The cases of COVID-19 and climate change highlight the central role of scientific research which supposedly guides political decision-making. Models and scenarios assume a central role. However, science cannot tell us what to do. While it provides important facts and metrics, uncertainties remain and decisions are based on considerations pertaining to fundamental values. Apart from these similarities, my aim is to emphasize some significant differences.They relate to policy goals, international cooperation, data and metrics, values, and the time horizons involved.