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

Cover image from NASA:


TLDR Guide to Communicating Science Effectively: CHAPTER 3

For the past two days, I’ve posted my highlights of the 127-page guide for communicating science¬†and research agenda published by the National Academies of Science (ch1, ch2). Today I’m sharing my highlights from Chapter 3.

Chapter 3: Nature of science-related public controversies

There’s no shortage of controversial science issues to communicate about:

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The report points out three features that controversial science issues often share:

  1. Conflicting beliefs, values, and interests of individuals and organizations are central
  2. The public perceives that the science itself or its implications are uncertain
  3. Influential groups and people succeed in having their voices heard above many others, making it hard for scientific evidence to come through

Religious views in particular can play a more central role in beliefs about controversial science issues than political ideology:

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There are some strategies for reducing the effects of competing beliefs, values, and interests (1 above):

  • Tailoring messages from science for understanding and persuasion
    • When information is presented in a way that’s consistent with people’s values, they tend to be more open-minded about the message than when the same information is presented inconsistently.
    • Audience Segmentation: the practice of dividing a large potential audience into subgroups and tailoring messages differently for each subgroup. Research on this area is very new, but it has the potential to help researchers understand how much of an effect science communication can have, for whom, and in what contexts
  • Engaging the public
    • The most effective public engagement happens as early as possible in a public debate, and stakeholders should¬†be engaged over many rounds of discussion. “Repeated deliberation over time builds trust.” (p. 58)
    • We need more research to understand the structures and processes that encourage effective science communication in public forums across a range of issues and controversies.


Research also suggests some ways to deal with public perceptions of uncertainty (issue 2 above):

  • When there are inaccurate claims of uncertainty (for example, claims that not all scientists believe climate change is a result of human activity), it can be useful to use repeated communications to convey the extent of expert agreement. These communications should occur in a variety of places, involve diverse people, and take many forms, like conversations, social media, presentations, advertising, communication campaigns, and media interviews.
  • It also seems beneficial to be explicit about the uncertainty that’s present in scientific understanding, and particularly depicting how uncertainty decreases over time. This tactic might build credibility and also garner public interest in a scientific story that unfolds¬†over time.
  • But more research is needed on the most effective ways of presenting risks of varying degrees of uncertainty

Finally, the report discusses strategies for ensuring that science is heard among amplified voices of organized interests and influential individuals (issue 3 above):

  • Debunking misinformation
    This can be especially difficult when the false belief is consistent with how people already think about an issue. Communicators should be aware that repeating false information, even if doing so in order to correct it, may reinforce the belief. Corrections may be ineffective if inaccurate information as been repeated enough already. One strategy is to “prebunk” the information when possible by warning people that they might encounter misinformation and explaining why that information is being promoted. But more research is needed to reveal when and for whom this is an optimal strategy.
  • Work with opinion leaders to inform and persuade

This chapter confronts a major hair-pulling issue for science communicators. While communicating science might be hard to begin with, communicating about controversial issues seems at times impossible. The chapter shines light on what prior research can show us about effective communication despite an issue’s controversial nature and articulates areas for future research to continue improving in this direction.

Tomorrow I’ll break down chapter 4: Communicating science in a complex, competitive communication environment.