Mother Jones: The Mann behind the Hockey Stick

(deliberate pun in title)

Michael Mann has been interviewed by yet another journalist who didn’t do the background reading. Read it all at Mother Jones

Roger Pielke has done a good job of exposing the politicization of climate science on the Prometheus blog.

I think its very wrong to equate a view on a particular aspect of climate science with a political viewpoint. I know of many people of liberal political views who believe that anthropogenic climate change is minor and probably beneficial, and that the IPCC’s viewpoint is fundamentally flawed – yet for reasons which are now obvious, are viewed as political fellow travellers of the US Republican party or neoconservatives or libertarians. One climatologist told me he was being investigated by a journalist looking for funding from the oil industry because of his "non politically correct views" on climate science (by the way, there’s no money to be found).

30 Comments

  1. Dave Dardinger
    Posted Apr 21, 2005 at 7:51 AM | Permalink

    Well, that Mother Jones article was interesting on a couple of levels. It first of all gives some needed texture to what’s behind Mann’s thinking. It appears that he decided theoretical physics wouldn’t give him a place anymore where he could become well known, and so he moved to climate change instead.

    The second point is that Mann still isn’t quite sure what attitude to take in defending his own work. He wants to take cover behind other members of the team, but also doesn’t want to admit that his own work was wrong so he characterizes M&M as taking cheap shots and that if we just wait all will be made clear in the peer-reviewed journals. Of course he never addresses the actual problems with his work, and certainly wouldn’t consider the various ad homs he’s throwing at his opponents as cheap shots. The same, of course, is true of his blog site. There’s no actual attempt to discuss points of contention with an aim of reaching concensus, but instead an aim of looking good for any of unwashed masses who come along and more importantly any reporters. It’s rather telling that he explicitly says that getting their POV out to the press is a main reason for their blog. It’s also telling, of course, that this blogsite isn’t mentioned. Someone who’s truly objective, of course, would want someone trying to learn the truth to know where to go to get the other side of the story. That you link directly to his blogsite and he doesn’t to yours rather says it all.

  2. John A.
    Posted Apr 21, 2005 at 8:05 AM | Permalink

    I think it’s a definite tactic to marginalize M&M by applying a very large brush to Mann’s detractors as being part of some vast rightwing conspiracy. I think it’s counterproductive and divisive.

    When I’ve looked at other disputes in science, there has been close focus upon the methodology and upon reproducibility. My rule of thumb is: the first person to claim political bias of the other has lost the scientific argument. See for example, this blog entry by someone who is definitely not a political conservative. That guy speaks for me as well – I want to know the whole truth. If Steve is wrong, I want to know.

    When Steve setup the blog, the idea that we should not link to realclimate was seen as infantile. Why shouldn’t Steve link to people who disagree with his results? That realclimate doesn’t engage in any sort of debate does not speak to me that they have a strong scientific case.

    That’s my personal view.

  3. Peter Hearnden
    Posted Apr 21, 2005 at 8:24 AM | Permalink

    John A,

    One minute you accuse the BBC of bias (and unpleasantly ad hom one of their correspondents) the next minute you say “My rule of thumb is: the first person to claim political bias of the other has lost the scientific argument.”. You should practice what you preach – stick to your version of the science and stop the ad homs and the allegations of bias.

    Oh, and btw, this is BBC bias I suppose: http://news.bbc.co.uk/1/hi/sci/tech/4066189.stm ?

    Now, I expect you to unleash the dogs on me! And I’ll probably not get answered but I probably will get called a troll…

    bfn.

  4. John A.
    Posted Apr 21, 2005 at 9:09 AM | Permalink

    Peter, you’d said you were gone for good, but you were wrong!

    You have of course proved my point, since your entire output (including a fascinating comparison between me and Senator Joe McCarthy) is a series of ad hominem attacks as well as other logical fallacies – begging the question, arguments from authority and popularity – that you never bothered to defend. Challenged with the science itself, you have run away.

    I have not made an ad hominem attack on Alex Kirby – I have reported my opinion (well founded as it happens) with his journalistic output, which is extraordinarily slanted. Your link is to one single article that puts the skeptical viewpoint – a gesture never repeated by the BBC. You won’t address any points made in my opinion piece, because I know that you’ll run away rather than address them.

