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Exeter conference: Avoiding Dangerous Climate Change

Filed under: — group @ 7 February 2005 - (Français)

The conference last week in Exeter on “Avoiding Dangerous Climate Change” grew out of a speech by UK Prime Minister Tony Blair. He asked “What level of greenhouse gases in the atmosphere is self-evidently too much?” and “What options do we have to avoid such levels?”. The first question is very interesting, but also very difficult. As Roger Pielke has noted the conference organisers actually choose three “key questions”:

  1. For different levels of climate change what are the key impacts, for different regions and sectors, and for the world as a whole?
  2. What would such levels of climate change imply in terms of greenhouse gas stabilisation concentrations and emission pathways required to achieve such levels?
  3. What technological options are there for achieving stabilisation of greenhouse gases at different stabilisation concentrations in the atmosphere, taking into account costs and uncertainties?

It is worth thinking about the difference between the initial aim and the “key questions” chosen. Question 1 is essentially IPCC WGII impacts); question 2 is firmly WGI (how-much-climate-change); question 3 is fairly WG III (mitigation, including technical options). I guess they switched questions 1 and 2 round to avoid making the identification too obvious. The conference steering committee report makes it very clear that they are building on the IPCC TAR foundation.

All in all it would seem that the bold vision of the politicians has been tempered by the conference organisers into something more manageable – a set of questions that can be discussed within the usual scientific framework and by the usual people. And probably that was sensible, because the initial question really is very hard – not merely because all the science isn’t in, but because even if it was what is “dangerous” is probably a political rather than scientific question. And this was a largely scientific meeting.

So, what’s new? On the impacts front, the final report says that there is more clarity and less uncertainty since the TAR, which is what you would hope for after 4 years of research. They identify a few “thresholds” that are dangerous for certain processes – 2.7 ºC local for melting Greenland; coral bleaching above 1 ºC global. Extremes, and the 2003 european heatwave get a mention. On climate change, they note that restricting the global temperature change to 2 ºC with a fair degree of confidence would require stabilisation at 400 ppm CO2 equivalent (CO2 itself is at 380 already, but “equivalent” includes other GHG’s and the negative effects of sulphates; see here for more). If you were prepared to accept more risk of exceeding 2 ºC then 550 ppm would be possible. For technical options, they note that the IEA predict a 63% increase in CO2 levels by 2030, in line with IPCC estimates. There are a whole raft of options that could be taken to reduce emissions, and they do mention the word “nuclear”.

All in all, it looks like progress as normal. In summary, they note that work is needed on both mitigation and adaption – which is to recognise that climate change is occuring and will continue, although possibilities for slowing it exist.

To pick out some of the science, there is the perennially interesting “will global warming cause cooling” bit that people love so much because it seems paradoxical. This is the “thermohaline circulation (THC) shutdown” or slowdown, caused by freshening of the North Atlantic. Of course it wouldn’t (at its worst) lead to global cooling, it would mostly impact Northern Europe. And the IPCC TAR said even in models where the THC weakens, there is still a warming over Europe (because the overall warming outweights the local cooling). This still seems to be true. The conference was presented some results showing what happens if THC shutdown is artifically induced (by Richard Wood), and various attempts to explore the probability of a collapse, but coupled AOGCMs seem to be quite resilient to a total collapse. From impacts, they mention that “resilient” societies are better able to survive climate stresses – for example, they downplay the oft-mentioned risk of malaria spreading under increasing temperature: the increase expected is small compared to the total number; all it means is that existing efforts to combat malaria should be strengthened.

And finally, since it gets a mention in the report, there are two possible errors to make, apparently labelled Type 1 and Type 2. Type 1 is excess caution, leading to damage by unnecessary action restricting development. Type 2 is insufficient action, leading to damage from climate change. In the face of uncertaintly, it is very hard to steer a true path avoiding these two errors, but it appears that we should be tilting towards taking action.

The conference generated a lot of press coverage (thanks Het). Nature said UK climate meeting calls for action; New Scientist said Climatologists pursue greenhouse gas danger levels and Only huge emissions cuts will curb climate change. The BBC told us of Scientists’ grim climate report, that “The risks from global warming are more serious than previously thought”. The Guardian warned of A grim assessment of the global cost for each degree rise in temperature and the Manila Times says Evidence indicates climate change already here, which is a mild strengthening of what the IPCC TAR told us. The reporting seems reasonably fair – slightly sexed up headlines, as usual, but the text of the articles quite faithful to the conference.

43 Responses to “Exeter conference: Avoiding Dangerous Climate Change”

  1. 1

    From the article:

    “So, whats new? On the impacts front, the final report says that there is more clarity and less uncertainty since the TAR, which is what you would hope for after 4 years of research.”

