How did the United Nations secretary-general’s 2016 signing ceremony help advance the Paris Agreement?

The United Nations secretary-general’s signing ceremony, held on April 22, 2016, at United Nations headquarters in New York City, served as a critical step in the formalization of the Paris Agreement.

By opening the treaty for signature, the event initiated the necessary process for countries to commit to the accord. This period of signing, which lasted until April 21, 2017, was essential for gathering the international support required for the agreement to enter into force. The treaty officially became active on November 4, 2016, once 55 parties—representing at least 55 percent of global greenhouse gas emissions—had ratified it. This ceremony helped build the momentum needed to reach those specific thresholds, transitioning the agreement from a negotiated text into a functional international treaty.12