Factsheet: Entry Into Force Process for the Paris Agreement


The Paris Agreement was adopted by all Parties to the UNFCCC in December 2015, but there are several formal steps to go through before the Agreement enters into force in international law.

The first step: is for countries to sign the Agreement. Signing signals that country’s support for the Paris Agreement and its intention to align its domestic policies with the Agreement terms and start the process of formally joining the Agreement.

The second step: undertake domestic processes to formally join (or accept/approve/ratify) the Agreement and ‘consent to be bound’ by its terms and deposit the appropriate paperwork with the UN Secretary-General.

The third step: the next phase starts when a sufficient number of countries (55) covering a certain percentage of emissions (55%) have formally joined the Paris Agreement. When these two thresholds are met the Agreement will enter into force.

Once the conditions of the third step are met, entry into force will occur 30 days after the dual thresholds are achieved. Upon entry into force, the Agreement will become binding international law and countries that have formally joined will be subject to its provisions. Countries that have joined the Agreement can only pull out after a period of three years from the day it enters into force. After three years, a country that has joined the Agreement can choose to withdraw one year after submitting official notification of its intention. In effect, any country that has joined the agreement will be unable to legally exit the agreement for a period of four years.


  • On the 22 April 2016, the UN Secretary-General hosted government representatives possessing the authority to sign the Paris Agreement including Heads of State and Ministers of Foreign Affairs in New York. The representatives of over 175 countries signed the Agreement reiterating that country’s support for the Agreement and conveying that country’s commitment to follow through on the domestic process needed to join the agreement in accordance with each  country’s domestic requirements.
  • At the signing ceremony, nations were asked to announce an intended timetable for the process of their country formally joining the Agreement.
  • While in New York, leaders were invited to deposit their instruments of ratification (paperwork for officially joining) at the same time as signing the Agreement – it was not possible for those who had not yet finalised domestic ratification processes so instead a number of countries publicly announced their intent to formally join this year.
  • By signing the agreement without depositing accompanying instruments of ratification a country gives political support to the Paris Agreement and, according to the Vienna Convention on the Law of Treaties, has agreed to act in good faith “not to defeat the object and purpose of the treaty.”


  • The Paris Agreement is an international agreement that must be accepted by each country through its own domestic processes for joining. During this process, governments will ensure the compatibility of the Paris Agreement with their own legal and policy context.
  • Once a country joins the Agreement by approving it through its appropriate executive and/or legislative bodies, that country has agreed to be legally bound at the international level by the terms of the Agreement once the entire Agreement goes into effect. Once a country has ratified it then becomes a formal Party to the Agreement.
  • Each country’s domestic process for joining international agreements is different, and these can vary widely in their degree of complexity and timeframe.
  • Some countries will be able to ratify the Paris Agreement swiftly through use of executive powers (e.g. the USA), others can do so through executive power in consultation with the legislature (e.g. Australia), while others will need to pass it through and gain the approval of several legislative committees and then both houses of parliament / congress (e.g. Brazil).
  • Some countries have already been able to join: Fiji, Palau and the Marshall Islands are the first three countries to ratify the Paris Agreement. A total of two dozen countries have joined as of August 26, 2016.
  • And a large number of countries, including several major emitters, have made joining the agreement a priority – with a view to the Paris Agreement entering into force as early as possible, possibly in 2016.

Entry into force:

  • When an international agreement ‘enters into force’, it becomes legally-binding on all Parties to that Agreement. Entry into force will give the Paris Agreement the force of international law.
  • The Paris Agreement has a double trigger requirement for entry into force. The Paris Agreement stipulates that it will enter into force thirty days after at least 55 Parties to the UNFCCC, which account for at least 55 percent of total global greenhouse gas emissions, have deposited their instruments of ratification, acceptance, approval or accession with the UN Secretary-General.
  • Crossing the 55% emissions threshold will require a number of big emitters to ratify and several, including the United States and China who are both poised to do so.
  • Entry into force will rely entirely on how swiftly countries initiate and complete their domestic joining processes.
  • Following entry into force, countries that have joined the Agreement cannot provide notice that they wish to withdraw for at least 3 years.


How will the 55 percent of emissions be calculated for the purposes of the entry into force?

According to the Agreement, this requirement for the entry into force is to be calculated on the basis of the most up-to-date emissions data that has been communicated on or before the date of adoption of this Agreement by the Parties (i.e. when the Agreement was signed on December 12, 2015). These emission percentages have been captured in this table.

What does entry into force mean for countries that have not yet joined the agreement?

While countries that have not formally joined the Agreement are not obligated by its requirements, neither are they protected by its provisions nor are they able to actively participate it is governance. Countries that have not joined can observe meetings of the governing body of the agreement, but they can not vote on how the Agreement is implemented. Countries that join before the Agreement’s entry into force can provisionally apply the Agreement and inform the governing body that they have begun implementation.

Can additional countries join the Paris Agreement after it has already entered into force?

Countries can deposit their articles of accession with the UN and ratify the agreement at anytime either before or after it has entered into force. For parties that ratify after the Agreement has entered into force the Agreement will go into effect and become binding on that party 30 days after that party has deposited its instrument of accession with the UN.

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