In 1974 F. Sherwood Rowland and his research associate, Mario Molina, first sounded the alarm about the harmful effects of chlorofluorocarbons, or CFCs, on the earth's ozone layer. CFCs, which have been used in air conditioners, refrigerators, and aerosol sprays, release chlorine atoms into the upper atmosphere when the Sun's ultraviolet light hits them; chlorine then breaks down atmospheric ozone molecules, destroying a shield that protects the earth from damaging ultraviolet rays. In the mid-1980s a National Aeronautics and Space Administration (NASA) satellite actually confirmed the existence of a continent-sized hole in the ozone layer over Antarctica. By the early 1990s NASA and National Oceanographic and Atmospheric Administration scientists were warning that yet another ozone hole, this one over the Arctic, could imperil Canada, Russia, Europe, and, in the United States, New England. This news might have been gratifying affirmation for Rowland, a professor of chemistry at the...