Chinese actress and UNEP goodwill ambassador Li Bingbing speaks at the UN Climate Change Summit on Tuesday. Provided to China Daily

UNITED NATIONS - The United Nations Climate Summit opened here Tuesday with an appeal from UN Secretary General Ban Ki-moon for global action to address climate change.

"Climate change threatens hard-won peace, prosperity, and opportunity for billions of people," Ban said during his opening remarks. "Today we must set the world on a new course."

Declaring climate change the defining issue of our time, Ban told the delegates, "We need all hands on deck."

"I am asking you to lead," Ban "We are not here to talk. We are here to make history."

Opening at 8 a.m. (1300 GMT), the summit started with a video produced by Lyn Lear and narrated by Oscar winner Morgan Freeman.

It draws more than 120 heads of state and government to announce their vision and commitments, as well as make announcements on actions that will reduce emissions, enhance resistance to climate change and mobilize financing for climate action.

Chinese Vice Premier Zhang Gaoli, who is here to attend the summit as President Xi Jinping's special envoy, will deliver a keynote speech to explain China's stance and measures on climate change.

The UN Climate Summit is expected to set the stage for a crucial conference in Paris in December 2015 aimed at finalizing a new global climate change pact.

President of the General Assembly Sam Kutesa highlighted the two objectives of the meeting -- to generate ambitious actions on cutting gas emissions, increasing resilience and propelling the world toward a cleaner, greener economy, and to mobilize political will toward a meaningful, universal climate change agreement in 2015.

He reminded the representatives from government, business, finance and civil society that, climate change is a "potentially irreversible" threat that limits development options and efforts in eradicating poverty and achieving sustainable development.

Over the course of the day, participants will announce national actions and ambition plans, and take part in thematic discussions on topics ranging from climate science to health and jobs.

Also addressing the opening session are New York City Mayor Bill de Blasio, former U.S. Vice President Al Gore, Chinese actress and Goodwill Ambassador of UN Environment Program (UNEP) Li Bingbing, and Hollywood star Leonardo DiCaprio, a newly-appointed UN Messenger of Peace.