Ian Plimer, a distinguished professor of mining geology, and well known climate “sceptic” recently published a book in which he claims to show that concerns about warming are unscientific - that they are really a kind of spiritual yearning - and boldly sets out to prove the contrary: it’s getting colder.
Ian Plimer & the hockey stick
Farmers from round the country attended a conference a little while ago to listen to experts tell them about what they would have to deal with under a changing climate. On the evening news, a climate scientist sounded a serious note, and a farmer said it had been interesting to hear the “scientific debate” first hand; and then Professor Ian Plimer told us that the world was getting colder. Presumably that was what he told the farmers. And then I understood why the farmer spokesman had looked a bit bemused. He had every right to be.
With those few words, the professor asserted not only that the three big global temperature monitoring Centres - The University of East Anglia, NASA’s Goddard Institute, and the National Oceanic and Atmospheric Administration - which have specialised in this work for decades, don’t know what they’re doing, but also that all the observed consequences of warming - melting ice, rising seas, droughts, storms, fires, migrating plants & animals, etc - is all phoney or due to something else. It’s a bit like asking us to believe that measles is caused by cosmic rays & it seems incredible that a real professor said it. Yet he did. What’s on his mind?
Well, we now have somewhere to look for an answer. In his recently published book: “Heaven & Earth - Global Warming, the Missing Science”, he promises to refute in its entirety everything climate science has told us about the problem. Everything. This isn’t just an argument about one or more findings or interpretations or a theory or measurement; Plimer finds the whole climate science enterprise is not merely mistaken but misguided and corrupt. Its practitioners, according to him, are dishonest and malignant; the whole project is driven by deceit and self-interest. In short, it’s a book about a conspiracy theory.
That’s not how it presents itself though. It is full of graphs & references to scientists and their work; it cites the scientific literature 2300 times; there is any amount of argument about scientific issues. So it looks just as if the author knows his stuff and is grappling with equals. But he doesn’t, and he’s not. It isn’t really a scientific book at all - not even in the elementary sense that it begins with an open minded enquiry - it begins and ends with a conviction, and all the “facts” and arguments are contrived to support it. That makes it a work of propaganda, not science.
If you're interested, I've written a full-length review of the book, in an essay that also tries to understand what makes the climate-denier enterprise tick (which is difficult). Here, to show you the kind of scientific abuse this book is full of, I’ll just explain his treatment of the “hockey-stick” controversy.
The “hockey stick” was so named by sceptics for the very thing they wanted to deny - the sharp twentieth century up-turn on the right side of the figure. It is red because these temperature records were made with thermometers; the rest are surrogates, mainly tree ring studies, but including cores taken from stable corals and sediments.
Other similar studies done since this one have confirmed it, although some show the medieval warming (to about AD 1350) more prominently. Every one shows the exceptional character of the last 100 years.
Ian Plimer’s treatment of the “hockey-stick”: an example of his method
What’s the hockey stick all about?
To be certain the world is warming abnormally, we need to know how hot it was in the past. But we only have reasonably good temperature records back to about 1860. Everything before that must be inferred by indirect methods - finding clues to temperature and other climate properties in various places - mostly in living and dead organisms and in the earth itself. Such data are called climate “proxies”. The science behind their collection and interpretation has been a big preoccupation of investigators over the last 50 years and almost all our knowledge of ancient climates has come from this effort.
In 1999, three scientists published a study of collected proxy data for the last millennium - the first time this had been attempted. They did it by carefully extracting the temperature records from a large number of individual studies of ancient trees, corals and ice cores, mostly from sites in the Northern hemisphere, and combining them to create a global picture. Of the three, two were climatologists and one a specialist in ‘dendrochronolgy’, the science of getting climate data from tree rings. The statistical treatment of such data is complex, and the results are usually open to some methodological argument - but their study wasn’t seriously challenged until several years later, after it had become a famous exhibit in the IPCC’s 2001 report.
There followed a sometimes bitter dispute, still unfinished today. Sceptics and deniers began to deride the famous graph as “the hockey stick”, and if you search for this on the web now, you will find many places where the study is assumed to be, at best a mistake, and at worst a malicious fraud. This is strange when you consider that these findings have been independently confirmed several times in the last decade, and the great majority of scientists competent to adjudicate the matter are satisfied that it is settled.
What is Ian Plimer’s position?
He discusses the “hockey stick” between pages 87 & 99, beginning with a suggestion that Michael Mann, the lead author, deliberately altered his data so that the episodes known as the ‘medieval warming’ (900-1300AD) and the ‘little ice age’ (1280-1850AD) were invisible. Next, he implies that Mann was seduced by the professional rewards that followed the success of his study, and that the IPCC colluded with him in promoting its false conclusion. With these hints of his own prejudice, Plimer switches the focus from what is really a very technical argument about statistical methods, to persons; then he takes the unwary reader on a Mann-bashing journey, along paths already laid down by a bevy of climate sceptics, repeating all the long-discredited calumnies this patient investigator has put up with for years.
