A critique of Wood on global warming
I’ve been sent a critique of Alan Wood’s piece in the Oz claiming that global warming is a hoax. It’s written by a climate scientist who knows what he is talking about on this issue. Wood obviously doesn’t know or doesn’t care.
I was very disappointed in Wood’s piece. While his economic views are very different from mine, his columns on economic issues are usually rigorous, and if he makes a factual claim, it’s generally reliable. But his standards seem to desert him when he writes on this topic.
The response is in the (now relatively uncommon) form of a point-by-point fisking. Wood’s text is in plain type and the comment’s in italics.
One fairly trivial point is quite revealing. Wood claims, incorrectly, that the Mann “hockey stick” graph was “for a time, incorporated … into the IPCC’s logo.” As the analysis makes clear, the repetition of this bogus factoid indicates that Wood is sourcing his material from the denialist echo chamber, and not doing his own research. This is standard practice for our legion of rightwing hacks (and quite a few lefties as well), but it’s not the kind of thing I’d expect from Alan Wood.
Debate on climate change far from over (Alan Wood, Australian 91/7/06)
with a critique by Roger Jones*
*The views expressed here represent personal opinion based on assessing a wide a range of sources, professional experience in assessing both past and future climate, and do not represent the position of any organization
AT lunchtime on Monday, John Howard and Victoria’s Steve Bracks were on their feet talking about energy, climate change and the environment. While their approaches were notably different, there is one thing on which they both agree: the UN’s Intergovernmental Panel on Climate Change is the font of all scientific wisdom on global warming.
In fact it has become quite fashionable of late to assert the global warming debate is over and an overwhelming scientific consensus prevails. This is simply untrue.
As acknowledged in an Australian Bureau of Agriculture and Resource Economics report on climate change scenarios, also released on Monday, there are still considerable scientific uncertainties surrounding the nature and extent of future climate change.
This is what ABARE said in their report on Monday:
It is important to recognise the current scientific uncertainties surrounding the nature and extent of future climate change and the likely impacts thereof. Hence, a sensible approach to climate change must involve a reasonable balance between multinational action to mitigate future emissions to meet given concentration or temperature change targets and the necessary adaptation policy measures to cope with any unavoidable potential climate change impacts.
Of course, no-one can argue against taking a sensible approach. The IPCC offers full descriptions of the scientific uncertainties known to about 2000 in their Third Assessment Report. This is a red herring as to whether global warming poses serious risks or not. The â€œexpertâ€? consensus on whether global is real does not gainsay the uncertainties, quite the contrary.
A report released in the US on Friday has torn apart one of the main props used by the IPCC to illustrate the need for urgent action on climate change. The report raises serious questions about the IPCC process and the findings on which world governments rely in forming their climate change policies.
First, some background.
In telling the global warming story the IPCC, since 2001, has relied very, very heavily on what has become known as the “hockey stick”. It is based on a 1999 paper, the principal author of which was paleoclimatologist Michael Mann.
Before the publication of his paper the generally accepted view of the past 1000 years was that there was a period of elevated temperatures known as the Medieval Warm Period, which was followed by the Little Ice Age, and then a new period of global warming.
Mann’s hockey stick eliminated the Medieval Warm Period, flattening the fluctuations in global temperatures over most of the past millennium (the handle of the hockey stick) until we get to the 20th century, where the rate of global warming takes off in a sharp upward surge (the blade of the hockey stick).
There are several errors of fact here:
â€¢ They are not global temperatures, they are the northern hemisphere only
â€¢ It did not eliminate the medieval warm period but it is flatter than far more localised records
And of interpretation
â€¢ The IPPC did not rely very, very heavily on the â€œhockey stickâ€?. It was a statement in the Summary for Policymakers (SPM) that approved by all governments. It was one dot point of many and one panel of a single figure of five in the SPM.
This is the basis for the IPCC claim, now widely accepted, that the 20th century was the warmest in the past 1000 years, the 1990s were the warmest decade in the past millennium, and 1998 was the warmest year in the past 1000 years. Scary stuff!
