"This is the most monumental issue facing our generation and the next, and we need to solve it incredibly quickly," the Oscar winner told ET's Kevin Frazier on Monday.
The issue is so important to DiCaprio that it got him to step out from under the veil of a character.
"I like to keep my private life as private as possible, but if I'm going to be the person that's the narrator of this film. I wanted to take center stage as somebody who asks questions in a way that people would be able to digest it better," DiCaprio explained.
As a movie star and a U.N. Messenger of Peace, DiCaprio had access to many influential figures who make an appearance in the movie such as Elon Musk, John Kerry, Bill Clinton and Pope Francis, to name a few.
DiCaprio also spoke to dozens of scientists and hopes that their message is strong enough to sway those holding to the idea that climate change hasn't been proven.
"I think the media has improperly represented the fact that there still is an argument going on," DiCaprio said. "You have 97 percent of the scientific community saying that man is contributing to this issue and we have the ability to turn this all around."
The Revenant star left us with a call to action, saying, "It seems like such a complex issue and it seems beyond our control, but the truth is, we need to use our vote, we need to speak our voices through our vote and elect leaders who believe in the modern science of climate change, who believe in empirical truths, and if we don't do that, and lose our voice this election, ultimately we're not going to make a dent in this issue."
Before the Flood will air globally on National Geographic Channel on Oct. 30.