    How much more clarity? I would like to see more regional climate change evidence. For example:

    “Trends showing earlier snowmelt runoff in the Upper Midwest”
    and at:

  2. 2
    George Blahusiak says:

    So what are the technological fixes to addrss this problem after they were so prominently mentioned at the start of the speech? Or was this just another example of political speak?

  3. 3
    Jeffrey Davis says:

    I like it that Blair is asking questions like that of the scientific community, but I suspect that the first question is preposterously loaded.

  4. 4

    Re #2, it certainly seems time to put nuclear power back on the table. There’s an interesting popular article promoting this point of view at

    It concludes that “the more seriously you take the idea of global warming, the more seriously you have to take nuclear power” and, more tersely, “it’s time to get real.” I’m not an expert on the problems and prospects of nuclear power, but the article seemed compelling to me at first blush. In short, given that it is “time to get some policy traction” on global change, nuclear power does seems much less speculative than any alternative other than continued ineffectual handwringing.

  5. 5
    Nick Riley says:

    In response to comment 2 and technical fixes. The conference was mainly for climate scientists. The technical fixes come from other disciplines- so that part was weak. Princeton University have done a good review (published in “Science” last August) using the illustration of a wedge of technologies needed to achieve 550ppm CO2 stabilisation, including energy saving/demand reduction, renewables, nuclear and CO2 capture and storage. All achieveable with existing technologies (or slight adaptation of). The critical issue is the value of CO2 abated required to create a market for industry to invest and use the technology. At the moment there is little incentive. This latter issue is political & urgent.

    Nick Riley
    Manager, Sustainable Energy Programme
    & Co-ordinator of the European Network of Excellence on geological CO2 storage, “CO2 GeoNet”.
    British Geological Survey

  6. 6
    Grundt says:

    Mmm. That would be a different kind of danger. But, anyway, there is no way to fix Earth problems no matter which one we chose.
    More Nuclear Reactors could be a source of more dangers (statistical sense, probabilities). Waste disposal, despite new technologies, is a nightmare, to name only one. Natural disasters could evntually hit some of these power reactors if they are not well located and designed.
    A pity that scarce efforts were done in the past to construct a strong alternative energies platform.
    Every activity must be taken in account, not only fossil fuel use. Livestock, rice growing, release lots of methane, a powerful GHG. And there are many other sources of GHG gases.
    It would be a good intellectual exercise to imagine what humanity would have done if we had no fossil oils to rely on as energy source.

  7. 7
    Arthur Smith says:

    If you’re looking for technological fixes, they do exist, but R&D to make them commercial-scale has been badly underinvested since about 1980 (at least in the US). Bio-energy and solar photovoltaic solutions (including space-based systems) are feasible and probably competitively scalable to the level needed; fusion may also be but a practical reactor is still decades away. Not much else can do it – not even nuclear, unless we’re willing to live with vastly increased risks from fission reactors…

    More discussion of these topics at the Alternative Energy Action Network –

  8. 8
    Niko Jaakkola says:

    One interesting update – which certainly got some media attention in the UK – was the British Antarctic Survey director Prof. Chris Rapley’s revision of the West Antarctic Ice Sheet from ‘slumbering giant’ (IPCC TAR) to ‘giant awakened’. I’m sure it’s early days for anything even remotely conclusive, but the melting of WAIS is supposed to be one of the more credible ‘disaster scenarios’…

  9. 9
    Steve Bloom says:

    My impression from looking at the conference material is that it was indeed more or less what you would expect four years on from the 2001 IPCC report, with two very large exceptions: The potential collapse of the West Antarctic Ice Sheet (= 5 meter sea level rise) and ocean acidification (= partial ocean ecosystem collapse with a subsequent cascade of potential side effects that practically defy description). What about these, William?

    [Response: collapse of the WAIS is still a long way off, I think – William]

    Re #4: Which table would that be, the one in your kitchen or the one in your dining room? You may want to check with your family and neighbors first. Seriously, a big part of the global problem is that scientists and politicians tend to be biased in favor of the “big fat techno fix” approach. I lump in large-scale sequestration along with nuclear (and here in the U.S. at least, “clean coal”); what they have in common is that much money will be made by the usual suspects. Efficiency and conservation, which just don’t have the same potential for concentrated profit-making, always seem to get short shrift, despite making vastly more sense and being prone to immediate implementation.