    You probably won’t address the points made by Dr Martin Keeley:

    But for the now-infamous and discredited "hockey stick" temperature curve for the last millennium, used by the Intergovernmental Panel on Climate Change to add body to the case for Kyoto, most observers would not have suspended belief over claims that today’s weather is the "mostest" "on record".

    This expression is simply a lie. We know from the geological (and archaeological) record that weather variations and extremes are the norm.

    Such extremes occur gradually and rapidly, and obviously were not human-induced (anthropogenic). How then can they represent a threat greater than that of terrorism, as the UK’s chief scientist, Professor Sir David King, maintains, except to minds unwilling to accept the inevitability of planetary change?

    Still it’s great to know that you’re still reading the site. I don’t know that we allow dogs on this site – still less that I can set them on people – perhaps you’re afraid of debate?

    I’ll let Martin Keeley finish:

    Global warming is indeed a scam, perpetrated by scientists with vested interests, but in need of crash courses in geology, logic and the philosophy of science.

    It provides the media with a new scare story, which has been picked up by the focus groups and turned into the new religion, offering us hell if we don’t all change our ways. However, believing in anthropogenic global warming is not enough, but that is all it can offer.

  5. Peter Hearnden
    Posted Apr 21, 2005 at 10:41 AM | Permalink

    John,

    I tend to go with the tone (that you partly set here) in a place, but, I’m not going to deny my ad homs if that’s how you saw them…But I see you don’t say of Alex Kirby ‘seem to be slanted’, but ‘*is* slanted’. That is another attack on his integrity, another attack on the man!

    As to the science, well lets be honest I could tell you how I, and many others, see it until I’m fit to drop, and my finger typed down to stumps, but there would be no meeting of mind here. That’s partly why there is so little dissenting comment here I suspect. Why offer dissenting voices here? But I will ask a question: What might convince you the climate has warmed as I think (the .7C or so) and might very well warm by another 2C thanks to our activities in the next 100 years? Answers to that might indicate something we can discuss :) (though I suspect the answer is a resounding ‘nothing’?). My answers to the reverse question would be I would take note of any sustained levelling off or falling of temperatures by any measure, but, like it took decades for the evidence to become comelling to me, the reverse would also take time.

    So, that said, I do not have much I can say really in reply to post #4, bar me not being able to let what to me was clear double standards pass un commeted upon.

    Now, I am going again unless your reply is far, far better than I expect ;) (call it ‘run away’ if it makes you happy…).

  6. Spence_UK
    Posted Apr 21, 2005 at 10:42 AM | Permalink

    That Mother Jones article is the same old arguments trotted out by Mann. He still claims that the satellite data when interpreted “correctly” shows the warming – presumably here he is referring to the withdrawn Fu paper. One would assume that an article dated April 2005, Mann must be aware that the article he is referring to has acknowledged errors? But then Mann will always report flawed science that supports his theories as gospel, and good science that contradicts his theories as rubbish. Such a view is fundamentally unscientific. At least Fu was willing to recognise the criticisms of his piece and make appropriate corrections, the mark of someone interested in the science and not the politics.

    The observations of the infantile behaviour on realclimate (comments #1 and #2) do really stand out. Often realclimate will include a link when discussing a skeptic’s paper – but if you follow the link you just go somewhere else on realclimate with further reinforcements of the same arguments. It is a shame and just goes to prove they have no interest in open debate.

    And Peter is back! I knew you couldn’t keep away Peter, there is just too much truth at this site to be ignored ;) Have you read Wagner et al yet?

  7. John A.
    Posted Apr 21, 2005 at 11:22 AM | Permalink

    Oh dear, I’ll have to go line by line on this one:

    I tend to go with the tone (that you partly set here) in a place, but, I’m not going to deny my ad homs if that’s how you saw them…But I see you don’t say of Alex Kirby ‘seem to be slanted’, but “*is* slanted’. That is another attack on his integrity, another attack on the man!

    It’s good that you don’t try to defend your ad hominme attacks on me because you have no defence. Once again, to attack a journalist whose entire output is slanted is not an ad hominem attack, it is a matter of record. I notice that you in general ascribe negative opinions expressed on this weblog as ad hominems as a way of avoiding the substance of arguments presented.

    As to the science, well lets be honest I could tell you how I, and many others, see it until I’m fit to drop, and my finger typed down to stumps, but there would be no meeting of mind here. That’s partly why there is so little dissenting comment here I suspect.

