Full coverage: G20 Hangzhou Summit

The United States and China have formally joined the sweeping global climate change agreement reached in Paris last year.

Chinese President Xi Jinping (L), U.S. President Barack Obama (R) and Secretary-General of the United Nations Ban Ki-moon attend the deposit of instruments of joining the Paris Agreement in Hangzhou, capital city of east China's Zhejiang Province, Sept. 3, 2016. (Xinhua/Li Tao)

Chinese President Xi Jinping and U.S. President Barack Obama delivered documents to U.N. Secretary-General Ban Ki-moon entering their countries into the pact. They did this during a ceremony Saturday on the sidelines of the G20 Summit.

Xi said with this agreement China and the U.S. have displayed their determination to tackle a global challenge. Obama echoed this point.

Ban welcomed the move, saying the actions add “powerful momentum” to implementing the agreement this year.