Predicting the effects of climate change, just like any other events in the future, is inherently uncertain. Climate denialists often try to exploit that uncertainty to make it sound like there’s less scientific evidence or agreement about climate change than there really is. And the language climate scientists and communicators themselves use to convey scientific uncertainty may be helping to sow doubt and fuel climate skepticism, according to a new study.

“It is challenging to communicate ‘neutrally,’ especially when discussing predictions about future events,” says study team member Marie Juanchich, a psychologist at the University of Essex in the UK. “Information is inevitably framed either positively (highlighting the possibility of something happening) or negatively (emphasizing the chance that it might not).”

The Intergovernmental Panel on Climate Change (IPCC) prescribes standardized terms for communicating about the probability of different events. At the low end of the scale, the organization mandates negative terms. For example, something with a less than 33% chance of occurring should be described as “unlikely.”

In the new study, Juanchich and her collaborators conducted eight online experiments involving a total of 4,150 people, asking them to evaluate statements about climate change that used either negative (saying something is “unlikely” to occur) or positive (saying that something “has a small probability or possibility” of occurring) framing.

Many studies of uncertainty communication focus on the numerical probabilities that people attach to different terms. In the new study, both the negative and positive constructions gave people the impression that the event in question had a roughly 10 to 30% chance of happening, the researchers found. But the meaning they attached to those probabilities was totally different.

When projected outcomes are described as “unlikely” or using similar negative terms, people think the projection is backed by less scientific evidence than when those same outcomes are framed in positive terms. They also think there’s less scientific consensus around negatively framed projections than equivalent positively framed ones.

These patterns hold even after controlling for participants’ beliefs about climate change, familiarity with the IPCC (surprisingly, Juanchich says, three-quarters of those who were asked had never heard of the organization), and overall political orientation.

Positive framing also tends to focus people’s attention on the possibility that an event may happen, while negative framing focuses attention on the possibility that it may not, the researchers found. That’s a big issue when it comes to low-probability but high-stakes consequences of climate change.

“Using positive language may help prevent errors of omission (i.e., failing to act when action is needed), whereas negative framing might reduce errors of commission (i.e., acting unnecessarily),” Juanchich says. “In most climate change scenarios, the costs of inaction are likely greater than the risks of taking preventive action.”

One strategy to avoid the negative effects of negative framing without falling foul of the IPCC’s prescriptions is to instead describe a complementary, high-likelihood event in positive terms. In fact, the IPCC itself often does this. But this can still fail to raise awareness about the low-probability (but potentially important) outcome, the researchers point out.

Source: Juanchich M. et al. “Negative verbal probabilities undermine communication of climate science.” Nature Climate Change 2025.

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