Tuesday, August 17, 2010

Defending fairy dust

'Hypothetical thing thought to have special powers'
Last week this blog briefly described the involvement of local scientists in support of evidence for human influence on global warming.  Paleoclimate studies have played a key role in persuading policymakers that global warming is a serious threat.  There are many other arguments which have been used but none has been quite so emblematic as the hockey stick, a product of the paleoclimate community.

Launched by Michael Mann and two co-authors in papers in 1998 and 1999, the work purported to show that temperature had been more or less flat for the past 1,000 years until the second half of the twentieth century when there was an alarming spike - the (ice) hockey stick.

Criticisms of the quality of the work centred on two issues.  Some of the data, it was alleged, had been cherry picked to create a hockey stick, and the statistical methods used in analysing the data were flawed.

The response of Michael Mann and the paleoclimate community was to defend the 1998 (MBH98) and 1999 (MBH99) papers with a plethora of further peer reviewed papers which endorsed the original claims usually claiming to be independent.

I have been looking the Wegman Report, a five year old publication for a US Congressional Committee. Compiled by Edward Wegman, a respected academic expert in statistics. The report was devastating:

"In general we found MBH98 and MBH99 to be somewhat obscure and incomplete and the criticisms of MM03/05a/05b (the critics) to be valid and compelling. . . Our findings from this analysis suggest that authors in the area of paleoclimate studies are closely connected and thus 'independent studies' may not be as independent as they might appear on the surface.. . . In this case we judge that there was too much reliance on peer review, which was not necessarily independent. . . Overall, our committee believes that Mann's assessments that the decade of the 1990's was the hottest decade of the millennium and that 1998 was the hottest year of the millennium, cannot be supported by his analysis."

That all seems clear.  Yet peer reviewed paper after peer reviewed paper has been produced by the paleoclimate community supporting Mann's original analysis.

Take a local example.  In  December 2009 the Royal Society of Edinburgh produced a briefing paper aimed at the then forthcoming Copenhagen Climate Summit which was also 'intended as a helpful summary for the Scottish Government and Parliament, for public and private bodies, and for fellow citizens.'

In this document  the claim is made:
Several independent estimations have now been made of the global or hemispheric average temperatures for the last two millennia. Figure 3 is one of these, and shows that the late 20th Century warming has been rapid and large compared with earlier periods (note that this is independent of the University of East Anglia reconstruction, about which there has recently been much controversy).
Figure 3 refers to Hegerl et al 2006.  I wrote about Gabi Hegerl last week as being an Edinburgh members of the paleoclimate community.  In Wegman's terms she is not independent of Mann.  Nor is the paper cited independent from MBH99 or 'the University of East Anglia reconstruction about which there has been much controversy'.  A more detailed analysis of this false claim by the Royal Society of Edinburgh, and of the deficiencies of Hegerl et al 2006, can be found here.

This week a peer reviewed paper has been published in the Annals of Applied Statistics.  McShane and Wyner 2010 weighs in to the issue of the statistical methods used.
Research on multi-proxy temperature reconstructions of the earth’s temperature is now entering its second decade. While the literature is large, there has been very little collaboration with university level, professional statisticians (Wegman et al., 2006; Wegman, 2006). Our paper is an effort to apply some modern statistical methods to these problems. While our results agree with the climate scientists findings in some respects our methods of estimating model uncertainty and accuracy are in sharp disagreement.   On the one hand, we conclude unequivocally that the evidence for a "long-handled" hockey stick (where the shaft of the hockey stick extends to the year 1000 AD) is lacking in the data.  
In other words, these authors consider the previous reconstructions purporting to show that the late twentieth century warmth is unprecedented in the last millennium are unsupportable.  In doing so McShane and Wyner take a position which is consistent with the analysis of Wegman as well as the critics who had first challenged the Mann and University of East Anglia claims.

Of course the above doesn't prove that recent temperature increases are not unprecedented.   All we know from the above is that some of the evidence upon which these IPCC claims have been based -  is fairy dust.

