- The Montreal Protocol on Substances that Deplete the Ozone Layer was adopted in 1987 under the leadership of the United Nations Environment Programme (UNEP).
- It is a legally binding international treaty regulating the production, trade, and consumption of chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODSs).
- It is the first environmental treaty to achieve universal ratification by 197 nations.
- The treaty enabled global cooperation in phasing out chemicals that damage the ozone layer.
Analogy
The Montreal Protocol acted like a global medical treatment plan - diagnose the problem, set an intervention schedule, monitor progress, and update the prescription when new information became available.
Why the Montreal Protocol Has Been Successful
1. Strong scientific basis and early action
- The agreement was signed before scientific certainty was complete, demonstrating precautionary global action.
- Science was continuously reviewed, and policy evolved alongside new evidence.
Example
When new evidence showed that HCFCs were also harmful, the Copenhagen Amendment (1992) accelerated their phase-out.
2. Legally binding and enforceable agreement
- The Protocol contains clear phase-out deadlines and compliance requirements, unlike many voluntary climate agreements.
- Violations of the treaty result in trade restrictions and loss of access to regulated chemicals.
3. Support mechanisms for LICs and fairness
- A Multilateral Fund (1990) provides financial and technical assistance to low-income countries.
- This ensures that countries can adopt alternatives without sacrificing economic development.
- Industry had time to adapt research and manufacturing, preventing economic collapse.
Example
- Before the Montreal Protocol, refrigerators and air conditioners relied heavily on CFCs.
- After the treaty, manufacturers shifted to CFC-free technology, supported by financial and technical assistance for low-income countries.
Role of UNEP in Driving Action
- UNEP played a central role in scientific communication, negotiation, and international coordination.
- UNEP raised global awareness about:
- rapid ozone loss,
- its anthropogenic causes, and
- its threats to human health and ecosystems.
- UNEP coordinated international scientific panels to ensure evidence-based decision-making.
- UNEP facilitated global cooperation between governments, industries, scientists, and enforcement agencies to prevent illegal ODS trade.
Note
UNEP coordinated research networks that confirmed the Antarctic ozone hole, motivating urgent political action.
Why the Montreal Protocol is Considered a Model for Future Environmental Cooperation
- Universal participation, including high-income and low-income nations.
- Science-driven policy decisions rather than political debate.
- Economic support mechanisms such as the Multilateral Fund to support developing nations.
- Ability to evolve with new science, demonstrated through amendments.
- Shared recognition that all nations benefit, regardless of who invests most.
Theory of Knowledge
Should countries that contributed most to ozone depletion be responsible for a larger share of restoration costs?
Connection to the Planetary Boundaries Model
- Stratospheric ozone depletion is one of the nine planetary boundaries representing environmental thresholds that must not be crossed to maintain Earth system stability.
- Had the Montreal Protocol not been adopted, the ozone depletion boundary would have been crossed, leading to irreversible biological and climatic consequences.
- Actions under the Montreal Protocol successfully kept ozone loss within the safe operating range.
Evidence that the Montreal Protocol prevented boundary breach
- After the Montreal Protocol entered into force, the production of ODSs fell by over 99 percent in industrialised countries and by more than 50 percent in developing countries by 2002.
- The size of the Antarctic ozone hole has stabilised and is slowly decreasing, although annual variation still occurs due to temperature and wind patterns.
- The World Meteorological Organization (WMO) and NASA report that the ozone layer is on track to return to 1980 values by ~2050 in mid-latitudes and ~2065 in polar regions.
Example
Without the Montreal Protocol, modelling shows that two-thirds of the ozone layer would have been destroyed by 2065, dramatically increasing skin cancer cases and crop loss. Global cooperation prevented this scenario.
Ongoing challenges
- Illegal trade of ODSs remains a significant barrier to total elimination.
- Older equipment (for example, air conditioners, refrigerators, pesticides) still contains ODSs in many countries, particularly low-income regions.
- Continued monitoring, enforcement and technology transfer are required to ensure complete compliance.
- Long atmospheric lifetime of CFCs means that recovery will take decades even with zero future emissions.
Lessons for other global environmental issues
- The Montreal Protocol demonstrates that environmental progress is possible when global cooperation is strong, binding and equitable.
- Elements from the Montreal Protocol that could be applied to other challenges (for example, climate change mitigation and plastic pollution reduction) include:
- Legally binding targets
- Monitoring, enforcement and transparency
- Financial and technological support for lower-income countries
- Flexibility to incorporate new scientific evidence
Self review
- Why was the Montreal Protocol more successful than many other international environmental agreements?
- How did UNEP and financial support mechanisms contribute to global cooperation on ozone recovery?
- What scientific evidence shows that the planetary boundary for stratospheric ozone depletion has not been crossed?
- Why does full ozone recovery take decades even though the production of ODSs has almost completely stopped?
- Which strategies from the Montreal Protocol can be adapted to address climate change and plastic pollution, and why?
