’s Climate and Energy Project, for example.

    I do have a little personal insight into this issue. I received an MS in Ocean Sciences from the University of California, Santa Cruz a few years ago (in the area of marine nitrogen fluxes); at the time I was a recipient of an NSF Graduate Student Fellowship in microbiology – and I transferred into the Biochemistry department hoping to go into renewable energy research, which seemed to be very interesting, important and useful work – I was particularly interested in algal biochemistry (a great oil source) or fungal enzymes (for cellulose digestion) – but when I took these proposals to the Dean of Graduate Studies, he shook his head and said “You will never be able to find funding for this kind of work – can’t you do something else?” – no kidding (he was very nice about it). Compare the number of proprietary pharmaceutical research programs in this country to the number of renewable energy research programs, and you start wondering exactly what is going on. Look through course catalogs for renewable energy classes of any kind – generally, you find nothing. It’s a real travesty, and yet people seem largely unaware of this reality. Little funding means little research and development. If only this government would double NSF’s budget and create a renewable energy funding unit… but don’t hold your breath, they keep cutting the NREL budget while singing the praises of ‘switchgrass’ – unreal.

    There are a number of good renewable energy textbooks (mostly written by Germans or Australians, apparently) but very few publicly accessible books on renewable energy. One of the best is “From Space to Earth: The Story of Solar Electricity” by John Perlin, a fascinating historical treatment of the development of solar PV. You can also take a look at my personal favorite, (warning- 3.5 MB pdf file download) – the NREL Biodiesel from Algae program, killed off in 1997.

    (The Gelbspan link from #72 is interesting, (thanks) but it’s not a scientific discussion of renewable energy technologies, by any means).

  79. Mark Shapiro:

    Gar –

    Hope to see your book soon. Please let us know when it comes out!

  80. Fernando Magyar:

    RE 77:

    The NREL Biodiesel from Algae program, killed off in 1997

    Seems they really must have killed it because when I try to access the link this is what I get.

    Not Found
    The requested URL / was not found on this server.

  81. Barton Paul Levenson:

    Okay, I’ve written a planetary temperature calculator in javascript and uploaded it to my web site. It gives fair approximations of the temperatures of Venus, Earth and Mars (691 K, 288 K and 221 K versus the observed 735 K, 288 K, 214 K), and is a little oversensitive to CO2 and H2O changes (3.4 K increase on Earth with doubled CO2 and 10.2 K increase with doubled CO2 and H2O feedback — way too high compared to GCM results). But it has the basic physics more or less correct, in a qualitative way. I would have to make the model much more complex to get better accuracy, but I think this one illustrates some basic principles.


  82. Stormy:


    Thanks for the link. I was specifically interested in the Maunder Max/Min, which is one of the latest contra-arguments. The references in the paper were very helpful.

    As the general public latches on to each factor, that factor presumably overrides anthropogenic forcings. Not true, of course. Then I have to dig out the facts. Your site is a gold mine.

    Suggestion for the editors of RealClimate:

    Because economists are central to our dealing with GW and the environment in general, I would suggest dropping in on some of the major economic blogs when GW is an issue. And it is just starting to be an issue, a healthy sign.

    The Economic Roundtable gives a brief daily summary of all the major economic blogs. By looking there, you can see if your expertise would be useful. Quickly perusing this site once a week would be sufficient.

    I find your expertise informative and helpful. I would like key economists to have it as well.

  83. Mark A. York:

    Lomborg returns:

  84. Hank Roberts:

    >77, 80
    The NREL study PDF file is
    The link in 77 that looks the same has actually been mangled.

    (Practice SAFE TEXT: “copy link” — paste to a text* editor first, to see what you’re actually getting, instead of clicking. What you see is NOT what you get in HTML; typos and malware can be hidden in any editor that ‘interprets’ HTML. Eschew Microsoft Word for this purpose, use Notepad.)

  85. Eric Swanson:

    Re: #77

    Your comments on biomass production, particularly algal production as described in the NREL reference point to some big problems. Working in the lab to pick the best species out of thousands or manipulating selected species to improve production may not result in a workable system in the real world. As mentioned in work discribed on page 147, maintaining the proper culture in open ponds is difficult. Any monoculture is unstable and, given the many native species, keeping an algal system “pure” will be nearly impossible.

    Then, there’s the basic engineering problem. Building any pond system as described will require considerable material and effort to construct. If the energy produced is not large, the net return on the capital invested may be small or the production cost of the resulting fuel may be large relative to other energy sources. Economies of scale become difficult to imagine, as the construction of ever larger, gently sloped structures does not seem practical. One should think in terms of building 1,000 square meter parking lots as an example of the difficulty of controlling the flow with these large, shallow ponds. The ground below the ponds is not likely to be completely stable, especially after disturbance due to grading and pond construction. Then, there are the other problems of temperature and salinity maintenance and harvesting to add to the mix. What happens when it rains heavily over a short time period and lots of fresh water is added to the ponds? One implementation (page 162) involved an enclosed system, using a greenhouse type enclosure, which would be very expensive compared to open ponds. One reason what other types of solar systems have had difficulty competing against fossil energy sources is the cost of the material, be it glass, aluminum or plastic, which initially intercepts the solar energy. This becomes especially critical if the overall system has low overall energy conversion in real world operating situations. In sum, I think the engineering difficulties and costs involved would likely kill any large scale operation (see pages 245-247). Smaller scale operations for waste water purification may be a reasonable approach, as there is a secondary benefit to include in the calculations.

  86. Hank Roberts:

    Re 82 on the Economic Roundtable page —

    Alternative suggestion — could RC offer an ‘Economists’ link akin to the one you offer journalists? For journalists it’s “embargoed” stories.

    For economists — you could host a conversation for them, invited, with climate scientists. RC has the reputation to attract their interest. Doing it by invitation would cut the chaff.

    I did just peruse the Roundtable link — it does seem to do a good job of summarizing and linking out. Worth a look.

    For example, a link there to discussion of the July 5 Brooks NYT column, here: — discusses how fairness, equity and attachment are important but usually ignored by politicians, for instance. Climate change is one of those equity problems.

  87. Blair Dowden:

    Re #81: Barton, your calculator does not work properly in Firefox. When you press the buttons to pre-set the values, the numbers flash on, then disappear.

  88. Fernando Magyar:

    Re #85:

    I have just begun to read the study so possibly my opnion will change by the time I finish it. However this excerpt from page 18 seems to contradict your arguments even though your point about the laboratory strains not proving to be optimal in the open pond systems seems to be upheld. It seems that proof of concept was verified nontheless.

    “At the conclusion of the smaller scale tests conducted in California and Hawaii, the program engaged in a competitive bidding process to select a system design for scale up of algae mass culture. The HRP design evaluated at UC Berkeley was selected for scale-up. The â��Outdoor Test Facilityâ�� (OTF) was designed and built at the site of an abandoned water treatment plant in Roswell, New Mexico. From 1988 to 1990,1,000 square meter ponds were successfully operated at Roswell. This project demonstrated how to achieve very efficient (>90%) utilization of CO2 in large ponds.

    The best results were obtained using native species of algae that naturally took over in the ponds (as opposed to using laboratory cultures). The OTF also demonstrated production of high levels of oil in algae using both nitrogen and silica depletion strategies. While daily productivities did reach program target levels of 50 grams per square per day, overall productivity was much lower (around 10 grams per square meter per day) due to the number of cold temperature days encountered at this site.
    Nevertheless, the project established the proof-of-concept for large scale open pond operations. The facility was shut down in 1990, and has not been operated since.”

  89. Grant:

    Off topic I know, but I’m very curious…

    Why have nighttime temperatures warmed faster than daytime temperatures? It seems to me that the effect of greenhouse gases is strongest when *temperatures* are highest — during daytime — so the greenhouse warming would be strongest during the day. But I’ve looked at plenty of data, so I know that in fact nighttime temperatures have gone up faster than daytime temperatures.

    And a related question: why have wintertime temperatures warmed faster than summertime?

  90. Gar Lipow:

    In response to question – “why greater warming effects at night and in winter?”

    According to the Scientific American Blog:

    >”Greenhouse gases also have distinctive effects on the range of temperatures experienced by the surface. At night, the ground cools down by emitting infrared radiation, whereas during the day, the infrared cooling is secondary to solar heating. Because greenhouse gases impede the cooling but not the heating, they exert their greatest influence at night. If they are the cause of global warming, average nighttime temperatures should increase more than daytime ones — reducing the total daily temperature swing. (To be sure, the trend can be offset by changes in cloud cover and soil moisture.)”

    >”For the same reason, greenhouse gases affect wintertime temperatures more than summertime ones, reducing the total annual temperature swing, and high-latitude surface temperatures more than low-latitude ones. These effects are magnified by snow and ice: by reducing snow and ice cover, warming reduces the reflectivity of the ground and allows more solar energy to be absorbed, further increasing the warming; conversely for cooling.”

    I’ve also heard arguments that as global dimming is lowered this effect will be reduced.

  91. Grant:

    Re: #90

    I had seen the SciAm blog, but frankly, I wasn’t satisfied with that explanation. So I made a very crude computer model of diurnal heating and cooling, and when I increase the greenhouse effect the diurnal temperature range goes up.

    Any suggestions?

  92. Gar Lipow:

    Umm – I’d have to see your computer model. You have the words “very crude” bolded, but no link. Anyway your computer model depends on assumptions. I suspect there are some physics or engineering going on that the popularization I linked to does not go into. For that you will have to wait for actual scientists.

    I can take a guess – but it probably will not be right.

    I’m guessing that heat gets stored during the day. Because you have heat coming in less of it radiates out than at night when the air is cooler. (Smaller temperature differences result in smaller heat losses; the warmer daytime air acts as insulation – reducing additional flow of heat from thermal mass into the air; real engineers and scientists – is there where I start to go wrong?). At night you no longer have heat added. The air is cooler. So the heat stored in various types thermal mass gets radiated out faster. And of course since it is stored heat it is almost all radiated out in wavelengths that reflect back from greenhouse gases.

    Wothehell – if I’m wrong the real scientists can use this post as their straight-line when they get around to it.

  93. Steve Bloom:

    Re #60: Let’s go whole hog: “*abrupt* catastrophic runaway tipping points of no return” = ACRTPNR :)

  94. Hank Roberts:

    I’m thinking of a short form — “lemming points” — the precipices defined by a propensity for rushing blindly toward them, eh?

  95. Lynn Vincentnathan:

    RE #89, the (unscientific) way I figure it is the GHG blanket effect. Of course days are usually warming than night because of the sun, but if you keep a blanket on during the night & during winters, it keeps you fairly toasty….

  96. Grant:

    Re: #89 etc.

    Actually, it’s a mathematical model — I just used the computer to solve the differential eq.

