Climate change is an anthropogenic existential threat that provokes extreme concern among climate scientists, but not, it seems, among all member of the public. Here, there is considerably more variability in level of concern and, it appears, in everyday sustainable behavior. But how does personality affect this variability in behavior? And how are underlying personality states like dispositional optimism linked to more sustainable everyday practices? Research in clinical psychology has suggested that dispositional optimism is a very positive personality characteristic associated (...) with higher levels of hope and resilience, but applied research from other domains has reported that optimists can, on occasion, bury their heads in the sand and avoid attending to external threats, like climate change, in order to maintain mood state. So are optimists more immune to climate change messaging than non-optimists? And do they make fewer sustainable choices? A series of experimental studies, manipulating signifiers of carbon footprint (Study 1) and eco labels on products (Study 2) found that optimists made more sustainable choices than non-optimists and that both groups were influenced equally by climate change film clips in terms of sustainable choices (Study 1). Optimists also displayed a false consensus effect, overestimating the proportion of people who would behave more sustainably like themselves (Study 3). Given that global problems like climate change need concerted, cooperative effort, these optimistic beliefs about how others behave could be adaptive in the long-run. Designing climate change messages to appeal to optimists might be a critical consideration for the future. (shrink)