by Jeevan Shemar
The Montreal Protocol on Substances that Deplete the Ozone Layer (1987) is an international treaty that came into effect in 1989 . It aims to protect the ozone layer by regulating the production and consumption of certain chemicals . The Montreal Protocol and (its precursor) the Vienna Convention For The Protection Of The Ozone Layer (1985) became the first treaties to achieve universal participation (meaning that every UN Member State participates in it). The Protocol is widely considered to have succeeded in fulfilling its aim of repairing the ozone layer, and consequently it is judged, by some to be one of the most successful examples of international cooperation in history .
The Montreal Protocol intended to facilitate the phasing out of the use of ozone depleting substances, in order to reduce the size of the Antarctic ozone hole.
Since the Protocol came into effect, the consumption of ozone depleting substances by countries in the European Union has greatly decreased, as has that of the United States of America. This has contributed to the reduction in the size of the Antarctic ozone hole — which is at its smallest size ever recorded. Consequently, it is widely agreed that the Montreal Protocol has been successful .
It is possible to categorise the main successes of the Protocol into three general categories — repletion of the ozone hole, reduction of the contribution to the rising global temperature and effective international cooperation.
First, in the absence of the Montreal Protocol, it is possible both that an ozone hole could have formed each year over the Arctic (in addition to the hole around the Antarctic) and that there could have been a global ozone hole by 2040. Also, it has been estimated that the Protocol, and its amendments, will have prevented up to two million cases of skin cancer each year by 2030 .
Second, it has been suggested that without the Protocol the global climate would be at least 25% hotter than it currently is . It has been estimated that the Protocol’s control measures have reduced greenhouse gas emissions by the equivalent of 135 gigatonne of carbon dioxide (CO2), between 1990–2010 . Owing to actions taken pursuant to the Kigali Amendment, it is expected that emissions of greenhouse gases, equivalent to 105 million tonnes of CO2, may be prevented . This would help to avoid up to 0.5°C of global temperature increase by 210 .
Third, the Protocol has been lauded as an example of successful international cooperation — combining the efforts of national governments , the UN  and the private sector . It has been praised by world leaders — from Pope Francis  to Narendra Modi (Prime Minister of India). It has been suggested that this aspect of the success of the Montreal Protocol can be attributed to the flexibility of the Protocol in the way in which its aims could be achieved . Additionally, it is possible to interpret the success of the Protocol as evidence that developing countries are willing, ready and able to fully cooperate in international environmental projects, provided that they receive appropriate assistance.
On these bases, the Montreal Protocol is widely perceived as a success.
Considering that the science of CFCs and ozone depletion was not comprehensively known in 1987  means that the Protocol successfully responded to a crisis about which scientists and world leaders were not wholly informed . Therefore, perhaps it is for this reason that the Montreal Protocol has been praised as a model for future international climate policy .
Nonetheless, despite the successes of the Montreal Protocol, the ozone hole still exists. This means that the international community cannot be complacent; there is still more to do .