How much of the remainder of the 'evidence' is bogus?

And why have the paleoclimate community and scientific advisers to our governments been defending fairy dust for the last five and more years?

Finally, here is a comparison of the discredited hockey stick from Mann and the temperature reconstruction attempt by McShane and Wyner.
Mann version of the hockey stick

McShane & Wyner version


  1. Wegman, at most, shows that Mann's conclusions are not backed by his own research. He doesn't show that Mann's conclusions are incorrect. Other scientists have looked at both the original work and the criticism and have generally sided with Mann - albeit with reservations.

    I should also point out that other research by various methods overwhelmingly supports an anomolous increase in temperature in recent times.

    Finally we need to remember that temperature rise is the presumed consequence of change, not the cause of it. The presumed cause is carbon dioxide that is present in our atmosphere in indisputably unprecedented proportions. The current temperature rise is manageable. It may not be manageable if it rises in proportion to the levels of carbon diaoxide, as it has done in the past.

    clear that scientists on both side

  2. FF

    I appreciate your comments.

    Certainly, I agree with your first para. As I understand it there are two issues. First there has been a defensive operation by Mann et al to rubbish the criticisms. It has often seemed that valid and significant criticims are not accepted. Yet MBH98 and MBH99 have been seminal to the development of public policy. Second, the 'other scientists' phrase lacks specificity. Doubtless you are correct. But to whom does it refer? Such as Wahl and Ammann 2007 with all the shenanigans associated with their work? The problem is that the appeal to the authority of a majority of scientists, or to the experience of climate scientists is no longer a credible line of evidence. That is one of the outcomes of the misconduct in this field. The weakness identified by Wegman of 'close connections' amongst a limited circle of scientists leading to apparent but not actual independence, is relevant here.

    2nd para. I am not inclined to doubt an anomolous increase in temperature. But I do note there is increasing evidence of flaws and uncertainty in some of the methods used to calculate and present that anomoly.

    Finally, your third para. 'presumed. . . presumed. . . unprecedented'. I note your measured representation of uncertainty. Perhaps the 'unprecedented' refers to more recent times.

    All noted thanks.

  3. Cameron, I can think of four grounds why we might challenge Climate Change Theory:

    1. The planet isn't actually warming at all.
    2. Even if it is, there's no reason to believe man has anything to do with it.
    3. Even if man is causing climate change, we shouldn't believe it to result in sudden, irreversible and catastrophic change, as the standard model predicts. It could be gradual and manageable.
    4. Let's assume doom is around the corner. The proposed remedies won't prevent it happening.

    I observe that most challengers focus on points 1 and 2 when I would have thought point 4 and, perhaps, point 3 would be more rewarding.

    You say "the appeal to the authority of a majority of scientists ... is no longer a credible line of evidence". But surely that's the only sensible way of deciding public policy? You will always get dissenters - academics are paid to argue after all - but when you are trying to find the best policy for the most people, you will be informed by the majority thinking. So we start from the assumptions that smoking causes premature death, that a single MMR vaccine saves the most lives, and in this case, that man's behaviour is causing the climate to change - because that's what most scientists believe, even though there are dissenters on all these points, as well as scientists who have agendas for both sides of the argument.

    I should stress that the scientific consensus for man-made climate change is as firm as it gets. The vast majority of scientists who have looked at the issue have come down on the side of man-made climate change because in their view the evidence stacks up, and not because they are part of a huge conspiracy.

    Put it another way, it’s surely much less credible to dismiss a theory and change a public policy simply because someone believes an individual scientist to have been careless, biased or dishonest? Instead we should argue from first principles and try and win around the consensus that most informed scientists without an agenda currently hold. Unfortunately most challengers just attack their opponents rather than putting forward compelling arguments of their own.

