The two most prominent scientific institutions in the United States are the National Academy of Science—whose 4,000 members are made up of the most important of this country's scientists, including all the nation's Nobel laureates and Fields Medal recipients—and the 170-year-old scientific journal, Scientific American. Both those most prestigious and venerable institutions endorse the proposition that global warming and climate change are real, that they are caused by human activities, and are the No. 1 threat to life on the surface of the earth. Those are, to use Al Fonzi's own words, cold, hard facts—facts that are conspicuously missing in Mr Fonzi's anti-factual, anti-rational screed ("What makes a skeptic?" July 20). Years ago, when miners descended into the earth they would take with them canaries, which they used to test whether the air they breathed in the shafts would kill them. Polar bears are analogous to those canaries; if they die off through habitat loss, you can bet we will not be long behind. But unlike those miners of old we can't save ourselves by fleeing the mine; we either change our ways or die. Anyone supporting any other position is delusional.