The discovery of the Antarctic ozone hole in 1985 is chronicled, making the analogy with the concept of the “black swan,” a metaphor for unprecedented events. The ozone layer in the stratosphere acts as a shield for life on the Earth, by blocking harmful ultraviolet radiation from the sun. Concern mounted in the 1970s that compounds known as chlorofluorocarbons, used as refrigerants and coolants, could be slowly destroying the ozone layer. Joe Farman and the British Antarctic Survey (BAS) found that ozone levels in the stratosphere had dropped dramatically during the Antarctic spring season in the 1980s, creating a “hole” in the ozone layer. US scientist Susan Solomon led an expedition to make measurements of the ozone hole and worked with colleagues to explain the cause: cold Antarctic temperatures allowed the formation of polar stratospheric clouds that catalyzed chemical reactions involving CFCs, leading to rapid ozone loss.