America Officially Leaves the Paris Climate Agreement. As of Tuesday, the United States is no longer a party to the Paris agreement on climate change, becoming the only country in the world to abandon the international commitment to slow global warming. Earlier this month Mr. Trump said the United States would also leave the United Nations treaty that underlies the Paris agreement, which was unanimously ratified by the U.S. Senate in 1992 and signed by President George H.W. The United States is currently the planet’s second largest climate polluter after China. Wopke Hoekstra, the European Union climate commissioner, said abandoning the Paris agreement is a “clear absence of leadership” that will have “significant negative impacts” on America’s reputation.