  10. 10
    Ken says:

    Between 2000 and mid-2003 global CO2 releases have reportedly doubled from their 1990’s level. At least part of the increase is believed to be massive, uncontrolled burning of peat bogs in Borneo, which were estimated to account for 13-40% of global CO2 emissions in 1997.
    Was there any discussion of this topic at the Exeter conference? Has the emissions spike subsided or continued since mid-2003; is it adequately understood; and is it accounted for in climate models? Are scientists and politicians giving this issue adequate attention?
    This is significant. If the Borneo fires are primarily responsible for a doubling of global CO2 emissions, the countries participating in Kyoto could probably all meet their entire treaty obligations ten times over by helping to extinguish the fires. What is the current status of global CO2 emissions and what is being done about the burning peat bogs?

  11. 11

    Nuclear power while not releasing CO2 has major unresolved issues. No reliable method has been determined to accurately predict the behaviour of waste and waste storage for the timescales necessary. This is supported by the following quote from

    “Nevertheless, the common perception is that for geological disposal specifically, one must be able to predict the future accuratelyâ��and it is beyond established engineering practices to predict accurately for many thousands of years how the waste and the repository will behave. It is also beyond established practice to predict accurately whether or not some of the radionuclides disposed in the repository may move through the geological formations and eventually come in contact with human beings and the environment in the future and cause them harm. As emphasized above, however, the challenge is not to accomplish these impossible tasks, but rather to assess the range of potential future behaviors with sufficient confidence to allow the appropriate societal decisions to be made.”

    Nuclear Power also has security and weapons proliferation problems. Right at the moment Iran under the spotlight for its nuclear program. If nuclear power is the answer then all countries will need it including the ones we regard as unstable. We cannot say that it is alright for us to have nuclear power and deny everyone else if this is the best method of stablising CO2. NP is not the green solution to the Global Warming problem.

    Clean Coal also has problems. Sequestering CO2 has much of the same problems on nuclear waste storage. It is not enough to say that we can store it safely for 1000 years – what about after this? Really what these proponents are saying is that as long as it is safe until after I am dead then this is OK. This seems to be a human problem – the inability to see too far into the future. To us 1000 years is along time – to the Earth it is but a microsecond. To read more on this please follow this link

    I agree with comment #9. We cannot rely on a “techno-fix”. We have to face the fact the we have change our lifestyles to achieve a real reduction in CO2 levels. Efficiency and conservation must be implemeted on a large scale throughout the developed world and encouraged in the developing world. This coupled with increased use of renewable energy will achieve at least a stabilising of the CO2 level to what we hope is a ‘safe’ level.

    If you are interested I am proposing a method of producing methane from solar energy using atmospheric CO2. It is an extension of the Solar Hydrogen idea. You can read about it at This is not a fix but a method of powering a scaled back society without nuclear power.

  12. 12
    David Ball says:

    I’m reminded of the old saw about the man who goes to the doctor and says, “Doctor, it hurts when I do this!” to which the doctor replies, “Then don’t do it!” It always amazes me that people will invest time and money in looking for the grand solution instead of first doing the simple things. If our GHG emissions are causing the problem, the simplest solution is to reduce our emissions. That being said, technological “solutions” – something of a misnomer since this is a problem that can be mitigated not solved – should be directed at reducing emissions. Too many people are waiting with baited breath for technological advances that will allow them to continue their wasteful habits. That’s like a grossly overweight man waiting around for a miracle drug to help him lose weight rather than going on a diet. The point Michael Tobis makes about getting “policy traction” is well taken, but that isn’t going to happen until the public is more aware of the scope of the problem. Right now, I don’t believe it’s a problem they are even aware of except as part of a media sound-bite. Without the public clamoring for action, policy-makers are going to take a wait and see attitude and ultimately nothing will get done.

  13. 13
    Ajax Bucky says:

    That world-damaging short-sightedness in the service of prodigal energy consumption might be relieved by substituting one proven harmful source with another is exactly the mind-set that has brought us the dilemma it addresses.

  14. 14

    Great post. Just a small note on this one: “If you were prepared to accept more risk of exceeding 2°C then 550 ppm would be possible.”
    I think we should be clear about what “more risk” means in this context. It means 70%-99% risk of exceeding 2°C.

    Using available climate sensitivity uncertainty estimates (pdfs by Murphy et al., Gregory et al., Forest et al., Wigley&Raper, Knutti et al., etc…), the probability of overshooting 2°C global mean temperature rise above pre-industrial levels for a stabilization at 550ppm CO2eq are between 70%-99%. In other words, we can be rather certain that we are going to overshoot 2°C, if concentrations are not going to be peaked well below 550ppm. For 400ppm CO2eq stabilisation (and earlier peaking at 475ppm), the risk of overshooting 2°C is of course much less, although not zero (specifically: 4% to 55% risk). Assuming the conventional 1.5-4.5K IPCC uncertainty range (and its translation by Wigley & Raper, 2001, into a lognormal pdf assuming the range to be a 90% confidence interval), this risk of overshooting 2°C is about 75% (13%) in equilibrium for 550ppm (400ppm) CO2 equivalence stabilization. (see e.g. Exeter presentation )

