Consensus On Consensus

One of the things about the field of climate science that I find particularly striking is the way rigorous debate about so many diverse issues co-exists with a ubiquitous consensus about the fundamental facts that greenhouse gas emissions from our economic activities are warming the planet. Indeed, of all the silly things that have been said about the climate by political operatives and others who cannot accept the 150-year old physics of greenhouse warming for ideological reasons, perhaps the silliest is the claim that scientists do not agree about those fundamental physics.

Anyone who believes that has obviously never been to a meeting of the American Geophysical Union (AGU). I have attended multiple times, and the idea that there is disagreement about greenhouse warming among domain experts is just plainly and completely wrong. There is no kinder way of putting this: the consensus is not a matter of opinion, it’s a matter of fact. And the fact is that I have never heard anyone at an AGU meeting dispute that greenhouse gases are a major contributor to the observed global warming during the last 30-50 years. Nor are there any debates about greenhouse warming during those meetings—as is easily ascertained by perusing the conference program.

Given that recognition of the expert consensus is a gateway belief that determines the public’s attitudes toward climate policies, and given that informing people of the consensus demonstrably shifts their opinions, it is unsurprising that attempts continue to be made to deny the existence of this pervasive expert consensus.

Like other forms of disinformation, this denial of the expert consensus impinges on the public’s right to be adequately informed about the risks it is facing. It is therefore potentially ethically dubious. However, disinformation also provides an opportunity for agnotology—that is, learning from the analysis of mistakes and misrepresentations.

An article appeared today in Environmental Research Letters that takes on the disinformation about the scientific consensus. It is aptly entitled Consensus on Consensus and it is authored by a veritable who-is-who of research on the consensus (myself included).

The essence of the article is encapsulated in the figure below, which shows the expert consensus—measured as the percentage agreement on the fundamental premise that the planet is warming from greenhouse gas emissions—across a large number of studies published during the last decade (for the coding of the observations, refer to the original article).

It is clear that as expertise increases, so does the consensus. And the greater the precision of the data (represented by smaller uncertainty bounds), the higher the consensus.

And if you want to know more, here is a four-minute concise summary of the results of our study: