The Montreal Protocol protects our climate as well the ozone layer. By phasing-out the use of ozone-depleting substances that are very powerful greenhouse gases, the Protocol has avoided the equivalent of around 135 billion tonnes of CO2 emissions. The Protocol’s Kigali Amendment builds on this achievement, avoiding up to 0.4°C warming by 2100, by phasing-down the use of hydrofluorocarbons (HFCs), which are safe for the ozone layer but powerful greenhouse gases.
Since 1987, the effective implementation of the Montreal Protocol has successfully controlled the emissions of ozone-depleting substances (ODSs). This includes phasing-out the use of ODSs such as chlorofluorocarbons (CFCs) that are also very powerful greenhouse gases. For example, in terms of global warming one kilogram of CFC-12 is the equivalent of more 10,000 kilograms (ten tonnes) of carbon dioxide. Over the twenty-five years before the Montreal Protocol was signed, the warming effect of ODS emissions averaged between 20 per cent and 40 per cent of the effect of carbon dioxide emissions. As a result of the success of the Montreal Protocol, by 2018 the contribution of ODSs to warming had fallen 10-fold, to just 2-3 per cent. This reduction in global heating due to ODSs almost equals the increase caused by the increase in carbon dioxide emissions between 1987 and 2018.
The success of the Montreal Protocol in protecting climate becomes even more obvious in models of a future in which the Protocol did not exist, the so-called world avoided. These models suggest that the control of ODS emissions by the Montreal Protocol will have prevented temperature increases of 4-6°C at the poles and over 2°C in the tropics by 2070. This very significant warming would have been comparable to that predicted by the Intergovernmental Panel on Climate Change (IPCC) if we continue to fail in controlling emissions of greenhouse gases, especially carbon dioxide.
The parties to the Montreal Protocol have been proactive in ensuring that improved protection of the ozone layer does not undermine climate protection. The initial replacements for CFCs, hydrochlorofluorocarbons (HCFCs) posed much damaging to both global climate and the ozone layer than CFCs. However, HCFCs are not completely safe for the ozone layer, which led to the development of a second generation of replacements: hydrofluorocarbons (HFCs). HFCs pose no threat to the ozone layer but some are powerful greenhouse gases. For example, HFC-143a is more than 5,000 times more powerful than carbon dioxide. It was realised that if such high global warming HFCs were used extensively for air-conditioning and refrigeration in the future then they could cause as much as 0.5°C warming by 2100. In 2016 the parties agreed to introduce controls on these high global warming HFCs through the Kigali Amendment to the Protocol.
The Kigali Amendment will avoid around 0.4°C of global heating directly by encouraging the use of climate-safe refrigerants in place of high global warming HFCs. Further climate benefits are expected because the Kigali Amendment is encouraging a shift to more energy-efficient refrigeration and air-conditioning equipment. Improving energy efficiency could potentially double the direct climate benefits of shifting to climate-safe refrigerants. By supporting these changes in air-conditioning and refrigeration technologies, the Montreal Protocol continues to make a significant contribution to SDG Target 13.3, which includes improving ‘human and institutional capacity on climate change mitigation.’ By protecting the climate, the Montreal Protocol contributes not only to SDG13 but also to many other SDGs, described in other sections of this SDG website.