As I wrote yesterday, “I have written several times about the 2012 survey by Bart Verheggen and theNetherlands Environmental Survey. However, the climate blogosphere has started to look at it and is coming to some incorrect conclusions. But that’s okay, Bart himself is pushing a skewed interpretation of the results, so let’s look at it again.”
The report of Verheggen and his team is found here.
Verheggen’s survey was intended to measure how robust the scientific consensus is on climate change. As the report notes in the Introduction, “The general public is strongly divided over the question of human causation of climate change. Many believe that climate scientists are equally divided with respect to the same question, in contrast to what several studies have found. Perceptions about the level of agreement or disagreement among scientists influence people’s acceptance of scientific conclusions and their support for related policies.Public perception of climate change and of the scientific consensus on the subject, in turn, is influenced by ethical, social, and political values and attitudes.”
So it is very surprising that a survey intended to measure the consensus goes to such great lengths to avoid telling us what the answer is.
The answer is very clearly found in the data. Sixty-six percent (66%) of the respondents to the survey believe half or more of recent warming is attributable to human emissions of CO2.
That is the answer.
Now look at the only mention of that figure in the report: “There are two ways of expressing the level of consensus, based on these data: as a fraction of the total number of respondents (including undetermined responses), or as a fraction of the number of respondents who gave a quantitative or qualitative judgment (excluding undetermined answers). The former estimate cannot exceed 78% based on Q1, since 22% of respondents gave an undetermined answer. A ratio expressed this way gives the appearance of a lower level of agreement. However, this is a consequence of the question being difficult to answer, due to the level of precision in the answer options, rather than it being a sign of less agreement.
As a fraction of the total, the level of agreement based on Q1 and Q3 was 66% and 83%, respectively, for all respondents, and 77% and 89%, respectively, for the quartile with the highest number of self-declared publications. As a fraction of those who expressed an opinion (i.e., excluding the undetermined answers), the level of agreement based on Q1 and Q3 was 84% and 86%, respectively, for all respondents, and 91% and 92%, respectively, for the quartile with the highest number of self-declared publications.”
In journalism that is known as ‘burying the lede.’ In climate science it is perhaps best known as ‘hiding the decline,’ in this case the decline in the consensus from the 97% invented by pseudo-scientist John Cook (who is actually a cartoonist), who actually is part of Verheggen’s team.
I don’t care what the percentage is for the quartile with the highest number of self-declared publications. (Number of publications is a notoriously poor indicator of expertise in science, although it is a good indicator of networking ability and writing skills.) How strong is the consensus?
I don’t care what the fraction is of those who expressed an opinion. ‘I don’t know’ is a valid answer to this question. (Surveyors will sometimes remove those saying ‘I don’t know’ to questions like “Do you prefer the purple car or the red car?” But never for a question like this.) How strong is the consensus?
And I most certainly don’t care that the question is ‘difficult to answer.’ It’s a difficult question. Had you consulted me or any of 10,000 market researchers with the requisite level of skill in writing surveys we could have made it a bit easier for respondents to express their true perceptions on this issue. But this is the question you have and these are the answers you have.
It is painfully obvious they are trying to bury the answer. They refer to it as Q1, not as the question that inspired the survey. They conflate it in the same sentence with a follow up question. In the same paragraph they try to dilute its impact by citing higher percentages for sub-groups of respondents, those with a high number of publications and the total of those who didn’t say ‘I don’t know.’
So, Bart, here is my question. What percentage of practicing climate scientists believe half or more of recent warming is caused by human emissions of CO2?
Any answer other than 66% is dishonest.
The survey done by Verheggen et al is a good survey. The data they gathered is useful, relevant and important.
The report–not so much.