    There was but they keep running away when challenged. Not much I can do about that.

    Why offer dissenting voices here? But I will ask a question: What might convince you the climate has warmed as I think (the .7C or so) and might very well warm by another 2C thanks to our activities in the next 100 years? Answers to that might indicate something we can discuss :) (though I suspect the answer is a resounding “nothing’?).

    As Steve McIntyre has written, and I concur, that the global temperature (whatever that term actually physically means) has risen by about 0.6-0.7C since reasonably global intrumental readings began in the 1880s. I don’t challenge that, and I don’t know of anyone who does.

    As for the future, this is entirely based on whether the climate models can model the future, about which there is plenty of debate. The IPCC TAR said that future prediction of climate using models is impossible.

    My answers to the reverse question would be I would take note of any sustained levelling off or falling of temperatures by any measure, but, like it took decades for the evidence to become comelling to me, the reverse would also take time.

    Why do I find this difficult to believe? Your claims about 2C warming in the next 100 years are the results of climate models that you believe, not on whether you claim to understand them.

    So, that said, I do not have much I can say really in reply to post #4, bar me not being able to let what to me was clear double standards pass un commeted upon.

    Luke 6:42

    Now, I am going again unless your reply is far, far better than I expect ;) (call it “run away’ if it makes you happy…).

    I’ll call it as I see it, and not ask your permission.

  8. Spence_UK
    Posted Apr 21, 2005 at 11:58 AM | Permalink

    Peter,

    You have once again demonstrated your own myopic outlook on science. You quote top-level, subjective, emotive, politicised statements dressed up as science, yet this site is about the details. Let me explain.

    But I will ask a question: What might convince you the climate has warmed as I think (the .7C or so) and might very well warm by another 2C thanks to our activities in the next 100 years?

    How about we turn that around briefly – what has convinced you that this would be the case? Just reading conclusions and news articles? If some of us are scientifically minded, we might choose to investigate these claims further – and some of us are equipped with the tools and skills to do so. If those of us that dig a little into the results find serious problems with the analysis, are you surprised that this makes us doubt future predictions?

    I will also answer the question from my viewpoint; my answer is I would believe them if someone could first prove to me that they have the capability of predicting the future of climate. All of the evidence (climate being a non-linear chaotic system) would seem to me to support the hypothesis that it is not predictable. There is plenty of evidence that the models do not give a reasonable prediction using non-incestuous testing. The volcanic eruptions commonly cited by the doomsayers found good short-term predictions, i.e. the magnitude of the initial reponse, but poor long-term predictions – the world returned to its original state far quicker than models expected. It seems the models underestimate the robustness of our climate. Imagine that!

    I have explained my viewpoint several times to you, and you have been unable to counter it without resorting to logical fallacies. You have been (it would appear) entirely unwilling to read genuine science that I have pointed you to. Why are you so unwilling to engage in debate? Is it because you have run out of arguments?

  9. Peter Hearnden
    Posted Apr 21, 2005 at 12:56 PM | Permalink

    John, whose entire output *you say* is slanted. There is a big difference.

    Where did the IPCC TAR say ‘that future prediction of climate using models is impossible’. Which page(s) (I happen to have a copy handy)?

    I’m not a bible reader, but I googled your ref and, unsurprisngly, it’s, if I understand bible talk, not a compliment…

    “I’ll call it as I see it” you certainly do.

    Spence, hey, it’s been quiet here, you guy’s need someone to rail at! Have I read Wagner et el? No, but after the post by one of the associated (?) with it I do remember it. I wouldn’t put too much faith in just one paper (cue shrill calls of ‘oh yeah what about Mann 99′ etc etc? It’s not the only one…).

  10. John A.
    Posted Apr 21, 2005 at 1:01 PM | Permalink

    Re: 8

    I think also Spence, that the accuracy of climate modelling depends upon how it is calibrated. If the past climate entered in the climate model is wrong, how can the climate model predict the future?

  11. Peter Hearnden
    Posted Apr 21, 2005 at 1:20 PM | Permalink

    Re #8. Spence, look I make no claims to any more than the most modest of expertese. I’m not a climate modeller. I’m just a bloke who’s allways watched and recorded the weather. I’m fairly intelligent (and clearly interested in all side of the argument), fairly well informed, fairly fiesty, quite happy to put forward my pov, and I’ve flippin’ well been provoked into posting here again darn it:(.

