<p>Social media have become central to climate change communication, shaping how information circulates, how publics engage and who participates. We synthesize research about the prevalence and dominant forms of climate-related content on social media, as well as the documented effects of social media on attitudes, knowledge and behaviour, which exist but are context dependent and vary with platform affordances, governance regimes and sociopolitical conditions. We also examine how social media reshape the broader landscape of climate change communication by enabling outreach and diverse voices, while fostering fragmentation, ideological bias and misinformation, as well as marginalizing traditional media. Finally, we identify key gaps, including restricted data access, limited cross-regional research, and the underrepresentation of non-Western contexts and region-specific platforms, and call for an expanded, reflexive research agenda in future work.</p>