Students' everyday ideas of the greenhouse effect are difficult to change. Environmental education faces the challenge of developing instructional settings that foster students' conceptual understanding concept of the greenhouse effect in order to understand global warming. To facilitate students' conceptual development with regard to the greenhouse effect, learning materials aimed at promoting active cognitive learning in order to achieve deep understanding were designed. The learning materials were developed on the basis of the theory of reasoning and understanding co-founded by the Swiss educational psychologist Aebli. In a repeated measure design using a pre-, post- and follow-up test, the efficacy of these learning materials compared with standard learning materials was tested. A total of 289 eighth graders who had received little prior science instruction participated in the study. A combination of quantitative and qualitative methods was used to examine the students' knowledge acquisition and understanding over three measurement times. The group that had been instructed according to the method aimed at in-depth learning outperformed the group taught with standard materials on subsequent tests in terms of knowledge gains, structure and retention. The findings suggest that the theory-based learning materials promote active cognitive processing during learning. The instructional design of the learning materials seems to engage the learners in high cognitive activities that facilitate deep conceptual understanding of the complex and abstract concept of the greenhouse effect. (Contains 3 notes, 3 figures and 6 tables.)