    All risk numbers given above assume the climate sensitivity pdfs to be truncated at 10K, if necessary. Not trunkating them would make even more obvious, that today’s science cannot judge any stabilization level being “safe” (apart from pre-industrial or maybe 350ppm), since the real climate sensitivity might be high. Not very likely, but it cannot be ruled out completely. However, if we are going to peak concentrations and return to lower levels (e.g. 400ppm), we might be lucky and never find out what the real climate sensitivity is. Thus, research should focus more on peaking scenarios (with a possible stabilization at lower levels later on) than on stabilization scenarios a la “go up & stabilize” – see e.g. excellent talk in Exeter by Myles Allen on this: ).

    Cheers, Malte

  15. 15
    tom says:

    While we are pondering technological solutions, the size and horsepower of cars increase every year, not to mention the fact that the speed limit was raised under Clinton. If we had just kept size and hp constant since the 70s, we would have gone a long way to addressing global warming.

    Another technological fix is hydrogen. Great. Bush canceled the project to increase MPG in favor of hydrogen. The program, as constructed, does nothing to reduce GHG since it relies on mainly on fossil fuels to produce hydrogen.

    As long as it’s all about freedom, nothing serious will be done to address the problem. There are things individuals can do, but individual action will not solve the problem. As long as everyone else is merrily consuming as if there is no tomorrow, it’s hard to keep the faith.

    Technology’s great contribution of the last two decades was to give us the SUV.

  16. 16
    tom says:

    “What technological options are there for achieving stabilisation of greenhouse gases at different stabilisation concentrations in the atmosphere, taking into account costs and uncertainties?”

    With discussions related to the above, I cannot see how you can avoid political or economic discussions. Too bad they didn’t address lifestyle options. I fear Blair wants to avoid change that would be “inconvenient”.

  17. 17
    Grundt says:

    Stephen Gloor, you express a key problem “proponents are saying is that as long as it is safe until after I am dead then this is OK. This seems to be a human problem – the inability to see too far into the future. ”

    very good your article in your blog: “A Totally Stupid Article on why we Need More Nuclear Power”.

    Ball, you also say something that has been disappointing for so many serious environmentalists: ” Too many people are waiting with baited breath for technological advances that will allow them to continue their wasteful habits”

    People always expects miracles from “God Technology”

    Find many of the comments are very good.

  18. 18
    Lynn Vincentnathan says:

    An excellent source for solutions is NATURAL CAPITALISM by Paul Hawken and Amory Lovins (also see and They suggest we can lower our energy (& other resource) use on a U.S. national scale by more than 3/4, sometimes 9/10, WITHOUT LOWERING PRODUCTIVITY or living standards, with current technology. Even if they are wrong by 20%, this is very signficant. Perhaps I wouldn’t believe it, except my household has reduced by more than 1/2 while increasing our living standard and SAVING $$$. When I read about a poor woman in Chicago in a one bedroom apartment in Chicago with a $400+ gas bill (when ours was less than $200 for that same winter month with a 4 BR 2 bath house in the colder Chicago suburbs, and my friend’s passive solar home in the burbs was a tiny fraction of ours), I say why not try caulking and insulation? Duh! Maybe even fix those gas leaks.

  19. 19
    Grundt says:

    ***..this is not Crichton´s fear.*** In this moment..
    Here in Venezuela we are living frightful days. Since yesterday we have had absolutely unusual, non-periodic rains… People are being evacuated from some coastal towns. In the capital some landslides also (they happen usualy from May to November).

    Since some years, more rain is falling during the so called “dry season”.
    In December 1999 we had one of the hughest catastrophes of America, when a gigantic landslide, after raining for some days over Avila mountain, swallowed thousands, and changed tophography at the coastal side (Caracas is at the other side of the mountain, but at a higher level above sea). Rocks the size of buses, rumbling before daybreak, destroyed everything.

    That was a periodic event… one of more than 100 years periodicity.
    Now we are having abnormal events the last years (not this size, but it could happen any moment again, as it is raining and raining.. It used to be so periodic.. the seasons, we have only two: Dry and Raining, or wet, or “winter” )

    We know former and this week rains are effect of the Cold Front. But…

    In some coastal mangroves, people can see sea level is higher…
    Natural or man-driven, this is happening…

  20. 20
    Grundt says:

    +More about nuclear waste:
    Time Ticking on Nuclear Waste Decision,
    February 07, 2005 â?? By Robert Manor, Chicago Tribune

  21. 21

    Regarding the responses to my suggestion of nuclear power, I have to say it is a peculiar experience for me to be cast as a defender of the status quo.

