MIT study finds ozone loss began in 1957, not 1985

The first signs of human-caused ozone depletion appeared as early as 1957 — roughly 30 years before the Antarctic ozone hole was discovered — and the culprit was not chlorofluorocarbons but an older industrial solvent called carbon tetrachloride, according to new research from MIT published June 28 in the Proceedings of the National Academy of Sciences.phys+1

A Thought Experiment Rewriting Ozone History

Led by atmospheric chemist Susan Solomon, the team posed a deceptively simple question: if today's monitoring tools had existed throughout the 20th century, when would scientists first have detected human-induced ozone loss? Using 16 model simulations of atmospheric chemistry over the past 76 years, the researchers identified a clear signal emerging not over Antarctica but in the upper stratosphere of the tropics, where natural variability is lowest and a human fingerprint would be easiest to spot.gizmodo+1

"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," Solomon said.phys

The study's first author, MIT graduate student Jian Guan, noted that the finding overturns textbook assumptions. "It turns out there was another compound that caused ozone depletion much earlier than CFCs. This was a big surprise," Guan said.phys

Carbon Tetrachloride: The Overlooked Culprit

Carbon tetrachloride was widely used as a dry-cleaning and degreasing agent beginning in the 1930s — years before CFCs entered mass production for refrigeration and aerosol propellants. Ice core records confirm the chemical was accumulating in the atmosphere by the 1940s. By 1957, concentrations were high enough to produce a detectable ozone signal, the models show.phys

"That's the only ozone-depleting substance that was increasing that early," Solomon said.gizmodo+1

The compound was eventually phased out under the Montreal Protocol due to both its ozone-depleting potential and its health risks, including nervous system damage and suspected carcinogenicity. Yet a 2014 NASA study found that global emissions of carbon tetrachloride persisted at roughly 30 percent of pre-treaty peak levels from unknown sources.svs.gsfc.nasa

Implications for Monitoring

The findings underscore the importance of continued atmospheric surveillance even as the ozone layer recovers. Separate MIT-led research published earlier this year confirmed that Antarctic ozone is healing thanks to global CFC reductions, while another study warned that leaking industrial feedstocks could delay full recovery by seven years.news.mit+1

"We've gone through a big effort to get rid of these chemicals," Solomon said. "Don't we have an obligation to keep monitoring to make sure the atmosphere responds the way we think it should?"phys