This study investigated 438 Year 10 students (15 and 16 years old) from Western Australian schools, on their understanding of the greenhouse effect and climate change, and the sources of their information. Results showed that most students have an understanding of how the greenhouse effect works, however, many students merge the processes of the greenhouse effect with the ozone layer. Students gained climate change information from school science and geography, as well as different forms of media. Recommendations include teacher professional development and informing teachers of common alternative conceptions amongst students.