Mounting evidence suggests the public are not homogeneous in their climate-change opinions. Studies segmenting climate-change views typically deploy a top-down approach, whereby concepts salient in scientific literature determine the number and nature of segments. In contrast, in three studies using Australian citizens—undertaken at different stages of the Black Summer bushfires—we used a bottom-up approach, in which segments were determined from perceptions of climate change concepts derived from citizen social-media discourse. In Study 1 (before bushfires), we identified three segments of the Australian public (Acceptors, Fencesitters, Sceptics) and their psychological characteristics. Segments differed in climate change concern, political ideology, and environmental worldviews. In Study 2 (during bushfires), we examined whether reception to scientific information differed across segments using belief-updating tasks. We find significant heterogeneity in the belief-updating tendencies of the three segments that can be understood with reference to their different psychological characteristics. In Study 3 (during bushfires), we incorporated a measure of bushfire perceptions and elicited respondents climate-change policy preferences. Bushfire perceptions varied across segments, notably Acceptors were uncertain whether the bushfires were caused by arson attacks, whereas Fencesitters and Sceptics were more certain than not that the bushfires were caused by arsonists. Acceptors showed a preference for increased governmental climate action, whereas Fencesitters and Sceptics showed a preference for no governmental changes in climate action. The proportion of respondents falling into the three segments did not vary across the three studies indicating that experience of the Black Summer bushfires did not alter Australians’ climate-change opinions.