    The problem is that voluntary simplicity has never been a big seller among the rich, and has essentially no constituency among the poor. That we could theoretically be more comfortable with less consumption if everything were different (a proposition with which I heartily agree, for what it’s worth) is beside the point. Everything is not different. Thirty years ago it looked to some of us that the world might get different and better fairly quickly, but all we got after a generation was the same old stuff plus Google and more espresso bars.

    The people are who they are, not who we might wish they were. It isn’t remotely clear that we have the time to make the sorts of cultural shifts we need on the time scale we need to protect enough of our natural resources to matter.

    I think it’s an awfully risky proposition to be betting the future of the world on an immediate worldwide dawning of profound social and environmental insight. If there’s any alternative, if there’s a technical fix to some of our biggest environmental problems that doesn’t require a vast shift in the culture, it would be the height of folly and arrogance to pass it up .

  22. 22
    Laura Schilling says:


    Resources will be used until they are gone. To expect a capitalistic world view to do anything different is idealistic.

    Human beings would have to experience a huge shift in order to change their behavior (not just a shift in consuming practices but a shift in ‘spirit’ for lack of a better word).

    With the odds of this happening being right about at 0, there are still some of us who do practice simple living, for myself this includes living off the grid and moving towards 100% self sufficiency. I can’t change the world but I can change my behavior, elect not to procreate and sleep nights knowing I left a small footprint only when I pass on.

    That being said, the earth will be here long after human beings have rendered it un-liveable.

  23. 23
    Mike Atkinson says:

    I’m surprised no mention has been made of the land changing from a sink to a source [or less of a sink] (Cox) and the oceans losing their ability to absorb carbon, leading to decreased permissible emissions for any given stabalisation level of 20-30% (Jones).

  24. 24

    The Florida Current and Gulf Stream transport heat that melts Arctic glaciers and raises sea level. Turbines in these currents can slow them down and reduce the melting while supplying electric power equal to 133% of the peak demand of the combined New York City and Long Island areas. I have details and supporting calculations. Also, a longer article.

  25. 25

    I have no supporting calculations, but for fun — how about wind-powered (tapping the notoriously consistent katabatic flow off the ice caps) snow-making machines on Greenland and Antarctica to sequester the excess oceanic water volume, and thus to thwart sea level rise.

    [Response Building anything on an ice sheet with no base rock is tricky. Turbines tend to ice up over winter and may need lots of maintainence. I haven’t done the calcs either but I suspect that moving the volumes of water necessary would be impractical – William]

  26. 26
    Ajax Bucky says:

    My apologies to Nick Riley #5 and Michael Tobis #4 for the juxtaposition in #13.
    I read right through them both as one.

    Can I suggest a slightly more definite demarcation between comments?

  27. 27
    Grundt says:

    La Rosa, Wetzel, please keep on working on this!!!
    You can help millions of people with these extraordinary ideas.

    It seems so reasonable, and would cost less then sending artifacts to Mars and Saturn, to look not only for information about Solar system , but the possibility to find another place for Humans to live (what I consider a nonsense, since Evolution made us Terrestrians)

    We need repair the Earth before sending a few guys to spoil other planets..

  28. 28
    Bruce Frykman says:

    I am intrigued by the notion that energy consumption always revolves around SUVs that get 20 MPG vs ittty-bitty cars that get 30 mpg. The EU recently trumpeted its 800+ seat A380 airbus to meet the rising demand for world travel. If this is so, then why isn’t the EU funded Airbus consorteum doing everything it can to curtail global travel instead of encouraging more of it. In this regard the IPCC conventioners et al need to come to the 21st century and discovery the energy savings of teleconferencing.

    Capitalism will never produce the needed conservation measures so it is important for governments to establish conservation measures that speak to our individual needs; wages and profits are the instruments of our consumption. Therefore, their levels need to be strictly controllled by government if we are ever to establish acceptable consumption levels to the point where catastrophic global warming can be avoided. Only government and government scientists can establish what individuals should be allowed to consume simply because they are not concerned with wages or profits as the rest of us are; they are therefore the only people who have no bias or ax to grind.

  29. 29
    Hans Erren says:

    RE #22

    Resources will be used until they are gone. To expect a capitalistic world view to do anything different is idealistic.


    Resources will be used until a cheaper and better alternative emerges.
    There is plenty of peat left in Holland.
    Also mercury prices imploded and natural resources are nearly infinite when demand plummeted.

    “The Stone Age did not end because the world ran out of stones”

  30. 30
    Eli Rabett says:

    and Hans, it is not useful to postulate a deus ex machina solution to problems. God may save us, but a lot of people have been hurt betting that way.