    I think the evidence is good. I think those who say we can model the climate are right – I know they know a lot more than me. I post here on that basis. I’m not utterly convinced, but I do think it’s quite reasonable to say the climate will likely warm by 2-3C (that mid range climate model predictions).

    You don’t think we can model the climate – here you’re not alone. OK, that’s your opinion. Clearly, though, when you bang data into a climate model you get recognisable climate preditions out. A lot of people are doing this, with a lot of models. They all show warming. You may be right and they all wrong. But, and this is just my opinion so don’t all start criticing me *again*, you’re not.

    I’ve read a lot here. I have to say I’m pretty un moved by it all. Again, that’s just my view.

    This place invites comment. I make them – OK?

  12. John A.
    Posted Apr 21, 2005 at 1:30 PM | Permalink

    Where did the IPCC TAR say “that future prediction of climate using models is impossible’. Which page(s) (I happen to have a copy handy)?

    In the Technical Summary of Working Group 1 which you can find here you can find in Section G on “Advancing Understanding” the following (my emphasis):

    Explore more fully the probabilistic character of future
    climate states by developing multiple ensembles of model
    calculations.
    The climate system is a coupled non-linear
    chaotic system, and therefore the long-term prediction of
    future exact climate states is not possible.

    As for the bible quote, I used to be a bible reader and I wanted to test if you’d actually look up a reference and comprehend it. It seemed a reasonable test.

  13. Peter Hearnden
    Posted Apr 21, 2005 at 1:58 PM | Permalink

    Re #12. John, it hinges on the word ‘exact’? Exact doesn’t equate to impossible.

    The quote goes on thus (page 78 ‘Climate change 2001 the scientific basis’) “Rather the focus must be upon the prediction of the probability distribution of the system’s future possible states by generation of ensembles of model solutions.” That sound like an entirely sensible approach to me as of then. It’s this very probablistic approach which make it not exact, and which I would have thought Spence would be with. Exactness probably is impossible, good predictions of probabilities not.

  14. Ed Snack
    Posted Apr 21, 2005 at 2:09 PM | Permalink

    Good Heavens, Hearnden is back and STILL won’t even attempt to look at the data. I challenged you weeks and weeks ago, Peter, to, just for once, look at some actual data, and see if you then considered the treatment of that data was reasonable. Your are disparaged on this site not because of your viewpoint, but because of the way you espouse that viewpoint in the face of contrary data. Sadly that appears to be the only tactic employed by the AGW crowd. The exception was Tom Rees who at least tried to debate the underlying data, unfortunately when faced with some convincing data that contradicted his viewpoint, he disappeared never to comment again.

    You will never be taken as anything other than the resident joke Peter, until you at least once engage with the data being presented and attempt to understand what underlies MBH98, 99, and other the multi proxy studies that purport to show unprecedented 20th century warming. You are, as you say, “pretty un moved by it all” because, although you claim to read it, I would be pretty certain that you don’t understand it. If you did, you could at least offer some informed comment.

  15. John G. Bell
    Posted Apr 21, 2005 at 6:39 PM | Permalink

    Re #12, “a coupled non-linear chaotic system” So scratching my arm pit might result in rain a couple of weeks from now instead of sunshine and a desert instead of a swamp in my backyard in a thousand years? “Long-term prediction of future exact climate states is not possible.” “exact” reduces the sentence to a useless truism.

    One doesn’t quibble when wanting terms defined. “Long-term”, “prediction”, “climate state”. If we extract exact and agree on terms there would be grounds for discussion. As it is, the sentence is useless. John made a mistake in trying to infuse it with meaning. IMHO

  16. Louis Hissink
    Posted Apr 21, 2005 at 10:16 PM | Permalink

    Re #12

    I recall decades ago trying to work out some empirical methods of determing heavy mineral deposition in streams and rivers. All works sort of well if the flow is laminar, but the instant flow reaches a threshold and becomes turbulent, prediction, where exact or imprecise becomes impossible for the various reasons stated here.

