Climate Claims Across Platforms: Comparing Meta Advertising and Bluesky Public Discourse

Abstract

Climate communication reaches online audiences through distinct communication environments, including sponsored advertising and public user-generated discussion. Yet most cross-platform analyses focus on themes or stance rather than the specific claims communicators advance. We analyze 16,157 climate-related Meta advertisements and 18,781 Bluesky posts to examine how climate claims differ across these two online environments. Using a Toulmin-inspired constrained large language model (LLM) pipeline, we extract and validate explicit claims and compare them through topic, named-entity, and LIWC-based linguistic analyses. We find that Meta advertisements more often emphasize solution-oriented, locally targeted, and campaign-style claims, whereas Bluesky posts are more political, event-driven, and issue-centered. Meta claims also more frequently foreground clean energy, U.S. geographic contexts, and institutional actors, while Bluesky claims more often center on broad climate issues, fossil-fuel responsibility, and political actors. Linguistically, Meta claims exhibit more analytic and authoritative language, whereas Bluesky claims are more personal and expressive. These findings characterize observed differences between two structurally distinct climate communication environments and demonstrate how claim-level analysis complements conventional topic- and stance-based approaches by revealing not only what online discourse discusses, but also the claims communicators advance.