  31. 31
    Stephen Berg says:

    An excellent article regarding the Kyoto Protocol and the failure of the US to sign on:

    (Political, but with a scientific summary of the evidence of climate change. Also attacks Inhofe’s and Crichton’s positions and the US government’s cuddling up to the energy industry.)

  32. 32
    Randal Leavitt says:

    Well, if we think that cleaner modes of delivering power will help, then it is falling down obvious that we should be using nuclear fission. It is feasible, inexpensive, safe, clean, robust, and sustainable. Oh yes, it disrupts the flow of money to some established industries based on coal and oil, so we can expect a lot of opposition to its use. One interesting attribute of today’s nuclear power is the complete absence of waste. Fuel goes in the front end, electicity comes out the back end, and the used fuel is stored on site ready to be recycled. Every last gram of material is accounted for, nothing is thrown away, no waste in any sense. This example of cleanliness and safety is something that we are going to have to emulate widely if we plan on making a go of it on this planet. Another thing that I think is neat is that the used fuel is worth more than gold. So your nuclear reactor get more valuable as you use it, by piling up that treasure of reusable fuel behind it.

  33. 33
    Hans Erren says:


    Focussing on neo-Malthusian exponential extrapolations is also not the right answer. A lot of people have been scared that way, and now are becoming indifferent.

  34. 34
    Bruce Frykman says:

    Regarding my previous comment #28, of course it was offerd in jest. However it was seen as fit for publication here by the editors; numerous posts reflecting my state of skepticism re the case for alarmism over the climate have been discarded with no explanation offered. I am puzzeled as to your editorial polity; Do you host a forum or a propaganda site?

    This is offered in the vain hope that this missive will not also similarly be discarded.

    [Response: We are trying to tread a fine line here between inclusivity and relevance, all the while trying to keep focussed on the science. As such, it can be a little subjective (although we are trying to be fair). Nobody’s posts are removed purely on the basis of their point-of-view. Plenty get removed because they start off by assuming that we are all frauds and hypocrites – that is not conducive to a profitable exchange of information. – gavin]

  35. 35
    Eli Rabett says:

    Hmm, Hans, I was not talking about any sort of exponential anything. What I was saying in an indirect way is that magic solutions to difficult problems only appear at the end of movies. Advising folk to do nothing and wait for a miracle because taking ameliorative actions have a cost (we can debate THAT) is not a recommended policy.

  36. 36
    Harel says:

    You suggest that “total collapse” is unlikely, yet it is reported that

    “Professor Mike Schlesinger, of the University of Illinois, reported that the shutdown of the Gulf Stream, once seen as a ‘low probability event’, was now 45 per cent likely this century, and 70 per cent probable by 2200.”

    (G. Lean, Independent of London. 06 Feb 05). Yes, Profe Schlesinger does not equal unanimous or even ‘generally agreed consensus’ however not even mentioning such a serious finding but at least, a serious scientist and participant in the conference, seems to me like you are ‘sexing down’ your story. (I realize global THC does not equal the Gulf Stream, however you did not mention the latter either, and the above quote from the Independent is an important one)

    (As an aside, you seem to delight in beating up on the media — recently unfairly beating on the BBC which was very careful to differentiate between X is known, Y is likely, and Z is only a possibility, though a dangerous one, while your attack suggested they were sensational; if you read the full online transcript, they were quite careful to differentiate X from Y from Z and to use “if true, Prof W’s finding _would_ mean” and so on — I guess I can’t blame you, given the nasty lobby out there working overtime to deny climate change, guess I can’t blame you for being overzealous in trying to make sure you are touch on those who are over sensational, but you go overboard sometimes in that direction. Working too hard to avoid being labeled as exaggerators you end up erring too far and unfairly in the other direction. The above are but two examples. Still, you are a good site with good information, overall, and those of us working to raise awareness appreciate your work)

    [Response:Schlesinger’s presentation describes very simple model experiments and all his assessments are for 2200, as opposed to the coupled model simulations described in IPCC TAR which only go to 2100 – none of which show a collapse by then. This kind of context is essential to get a better idea of what is really being said, and rarely makes it into the headlines. It is not ‘beating on’ the media, to give make this context clearer. – gavin]

  37. 37
    Hans Erren says:

    The SRES scenarios don’t show any difference for the next twenty years, whatever policy we may take, usually the time frame for policy makers.

    But now the world has embarked on Kyoto, a climate UN agreement that has no effect at all on climate and entirely based on a what-if house of cards hundred years away…

    There is still twenty years time for draconian action.

    PS The good news: Polar bear population is increasing.

  38. 38
    Stephen Berg says:

    Hans, the Kyoto Protocol is only a first step in combatting climate change. It is a framework for other agreements that will have to occur if the Earth is to remain inhabitable. And it will have some impact. It will result in some GHG emissions being prevented.

