President Obama was able to formally enshrine the United States in the agreement through executive measures because he did not impose new legal obligations on the country. The United States already has a number of instruments on the books, under laws already passed by Congress to reduce carbon pollution. The country officially joined the agreement in September 2016, after submitting its request for participation. The Paris Agreement was only able to enter into force after the formal accession of at least 55 nations representing at least 55% of global emissions. This happened on October 5, 2016 and the agreement came into force 30 days later, on November 4, 2016. The Paris Agreement is the first legally binding universal global agreement on climate change adopted at the Paris Climate Change Conference (COP21) in December 2015. Kyoto Protocol, 2005. The Kyoto Protocol [PDF], adopted in 1997 and entered into force in 2005, was the first legally binding climate treaty. It called on industrialized countries to reduce emissions by an average of 5% from 1990 levels and set up a system to monitor countries` progress. But the treaty did not force developing countries, including the major CO2 emitters China and India, to take action.
The United States signed the agreement in 1998, but never ratified it and then withdrew its signature. The Paris Agreement (the Paris Agreement)  is an agreement within the framework of the United Nations Framework Convention on Climate Change (UNFCCC) that deals with the reduction, adaptation and financing of greenhouse gas emissions and was signed in 2016. The language of the agreement was negotiated by representatives of 196 States Parties at the 21st UNFCCC Conference of parties held at Le Bourget, near Paris, France, and agreed on 12 December 2015.   Since February 2020, all 196 UNFCCC members have signed the agreement and 189 have left.  Of the seven countries that are not parties to the law, Iran and Turkey are the only major emitters. Saturday night was the culmination not only of two weeks of discussions, but also of more than 23 years of international attempts by the United Nations to fight together against this global problem. Since 1992, all governments around the world have committed to taking action to prevent dangerous warming. These efforts have been marked by discord and failure, the refusal of the largest emitters to participate, ineffective agreements and ignored contracts.