While scenarios are used extensively for communication about climate change mitigation, little is known about the interpretation of these scenarios by citizens. We conducted a cross-country empirical evaluation of scenario visualizations for global mitigation, using online surveys in Germany (N = 379), Poland (N = 223), and France (N = 225). Each respondent received visualizations of the required changes in global carbon dioxide emissions and composition of electricity supply (fossil fuels, nuclear, and renewable sources) for limiting global warming to 1.5 °C. We evaluated the effects of respondents' demographics, prior beliefs, numeracy, and graph literacy on the reading accuracy and knowledge gains from the visualizations. We also included an experimental between-groups design on visualization format, where four groups received different graph formats (steep or gradual graphs with depictions of uncertainty ranges or scenario ensembles) and the fifth group received a table. Results showed that higher education level, numeracy, and graph literacy increased reading accuracy in all countries, while age reduced them. Respondents with prior beliefs about climate change mitigation that matched the information in the visualizations had also higher reading accuracy and knowledge gains. While the effects of different visualization formats were comparatively minor, customizing formats according to demographic and country differences was used to reduce adverse effects from these differences. These results emphasize the need to design visualizations that match characteristics of the intended audience and could inform better communication of climate change mitigation scenarios to non-expert audience.