Pluralistic ignorance-a shared misperception of how others think or behave-poses a challenge to collective action on problems like climate change. Using a representative sample of Americans (N = 6119), we examine whether Americans accurately perceive national concern about climate change and support for mitigating policies. We find a form of pluralistic ignorance that we describe as a false social reality: a near universal perception of public opinion that is the opposite of true public sentiment. Specifically, 80-90% of Americans underestimate the prevalence of support for major climate change mitigation policies and climate concern. While 66-80% Americans support these policies, Americans estimate the prevalence to only be between 37-43% on average. Thus, supporters of climate policies outnumber opponents two to one, while Americans falsely perceive nearly the opposite to be true. Further, Americans in every state and every assessed demographic underestimate support across all polices tested. Preliminary evidence suggests three sources of these misperceptions: (i) consistent with a false consensus effect, respondents who support these policies less (conservatives) underestimate support by a greater degree; controlling for one's own personal politics, (ii) exposure to more conservative local norms and (iii) consuming conservative news correspond to greater misperceptions.