Editorial NexoScience
You share a grim headline about melting ice caps or dying coral reefs. It feels like you did something. Then you close the tab, and the donation request that shows up right after barely registers. That gap between feeling moved and actually acting is exactly what a team of behavioral scientists set out to measure, at a scale nobody had attempted before.
A global team tested eleven different ways of talking about climate change on the same people. Researchers led by Madalina Vlasceanu and Kimberly Doell recruited 59,440 participants across 63 countries and randomly assigned each person to one of eleven expert-crowdsourced interventions, or to a neutral control text. Everyone was then measured on four separate outcomes: how much they believed in climate change, how much they supported climate policy, whether they were willing to share climate information on social media, and whether they would actually put in effort, real effort, toward planting trees through a paid task connected to a reforestation project. The interventions ranged from emphasizing scientific consensus to writing a letter addressed to a child living decades in the future.
Making the threat feel close to home did the most for people’s underlying beliefs. The single most effective strategy for shifting belief in climate change was reducing what researchers call psychological distance, essentially connecting the abstract idea of a warming planet to specific, local disasters the person could recognize. That intervention raised belief scores by 2.3 percentage points compared to the control group, the largest gain of any strategy tested, though still a modest one in absolute terms.
A letter to an imaginary child in 2055 outperformed everything else on policy support. Participants in this condition wrote to a future-generation family member, describing what they were doing today to leave behind a livable planet. That simple writing exercise increased support for climate policies, carbon taxes, clean energy, protected land, by 2.6 percentage points, and unlike most other interventions, it worked almost as well among people who started out skeptical as it did among committed believers.
Doom and gloom messaging turned out to be a trap. Exposing people to blunt, frightening facts about climate consequences was the single best way to get them to share information on social media, boosting sharing intent by 12.1 percentage points, by far the largest effect measured on any outcome. But that same fear based messaging, along with several other supposedly effective strategies, actually reduced how many trees people were willing to earn through the effortful task. In other words, the message that made people want to forward a scary post was not the message that made them willing to do something that actually cost them time and effort.
None of the eleven strategies reliably increased that costly, effortful behavior. Across the whole sample, not a single intervention outperformed the control condition on the tree planting task, and several made people plant fewer trees than if they had received no messaging at all. The researchers link this partly to a simple tradeoff: the interventions that took longest to read or complete left participants with less patience for the demanding task that came afterward, though they note other explanations, including a kind of resignation triggered by especially bleak messaging, remain possible.
This was a randomized experiment, not an observational study, so the differences between groups can genuinely be attributed to the messages themselves rather than to who happened to already believe what. Even so, the authors are upfront about the limits of what they found. The effects were small in absolute terms, they were concentrated among people who were not already climate skeptics, and the study measured intentions and a single symbolic behavior rather than someone’s actual carbon footprint over months or years. Global belief in climate change was already high before any intervention, at 85.7%, which likely capped how much any single message could move the needle. The authors conclude that behavioral nudges alone are unlikely to deliver the scale of change needed, and that top down policy shifts probably have to carry most of the weight.
Study: Vlasceanu M, Doell KC, Bak-Coleman JB, et al. “Addressing climate change with behavioral science: A global intervention tournament in 63 countries.” Science Advances, 2024;10(6):eadj5778. DOI: 10.1126/sciadv.adj5778.