What the IPCC said was this: New analyses of proxy data for the Northern Hemisphere indicate that the increase in temperature in the 20th century is likely to have been the largest of any century during the past 1,000 years. It is also likely that, in the Northern Hemisphere, the 1990s was the warmest decade and 1998 the warmest year (Figure 1b). Because less data are available, less is known about annual averages prior to 1,000 years before present and for conditions prevailing in most of the Southern Hemisphere prior to 1861
In this case likely gives a level of confidence to that statement that it is 66â€“90% of being true, i.e. more than twice as likely as not, but not highly likely to be true (>90%).
This is a statistically verifiable sequence if one believes the first statement, because if the latter 20th century is the warmest period and the 90s the warmest decade and 98 the warmest year, the likelihood of a departure that large from a cooler previous period is exceedingly remote. So for the NAS to find the latter less plausible than the former, does not make much sense. This type of analysis can be seen for Svalbard/Spitzbergen here:
Two Canadians, Steve McIntyre, an engineer, and Ross McKitrick, an economist, challenged Mann’s work in 2003. They argued his technique produced hockey sticks from just about any set of data. Mann responded in a notably less than scientific manner by withholding adverse statistical results and important data, and discouraging the publication of criticism of his work.
Mann was cranky but did not prevent their access. He challenged them to reproduce his method from the science and declined to hand over his analytic code.
A Wall Street Journal report of the controversy last year attracted the attention of the US House Committee on Energy and Commerce. It wrote to Mann and his co-authors, as well as to the IPCC, demanding relevant information and then approached independent US statisticians for advice on assessing the data provided.
Leading US statistician Edward Wegman, of George Mason University, who is chairman of the US National Academy of Sciences’ committee on applied and theoretical statistics, agreed to assemble a group of statisticians to assess the Mann data. Their report was released last Friday and supported McKitrick and McIntyre’s criticisms of the hockey stick, finding Mann’s statistical work flawed and unable to support the claims of the hottest century, decade and year of the past millennium.
The Wegman et al. paper is interesting but for the wrong reasons: It summarises palaeoclimatic proxies and carries out an analysis of how to produce hockey sticks from random data. They did not produce a bootstrap analysis of the data used by Mann et al., which would prove that the hockey stick through Mann et alâ€™s analysis was or was not an artifact. They merely showed that the analysis could produce spurious results, not that it did. The corroborating scientific analyses produced since (by scientists that were unrelated to Mann in Wegman et alâ€™s analysis) show that underlying data was not red noise.
The social network analysis is highly flawed. It all hangs on the following statement: In particular, if there is a tight relationship among the authors and there are not a large number of individuals engaged in a particular topic area, then one may suspect that the peer review process does not fully vet papers before they are published. Indeed, a common practice among associate editors for scholarly journals is to look in the list of references for a submitted paper to see who else is writing in a given area and thus who might legitimately be called on to provide knowledgeable peer review. Of course, if a given discipline area is small and the authors in the area are tightly coupled, then this process is likely to turn up very sympathetic referees.
So one may suspect peer review does not fully vet papers and it is likely that the reviews will be sympathetic. That word likely is the same one that the IPCC used to say that the 20th century Northern Hemisphere warming was the largest in the past millennium and that the 90â€™s were the warmest decade and 1998 the warmest year. So, without any foundation, suspicion and likelihood is attributed. To then link the Mann network which is a close network, with the palaeoclimate reconstruction network, which is not, the authors use common data sets of temperature proxies. This is like accusing economists of collusion when they use the same GDP data. Wegman and his colleagues manage to gainsay recent debates that have surrounded the use of peer review. Those debates have been widely publicized and have concluded that it is not flawless but is the best method going.
The recommendations about the IPCC and how it operates come with no analysis in the report, and thus there are no grounds for the recommendations the report makes. The report attacks the whole notion of peer review both within science and the IPCC without a shred of evidence.
