There is a need to approach environmental education (EE) topics, such as climate change, with a framework that productively reflects its inherent complexity. This study investigates how computational thinking (CT), specifically systems thinking (ST), may prepare educators to teach climate change. As scientists increasingly rely on computational techniques in their studies of complex EE topics, it is incumbent on science education to provide learners with computational thinking opportunities. We investigated how elementary preservice teachers (PSTs) in a science methods course (N=35) adapted a curricular resource on the climate change topic of sea level rise to integrate the CT practice of ST. Changes in their thinking were analyzed. Findings suggest that PSTs prior to instruction held a limited understanding of climate systems, often conflating weather and climate. Post instruction, their thinking expanded to consider the relationships between carbon dioxide, global warming, ice melt, and sea level rise. Further, many were able to describe these systems in a future EE teaching activity for young learners. A major implication was the need to develop a continuum of CT practices for elementary educators, with an emphasis on ST, for complex environmental education topics, that could frame their pedagogical thinking for climate change education.