Why do some controversies persist despite the evidence?

The debate over climate change is relatively young while nuclear power and pesticides have been heated topics since the 1960s, and fluoridation since the 1950s. So what is it about these scientific controversies that makes them seem to go on forever? Some campaigners despair, assuming that those on the other side simply refuse to acknowledge the overwhelming evidence: “They must be ignorant. Or devious – they’re lying. Or they’re getting paid.” Ignorance or psychological resistance might be relevant in some cases, but there are better explanations for why controversies persist. Sociologists have been studying scientific and technological controversies for many decades, and have documented that new evidence seldom makes much of a difference. So what is going on? Anyone who wants to better understand controversy dynamics needs to consider several factors as I’ve outlined in a new Controversy Manual.