That they want to involve statisticians in ongoing work is interesting. What level of education in statistics does one need to have? Skill in statistics does not mean a better understanding of science or even uncertainty. For example, Bjorn Lomborg in his book The Skeptical Environmentalist notoriously misrepresents the underlying science contributing to a range of environmental risks (not to mention his selective use of statistics). Ian Castles also, attacked the IPCC SRES scenarios on statistical grounds, without showing that the underlying assumptions relating population and energy use were in fact incorrect. The idea of using statisticians without training and a publication record in the relevant science, or as an integral part of a larger team should not be given air. However, more resources would also be required to fund the greater scrutiny if it were applied. My own experience in the current funding environment is that the biggest restriction to peer review is resources. I apply a skeptical filter to the papers I review and to my best knowledge, so do my colleagues. However, peer review is a gift economy that does not sit well with targeted funding.
What the Wegman et al. report does not do is assess the scientific nature of Mann et al.â€™s work and whether it has been supported by other research (although it summarises some of that research).
In his article Wood also overlooks a National Academies of Science report published in the previous week that does address the science. http://www.nap.edu/catalog/11676.html
However that report was not conclusive on the matter of the hockey stick. The NAS report says:
Not all individual proxy records indicate that the recent warmth is unprecedented, although a larger fraction of geographically diverse sites experienced exceptional warmth during the late 20th century than during any other extended period from A.D. 900 onwards. Based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium. The substantial uncertainties currently present in the quantitative assessment of large-scale surface temperature changes prior to about A.D. 1600 lower our confidence in this conclusion compared to the high level of confidence we place in the Little Ice Age cooling and 20th century warming. Even less confidence can be placed in the original conclusions by Mann et al. (1999) that “the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium” because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales.
The report confirmed that the latter part of the twentieth century was warmer than for the previous 400 years but ducked on extending this conclusion to the last millennium despite the attribution of plausibility above. However, that the larger fraction of sites showing that a warmer 20th century has occurred suggests that the â€œwarmest period over the last millennium in the Northern Hemisphereâ€? could only be false if some contra-indication was introduced into the numbers and analysis (this allows also for area-weighting of the data).
The NAS report has been claimed as vindication by Mann and his supporters and also by McIntyre and McKitrick and their supporters. Why is this so?
By not quantifying their levels of confidence in these conclusions the NAS committee has allowed the reader to interpret this information in any way they see fit. But, they do not say that Mann et al.â€™s statement was implausible. The inference is that it is difficult to verify on the available evidence.
However, the committee does say that support evidence exists for the statement that warming during the late twentieth century is more spatially coherent at any other time since the 9th century A.D. and the larger number of sites shows exceptional warming. Given that the committee found itself unable to clarify any levels of confidence in their findings, or even come to any conclusions as to whether simple or area-weighted averages were preferable to determine areal trends, the whole report does little to clarify an issue where entrenched views that have little to do with the science of palaeoclimatology abound.
The NAS report suffers by not treating uncertainty and confidence in any rigorous manner, so has served to muddy the debate rather than clarify it. People will interpret words like likely, plausible and less confidence but still plausible in the way they see fit if not provided with internally consistent methodology and guidance. In its Third Assessment Report, the IPCC introduced methods to quantify and clarify uncertainty and confidence. Although not perfect, this development should now be seen as best practice in communicating contentious issues. It is a pity that the NAS does not do this.
Yet the IPCC used the hockey stick in its publications, media releases, press conferences – where senior IPCC figures sat with the chart as a backdrop – and, for a time, incorporated it into the IPCC’s logo.
This last statement is patently untrue. McIntyre wrote on Prometheus (Roger Pielke Jrâ€™s blog) It could almost characterized as the logo for IPCC TAR. Figure 1 below shows Sir John Houghton, at the press conference releasing IPCC TAR, standing in front of the Hockey Stick. The graphic was used repeatedly in IPCC TAR and was one of the most prominent graphics in the Summary for Policymakers. http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/000630does_the_hockey_stic.html
By the time Wood gets the Chinese Whisper, the hockey stick has graduated onto IPCCâ€™s logo. This misrepresentation of the logo has been repeated on a number of web sites.
As to the use of the graph, the IPCC uses a range of signature graphs. Communication is its business.
