UNITED NATIONS — When international negotiators reached a first-of-its kind climate change agreement in Paris this month, the United Nations’ normally low-key leader, Ban Ki-moon, celebrated onstage, arms raised in victory and more exuberant than many had ever seen him before.

Nearly nine years had passed since, in his first days as secretary-general, Ban surprised world leaders by making global warming a top item on his agenda. Now, on the eve of his final year in office, the cheers in Paris marked the culmination of his nonstop campaign, pressed with world leaders at summit after summit and in locales including melting glaciers and islands at risk of disappearing.

It was an emotional moment, and looking back at the road to Paris in an interview with The Associated Press, Ban paid tribute to many people, including the leaders of the United States, China, India and France. He also spoke proudly of his own role.