The U.S. has formally ratified the global climate change agreement reached in Paris last year, as has China. This moves the Paris climate agreement closer to legal effectiveness -- but more nations must accept the pact before it can enter into force.
At issue is the Paris Agreement, an agreement brokered at the 21st Conference of the Parties of the United Nations Framework Convention on Climate Change (UNFCCC). In December 2015, over 190 countries meeting under UNFCCC adopted the Paris Agreement agreement to limit global warming. The Paris Agreement describes climate change as an
"urgent threat" and a "common concern of humankind." The agreement's aim is to strengthen global response to this threat, through a variety of means. These include the creation of individual national commitments to reduce greenhouse gas emissions, increased adaptation to climate change, and assistance for developing nations.
But the Paris Agreement has not yet taken its full legal force, because it contains a provision limiting its effectiveness until enough nations agree to comply. As is common for multilateral international agreements, the Paris Agreement calls for parties to express their consent to be bound by the agreement, by depositing instruments of ratification, acceptance, approval or accession with the depositary established by the convention. In this way, the agreement draws a distinction between Parties -- those signing the Agreement -- and those nations which have deposited their ratification instruments.
Under its Article 21, the Paris Agreement "shall enter into force
on the thirtieth day after the date on which at least 55
Parties to the Convention accounting in total for at least an
estimated 55 percent of the total global greenhouse gas emissions have
deposited their instruments of ratification, acceptance, approval or
accession." Practically speaking, this means that as new countries submit their ratifications, the convention's secretariat must calculate the total greenhouse gas emissions of Parties that have ratified
the Paris Agreement, as a percentage of global greenhouse gas emissions. Once the 55 percent threshold is hit, the Paris Agreement will become legally effective and operational. The
UNFCCC has said that while it cannot predict when this will occur, "it is conceivable that the Agreement may enter into force before 2020."
On April 22, 2016, the Paris Agreement was opened for signature. At the opening ceremony, 15 states deposited instruments of ratification. By September 1, reportedly 24 states accounting for just over 1% of global greenhouse gas emissions had ratified the agreement.
The Paris Agreement's path to effectiveness advanced on September 3, when President Obama announced that the U.S. and China had formally joined the Paris agreement in a ceremony in China. In recent years, these nations have been among the world's top emitters of carbon dioxide. As described by the White House, "Both leaders expressed satisfaction with jointly joining the Paris climate agreement and pledged to work together and with other parties to bring the Paris agreement into force as early as possible." The Obama administration also noted other recent U.S. climate actions taken jointly with China, including support for a proposed amendment to the Montreal Protocol to phase down the consumption and production of hydrofluorocarbons (HFCs) globally, and efforts to address international aviation emissions.
Following the U.S.-China announcement, the convention secretariat announced that as of September 7, 27 states had deposited instruments of ratification, acceptance or approval
accounting in total for 39.08% of the total global greenhouse gas emissions.