"Perhaps the single most successful international agreement to date has been the Montreal Protocol." -Kofi Annan, former Secretary General of the United Nations
The Montreal Protocol, finalized in 1987, is a global agreement to protect the stratospheric ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS). The stratospheric ozone layer filters out harmful ultraviolet radiation, which is associated with increased prevalence of skin cancer and cataracts. The United States ratified the Montreal Protocol in 1988 and has joined its four subsequent amendments. The United States has been a leader within the Protocol throughout its existence, and has taken strong domestic action to phase out the use of ODS such as chlorofluorocarbons (CFCs) and halons. Over two million tons of ODS have been phased out under the Montreal Protocol since its inception.
A great deal of work continues to ensure protection of the ozone layer, particularly in developing countries. Through the Protocol's Multilateral Fund, over $3 billion has been used to help lesser-developed countries make the transition out of ODS The Montreal Protocol has been amended four times since 1987. These amendments introduced additional control measures and regulated additional ODS.
The Montreal Protocol’s Scientific Assessment Panel estimates that implementation of the Montreal Protocol may allow the ozone layer to return to its pre-industrial levels by 2060-2075. The United States continues to work with its partners from all over the world to ensure that progress moves forward on protection of the stratospheric ozone layer.
In April 2015, the United States, Mexico and Canada jointly submitted an amendment proposal to the Montreal Protocol that includes provisions to phase down the production and consumption, and eliminate byproduct emissions of hydrofluorocarbons (HFCs), potent greenhouse gases with global warming potential (GWP) thousands of times that of carbon dioxide. HFCs are widely used alternatives to hydrochlorofluorocarbons (HCFCs) chlorofluorocarbons (CFCs) and other ODS that are being phased-out under the Montreal Protocol. If adopted, the amendment would reduce HFCs through 2050 by more than 90 gigatons of CO2-equivalent emissions, which is about 2 years of current global anthropogenic emissions of all greenhouse gases. A summary of the amendment proposal is available here.
The full text of the Protocol and other publications are available through the UNEP Ozone Secretariat.