In 1987, one of the most successful multilateral environmental efforts were undertaken when the Montreal Protocol was signed, with the objective to completely phase out ozone depleting cholorofluorocarbons (CFCs). On September 16, 1987, 196 states and the European Union (a total of 197 parties) got together to sign the Montreal Protocol. This was such a huge success and 99% of CFCs were removed from the products in which they were used, helping to save the ozone layer that protects the Earth from harmful UV radiation from the Sun.
Now, a new study suggests that this treaty may also have helped us avert a climate crisis; otherwise we would be in an even worse situation than we are now. The study says that without the Montreal Protocol, the Earth’s vegetation would have been exposed to a lot more ultraviolet (UV) radiation from the Sun, resulting in tissue damage and restricting plant growth. This damage would have decreased plants’ ability to absorb carbon (through photosynthesis) from the atmosphere, further increasing global temperatures. Additionally, less carbon stored in global flora would have meant less carbon being transferred into soils due to decomposing plant matter (the carbon cycle). Because the Montreal Protocol banned the use of ozone destroying CFCs, we were able to stave off climate change impacts that would otherwise have been even worse than they are today.
The team modelled scenarios using variables such as ozone layer, plant damage caused by UV radiation, climate change and the carbon cycle to “explore the benefits of avoided increases in ultraviolet radiation and changes in climate on the terrestrial biosphere and its capacity as a carbon sink”, according to the study. Without the Protocol, the ozone layer would have collapsed by 2040. By 2100 there would have been 78% less ozone in mid-latitudes in the northern hemisphere and 60% less in the tropics, exposing vegetation to extensive amounts of UV radiation. This would have resulted in:
- 325–690 billion tonnes less carbon held in plants and soils by the end of this century (2080–2099),
- this change could have resulted in an additional 115–235 parts per million (ppm) of atmospheric carbon dioxide,
- which might have led to additional warming of global-mean surface temperature by 0.50–1.0 degrees.
The avoided decreases in the ozone layer due to the Montreal Protocol helped to mitigate climate change. CFC’s are also greenhouse gases that contribute to global warming. If they had continued to be used, they would have increased temperatures by 1.7C on their own. Combine that with the warming would result with the weakened ability of plants and soils to absorb CO2 by an average of 0.8C, leads us to a whopping 2.5C of warming over pre-industrial levels.
Earth has already seen 1C warming since pre-industrial times due to 420ppm of carbon in the atmosphere. We would have already overpassed the Paris Agreement goals of keeping climate change below 2C and to make efforts to keep it at 1.5C.