A study from MIT published in Proceedings of the National Academy of Sciences revealed that the first signs of ozone layer depletion appeared in 1957, nearly three decades before the discovery of the hole in Antarctica in 1985.
Researchers identified ozone loss in the upper stratosphere of the tropics and initially pointed to carbon tetrachloride, an industrial compound used since the 1930s, before the massive expansion of chlorofluorocarbons (CFCs).
Context of the Discovery
- 1985: the ozone hole was detected in Antarctica, attributed to CFCs used as refrigerants, propellants, and solvents.
- Montreal Protocol (1987): allowed for the gradual elimination of CFCs and carbon tetrachloride, achieving a progressive recovery of the ozone layer.
- New study: shows that the deterioration began much earlier and in another region of the planet.
Study Methodology
The team led by atmospheric chemist Susan Solomon and researcher Jian Guan used:
- 16 independent simulations of the atmosphere during the 20th century.
- Historical records of industrial production.
- Ice cores from Antarctica and the Arctic, which preserve chemical residues trapped in snow for centuries.
- Models that incorporated natural phenomena such as volcanic eruptions and the El Niño phenomenon.
The results showed that carbon tetrachloride concentrations began to increase in the 1940s, and the clear signal of ozone loss appeared in 1957, especially in the tropics.
Implications of the Finding
- Change in scientific narrative: textbooks attribute the start of depletion to CFCs, but the study shows that another industrial compound was already causing the effect decades earlier.
- Importance of monitoring: the research underscores the need to maintain constant atmospheric surveillance to understand how it responds and recovers.
- Persistence of compounds: both carbon tetrachloride and CFCs can remain in the atmosphere for decades, requiring strict controls.
Risks of Carbon Tetrachloride
- Used in dry cleaning and as a degreasing solvent.
- Potentially carcinogenic and harmful to the nervous system.
- Phased out in the 1990s thanks to the Montreal Protocol.
The MIT study demonstrates that ozone layer depletion began much earlier than previously thought and in regions other than Antarctica.
This finding reinforces the importance of international agreements and atmospheric monitoring to protect human health and biodiversity from the effects of industrial compounds.