    As for your “draconian” comment, such action may, in fact, be necessary, especially with belligerent governments in the US and Australia on this issue.

    Sure, the polar bear population may be increasing now, but once the Arctic ice retreats, there will be much different migration and feeding patterns and polar bears will suffer greatly. The populations may be growing, but the bears themselves are not. They have never been more emaciated (I think this is the right word) before in recorded history.

  39. 39
    Mike Atkinson says:

    As regards to the polar bear population, it seems to be stable at present. Some populations are increasing some decreasing.

    See the WWF report Polar Bears at Risk. The Cato institute try and rubish this report but I don’t think their critisms add up.

    Some polar bears may be more emaciated but I don’t think there is enough data to say wether this is a global trend.

  40. 40
    Harel says:

    Picking up on comment 36 (and at least I appreciate how like the BBC does at least take criticism seriously and respectfully and I appreciate that) you write that the models in question only give predictions for 2200, however this is not what the London Independent reported; it stated: “Professor Mike Schlesinger, of the University of Illinois, reported that the shutdown of the Gulf Stream, once seen as a “low probability event”, was now 45 per cent likely this century, and 70 per cent probable by 2200″

    Secondly, I fail to see why (as even you concede) partial evidence about a shutdown by 2200 is anything to relax about. By the way I fault the Independent too for hiding the full power of the dangers we face from its readers: it did not ask what the probabilities are for a “partial but significant” shutdown is. Surely the probability is higher than that for a complete shutdown (itself 45% to 70%) Here “partial but significant” is defined to mean, significdant enough to cause ecological or economic serious damage.

    By the way I do not fault you for critiquing what you see as insufficient background given in reporting about the Schlessinger study. However I do fault the blurb at the top of this page for giving the impression that little-or-nothing has changed in the last 4 years vis a vis the “best estimate we have” of Gulf Stream shutdown (complete or significant partial). Clearly this study (as well as another reported in the last 12 or so months on BBC and elsewhere, on alarming measured salinity changes) are such that it’s not fair to state that “little or nothing has changed” in our risk assessment: clearly today we must give higher estimates of these gulf stream risks than a half decade ago. (If you did not intend to have the opening suggest that little or nothing has changed on this gulf stream risk issue, please take this as constructive criticism of *your* reporting ;-) and consider at least a small non-sensational statement next time that several pieces of evidence suggest that risks vis a vis the gulf stream may be higher than the ‘tiny’ risk level previously thought)

    [Response: Firstly, the ‘Gulf Stream’ is not ever going to shut down becasue that is predominantly a wind-driven phenomena, like the analogous Kurishio current in the Pacific. The potential shutdown is of the meridional overturning circulation (or thermohaline circulation), which is but a part of the Gulf Stream transport. Having said that, Prof. Schlesinger’s comments refer to results in his very simple model, which is not a full GCM. Therefore any probabilities quoted need to be weighted by the probablility that these models capture all of the relevant feedbacks (pretty low, in my opinion). Since these kinds of experiments cannot yet be done with the full models, this exercise is of value, but it is not yet a definitive statement. This is one of the most uncertain issues with regard to the future climate, and even with the increased focus on this since the TAR, those uncertainties have not been much reduced, if at all. Thus William’s comment that not much has changed, is valid, because it was uncertain then, and it is uncertain now. – gavin]

  41. 41
    harel says:

    And to add to comments 36 and 40, I somehow missed these important numbers earlier:

    “Curry found that between 1965 and 1995, about 4,800 cubic miles of fresh water – more water than is in Lake Superior, Lake Erie, Lake Ontario and Lake Huron combined – melted from the Arctic region and poured into the normally salty northern Atlantic.”


    “Early calculations show that it would take another 4,300 cubic miles of fresh water from the Arctic to trigger a shutdown of the conveyer belt, Curry said.

    If the thaw continues at current rates, the shutdown scenario would occur in about two decades. What’s worrisome, Curry said, is that the Greenland ice, which hadn’t been melting with the rest of the Arctic, is starting to thaw.

    “We are taking the first steps” toward this scenario, Curry said in a news conference. “The system is moving in that direction.”

    Curry said abrupt climate change was “just possible” but not necessarily likely.
    (end quote from )

    Fine, so it’s “just possible” but a) we have yet more evidence to back the point that we cannot claim that little or no has changed in our assessment versus 4 years ago, on shutdown risks, and b) even if “could occur in 2 decades” (the current estimate) turns out to be wrong (and I’d hate for us to have to “wait to find out” when the cost is so high..) one can hardly take 4,800 cubic miles lightly. Whether “another 4,200 cubic miles” is exact, or a bit over or under, is secondary. Bottom line: responsible reporting should note these are only “possibilities”, yes, but same said responsible reporting should also inform readers that not one but several recent studies change the picture
    (veruss 4-5 years ago) from “remote possibility” to a “higher probability than previously thought” for such shut-down scenarios. That’s what responsible reporting needs to tell people, on page 1 front page news, this isn’t Madonna’s hair we’re talking about.

