Leonardo DiCaprio, the Hollywood actor and an environmental activist is feeling optimistic now that the debate over climate change has started to wane and world leaders are finally starting to take it more seriously, reports ABC News.

"The scientific community has been screaming out loud. Ninety-nine per cent of the scientific community is in agreement that man is contributing to (climate change)," DiCaprio told The Associated Press on the red carpet for his new film, "The Revenant" on Wednesday.

"The argument is over. Anyone that doesn't believe that climate change is happening doesn't believe in science," said DiCaprio, who has remained an active player for the issue.

The actor previously has addressed the United Nations on climate control, donated millions of dollars to environmental causes, and narrated the 2014 short film, "Carbon," which presents ideas for climate change solutions.

But after the UN Climate Conference in Paris, which ended last month, he feels world leaders are finally willing to address the issue more seriously.

"No one has the answer what the future is going to look like, and no one can foresee the dramatic effect that climate instability will have on our planet and the biodiversity in it, but I'm just very proud for the first time we've taken a step in the right direction," Dicaprio said.