Problem-based learning (PBL) is a teaching technique that uses problem-solving as the basis for student learning. The technique is student-centred with teachers taking the role of a facilitator. Its general aims are to construct a knowledge base, develop problem-solving skills, teach effective collaboration and provide the skills necessary to be a successful lifelong learner. This study evaluates the application of PBL in an undergraduate Earth Systems Interactions unit and an exercise based around the Urban Heat Island. The initial execution of PBL was mixed with many students fully engaged in the material, but others found the approach insufficiently structured. Some students were not able to adapt to the unusual challenges of PBL, partly because it was their first exposure. When asked about what they had learnt from their PBL experience, the students emphasized the technical rather than the problem-solving skills. In subsequent years, a more directed project-based learning approach was introduced, which improved students' overall satisfaction and performances. (Contains 5 tables and 1 figure.)