Improving climate change decision-makers’ comprehension of IPCC graphs: Evidence from a randomised experiment across 179 countries

The Intergovernmental Panel on Climate Change (IPCC) Assessment Reports aim to support evidence-based decision-making by providing policy-relevant information. Yet, comprehension of graphs in IPCC reports is often poor, and recommendations to improve the graph design have not yet been tested with a global sample of the IPCC’s target audience: Climate change decision-makers. Here, we present three global experimental survey studies that apply four theoretically promising principles from cognitive science to redesign IPCC graphs, with the aim of improving graph comprehension among the IPCC’s target audience. Our sample comprised a total of N = 1,052 climate change decision-makers from governance, civil society, research, and the public sector, across 179 countries. Using actual IPCC graphs, we experimentally tested the effects of graph redesign on graph comprehension and awareness of graph comprehension, providing an ecologically valid approach. Findings show that (1) the principles matching spatial and conventional features enhanced graph comprehension consistently across studies and diverse graphs, (2) the principle one main message per graph improved participant’s comprehension and awareness of their graph comprehension, although this finding was not consistent across studies, (3) while guiding viewers to make the correct inferences and matching visual information with expectations did not enhance comprehension or awareness. These findings provide an empirical basis for improving climate science communication through graphs and offer concrete recommendations for future IPCC graph design. By advancing climate change communication, this work supports more evidence-based decision-making worldwide.