By working together, and agreeing to ban certain industrial chemicals, the countries of the world averted an environmental disaster in the 1980s.
The effect of certain chemicals on the ozone layer had been report in 1975. However, in 1985 British scientists announced the discovery of a shocking decline in atmospheric ozone concentrations high above Antarctica.
The “ozone hole”, as it became known, was caused by ozone depleting chemicals called chlorofluorocarbons (CFCs). Invented in the early 1890s, and first used in the 1930s as refrigerants and propellants in spray cans, CFCs were to cause surprising damage. While CFCs are not reactive at Earth’s surface, they become quite destructive when they are exposed to ultraviolet light in the upper stratosphere. Of course, no-one knew that at the time.
Ozone naturally traps around 98% of the sun’s ultraviolet (UV) light which is damaging to humans and other life. The concerns about the risk of skin cancer, cataracts and sunburn associated with increased exposure to UV radiation galvanised public opinion. Countries around the world moved quite quickly to ban CFCs and other ozone depleting chemicals. On 16 September 1987 46 countries signed the Montreal Protocol on Substances that Deplete the Ozone Layer which banned CFCs. The Protocol was later ratified by a total of 197 countries and came into effect on January 1, 1989.
30 years after the Montreal Protocol was signed, the ozone layer is now slowly recovering. Because CFCs have lifetimes from 50 to 100 years it may take more than another 50-60 years before the ozone layer makes a full recovery. However, in January 2018, NASA reported that the ozone hole was the smallest it had been since 1988, the year before the Protocol came into effect.
Ozone and climate change
As well as being ozone depleters, CFCs are powerful greenhouse gases, with more than 5,000 times the warming potential of an equivalent weight of carbon dioxide.
If the Montreal Protocol hadn’t been signed earth would not only have significantly higher ozone depletion we would have significantly higher atmospheric temperatures and climate change.
Part of the reason was highlighted in a multi-national modelling study reported in Nature magazine. The ozone layer not only protects animals from UV radiation but also plants. UV rays cause damage to the tissues and the photosynthetic ability of plants. In protecting the globe’s flora from UV, we ensured plant species and soils will absorb 325–690 billion more tonnes of carbon dioxide by the end of the century, the modelling found. This equates to between 0.5C and 1C of warming.
Also, the ozone hole over the South Pole has a complex influence on the atmosphere, oceans and wind patterns in and around Antarctica. Strengthened winds blowing over the Southern Ocean draw more deep water towards the surface, where it degasses when it comes in contact with the atmosphere. Deep Antarctic water is rich in CO₂ already which means that it is less able to absorb atmospheric CO₂. That means that the ocean has become less efficient at removing excess carbon dioxide from the atmosphere, reducing its ability to offset global warming.
What did we learn from CFCs and Ozone depletion
The success of the Montreal Protocol holds lessons for today’s efforts to stop human-induced climate change. Perhaps the most important lesson is the need for decisive action, even when the science is not yet conclusive.
“We don’t need absolute certainty to act,” says Sean Davis, a climate scientist at the US National Oceanic and Atmospheric Administration. “When Montreal was signed, we were less certain then of the risks of CFCs than we are now of the risks of greenhouse gas emissions.”