    Input is solar energy, given by
    E(in) = S sin h,
    where S is solar constant * (1-albedo), h is solar altitude. This is given by
    sin h = cos d cos L cos(wt) + sin d sin L
    where d is the sun’s declination, L the observer’s latitude, w the (radian) frequency (= 2*pi /day), and t the time (in days). If the solar altitude is negative, then E(in) is set to zero. Output is blackbody radiation, given by
    E(out) = a T^4
    where a is a constant (emissivity * Stephan-Boltzman) and T is the temperature. Then I used
    dT/dt = const * (E(in) – E(out))
    I simulated greenhouse warming simply by lowering the constant “a”.

    There are a *lot* of oversimplifications here. Even so, when I lower the constant “a” the daytime peak temperature rises more than the nighttime low.

  97. Gar Lipow:

    >There are a *lot* of oversimplifications here. Even so, when I lower the constant “a” the daytime peak temperature rises more than the nighttime low.

    How about more than the nighttime *high* not *low*?

  98. Wacki:

    If Al Gore’s movie, which was quite favourably reviewed here…….

    Comment by David Goforth � 6 Jul 2006 @ 2:04 pm

    Gavin, you’ve known about this article for a while. You really need to do a piece on this or open up a forum so we can attempt to collectively tear it apart.

  99. Robert A. Rohde:

    Re #96: A meaningful greenhouse effect model really needs to have both the Earth and the atmosphere. The atmosphere is an enormous reservoir of energy that is maintained in large part by the ability of greenhouse gases to capture thermal radiation. It is so large in fact that averaging over 24 hours at a typical midlatitude site there is significantly more energy transfered from the atmosphere to the ground than there is transferred from the sun to the ground. See:

    I suspect that the problem you are having is that without the natural recycling effects of the interactions between the atmosphere and the Earth you are dissipating energy too rapidly during the night and hence cooling too rapidly. Keep in mind that since most of the radiation that makes it into space is emitted from the atmosphere, it is not merely a matter of adjusting the emissivity, but there is also an effective temperature, T_atmosphere, from where those emissions are eminating that can be substantially cooler than the surface.

  100. Hank Roberts:

    Night time:

    I searched here:

    and found this clue, which may lead you to an answer:

    “… “fingerprints” were found that pointed directly to greenhouse warming. One measure was the difference of temperature between night and day. Tyndall had pointed out more than a century back that basic physics declared that the greenhouse effect would act most effectively at night, as the gases impeded radiation from escaping into space. Statistics did show that it was especially at night that the world was warmer….”

  101. Pavel Chichikov:

    “It may also be that they just do not care what happens after they die.”

    A theist here, and a Roman Catholic, probably in a very small minority in this dicussion.

    I’ve been interested in the problem for years, and especially after having interviewed two scientists for a small Idaho paper on the subject of stratospheric ozone depletion in the arctic – one an atmospheric physicist and the other an atomospheric chemist.

    I sense that Rome is coming around to an awareness and concern in these matters, particularly as they affect the poor in the so-called undeveloped countries.

    I do know of individual Catholics who are concerned, and I’m thinking now of a field biologist who works in the sub-Arctic and who has done some notable work in insect infestation of sub-boreal forests.

  102. Grant:

    It seems that changes in the diurnal temperature range (DTR) are not so easy to attribute to a cause. Nor is DTR changing everywhere by the same amount, or even with the same *sign*.

    Some googlescholar search turned up very interesting things about DTR. I can’t seem to find the work by Tyndall (or anyone else) giving the reasons “basic physics” indicates greenhouse warming will decrease DTR. But one of the papers discussing the observed trends throughout the 20th century [Karl et al. 1984, J. Climate and Appl. Meteorology, 23, 1489] simply states that

    The physical mechanism responsible for the observed decrease in the diurnal range is not known.

    At least part of the change in DTR seems to be due to atmospheric absorption of solar energy, and by latent heat from increased evaporation [Cao et al. 1992, J. Climate, 5, 920]:

    atmospheric absorption by CO2 and water vapor increases, reducing the solar heating at the surface, and surface evaporation increases faster with temperature than the transfer of sensible heat (due to the Clausius-Clapeyron relation), both of which tend to reduce the diurnal cycle. However, in the three-dimensional model, the diurnal cycle increases substantially where the snow line recedes, where the land surface becomes drier, or where there are substantial decreases in cloud cover. The diurnal cycle of surface temperature decreases where sea ice is replaced by open water because of the increase in thermal inertia of the surface.

    Another important factor seems to be changes in cloud cover. This is from [Karl et al. 1993, Bull. Amer. Met. Soc., 74, 1007]

    The decrease in daily temperature range is partially related to increases in cloud cover. Furthermore, a large number of atmospheric and surface boundary conditions are shown to differentially affect the maximum and minimum temperature. Linkages of the observed changes in the diurnal temperature range to large-scale climate forcings, such as anthropogenic increases in sulfate aerosols, greenhouse gases, or biomass burning (smoke), remain tentative.

    And this from [Dai et al. 1999 J. Climate, 12, 2451]

    “Clouds, which largely determine the geographic patterns of DTR, greatly reduce DTR by sharply decreasing surface solar radiation while soil moisture decreases DTR by increasing daytime surface evaporative cooling. Clouds with low bases are most efficient in reducing the daytime maximum temperature and DTR mainly because they are very effective in reflecting the sunlight, while middle and high clouds have only moderate damping effects on DTR. The DTR reduction by clouds is largest in warm and dry seasons such as autumn over northern midlatitudes when latentheat release is limited by the soil moisture content. The net effects of clouds on the nighttime minimum temperature is small except in the winter high latitudes where the greenhouse warming effect of clouds exceeds their solar cooling effect.
    The historical records of DTR of the twentieth century covary inversely with cloud cover and precipitation on interannual to multidecadal timescales over the United States, Australia, midlatitude Canada, and former U.S.S.R., and up to 80% of the DTR variance can be explained by the cloud and precipitation records. Given the strong damping effect of clouds on the daytime maximum temperature and DTR, the well-established worldwide asymmetric trends of the daytime and nighttime temperatures and the DTR decreases during the last 4â??5 decades are consistent with the reported increasing trends in cloud cover and precipitation over many land areas and support the notion that the hydrologic cycle has intensified.”

    Yet another factor is changes in land use/land cover (LULC) [Gallo et al. 1996, J. Climate, 9, 2941]

    The results also suggest that changes in the predominant LULC (land use/land cover) conditions, within as great as a 10000 m radius of an observation station, could significantly influence the climatological DTR.”

    While not relevant to the cause of changes in DTR, the most interesting thing I found was this [Forster and Solomon 2003, PNAS, 100, 11225]

    Using surface measurements of maximum and minimum temperatures from the Global Daily Climatological Network data set, we find evidence of a weekly cycle in diurnal temperature range (DTR) for many stations in the United States, Mexico, Japan, and China. The â??â??weekend effect,â??â?? which we define as the average DTR for Saturday through Monday minus the average DTR for Wednesday through Friday, can be as large as 0.5 K, similar to the magnitude of observed long-term trends in DTR. This weekend effect has a distinct large-scale pattern that has changed only slightly over time, but its sign is not the same in all locations. The station procedures and the statistical robustness of both the individual station data and the patterns of DTR differences are thoroughly examined. We conclude that the weekend effect is a real short time scale and large spatial scale geophysical phenomenon, which is necessarily human in origin. We thus provide strong evidence of an anthropogenic link to DTR, an important climate indicator. Several possible anthropogenic mechanisms are discussed; we speculate that aerosol-cloud interactions are the most likely cause of this weekend effect, but we do not rule out others.

    The one thing that seems to be clear is: the simple explanation given in the Scientific American blog is not correct (or at the very least, far from the whole story).

    To the moderators: I think this might be a great topic for a post. Or, it could be part of a larger topic on “fingerprints” of AGW, and the root physical mechanisms behind them.

    Now … about that change in *annual* temperature range…

  103. Wacki:

    Paul, if the Vatican is starting to come around on the whole global warming debate please post evidence either here or your website. I don’t care how trivial. I’m extremely interested in this subject.

    Also, it’s good to see you here. We need more *openly* theistical posters here to show the proudly “godless liberals” that religion isn’t as bad as they make it out to be. It seems like it’s becoming harder and harder to say that lately due to the anti-evolution movement and the “war on science”.

  104. Hank Roberts:


    In the 1860’s, Tyndall began to suggest that slight changes in the atmospheric composition could bring about climatic variations. He was exploring radiation passing through the atmosphere and noted that,

    “The waves of heat speed from our earth through our atmosphere towards space. These waves dash in their passage against the atoms of oxygen and nitrogen, and against molecules of aqueous vapour. Thinly scattered as these latter are, we might naturally think of them meanly as barriers to the waves of heat.”

    Tyndall’s main interest was with water vapour and its impact on radiation, but he also dealt with the radiative forcing of other greenhouse gases including carbon dioxide. Most importantly he identified that there was a greenhouse effect, whether natural or anthropogenic. For water vapour he noted that:

    “â�¦this aqueous vapour is a blanket more necessary to the vegetable life of England than clothing is to man. Remove for a single summer night the aqueous vapour from the air that overspreads this country, and you would assuredly destroy every plant capable of being destroyed by a freezing temperature. The warmth of our fields and gardens would pour itself unrequited into space, and the sun would rise upon an island held fast in the iron grip of frost â�¦ its presence would check the earth’s loss; its absence without sensibly altering the transparency of the air, would open wide a door for the escape of the earth’s heat into infinitude.”

  105. Hank Roberts:


    Weekend Effect in Diurnal Temperature Range in China: Opposite Signals Between Winter and Summer
    “… Since the late 1970s, the weekend effect has been enhanced in both winter and summer, concurrent with rapid development and enhanced human activity in China. The direct and indirect effects of human-related aerosols on radiation, cloud, precipitation, and so on, might play an important role in generating the opposite signal in the weekend effect for different seasons. During a dry winter, the reduction of aerosol concentrations in weekend days may overwhelmingly impact on the DTR through a direct effect, i.e. by increasing total solar irradiance near the surface and raising the daytime temperature and maximum temperature, and lowering relative humidity. By contrast, in summer the indirect effect of aerosols, i.e., reduction in precipitation efficiency caused by more numerous and smaller cloud droplets, would largely be responsible for the increased numbers of rainy days, the reduction of the total solar irradiance, and the lowering of the maximum temperature and DTR.”

  106. Hank Roberts:

    This seems relevant to sudden change because a major recession or sudden decrease in air pollution would remove a lot of particulates and we’d feel the full effect of climate change masked by aerosols.

