Henrik Leon Heubl
Bachelor project
Supervised by Fuad Mehraliyev
December 18, 2025

Abstract
This study measures online climate change polarization on Reddit following a framework of positional, interactional, and affective polarization. Using 3,764,484 comment-to-parent reply dyads from 2012 onward, position was classified according to Global Warming’s Six Americas and expressed affect was classified using the Political Sectarianism framework, with final labels produced by Llama 3.3 70B. Results show that Reddit climate discourse is considerably more concerned about climate change than the U.S. population, with a dominant
alarmed mainstream and a smaller skeptical minority. Interaction patterns are largely consistent with random mixing given group sizes, producing structurally asymmetric exposure where skeptical minorities face routine cross-cutting contact. The clearest polarization signal is affective: negative affect increases in prolonged back-and-forth and is highest in far-apart disagreements. Users skeptical of anthropogenic climate change exhibit consistently higher expressed affect than believers, regardless of whether they interact with same-position or
cross-cutting contacts. Over multi-year spans, most long-observed users remain in the same position category, suggesting that aggregate positional shifts reflect changes in who participates in climate discussion over time rather than widespread within-person conversion. These patterns describe online polarization as observable in discourse, but do not establish polarization in the sense of individual attitude change.