So if the models are so hopelessly riddled with errors and uncertainty that an anthropogenic radiative forcing signal cannot be distinguished from noise, or if the total magnitude of the warming attributed to humans is one-tenth to one-hundredth of the error or uncertainty ranges, why are those who dare question the degree to which humans affect the Earth’s climate branded as “deniers” of science?

Kenneth Richard,

Friday, 21 March 2014

Occam’s Broom and the stink of ‘97% of Climate Scientists’

‘The molecular biologist Sidney Brenner recently invented a delicious play on Occam’s Razor, introducing the new term Occam’s Broom, to describe the process in which inconvenient facts are whisked under the rug by intellectually dishonest champions of one theory or another…The practice is particularly insidious when used by propagandists who direct their efforts at the lay public …their carefully crafted accounts can be quite convincing simply because the lay reader can’t see what isn’t there.’                            Source: Daniel C Dennett

This Broom is so widely used in climate-scare propagandising that it could be the basis of a book about that dark art.  I want to focus on just one of the displays of it and that is the mis-use of the statistic '97% of climate scientists'.  To mix the metaphor, here is a source of one foul smell that no amount of brushing can remove.  It is the smell of deliberate deceit repeated over and over again.

As we shall see, the 97% figure, or ones like it, come from very unsatisfactory sources, and are not at all what they are sometimes made out to be, often by innuendo, insinuation, or juxtaposition.  The deceit occurs when the audience is encouraged to conclude that the 97% agree that there is a dreadful crisis associated with our CO2 emissions, and that draconic interventions by governments are all but immediately required if we are to survive the imminent catastrophe. 

In reality, the figure generally means, where meaning can be found in the studies which have produced it, that a non-random selection of people or papers contains around 97% of items supporting the twin notions that we affect climate with our CO2 emissions and that there has been overall global warming during the 20th century to which we have contributed.  

Note there is nothing intrinsically alarming about either of these notions because they are unquantified.  Some scientists believe for example that our impacts on the climate system have been too small to detect so far using global measures such as mean temperature, and may well remain so even if ambient CO2 levels continue to increase this century.

Here is a prominent example of 'propagandists directing their efforts at the lay public', published in the Wall Street Journal in 2012:

'The world is heating up and humans are primarily responsible. Impacts are already apparent and will increase. Reducing future impacts will require significant reductions in emissions of heat-trapping gases.  Research shows that more than 97% of scientists actively publishing in the field agree that climate change is real and human caused.  It would be an act of recklessness for any political leader to disregard the weight of evidence and ignore the enormous risks that climate change clearly poses’
I have put the key phrase in bold to help it stand out.  Notice the tone of the surrounding text.  This is the insidious part.  It would seem, would it not, that this 97% of scientists hold that 'humans are primarily responsible', that 'significant reductions of heat-trapping gases' are required, and it would be 'reckless' to 'ignore the enormous risks'.  That is crisis talk.  We do not know how many scientists, or what proportion of them, believe there is such a crisis.  The 97% is not that figure, nor indeed has it been shown to be the proportion who agree that all of climate change is human caused (another insidious insinuation in the above quote).

Here is a more straightforward usage on a NASA site, one which might well be widely referenced by schoolteachers, pupils, and the authors of school materials:

'Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities.'

We also have this notorious tweet from the office of the US President, Barack Obama in 2013:

‘Ninety-seven percent of scientists agree: #climate change is real, man-made and dangerous.’
Anthony Watts described the tweet quite simply as a lie: 
Here’s the genesis of the lie. When you take a result of 32.6% of all papers that accept AGW, ignoring the 66% that don’t, and twist that into 97%, excluding any mention of that original value in your media reports, there’s nothing else to call it – a lie of presidential proportions.’