    One of the earlier publications, from 2003.:

    “… We knew about a weekly cycle in pollution and wanted to learn how this altered clouds. Rather than look directly for changes in cloud cover we examined the better quality records of the daily temperature range. As clouds keep the daytime cooler and the night-time warmer, the daily temperature range is smaller under cloudy skies. We found temperatures were up to 0.5°C different at the weekends over much of North America, China and Japan. This difference is as large as that seen in the last 100 years of global warming.

    “But as we expected to see a greater daily temperature range at the weekend due to less cloud-forming pollution, we were surprised. Over Japan and the US Midwest the effect was the opposite, weekends had a smaller daily temperature range, implying more cloud. And over Europe we found no effect at all!

    “…. we have theories. While pollution in some areas provides nuclei for water to condense on to form clouds, in other places there may be soot particles, which could absorb sunlight and cause the cloud to burn off (evaporate) during the day, leaving less cloud to warm the night. Another possibility might be that pollutants could cause changes in wind circulation patterns on a weekly basis. Or there may be a gradual change across the country because of the downwind transport of pollutants. And we canâ��t rule out the possibility there is some other human-related mechanism at work other than pollution changing clouds.”

  107. Pavel Chichikov:

    “Paul, if the Vatican is starting to come around on the whole global warming debate please post evidence either here or your website. I don’t care how trivial. I’m extremely interested in this subject.”

    First off, I’m just a layman and nothing I say is in the least authoritative for the Church. Authoritative statements for the Church as a whole come out of Rome from the Pope or from an important office.

    If you ever hear of a monsignor or a bishop making pronouncements about climate change, that is only his opinion.

    I would not use the phrase ‘coming around’, only perhaps that the Church is becoming aware of the problem of climate change. It has pastoral and humanitarian responsibilities. Insofar as climate change affects these, it must take notice of it.

    See for example, this below, especially the fourth paragraph on and references to the Pope’s position on the environment.

    As for intelligent design, the link below seems to represent adequately a Catholic position.

    I agree that ID is not scientific and should not be taught as science. That doesn’t necessarily make it wrong.

  108. Hank Roberts:

    >89, 90, 91, 102 etc.
    Grant, is it clear that you’re looking at variation in nighttime temperature records due to two very different causes? You need to sort them out if you’re questioning how that variation is explained and whether it proves anything about the greenhouse effect predictions.

    1) The fundamental ‘greenhouse effect’ basic physics that Tyndall describes as quoted above from a century ago — some gases, including water vapor and carbon dioxide, are transparent in the human visual range, but are not transparent to a range of infrared. In the atmosphere these gases act like a blanket trapping heat, and the effect is prominent at nighttime because that’s when the sky is dark and more heat can radiate away into space. In earlier threads there was discussion of how to show this at the high school science fair level.

    2) The effects of clouds and aerosols on radiative heat transfer, which are many and varied and still being studied with many questions open.

    Hold the variations in aerosols and clouds constant, and you’ll see the greenhouse gas effect.

  109. Barton Paul Levenson:

    Re #87 — Blair is right, the calculator doesn’t work properly as seen in Firefox. I’m not quite sure how to fix this. It works in IE, and I haven’t tried Netscape or Opera.


  110. Hank Roberts:

    Firefox OSX workaround:
    Pick planet; after input numbers blink, page-back (left-arrow)
    Numbers reappear. Change them if desired.
    Click Calculate; after result numbers blink, page-back
    Results reappear.

    No promise from me that these reappearing numbers are correct or resemble those the page is supposed to produce, haven’t taken the time to check anything.


    re: 37
    Nils, the German Wikipedia “Folgen der Globalen Erwaermung” entry is quite ambitious and very well done.
    And yes, although not a climatologist practitioner, I can read it with considerable profit . The accompanying graphics included are also very timely and helpful.

    thank you on behalf of German speaking ( and reading) everywhere, for the considerable labor of completing this, including all the sublinks by topic name that follow the main entry . I have friends I will be sending this discussion to.

    ed lanwermeyer

  112. S Molnar:

    Re #110: Same problem in Opera as in Firefox, and same workaround. Also, same disclaimer, but earth works out correctly. Of course, the other workaround is just to use IE – I hate it as much as the next guy, but Opera users always need a backup since so many websites don’t work properly in Opera (not the fault of the Norwegians, I hasten to add).

  113. Blair Dowden:

    Barton, I tried to follow your calculation of planetary temperatures on your web site. I am afraid I lost you at equation <3>. I have no idea where the value Tau (“gray optical thickness”) comes from, and I do not understand the four cooling processes, or even what some of them mean. For example, how is absorption of radiation in the atmosphere or evaporation of seawater a cooling process?

    Perhaps some further explanation would help.

  114. George A. Gonzalez:

    It is when considering tipping points that geoengineering responses to climate change appear central to preventing at least some of the worst outcomes of climate change. It is important to stress that the CO2 400 ppm atmospheric threshold is dangerous to cross because it will cause the mean global temperature to rise 2 degrees Celsius. So it is the 2 degree Celsius increase that must be avoided. This can be done so through geoengineering (e.g., aerosols in the stratosphere or mirrors in space). Even at 380 ppm the current biosphere stability in the long-term may be unviable. It is currently maintained by sulphate emissions from coal burning power plants. These emissions are in the atmosphere only a few years. It would appear vital to plan to replace the cooling affects of these sulphate emissions.

  115. Hank Roberts:

    That seems the clearest statement yet of the real problem == is there anything that can replace current levels of air pollution, if high sulfur coal and oil are phased out for respiratory health reasons, that would make up for the loss of the aerosols’ negative forcing on global temperature?

    I’d think arguing over volatiles a smokescreeh to divert attention from CO2 problems, notably now ocean acidification?

  116. Vincenze:

    More around social tipping points than a scientific ones (though the first tipping point is science)… the Climate Institute Australia released their report “The Top Ten Tipping Points on Climate Change” the other day and I’ve written about it in this article…

    May be relevant to you folk.



  117. Barton Paul Levenson:

    ##Barton, I tried to follow your calculation of planetary temperatures on your web site. I am afraid I lost you at equation <3>. I have no idea where the value Tau (“gray optical thickness”) comes from, and I do not understand the four cooling processes, or even what some of them mean. For example, how is absorption of radiation in the atmosphere or evaporation of seawater a cooling process?

    Perhaps some further explanation would help.##

    Radiation absorbed in the atmosphere doesn’t make it to the ground. Evaporation of seawater cools the surface and warms the atmosphere.

    Optical thickness (optical depth, optical path) is a fundamental quantity in radiation physics. It has to do with the reduction in strength of a beam of radiation going through a physical medium. Tau is 1 for a situation where the strength of the beam has decreased by a factor of e (2.718…). The higher tau is, the greater the absorption, all else being equal.

    You’re probably right that I should have explained more of the background. I’ll have to see about revising the paper. Thanks for checking it out for me.


  118. Brian Gordon:

    Re: #85: alternative energy possibilities

    I often see arguments against alternative energies that boil down to this: When something as efficient, inexpensive, and convenient as oil comes along, we’ll take it seriously. However, this is a silly point of view, really:

    New energy sources will take time, money, and energy to discover, develop, and make efficient; they won’t just magically appear complete with all the same characteristics as oil (eg, suitable for use in internal combustion engines) and with the existing zillion-dollar oil infrastructure. This latter ranges from massive oil sands projects to transportation to refining to distribution. It also includes a heck of a lot of engineers and scientists researching and developing in companies and taxpayer-funded organisations, and how about the military subsidy…? We have spent literally trillions of dollars building infrastructure based on cheap oil; how much have we spent similarly supporting sustainable energy sources, or that unAmerican ideal: conservation.

    There is no guarantee that we will be able to continue our existing oil-based economy/infrastructure/lifestyle. The longer we wait, the less likely we’ll have the time, energy, and social stability to find alternatives. Every dollar currently spent on oil and coal research and development is being poured into obsolete, dangerous technology.

  119. Lynn Vincentnathan:

    RE # 101, 103, 107, there are great statements about GW at the top of the Catholic hierarchy. The U.S. Bishops made a very good statement in 2001(link below) & are working on a GW packet for parishes, and Pope John Paul II as early as 1990 stated:

    “Today the ecological crisis has assumed such proportions as to be the responsibility of everyone…The…’greenhouse effect’ has now reached crisis proportions…â?? from “Peace with All Creation,” see

    However, there is not much action at the local level. My priest won’t bring up GW because he’s afraid of the “Rush Limbaugh parishioners.” So lots of talk, no walk.

    I would appreciate it if some scientist on this site could read the U.S. Bishops’ statement, “Global Climate Change” (2001, at
    ), and discuss their use of science. My own understanding is that they are too conservative & assume the GW problems are only in the future. (You can hear in dialogic fashion apologetics to skeptics.) My idea is that we’ve already been beset with GW problems (increases due to GW in droughts, floods, storms, heat deaths, disease spread, etc) perhaps for several decades, and that as science improves it will find these past & present harms to be more & more certain.

    3. My own “Little Way of Environmental Healing” (brief summary) at

  120. Dan Robinson:

    A month or so ago in a related blog, before I was called away on other business, I asked if the earth could be pushed into a “Venus syndrome” of permanent runaway greenhouse. (I continue to fall behind in the ongoing discussion.) I accept the figures from “Lessons from Venus” that indicate “… the amount of CO2 we could add to the atmosphere by burning all available fossil fuel reserves would not move us significantly closer to the [Venus level] runaway greenhouse threshold”. Can we assume that burning most of the available surface carbon resources, in stoves, boilers and increasing wildfires also wouldn’t make a significant difference?

    But to imply simply “no runaway greenhouse” is another matter. I think there are several possible levels of this. Maybe the most pertinent is where our excessive burning of carbon triggers self-reinforcing natural forces beyond our control, with little knowlege of what will turn them around. Can anyone guess how this could evolve, say through this millenium?

    It seems we’ve been in a slowly developing runaway greenhouse since life began. We’ve evolved basically as individuals on various levels, with individual selfish interests. Individuals and local communities have in the past been controlled by natural laws of checks and balances. But the very “natural”, not truly human, and therefore blind, goal of “directing a stream of ‘negentropy’ upon ourselves” (John Dobson) has now gone global, beyond such laws.

  121. George A. Gonzalez:

    re: #115

    I do not see how discussing the prevention of a global mean temperature rise of 2 degrees Celsius is a smokescreen for anything. If this occurs, it would likely mean the end of life on the earth as we know it. On the issue of ocean acidification, a 2 degree Celsius increase would probably push CO2 to 750 ppm in the atmosphere. What would happen to the ocean’s pH balance then?

    Respectfully yours,

  122. Pavel Chichikov:

    Re: #119

    “RE # 101, 103, 107, there are great statements about GW at the top of the Catholic hierarchy. The U.S. Bishops made a very good statement in 2001(link below) & are working on a GW packet for parishes, and Pope John Paul II as early as 1990 stated:”

    “Today the ecological crisis has assumed such proportions as to be the responsibility of everyone…The…’greenhouse effect’ has now reached crisis proportions…â?? from “Peace with All Creation,” see

    I was aware of the USCCB statements but not of The Catholic Conservation Center, so thanks Lynn.

