In a study involving more than 13,000 participants in the U.S., several messaging strategies were shown to move the needle - albeit slightly - in attempts to strengthen pro-environmental attitudes and behaviors regarding climate change.
None, however, was effective in spurring people to put their money where their mouth is. And, perhaps most surprisingly, messages' persuasiveness varied little between Democrats and Republicans.
The key takeaway: Widely cited messages tend to be effective but short-term messaging can only go so far in swaying people regarding the urgency of climate change.
"The way I like to think of these short-term messages is, they're not medical surgeries, they don't fix the problem permanently. I think of them more like a session of physical therapy," said Jan Voelkel, assistant professor in the Cornell Jeb E. Brooks School of Public Policy, who focuses on political and behavioral change.
"With these short messages, we learn a little bit about our own beliefs, and we may change our minds," he said. "But if afterward you just move on with your life as it was before, your attitudes and behaviors will probably go back to what they were. In order to see sustained effects, you would have to go to 'physical therapy' again and again."
Voelkel is the first and corresponding author of "A Registered Report Megastudy on the Persuasiveness of the Most-Cited Climate Messages," published Jan. 5 in Nature Climate Change. Voelkel's 24 co-authors are from five countries and 20 different institutions, including Stanford University, where he received his master's and doctorate degrees in sociology.
For 50 years, the term "global warming" has been part of the lexicon - ever since a 1975 article in the journal Science by Columbia University geochemist Wallace Broecker: "Climatic Change: Are We on the Brink of a Pronounced Global Warming?"
Many would argue that we were: According to the World Meteorological Organization, the 10 hottest years in recorded history are 2015 through 2024. And 2025 is expected to be in the top five on that list.
But in the U.S., which leads the world in carbon dioxide emissions, only 25% of the population considers global warming extremely important, and 34% of likely voters prioritize limiting CO2 emissions over expanding oil and gas drilling, Voelkel and his collaborators wrote.
For this research, the team first conducted five pilot studies trying to replicate past work on climate messaging effectiveness, and found that widely cited strategies had little or no effect on attitudes and behavioral intentions related to climate change. Part of that, Voelkel said, could be a shift in how malleable climate change attitudes are over time.
"Public discussion around climate change has changed a lot over the last 10 years," he said. "It may be that back when some of these discussions were still fresh, you may have found bigger effects from some of the messaging than now."
To gauge the malleability of current attitudes, Voelkel and the team adopted a "megastudy" approach - taking the top 10 messaging strategies from 157 climate messaging research papers and testing their efficacy against non-climate-related control messages to gauge how much the 10 climate messages could increase: belief in climate change; climate change concern; support for general climate change mitigation policies; and pro-environmental behavioral intentions.
The researchers recruited 13,544 participants in the spring of 2024, and all were surveyed regarding their climate change attitudes and pro-environmental behavioral intentions. Questions included: "Do you think that the world's temperature probably has been going up over the past 100 years, or do you think this probably has not been happening?" and "How serious a problem is climate change?"
After answering the survey questions, participants were assigned to read one of the 10 climate messages (around 1,000 to each message) while more than 3,000 were assigned the control messages. The climate messages had labels such as "system preservation" (i.e., mitigating climate change is consistent with American values), "dire but solvable" (i.e., consequences of unaddressed climate change are dire) and "scientific consensus (1 and 2)."
After reading their assigned message, participants were once again surveyed regarding their climate change attitudes and pro-environmental behavioral intentions as well as donations to pro-environmental organizations. The researchers found that six of the messages significantly increased participants' belief in climate change; overall, the messages resulted in a 1.16-percentage-point increase in participants' belief in climate change. The "scientific consensus 2" message - emphasizing the consensus that human-caused climate change is happening - was most effective in increasing participants' belief in climate change.
Increases were also seen in concern over climate change, support for mitigation policies and for political behavior intentions, although none of the messages made participants more likely to donate money.
"We always asked the attitude questions first, then asked about donations," Voelkel said, "so maybe people felt like they've already updated their attitudes, and they don't need to donate, as well."
The biggest surprise, Voelkel said, was that the messaging were similarly persuasive for both Democrats and Republicans. "Based on previous studies," he said, "you would really expect that you'd need unique messaging strategies for conservatives or Republicans, but we don't find that in our study."
Support for this work came from the Stanford Woods Institute for the Environment and the Stanford Center on Philanthropy and Civil Society.
