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Why the Montreal Protocol is the most successful environmental treaty: 40 years of global impact

2025 marks the 40th anniversary of the Montreal Protocol, a landmark international agreement. Adopted in 1987 to phase out ozone-depleting substances (ODSs), the Protocol has not only protected the ozone layer but also delivered significant climate benefits, making it the most successful environmental treaty in history.

1. Universal ratification and global commitment 

 

The Montreal Protocol is the only environmental treaty ratified by every country in the world. This universal participation has enabled coordinated global action to eliminate nearly 100 ODSs, including chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which were widely used in refrigeration, air conditioning, and aerosols. 

 

2. Measurable environmental and health benefits 

 

Thanks to the Protocol: 

  • The ozone layer is on track to recover fully by mid-century. 
  • Millions of cases of skin cancer and cataracts have been prevented. 
  • Harmful ultraviolet (UV) radiation exposure has been reduced, protecting ecosystems and agriculture. 

A recent study published in Photochemical & Photobiological Sciences estimates that without the Protocol, UV Index values could have reached 40 in some regions by 2100 — compared to the current maximum of 25.8 observed in Chile [1].

 

3. Climate co-benefits 

 

Although originally designed to protect the ozone layer, the Montreal Protocol has delivered substantial climate benefits. Many ODSs, such as CFCs, are also potent greenhouse gases. Their global phase-out has helped avoid up to 0.5°C of warming, delayed the onset of an ice-free Arctic summer by 15 to 40 years, and prevented emissions equivalent to 135 gigatons of CO₂ between 1990 and 2010. These co-benefits underscore the Protocol’s dual role in environmental protection and climate mitigation [2]. 

The Kigali Amendment (2016) extended the Protocol to include HFCs, further enhancing its climate impact. 

 

4. Financial support and equity 

 

One of the defining strengths of the Montreal Protocol is its cooperative structure that bridges the gap between developed (Article 2) and developing (Article 5) countries. This collaboration was made possible through the establishment of the Multilateral Fund in 1991, which provides financial and technical assistance to Article 5 countries, enabling them to meet their phase-out commitments. The Fund has played a pivotal role in ensuring equitable participation and fostering mutual trust.  

 

As of 2024, it has disbursed over US$3.9 billion, including US$175 million to support 123 countries in that year alone. Additionally, new initiatives such as a US$100 million framework and a US$40 million revolving fund have been launched to promote energy-efficient cooling technologies, further reinforcing the Protocol’s climate and development goals [3]. 

 

5. Science-based and adaptive governance 

 

The Protocol is guided by regular scientific assessments and has evolved through amendments and adjustments. Its Implementation Committee supports compliance through transparency and cooperation [4]. 

 

6. A model for future environmental agreements 

 

The Montreal Protocol’s success is attributed to: 

  • Clear, enforceable targets 
  • Binding commitments 
  • Financial and technical support 
  • Strong scientific foundation 
  • Flexibility to adapt to new challenges 

It serves as a blueprint for future climate and environmental treaties, demonstrating that global cooperation is not only possible—but effective. 

 

As the world celebrates 40 years of the Montreal Protocol, the IIR recognises its profound impact on both ozone protection and climate action. The Protocol’s legacy continues to inspire innovation in sustainable refrigeration and cooling technologies, aligning with IIR’s mission to promote environmentally responsible practices worldwide. 

 

 

Sources: 

[1] Madronich, S., Bernhard, G.H., Neale, P.J. et al. Continuing benefits of the Montreal Protocol and protection of the stratospheric ozone layer for human health and the environment. Photochem Photobiol Sci 23, 1087–1115 (2024). https://doi.org/10.1007/s43630-024-00577-8 

[2] Madronich, S., Bernhard, G. H., Neale, P. J., Heikkilä, A., Sulbæk Andersen, M. P., Andrady, A. L., ... Neale, R. E. (2024). Continuing benefits of the Montreal Protocol and protection of the stratospheric ozone layer for human health and the environment. Photochemical & Photobiological Sciences, 23, 1087–1115. https://doi.org/10.1007/s43630-024-00577-8 

[3] United Nations Environment Programme. (2024). Report of the Executive Committee of the Multilateral Fund for the Implementation of the Montreal Protocol to the Thirty-Seventh Meeting of the Parties: Annex. Ozone Secretariat. https://ozone.unep.org/system/files/documents/MOP-37-8_annex.pdf 

[4] United Nations Environment Programme. (2024). Systemic issues: Annex II – Advance copy, Implementation Committee, 74th meeting. Ozone Secretariat. https://ozone.unep.org/system/files/documents/IMPCOM-74-6E_AnnexII_advance.pdf