An Inconvenient Truth: A Global Warning (official site)
A documentary film by former U.S. Vice-President Al Gore
Directed by Davis Guggenheim

Film Critic Roger Ebert:

"In 39 years, I have never written these words in a movie review, but here they are: You owe it to yourself to see this film. If you do not, and you have grandchildren, you should explain to them why you decided not to."

From Wikipedia:

A documentary film, An Inconvenient Truth explores data and predictions regarding climate change, interspersed with personal events from the life of Al Gore. Through a Keynote presentation (dubbed "the slide show") that he has presented worldwide, Gore reviews the scientific evidence for global warming, discusses the politics and economics of global warming, and describes the consequences he believes global climate change will produce if the amount of human-generated greenhouse gases is not significantly reduced in the very near future. Gore argues that climate change is indeed an ethical issue and relates this understanding to events of his life.