President of Vanuatu Baldwin Lonsdale signs the Paris Agreement on climate change, Friday, April 22, 2016 at U.N. headquarters (AP)

U.N. Secretary General Ban Ki-moon (R) embraces U.S. Secretary of State John Kerry who holds his two-year-old granddaughter Isabelle Dobbs-Higginson after signing the Paris Agreement on climate change at United Nations Headquarters in Manhattan, New York, U.S., April 22, 2016 (Reuters)

Palestinian Authority President Mahmoud Abbas signs the accord at the United Nations Signing Ceremony for the Paris Agreement climate change accord that came out of negotiations at the COP21 climate summit last December in Paris. on April 22, 2016 in New York City (AFP)

Nepalese Deputy Prime Minister Kamal Thapa signs the Paris Agreement on climate change held at the United Nations Headquarters in Manhattan, New York, U.S., April 22, 2016 (Reuters)

Poland's Prime Minister Beata Szydlo signs the Paris Agreement on climate change held at the United Nations Headquarters in Manhattan, New York, U.S., April 22, 2016 (Reuters)

Iran's Foreign Minister Mohammad Javad Zarif signs the Paris Agreement during the United Nations High-Level Event for the Signature of the Paris Agreement on April 22, 2016 in New York (AFP)

Deputy Prime Minister of Belgium Alexander De Croo signs the Paris Agreement during the United Nations High-Level Event for the Signature of the Paris Agreement April 22, 2016 in New York (AFP)

Rafael Pacchiano Alaman, Mexico's Minister of the Environment, signs the Paris Agreement on climate change, Friday, April 22, 2016 at U.N. headquarters (AP)

Germany's Minister of the Environment Barbara Hendricks signs the Paris Agreement on climate change, Friday, April 22, 2016 at U.N. headquarters (AP)

China's Vice Premier Zhang Gaoli signs the Paris Agreement during the United Nations High-Level Event for the Signature of the Paris Agreement April 22, 2016 in New York (AFP)

Attendees applaud at the conclusion of remarks at the opening ceremonies of the Paris Agreement on climate change held at the United Nations Headquarters in Manhattan, New York, U.S., April 22, 2016 (Rueters)

U.S. Secretary of State John Kerry kisses his two-year-old granddaughter Isabelle Dobbs-Higginson after signing the Paris Agreement on climate change at United Nations Headquarters in Manhattan, New York, U.S., April 22, 2016 (Reuters)

French President Francois Hollande (2nd from L) listens as he holds a press conference with United Nations Secretary-General Ban Ki-moon as French Minister of Ecology, Sustainable Development and Energy Segolene Royal (L) and Costa Rican diplomat Christiana Figueres listen on the sidelines of the Paris Agreement on climate change at the United Nations Headquarters in Manhattan, New York, U.S., April 22, 2016 (Reuters)