    There is a very vocal faction in Catholicism which is anti-environmentalist and takes its positions from Chrichton, Lomborg and “Professor” Limbaugh. The size of the faction is another matter, probably not very large.

    In respect to the environment, I believe that the Catholic at large is very much in the same place as the public at large. Atmospheric carbon uptake seems very far removed from the daily problems of earning a living, surviving the daily commute and the boss’s moods, and paying for the kids’ school tuition.

    I believe that there is an underlying issue, though. Many devout Catholics have the impression, not entirely unfounded, that many if not most physical scientists are deep in the bone reductionists who hold religious faith in contempt.

    The devout are not faithful, for the most part, because they read about God in a book, or have never got beyond a slavish innocent reliance on what their elders told them, but out of deep life experience.

    To be frank, they believe most scientists to be not only contemptuous of them, but blind.

    For that reason, I read with interest about a letter sent by physicist Lawrence Krauss to the Pope. It has weaknesses, but it’s a start, anyway:

  123. pete best:

    This discussion on tipping points seems to assume on realclimate’s stance on them is that tipping points are not likely to happen? The fact that polar ice is disappearing faster than predicted from the models along with permafrost decline and more besides seem to indicate to many climate scientists (who incidently appear profously in the Fred Pearce book – the last generation) that human induced climate change is happenning faster than can be explained by the primarily linear models.

    If the lay scientist is being fed too much ITS REALLY URGENT – WE MUST DO SOMETHING NOW rhetoric from scientific journalists does that means that the scientists are feeding to them or people are exaggerating to sell books. Climate Science seem to deny any evidence of major far from equilibrium effects citing that all that is being observed is as predicted, which other sources say is not true.

    This is troubling me somewhat

  124. pete best:

    Re #121

    the oceans appear to already be increasing their acidity

  125. Stephen Berg:

    A paper just published in Journal of Climate has an interesting graphic on p. 3059. It shows the causes of climatic warming over the 20th Century and indicates that anthropogenic sources are the primary reason.

    Stott, P.A.; Mitchell, J.F.B.; Allen, M.R.; Delworth, T.L.; Gregory, J.M.; Meehl, G.A.; and Santer, B.D. (2006) ‘Observational Constraints on Past Attributable Warming and Predictions of Future Global Warming’ Journal of Climate 19(13) 3055â??3069.

  126. Hank Roberts:

    George, my point was that it’s missing the point to be planning for replacing sulfates in the stratosphere while controlling sulfate air pollution at ground level. The real issue as you note is reducing carbon dioxide.

    The already difficult target — 2 degrees above preindustrial level —

    doesn’t include ocean acidification as an issue. I hope we’ll be seeing models and targets that include changes — and rates of change — in ocean pH.

    I’d bet — but it’s a hunch only at this point — that the rate of acidification is more urgent and will require more control and faster than we thought we’d need. I hope the hosts here can bring in some of the researchers to talk about rates and rate of change and consequences, to inform that guess.

  127. Brian Gordon:

    Re: 123: When and where, exactly, are the tipping points?

    My impression, from reading numerous RC and other sources (like the BBC), is that:

    1. Scientists like to have solid evidence to back up their assertions.
    2. The evidence on when and where various tipping points will happen, and their subsequent effects, is not yet solid.
    3. Therefore, scientists are not willing to say that we have passed a particular point.

    This may change as we understand more about the climate system. It may also mean that we’re flying by tipping points (or are committed to doing so) and just don’t have the evidence to know so.

  128. Mark Shapiro:

    This is somewhat OT, but RC has done a couple articles on the thermohaline circulation, fortunately concluding that we don’t have to worry about a tipping point there.

    I just saw an article in American Scientist Online by Richard Seager explaining why the THC is not so critical to Europe’s climate. The main thrust is that Europe has a maritime climate rather than a continental climate. The case seemed clear and reasonable to me. It is at:

    Any other opinions?

  129. Joseph O'Sullivan:

    This was an excellent explanation of the concept of tipping points. I think that in the popular press at least there is a confusion of tipping point with time lags.

    When the scientific community states that we are already locked into climate change in the near future because of the pollution we have already emitted, it is a logical conclusion to the idea of a “point of no return” or “tipping point”. The complications and subtlety that provide a more accurate explanation are lost.

    Ecosystems do provide examples of tipping points. Gavin’s paragraph on this was very informative. There has been work by scientists that indicates that are tipping points in ecosystems that have been crossed due to human activities.
    Pauley and other marine biologists have shown that drastically reduced populations in marine fishes caused by overfishing may never recover because overfishing has created irreversible changes in ecosystem structure.

    #124 (Pete Best) 121 (George Gonzalez)
    There is a new synthesis report on the impacts of anthropogenic ocean acidification on marine life.

  130. S Molnar:

    Re #128: A related paper by Seager was discussed in a comment and reply on a previous thread:

    Or, for you tinyURL fans out there:

    RealClimate has such a wealth of information – too much for me to keep straight – that I find the search window at the top of the page indispensable.

  131. Mark Shapiro:

    S Molnar –

    Thanks for the refs. The comments & replies are great.

  132. George A. Gonzalez:

    re: # 124, 126 and 129


  133. Blair Dowden:

    Re #117: Barton, I have wanted to do the same kind of calculation you have done, and I appreciate your effort. But I have to disagree with some of what you have done.

    A simple radiation balance model only needs incoming solar energy and albedo. It makes no difference where the energy is distributed between the land, ocean and atmosphere. The existance of an ocean does not matter, as albedo and water vapor are already taken care of. Of course, Gavin and the boys may take a different view about all this, but their models are rather more complex.

    Optical thickness has nothing to do with the greenhouse effect. It can be approximated by a logarithmic (or even square root, as you have done) relationship. The only figure I have is 3.7 watts per square meter for each doubling, but I don’t know how to seed this to start with. This will not work for Venus, because at high concentrations arbon dioxide absorption bands expand with increased atmospheric pressure (collisional broadening) and higher temperatures (doppler broadening) [according to Raypierre.]

    Your gray gas is fine, but maybe you should keep it that way instead of distinguishing between water vapor and carbon dioxide. The calculation will show that about 99% of the greenhouse effect on Earth is from water vapor. Even the craziest skeptics only claim 95%, probably because they think that is the highest figure they can get away with. It does not take into account the vertical structure of the atmosphere, which is way too hard. Maybe it is best to treat them as the same gas.

    But you want to handle water vapor feedback, which would be nice. I don’t know how to do this (ie. what is the increase in water vapor for every degree C), but maybe you could just hack in the known ratio that 65% of the greenhouse effect is water vapor. That would spoil the purity.

    I don’t know if this helps, or just confuses. I would love to see a working model I can believe in.

  134. Blair Dowden:

    Re #121: George, a 2 degree C temperature rise would not “mean the end of life on the earth as we know it.” The Earth was about 3 degrees warmer for several million years during the Pliocene, between 2 and 6 million years ago, and life did quite well, perhaps better than today. Now, a quick transition to that climate could be rather disruptive to our already overpopulated human species, and it should be noted that sea levels were 25 meters higher during that time. This is not something we should want to do, but neither is it the end of the world.

    About ocean acidification. This has nothing to do with temperature, or even carbon dioxide levels, both of which have been much higher in the past and the ocean did fine. The problem is the rate of increase of carbon dioxide levels, because the ocean does not have time to transfer it from the surface to the deep ocean. The faster carbon dioxide levels rise, the worse the problem will be. This is not just speculation or modeling, because there was an interval of rapid carbon dioxide rise about 55 million years ago, known as the Paleocene Eocene Thermal Maximum, for which there is evidence of a large dying of calcium carbonate shelled organisms. So it is something to take seriously.

  135. George A. Gonzalez:

    re #134

    The problem with a 2 degree C increase in global temperature does not lie with the rise in temperature itself, but with the fact that such a rise in temperature will engage positive feedbacks (e.g., the massive die off of the rainforest). This will release more CO2 into the atmosphere than emitted throughout the 20th century (in a shorter space of time). As a result, CO2 atmospheric levels will be pushed to 750 ppm. Thus, a 2 degree C rise in global mean temperature will cause a dramatic and relatively sudden global mean temperature increase.

  136. Hank Roberts:

    I’m waiting on the ocean chemists to tell us if primary production will drop off before we can burn that much coal — remember where our oxygen comes from!

    Melting the Arctic sea ice could hit hard at ocean biology, as will acidification. Here’s a decent summary page:

    ‘… The halocline is far more important in polar waters in producing water column stratification. Melting of sea ice places a lens of fresh water on top of salt water, creating a very stable water column that lends itself to some of the most intense phytoplankton blooms experienced on the planet.”

    “… Once more, I want to emphasize (read–pound into your head), the importance of physical processes … and chemical processes … in determining biological processes (spring and all phytoplankton blooms, switching from a “classical” food web to a microbial food web, deepening of the chlorophyll maximum, etc.). Remember that all of the energy and matter that fuels oceanic food webs comes from the phytoplankton, who use sunlight to create living matter from inorganic elements.”

    That’s snipped from a good illustrated page, recommended reading.

    If we lose the, what, 30 percent? of the oxygen that’s currently being put into the atmosphere by ocean organisms, we may not manage to burn all that coal that fast.
    “Gross oxygen production (GOP) is a fundamental but poorly known characteristic of planktonic marine ecosystem especially with reference to climate change.”

  137. C. W. Magee:

    Re: 120.
    I think the projected incease in solar luminosity means that Earth will have a runaway venus-style climate eventually. But “eventually” is something like a billion years in the future. And changes in CO2 will not significantly effect this event.

  138. Blair Dowden:

    Re #135: George, your reasoning is circular. The projected 2 or 3 degree rise in global average temperature already includes feedbacks. I see no reason why tropical rainforests will die when paleoclimate data tells us that they covered more area in the time when temperatures where higher than today. The problems with a rapid temperature rise are serious, and we should do what we can to avoid this happening, but I think you are overstating the problem.

    If we want to convice people to reduce carbon dioxide production, we need to be credible. That means not making claims that are not based on the scientific knowledge that we have.

  139. D_WillRobinson:

    The very term, “Climate Change is the work of Republican spin doctor, Frank Luntz, who contends, “‘Climate change’ is less frightening than ‘global warming.’ … While global warming has catastrophic connotations attached to it, climate change suggests a more controllable and less emotional challenge.”

    You can read further on Luntz’s fine evil work here.

  140. Barton Paul Levenson:

    [[Re #117: Barton, I have wanted to do the same kind of calculation you have done, and I appreciate your effort. But I have to disagree with some of what you have done.

