In 1987, all 197 member states of the United Nations came together to adopt the Montreal Protocol on Substances that Deplete the Ozone Layer. This environmental agreement regulated the production and consumption of human-produced chemicals, such as chlorofluorocarbons (CFCs) — found in products such as aerosols — that deplete the ozone layer. Now, more than 30 years later, we continue to recognize the positive impacts of this landmark protocol to protect the shield that absorbs most of the Sun's ultraviolet radiation.
The harmful chemicals that the Montreal Protocol govern are known to have triggered changes in atmospheric air temperature and wind in the Southern Hemisphere. ECCC’s Senior Research Scientist, Dr. John Fyfe, and U.S. colleagues examined these changes over recent decades. According to their study, published earlier this year in Nature, around the year 2000, the ozone depletion driven changes in temperature and wind stopped. The study concludes that the Montreal Protocol was the main driver of this encouraging turn of affairs.
Recovery of the Ozone Hole
The ozone hole was discovered in 1985 and forms every spring over Antarctica. Throughout the 1980s to 1990s, the ozone hole grew in size causing the southern mid-latitude jet stream to blow stronger and shift towards the South Pole. “The cause of the poleward shift from the late 1970s to 2000s was primarily due to the combined effects of greenhouse gas increase and stratospheric ozone decrease”, says Fyfe.
Beginning around the year 2000, the concentration of ozone-destroying substances in the stratosphere began to decline and the ozone hole started to recover. Dr. Fyfe and his colleagues at the University of Colorado, Columbia University, and Johns Hopkins University showed that starting around this time the jet stream stopped its southward migration.
Ozone Depletion versus Greenhouse Gas Emissions
Using computer simulations, the researchers concluded that the shift in atmospheric winds from about 1979 to 2000 cannot be explained by natural effects alone. Rather, the shift was primarily due to the combination of rising concentrations of carbon dioxide and ozone depleting substances. After 2000, as the ozone depleting substances began to decrease, the poleward shift of the winds stopped, if not slightly reversed.
While the ozone layer is recovering, carbon dioxide levels are continuing to rise and as a result, the future is less certain. However, the Montreal Protocol illustrates that international multi-lateral agreements can have significant positive impacts on our environment. When world leaders signed in 1987, the goal was to prevent the destruction of our ozone layer and the Montreal Protocol has been a success in the ongoing protection of our global climate system.