  17. Spence_UK
    Posted Apr 22, 2005 at 5:23 AM | Permalink

    Re: #10
    You are correct John – by incorrectly interpreting the past, the tuning of the models will be wrong, and of course by tuning the models to the Vostok ice core and Mann temperature curve any reverse-engineered model (as climate models really are) is simply going to tightly link global mean temperature to CO2 concentration, and projecting those models forward becomes a trivial extrapolation of this trend – even though there are very good reasons not to make such an extrapolation.

    I would say though, that even a flawless record of historical temperatures and CO2 levels would not allow us to predict forward climate with any certainty, and I believe this is the strongest argument against models for prediction.

    Having said that – a true knowledge of historical temperatures and CO2 levels would be useful to illustrate the natural variability of climate, of course, which should help to illustrate the futility of using models as a tool for prediction.

  18. Spence_UK
    Posted Apr 22, 2005 at 5:34 AM | Permalink

    Spence, hey, it’s been quiet here, you guy’s need someone to rail at!

    Most obliged, I am sure :)

    Have I read Wagner et el? No

    Uh-huh, you surprise me…

    ut after the post by one of the associated (?) with it I do remember it

    ? Not sure what this means. Although the discussion with Timme was interesting and constructive – actually looking at the detail of the paper – the paper still strongly supports my hypothesis of highly variable past climate.

    I wouldn’t put too much faith in just one paper

    My opinion is supported by many papers, I wanted to see if you were willing to read just one. Since you aren’t why should I point you at any others? Actually, part of the reason I dangled that particular paper under your nose was that Wagner seems to be an advocate of the global warming scenario, and she actually makes some pro-AGW statements in the paper. I knew you hadn’t read it because, if you had, I expected to see a return of these arguments. It just reinforces my opinion that you have no interest in the technical detail of the science (or perhaps lack the capacity to follow the science?), only in the politics.

  19. Peter Hearnden
    Posted Apr 23, 2005 at 1:23 AM | Permalink

    Spence, “or perhaps lack the capacity to follow the science?”. Fairly typical response to me it seems. Why can’t you people do better than simple insults?

    You should face me, and people like me, with the facts (as you seem them), and keep doing it. Keep it simple, not because I am (but, hey, think that if you like) but because you ought to be aiming at an audience that isn’t expert, and do try to keep calm and civil (Steve M. seems to be able to, follow his example). Resorting to insult just diminshes you (as, indeed it would, and *has*, me at times).

    I’d move on from the obsession with the work of Michael Mann and onto something like the recent Moberg et al. Can’t see it happening though.

  20. John A
    Posted Apr 23, 2005 at 11:33 AM | Permalink

    We’ve already covered Moberg et al.

    Apart from the fact that it refutes Mann’s key notions that
    - the MWP and LIA were not global events,
    - that climatic variation was minimal prior to the 20th Century and
    - the carbon dioxide concentration matches the temperature variation of the last 1000 years,
    its a perfect fit.

    Moberg et al went to enormous length to explain why their results were so different from the Hockey Stick and their methodology superior. The entire curve is as different as its possible to get from the Hockey Stick but guess what? You’ll ignore that as well. Like your "2-3C" claim you’ll never justify it, never look at the data, never engage in the debate at all.

  21. Spence_UK
    Posted Apr 23, 2005 at 5:09 PM | Permalink

    Spence, “or perhaps lack the capacity to follow the science?”. Fairly typical response to me it seems. Why can’t you people do better than simple insults?

    Peter, you seem to be looking for insults where there are none; but quoting me out of context does help to at least partially reinforce your claim.

    My main observation, and only direct statement, was that you were looking at top level conclusions and politics, rather than the detail of the science (which, as I read it, is what this site is primarily about – the devil is in the detail).

    I hypothesised that this might be because you were disinterested in the detail (in which case why post here?) or that you lacked the necessary skills to understand the detail. The words used (“might be” “perhaps”) should indicate to you that I’m only wondering why you are avoiding the detailed scientific discussion, not pointedly claiming I know the reason. (I thought you liked uncertainty?)

    The latter shouldn’t be seen as an insult. Some of the discussion here is very technical, and without a good grounding in statistics one would have difficulty in following some of the detailed arguments, even though Steve does generally communicate his thoughts well. Even so, some of the tests Steve has carried out I have replicated using my own tools (computers and software) which not everyone has access to – this is another example of “capacity to do so”, you may not have the same sort of tools available that I have to compare.