    -HB (postscript: again one has to ask, if it’s about 4,200 more cubic feet for a shut down, what *smaller* number of cubic feet would it take for “merely” a partial shutdown/slowdown of a magnitude enough to cause substantial weather disruption. You don’t need a 100% shut down to disrupt weather significantly in UK….)

    [Response: More context. The estimates of how much water was released into the N. Atlantic around 8000 yrs ago (potentially triggering the 8.2 kyr ‘event’) are around 2.5 to 5 Sv years ( 1 Sv year is a volume flux of 10^6 m3/s maintained for a year = 3.1×10^13 m3) delivered over 1 year (Clarke et al, 2004). The numbers that Curry discusses are around 0.6 Sv years, over a 30 year period – a volume flux around two orders of magnitude smaller. The climate changes at 8.2 kyr BP were likely associated with a decrease in the overturning (not a shutdown) and led to around 1 or 2 degrees cooling in Europe. – gavin]

  42. 42
    Harel says:

    Firstly, I already made a disclaimer statement in my first, original post, about standard non-science usage of the phrase “Gulf Stream” to refer to what warms UK, so that is a straw man: I already noted the problems with the several terms floating around in articles for lay people versus official terms; in either case a rose is a rose and if the rose is dying who cares what you call it. The response to #41 reminds me of people who point out that in the ancient Earth history one can find co2 far higher than 400ppm, far higher than 500ppm etc. Who cares, when the question is what will be triggered under the human induced (I could throw an “Anthro” in there to sound more impressive, but won’t) climate model. If you have evidence to suggest the figure of “another 4,300 cubic miles of fresh water from the Arctic” would be very unlikely to “trigger a shutdown of the conveyer belt” that would be intersting. Indicating that a completely separate event completely unrelated to fossil fuel burning was probably associated with far higher flux, tells us nothing about whether the present level of danger. (it’s also not as if we haven’t seen other studies on the salinity being yes, significantly changed, e.g. )

    The bottom line is that 5 years ago virtually no one spoke of a shut down other than “in 100 years” or so, and today, serious researchers at respected places like Woods Hole and more than a few others, put a significant risk of such changes within “Decades”. With all due respect to your expertise, nothing you say can obscure these last noted facts. You may argue (even vehemently) against their conclusions (thought Clarke 04 citation here is not very convincing IMO) but even that would not change the fact that serious researchers now unlike 5 years ago, have findings which mean that our risk analysis de facto has changed, and claiming otherwise is not responsible journalism on’s part.

    Remember: this site will be permanently archived. A (short term) protection for you, from the climate change deniers, will, if done by bending over backwards to extreme levels, simultaneously seal a permanent record of irresponsibly under-stating certain risks to humanity, surely not what this site aims to accomplish. It’s a difficult line to walk, I’ll be the first to grant: but taking care to not omit new (yes newly) inferred risks is at least as important as not over stating dangers. Well, I’ve said my piece.

  43. 43
    Harel says:

    ps to gavin: before you slam me for giving a link on salinity speaking of dramatic changes but not giving numbers, yes, I posted another link than the one I meant and can’t find the link w/numbers. Hence we have to make sure with “It’s the most fundamental change [in salinity] I’ve observed in my career,” in the cited link for now

    [Response: Nothing I’ve said should be construed as saying that I don’t think this is a significant issue. On the contrary, I think it is, and I work on this quite a lot. My point is that when talking about ‘low probabilty, high impact’ events such as this, one has to be careful not to over-interpret statements. For instance, ‘It’s the most fundamental change [in salinity] I’ve observed in my career’, is clearly a true statement – but changes in salinity do not need to be very large for this to be true. Measurements are now very precise, routinely to the third decimal place in PSU, and the changes seen over the last 30 years are around 0.05 PSU in segments of the North Atlantic are very clearly significant. However, to connect that with paleo-evidence for THC shutdowns means extrapolating those changes by another order of magnitude – and that is where I might disagree with some of my esteemed colleagues. We started this conversation by addressing the question of whether the additional information over the last 5 years has reduced our uncertainty about the probability of a THC shutdown. Although there is plenty of new information available, I am not any less uncertain about this, because some of the key questions to my mind are still unanswered – what controls the THC response to freshwater forcings? what are the main non-local salinity feedbacks in the North Atlantic? what is the role (if any) of changes in the NAO? Since these answers depend to a large extent on the model you look at, this cannot yet be described as being ‘robustly’ understood. – gavin]