Lifting the Rug

The notion of an overwhelming consensus in support of alarm is generally traced to one or other of 4 studies:

All 4 have been severely criticised.  
For example, re the Oreskes study of a set of papers she located from the years 1993 to 2003, the theoretical physicist Lubos Motl was not impressed and supports Benny Peiser's view: 'In light of the data presented above (evidence that can be easily verified), Science should withdraw Oreskes' study and its results in order to prevent any further damage to the integrity of science.'  A medical researcher, Klaus-Martin Schulte also took a critical look at Oreskes' methods, and using them on more recent papers, published between 2004 and 2007 he found:  'Of 528 total papers on climate change, only 38 (7%) gave an explicit endorsement of the consensus. If one considers "implicit" endorsement (accepting the consensus without explicit statement), the figure rises to 45%. However, while only 32 papers (6%) reject the consensus outright, the largest category  (48%) are neutral papers, refusing to either accept or reject the hypothesis.  This is no "consensus."'
Doran and Zimmerman's work was essentially a student project given an elevation and prominence which it did not, to put it mildly, deserve. In an attempted census of some 10,000 targets, only about 3,000 responded, and of these a subset of about 77 was singled-out to produce the 97% statistic since 75 of them agreed with quite innocuous, but carelessly worded, statements about climate to the effect that it has been warming recently, and humans could have contributed to it in a 'significant' way.  WUWT has relevant links.
Anderegg at al has been described as 'having so many defects it should never have been published' (see source of this observation and other criticisms in this post by Tom Harris.  Roger Pielke Sr. noted that the paper illustrates 'how far we have gone from the appropriate scientific process.'
Cook et al has also been shredded by informed commentators, appalled at what they found in it.  It actually contradicts what it is purporting to show, as noted by Brandon Shollenberger: 'This study done by John Cook and others, praised by the President of the United States, found more scientific publications whose abstracts reject global warming than say humans are primarily to blame for it.  The “consensus” they’re promoting says it is more likely humans have a negligible impact on the planet’s warming than a large one.’    Marcel Crok was a little harsher, he provides chapter and verse to show why the Cook et al paper is both 'meaningless and misleading'.  Christopher Monckton finds that 0.3% 'consensus' is more convincing than 97% using the Cook et al data, and he also has useful, and critical, insights on the other source papers.*
Andrew Montford has written a brief and very accessible overview of some of the shortcoming of the last three papers.  He points out that their  ' results add up to little more than “carbon dioxide is a greenhouse gas” and “mankind affects the climate.” These are propositions that almost everybody in the climate debate accepts; ‘  He has also published a trenchant analysis of the Cook et al paper ins this GWPF note.  In it he quotes Mike Hulme, by no means a climate sceptic, writing 'The [Cook et al.] article is poorly conceived, poorly designed and poorly executed.   It obscures the complexities of the climate issue and it is a sign of the desperately poor level of public and policy debate in this country that the energy minister should cite it.'
Let me end with the words of commentator Barry Woods on the WUWT blog:: '.. I would like to put aside any criticism of the methodology or conclusions the scientists behind the Doran, Anderegg or any other similar paper make, and reserve my strongest criticism to others that misrepresent them, or go much further than the conclusions. My strongest criticism is not for those politicians, environmentalists, journalists or scientists, that use the soundbite of ’97% of scientists’ in complete ignorance of its source, or do not check the citation for themselves ...No, I reserve my strongest criticism for those activist scientist that know full well the source of the ’97% of scientists’ soundbite and use it anyway, ... and then use it to imply that there is some consensus of future dangerous or catastrophic risk, or that certain policies that must be taken, because of this consensus.'
I think Barry is right.  Irresponsible people can deploy Occam's Broom on this as much as they like, but the rotten smell of their '97%' insinuations will not go away.  Their rug has been lifted on that one.  In due course, I hope this particular deception will be removed from materials aimed at schoolchildren.  In the meantime, teachers and pupils alike can express their disdain by holding their noses as and when they come across it.
* Note added 26 March 2014. I forgot to mention the important study published by Legates in 2013 about the Cook et al. nonsense.  A useful report on it can be found here:  Extract: 'Dr Legates said: “It is astonishing that any journal could have published a paper claiming a 97% climate consensus when on the authors’ own analysis the true consensus was well below 1%." '  

Note added 14 March 2017.  The corrupted-by-campaigners organisation NASA has long had a 97% claim up on its website.  Here is a report on just how shonky their reference to support it is:
'If you actually click on the reference, you quickly realize that the claim is fraudulent. '
Further Reading
(1) The NIPCC 2013 report 'Climate Change Reconsidered II' is a good source of counter-arguments linked to the scientific literature and taking a contrary position to that promoted by the IPCC leadership.
(2) The Popular Technology website has compiled a list of over 1,350 'peer-reviewed papers supporting skeptic arguments against ACC/AGW alarm'. 