It is important to understand that this is a debate about the use of statistics. Mann did no original scientific work, using available data and manipulating it in a new way.
The work was original. This comment implies that experiment and measurement is the only original thing you can do. This debate should be about science â€“ statistics is a tool. It is possible to use a tool poorly and come up with the right answer and also to it well and be wrong.
However, it destroys the idea of an alarming escalation in global temperatures and, as the Wall Street Journal remarked on Friday, brings the present temperature rise within the range of natural historical variation.
No it does not â€“ plenty of other studies confirm high 20th century warming. The evidence is not only trend but â€œfootprintâ€? and has been confirmed by modeling. AGW produces very different spatial patterns to hemispheric warming.
There remains plenty of room for argument about the projections of future temperature rises and their implications, based on what are still primitive climate change models. But there is no escaping the damage done to the IPCC’s reputation. It has relied heavily on a badly flawed piece of work, produced by what Wegman discovered was a small, insular group of paleoclimatologists who incestuously peer review, reinforce and defend each others’ work.
Wegman et al. discovered no such thing. They conducted a Committee of un-American Activities-type analysis but much more sophisticated and used guilt by association. Their independent analysis showed separate clusters of researchers. They had no information on who the reviewers were and what was in the reviews. There are sufficient researchers available to offer proper peer review. The best they managed was that the different analyses were using common data (well, duh) and inferred that was somehow suspect.
The claim of primitivity in climate change models is interesting. These models are dynamic, are run in open mode from a set of initial conditions and external forcing and do a good job of many global processes. They are not perfect, but are continually being improved â€“ the improvements are openly detailed in the international literature and in IPCC assessments. In contrast, many of the economic models that seem to be preferred in many circles are not dynamic, being based on general equilibrium and internally optimise themselves assuming â€œperfect knowledgeâ€? of processes that are poorly understood.
Significantly, former commonwealth statistician Ian Castles and his colleague David Henderson, former head of the Organisation for Economic Co-operation and Development’s economics department, have also exposed statistical and analytical flaws in the economic scenarios underlying the IPCC’s climate change projections. As with McIntyre and McKitrick’s criticism of the hockey stick, the IPCC establishment initially tried to ignore, then discredit, their work.
Here is what the International Energy Agency said about Castles and Henderson: We are aware of the fact that the validity of some of the assumptions underlying the IPCC-SRES scenarios, and particularly the scenarios of the A1 family were recently challenged by I. Castles and D. Henderson. One of their main objections centred on the use of GDP data measured at Market Exchange Rates (MER) instead of Purchasing Power Parities (PPP). As the rebuttal written by Nakicenovic et al. and published in issue 2 of 2003 of Energy and Environment provides some reasonable answers to the issues raised, we stick to our choice of reference framework. ENERGY TO 2050 Scenarios for a Sustainable Future IEA, 2003.
However, last year a House of Lords committee looking at the economics of climate change praised their work and said that without them the debate on emissions scenarios would not have taken place.
This confusion can arise when all pieces of information are treated equally rather than being assessed properly â€“ the same happened in the New South Wales Parliament background paper on climate change science http://www.parliament.nsw.gov.au/prod/parlment/publications.nsf/0/FB07F849FCBA7B76CA2571150023166E
The Lords committee also expressed concerns that the IPCC was an increasingly politicised body that tried to suppress dissent. It warned of a risk it was becoming a knowledge monopoly, “in some respects unwilling to listen to those who do not pursue the consensus line”.
In an article last week in Canadian newspaper the National Post, McIntyre and McKitrick say the IPCC’s lead author, who selected Mann’s hockey stick for prominent display, was none other than Mann himself. They quote eminent US climate science academic Kurt Cuffey as saying the IPCC’s use of the hockey stick sent “a very misleading message”.
They ask a pertinent question.
If the IPCC process isn’t fixed, and there is no evidence the IPCC intends to do anything about it, how do we know it won’t send out another very misleading message in its upcoming Fourth Assessment report?
It was interesting to see the word Fraud associated with the article. Deliberate deception intended to mislead a third party for personal gain. Hmmm.