Plimer says the IPCC “dropped” the hockey stick from its 2007 report; it did no such thing. In fact, the section on temperature reconstructions for the millennium is updated with eleven new studies, giving better resolution, and confirming the 20th century trend. [see figure below] He does not mention that Mann himself published an update in 2008, [can be viewed here] which employs better data and improved statistical techniques - and it shows exactly the same result. He naturally says nothing about Mann’s many careful refutations of his main critics, McKitrick & McIntyre, showing how their attacks on his work are deceptive, and presumably contrived to promote some prior agenda. Nor does he cite the work of Wahl & Ammann (2007) [can be seen here] which shows that McKitrick & McIntyre were mistaken.
Figure 11, on page 89 reproduces (without acknowledging the source) a graph made by Hubert Lamb, a pioneer climate scientist, in 1965, showing the temperature in the year 1300 half a degree warmer than the 20th century average. It is labelled “Climate changes in Europe over the last thousand years” - but this is false. Lamb drew it as a reconstruction of temperature for Central England, using data that would now be considered inadequate. Plimer says that Mann “rubbed out” the medieval warming because it didn’t suit his case (it actually reappears in his later work). In fact, Plimer has “pumped up” the medieval warming to suit his case, claiming that Lamb’s graph represents “hundreds of previous validated studies”, when it does nothing of the kind.
How can this be resolved?
The dispute quickly became political, and in 2006 in an atmosphere of acrimony, the US Congress deputed two expert committees to report to it. The first was assembled by the National Research Council’s Board on Atmospheric Studies with a brief to examine the question of what can be known about 20th century warming & with what certainty; the second was convened at the behest of congressman Joe Barton, a long-time climate denier, and chaired by Edward Wegman, a very eminent statistician. It concentrated on statistical questions but also had a lot to say about the professional and personal relationships of the practicing scientists.
Understanding exactly how each of these reports resolves or exacerbates the controversy is not easy, but it’s safe to say that Plimer’s account of them is both thoroughly partisan and very misleading. Essentially, the NRC report said that Mann’s data were most reliable for the last 400 years; less so for the 700 years before that. Mann himself completely agreed. It confirmed that the 20th century warming is detected in borehole temperature measurements, and can be simulated in climate models, and is buttressed by a large body of observational evidence.
Wegeman’s report, on the other hand, found in favour of Mann’s critics, and further criticized the institutional arrangements between scientists. The findings could be very briefly summarized thus:
1. Mann’s conclusions are not warranted by his data and methods;
2. Climate scientists should collaborate more with statisticians;
3. The community of climate scientists is too closed and incestuous for its own good.
Needless to say, this was not the last word, and there seems to be a strong prima facie presumption that Wegeman’s committee was reporting conclusions arrived at beforehand. Be that as it may, if we concentrate on what really counts - the trend of accumulating evidence - it is clear that the specialists most competent to decide, regard this ‘debate’ as finished, and the reality of anomalous 20th century warming as beyond reasonable doubt. You will judge for yourself, but to me, Plimer’s treatment of this controversy reads like propaganda - certainly not the dispassionate unravelling that is required.
IPCC 2007 Fig 6.10
from chapter 6: Paleoclimate
In section 188.8.131.52 of the report, the IPCC scientists discuss the current consensus on temperature reconstructions for the last 2000 years. As this figure shows, a number of high quality studies since Mann’s have converged on essentially the same result.
The top graph shows two historical records - one for land & one for land and sea - from 1850, with an estimate of uncertainty (because the measurements were not standardized at the time they were made).
In the middle is a plot of all eleven proxy reconstructions, together with the instrumental record.
At the bottom is a graphic showing the range of agreement of the included studies.
This is powerful confirmation of the proposition that 20th century warming is not comparable to any past episode & in fact exceeds our experience in both magnitude and rapidity.
It is hard to know what would convince anyone, if this data does not - unless you held the view that all climate scientists (and the IPCC) are crooks - in which case it is not evidence that matters but purity of conviction.
I’ll end by making a couple of general observations about this book and its author. More can be found in my essay.
• The writer has a strange approach to scientific authorship. He certainly puts in plenty of references to published sources, but many of them are incorrectly attributed, some are spurious, and some deliberately misleading. He makes extraordinary sweeping claims, such as that CO2 could not affect climate because it is a ‘trace gas’; that all the arguments for anthropogenic climate change come from atmospheric studies; that the science of geology has been ignored; that global temperature was higher in the 13th century than in the 20th; and many more. One can only think that the heat of his conviction has overwhelmed his better judgement.
• The book gives an impression that it is meant to be a show of force - as if the author expects to sweep his audience before him with an exhibition of scientific sound and fury, and a few mirrors and disguises. I am not a climate scientist, any more than Ian Plimer is - yet just by bringing to the reading a little knowledge of what has been accomplished in this field, I can easily detect the bluster and intimidation where there should be careful and judicious argument.
• It is a gravely misleading book, but also a seductive one. Its vigorous sales, at least in this country, suggest two things - that there are many people who already share Plimer’s views, and that the public will continue to consume denial because the reality of the climate problem is so disturbing and unwelcome. In this respect, it does a huge disservice to our descendants, who will surely shake their heads in disbelief that we were taken in by such poor stuff.
Click here for a full length review of Plimer's book