UN ambassador on Climate Change DiCaprio addressed the delegates, urging leaders to make protecting the environment a priority.

"Clean air and a liveable climate are inalienable human rights. And solving this crisis is not a question of politics, it is a question of our own survival. This is the most urgent of times and the most urgent of messages. The time to answer humankind's greatest challenge is now. We beg of you to face it with courage and honesty."

Chinese actress Li Bingbing also addressed the summit's opening ceremony.

李冰冰英文致辞全球气候峰会

"I remain optimistic that this climate summit will be about action and solutions as we pursue our common goals of a low carbon economy. We have an expression in Chinese. This means, "Where there's a will, there's a way."

Bingbing and Dicaprio are not the only stars at this years summit. Actress Emma Watson addressed the UN on Saturday in order to bring attention to the issue of gender equality.

Other messengers who have advised the world body on a variety of issues include actors Michael Douglas and Charlize Theron, and author and Holocaust survivor Elie Wiesel.