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Watch The Pea

July 12, 2013

By Paul Homewood




The results of John Cook’s survey have been well publicised. Most of the media appear to have picked it up, with headlines such as “Scientists say united on global warming, at odds with public view”.

We are now, no doubt, well versed in the claim that “97.1% endorsed the consensus position that humans are causing global warming” and a lot of attention has been paid to how papers have been classified,( or misclassified).

However, in looking at the detail, we have taken our eye off the pea. Let me explain.


A quick recap, first. Cook and his volunteers have been busily reading abstracts of papers relating to global warming, and using this as a basis to grade them into seven endorsement levels, as below.




The results of this grading are below.


Category No. of Papers
1 65
2 934
3 2934
4 8269
5 53
6 15
7 10
Total 12280


Take out Category 4, the “Don’t Knows”, and you get 4011 papers, of which 3933 are in the first 3 categories. And 3933 is 98% of the 4011 papers that have expressed some position on global warming. (These figures are slightly higher than Cook’s abstract gives, possibly due to the inclusion of non peer reviewed ones).

In other words, Cook assumes that all the papers in Category 1-3 “agree that humans are causing global warming”, as his abstract states.


Now, this is where you have to start watching the pea. Others have pointed out that even a paper investigating the effects of UHI or land use change would effectively acknowledge that “humans are causing global warming”.

Moreover, many of the papers are unbelievably woolly when it comes to discussing global warming. I have taken the relevant extracts from three papers to give some idea of this. These three are not cherry picked in any shape or fashion, they appear top of the list under Cook’s Mitigation Category, as you can from this screenshot. All are rated under Category 3 – Implicit Endorsement.




1) Buying Greenhouse Insurance (No, it’s not the sort you grow tomatoes in!)

There have been numerous proposals for immediate cutbacks in CO2 emissions. Proponents argue that sizable reductions are necessary as a hedge against unacceptably rapid changes in climate. This paper provides a decision tree analysis of the problem. We examine how the optimal hedging strategy might vary with: a) the damage potential associated with the continued buildup of greenhouse gases; b) the accuracy and timing of climate research; and, c) the prospects for new supply and conservation technologies.

2) CO2 emissions reduction by price deregulation and fossil fuel taxation: A case study of Indonesia

As environmental issues, and the issue of global warming in particular, rise to the top of the international agenda, developing nations are faced with a major question: how to confront these environmental problems and simultaneously address a number of more pressing developmental imperatives? This paper tries to answer that question on a limited scale using Indonesia as a case study. The study indicates that by deregulating energy prices and imposing different levels of taxation on fossil fuels, Indonesia could reduce its CO2 emissions without considerably suppressing the growth of its economy. In the long run, however, these policies cannot cope with the inevitable rise in coal-use in Indonesia, due to constraints on domestic natural gas and oil resources. Limiting the growth of coal consumption in the future will require direct technological intervention in the supply and demand of energy and a shift in current energy export and import policies.

3) Effect of encapsulated calcium carbide on dinitrogen, nitrous oxide, methane, and carbon dioxide emissions from flooded rice

The efficiency of N use in flooded rice is usually low, chiefly due to gaseous losses. Emission of CH4, a gas implicated in global warming, can also be substantial in flooded rice. In a greenhouse study, the nitrification inhibitor encapsulated calcium carbide (a slow-release source of acetylene) was added with 75, 150, and 225 mg of 75 atom % 15N urea-N to flooded pots containing 18-day-old rice (Oryza sativa L.) plants. Urea treatments without calcium carbide were included as controls. After the application of encapsulated calcium carbide, 3.6 μg N2, 12.4 μg N2O-N, and 3.6 mg CH4 were emitted per pot in 30 days. Without calcium carbide, 3.0 mg N2, 22.8 μg N2O-N, and 39.0 mg CH4 per pot were emitted during the same period. The rate of N added had a positive effect on N2 and N2O emissions, but the effect on CH4 emissions varied with time. Carbon dioxide emissions were lower with encapsulated calcium carbide than without. The use of encapsulated calcium carbide appears effective in eliminating N2 losses, and in minimizing emissions of the “greenhouse gases” N2O and CH4 in flooded rice.


Leaving aside the issue that none of the authors of these papers were in any way qualified to discuss the science behind global warming, and were effectively just passing on hearsay, the statements were unbelievably vague. “Rise to the top of the agenda”, “as a hedge”, “implicated in”! I don’t want to get into a debate as to which category these should be included in. Indeed, Category 3 probably seems fitting.

