Scientists agree on climate change: How should we communicate that?

Scientists agree: humans are causing climate change, and if we don’t drastically change our behavior, there will be catastrophic consequences.

The Consensus Handbook, a recent publication by communication researchers John Cook, Sander van der Linden, Edward Maibach, and Stephen Lewandowsky provides a clear and concise compilation of research on communicating scientists’ consensus on climate change. Here are some of my highlights from the report*.

First, what percentage of scientists agree? There are a number of ways to measure consensus — examining published research, surveying scientists, or studying public statements made by scientists, for example.¬†Different researchers have studied this question in a variety of ways, but each result has suggested that 91-100% of climate scientists agree that human-caused climate change is occurring. The majority of these studies actually converge on the estimate the 97% of scientists agree, which is why many of the studies that research the effects of consensus messaging use that number. Regardless, agreement is high. Climate scientist Katharine Hayhoe addresses this consensus in a great video on her channel Global Weirding.

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Does the public realize how high scientific consensus is? No.

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Why is there a gap between public perception of scientific agreement and actual scientific agreement? There are two primary culprits. The first, the authors refer to as a “cultural bias.” On average, people who are more conservative report lower consensus than those that are farther to the left. This report doesn’t delve into too much detail on the role of people’s ideological worldview in shaping how they think about climate change, but work by Dan Kahan (which I’ve written about here) is one resource for learning more about that.

The second — and larger — cause of the perception gap is a combination of a lack of information and misinformation. Misinformation campaigns have been relatively successful at confusing the public about scientific consensus on climate change. The most notable is probably the Global Warming Petition Project, in which “people” (some of whom are not real people and many of whom are not scientists) have signed a petition urging the US government to reject global warming agreements.

Adding fuel to the misinformation fire, the media often shows contrarian and climate scientist opinions in comparable ways, suggesting that there is a balance and that climate change is still an issue of debate among scientists.

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Why is it important for the public to know the true consensus on climate change? Research has shown that it’s a gateway belief:

what people think about expert agreement influences a range of other key climate attitudes, including whether global warming is real, caused by humans, resulting in serious impacts and importantly, whether we should act to solve it.

Since communicating consensus is also helpful for encouraging people to embrace other crucial beliefs held by climate scientists, the authors comment that “the 97% consensus offers a lot of bang for one‚Äôs communication¬†buck.”

Given the importance of understanding scientific consensus, how should we communicate about it? The handbook offers a number of evidence-driven suggestions:

  • Use the number (97%). This is more effective than a description of the consensus as “an overwhelming majority” for convincing people of the reality of the consensus.
  • Consider a pie chart to show consensus. A study led by van der Linden (which I’ve written about previously) showed that the pie chart was more convincing than a simple description or analogy.
  • Encourage people to estimate consensus first.¬†Revealing the consensus after people have estimated it has been shown to be more influential than simply revealing the same information.
  • Inoculate against misinformation¬†(I’ve also written about this strategy).¬†Research shows that people can encounter misinformation about the consensus and still come away with favorable climate attitudes if they’ve been warned about tactics that contrarians often use before they encounter them.

These are all promising tactics for communicating the climate change consensus, but amid these nuanced strategies, we should also not lose sight of the golden rule:

  • People need to encounter straightforward and¬†clear messages that are repeated often and from a range of sources.

*All are figures from Cook, J., van der Linden, S., Maibach, E., & Lewandowsky, S. (2018). The Consensus Handbook. DOI:10.13021/G8MM6P. Available at http://www.climatechangecommunication.org/all/consensus-handbook/

Cover image from NASA: https://www.nasa.gov/topics/earth/images/index.html

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Scientists Agree on Climate Change: A Gateway Belief

 

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https://climate.nasa.gov/scientific-consensus/

It doesn’t get much clearer. The Earth’s climate is warming. Humans are the reason. But how many people are actually aware of the scientific consensus on this issue?

Research by Sander van der Linden and colleagues shows that when people believe that scientists overwhelmingly agree about climate change, they increase their a) own beliefs in climate change and b) beliefs that humans are responsible. They feel c) more worried about climate change, and as a result of a, b, and c, they support public action to mitigate the effects of climate change.

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At the beginning of the study, participants indicated the percentage of scientists they thought agree on global warming and they answered some questions about their own climate change beliefs. People then received a message about scientific consensus, which took the form either of a) a simple description, b) a pie chart, or c) a metaphorical comparison related to¬†trusting engineers’ consensus about bridges (i.e., if 97% of engineers agreed that a bridge was unsafe, would you use it?) or doctors’ consensus about illness. All the messages included the info that¬†‚Äú97‚ÄČ% of climate scientists have concluded that human-caused climate change is happening.‚ÄĚ

Then participants again indicated what percent of scientists they thought agree on global warming and answered questions about their own beliefs. All messages “worked,” in the sense that people perceived greater scientific agreement after the messages telling them that 97% of scientists agree than if they hadn’t read anything about the consensus at all (though the simple description and pie chart were more effective than the metaphor. People shifted their climate change beliefs more after encountering one of the more straightforward messages than the more complex metaphor. Great food for thought, as many science communicators insert metaphors wherever they can).

Of course, having people believe¬†that there’s strong scientific consensus about climate¬†is only one¬†step toward the larger goal of having them endorse actions that mitigate the effects of climate change. But in follow-up analyses, the researchers identified that perceiving scientific agreement¬†is a gateway belief: believing that scientists agree about global warming¬†led to other beliefs, ones that get us closer to the goal of actions in favor of mitigating climate change. Specifically, it led to greater belief that climate change was real, human-caused, and worrisome. These beliefs, in turn, led to greater support for public action against climate change. It’s often hard to know what leads to what, especially when it comes to beliefs we keep hidden in our own heads, but with some semi-fancy math, these researchers¬†quantified those relationships.

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Climate 365 by NASA Goddard Space Space Flight Center. CC BY.

These studies have some clear takeaways for science communicators (especially when communicating about climate change — but maybe these ideas apply to other topics too — need more research!)

  • Emphasize scientific consensus, that an overwhelming percentage of scientists agree that climate change is a real problem caused by human activity.
  • Don’t worry so much about immediately pushing for public action against climate change. When people understand that scientists agree, they come to agree themselves that climate change is a problem that should be addressed, and THEN they come to support public action. Be careful about skipping steps.

At the same time, there’s not only one right way to communicate about climate change. There are truly effective ways, ineffective and potentially backfiring ways, and many in between. There aren’t cut-and-dry rules because every audience is unique, and taking the audience into account — their beliefs, values, and past experiences, for example — is crucial. But this work sheds light on communication strategies that are probably pretty far toward the “truly effective” end of the ways-to-communicate-climate-change continuum.