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.
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 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.