    I’m sure there are things that you could talk about that I would struggle to follow. That isn’t because either of us are stupid, just things that one or the other has little experience of.

    When it comes to statistics, there is a particular issue: in my opinion, statistics is not something that natural intuition or judgement is easy to apply. The same goes for chaotic systems. These things behave in a manner quite inconsistent with how we (humans) naturally perceive they might behave, and because of this unless you have specific understanding/experience/training in these fields, mistakes are prone to occurring. Even “professionals in the field” can make mistakes (just look at MBH98 for a perfect example here).

    You should face me, and people like me, with the facts (as you seem them), and keep doing it.

    I’m really not that interested in persuading a larger majority of my viewpoint. I’m more interested (at the present, at any rate) in testing my viewpoint (and those of others) to clarify my own understanding of climate change. That is really what science is all about – producing theories, hypotheses, models, and then trying to break them. The ones that are most difficult to break are usually give the best available answers. Suffice to say that, (IMHO) on the balance of evidence I have observed, the views of the IPCC seem very fragile. Especially for something that is supposed to be the basis of international environmental policy.

  22. Peter Hearnden
    Posted Apr 24, 2005 at 6:18 AM | Permalink

    Re #21. Yes, ok Spence, I take on board you’re clarification and conciliatory tone :).

    When you’ve just been referred to, in a obviously derogatory fashion, by your surname by others (and had the that bulls**t that i don’t look at any data chucked in your direction *again*) you can see words as yet more insults.

    Right, you do seem to be judging MBH, are you better qualifed than him and thus able to do this?

    Re chaos, try this – http://mustelid.blogspot.com/2005/04/we-cant-predict-weather-week-in.html It’s pretty much the view I’ve expresses here, and been pretty much ridiculed for…Perhaps you also are better qualifed then W Connelley? On both points you might be, I don’t know. I do know I’m not more qualifed the either Mann and Connelley – and I behave accordingly.

    Edit: Remove full stop to allow link to work

  23. Peter Hearnden
    Posted Apr 24, 2005 at 6:27 AM | Permalink

    Re # 20

    Firstly apologies if I’ve repeat posted – I think I might have.

    I think Moberg adds to the sum of our knowledge. The truth *probably* lies within the error bars of the reconstruction*s* I *suspect*. We are now outside those error bars – just.

    Re 2-3C, I think it’s a fair call. I don’t ‘claim’ it, I just happen (since I am suspicious of prediction from either extreme) to think that it’s – *likely*. Do I think we’ll only see a total of 1C warming when we’ve allready seen .7C and anthro ghg’s are only really just kicking in? What do you think I think? Do I think the planet will warm by 11C? What do you think I think?

  24. Spence_UK
    Posted Apr 24, 2005 at 3:49 PM | Permalink

    Re: #22, Re-reading, I realise what I wrote (the way I wrote it) could be taken either way, always a risk when discussions take place on the internet as important cues (tone of voice etc) are lost. Anyway, here is the latest essay I have written in response to one of your posts :)

    Right, you do seem to be judging MBH, are you better qualifed than him and thus able to do this?

    Firstly, let me make things clear here: scientific papers are published with pressures of time and resources. Mistakes get made. It is natural for the author to defend their paper. But mistakes are present and only detailed analysis (through replication etc.) can uncover whether a study "holds water" or not.

    I believe I have the skills and tools necessary to engage in the debate over the authenticity of the hockey stick, at the detailed scientific level. I’m not so familiar with the details of the dendrochronology, corrections etc. but I can replicate the PCA process, and I have to concur with Steve’s findings that there are serious problems with the statistical mechanisms used by Mann. As it happens, I am generally uneasy about the application of PCA to global temperature reconstruction in this way as it can incorrectly invert temperatures (i.e. switch a falling temperature to a rising temperature) if this provides a better "fit", which has no valid interpretation in building a global average temperature.

    With regard to Professor Mann’s skills, I noted that his code included peculiarities that – whilst not introducing significant errors – were odd things that I would not expect a seasoned statistician to get wrong. For example, at times he calculates population standard deviation when he should be using sample standard deviation. All these things fall into the category "trivial errors of little consequence" but someone with a solid statistical background probably ought to do these things correctly without even thinking about it. At the end of the day, nobody has a monopoly on being right. We all hold our own views.

