The Montreal Protocol and the Pathway from CFCs to Climate-Friendly Compounds and Technologies

The Montreal Protocol was created in 1987 to protect the ozone layer through the regulation of ozone depleting substances (ODSs) such as chlorofluorocarbons (CFCs) and halons. The Protocol initially only slowed the growth of ODS concentrations in our atmosphere. However, the Protocol was designed to allow for modification as scientific understanding improved. Amendments further slowed ODS growth, and reversed the increase of most ODSs in our atmosphere by the mid-1990s. A more rapid phase-out of CFCs was enabled by use of hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) as transitional substitutes. The advantage of HCFCs was their weaker ozone impact, while HFCs have only a very small indirect ozone impact. The disadvantage of HCFCs and HFCs was was that they are potent greenhouse gases, just like the CFCs. Because of their large global warming potentials, unchecked emissions would lead to important climate impacts. While HCFCs were controlled, the strong future growth of HFCs threatened to offset the climate forcing benefits gained from controlling ODSs. This HFC climate threat was mitigated by the Parties’ adoption of the Kigali amendment in 2016. In this talk we will review the evolution of the Protocol with respect to ODS and HFC projections. We will also cover current and future estimates of climate forcing contributions by ODSs and HFCs, discuss the elements of the Kigali amendment and its expected impact, and briefly discuss issues related to HFC replacement substances and technologies.