    A simple radiation balance model only needs incoming solar energy and albedo. It makes no difference where the energy is distributed between the land, ocean and atmosphere. The existance of an ocean does not matter, as albedo and water vapor are already taken care of. Of course, Gavin and the boys may take a different view about all this, but their models are rather more complex.]]

    ANYBODY’S model is going to be more complex. You’re talking about estimating the Earth’s effective or emission temperature, which, due to the presence of an atmosphere, is usually going to be considerably less than the SURFACE temperature.

    [[Optical thickness has nothing to do with the greenhouse effect.]]

    If you’ll forgive me, this is an unbelievably ignorant statement. See if you can get ahold of a copy of John Houghton’s “The Physics of Atmospheres” (the most recent edition is 2002, I think) or K.N. Liou’s “Introduction to Atmospheric Radiation.” The greater the infrared optical thickness of an atmosphere, the hotter the surface will be COMPARED TO THE EFFECTIVE TEMPERATURE.

    [[The calculation will show that about 99% of the greenhouse effect on Earth is from water vapor]]

    Not true. This has been covered in RealClimate before. CO2 accounts for about a quarter of the effect, not 1%.

    There’s no reason you should like my model in particular, but many, many gray greenhouse models exist out there for you to research if you’re interested. Michael Hart came up with a nice iterative one in 1978 (“The Evolution of the Atmosphere of the Earth,” Icarus 33:23-39. Walker et al. came up with a very different one in 1981 (Walker, J.C.G., P.B. Hays, and J.F. Kasting. “A Negative Feedback Mechanism for the Long-term Stabilization of Earth’s Surface Temperature.” J. Geophys. Res. 86(C10):9776-9782). McKay and Davis have come up with several using Mars as a test case, see, for instance, C. McKay and W. Davis, “Duration of Liquid Water Habitats on Early Mars,” Icarus, 90:214-221, 1991. Some of these, e.g. McKay’s, can be found on the web. My model has a number of flaws, some of which you pointed out, but it’s not doing anything spectacularly novel and I’m pretty sure it’s not doing anything spectacularly incorrect, either.

  141. George A. Gonzalez:

    re: #138

    The claim that my logic is circular is baseless. One variable causing a temperature increase (e.g., anthropogenic CO2 emissions) can trigger other variables (e.g., methane releases from tundra) that will compound and accelerate temperature increases.

    Respectfully yours,

  142. Eric:

    This discussion lacks comprehensive analysis of feedback. There’s
    cherry picking of known positive feedbacks (e.g. melting glaciers and
    tundra) and speculation about new ones (e.g. less snow in Greenland).

    But there’s little mention of negative feedback from increasing anthro
    CO2 and the subsequence water vapor feedback. Water vapor is
    speculated to correspond with “less cloudiness”, but that’s about it.
    The DTR discussion is interesting but not really relevant to climate,
    the more important effect would be higher or lower temperature in the
    daytime or nighttime.

    Here’s some negative weather feedbacks to consider: concentrated
    tropical convection is shown in models to be a negative feedback.
    Diurnal clouds are a negative feedback, in our temperate zone they
    occur after rain, when there is colder air aloft (generally when there
    is a more amplified jet stream), and other times.

    Determining which of those preconditions results from negative
    feedbacks (or are attenuated by positive) will require more modelling.
    Clouds in lower latitudes are a negative feedback.

    Increased land vegetation is a negative feedback. Burning vegetation
    is a negative feedback from aerosols. Ocean circulation is a negative
    feedback (vs stratification), increased plankton in the ocean is a
    negative feedback.

  143. George A. Gonzalez:

    re: #142

    There are no doubt negative feedbacks. The problem is that the evidence strongly indicates that anthropogenic CO2 emissions, and positive feedbacks are overwhelming the negative feedback.

  144. Hank Roberts:

    George, what evidence do you rely on for this conclusion?
    I’m guessing you’re the college teacher who has a book out relevant to the politics of environmental decisions — but I don’t have the book and am not sure. If you’ve published your references, would you tell us where to look them up?

    You are, I think, saying you expect more warming than Hansen et al. or the IPCC expect — you disagree with what the climatologists are telling us here is known and predictded from the research to date?

    I’m just an interested reader here. I thought about the same as what you’re saying, based on everything I knew, before I began reading RC seriously. Since I began trying to understand what they mean by climate sensitivity, I’ve backed off on what I claim I know.

    Now, when Hansen’s worried, I’m worried — and he’s worried. So I’m not saying you’re wrong. But I’m saying you’re being far more specific and definite than the climatologists about what’s going to happen.

    As to trouble coming –there are more possibilities than you are focusing on. Some are already included in the climate sensitivity calculation as feedbacks. Others like methane burps and dieoff of the aragonite-shelled plankton are not.

  145. Hank Roberts:

    To our hosts — would you consider reopening the ocean acidification thread?

    It didn’t get a lot of discussion before it closed; this area includes the unexpected feedbacks for which we have known good science — ocean chemistry.

  146. John McCormick:

    RE #141

    George you are right on point to keep reminindg us of the threats temperature increase present. Temperature increase equals: expansion of the tropical zone (observed); increased SST (observed); meltback of Arctic ice and change of Arctic ecosystem (under observation); meltback of global glaciers and temperature increase at higher elevations (observed); melting tundra and permafrost with their CO2 and CH4 feedback (in intensive care unit). And, we can add diminished snowpack and early melt in the Western North America and more frequent and extensive fires in the West (positive feedbacks).

    Higher temperatures beget higher temperatures, in my lifetime, despite increased cloudiness.

    As the earth’s human population approaches 7 billion –a time likely to coincide with China achieving the #1 CO2 emiter status, my pessimism needle is heading towards the red zone.

    Positive feedbacks are like a swarm of killer bees coming at us from every direction. Swatting them becomes useless as their venom weakens and eventually kills us. Should we have started the aerial spraying before the swarm arrived? Would there be time and will the chemicals be effective — at which point someone might advocate a non-pesticide approach?

    George, I am hot and cold about your encouraging geoengineering, though you are not advocating any particular line of research or end product. I am reading David Keith’s papers on geoengineering and there is much to be considered before taking steps towards realistic researach efforts (greater concern for ocean acidity being high on my list).

    However, there is no reason to believe we can function OK as the temperature approaches the 2 degree mark. For the sake of continuing civility around the planet, bio-engineering must also be a high priority. Stronger drought, pest and heat resistent crops and silviculture may be our means to buying a little, precious time to come upon a long term solution. I believe there will be universal understanding of the climate problem when barley and hops yields drop dramatically and beer sells at $14 per six pack.

    I know this thread is devoted to tipping points but a tipping point witnessed means there is no time to regain the balance on a global scale.

    A serious discussion on including —ALSO— adaptive measures to the world community’s approach to climate change is in order.

  147. Brian Gordon:

    Re: 141, 146: How nigh is the end?

    “Stronger drought, pest and heat resistent crops and silviculture may be our means to buying a little, precious time to come upon a long term solution.”
    Here’s one reason I don’t trust geoengineering solutions: say we develop and introduce all kinds of genetically-modified crops in an attempt to feed ourselves.
    A. Who is developing, manufacturing, marketing (globally) this GM stuff? Big corporations, and we can see how concerned they are about climate change….
    B. Who will sell you the special chemicals required to fertilize and keep weed and pest-free these wondrous new crops? I think we know….
    C. What happens to biodiversity when these crops are widespread? If the crops can be pollinated naturally, they will take over the land. If they cannot reproduce themselves, farmers (and therefore, everyone) are locked into annual seed-buying deals with big business.
    D. When will the ‘climate problem’ be over, so we can go back to the original crops? Maybe never. Or, maybe the original crops can no longer survive, because their habitat has been occupied by more resilient GM crops.

    Suffice it to say that not all of us are convinced that products produced in a lab and tested on rats are as ‘safe’ as plants we have evolved with over many millenia.

    “I believe there will be universal understanding of the climate problem when barley and hops yields drop dramatically and beer sells at $14 per six pack.”
    Beer in Canada has been up around there for some time, and…wait a minute, you may be on to something with this…. :-)

  148. Steve Sadlov:

    I want to put forth something here. Quantum behavior. We see it in physics. We see it in “digital” electronics. The term “threshold” is an apt term. “Tipping point” has a more ambiguous meaning. Thesis – we may be at, near or just a past a threshold. Possible deduction – a state change is underway. Following question – what is that state? Has the earth been there before, if so, when? Additional question – if such a state is a likely outcome, is it “bad,” “good,” or neither?

  149. Eric:

    George, on balance man is likely forcing positive. How much positive
    feedback could there be, especially once you do some smoothing to
    better compare to the naturally smoothed proxies? I see very little
    possibility of positive feedback having any current effect.

    Since the CO2 forcing can account for much of 0.6 C increase, how do
    we know “instant” positive feedbacks like water vapor will overwhelm
    negative feedbacks before slightly longer timescale feedbacks have a
    chance to kick in? I don’t see how a tipping point can occur when we
    may not be tipping (in feedback) at all yet.

    There is ample evidence of positive forcing natural cycles. There is
    evidence of some negative anthro forcing and other positive non-CO2
    anthro forcing, on balance positive. So not a lot of room for
    positive feedback and not a lot of time to take well-smoothed

  150. Eric:

    John, fires are a negative feedback due to aerosols.

    [Response: I think it may be the other way round. They produce aerosols yes, but a lot of them are black carbon (a warming influence), and they also produce NOx, CO and CH4 (ozone precursors) as well as CO2 of course. I’ll try and find a study that does the whole picture and report back…. – gavin]

  151. lars:

    More on ‘Frozen out’ and global warming
    There is also little dispute regarding natural climate change. Climate has never been static. Over the last few million years the climate has changed particularly dramatically and rapidly. Ice caps have developed in North America and Europe, melted, and then grown again 15 to 20 times. The ice takes about 90,000 years to grow, and 5,000 years or so to melt. The warm periods between glaciations last about 10,000 years. Ours has already lasted for this long. If the natural cycles of the past prevail, the climate should soon quite suddenly cool (over a few years or decades, although the climate switch may initially flicker). The North American ice cap will then expand to cover Canada, and reach Ithaca in about 50,000 years. Less dramatic cycles (the Holocene climate optimum, the little ice age, and the current warming) have affected humanity within our interglacial period. Natural climate change is real, rapid, and significant.

    Prompted by Scarborough, Stossel attacked Gore with Myths, Lies, and Downright Stupidity
    NAS report “said we can’t rule out that this [climate change] is just natural.” He claimed that the report’s authors “said we think” global warming is “man-made,” but that “we don’t know” and “[w]e can’t rule out that these are all natural influences.”

