Against ‘consensus’ messaging

cartoon settled scienceA decades’ experience shows that “Consensus messaging” doesn’t work. – Dan Kahan

Two weeks ago, Bristol University hosted a debate between Stefan Lewandowsky and Dan Kahan [link].

What is the best way to communicate the risks from climate change to the public? Dan Kahan has been championing the idea that risk perception depends on one’s culture or “worldview”, with people on the political right being more likely to downplay the risks from climate change than people on the political left. Stephan Lewandowsky has also found support for this notion in his own research, but he additionally finds that knowledge of the pervasive scientific consensus about global warming is a “gateway belief” that shapes people’s acceptance of the science and their willingness to support mitigation policies. So what are the implications of those two positions? Do they permit synergy or are they locked in opposition? Is there a third way to communicate science?

Dan Kahan has a blog post with his remarks [link (including link to Kahan’s slides], excerpts:

First, I’m not against the proposition that there is a scientific consensus that human activity is causing climate change. Second, I am by no means against communicating scientific consensus on climate change.

The proposition I am against is that the way to dispel polarization over global warming in the U.S. is to continue a decade’s long “social marketing campaign”—one on which literally hundreds of millions of dollars have already been spent—that features the claim that “97% [or 98% or 100% etc] of scientists accept human caused climate change.”

I am against that this “communication strategy”–

  • first, because it misunderstands the nature of the problem;
  • second, because it diverts resources from alternative approaches that have a much better prospect for success; and
  • third, because it predictably reinforces the toxicity of the climate change debate for our science communication environment.

But both “liberals” and “conservatives” have “gotten the memo” that scientists think human activity is causing climate change and that we are in deep shit as a result. So why should we expect that telling them what they already know will dispel the controversy reflected in persisting poll results showing that they are polarized on global warming?

You see, there are really two “climate changes” in America.

There’s the one people “believe in” or “disbelieve in” solely for the purpose of expressing their allegiance in a mean, ugly, illiberal status competition between opposing cultural groups.

Then there’s the one that people “believe in” in order to do things—like being a farmer—that depend on the best available scientific evidence.

As you can imagine, it’s a challenge for a legislator to keep all this straight.

JC comment:  Kahan gets it partly right – there are indeed two climate changes.  But IMO he misunderstand what they are.  There is human caused climate change, and then there is natural climate variability.  Farmers don’t care so much about what is causing climate variability change; rather their job is to continually assess weather/climate risks to their crops and then adapt.  This split is discussed in my previous post Nonsensus about the Senate’s non consensus on climate change.

The only way to promote constructive collective decsionmaking on the climate change that ordinary people, left and right, are worried about,and that farmers and other practical individuals are taking steps to protect themselves from, is to protect our science communication enviornment from the toxic effects of the other climate change change—the one that people believe or disbelieve in to express their tribal loyalties.

Public opinion on climate change—whether it is “happening,” is “human caused,” etc.—didn’t move an inch at all during that time.

But we are supposed to think that that’s irrelevant because immediately after experimenters told them “97% of scientists accept climate change,” a group of study subjects, while not changing their own positions on whether climate change is happening, increased by a very small amount their expressed estimate of the percentage of scientists who believe in climate change? Seriously?

Perpetuating a toxic discourse. No doubt part of the appeal of “consensus messaging” is how well suited it is as an idiom for expressing contempt. The kinds of real-world “messaging campaigns” that feature the “97% agree” slogan all say “you are an idiot” to those for whom not believing climate change has become identity defining. It is exactly that social meaning that must be removed from the climate change question before people can answer it with what they know: that their well-being and the well-being of others they actually care about requires doing sensible things with the best available current evidence.

JC comment:  I think that the above paragraph is spot on.  Not only is it toxic to the public debate on climate change, but its toxicity also extends to the scientific debate

A decades’ experience shows that “Consensus messaging” doesn’t work. Our best lab and field studies, as well as a wealth of relevant experience by people who are doing meaningful communciation and not just fielding surveys, tell us why: it is unresponsive to the actual dynamics driving the climate change controversy.

Time to give alternative approaches–ones that reflect rather than ignore evidence of the mechanisms of cultural conflict over societal risks–a fair trial, during which we can observe and measure their effects, and after which we can revise our understandings once more, incorporate what we have learned into refined approaches, and repeat the process yet again.

Otherwise the “science of science communication” isn’t scientific at all.

JC reflections

While I find Dan Kahan’s research and perspectives to be very interesting, all of this science of science communication strategy for climate messaging runs dangerously close to propaganda techniques.

Consensus ‘messaging’ has been pernicious to the science, as well as to public perception of science, which is discussed in my paper No consensus on consensus.

My long standing recommendation has been to drop the consensus messaging.  Scientists should make a clear statement about what we understand with confidence, what we think might happen, and what the major uncertainties are.  This is generally what the IPCC First Assessment Report did.  The ‘consensus’ strategy was put into play for subsequent reports.

After reading Kahan’s stuff, I wish he would apply his methods to understanding people who believe the scientific consensus on climate change (both scientists and the public).


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    From a purely logical perspective science is not built upon consensus, and science is never “settled”. It should be axiomatic.

    However, when the AGW movement started promoting the idea that man-made global warming was [i]settled science[/i] it blew right through the definition of absurdity.

    This claim is based on impossibly complicated and ever-changing theoretical scientific [u]MODELS[/u]; the most debatable and dubious form of scientific endeavor short of alchemy. Flow charts alone for these models look like a massive explosion at a spaghetti factory, and we learn almost daily how whole segments are often fudged, ignored, or completely omitted to achieve desired results. Settled? Really?

    Researchers who would dare propose studies that [i]might[/i] contradict the AGW meme are overtly ignored by a massive, politically-controlled funding apparatus while those who openly question existing results or methods are shunned by their peers. Hardly an environment for discovery and truth.

    Unless this crime against science is quickly, thoroughly, and openly rebuked with truth, this time will become known as the onset of a dark age for science.

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