(3) For a very recent exposure of Occam's Broom being deployed by IPCC scientists see :

IPCC Scientists Knew Data and Science Inadequacies Contradicted Certainties Presented to Media, Public and Politicians, But Remained Silent

Note added 10 May 2014  A further refutation of the Cook-junk is about to be published as a journal note.  More details here: )
Note added 4 Sep 2014  More devastating analysis of the Cook et junk:
'This all tells us:

1) They blatantly, cavalierly, and repeatedly violated the methods they claimed in their paper, methods that are crucial to the validity of a subjective rater study – maintaining blindness to the authors of papers they rated, and conducting their ratings independently. This destroyed the validity of an already invalid study – more coherently, it destroyed the validity of the study if we assumed it was valid to begin with.

2) These people were not in a scientific mood. They had none of the integrity, neutrality, and discipline to be subjective raters on such a study. We could've confidently predicted this outcome in advance, given that they're political activists on the subject of their ratings, had an enormous conflict of interest with respect to the results, and the design appointed them subjective raters of written work, placing them in the position to deliver the results they so fervently sought. Just that fact – the basic design – invalidates the study and makes it unpublishable. We can't go around being this dumb. This is ridiculous, letting this kind of junk into a scientific journal. It's a disgrace.'
Note added 16 Sep 2014    Andrew Montford has written a report on the Cook et al.travesty - one of the sources of '97%'.  He concludes the consensus they produce is 'virtually meaningless'.

Note added 21 Dec 2014  Popular Technology have listed their top 97 articles refuting the '97% consensus':  They note, 'The following is a list of 97 articles that refute Cook's (poorly conceived, poorly designed and poorly executed) 97% "consensus" study. The fact that anyone continues to bring up such soundly debunked nonsense like Cook's study is an embarrassment to science.'
Note added 18 May 2015.  The '97%' nonsense is still being used, presumably because the propaganda benefits are many.  Here Ross McKitrick shows once again how shoddy it is:
Note added 13 August 2015.
Here is a 2014 article by James Delingpole which provides some useful insights into the tawdry methods and motivation of Cook et al:

Here is an August 2015 post by the MEP Roger Helmer (hat tip Climate Science) noting that a somewhat more respectable (but imho still very unsatisfactory) survey in which less than 50% of respondents took the IPCC party line:
Details of that survey can be obtained here:

Note added 23 March 2016.
Anthony Watts: 'I don’t like to use the word “fraud”, and I can’t recall if I’ve ever used it in a title. In this case it is warranted. Brandon Shollenberger writes of a new book, The Climate Wars: How the Consensus is Enforced, that proves without a doubt that John Cook and his “Skeptical Science” team are nothing but a gang of “say anything” activists, and that the much repeated “97% consensus” is indeed nothing more than a manufactured outcome.'


  1. Excellent article!

    I have some more relevant information here, mostly about Doran 2009:

    Don't blame Zimmerman for that one, BTW. She was the student who did the grunt work of conducting the survey, but Prof. Doran is the one who formulated the bias-inducing questions, and who wrote the article claiming a 97.4% consensus, which he obtained by first discarding 97.5% of the survey respondents for being insufficiently specialized in climatology, and then also discarding at least half of the self-identified skeptics who remained in his tiny pool of just 79 self-identified climate specialists.

  2. Thank you for your comments and link. I do agree about Zimmerman. She was just doing a project for her master's degree. Doran was her supervisor and it would have been him who decided to publish the findings of her project in that ludicrous way.