Appeals to the climate consensus can give the wrong impression

Credit John Cook 2014

Image credit John Cook, Closing the Consensus Gap on Climate Change

Dr. Will Howard, recently published an essay that will appeal to those of you interested in science communications, especially in the challenging and politically-charged context of climate change. Dr. Howard makes the extremely important point that “scientific consensus” on climate change reflects strong consilience of evidence. I confess that I had to look up “consilience” to learn that it is indeed the perfect term to capture how we have developed confidence in our understanding of the causal connections between human-generated greenhouse gases and climate change.

In public discourse, if we had chosen “consilience of evidence” to describe the accumulation of research, then perhaps people might have understood more readily that we are not talking about the results of an opinion poll or a negotiated statement (yes, the IPCC Summary for Policymakers [PDF] is a negotiated statement, though I don’t know how else such a summary could be produced).

I thought Will’s essay captured this science communications challenge succinctly, and especially how this strong consilience of evidence is separate from the politics of what to do about it:

“Consensus” is understood differently in science compared to politics or society.

Scientists use this word to refer to consilience of multiple lines of evidence that underlie widespread agreement or support a theory.

In the case of climate change, multiple lines of evidence underpin the prevailing view that the climate system is showing decade-on-decade warming over the past 50 years.

In particular, this warming bears temporal and spatial patterns, or “fingerprints”, that point to human causes.

For example, the stratosphere (that part of the atmosphere higher than about 11 km) has been cooling as the lower atmosphere and the ocean warm. This is the pattern we expect from the addition of greenhouse gases and not from, say, changes in the sun’s output.

But in public and especially political discourse, “consensus” tends to imply majority opinion or concurrence. As consensus in this public context is often arrived at by negotiation, saying there’s a scientific “consensus” may imply to the community that prevailing scientific views represent a negotiated outcome. This is the antithesis of science.

Consensus of the non-scientific kind does have a role to play in the climate debate. This includes negotiating whether warming is a “good” or “bad” thing and what, if anything, we should do about it.

These are not scientific questions. These are issues of values, politics, ethics and economics. As a nation and as a global society we need to reach consensus to resolve those questions and to make and implement appropriate public policy.

I’ve nothing to add to Will’s excellent essay, so I recommend that you go directly to The Conversation to read the original and the comments. Some effort is required to weed the growing number of comments so I will highlight a segment of the conversation which focuses upon the important question of effective science communication:

John Cook
Climate Communication Research Fellow at University of Queensland

This is an interesting article with many important points. I would be the first person to stress the importance of communicating the many “fingerprints” being observed in our climate (and in fact have created a human fingerprints infographic which I frequently use in public talks

However, the article is missing a crucial element to this discussion – what does the evidence tell us about the efficacy of consensus messaging? A number of studies have found that one of the strongest predictors of public support for climate mitigation policies is perception of consensus (i.e., the level of agreement among climate scientists about human-caused global warming). Also, consensus messaging significantly increases acceptance of climate change. A randomised experiment by Stephan Lewandowsky found that informing Australians of the 97% consensus increased their acceptance of human-caused global warming and intriguingly, the increase was greatest amongst conservatives. In this case, consensus neutralised ideology to some degree.

When people think there is still an ongoing debate about human-caused global warming amongst climate scientists, they’re less likely to accept climate change and support climate action. And given the Australian public on average think there is 58% agreement among climate scientists, rather than 97%, then this misconception has serious societal implications. Science communicators need to take into account that people use expert scientific opinion as a heuristic to inform their views on complex scientific issues.

To underscore this fact, I’ve actually tested the human fingerprints message (linked to above) and the consensus message in a randomised experiment. Consensus messaging significantly outperformed the fingerprints message. The lesson here is that we need to understand how laypeople think about complex scientific issues like climate change.

However, I don’t think there need be that much conflict between what social science is telling us and the views of the OP. A recent paper by Ed Maibach tested various forms of consensus messaging and they found the most effective was a message that emphasised both consensus and the evidence-based nature of the scientific method:

“Based on the evidence, 97% of climate scientists have concluded that human-caused climate change is happening”

John Cook
Climate Communication Research Fellow at University of Queensland
In reply to Anna Young

Anna, the problem you raise is exactly why communication like the John Oliver YouTube video embedded in the OP are so powerful. Not only does Oliver communicate the 97% consensus, he also does something equally important – he communicates how people cast doubt on the consensus (in this case, by perpetuating false balance in the media). What Oliver is doing is equipping people with the knowledge and the critical thinking skills so that when they see the mainstream media show a debate between a climate scientist and a tinfoil guy, they can see it for what it is. It’s not only a funny video, it’s brilliant communication. The fact that it’s been viewed millions of times means millions of people have now been “inoculated” against the misinformation of false debate in the mainstream media.