  152. Matt Pease:

    I just wanted to point out that in regards to the Pine Bark Beetle infestation of Alaska… I hope that you all are aware that most of British Columbia’s forests are currently being decimated by the Mountain Bark Beetle. Canadian officials fear that it will spread over the rockies and head east… making its way through the Boreal Forest (1/3 of the world’s forest) clear to the East coast of Canada.

    I read here that the current toll stands at 8.5 million hectares of effected forest. I read somewhere else that this number represents BILLIONS of trees. (4th paragraph talks about fear of spread to eastern canada)

    Somewhere I read that BC expects to lose 90% of their forest. I’m not sure where I read that… I didn’t understand if this was 90% of all forest, or 90% of the lodgepole pine (the beetle effected tree)

    It seems to me that we are witnessing the changes unfolding before our eyes. This event must be causing Canadians to want to move to renewable energy ASAP.

    Unfortunately… no such event has hit the US of A. And so people remain unaware of the growing urgent need for action.

  153. John McCormick:

    Fires also produce enough carbon dioxide that the recent (2002-2003?) increase of atmospehric CO2 concentration has been attributed, in part, to the massive fires in Borneo.

  154. John McCormick:

    Re #147

    Brian, you are getting geoengineering crossed up with bioengineering.

    I too am hesitant about the long term consequences of altering genetic structure of the foods upon which we depend. However, the nigh may be neared than we think or the models project.

    The concern about altering surivial food crops is, to me, a concern similar to the fear that disposal of nuclear waste will threaten humans for ten thousand years, at the least. Wish we had that much time on our side.

  155. Eric:

    My information is from studies using a model: (e.g. 9927482)

    [Response: Thanks! It doesn’t appear to include the ozone or CO2 effects, but it does show that the sulphates (+indirect effects) outweigh the soot effects. I stand (partially) corrected, but it may be one of those things that are quite model dependent. I’ll ask around…. – gavin]

  156. Lynn Vincentnathan:

    RE the positive feedbacks, any comments on the recent article to appear in the journal SCIENCE re how scientists may have seriouly underestimated the amount of carbon frozen in Arctic permafrost. Which could really spell disaster if it were released due to warming/melting….

    I guess what scientists don’t know (but perhaps discover later) could actually hurt us.

    I read reference to it at ClimateArk, an LA Times story, so of course it may have been sensationalized (or maybe not):

  157. Sean D:

    Hi folks, I guess this should really wait until a posting on clouds, but I started a new blog called “Head in A Cloud”, focused on current research in cloud physics and in particular cirrus (my research) and upper troposphere / lower stratosphere topics. Please feel free to swing by and say hi!

  158. pete best:

    This report brings together the material from the UK climate meeting in Exeter in 2005 and is headed by Tony Blair who personally believes that climate change is unsustainable and hence the major U turn on nuclear power as well as increased renewable energy commitments.

    This conference appears to have been mainly about type II – abrupt climate change and the speakers and attendeed certainly appear to believe in an worse than predicted warming world.

  159. Doug Percival:

    John McCormick in #146 wrote: “Stronger drought, pest and heat resistent crops and silviculture may be our means to buying a little, precious time …”

    Research by the Rodale Institute and others has found that organic agriculture produces higher yields during droughts than “conventional” petrochemical (fertilizer & pesticides) agriculture.

    A large-scale transition to locally produced, organic, vegetarian diets would be helpful in reducing both CO2 and methane emissions from food production and transport.

    For example a recent study by researchers at the University of Chicago found that the difference in CO2 emissions generated by producing the typical American diet and those associated with a vegan diet was comparable to the difference between driving an SUV and driving a compact sedan.

    And eating locally produced food eliminates the CO2 emissions associated with transporting produce such as lettuce and tomatoes (which are 90% water) thousands of miles in refrigerated diesel trucks, which is simply insane.

    Probably the smallest global-warming food-production footprint comes from growing your own food in a backyard garden. Victory Gardens, anyone? In the WWII era, Victory Gardens produced vast amounts of food and really helped feed the country during wartime shortages. Imagine the impact on energy consumption and CO2 emissions by agriculture if typical American suburbanites devoted the time and energy that they presently spend on maintaining lawns and various other decorative landscape plantings to organic food gardens instead.

  160. Dano:

    RE 148 (Sadlov):

    “Tipping point” has a more ambiguous meaning…if such a state is a likely outcome, is it “bad,” “good,” or neither?

    To restate, you say a tipping point is ambiguous. This is incorrect. The ecological literature is clear on this point.

    Your following questions:

    what is that state? usually is understood to be ‘a different stable state’ or ‘a less stable state’ than prior to the flip (depending upon the species or system being considered).

    Has the earth been there before, if so, when The five great extinction events (to use your implied global-wide scale. There have been many tipping points at smaller scales, such as desertification or Mayan-era drought.)

    if such a state is a likely outcome, is it “bad,” “good,” or neither? We must consider that our economies and social networks are predicated on THIS stable state. We have no experience or precedent for undergoing such a change to a different state on large scales. None.

    We see contemporary events unfold and read accounts of societal change in past events, and we make our judgements on how they turn out; our predilection for assessing ‘good’ or ‘bad’ from events colors our solutioning and judgement for how the solution turned out. That is: we are wont to assess moral outcomes to events according to our natures. Answering your question as it is framed is highly charged, at best.

    But certainly those charged with the stewardship of our societies should be cautious about committing societies to uncharted waters, with no compass, and no way of being sure of securing adequate provisions for the journey. So: having to lead billions forward when having no experience, IMHO, is “bad” in the sense that I wouldn’t want to do it, and I know or can conceive of no one who does.



  161. Pavel Chichikov:

    “A large-scale transition to locally produced, organic, vegetarian diets would be helpful in reducing both CO2 and methane emissions from food production and transport.”

    Proposals that run counter to cultural norms are not only success-proof, but they make the environmenal movement look, shall we say, not serious.

    Americans will give up hamburgers and go vegan when Mexicans switch from maize to buckwheat kasha.

    Anyway, there’s plenty of dry prairie out West which has always been unsuitable for grain but does perfectly well for stock raising.

  162. Mark A. York:

    “Unfortunately… no such event has hit the US of A. And so people remain unaware of the growing urgent need for action.”

    Not true. In central Idaho the bark beetle is on the march; and In the San Bernardino Mountains outside of LA. Great swaths have been cut due to beetle-killed trees under the National Forest Restoration Act and “Healthy Forests.”

  163. Mark A. York:

    Yeah here it is:

  164. Pavel Chichikov:

    Interesting local climate note here (Washington DC): About two weeks ago we received approx. 30 centimeters of rain in 4-5 days. I believe that the *yearly* average precipitation is approx. 95 centimeters. So we had approx. four months’ rain in 4-5 days.

    Some local home owners suffered appreciable property damage from flooding, and they applied to the regional water authority for compensation for damages – something to do with sewers I suppose. The authority rejected the claim, stating that the area had experienced a ‘200 year’ storm, which amounted in their judgement to ‘an act of God.’

    Which leads me back to the idea that if you want to track the development of climate change awareness in the practical world, keep your eye on the insurance companies.

    Swiss re, anyone?

  165. Lynn Vincentnathan:

    There’s been talk of solutions — all the more needed if we are headed toward a runaway tipping point of no return — including geo-engineering.

    And some have raised religion. (Thanks for posting these, since the religious communities seem in general to have fallen quite short on addressing GW — guess some just like it hot.)

    So here’s a solution: Pray to end GW.

    This is sort of scientific. I read about a science fair project in which a girl experimented on 5 marigold plants. One, the control, the others she talked to, played classical music to, rock music to, and one she prayed over. The talked to & classical music ones did better than the control, and the prayed over one did best, and (you got it) the rock music one….died. So even though there’s no empirical/material theory to go along with this, prayer does seem to work.

    For Catholics on this site I recommend dedicating each decade of the daily rosary to “ending GW”; it can be said while waiting in lines, trying to sleep at night, and other odd moments. The cost is nil, and I think it may finally do the trick of pushing the world’s populace to the tipping point of working to end GW, before we reach the tipping point of “GW is now beyond our ability (thru our GHG reductions) to halt or reverse.”

    (If this isn’t posted, I’ll understand.)

  166. Doug Percival:

    Pavel Chichikov wrote: Americans will give up hamburgers and go vegan when Mexicans switch from maize to buckwheat kasha.

    I’ve heard the exact same sentiment expressed innumerable times about how Americans will never give up SUVs and drive compact cars.

    What impresses me most about these sort of comments is the apparent underlying notion that the world revolves around “what Americans want”. If Americans want to drive SUVs, then there simply must be an abundant supply of cheap gasoline forever, and anthropogenic global warming must simply not be real. Case closed.

    If Americans want to consume vast quantities of cheap, factory-farmed cow and chicken and pig flesh, then there simply must be an unending supply of cheap factory-farmed grain to feed the animals, and an unending supply of cheap fossil fuels to power industrial agriculture, and the anthropogenic global warming associated with the CO2 and methane emissions from industrial animal agriculture must simply not be real. Case closed.

    This notion that reality must conform itself to whatever Americans want seems to me a sort of national infantile narcissism. And it is so ingrained that whoever brings up the inconvenient truth that reality does not, in fact, conform to whatever Americans want is viewed as, shall we say, “not serious.”

    My own expectation is that the vast majority of Americans will continue to believe that reality revolves around what they want, and will behave accordingly, until the bitter end. And the result will be ever-escalating wars for control of dwindling oil supplies, ever-escalating destruction of ecosystems, and irreversible, runaway catastrophic global warming, until the whole house of cards that constitutes the present-day “American way of life” collapses, in a very painful and ugly fashion.

  167. Brian Gordon:

    Re: 154: Confusing bio with geoengineering:
    John – I assumed that, for bioengineering to have sufficient effect, it would have to be carried out on a global scale. To me, this is, effectively, geoengineering.

    Re: 161: local, organic, vegan
    “Proposals that run counter to cultural norms are not only success-proof, but they make the environmenal movement look, shall we say, not serious.”
    I guess we have to find a way to make the US car-based, excessive-consumption culture work, then? I once owned an upscale vegan restaurant, in Sedona, Arizona. It was next to a Holiday Inn, and often we would get customers just before closing, who had just checked in. Not many Holiday Inn customers were vegan. Not many were happy to discover that the only restaurant they could get to before closing was vegan. Pretty nearly every one of them was shocked and awed that vegan food could taste so good, and that one could *feel* so good after eating. Without lots of wine. :-)

    I believe we are culturally biased toward meat because it is a status symbol: an expensive luxury that used to be in short supply, and another way of showing our dominion over nature. That can change. How much meat did we eat pre-industrial farming? We’ve invested a lot of money in making fast food tasty; no reason we can’t do the same with non-meat-based foods.