    On point 3, the idea that climate change will be sudden, irreversible and catastrophic is definitely open to challenge. No-one knows the future and we’re in an unprecedented situation – ie CO2 levels - so the past is no guide either. But there’s an issue here too. Given that sudden, irreversible and catastrophic change is as a plausible an outcome as a gradual and manageable change, wouldn’t it be a bit irresponsible to assume the more benign outcome is the one that will actually happen? If we don’t know, shouldn’t we plan for the worst?

    Point 4 – what to actually do about climate change is wide open, however. We’re out of the scientific realm at this point and in the world of politics.

  4. This comment has been removed by the author.

  5. Thanks again for your thoughtful reply.
    Personally. . .
    1. I've already noted I think it very likely it is.
    2. It is not all or nothing. People like Prof Richard Lindzen (MIT) suggest the human influence is there but is exaggerated.
    3. The uncertainty is very considerable.
    4. I'm not sure of the efficacy of many of the proposed remedies. Some of them are clearly fairy dust.

    On the 'appeal to authority', can I respectfully suggest your argument is essentially flawed. Since when did a majority make something right? Majority thinking may make something politically achievable but it does not make it true. Evidence is what is needed - which is why I have tried to the best of my ability to look at the grounds used to justify public policy. Public policy is littered with decisions which in retrospect can be seen to be wrong.

    And I am afraid I have to disagree with you on the consensus paragraph. First, I don't think it is helpful to paint the issue as whether or not there is a conspiracy. I think one commentator suggested 'unintended groupthink'. Wegman addresses this issue helpfully as well. Then your use of scientists 'who have looked at the issue' is problematic. Which scientists have looked into the issue? Those who agree with a certain conclusion? I can hardly believe you are up with the current literature and debate with your first sentence in this para. There is a whole range of thoughtful debate below the parapet of mainstram media, government policy and CRU and climate change establishment figures. I suggest you review your statement after reading McKitrick or Montford's review of the Climategate enquiries. What of Lindzen, McIntyre, Singer, Pielke? Have you read the Hockey Stick Illusion? Perhaps I have judged the debate wrongly but you don't have to look far to get evidence that the 'consensus that the science is settled' seems to be only amongst certain classes of people.

    Your comment about an 'individual scientist being careless' etc. does not seem to put the debate on the CRU in proper context. CRU and a relatively small group of other such establishments and people have been hugely influential in shaping how the science is percieved (especially thorough the IPCC reports)and, consequently public policy. This is not a matter of one or two scientists who have made a mistake.

    I note your 'precautionary principle' comments on point 3. Unless, of course, the precautions taken (Stern?) turn out to be more damaging to the people we are trying to save from negative consequences of global warming. There is plenty of work which challenges Stern and others who load their calculations to a more alarmist conclusion - and there is a strong moral argument about doing current good (with some certainty) as opposed to future perceived good (with significant uncertainties).

    Last word here to Prof Michael Kelly Electronics, Cambridge Univ, in relation to confidence in models (ground 3 above):
    "I take real exception to having simulation runs described as experiments (without at least the qualification of ‘computer’ experiments). It does a disservice to centuries of real experimentation and allows simulations output to be considered as real data. This last is a very serious matter, as it can lead to the idea that real ‘real data’ might be wrong simply because it disagrees with the models! That is turning centuries of science on its head."

    Thanks again for your time. Forgive me if I have assumed views from your words which are not you views.

  6. Cameron, you have summed up my views accurately and addressed them in a way that gives much food for thought. I think we'll need to agree to disagree on the facts of climate change (as opposed to the theory and policy points). Those challenging Climate Change Theory are just as likely to be biased as those promoting it. We have to deal with an imperfect world and competing agendas, so what the main body of informed opinion thinks does matter in my view. They are testing the various theories and are coming down firmly on the side of those that believe that man made climate change is real, significant and happening now.

  7. FF
    Since my last response, I have read the analysis of the enquiries produced by Montford (link in my 11:10pm post on Tuesday 14th September). As we bring this exchange to an end I urge you to read it. It might inform how one assesses 'the main body of informed opinion'.

    Best wishes and thank you for your courteous and thought provoking exchange.