By Jeremy Deaton
People play dirty when they can't win by playing fair. This is, more or less, the story of climate change denial in the U.S.
Scientists overwhelmingly agree that humans are altering the climate, reaping changes with potentially catastrophic consequences. Climate deniers can't dispute the data. They can't win on facts. Instead, they impugn the credibility of scientists, a tactic which has proved both ugly and effective.