In October 2016 C.E., representatives from roughly 170 nations gathered in Kigali, Rwanda, and reached a milestone that climate scientists had been pushing for years. They agreed to phase down hydrofluorocarbons — a class of industrial gases so potent that a single pound can trap thousands of times more heat than a pound of carbon dioxide. The Kigali Amendment to the Montreal Protocol was born.
Key findings
- Kigali Amendment: Adopted in October 2016 C.E., the amendment adds HFCs to the Montreal Protocol’s list of controlled substances, committing signatory nations to a structured, legally binding phase-down schedule.
- HFC emissions reduction: Full implementation is projected to avoid more than 80 billion metric tons of CO₂-equivalent emissions by 2050 C.E. — enough to prevent roughly 0.5 degrees Celsius of warming above pre-industrial levels by century’s end.
- Global warming potential: HFCs have a 100-year global warming potential ranging from 12 to 14,800 times that of CO₂, making even small reductions in their use disproportionately significant for the climate.
Why HFCs needed their own agreement
The story starts with an earlier success. In 1987 C.E., the original Montreal Protocol targeted chlorofluorocarbons, or CFCs — the chemicals used in refrigerants and aerosols that were tearing a hole in the ozone layer. The agreement worked. CFCs were phased out, and the ozone layer began to recover.
But the replacement wasn’t clean. HFCs took over as the go-to coolant and refrigerant, solving the ozone problem while quietly building a new one. Unlike CFCs, HFCs don’t contain chlorine and don’t damage the ozone layer. But they absorb infrared radiation with remarkable efficiency. Some HFC variants are nearly 15,000 times more heat-trapping than carbon dioxide over a century, even though they linger in the atmosphere for only 10 to 20 years.
As air conditioning and refrigeration expanded rapidly across the developing world — a trend driven by rising incomes and rising temperatures — HFC use was on track to surge. Scientists warned that without intervention, HFC emissions alone could add a significant fraction of a degree to global warming by 2100 C.E.
What the Kigali Amendment actually requires
The amendment works through a tiered system, acknowledging that countries face different economic realities. Wealthier, industrialized nations committed to cutting HFC use by 45% by 2024 C.E. and by 85% by 2036 C.E., measured against their 2011–2013 baseline. A second group — including China and Brazil — committed to an 80% reduction by 2045 C.E. A third group, including several nations in the Middle East and parts of South Asia where air conditioning demand is highest, has until 2047 C.E. to reach the same target.
Countries experiencing extreme heat — defined as average monthly temperatures above 35°C for at least two months per year over a decade — can apply for additional flexibility. The amendment also provides technical and financial support to help developing nations transition to lower-impact alternatives.
As of March 2025 C.E., 171 states and the European Union had formally ratified the agreement, making it one of the most broadly adopted climate treaties in history.
Building on a proven foundation
The Kigali Amendment’s power comes partly from the institution it builds on. The Montreal Protocol, which entered into force in 1989 C.E., is the only United Nations treaty to achieve universal ratification — all 197 U.N. member states have signed on. Its track record is measurable: the ozone layer is healing, and CFC concentrations in the atmosphere have declined steadily.
That existing enforcement architecture — with its compliance mechanisms, multilateral fund, and established national implementation programs — meant the Kigali Amendment didn’t have to start from scratch. Nations already had the administrative structures in place to act.
Scientists Paul J. Crutzen, Mario Molina, and F. Sherwood Rowland, whose 1974 C.E. research first revealed CFCs’ threat to the ozone layer, helped lay the scientific groundwork that made both agreements possible. Molina and Rowland shared the Nobel Prize in Chemistry in 1995 C.E. for that work.
Lasting impact
The Kigali Amendment is widely regarded as among the most consequential climate agreements ever reached, partly because HFCs are so potent that even modest reductions yield outsized climate benefits. Avoiding 80 billion metric tons of CO₂-equivalent by mid-century is roughly equivalent to stopping two years of total global carbon emissions.
The agreement also drove investment in alternatives. Manufacturers began developing new refrigerants with far lower warming potential — including natural options like ammonia, CO₂-based coolants, and hydrofluoroolefins — accelerating an industry transition that might otherwise have taken decades longer.
For millions of people in the Global South, where reliable refrigeration affects food security and vaccine storage, the amendment’s support for developing-nation transitions matters beyond climate math alone. Getting the technology transition right means access to cooling doesn’t have to come at the expense of a stable climate.
Blindspots and limits
The Kigali Amendment is a phase-down, not a phase-out: HFCs will continue to be produced and used for decades under the agreed schedules. Enforcement depends on national implementation, and some countries have been slower to act than their commitments suggest. The flexibility provisions for extreme-heat nations, while reasonable, also extend timelines in regions where demand for air conditioning is growing fastest — meaning the gap between ambition and impact may widen before it narrows.
Read more
For more on this story, see: Wikipedia — Kigali Amendment
For more from Good News for Humankind, see:
- Renewables now make up at least 49% of global power capacity
- Indigenous land rights and 160 million hectares recognized ahead of COP30
- The Good News for Humankind archive on climate action
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