I get my kicks on the Route to 66… Percent Consensus

Sorry to bore all of you with my third post in as many days regarding Bart Verheggen’s survey of climate scientists.

However, it’s important to highlight defects of their reporting scheme before John Cook starts trumpeting it all over the intertubes as support for his nonsensical 97% consensus.

Verheggen’s survey is good. His report is not.  The data shows clearly that the percentage of scientists who think half or more of recent warming is caused by human emissions of greenhouse gases is 66%. He almost point blank refused to use that figure, preferring to show the higher percentage of agreement among scientists who claim to have more publications under their name.

Route 66

Over at Bart’s weblog, he writes this in justification for his decisions:


I disagree with this conclusion of yours:

Those answering ‘I don’t know’ need to be included in your calculations of a consensus, precisely because they do not form part of the consensus.

For the reasons given in this post. Many of those who answered I don’t know, unknown, or other, could realistically be expected to form part of the consensus in terms of thinking warming is predominantly human induced. That is clear from comparing the answers to Q1 to the answers to Q3 and from the responses to the open question box with Q1.”

Bart–could? Could?

Bart continues, “To substantiate your approach, you’d need to answer types of questions such as:

What is your explanation for the large number of undetermined answers to Q1?”

The explanation is simple. It is a difficult question and many scientists honestly do not know the answer. Many may believe it is possible but not shown or not proven, that half or more of the recent warming is due to human emissions.

That is why they count as part of the global response to your question and do not count as part of the consensus.

You continue: “How would you explain the big difference between Q1 and Q3 based on your preferred approach of including the large fraction of undetermined answers?”

First of all, why do you neglect Q2 in trying to understand Q1 and Q3? In Q2, only 32% say the long term trend has changed. An equal percentage say the trend is masked by short term variation and 24% say it is impossible to state. To me that fully explains the percentage who say they don’t know to Q1 and still attribute warming to concrete causes in Q3.

Bart: “How would you think the same sample of scientists would have responded if we had asked one of the questions I discussed in the post, namely:

Imagine that we had asked whether respondents agreed with the AR4 statement on attribution, yes or no. I am confident that the resulting fraction of yes-responses would (far) exceed 66%. We chose instead to ask a more detailed question, and add other answer options for those who felt unwilling or unable to provide a quantitative answer. On the other hand, imagine if we had respondents choose whether the greenhouse gas contribution was -200, -199, …-2, -1, 0, 1, 2, … 99, 100, 101, …200% of the observed warming. The question would have been very difficult to answer to that level of precision. Perhaps only a handful would have ventured a guess and the vast majority would have picked one of the undetermined answer options (“I don’t know”, “unknown”, “other”). Should we in that case have concluded that the level of consensus is only a meagre few percentage points? I think not, since the result would be a direct consequence of the answer options being perceived as too difficult to meaningfully choose from.

Do you disagree with this quoted paragraph? If so, why?”

Umm, Bart–it doesn’t work that way. The way to quantify a consensus is to count those who raise their hands  when you ask them if they agree. It is only those who actively volunteer who form part of the consensus.

If you think more would agree with the AR4 attribution statements, ask them. Your confidence in the answers you think they would provide is admirable. But don’t pretend that it was asked and answered in your survey. Your argument as reproduced here indicates that the consensus is so weak that only precise phrasing can bring it to light. If it’s robust (and 66% is robust–it just isn’t 97%) then you don’t have to make excuses for those who say they don’t know.

I wish you had asked for help on this. There is a battery of questions you can use to get this information.

As it stands, you are saying those who answer ‘I don’t know’ should be eliminated from the total. That’s an incorrect choice for honest analysis.

As for the publications thingy, that’s just hand-waving. ‘Look over here, the numbers are higher!’

You need to show why you think higher numbers of (self-declared) publications are an indicator of a higher level of expertise for it even to be relevant. And you don’t even try.

Younger scientists may have been educated with more up-to-date information and even techniques. They may be far more expert that old fuddie duddies who sit in a room writing papers.

A brilliant scientist might write one paper as a single author who sheds significant light on a subject, while  her colleague might get his name onto 15 different papers as a co-author without doing anything significant.

Authors who don’t agree with the consensus may be keeping their head down. Worse, they may face a wall of dissent from the consensus when they seek to publish.


8 responses to “I get my kicks on the Route to 66… Percent Consensus

  1. Bart is like a fundamentalist preacher who understands the science about evolution but refuses to accept it because it might interfere with his preaching gig.
    He is just rationalizing away anything that is counter to his lucrative catastrophic cliamte preaching. That the climate madness got a scientific illiterate like Mr. Obama makes sense. He does know squat about the issue, but he likes how he can give his pals tax money and hurt his enemies and kid himself he is a strong leader. That a lunatic like Hansen is obsessed with climate doom is understandable. But Bart, on the surface at least, seems like a reasonable person.

    • Hiya Hunter,

      Bart is reasonable. And he’s a nice man as well. But I fear he has adopted a very rigorous stance on this.

      I must say I’m not impressed by the fact he collaborated with John Cook on his paper.

      • I know plenty of nice fundies who reject evolution as well.
        The unwillingness of very many “mainstream scientists to reject Ehrlich on the large end of the scale, or even Cook on the ankle biter end of the scale, speaks volumes about human weaknesses.

  2. Respondents who listed climate impacts outnumbered those who listed attribution by 7 to 1.
    About 55 of the respondents listed attribution as their expertise. That’s a representative sample. He could have listed their responses separately. He didn’t. That’s the story.

  3. Sorry to post something off topic, but I found this to be fascinating:
    Well it is not really so far off topic. It does shed some light on the morphing of climate science into the hysterical mania it has become.

  4. Any scientist who has done opinion research, whether on climate science or the taste of chocolate bars know that the first, most important variable in a survey is the wording of the questions. A good survey repeats the same questions with different wording to measure how astute the respondents are.
    Any scientist who has done opinion research, whether on climate science or the taste of chocolate bars know that the first, most important variable in a survey is the wording of the questions. A good survey repeats the same questions with different wording to measure how astute the respondents are.
    The very first question in Mr. Verheggen’s survey-
    What fraction of global warming since the mid 20th century can be attributed to human induced increases in atmospheric greenhouse gas (GHG) concentrations? –
    is very problematical. It has ten logically disconnected answers making it nearly imposssible to answer. The first six are an unbounded scale from over 100% to less than 0% and 4 25% categories in between. Then- there has been no warming, the same as zero percent. and two equivalent categories – Unknown due to lack of knowledge and -I don’t know-, followed by -other(please specify).
    Since most of the respondents were directly involved in climate science they would likely now what was going on here and be familiar with the IPCC reports and answer in the top two bracets. As scientists, any self-respecting person would not go over 100%, especially when it has already been specified as aerosol cooling, or admit to unknown due to lack of knowledge(on the respondent’s part) or admit to just general lack of knowledge. The question, wittingly or not, presupposes some answers and disrupts the whole thought process for the respondent.
    All of the other questions appear to have similar problems of confused presentation, mixing observations with opinions, assigning political opinions to policies, and numerous other problems that would all tend to invalidate any results.
    Consultation with a statistician and an opinion reearch psychologist could have greatly improved the reliability of the results. As it stands, this survey is worse than useless because it implies validity it doesn’t have.

    • Phil,
      The assumption that the climate science faithful are trying to actually research the issue for knowledgeable insights is, in my observation of the movement, mistaken.

  5. Pingback: Once more on Verheggen et al while I squeegee water out of my apartment | The Lukewarmer's Way

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