    As for your chaos link (the link didn’t work for me, but copying and pasting does – (unfortunately you can’t edit, so you’ll have to appeal to John A’s kinder sensibilities to get it changed ;) ), that is a rather pat discussion of the topic in a blog. Sure, it is aimed at people who are not interested in the detail, but it leaves me cold I’m afraid. I could explain my full views on that posting but my comments here are long enough as they are and such a response would probably go to several pages!!!

    As a taster though, he should have introduced the requirements for a chaotic system as identified by Lorenz: a system containing two (or more) interacting variables (i.e. feeding back to each other’s future value). The prediction of the tides is a bizarre and inappropriate comparison, since tides are dominated by a single parameter (the orbit of the moon) which is a well known quantity and essentially independent of any other variables that may influence the tides. Whilst the relationship is complex, the lack of interaction (or feedback) is key to the predictability. For this reason, we can identify the tides as "probably not truly chaotic in nature", which would explain why they are so predictable. Can we say the same about climate?

    Climate is different – there are many interacting parameters. For example, just take carbon dioxide concentration and temperature. The greenhouse phenomena is well known: increase CO2 concentration and (to some unknown degree), temperature should increase. But as temperature increases, the CO2 concentration equilibrium shifts as bio matter and the seas shift their respective sources and sinks. So we have two interacting parameters. Of course this is a huge simplification; once we add other feedbacks and forcings, we find the whole system very complex and almost certainly chaotic in nature.

    Once we recognise chaos, we must accept that when we try to predict into the future, there will come a point when the errors in our models become as large as the signal being measured (even if they are well tuned and captured all of the salient feedbacks – which current models aren’t and don’t). I maintain that there must be a (fairly high) finite probability that the global mean temperature in 2100 will be at the same level as it is today, irrespective of what our current models esimate. I would be hugely suspicious of anyone who claimed otherwise unless they had a very good justification.

    Edit: Changed formatting in this reply after Spence failed to close a “blockquote” correctly. I never realised I had a better nature, being wholly evil according to some.

  25. Spence_UK
    Posted Apr 25, 2005 at 7:36 AM | Permalink

    Thanks for the correction to comment #24 (John?), I really must proof read my feature length comments before posting them up!!!

    John replies: No problem. I needed to express my evil McCarthyite tendencies anyway…

  26. Peter Hearnden
    Posted Apr 27, 2005 at 2:17 AM | Permalink

    Re #24

    Ok Spence, I think you are qualified to comment, but I still think you not right. Perhaps I’ll explain, fwiw, why I think this though my qualifications are far less (and before you trash me for not being qualifed remember many here are trying to trash people better qualified than they are – OK?).

    I think it’s clear the climate (and the weather) operate within limits. The weather may not be usefully predictable beyond a week or two (other than, say, it’s not going to be -10C in London during July) but the climate is more so (to my mind) since it the average of weather and easier in a way to predict. Thus the UK temperature varies from say -10C to +30C each year, and perhaps 20C a day at times, it’s yearly climate only varies from, say, 8C to 11C. So this whole ‘weather and climate is chaotic’ business seems strange to me. I’d rather think that there are limits to our ability to usefully predict the weather, but that, since climate is ‘bigger’ the limits with climate are ‘bigger’. We also *know* that you can predict the temperature of the Earth’s surface (broadly it’s climate) using quite simple formulas and get a very good result, no such formula exists for the weather…

    That’s how I see it anyway. So, for my mind to change, what I need is someone to convince me that weather and climate (which *are* different things) are not different in terms of predictability – how? Or, indeed, perhaps I’d need convincing that climate is *less* predictable than weather since climate is obviously ‘longer’ than weather. Neither seem likely to be so shown me.

    The views in this document seem right to me – http://policy.iop.org/Policy/Climate%20change%20models.pdf

    Re full stops, seen that elsewhere, I should have spotted it…

    Finally, who has called you evil John A? You clearly are not. I don’t agree with you, or you with me, that doesn’t make you evil or *anything like it*!!

