This documentary is streaming for free on all platforms on October 30, the day it premieres on the National Geographic Channel. See clips and more here.

Ten years ago the Oscar-winning actor Leonardo DiCaprio sat down with Al Gore and learned about the scary and imminent dangers of climate change. This sober-minded young man is serious about understanding the global problem and wants to shed light on what can be done to save the planet from the greed, the self-absorption, and the many missteps which have harmed humanity and the good Earth.

Before the Flood is a feature-length documentary presented and produced by DiCaprio, who has been appointed by Ban Ki-Moon as the United Nations messenger of peace on climate change. With the energy of his youth and ample financial resources and contacts, he has put together the most comprehensive film on the subject since An Inconvenient Truth.

DiCaprio chronicles his three-year excursion around the world seeking solutions to the problem which is unfolding more swiftly than many scientists had predicted. He says that in the back of his mind is the "nightmarish" painting which hung over his bed as a child. It was Hieronymus Bosch's "Garden of Earthly Delights" with its depiction of a place that has been dominated and brutalized by human beings before the Flood.

In Canada and Greenland, DiCaprio witnesses the devastating impact of the addiction to fossil fuel in the United States and other nations. Years ago, activists for the environment believed that small individual acts like changing the type of light bulbs used in our homes and offices could begin to turn things around. DiCaprio responds: "It's pretty clear that we are way beyond that now. Things have taken a massive turn for the worst."

What does that mean? Jason Box, a geology professor, believes that if the climate remains at the temperature that it's been in the last decade, Greenland will be completely submerged beneath water. DiCaprio speaks to marine biologist Jeremy Jackson who predicts that our actions will kill off coral reefs all over the world. In Florida and the Pacific islands, measures are being taken right now to protect people who live by the ocean and face massive floods. In one of the cogent moments in the documentary, Indian environmental activist Sunita Narain challenges DiCaprio's America-centric view in asking India to make sacrifices that the citizens of the United States have not made.

DiCaprio is taken aback when flying over Indonesia and seeing the drastic deforestation efforts being mounted by palm oil plantations in order to create cash cows for big companies. Gidon Eshel, a professor of environmental science and physics at Bard College, suggests that all travelers on Earth should realize that beef is about 10 times more damaging to the environment than any other form of livestock. He suggests that a gracious nod to the environment can be made by simply switching to chicken. Other solutions which are discussed include a carbon tax and "gigafactories." DiCaprio hopes that others will catch the enthusiasm voiced by President Obama during their walking interview for the film.