The importance of climate-related education has been recognised, but little is known about what motivates students to learn about climate change. This study examines situational motivation in the context of a climate education module in an upper secondary school that emphasises project-based learning. We investigate variation in student motivation across activities, and the extent to which this is predicted by their attitudes to climate change and aspirations to pursue a career in science. We further assess the impact of these attitudes on their knowledge about climate change. Applying momentary assessment, we collected data on 2228 situations reported by 204 students (aged 16 years). The results show that science career aspirations affect motivation and climate change knowledge. Additionally, climate change attitudes influence motivation. Our findings highlight gender differences in attitudes towards and knowledge about climate change. They further imply that a project-based learning approach would be beneficial in the development of climate education modules.