Stratospheric Ozone Treaties and the Kigali Amendment: Ratification Considerations
Legal Sidebar
Stratospheric Ozone Treaties and the Kigali
Amendment: Ratification Considerations
March 23, 2022
For at least four decades, the United States has been engaged in global efforts to protect the earth’s
stratospheric ozone layer. The stratospheric ozone layer absorbs ultraviolet solar radiation that can
otherwise result in increased risks of skin cancers, cataracts, and harm to agricultural crops and marine
life. Global measures to restore stratospheric ozone include the framework Vienna Convention for the
Protection of the Ozone Layer, ratified with Senate consent in 1986, and its affiliated Montreal Protocol
on Substances that Deplete the Ozone Layer, ratified with Senate consent in 1988. Both treaties have
universal membership of all United Nations member and observer states.
Consistent with their Montreal Protocol obligations, countries have effectively reduced ozone-depleting
substances. According to the U.S. Environmental Protection Agency (EPA), the atmospheric levels of
nearly all substances subject to the Montreal Protocol have declined substantially in the past two decades,
resulting in improvements to the ozone layer. However, some of the chemicals known as
hydrofluorocarbons (HFCs), which emerged in the 2000s as substitutes for some of the regulated ozone-
damaging substances, are greenhouse gases many times more potent than carbon dioxide.
To address HFC emissions, in 2016, countries adopted the fifth amendment to the Montreal Protocol in
Kigali, Rwanda (the “Kigali Amendment”). The Kigali Amendment adds HFCs as a new class of
substances subject to control measures and requires their gradual phasedown.
In 2020, Congress passed the American Innovation and Manufacturing Act (“AIM Act”) to limit HFCs. In
2021, the President submitted the Kigali Amendment to the Senate for advice and consent to ratification.
This Legal Sidebar addresses the context, content, and legal implications of possible ratification of the
Kigali Amendment.
Background: Vienna Convention and Montreal Protocol
The United States is an original signatory to the Vienna Convention, which was ratified in 1986 with the
advice and consent of the Senate. As a framework instrument, the Vienna Convention sets forth
expectations of its member countries, such as meeting regularly and making subsequent global decisions
for ozone protection, cooperating with other countries to conduct research and assessments, exchanging
information, and adopting “appropriate measures” to protect the ozone layer.
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The United States is also a party to the Montreal Protocol, which builds on the Vienna Convention with
specific targets and timetables to phase down and phase out the production and consumption of certain
industrially manufactured substances that impact stratospheric ozone. Article 2 of the Montreal Protocol
lists specific substances and time frames for phasedown and phaseout; a series of technical annexes list
individual compounds and their relative potentials to impact stratospheric ozone. These limits on the
production and use of listed substances are commonly referred to as control measures.
The Montreal Protocol has special provisions in Article 5 for countries with the least per capita
consumption of listed substances. These Article 5 countries have longer time frames to reduce
consumption and production of listed substances. Countries that have been responsible for most industrial
production of Montreal Protocol–regulated substances (non–Article 5 countries), including the United
States, contribute financing that supports other countries’ control measures. Article 4 of the Montreal
Protocol contains trade limitations for countries that do not become party to it.
The United States ratified the Montreal Protocol in 1988 following a resolution of ratification in the
Senate adopted by an 83-0 vote. In 1990, Congress passed Clean Air Act amendments that included
stratospheric ozone control measures in Title VI of the Act. Title VI implements U.S. obligations under
the Montreal Protocol to phase down and phase out listed substances. Since Title VI’s enactment, the
United States has successfully reduced the production and consumption of several ozone-depleting
substances consistent with its obligations.
Amendments and Adjustments
The Clean Air Act obligates EPA to update the schedules for control measures based on modifications to
the Montreal Protocol that are known as amendments or adjustments. A treaty amendment is required for
new substantive obligations, including any decision to list new substances and related control measures.
(The Kigali Amendment is an example, as it lists and phases down HFCs as a new class of substances
subject to control measures.) An adjustment is a more limited decision by the treaty Parties to modify the
phasedown schedules of already-listed substances. An amendment requires formal ratification by
individual countries; an adjustment requires a supermajority decision: at least two-thirds of countries that
represent independent majorities of Article 5 and non–Article 5 countries.
