PARIS, FRANCE - DECEMBER 12: Executive Secretary of the United Nations Framework Convention on Climate Change (UNFCCC) Christiana Figueres (L 2), Secretary General of the United Nations Ban Ki Moon (C), Foreign Affairs Minister and President-designate of COP21 Laurent Fabius (R 2), and France's President Francois Hollande (R) raise hands together after adoption of a historic global warming pact at the COP21 Climate Conference in Le Bourget, north of Paris, on December 12, 2015. (Photo by Arnaud BOUISSOU/COP21/Anadolu Agency/Getty Images)

PARIS, FRANCE - DECEMBER 12: Executive Secretary of the United Nations Framework Convention on Climate Change (UNFCCC) Christiana Figueres (L 2), Secretary General of the United Nations Ban Ki Moon (C), Foreign Affairs Minister and President-designate of COP21 Laurent Fabius (R 2), and France's President Francois Hollande (R) raise hands together after adoption of a historic global warming pact at the COP21 Climate Conference in Le Bourget, north of Paris, on December 12, 2015. (Photo by Arnaud BOUISSOU/COP21/Anadolu Agency/Getty Images)