Many scientists are perplexed by the fact that some people do not believe in global warming, despite overwhelming scientific evidence. Prior research suggests that part of the reason might be that people are uninformed (Tobler et al., 2012). However, it is also worth considering how people perceive their own knowledge about global warming. For the general public, believing in global warming depends on trusting experts (Almassi, 2012). Expertise is relative, and the extent to which we defer to an expert depends on our assessment of their knowledge relative to ours. The Dunning-Kruger Effect (DKE) suggests that people tend to overestimate their own knowledge (Kruger and Dunning, 1999), and there is evidence that people are bad at evaluating their knowledge about global warming in particular (Sharp and Hoj, 2010). However, there has been no research directly examining how someone’s knowledge about global warming and their confidence in that knowledge relate to their beliefs in global warming. In the present study, we investigate this by having participants take surveys that measure their global warming knowledge, general science knowledge, confidence in their knowledge, and their global warming beliefs. We found that participants were underconfident in their global warming knowledge and this knowledge is the key predictor of one’s belief in global warming. In addition, as confidence on the general science knowledge test increased, beliefs in global warming decreased, which is consistent with the DKE.