The four amendments to the Montreal Protocol prior to the Kigali Amendment have each been ratified by
every country that is a party to the Protocol, including the United States with Senate consent:
The 1990 London Amendment (Senate consideration here) added new chemicals to the
list of regulated substances and provided for their phaseout. It also established a financial
mechanism and banned Parties from trading listed substances with non-Parties.
The 1992 Copenhagen Amendment (Senate consideration here) added new chemicals
and schedules to the list of regulated substances and applied all subsequent amendments
and adjustments to Article 5 countries following a review of financing.
The 1997 Montreal Amendment (Senate consideration here) added provisions related to
a specific substance and addressed licensing procedures. In 1998, Congress amended
Title VI of the Clean Air Act to reflect new commitments beyond the initial 1990
amendments.
The 1999 Beijing Amendment (Senate consideration here) added a new chemical
(bromochloromethane) to the list of regulated substances, implemented stricter controls
for two listed substances, and created a “basic domestic needs” exception for Article 5
countries.
In addition to the compliance, finance, and trade provisions listed above, these amendments added new
annexes of listed chemicals and products that impacted stratospheric ozone levels. By 2000, the lists had
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expanded to include fully halogenated chlorofluorocarbons (CFCs), carbon tetrachloride, methyl
chloroform, HFCs, hydrobromofluorocarbons, methyl bromide, and bromochloromethane. All of these
chemicals are considered ozone-depleting substances.
Kigali Amendment
In 2016, countries adopted the fifth amendment to the Montreal Protocol in Kigali, Rwanda. The United
States is considering ratification. The Kigali Amendment adds HFCs as a new class of substances subject
to control measures and requires their gradual phasedown. The decision by the treaty Parties to add HFCs
under the Montreal Protocol was notable because HFCs do not directly reduce stratospheric ozone but
instead were included due to their use as substitutes for other ozone-depleting substances. While scientists
do not consider HFCs to substantially deplete stratospheric ozone, they can be hundreds to thousands of
times “more potent than carbon dioxide” in contributing to climate change.
The Kigali Amendment:
adds HFCs as a new category of listed substances and creates a new annex that lists 18
specific HFC compounds subject to control measures;
requires all countries that ratify the Amendment to gradually phase down the production
and consumption of HFCs by 80%-85%. Specifically, non–Article 5 countries (including
the United States, if ratified) reduce the production and consumption of HFCs by 10%
from 2019 to 2023, increasing to 85% by 2036 (Article 5 countries must gradually reduce
HFC production and consumption to either 80% by 2040 or 85% by 2047);
specifies the baseline for HFC reductions to be calculated based on average consumption
and production for 2011-2013 plus 15% of the average consumption of a different class
of listed substances, hydrochlorofluorocarbons;
allows Parties to make adjustments to the phasedown schedules and global warming
potential values;
updates the Montreal Protocol’s financial mechanism to support Article 5 countries’
incremental costs not otherwise covered elsewhere in transitioning to technologies that do
not use HFCs;
requires that all ratifying countries ban exports and imports of HFCs to or from any
country that has not ratified the Amendment, effective in 2033;
authorizes countries to voluntarily impose more stringent measures to regulate HFCs; and
makes technical and conforming changes to the Montreal Protocol.
The Kigali Amendment entered into force in 2019 for any country that has ratified it. As of January 20,
2022, 130 countries have become Parties to the Amendment.
Addressing HFCs Domestically: The AIM Act
After the Kigali Amendment was adopted, and before the President requested the Senate to approve its
ratification, Congress passed the AIM Act, which authorizes EPA to phase down domestic HFC
consumption and production on a schedule similar to that identified in the Kigali Amendment.
Initially, some stakeholders opposed the AIM Act on the basis that it was so closely aligned with the
Kigali Amendment that it circumvented the Senate advice-and-consent process for treaties under Article II
of the Constitution. Others expressed support for the AIM Act as potential implementing legislation for
the Kigali Amendment. Statutory requirements under the AIM Act align with key provisions of the Kigali
Amendment in the following ways:
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The AIM Act identifies the same 18 HFCs for a phasedown schedule as those listed
Kigali Amendment Annex F.
