An empirical study on 12th-grade students' engagement on a global warming debate as a citizens' conference is reported. Within the design-based research methodology, an interdisciplinary teaching sequence integrating an initiation to non-violent communication was developed. Students' debates were analyzed according to three dimensions: communication, argumentation, and knowledge. Students regulated their oral contributions to the debate by identifying judgments in their discussions. Rhetorical processes developed by students were mainly related to the identity of debate protagonists with interest attributions, authority, and positions. Students' arguments also relied on empirical data. The students' knowledge focused on energy choices, economic, political, and science development issues. Implications for socioscientific issues integration in class are discussed.