    Re: 152: Bye bye forests
    “Somewhere I read that BC expects to lose 90% of their forest. I’m not sure where I read that… I didn’t understand if this was 90% of all forest, or 90% of the lodgepole pine (the beetle effected tree)

    It seems to me that we are witnessing the changes unfolding before our eyes. This event must be causing Canadians to want to move to renewable energy ASAP.”
    You would think. However we recently elected a ‘conservative’ as PM, and they have a poor record conserving anything except their money.

  168. John McCormick:


    I want to turn your words upon you and in a constructive way because I share your sentiments and not all your ideas of what is possible.

    You said: “This notion that reality must conform itself to whatever Americans want seems to me a sort of national infantile narcissism. And it is so ingrained that whoever brings up the inconvenient truth that reality does not, in fact, conform to whatever Americans want is viewed as, shall we say, “not serious.”

    I could replace the word “Americans” with Doug Percival and I get the same result —– …..whatever Doug Percival wants is viewd as, shall we say, “not serious”.

    From Richmond, VA to north of Boston, about 100 million people have absolutely no opportunity to subsist on “victory gardens” letalone locally produced food….weather and land availability seeming to be the limting factors. Can we agree on that?

    Yes, I am sure the Rodale method can resolve some of the water deficit problems in agriculture but not on a ten thousand acre wheat farm. Though, there are likely experiments on small plots and farms that might give me hope that drought will not be a problem for the world’s grain basket farmers. But, I am pessimistic.

    I could go on with this reply about “serious” and include comments on campaigns to get Americans to walk or bicycle to work and short errands. But, I fear that will open a new channel for an “us” versus “them” food fight.

    Suffice it to say that solutions imposed upon the ignorant and unwilling will not fly at this “moment in time” in America. But, eventually, there will be nowhere to run and nowhere to hide. That is what I’m serious about…..thinking worst case —- even if that includes genetically modified food, trees, fiber; whatever we and our children and grandchildren will need to buy us some more time.

  169. Steve Sadlov:

    RE: #160 – You are speculating. You don’t know for sure.

  170. Gavin:

    Please remember to keep to the point, this is not the place to argue about ideal political systems or your personal opinions about ‘average Americans’.

  171. Doug Percival:

    With regard to possible “tipping points” in public opinion, I have been wondering what sort of event might act as a “global warming 9/11” — a shocking event that would quickly transform public opinion about the urgent need to make and/or accept large-scale lifestyle changes to quickly and drastically reduce GHG emissions? Is there any such event that is a real possibility, scientifically speaking?

    Or is it the case that there have already been such events — e.g. the 2003 European heatwave that reportedly killed tens of thousands of people, or hurricane Katrina — but that since it can always be said that “no individual extreme event can be directly attributed to global warming”, that no event, no matter how extreme, will ever cause the sort of “tipping point” in public consciousness that the 9/11 attacks did?

  172. John McCormick:

    Doug, I see the European heat wave, Katrina, the 36 inch rainfall in Delhi, and typhoon Larry that skimmed the Australain coast as snapshots in a “family album” documenting their suffering and projecting our future. If such events are symptomatic of climate change, their short history will make their autopsies difficult and likely irrelevant.

    However, using an American example, a decade of increasingly greater reduction of snowpack in the Rockies will translate into enormous costs to the US Southwest and particularly economies of Las Vegas, Phoenix, Tucson and Southern California. Dr. Lisa Sloan and her colleagues are beginning to report and warn of diminished water availability along the Pacific coast and the vested interests are certain to feel the pressure to accelerate water conservation, sell ag water rights to municipalities and implement water rationing programs. Depleting Colorado River water reservoirs beneath their outtake systems, in my mind, will be a 9/11 scale event.

    Maldives and other very low profile islands will have their own 9/11 scale events to experience and report but that will happen on a much longer time frame than diminished stream flow due to melting glaciers (e.g., Himalayan glaciers) and minimal snowpack with early melt.

  173. Eric:

    Doug, I think you are much more likely to see tipping points for energy consumption than for warming, It takes energy to make, deliver and use energy whether it is alternative or conventional. For example “$50” shale oil costs calculations were made when conventional oil cost $30. The energy shortage spiral will be made worse by political manipulation, subsidizing net negative energy sources for example.

  174. Hank Roberts:

    >160, 169
    Dano, excellent first link to that Google Scholar search on the usage ‘tipping point’ — good work there I hadn’t known about, some excellent papers in the first few hits. And a reminder that ‘don’t rock the boat’ is folk wisdom.

    >169 “don’t know for sure” — no one here does; this is science — if you want certainty, that is available in the math department, down the hall.

  175. Dano:

    RE 175 (Roberts):

    Thank you Hank.

    I took Steve’s comment to mean you are speculating about your assertion regarding the lack of leaders that are willing to lead billions forward after a tipping point [as we have no experience or memory to guide us, it is a daunting task that few will want to undertake]. That, surely, is a wish. Certainly leaders will arise as they always do, but only out of necessity and not a willingness for such an unprecedented challenge with no rule book.



  176. Steve Sadlov:

    RE: #175 – Specifically, you speculated that our future will bring an abnormality that rivals the 5 great extinction events. Without understanding innate variation levels in the system how can you say whether or not the effects of the projected range of abnormality rivals the effects of the abormalities that are believed to be potential root causes of those extinctions? You may notice I am really hammering this theme. Sorry to say it, but when a faction spends energy trying to downplay or discredit certain ranges of past variation (by trying to make the variation simply go away! or by saying it’s only regional!) that may well be within the normal variation of the “process,” it indicates that there is a sort of doctrine at work. The doctrine purports to describe some mythical “stable state” – almost a sort of Eden. Of course, against such a idealized stick like “flat” framework, the range of possible future innate variation or even, bona fide “subcritical” abnormalities, would appear to be disasterous. If, on the other hand, innate variation is in play, and the long term state is oscillatory, or even a quantum, semi chaotic sequence of events, with a myriad of states which we quite normally and expectedly flip between, then, even some of the worst case things being projected by models may fall well within the innate level of variation. Pause on this last bit, this “chaos and quanta” idea. Juxtapose it with Erwin et al and the notions of highly nonlinear evolutionary history – hopeful monsters – etc.

  177. Paul Duignan:

    Picking up on Pete’s point in #123 that he is troubled by not knowing exactly what climate scientists are trying to tell us about where we currently stand in regard to tipping points and todays ABC article on the acceleration of climate change which includes the comment: “But many experts confide privately what they aren’t yet ready to announce publicly: Change is accelerating at a dramatic rate” (URL below) I would find it very helpful if someone from Real Climate could tell us the summary message you want to get across to the public regarding tipping points – is it the “alternative version” I set out in #75 above or is it a modified version of this, if so it would be great if you could post the modified version up here – I would love to hear it.

  178. Hank Roberts:

    Paul, have you read these? I suggest this is as clear as anyone can be:

  179. Dano:

    RE 176 (Sadlov):

    Hmmm. I’ve discussed the contents of #160 with my editor and she agrees that I could have used a few more words to ensure such speculation as yours would be avoided. Ah, well – this happens in comment threads.

    Nonetheless, upon rereading the exchange, you’ll note that I responded to your ‘likely outcome’ question without passing judgement on its likelihood. That is: I merely answered the question you posed.

    If, on the other hand, innate variation is in play, and the long term state is oscillatory, or even a quantum, semi chaotic sequence of events, with a myriad of states which we quite normally and expectedly flip between, then, even some of the worst case things being projected by models may fall well within the innate level of variation.

    No and yes.

    Organisms exist within ranges of stable bounds. In ecological processes, scale is all-important and your oscillatory states must be bounded by some scalar limits for useful discussion. In socioecological processes, especially in today’s globalized, interconnected economy, regional effects can become global (cross-scalar cause/effect).

    However, we must note that ecological states rarely ‘flip’ at scales important to socioecological processes, and state changes at important scales during our agrarian era (the last ~10K yr) have been few but have had important, lasting impacts (viz. Anasazi, Maya, Eastern Med., Easter Is.).

    So, while one can discuss past variation all day, at time scales important to human society our ecological states have been, in effect, stable. We, simply, have no blueprint for leading this society, today, forward after a flip of an ecological state at any relevant scale. That was my point. We don’t know what agriculture will be like if the state flips in, say, central Europe and wheat can’t be grown there.



  180. William Golove:

    In my PhD dissertation, “Avant Le Deluge: An Investigation of Some Neglected Dimensions of Electricity Restructuring in California,” I did proposed a name for this rhetorical phenomenon. I refer to it as “High Salience Terminology,” which basically refers to words and phrases used in a political context that tend to be persuasive/influential, either positively or negatively. I also describe a process which I refer to as the “Search for Salience” were participants in a particular debate/discussion use various terms until one or more emerge as high salience, at which point there is a move toward widespread use.

  181. ms @ cu:

    Nice post!

    Tipping point:

    -phase change (e.g., “freezing” liquid to solid)
    -bifurcation (e.g., fork in the road)
    -self organized criticality (e.g., see Per Bak, avalanches, sand pile experiments, ecocatastrophes…)
    -cusp (e.g., “cusp catastrophe”, like in ecological situations like the spruce budworm outbreaks as described by Ludwig, et al)

    These things aren’t necessarily irreversible, of course, though “hysteresis”, e.g., might make it a bit of a long road back to where we were or want to be…

    Some authors re nonlinear systems, complexity, “tipping points” (that can keep it manageable for the laypeople that most of us here are, to be honest with ourselves):

    -Barry Saltzman
    -Steve Strogatz
    -Duncan Watts

    Happy reading!

  182. ms @ cu:

    Hi Sean D.

    Re your post #157, maybe you have something to say about “tipping points”, being that cloud droplet nucleation, growth, and evaporation are nice manifestations of behavior around a “tipping point”, or struggle of competing “interests” (surface tension, vapor pressure, e.g.) tipping towards a particular outcome (growth, evaporation, or niiice and steady now)…

    You might be interested to take a look at Prigogine’s words in this context, e.g.. Fun fun.

    Thanks for the heads up on your blog.

  183. Hank Roberts:

    Here’s a useful perspective on major changes:

  184. Lynn Vincentnathan:

    RE #176, I agree that nature has been fluctuating greatly on earth over the past billions of years. And it could make the climate warm all on its own (without human help) in the future, or cool to severe ice ages.

    So my idea is that we not add to any warming nature may cause naturally — & who knows when nature might get a fever, so it’s just prudent not to release GHGs, even when nature doesn’t seem to be warming the earth (due to the time lag). On the other hand, we will need to save all our fossil fuels for an “ice age” day, so we can tweak up the climate a bit when that happens.

  185. Hank Roberts:

    Relevant to the topic,

    Discussion found (second hand already) mentioned here:

    “Article: “Leverage Points: Places to Intervene in a System”

    “I read this fascinating paper over the weekend by systems analyst Donella H. Meadows, called “Leverage Points: Places to Intervene in a System”. Leverage points are those “places within a complex system (a corporation, an economy, a living body, a city, an ecosystem) where a small shift in one thing can produce big changes in everything.”

