2.3 Montreal Protocol and International Agreements

Why International Agreements Are on the Exam

U.S. refrigerant rules did not appear in a vacuum — they implement international treaties. The EPA 608 exam expects you to know the treaty framework because it explains why certain refrigerants are banned, phased out, or phased down, and when. Two harms drive everything: ozone depletion (measured as ODP) and climate warming (measured as GWP). Keeping these two ideas separate is the single most important conceptual skill in this chapter.

The Ozone Layer and the Role of Chlorine

The ozone layer is a band of ozone (O3) molecules in the stratosphere, roughly 10–30 miles up, that absorbs 97–99% of the sun's harmful ultraviolet-B (UV-B) radiation. Depletion lets more UV-B reach the surface, raising rates of skin cancer and cataracts and damaging crops and marine phytoplankton.

Chlorine is the villain. CFC and HCFC molecules are extremely stable, so they drift intact into the stratosphere (a 2–5 year journey). There, intense UV breaks them apart and frees chlorine atoms. Each chlorine atom catalytically destroys ozone — and is regenerated afterward — so a single chlorine atom can destroy on the order of 100,000 ozone molecules before it is finally deactivated. HFCs and HFOs contain no chlorine, which is exactly why their ODP is zero.

The Montreal Protocol (1987)

The Montreal Protocol on Substances that Deplete the Ozone Layer was adopted in 1987 and has been ratified by 198 parties — the first and only UN treaty to achieve universal ratification. It set binding phaseout schedules for ozone-depleting substances. The developed-country deadlines you should recognize:

The treaty works through a stepwise reduction: production caps tighten over time rather than dropping to zero overnight. This is why R-22 (an HCFC) had its U.S. production and import end on January 1, 2020, ahead of the broader 2030 HCFC deadline — EPA front-loaded the most common HCFC.

Ozone Depletion vs. Climate Framing

The Montreal Protocol was designed for ozone protection. But the substitutes industry adopted — HFCs — turned out to be potent greenhouse gases. They solved the ozone problem (zero ODP) while worsening the climate problem (high GWP). That mismatch set up the next chapter of the treaty.

For the Exam: Lock in three facts about chlorine and ODP. (1) Chlorine destroys ozone; HFCs/HFOs have none, so ODP = 0. (2) One chlorine atom destroys ~100,000 ozone molecules. (3) CFCs have the highest ODP (R-11 and R-12 = 1.0); HCFCs are lower (R-22 = 0.055). Do not confuse ODP with GWP — a refrigerant can have zero ODP and still have an enormous GWP.

The Kigali Amendment (2016)

The Kigali Amendment, adopted in Kigali, Rwanda in 2016, extended the Montreal Protocol to cover HFCs — not because they deplete ozone (they do not) but because of their climate impact. Key points:

• It mandates a global phasedown of HFC production and consumption — more than an 80% reduction over roughly 30 years.
• Developed countries began stepping down HFCs in 2019; many developing countries freeze and then reduce on later schedules (with a freeze around 2024 for one major group).
• The United States ratified the Kigali Amendment in 2022, committing to the international HFC phasedown.

The Kigali Amendment is the bridge between the old ozone-focused regime and the new climate-focused regime. In the U.S., it is implemented domestically by the AIM Act (covered in Section 1.4), which is where the concrete percentages and dates live.

Putting the Timeline Together

• 1987 — Montreal Protocol: attacks ozone-depleting substances (CFCs, halons, HCFCs).
• 1996 — CFC phaseout complete in developed countries.
• 2016 — Kigali Amendment: extends the treaty to climate-warming HFCs.
• 2020 — R-22 production/import ends in the U.S.
• 2022 — U.S. ratifies Kigali.
• 2030 — HCFC phaseout complete in developed countries.

A Quick Word on the Vienna Convention

One more name occasionally appears on the exam: the Vienna Convention for the Protection of the Ozone Layer (1985). It was the framework treaty — the diplomatic agreement that nations would cooperate on ozone science and policy — but it set no binding targets. The Montreal Protocol (1987) is the implementing agreement that added the actual, enforceable phaseout schedules.

If a question contrasts the two, remember: Vienna = framework/cooperation, Montreal = binding phaseouts. Together they explain why the international response to ozone depletion succeeded where many environmental efforts stalled — the science framework came first, then the binding cuts, then the Kigali climate extension.