Just a couple years after Thomas Midgley, Jr. invented leaded gas in the 20s, he followed up that achievement by inventing chlorofluorocarbons or CFCs, which were sold by Du Pont under the brand name of Freon. The crown jewel of his work was the creation of Dichlorodifluoromethane, or CFC-12. This substance allowed for more people to experience the wonders of electric food refrigeration as well as indoor air conditioning. For over 40 years everyone assumed the Freon was perfectly safe, and in fact safer than other chemicals used in refrigeration. It wasn’t until the 1970s, years after Midgley had died, that the horrible truth was discovered: CFCs were eating away at the Earth’s ozone layer. The ozone layer is a region in the stratosphere that absorbs 97 to 99 percent of the Sun's medium-frequency ultraviolet light, which otherwise would potentially damage life. The deterioration of this protective layer threatened all life on earth with increased risk of cancer and other ecological problems. People realized the extent of the damage in 1985 when it was discovered that there was a massive hole in the Ozone layer above the Antarctic. This emergency situation led in 1987 to the creation of an international treaty called The Montreal Protocol on Substances That Deplete the Ozone Layer. Because of this agreement, which was signed by all of the members of the United Nations and has an extremely high compliance rate, climate projections indicate that the ozone layer will return to 1980 levels between 2040 and 2066. One possible apocalypse averted because of global cooperation. This is the story of one guy who just wanted to make money for himself and the companies he worked for (specifically Frigidaire, General Motors, and DuPont), and how his second big invention eventually forced the entire world to pull off a massive effort to avoid global ecological disaster. Christie, Maureen. The ozone layer: A philosophy of science perspective. Cambridge University Press, 2001. Cagin, Seth, and Philip Dray. "Between earth and sky: how CFCs changed our world and endangered the ozone layer." 1993. McGrayne, Sharon Bertsch. “Prometheans in the Lab: Chemistry and the Making of the Modern World.” Sharon Bertsch McGrayne, 2001. Wilson, Eric Dean. After cooling: On freon, global warming, and the terrible cost of comfort. Simon and Schuster, 2021. Cox, Stan. Losing our cool: Uncomfortable truths about our air-conditioned world (and finding new ways to get through the summer). The New Press, 2010. Molina, Mario J., and F. Sherwood Rowland. "Stratospheric sink for chlorofluoromethanes: chlorine atom-catalysed destruction of ozone." Nature 249, no. 5460 (1974): 810-812. Oreskes, Naomi, and Erik M. Conway. Merchants of doubt: How a handful of scientists obscured the truth on issues from tobacco smoke to global warming. Bloomsbury Publishing USA, 2011.