    “The central thesis of Leverage Points is to elucidate a theory by MIT professor Jay Forrester that “People know intuitively where leverage points are…[however] everyone is trying very hard to push [them] in the wrong direction!” So Meadows observes that paradoxically “Leverage points are not intuitive. Or if they are, we intuitively use them backward, systematically worsening whatever problems we are trying to solve.””

  186. bender:

    Re: #152: warming and beetle outbreaks
    1. 90% loss of trees in BC due to pine beetles is an overestimate. In some localized instances losses will be that high. Averaged over larger areas, the figure drops considerably.
    2. The loss would only apply to the host tree: lodgepole pine, not all forests.
    3. Warming is not the only factor responsible for the unusual severity of this outbreak. Other suspected factors include selective harvest of spruce over pine, fire suppression, and the ever-present unknown.
    4. What makes you say that “no such event has hit the USA”? The pine beetle outbreaks in the US Rockies in the 1960s and 1980s were extreme, and may have been an early warning sign of trends to emerge later at higher elevations and latitudes. Read papers by Jesse Logan. (The spruce beetle in Alaska may turn out to be a present-day example of the same sort of response.)
    5. There is a lot of uncertainty surrounding insect responses to climate change. Don’t be so quick to assert.
    6. Science is the cure for uncertainty. Yet funding for forest, insect & climate science has not increased in proportion to public concern over the issue. If you want more science and less uncertainty, write to your elected representatives.

  187. George A. Gonzalez:

    The current heat wave gripping vast areas of the northern hemisphere indicates the vital need to plan a geoengineering approach to counter ever increasing temperatures. Current temperatures point to the very real possibility that we are already past a tipping point.

  188. Colin:

    Thank you Hank #185. The link to the paper on Leverage points is a real bonus. I have saved it and will send it on to several of my co-conspirators with whom I am attempting to engineer a Paradigm shift. I recomend it as a reference paper and a prop for those times of despair that we all get every now and then.

  189. Hank Roberts:

    >185, 188
    One of the earlier online cites to the Meadows article is here:

    Interestingly they also address social network analysis — it reads as a serious early attempt to look at the tangles that occur when multiple problems interact that affect public health and there’s no easy way to get hold of leverage that works.

    Interestingly Meadows was also writing about climate modeling — from the references at that CDC page:

    Meadows DH. Leverage Points: Places to Intervene in a System. Sustainability Institute, 1999.

    Meadows DH, Meadows DL, Randers J. Beyond the Limits: Confronting Global Collapse, Envisioning a Sustainable Future. Mills, VT.: Chelsea Green Pub., 1992.

    Meadows DH, Richardson J, Bruckmann G. Groping in the Dark: The First Decade of Global Modelling. New York, NY: Wiley, 1982.

    24 years ago, that last one. Anyone got a copy, for reference?

    The CDC page says:

    “The term â��syndemicâ�� refers to the phenomenon of linked afflictions. Scholars and practitioners have long observed interactions among diseases, but it wasnâ��t until the early 1990s that anthropologist Merrill Singer suggested that empirical connections among epidemics might signify the existence of a higher-order phenomenon–a syndemic. ”

    Yeah — linked afflictions. We got’em.

  190. George A. Gonzalez:

    This was sent to me today. It is a synopsis of an article in the _Independent_:

    _Maybe I’m Amazoned at the Way I Really Need You:
    Drought could turn Amazon into desert, researchers warn_

    The Amazon rainforest — soon to be called The Artist Formerly Known as the Amazon Rainforest, and then just some weird little symbol — appears to be undergoing a second year of drought, and that has researchers seriously alarmed. Starting in 2002, scientists at the Woods Hole Research Center simulated drought on a small section of the Amazon and found that after two years, the trees began to die, fall, and release more than two-thirds of their lifetime storage of carbon dioxide. Widespread desertification of the rainforest would likely spread drought into the northern hemisphere; the Amazon contains 90 billion tons of CO2, enough to accelerate global warming by 50 percent, spinning it out of control and eventually making the world uninhabitable. Computer models predict that harm to 50 percent of the Amazon would represent a tipping point — after that, the whole thing starts going down the tubes. Today, about 20 percent has been totally razed and 22 percent has been harmed by logging. Oy. It’s only Tuesday and we’re already doomed.

  191. Greg:

    RE: …CO2 are already very unlikely to revert to pre-industrial values…

    In reviewing the historic “bubble data” in ice cores: 1) there were several periods of rise and fall of temperature, CO2, and CH4; and 2) there were times when temperature rise precedes the rise in CO2 and CH4.

    From it, I conclude that: 1) the relationship between greenhouse gases and temperature is uncertain; and 2) there is some feedback mechanism that has prevented the earth from passing â??the tipping pointâ?? before.

    I recognize that we have gone beyond the previous CO2 peaks and that there is no existing ice to provide the same information on CO2 concentrations in previous times. But what was it that stabilized the earth before and how are we certain that not enough of it currently exists now? Also, other paleo-data suggests that CO2 was much higher in the times long before the current caps were formed. What mechanism removed the CO2 and initiated the ice formation? And since then, what is the cause for the periodicity of the long cooling periods followed by short warming periods until this point?

    I am not planning to count on other feedback mechanisms, but want to recognize that those mechanisms we have are not fully understood â??at least not to me yet.

    This site has been extremely educational. Thanks.

  192. Alastair McDonald:

    Re 191. The easiest way to reply is to say that you are correct!

    In the Antarctic ice cores (but not the Greenland cores) the temperature rise has nearly always preceded the rise in CO2 and CH4. Your conclusion that the relationship is uncertain is also true. However it is known that greenhouse gases cause warming, and it seems most likely that the increase in sea surface temperture cause the atmospheric CO2 concentration to rise, and that the increase in land surface temperatures causes the CH4 levels to rise. Thus both gases act as positive feedbacks, and global warming will keep the greenhouse gas levels high even if we stop emitting them, so making global warming self perpetuating.

    There is a negative feedback which prevents global temperatures running away until the surface temperature of the Earth matches that of Venus, and it is the same mechanism that prevents Venus getting any warmer. It is clouds. But clouds do not gently increase as tempertures rise. For clouds to increase we need temperatures to rise considerably, so that the climate settles into a new regime where cloud cover is greater. The tipping point will occur when the current cloud system can no longer provide the negative feedback needed, and temperatues rapidly rise until a new cloud system exists.

    Clouds are the least understood part of the climate system, so you are not alone in not understanding the climate, and the consequences of global warming!

  193. John L. McCormick:

    When I read your question Greg, I wondered how it could fetch a short and clear answer. Alastair delivered the goods.

    Now, I would add the other postive feedbacks in the form of melting tundra and permafrost yielding CO2 and CH4 while the oceans acidity accelerates. All contributing to a destabilization over a narrow band of time and too short an interval for humans to adapt civily.

  194. Karl Sanchez:

    Once again, for the 5th year running, we have a dead zone off the Oregon coast, a zone that’s getting larger every year (here’s a google link to recent news reports about this, ).

    One scientist noted that this behavior is predicted by global warming models for that region of the Pacific. Is this further related to the lack of mixing action between different ocean layers and predicted increases in acidification due to AGW forcing changes to oceanic and atmospheric circulation? Would it be possible to have a Forum thread address the topic of AGW’s assault on terrestial and oceanic food chains?

  195. Phillip Shaw:

    Re #194 – Is there any connection between the dead zones off the Oregon and Gulf coasts and the large methane hydrate deposits off those same coasts? Would the release of methane stimulate phytoplankton, which later dies and rots? Or could there be a chemical reaction between dissolved methane and oxygen that depletes the oxygen level below that needed to sustain life? Please excuse me if these are silly questions.

  196. Karl Sanchez:

    Re #195 This item provides answers to your questions,

    Methane hydrates aren’t the cause, but the anoxia is caused as dead plankton’s decay.

  197. Phillip Shaw:

    Re #196 – Karl, thank you for the link to the interesting article. Much of the information I already knew and I suspect my questions weren’t phrased very clearly. So I’ll try again.

    The 12/12/2005 RC article on methane hydrate (I’m sorry but I don’t know how to provide the url) refers to large hydrate deposits along the Oregon and Gulf coasts. It describes various ways in which a hydrate deposit can become unstable and melt or break up. And it says “Dissolved methane is chemically unstable in the oxic water column of the ocean, but it has a lifetime of decades (shorter in high-flux environments) [Valentine et al., 2001], so if the methane is released shallow enough in the ocean, it has a good chance of escaping to the atmosphere. Bubbles of methane are typically only able to rise a few hundred meters before they dissolve.”

    I’d like to know what the chemical reaction is for the unstable methane. Is there a net reduction in the dissolved oxygen? And I assume from the article that if the methane hydrate deposit is melting then the bottom water will have a high level of dissolved methane. If this methane saturated bottom water upwells what effect does the methane have on the phytoplankton at the surface? Does it serve as a foodsource and promote rapid growth? Does it inhibit phytoplankton growth? Or is it essentially neutral? Has anyone sampled the dead zones for dissolved methane levels?

    The metaphor I’d use is that the ocean dead zones are the ‘canaries in the coalmine’, dead from an overdose of methane. The persistence and growth of the dead zones may indicate the onset of large-scale hydrate melting. Heaven help us if that’s true.

  198. Karl Sanchez:

    Your hypothesis and questions I’m unable to answer. However, I will forward them on to the scientist from the Hatfield Marine Center in Newport quoted in the article. An additional note, the lack of upwelling problem stretches from the southcentral Califonia coast to beyond Vancouver Island, see this item:

    I’ll post whatever response I get from Hatfield.

  199. Hank Roberts:

    The lack of upwelling itself is enough to explain the methane levels observed, and the change in wind explains the change in upwelling. I know that observations are made of methane bubbling up.

    Note that fossil methane will be detectable because there won’t be much if any carbon-14 in it, while methane from decomposition of recently dead material will have contemporary levels of carbon-14.

    There’s a lot of attention being given to what happens when the plankton production (“primary production” — the first step where photosynthesis occurs). One example:

  200. Phillip Shaw:

    Thank you both for helping me understand more about this. I, like many others, am still on the steep part of the learning curve about AGW and I really appreciate the information provided by the scientists such as yourselves.

  201. Hank Roberts:

    Philip, I’m another reader like you are. The creators are identified under the sidebar “Contributors” — they’re helping us all learn to read and understand this. I count on their followups a lot (in the sidebar, see “…With Inline Responses” to jump to places they’ve added comments).

  202. Hank Roberts:

    Worth a look:

    which points to these arguments:

    and to RC

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