The HFC phasedown schedule under the AIM Act begins with a 10% reduction in
production and consumption from 2020 to 2023, increasing to 85% in 2036. Similar to
Kigali, the baseline for reductions derives from a 2011-2013 baseline plus a fraction of
HFC and of CFC production.
The AIM Act requires EPA to promulgate regulations to maximize reclamation, minimize
equipment leaks, and facilitate technology transitions through sector-based restrictions.
This is similar to the requirement in paragraphs 6 and 7 of the Kigali Amendment to use
approved technologies that destroy HFCs created during industrial manufacturing.
EPA has begun developing programs to phase down HFCs under AIM Act authorities.
Considerations for Congress
There are different views on U.S. ratification of the Kigali Amendment. One legal consideration as
Congress evaluates the Kigali Amendment is what benefit additional legislation (or the lack thereof)
might have in implementing the treaty, if ratified. President Biden’s letter to the Senate recommending
ratification states the United States already has the authority to implement the Kigali Amendment under
the AIM Act and Clean Air Act. In addition to reducing HFC production and consumption, the Kigali
Amendment also requires countries to report on HFC emissions and regulate exports and imports of
products containing HFCs. If the United States does not ratify the Kigali Amendment, it would not be
subject to those additional reporting requirements, but it would still phase down HFCs under the AIM
Act.
Also, if the United States does not ratify the Kigali Amendment, U.S. producers and consumers would
eventually be unable to take advantage of trading HFC products with countries that have ratified the
Amendment due to the prohibition on Parties trading HFCs with non-Parties.
While many in industry support the Kigali Amendment, some stakeholders have expressed reservations
about addressing greenhouse gases such as HFCs under the Montreal Protocol. Others oppose ratification
due to concerns about implementation costs and differentiation between Article 5 and non–Article 5
countries.
Adjustments
It is possible that, at a later date, countries could decide to adjust the time frames for HFC phasedown.
Article 2.9 of the Montreal Protocol and the Kigali Amendment allow a supermajority of countries to
adopt subsequent modifications to HFC phasedown schedules. Such a change could result in divergences
from the AIM Act phasedown schedules. In the past, adjustments to schedules of other listed substances
have accelerated phasedowns.
On the one hand, if the United States were to ratify the Kigali Amendment and a supermajority of
countries subsequently adopted modifications that were different from the AIM Act, the United States
would have the option of undertaking additional domestic measures in order to comply with the modified
schedules. For example, Title 42, Section 7675(f), of the U.S. Code is a provision of the AIM Act that
authorizes EPA to undertake rulemaking to accelerate HFC phasedown schedules if it receives an
appropriate rulemaking petition. Congress could also pass new legislation at that time, or EPA might seek
to rely on an alternate authority for HFC regulation (discussed elsewhere).
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On the other hand, if a future adjustment, AIM Act amendment, or EPA regulation were to result in
divergent approaches between domestic and international obligations, the United States would have the
options of abrogating its treaty obligations or withdrawing from the treaty.
Diplomacy
Some stakeholders have questioned the need for ratification because the AIM Act requires a domestic
phasedown of HFCs under a schedule that appears to align with the Kigali Amendment. The executive
branch maintains that ratification will “ensure the United States continues to have a full voice to represent
U.S. economic and environmental interests” on the international stage.
The 1990 amendments to Title VI of the 1990 Clean Air Act implement the Montreal Protocol in part by
requiring the President to pursue international agreements, develop rules, negotiate multilateral treaties,
and advance proposals at the U.N. to protect the stratosphere. The United States was formally involved in
Kigali Amendment negotiations since at least 2009, submitting various amendment proposals and joining
in the decision to adopt the Amendment.
There are other environmental treaties that the United States has not ratified—such as the Law of the Sea
Convention and Basel Convention on the Control of Transboundary Movements of Hazardous Wastes—
despite playing an active role in treaty negotiations. The degree to which non-ratification may affect U.S.
influence in subsequent global decisionmaking is beyond the scope of this analysis.
Author Information
Kristen Hite
Legislative Attorney
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