Ninety Seven Percent

lady and the tramp beaver

Once again, Cook et al 2013 seems to be generating quite a bit of discussion.  According to the abstract, 97% of a selection of scientific papers related to Global Warming “support the consensus” that “humans are causing global warming”, vis:

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. In a second phase of this study, we invited authors to rate their own papers. Compared to abstract ratings, a smaller percentage of self-rated papers expressed no position on AGW (35.5%). Among self-rated papers expressing a position on AGW, 97.2% endorsed the consensus. For both abstract ratings and authors’ self-ratings, the percentage of endorsements among papers expressing a position on AGW marginally increased over time. Our analysis indicates that the number of papers rejecting the consensus on AGW is a vanishingly small proportion of the published research.

So far, so good, I don’t have any problem with that. And it’s clear that if 97% of papers agree with something then, by definition, that is a consensus.  However, this statement is being interpreted as saying something a bit more: that 97% of those papers support the idea that humans are responsible for more than 50% of the warming seen in the 20th Century.  This claim is not supported by the paper’s own data.

The endorsement levels in the supplementary data  are:

1    Explicitly endorses and quantifies AGW as 50+%
2    Explicitly endorses but does not quantify or minimise
3    Implicitly endorses AGW without minimising it
4    No Position
5    Implicitly minimizes/rejects AGW
6    Explicitly minimizes/rejects AGW but does not quantify
7    Explicitly minimizes/rejects AGW as less than 50%

Of these, only endorsement level 1, “Explicitly endorses and quantifies AGW as 50+%” matches the claim “Humans responsible for more than 50% of 20th Century warming”.

The distribution of the endorsement level across the examined papers is:

1    Explicitly endorses and quantifies AGW as 50+%     64
2    Explicitly endorses but does not quantify or minimise    922
3    Implicitly endorses AGW without minimising it     2910
4    No Position    7970
5    Implicitly minimizes/rejects AGW    54
6    Explicitly minimizes/rejects AGW but does not quantify    15
7    Explicitly minimizes/rejects AGW as less than 50%    9

So only 64/11944 papers endorse the stronger position of humans having than more than 50% effect on the 20th Century temperature increase.  If we exclude from this count the 7970 papers classified as “No Position” (which is what the paper’s authors did) then the figure becomes 64/3974 endorsing the “more than 50%” position.  Far from being 97%, this is around 1.6% – a piffling amount. In fact, I would go so far as to say that it is “vanishingly small”.

It seems to me that this paper has discovered that 97% of the papers selected endorse the idea that human activity has caused some degree of warming.  This is essentially the position held by the majority of sceptics.

Why all the fuss?

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18 responses to “Ninety Seven Percent”

  1. Gary H says :

    Ah, only 64 endorse Obama’s view.

  2. jim says :

    Reblogged this on pdx transport.

  3. Sundance says :

    The 97% is used by climate activists to paint their opposition as irrational and it is something that is easy for mindless fanatics to keep repeating in the twitterverse, president Obama being a good case in point. Climate activists have been programmed to rely on their amygdala and are driven by emotion not reason so they shut down frontal lobe activity as soon as you lead them into the details and data of a flawed and overreaching study that refutes their emotional programming. Climate activist aren’t interested in actual science data or facts.. All they require is a bumper sticker meme to mindlessly repeat and use to shout down opposition. They have programmed themselves not as independent thinkers who question authority, but weak minded followers driven not by fact but by fantasies such as saving the planet.

    One last thought. You’ve seen John Kerry introducing another bumper sticker meme, “climate terrorism”. He hasn’t done this directly but by John Kerry stating that climate change is a bigger threat than terrorism he has set the table for activists to label those that oppose EPA regs as “climate terrorists”. This is all pre-planned stagecraft intended to provide the self-absorbed, unquestioning, emotionally driven, frontal lobeless, one dimensional linear thinkers a new bumper sticker/meme to shout at opposition. 😉

  4. Phil Ford says :

    The BBC are particularly fond of using the ‘97% meme’ to reinforce their intractable pro-CAGW position. They restate their firm adherence to the Church of the Holy Consensus in just about every natural history documentary they make – and the infamous ‘97%’ appears regularly in their news and current affairs reporting. It’s beyond contempt.

  5. BallBounces says :

    If you like your 97%, you can keep your 97%.

  6. Victor Venema says :

    If you want to remove all that do not quantify, you get another question, that would be the opinion of scientists making attribution (quantifying the contribution of the various possible causes of climate change) studies, rather than the opinion of the larger scientific community.

    If you want to remove them, you should remove all that do not quantify. That would make a consensus among scientists that studied the topic of 64/(64+9)=88%. About the same. And the 9 is probably generous, many of those likely did not make a formal attribution studies.

    • Derek Sorensen says :

      It wasn’t that I “wanted” to remove anything; I was simply doing the same thing Cook et al did. If I hadn’t removed the neutrals the “more than 50%” percentage would have been much lower.

    • tlitb1 says :

      @Victor Venema says : June 19, 2014 at 7:37 pm

      “If you want to remove them, you should remove all that do not quantify. That would make a consensus among scientists that studied the topic of 64/(64+9)=88%. About the same. And the 9 is probably generous, many of those likely did not make a formal attribution studies.”

      Why bother falling back to this 88%? What is this supposed to mean with regard any “consensus”?

      All it can indicate is that over an extensive search of thousands of papers, over the last 20 years, there are only 71 papers found that actually claim a specific level of attribution of human contribution.

      Even if they all agreed one way or the other it does not seem enough to stand credible as a proxy for the actual belief (and strength of belief) of the thousands of other scientists.

      If the argument is that there are only approximately ~100 scientists in the world who can make credible claims about attribution then IMO that isn’t going to be a good argument there exists a powerful consensus that should influence policy. 😉

      • tlitb1 says :

        Spot the deliberate mistake – when I say 71 papers I meant 73!

        Not many out of 1200, however I should have treasured every one!

        Luckily the 2 I left out were outside the consensus – whatever that is today 😉

  7. Arthur Cohn says :

    Options numbers 1,2, and 3 add up to 3,700. The total papers considered add up to 8050.
    3700/8050= 46%
    Thus 46% of the papers endorse AGW to some extent.

    • Derek Sorensen says :

      97% of the papers endorse AGW “to some extent”, just as, I’d guess, do 97% of sceptics.

    • GoFigure560 says :

      How can any prudent scientist not agree 100% that human activity contributes to global warming? If I strike a match, isn’t that a contribution?

      • Arthur Cohn says :

        The point of the warmists is that because of mankind spewing CO2 the Earth will go beyond a tipping point where all the glaciers will melt and the coastal cities will flood along with assorted other disasters.
        Since 1998 we have been spewing CO2, yet the Earth has not gotten any warmer, contrary to the warmists’ predictions.

  8. GoFigure560 says :

    If I strike a match, I’ve contributed to global warming,….. but, so what?

  9. Will Nitschke says :

    “Why all the fuss?”

    That would seem to suggest that the IPCC claim that more than 50% of the warming is human, is only supported by 1.6% of the published literature. Which is not necessarily a problem except that a greater % specifically reject the claim. Of course none of this is important unless you accept the premise that scientific knowledge is advanced by means of some sort of democratic voting process. I guess that’s why the best estimate for warming by the year 2100 was based on a democratic vote count of climate models. The “model mean”. At least… it was until the last report where 97% were found to be wrong. 😉

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