So kudos to Will Howard for embedding the video.

Will Howard
Research scientist at University of Melbourne
In reply to John Cook

Thanks John, for contributing that perspective. The points you raise, I would suggest, may be applicable to many areas of “contested” science, in health, resources (e.g. coal seam gas) and others. 

Whatever is said about the consensus, I do think we need to do a better job of communicating what underpins it. As your co-author Peter Jacobs notes

“to those suggesting that the consensus message is an appeal to authority that ignores evidence- the consensus exists *because of* the overwhelming physical evidence, which is detailed at length in the scientific literature.”

But I wonder about this: both the consensus and the consilience of evidence (my preferred term) seem to be strengthening, yet public support for policies aimed at mitigating climate change seem not to be.

I note polls suggesting climate change and environmental issues have moved down peoples’ priorities. Here in Australia, our current government was elected with a major plank in its platform being the removal of the carbon tax. (Whether we agree or disagree with their policy they ran on that issue and were elected).

Is this because people are skeptical of the science? Is it just that other issues take on more urgency: jobs, the economy, international conflicts, etc.?

John Cook
Climate Communication Research Fellow at University of Queensland
In reply to Will Howard

I like the term “consilience of evidence” also but when I test-drive it in public talks, it tends to inspire blank looks from the audience. It’s a term that scientists love. Laypeople, not so much. Which is why, again, it’s important that we understand our audience when we do science communication.

Why is public support not changing that much? Public concern about climate change does correlate with economic performance hence the drop in climate concern after the GFC. Another predictor of public concern about climate change is cues from our political leaders so you can see why Australia has a problem in that department at the moment. There’s certainly a number of factors that influence people’s attitudes to climate.

But as I said above, several recent studies have found perception of scientific agreement on climate change is one of the biggest factors. And given public perception of consensus is very low (I measured it at 58% on a representative Australian sample), this misconception is definitely a significant problem. It’s not the only factor delaying public support for climate action but it’s a big one.

Also, communicating the 97% consensus is a lot easier to understand than explanations of why greenhouse gases in the upper atmosphere are more efficient at radiating longwave radiation to space, hence contributing to the cooling stratosphere. From a communication point of view, consensus is a low lying fruit. This is why consensus messaging outperformed fingerprint messaging in my data.

So communicating the 97% consensus can help with removing one roadblock delaying climate action. It won’t fix everything – it’s not a magic bullet. But ignoring the “consensus gap” only serves to give extra life to that stumbling block.

I wrote a post a while back How to break the climate change gridlock including a conversation with  Andrew Dressler, Professor of Atmospheric Sciences at Texas A&M, about how we might more explicitly get each party’s values and economic interests on the negotiating table.

Will Howard has received funding from the Australian Research Council, the Australian Government Department of Climate Change, the Cooperative Research Centres Program, and the Australian Antarctic Science Program.


3 thoughts on “Appeals to the climate consensus can give the wrong impression

  1. Good point about the IPCC Summary for Policymakers. The working group reports’ technical summaries are better syntheses of the science, with less negotiation over wording.

    John Cook’s comments are quite valid. However they reflect that he and I were talking past one another about two different things, I think. I was not critiquing the use of “consensus” from the perspective of an activist seeking an “effective message” to build support for action. “Removing roadblocks” in his words.
    I see myself as a scientist first (think Roger Pielke Jr.’s spectrum). I am concerned about action on climate change (as a citizen/human being/parent). But I am also concerned about the effect of words like “consensus” on the perceived credibility and integrity of science.

  2. There’s a lot of discussion about “consensus” messaging and its efficacy, debate about whether the “consensus” is 97% or 90%.

    Looking around the world at climate policies and the continued rise of emissions, I wonder how that “consensus messaging” is working out so far? I think it’s too easy to overcome. Just haul out a few dissenters. And there will always be some…

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