Principle 2: Communicate Consensus
People are more likely to believe climate change is happening and caused by human beings if they understand that the scientific evidence justifies these conclusions and that there is a scientific consensus about both.
Individuals鈥 beliefs about climate change are influenced by what they think scientists believe (Lewandowsky, Gignac, and Vaughan 2013). Communicating that there is a scientific consensus about the existence, harmful nature, and need to address climate change can increase acceptance of the existence of human-caused global warming (Bolsen, Leeper, and Shapiro 2014; van der Linden, Leiserowitz, and Maibach 2018). Accepting the scientific consensus about climate change can act as a 鈥済ateway belief鈥 to understanding and engaging with other dimensions of the issue (van der Linden et al. 2015). Consensus messaging of this sort works by using perception of widespread acceptance as a means of aligning individual perception with the descriptive norm (for an explanation of the process, see Tankard and Paluck 2017). A meta-analytic examination of the demographic and psychological correlates of belief in climate change found that belief in climate change was stronger among those who accept a source heuristic (鈥渟cientists are trustworthy so the scientific orthodoxy must be true鈥) and a consensus heuristic (鈥渢here is scientific consensus around climate change, and consensus implies correctness鈥) (Hornsey et al. 2016).
The challenge to be addressed:
For decades, the media tendency to imply the existence of two opposed but equally justified scientific positions on the nature, extent, and causes of climate change distorted the public鈥檚 perception of the extent of agreement among published climate scientists (Boykoff and Boykoff 2004; Koehler 2016). At the same time, those with a vested interest in sustaining fossil fuel use (Farrell 2016; Supran and Oreskes 2017) were seeding doubts about the extent of scientific agreement (Oreskes and Conway 2011). Worrisomely, a recent meta-analysis concluded that 鈥渂elief in climate change is more easily weakened than strengthened鈥 (Rode et al. 2021). Consensus uncertainty鈥攁 disagreement among experts or about the existence or strength of evidence鈥攊s the only kind that erodes a message鈥檚 credibility, according to a 2020 review of the literature on the effects of uncertainty in science (Gustafson and Rice 2020).
The climate science:
Since the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change, 鈥渉uman influence on the Earth鈥檚 climate has become unequivocal, increasingly apparent, and widespread, reflected in both the growing scientific literature and in the perception and experiences of people worldwide (high confidence)鈥 (Working Group II 2022).
An analysis of 11,944 climate abstracts from 1991鈥2011 matching the topics 鈥済lobal climate change鈥 or 鈥済lobal warming鈥 found that, 鈥渁mong abstracts expressing a position on AGW [anthropogenic global warming], 97.1% endorsed the consensus position that humans are causing global warming鈥 (Cook et al. 2013; see also Anderegg et al. 2010).
Example 1: Graphically communicating climate consensus
Source: van der Linden et al. 2014.
Effectiveness:
Descriptive text and a pie chart capsulizing the scientific consensus on human-caused climate change (鈥97% of climate scientists have concluded that human-caused climate change is happening,鈥 with the logo of the American Association for the Advancement of Science [AAAS]) were able to increase belief certainty about estimates of the scientific consensus (van der Linden et al. 2014; see also Goldberg, van der Linden, Ballew, Rosenthal, and Leiserowitz 2019).
Example 2: Communicating consensus through a pictograph
Source: Cook et al. 2013.
Effectiveness:
By using as a stimulus a graphic that visually represents the percentage of climate scientists who agree that climate change is caused by human activity, Cook and Lewandowsky (2016) found that, although providing consensus information did raise perceptions of consensus, the consensus messaging was potentially polarizing with American subjects who endorse free markets (i.e., hierarchical individualists attributing less expertise to climate scientists). But the consensus information did have a small worldview neutralizing effect on Australians.
Example 3: Dramatizing climate consensus
Source: Last Week Tonight with John Oliver 2014.
Effectiveness:
While climate scientists have generally represented the scientific consensus on climate change using graphs, a segment of HBO鈥檚 Last Week Tonight with John Oliver from 2014 has, as of October 2022, drawn more than 8.8 million YouTube views for a dramatization of what the show cast as 鈥渁 mathematically representative climate change debate.鈥 鈥淚t鈥檚 a little unwieldy,鈥 host John Oliver said, 鈥渂ut this is the only way we can actually have a representative discussion.鈥 The 鈥渙verwhelming view of the scientific community鈥 involved a lot of yelling and waving of files, leading Oliver to tell the denier: 鈥淚 can鈥檛 hear you over the weight of scientific evidence鈥 (Last Week Tonight with John Oliver 2014). 鈥淚f you look at the science,鈥 noted an article in The Atlantic, 鈥渞ather than just asking people on the street if they believe in global warming, it鈥檚 not a 50/50 debate between two sides鈥 (Beck 2014).
On the science podcast Inquiring Minds, science journalist Chris Mooney praised both Oliver鈥檚 concision and effectiveness: 鈥淚 feel like they said in 4 minutes something I鈥檝e been saying for 10 years with like tens or hundreds of thousands of words; what they said was that there鈥檚 no debate over global warming, so to have these 鈥榖alanced鈥 1-on-1 TV debates is just preposterous鈥 (Nuccitelli 2014).
Effectiveness:
Findings from a randomized experiment showed that viewing the Oliver segment increased viewers鈥 belief in global warming and perceptions that most scientists believe in its existence (Brewer and McKnight 2017).
Example 4: Communicating consensus through analogy
Source: Science Moms 2021a.
Effectiveness:
Using analogy to convey the scientific consensus, a team of scholars found that belief in human-caused global warming increased as an issue of concern, as did its priority after subjects in a controlled experiment were exposed to either a speaker in the video or print text reading, 鈥淚f 97% of all dentists told you a tooth couldn鈥檛 be saved, you鈥檇 pull that tooth. If 97% of all engineers told you your house was unstable, you鈥檇 move. And if 97% of all airline workers told you not to get on a plane, you wouldn鈥檛. So, when 97% of the world鈥檚 climate science experts tell you our planet is warming and we鈥檙e responsible, why would you ignore them? When you鈥檙e 97% certain, you鈥檙e certain. Protect America from climate change鈥 (Goldberg, van der Linden, Ballew, Rosenthal, Gustafson, Leiserowitz 2019).
The need:
Clear communication that uses trusted messengers to reiterate the scientific consensus that climate change is happening and increasing the likelihood or severity of heat waves, fires, flooding, droughts, and hurricanes.