But what does Cook mean when he talks of “humans causing global warming”? Is he including the full range of views? Does he include and acknowledge the views of many sceptical scientists, who, while accepting that GHG’s will lead to some warming, stress the importance of other, natural factors in shaping our climate?

Or is he talking of what, we might call, the IPCC consensus position.


It’s time to watch the pea.


In his abstract, John Cook states:-

We analyze the evolution of the scientific consensus on anthropogenic global warming (AGW) in the peer-reviewed scientific literature, examining 11 944 climate abstracts from 1991–2011 matching the topics ‘global climate change’ or ‘global warming’. We find that 66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming. Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming.


So you would think this encompasses the full range of views, but no. Further down in his introduction, Cook says:-

We examined a large sample of the scientific literature on global CC, published over a 21 year period, in order to determine the level of scientific consensus that human activity is very likely causing most of the current GW (anthropogenic global warming, or AGW).


This is a much narrower definition, and of course fits in with the IPCC position. I would also argue it fits in with the public perception of what they regard as climate change.

Furthermore, this is the message the media have passed on. For instance, Reuters say:-

Experts in Australia, the United States, Britain and Canada studied 4,000 summaries of peer-reviewed papers in journals giving a view about climate change since the early 1990s and found that 97 percent said it was mainly caused by humans.

And the Australian:-

A REVIEW of thousands of studies published over 21 years found "overwhelming" and growing consensus among scientists that humans are mostly to blame for global warming, its authors said Thursday.

Have the media hyped up the message? Apparently not. The Institute of Physics reports co-author, Mark Richardson, as saying:-

We want our scientists to answer questions for us, and there are lots of exciting questions in climate science. One of them is: are we causing global warming? We found over 4000 studies written by 10 000 scientists that stated a position on this, and 97 per cent said that recent warming is mostly man made.”


This is quite specific, but where is the evidence for it? Only 65 papers are graded as specifically stating this. It is abundantly clear that many papers, included in the 97%, do not support this assessment. They MAY agree with this view, but there is no tangible evidence to make a judgement either way.

In other words, John Cook has interpreted all of these papers as supporting his assertion that “ human activity is very likely causing most of the current GW”.

This is a huge leap of imagination. What evidence does he or his researchers have to make this judgement? Very little, it seems to me.

In no way can this be regarded as a serious scientific exercise. Which raises a separate point – what on earth were the peer reviewers doing when they flagged this one through? Clearly not their jobs.


It seems to me that John Cook has two alternatives:-

1) Amends his abstract, and other statements, to say that 97% of papers support the view that humans are responsible for some of the warming seen, but there is still a wide variety of opinion as to how much, and to how much of a role natural factors play.

He also needs to spell out how many of his selected papers actually offer evidence of AGW, as opposed to simply repeating heresay.


2) Identify the number of papers that actually support his assertion that “ human activity is very likely causing most of the current GW “, which will be a hugely reduced number.


If he is not prepared to do this, his survey will remain heavily flawed, and will be seen as no more than a PR stunt.


One question remains. Was this a case of deliberate misrepresentation on Cook’s part, or was he so convinced of his own propaganda that he deluded himself?

  1. Brian H permalink
    July 13, 2013 8:23 am

    Sounds to me as though many are of the form, “IF AGW, THEN …” The one sample abstract even puts “greenhouse gases” in quotes. It reads as “purported GHGs”. Even a firm skeptic could do research under such a heading.

    • Craig King permalink
      April 26, 2014 2:41 pm

      Me too Brian. A great deal of the published stuff is of the “IF this THEN that” form. I wonder how many published papers say that “Man Made CO2 causes global warming as the measured data shows by a predictable mechanism that is well understood. Here are the projections of temperature change vs CO2 concentration”.

      Those papers are hard to find.

  2. April 26, 2014 7:55 pm

    What Cook really should have published is that 0.00529% of peer reviewed studies claim that man is the cause of AGW. 65/12280 of category 1 level of endorsement

    • April 26, 2014 10:37 pm

      Or maybe include the lower level of explicit endorsement for 8% (999/12280). This may be the most realistic number.

      If you want to stretch the truth to include implications, then you still only get 32% (3933/12280).

  3. April 26, 2014 10:08 pm

    Reblogged this on pdx transport.

  4. Frank permalink
    October 14, 2015 2:40 am

    Paul: I was looking back at this paper and looking for the original source of percentages for the seven categories you show. I can’t find them anywhere in the paper. Could you tell me where the seven percentages you cite came from?


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