After a decade of steady growth in the acceptance of the existence of climate change and its anthropogenic causes, opinions have polarized, with almost one-third of Americans, mostly Republicans, denying that the climate is changing or that human activity is responsible. What causes Americans to change their minds on this issue? Using a large panel data set, we examined the impacts of direct experience with weather anomalies, ideology, relative prioritization of environmental conservation in comparison to economic development, and motivated reasoning that adjusts individual opinion to align with others who share one’s party identification. A generalized ordered logit model confirmed the importance of political ideology, party identification, and relative concern about environmental conservation and economic development on attitude change. The effect of party identification strengthened with attentiveness to news and public affairs, consistent with the logic of motivated reasoning. Recent experience with hot summers, warm winters, droughts, and natural disasters had only a minimal impact on attitude change.