Climate change is one of the most critical problems facing citizens today. Chemistry faculty are presented with the problem of making general chemistry content simultaneously relevant and interesting. Using climate science to teach chemistry allows faculty to help students learn chemistry content in a rich context. Concepts related to electromagnetic radiation and gases can be taught using an understanding of climate change and how greenhouse gases work. However, it would be important to know the level of prior knowledge that the students bring to the course and their confidence in that knowledge. Thus, a two-tiered instrument was developed to measure student understanding of climate change, the behavior of gases, and the mechanism of radiative forcing by greenhouse gases. The instrument was implemented iteratively at two institutions to allow for revision and replication. The final form of the instrument may be used in general chemistry classes or interdisciplinary courses to shape and guide instruction.