Everyone agrees that global warming has become a polarized issue. Liberals tend to view themselves as being on Team Human-Caused Global Warming is a Problem, and conservatives tend to view themselves on Team No It’s Not. Convincing people to change their beliefs and leave their cultural group is a challenge with any polarized subject.



When it comes to climate change, the scientific evidence falls squarely behind the first team, and so the question becomes how we reduce the polarization that makes so many people culturally identify with second team. That’s a question social scientists have been grappling with for years.

One suggested approach involves consensus messaging – telling people about the 97% expert consensus on human-caused global warming. People tend to badly underestimate the expert consensus on this issue, and research has shown that communicating the 97% consensus makes people more likely to accept the scientific reality of human-caused global warming and the need to do something about the threats it poses.

Expert Consensus is a Gateway Belief



A new study by social scientists at Princeton, Yale, and George Mason universities goes further yet to suggest that perception of the expert consensus is a “gateway belief” that opens people to the acceptance of other important concepts.



increasing public perceptions of the scientific consensus causes a significant increase in the belief that climate change is (a) happening, (b) human-caused and (c) a worrisome problem. In turn, changes in these key beliefs lead to increased support for public action. In sum, these findings provide the strongest evidence to date that public understanding of the scientific consensus is consequential.

The study illustrates “the gateway belief model” in the following figure.



The Gateway Belief Model. Photograph: PLOS ONE

In the study, the scientists asked people to rate their beliefs about these key issues before and after being told about the 97% expert consensus. The results validated the model. Subjects’ perceived expert consensus increased dramatically, and their belief in climate change, its human causation, concern about it, and support for public action all increased as well.



Overview of sample characteristics and key belief measures in van der Linden (2015). Photograph: PLOS ONE

The increase in concern about climate change is a key result. Most people, including a majority of Republicans, support taking action to slow global warming. But they view it as a low priority, so they don’t mind when policymakers fail to take action. Hence there’s no penalty for climate denial in Congress, whereas there’s a big financial reward from the fossil fuel industry for delaying climate action. That calculation won’t change until people view tackling global warming as a higher priority. This study suggests that consensus messaging may help people grasp the importance of the problem.



The gateway belief model makes sense because people don’t have the time to learn about every important issue, so we often defer to the experts. As shown by a 2013 study led by Stephan Lewandowsky,



when in doubt about scientific facts, people are likely to use consensus among domain experts as a heuristic to guide their beliefs and behavior.

Dan Kahan at Yale is also a social scientist, and has argued that consensus messaging is “counterproductive” and “deepens polarization.” However, both Lewandowsky’s research and this new study find that consensus messaging “neutralizes the effect of worldview” because “Republican subjects responded particularly well to the scientific consensus message.” Especially when they saw it in pie chart form.



Geoengineering Messaging



Kahan prefers to reduce polarization about climate change by telling people about geoengineering. He’s run experiments in which subjects read a fictional article about new technologies to offset global warming by removing carbon dioxide from the atmosphere, and reflecting sunlight into space. After reading the fictional article, conservatives become more likely to accept the science behind human-caused global warming, and so polarization is reduced.

The problem, as Andy Skuce notes in detail at Skeptical Science, is that the fictional article bears little resemblance to the realities of geoengineering. The technologies are described as “more effective than enactment of emissions restrictions” and would “spare consumers and businesses from the heavy economic costs associated with the regulations necessary to reduce atmospheric CO2 concentrations”.



In reality, proposed geoengineering technologies are generally very expensive, would require international cooperation and regulation, and are extremely risky. As Skuce notes, even the scientists who are among the biggest advocates for geoengineering research agree that the technologies entail high risks, and their implementation should only be considered in the event that we first fail to mitigate global warming through carbon pollution reductions and have become desperate to slow rapid climate change.

Use the Brakes, not the Airbags



If the Earth’s climate were a car, right now we’re already driving dangerously fast and accelerating. Carbon pollution cuts would be the brakes, and geoengineering would be the airbags. Kahan’s experiment tells people that we don’t need to use the brakes because the airbags will protect us, and we can have fun going fast in the meantime.



What Kahan has shown is that when presented with a fictional silver bullet solution to climate change, those with an ideological opposition to real solutions (like making polluters pay for their carbon emissions) become more willing to accept climate science realities. As with many previous studies, it confirms that much of the rejection of human-caused global warming stems from ideological opposition to the proposed solutions, rather than actual doubts about the science.

Kahan believes that telling people that scientists are studying geoengineering may still reduce polarization for some groups. He notes that different communications approaches will work for different people,

I believe professional communicators must use the data that I and others develop in lab studies and apply their own judgment about how the mechanisms involved should inform their work

In short, we have data indicating that if we tell people the experts agree we need to put on the climate brakes, more will accept that reality. And telling people that scientists are also working on an airbag system may also make more people accept the dangers that we face.

