The Paris Agreement is the culmination of a quarter-century of international climate diplomacy launched with the U.N. Framework Convention on Climate Change (UNFCCC) at the Earth Summit in Rio de Janeiro.  Here’s a brief recap of the evolution of the global climate effort and the role played by the United States.

UNFCCC

President George H.W. Bush joined more than other worlds leaders at the 1992 Rio Earth Summit to adopt a series of international environmental agreements, including the UNFCCC.  The president later ratified the UNFCCC with the advice and consent of the U.S. Senate, and the agreement has since been embraced by virtually every nation on earth.

The UNFCCC sets a long-term objective of avoiding dangerous human interference with the climate system.  Toward that end, the agreement:

• commits all nations to take steps to mitigate greenhouse gas emissions;
• establishes the principle of “common but differentiated responsibilities and respective capabilities” (CBDRRC), recognizing that countries vary in their contributions to climate change and capacities to address it, so their obligations will likewise vary; and
• commits developed countries to assist developing countries in reducing emissions and coping with climate impacts.

Governed by the Conference of Parties (COP), which meets annually, the UNFCCC serves as the foundation of an evolving global climate effort.

Kyoto Protocol

At COP 1 in 1995, UNFCCC parties decided to accelerate climate efforts by launching negotiations toward a first sub-agreement.  They agreed that, consistent with the principle of CBDRRC, the new agreement would establish binding targets and timetables for reduce developed country emissions, but no new commitments for developing countries.  (In the nonbinding Byrd-Hagel resolution, the U.S. Senate rejected this premise, saying the agreement should also include new greenhouse gas limits for developing countries.)

The resulting Kyoto Protocol was adopted at COP 3 in 1997.  Largely at the insistence of the United States, the agreement incorporated a series of “flexible,” or market-based, mechanisms enabling developed countries to use different forms of emissions trading to achieve their targets more cost-effectively.  President Clinton, however, never submitted the protocol to the Senate, and shortly after his election, President George W. Bush announced that the U.S. would not ratify it.

Other countries proceeded to ratify the agreement and it entered into force in 2005.  Its initial emission targets, however, extended only through 2012, and when it came time to negotiate a second round through 2020, several other developed countries declined to go along.  The Kyoto Protocol technically remains in force, but its targets cover only a small fraction of global emissions, and there is no expectation of future targets.  One element of the protocol that may continue is the Clean Development Mechanism, which certifiable emission reductions in developing countries as tradable emission offsets.

Copenhagen and Cancun Agreements

As it became clear that the Kyoto Protocol was faltering, UNFCCC parties struggled to develop an alternative framework that would facilitate stronger action by all countries, both developed and developing.

The 2007 Bali Action Plan launched talks aimed at a new agreement providing for the UNFCCC’s “full, effective and sustained implementation.”  The agreement was to be adopted at COP 15 in Copenhagen in 2009.  More than 100 world leaders converged on Copenhagen for the summit, but negotiators were unable to overcome their differences.  President Barack Obama and other leaders stepped in to quickly hammer out the Copenhagen Accord, but a handful of countries objected, keeping it from being formally adopted by the COP.

The Copenhagen Accord, while only a political agreement, reflected significant progress on several fronts.  It set a goal of limiting global temperature increase to 2 degrees Celsius; called on all countries to put forward mitigation pledges; established broad terms for the reporting and verification of countries’ actions; set a goal of mobilizing $100 billion a year by 2020 in public and private finance for developing countries; and called for the establishment of a new Green Climate Fund.

At COP 16 the following year in Cancun, parties adopted the Cancun Agreements, effectively formalizing the essential elements of the Copenhagen Accord under the UNFCCC.  The Cancun Agreements were regarded as an interim arrangement through 2020, and parties left the door open to further negotiations toward a legally binding successor to the Kyoto Protocol.

Paris Agreement

At COP 17 in Durban, South Africa, parties adopted the Durban Platform for Enhanced Action, launching talks aimed at achieving a comprehensive new agreement starting in 2020.  They left open the legal nature of the agreement and how it would address differentiation between developed and developing countries.

World leaders once again at COP 21 in Paris, and on December 12, 2015, parties adopted the landmark Paris Agreement.  The agreement represents a hybrid of the “top-down” Kyoto approach and the “bottom-up” approach of the Copenhagen and Cancun agreements.  It establishes common binding procedural commitments for all countries, but leaves it to each to decide its nonbinding “nationally determined contribution” (NDC). The agreement establishes an enhanced transparency framework to track countries’ actions, and calls on countries to strengthen their NDCs ever five years.

Given its hybrid legal nature, President Obama was able to ratify the Paris Agreement through executive action, without seeking Senate advice and consent.  The agreement entered into force in late 2016, much earlier than expected, and parties are now developing detailed implementing rules to be adopted at COP 24 in 2018.

In June 2017, President Donald Trump announced his intent to withdraw the United States from the Paris Agreement.  However, withdrawal cannot formally be initiated until November 4, 2019, and would not take effect until a year later.  The Trump Administration has meantime indicated that it will continue negotiating the Paris rules and may remain in the agreement under revised terms.