Repeating climate denial claims makes them seem more credible, Australian-led study finds

Repeating false and sceptical claims about climate science makes them seem more credible – including to people who accept the science and are alarmed by the climate crisis – new research has found.

The study’s lead author, Mary Jiang, from the Australian National University, said: “The findings show how powerful and insidious repetition is and how it can influence people’s assessment of truth.”

Published in the academic journal Plos One, the study said people were more likely to judge a statement as probably true if they had encountered it before, a behaviour psychologists called the “illusory truth effect”.

The paper is among the first to test the effect of statements about the climate crisis. The findings highlight the dangers of repeating and sharing misinformation.

“A single repetition is enough to nudge recipients towards acceptance of the repeated claim, even when their attitudes are aligned with climate science, and they can correctly identify the claim as being counter-attitudinal,” the paper states.

Researchers from Australian and US institutions conducted two experiments involving 52 and 120 participants, respectively. About 90% of participants across both tests were considered “climate science endorsers”.

Participants were shown a set of common climate-related statements, including a mix of science-based and sceptical claims.

An example of a science-based claim was that “climate change models can make accurate predictions”, Jiang said. A sceptical claim might challenge the accuracy of climate science or suggest a conspiracy.

Participants then rated the perceived truthfulness of a new series of statements – half new and half seen previously – on a scale from definitely true to definitely false.

Participants on average assessed science-based statements as more truthful, consistent with their largely pro-climate science attitudes. But the results also revealed repetition boosted truthfulness scores for both climate-science-sceptic and climate-science claims.

Dr Gabi Mocatta, a climate science communication researcher at the University of Tasmania, said effective communication was essential to climate action.

“Media are crucial in all of this because the science is settled … We know what the issues are and we know what needs to be done in response and we know the timeframe,” she said.

Mocatta said her own soon-to-be-published research had found that climate sceptical claims and climate misinformation tended to “travel faster, further and longer from its origin than accurate climate information”. She said climate sceptic claims tended to be more negative and emotion-arousing.

Dr Jess Berentson-Shaw, co-director of The Workshop – an organisation that helps people use evidence to communicate complex issues, including climate change – said people were frequently being exposed to false climate information about climate.

“It is framed in ways that makes it easy for people to hear and share,” she said.

“The cognitive science is pretty clear that repetition is a very powerful tool because of how we process information. The more we hear something, from multiple sources, including those we trust, the smoother it becomes to process, the more accepted it is as ‘just known’.

“Climate communications need to focus on repeating what is known and true much more than debunking, myth-busting and repeating what is not [true].”

Jiang’s research found repetition influenced the perceived truth of climate-sceptic claims even among people who were most alarmed about climate change.

The paper concluded: “Do not repeat false information. Instead, repeat what is true and enhance its familiarity.”