Does a thinking person today have a chance of figuring out what to think about climate change? On the one hand, we are told there is a scientific consensus that humans are changing the climate. On the other hand, the most pessimistic future scenarios strain our credulity. The most extreme example may be the retired professor who believes that we will all be dead by 2026. The activist group Extinction Rebellion is telling us that climate change represents “an unprecedented global emergency” and is calling for radical measures to deal with it. Such claims seem to be gaining ground and appearing with increasing frequency in the media. And according to a recent poll, nearly half of Americans believe climate change will result in the end of the world within the next 200 years. Even among the more optimistic, many find it prudent to consider the worst case, but have very little information to help them decide where to draw the line between farsightedness and fantasy. And I understand those who assume that even though some …