The interpretation of IPCC probabilistic statements around the world

The Intergovernmental Panel on Climate Change (IPCC) uses verbal descriptions of uncertainty (for example, Unlikely) to convey imprecision in its forecasts and conclusions. Previous studies showed that the American public misinterprets these probabilistic statements. We report results from a multi-national study involving 25 samples in 24 countries and 17 languages. As predicted, laypeople interpret IPCC statements as conveying probabilities closer to 50% than intended by the IPCC authors. We show that an alternative presentation format supplementing the verbal terms with numerical ranges increases the correspondence between the publicâ (tm) s interpretations and the IPCC guidelines, and the terms are better differentiated. These qualitative patterns are remarkably stable across all samples and languages. In fact, interpretations of the terms in various languages are more similar under the new presentation format. These results suggest changing the way the IPCC communicates uncertainty.