I personally know someone with the belief that climate change is a political conspiracy. Any evidence to support climate change just points to a bigger "cover-up" and validates their beliefs. Almost always this is not an isolated belief but a pattern of thinking, and the person holds similar conspiracy theory beliefs about other issues. This is not a political left/right issue (the person I happen to know happens to be a left-wing conspiracy theorist). This is an issue of mild paranoid psychosis that is not being recognized and treated seriously because the symptoms are not very disturbing to others, and the people suffering from it happen to be relatively high-functioning. Eventually as these people age the symptoms get worse and they end up driving those close to them away.