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Scientists find ozone depletion began decades before discovery of ozone hole
Scientists find ozone depletion began decades before discovery of ozone hole
Using modern tools, they also determined that carbon tetrachloride, used as a dry-cleaning and degreasing agent as early as the 1930s, was at the root of early ozone loss.
Jennifer Chu<br>MIT News
Publication Date:
June 29, 2026
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“The fact that ozone depletion would have happened as early as the late 1950s, which is much earlier than I would have thought, just absolutely blew my mind,” says Susan Solomon.
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Image: Jose-Luis Olivares, MIT
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Caption:
“The fact that ozone depletion would have happened as early as the late 1950s, which is much earlier than I would have thought, just absolutely blew my mind,” says Susan Solomon.
Credits:
Image: Jose-Luis Olivares, MIT
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The Antarctic ozone hole was discovered in 1985, when scientists observed a severe depletion in the Earth’s protective layer of stratospheric ozone. Industrial chemicals known as chlorofluorocarbons (CFCs), then widely used as refrigerants, propellants, foam-blowing agents, and solvents, were at the root of the ozone depletion. After concerted global effort to phase out the use of CFCs, ozone today is recovering, especially in the Antarctic.<br>The discovery of the ozone hole was possible thanks, in part, to the measurement tools that were available at the time. Advances in those tools, along with satellites and other monitoring technologies, have since allowed scientists to track ozone’s recovery.<br>But what if today’s tech was available much earlier? Would scientists have been able to spot even earlier signs of human-induced ozone depletion? And if so, when would those first signs have popped up, and where?<br>MIT scientists now have some answers. The team, led by atmospheric chemist Susan Solomon, has carried out a thought experiment in which they consider a hypothetical world where today’s atmospheric monitoring capabilities were available throughout the last century. In this scenario, they simulated the atmosphere’s chemistry through history and discovered not only when the earliest sign of ozone depletion would have been detectable, but also where, and why.<br>In a study appearing today in the Proceedings of the National Academy of Sciences, the scientists suggest that the first signs of ozone depletion appeared as early as 1957 — about 30 years before the ozone hole was discovered. And, this first signal of ozone loss popped up not in the Antarctic, but in the upper stratosphere of the tropics. What’s more, the cause of this early depletion was not due to CFCs, but to another industrial chemical: carbon tetrachloride.<br>“What we’ve learned from textbooks is that CFCs result in ozone depletion,” says the study’s first author, Jian Guan, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “It turns out there was another compound that caused ozone depletion much earlier than CFCs. This was a big surprise.”<br>For Solomon, who was an early pioneer in the study of ozone’s effects on the atmosphere, and who was the first to show that CFCs were the main agent eroding Antarctic ozone, the new results were a complete shock.<br>“The fact that ozone depletion would have happened as early as the...