  27. Spence_UK
    Posted Apr 27, 2005 at 4:27 AM | Permalink

    Peter, I thought you’d given up on me, but then with a comment as long as #24, you’d be forgiven falling asleep half way through ;)

    The natural variation of temperature due to the seasons is another interesting observation, and the predictability of this is often cited as an example of how we can predict climate. Again, my thoughts on this with regard to chaos and predictability:

    The seasons are driven by the tilt angle of the earth’s rotational axis with respect to the sun. During April-September, the earths rotational axis is tilted such that the Northern Hemisphere is tilted towards the sun. During October-March, the axis is tilted such that the southern hemisphere is tilted more towards the sun. Coupled with this, the earth is also closer to the sun in the Oct-Mar time of the year, making the SH summer and the NH winter warmer; the NH summers and SH winters are cooler. This is an important part of climate.

    When we consider the relative feedbacks here, we can see that the geometry of the earths orbit around the sun is driving climate, but climate has no way of influencing the geometry of earth’s orbit. No feedback means a non-chaotic system, which means (by my measure) this should be a predictable system.

    So a significant part of the climate signal is quite predictable. The impacts of solar forcings similarly have little feedback and remain predictable (although predicting the level of solar activity is another story) But not all of climate falls into this category.

    I have still yet to be convinced that climate associated with the forcings and feedbacks of earth’s atmosphere is not chaotic. It is possible for a non-linear multi-parameter system with feedbacks to be non-chaotic and predictable, but as a rule of thumb they should be assumed chaotic until demonstrated otherwise.

    I appreciate that these papers claim that the system is chaotic but the chaos can be reduced through averaging. This goes against the grain of my own experiences of chaotic systems. I have already mentioned professor Thorpes paper in comment #6 of this thread. There are two issues at stake here: it does not consider time lapse, which is critical in a chaotic system. All chaotic systems carry some “inertia” and as such have some “predictability” in the short term, as a probability spread. The further into the future one looks, the less predictable it becomes. The second problem is that of multi-scale variability; with predictable and repeatable systems, one can observe a signal over a period of time and average to remove random noise imposed on the signal to improve the signal to noise ratio. This does not apply to chaotic systems (or fractals) due to multi-scale variability. Essentially, to perform an average, you need to increase the observation period, but to do so you include a different underlying signal. The averaging process does not move towards a meaningful result.

    [Irrelevant side note on averaging, and popular statistician's joke: did you know that almost the entire population of UK humans has more than the average number of legs? OK I say joke but this is by scientist standards]

    Anyway, enough from me for now (before this becomes another 15 pages), I can see we are unlikely to agree on this topic, although it is always interesting/useful to share opinions.

  28. Michael Ballantine
    Posted Apr 27, 2005 at 5:21 AM | Permalink

    Spence, [Irrelevant side note on averaging, and popular statistician's joke: did you know that almost the entire population of UK humans has more than the average number of legs? OK I say joke but this is by scientist standards] ROTFLOL. I love it. That is a new one for me. Guess I haven’t spent enough time on your side of the big pond. Did you hear about the education official in California who complained that despite all their efforts it was unacceptable that half the students in California were below average? Sadly, this is a true story and not a joke.

  29. John Davis
    Posted Apr 27, 2005 at 9:01 AM | Permalink

    My thanks to Peter H for the link to the Thorpes paper – it’s a very nice summary of “the state of the art”, and there’s a lot in it I have yet to digest (or otherwise). So far my normal state of mild skepticism about the degree of AGW – and my extreme skepticism about the proposed action to reduce it – remains unruffled. I’d like to make two minor points though; firstly it is in both the personal and professional interests of the author (and probably the corporate interests of the institute of physics come to that)to emphasise the risks and reality of AGW. Secondly that I tend to mis-trust obvious rhetoric like
    “society is increasingly vulnerable to climate
    change both because of the huge increase in the total
    population and because of the way it organises itself.”
    In fact, as societies become wealthier they are better able to afford to deal with change of all kinds. The societies most at “risk” are those with least resources, who will arguably be most disadvantaged if Kyoto and its successors put a serious brake on global wealth creation.

  30. TCO
    Posted Sep 18, 2005 at 5:45 PM | Permalink

    1. Mother Jones!!! Sheesh…that is the extreme left wing!

    2. Mann moving from physics is not that unusual. It is common for those guys to try to use their math skills in other fields. They’ve invaded biology and even sociology. Actaully makes me think of him a bit like Steve.

    3. I agree that the “team cover” is kind of cheesy. Not willing to admit your own work is wrong, but trying to deflect examination. It’s a girly evasion.

Follow

Get every new post delivered to your Inbox.

Join 3,381 other followers

%d bloggers like this: