UN signing ceremony for Paris Agreement on Climate Change (25 images)

Canadian Prime Minister Justin Trudeau plays with the two-year-old granddaughter of U.S. Secretary of State John Kerry, Isabelle Dobbs-Higginson, before both officials signed the COP21 Climate Change Agreement on Earth Day, April 22, 2016, at the United Nations General Assembly Hall in New York. Photo by U.S. Department of State/UPI

United States Secretary of State John Kerry holds granddaughter Isabelle Dobbs Higginson while he signs the Paris Agreement on Climate Change at the headquarters of the United Nations in New York City on April 22, 2016. A historic meeting takes place today as 155 countries have committed to sign the Paris Agreement on Climate Change. Photo by John Angelillo/UPI

United Nations Secretary-General Ban Ki-moon meets UN Messenger of Peace (with a special focus on climate change) Leonardo DiCaprio at the United Nations in New York on April 22, 2016. DiCaprio was one of many high profile guests and world leaders attending the signing ceremony for the Paris Agreement on Climate Change. UN Photo by Eskinder Debebe/UPI

U.S. Secretary of State John Kerry sits backstage with Canadian Prime Minister Justin Trudeau and Italian Prime Minister Matteo Renzi before all three officials signed the COP21 Climate Change Agreement on Earth Day, April 22, 2016, at the United Nations General Assembly Hall in New York. Photo by U.S. Department of State/UPI