The film will be unveiled in Leicester Square this weekend in a specially constructed solar-powered cinema. It will also be beamed by satellite to 65 other cinemas around the UK and is expected to be the largest ever official film premiere.
The film sees actor Pete Postlethwaite looking back on footage from 2008 from a future world ravaged by climate change. All profits from the film will go to climate campaign Not Stupid, which is supported by Friends of the Earth, Greenpeace, WWF and Stop Climate Change Chaos.
Unity will also handle PR for the Not Stupid campaign in the run-up to the UN Climate Summit in Copenhagen in December. The campaign aims to turn the film's viewers into climate activists.
Entertainment specialist Rogers & Cowan has been handling PR for the film in the run-up to the premiere.