Attitudes on which people have achieved cognitive closure are better predictors of future attitudes and behavior than open attitudes. In two experiments, we found that factors in communication (source identity, source consensus) can enhance people's ability to achieve cognitive closure on complex environmental topics through an increase in perceived source expertise. Results showed that participants perceived higher levels of source expertise and felt better able to achieve cognitive closure on the environmental technology of carbon dioxide capture and storage (CCS) when the information source had an expert identity compared to a non‐expert identity. The communication of consensus by the information source increased the level of expertise ascribed to the non‐expert source, resulting in an enhanced ability to achieve closure.