Environment
Climate, sustainability, ecology, conservation, and environmental science
CFCs: The Miracle Chemicals That Tore a Hole in the Ozone Layer
CFCs were widely used refrigerants and propellants until the discovery that they destroy stratospheric ozone — their ban under the Montreal Protocol is history's most successful environmental treaty.
The Montreal Protocol: How the World Agreed to Save the Ozone Layer
The Montreal Protocol (1987) is the international treaty that phased out ozone-depleting substances — the only UN treaty ratified by all 198 member states.
The Kigali Amendment: Phasing Down the Greenhouse Gases That Replaced Ozone-Killers
The 2016 Kigali Amendment to the Montreal Protocol requires an 80-85% global phase-down of HFC refrigerants — potent greenhouse gases — estimated to prevent 0.5°C of warming.
HCFC Refrigerants: The Transitional Chemicals That Still Depleted the Ozone Layer
HCFCs were transitional refrigerants that replaced ozone-destroying CFCs in the 1980s but still caused ozone depletion, now being phased out globally by 2030.
HFC Refrigerants: Ozone-Safe but Climate-Damaging, Now Facing Global Phase-Down
HFCs replaced ozone-depleting refrigerants but turned out to be potent greenhouse gases, now subject to an 80-85% global phase-down under the 2016 Kigali Amendment.