The film 'An Inconvenient Truth', made by former US Vice-President, Al Gore, is about:

Explanation

It's climate change.

Interestingly I've seen writings from climate activists who say that the film provides clear evidence that human-made climate change will be disastrous for the human race; and I've seen writings from climate-change deniers saying that if things were that bad we'd have become extinct a while ago. You decide.