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1987 ozone treaty had an unexpected benefit for the environment

New research has shed light on an unforeseen benefit of the 1987 global agreement, known as the Montreal Protocol, which aimed to protect the ozone layer. The study reveals that this international accord may have delayed the inaugural ice-free Arctic summer by up to 15 years, with the timeline now projected for mid-century.

The Montreal Protocol was a landmark agreement, ratified by every member of the United Nations. It focused on regulating nearly 100 synthetic chemicals, identified as ozone-depleting substances (ODSs). These chemicals were largely developed during the 20th century for industrial applications such as refrigerants and propellants, the most well-known being chlorofluorocarbons, or CFCs.

Despite the primary objective being the conservation of the ozone layer – a shield protecting us from the sun’s harmful ultraviolet radiation – the Montreal Protocol had a broader impact. The ODSs in focus also double as potent greenhouse gases, which means that the agreement inadvertently played a role in mitigating global warming.

The recently conducted study, backed by the US National Science Foundation, unveiled some astonishing insights about this unforeseen impact. The research team – comprising scientists from UC Santa Cruz, Columbia University, and the University of Exeter – found that for every 1,000 tons of ODS emissions prevented, approximately seven square kilometers of Arctic sea ice were saved.

How ODSs impact the environment

Dr. Mark England, a senior research fellow at the University of Exeter under the Royal Commission for the Exhibition of 1851, clarified the influence of ODSs on our environment. 

“While ODSs aren’t as abundant as other greenhouse gases such as carbon dioxide, they can have a real impact on global warming,” said Dr. England. “ODSs have particularly powerful effects in the Arctic, and they played a major role in driving Arctic climate change in the second half of the 20th Century.”

Dr. England also noted that while curbing these impacts was not the primary aim of the Montreal Protocol, it turned out to be a “fantastic by-product.” He said that despite some critics forecasting negative outcomes from the Protocol, these mostly did not materialize. Instead, the treaty has delivered numerous unexpected climate benefits.

First ice-free Arctic summer will be a pivotal moment

Taking a similar stance, Professor Lorenzo Polvani from Columbia University emphasized the significance of the first ice-free Arctic summer – a pivotal moment in the narrative of climate change. 

“Our findings clearly demonstrate that the Montreal Protocol has been a very powerful climate protection treaty, and has done much more than healing the ozone hole over the South Pole,” said Professor Polvani. “Its effects are being felt all over the world, especially in the Arctic.”

The research utilized cutting-edge climate model simulations to draw these conclusions. It emphasized that the protection of the ozone layer did not contribute to the preservation of the Arctic sea ice. Instead, the primary factor was the greenhouse gas role played by the ODSs.

Post the Montreal Protocol, the atmospheric concentrations of ODSs have been on the decline since the mid-1990s. This successful effort has led to the first signs of the ozone layer’s healing process. Nonetheless, a small rise in ODS concentrations was recorded between 2010 and 2020, prompting Dr. England to emphasize that vigilance remains crucial.

The study’s findings, highlighting the unexpected climate benefits of the Montreal Protocol, are published in the prestigious journal Proceedings of the National Academy of Sciences.

More about the ozone layer

The ozone layer is a region of the Earth’s stratosphere that contains a high concentration of ozone (O3) molecules. It plays a vital role in protecting life on Earth by absorbing the majority of the Sun’s harmful ultraviolet-B (UV-B) radiation. 

Without this protective shield, humans and other organisms could be subjected to harmful levels of UV radiation, potentially causing skin cancer, cataracts, weakened immune systems, and damaging crops and marine ecosystems.

Depletion of the ozone layer 

However, in the mid-20th century, scientists discovered that the ozone layer was depleting, primarily over the Antarctic, creating what is commonly known as the “ozone hole.” The primary culprits were man-made chemicals, particularly chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform. 

These chemicals were widely used in air conditioners, refrigerators, aerosol propellants, fire extinguishers, and in various industrial processes. Once released into the atmosphere, they could stay there for a long time, slowly rising to the stratosphere where they could be broken down by solar radiation, releasing chlorine and bromine atoms, which could then catalyze the destruction of ozone.

The 1987 Montreal Protocol

Concern over this growing environmental issue led to the establishment of the 1987 Montreal Protocol. This international treaty was designed to protect the ozone layer by phasing out the production and consumption of these ozone-depleting substances (ODSs). 

The Montreal Protocol was remarkable in the broad global consensus it achieved; it is the first treaty in the history of the United Nations to achieve universal ratification, with all 198 UN member countries signing on.

Since its implementation, the Montreal Protocol has been incredibly successful. It has resulted in the phase-out of 99% of ODSs globally. According to a 2018 scientific assessment by the UN, the ozone layer is recovering and the Antarctic ozone hole is expected to gradually close, returning to 1980 levels in the 2060s. 

This assessment also indicates that the Protocol will have prevented 2 million cases of skin cancer annually by 2030, averted damage to human eyes and immune systems, and protected wildlife and agriculture.

Inadvertent positive consequences

Furthermore, because many ODSs are also potent greenhouse gases, the Montreal Protocol has inadvertently mitigated some climate change. Recent studies have suggested that the Montreal Protocol’s controls on ODSs have avoided a significant amount of global warming, potentially more than any other measure taken so far.

However, despite these successes, challenges remain. Some ODSs continue to be emitted, either from existing equipment and products or from certain exempted uses. Furthermore, some substances that replace ODSs, while not depleting the ozone layer, are potent greenhouse gases. 

In response, the Montreal Protocol was amended in 2016 (the Kigali Amendment) to include hydrofluorocarbons (HFCs), which are used as replacements for CFCs but contribute to global warming.

In conclusion, the 1987 Montreal Protocol stands as a successful example of global cooperation in response to a planetary environmental threat. The continued vigilance and cooperation of the international community will be critical in ensuring the full recovery of the ozone layer and the successful management of ODSs and their substitutes.


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