As part of a renewed focus on current environmental concerns, the new geography programs set out for middle schools introduced new subjects on global change in 2015, subsequently replaced by a focus on climate change in 2020. The case study approach to teaching, imposed by official directives, makes it difficult for middle school students to understand these complex notions. This research attempts to analyze how students appropriate these notions and to verify whether they are capable of reasoning in a systemic way, i.e. of adopting the required approach for understanding such complexity. This article explores an epistemological analysis of global change and climate change, a didactic study of school textbooks and an examination of teachers' discourse and students' work in order to address this question.