Graduate students entered our online classrooms with robust, but nonscientific, opinions on climate change. To expose students to critical analysis of media and emphasize the nature of science, we required them to access scientific reports and participate in mandatory peer discussions. An introductory survey probed incoming knowledge and opinions, and students in four geology sections were then randomly assigned across sections to discussion groups. Throughout the semester, the instructor assigned resources and posted critical-thinking questions to guide discussions. Students analyzed data sources, judged studies' research relevance and application, identified nonscientific views, analyzed current trends against Earth's geologic history, and conducted additional research. At semester's end, each group summarized a consensus, and students completed postsurveys. Through content analysis, four broad themes emerged in group summaries, but differences existed. Paired pre- and postsurveys revealed that the vast majority of students (91%) indicated online peer-discussion forums promoted greater scientific understanding of the climate change issue. (Contains 1 table and 5 figures.)