Six true stories indicate that our time to reverse the impact of climate change may be running out.

Having bloodied the noses of McDonald's and the British judicial system with her first feature documentary, McLibel, Franny Armstrong moves on to bigger things in The Age of Stupid, an engaging and urgent attempt to make us all see sense about climate change.

The film is a wake-up call with an elegiac tone — not quite hectoring but pressing. It goes well beyond the arguments about science that Al Gore tried to straighten out in An lnconvenient Truth. This is about human nature, greed and personal responsibility. It aims to scare and galvanise — and it's pretty good at both.

It's a documentary but with a clever fictional framing device. Pete Postlethwaite plays a man looking back from 2055 atop a great tower in the Arctic Circle. He's the archivist, looking after a huge storage facility containing the combined knowledge and cultural resources of the human race, gathered there before it all went pear-shaped.

He rides around on a bicycle, like the last man on a space station. The tower is hundreds of metres above ground. There's no ice because the polar cap has melted. A quick fantasy montage shows what's left of the world: London is largely under water; Vegas is once again reclaimed by the desert; Sydney is burning and the Taj Mahal is a ruin.

The archivist sits down at a screen and presses "record". He is taping a final message to the future about what happened but it is shot as though he is talking directly to us through a two-way screen. As he talks, he reviews pieces of actuality from back "when we could have saved ourselves".

"What state of mind were we in," he asks, "to face extinction and simply shrug it off?"

The footage he chooses takes us into six stories, filmed in the present day.

Armstrong initially set out to make a film about the politics of oil and climate change. The film that finally evolved came about after what she says was a disastrous rough-cut screening for friends and investors in London. No one got all the subtle links between the six true stories. Postlethwaite gives the film much greater unity as a kind of digital shaman, revealing how we destroyed ourselves in the early 21st century. One person calls the last century "the age of ignorance, the age of stupid".

This is Alvin DuVernay, who, until recently, worked for Shell, helping them find more offshore oil. DuVernay lives in New Orleans, where he is well known because he personally rescued more than 100 people from rising waters after Hurricane Katrina. DuVernay's house is gone but he argues persuasively that the search for oil must go on.

In Nigeria, a young woman called Layefa Malemi shows us the poverty of life in an oil-rich country, from which Shell derives a decent share of its profits. She wants to study medicine; she also wants to be rich enough "to live like an American". In the meantime, she catches fish near an oil refinery. She washes them in laundry powder to get the oil off.

In France, 82-year-old mountain guide Fernand Pareau takes an English family for a hike on the Mont Blanc glacier, which has receded 150 metres since 1955. Pareau grows his own potatoes as trucks whizz through the Mont Blanc tunnel taking French potatoes for processing in Italy. They will return by the same route as potato mash for French consumers.

The English family is from Cornwall, where Piers Guy and his wife have built a largely self-sustaining farm. Piers also builds wind turbines to replace more costly forms of energy, except he faces opposition at every site. People who profess a strong commitment to fighting global warming do not want a wind turbine destroying their views.

In India, budding tycoon Jeh Wadia works towards his dream of establishing a low-cost airline that every Indian can afford. He believes his purpose is to eradicate his country's poverty through air travel. Why should rich Westerners be the only ones who can afford to fly?

The film glides through many highly contestable arguments, some of which are just a bit silly. Postlethwaite asks why we didn't save ourselves when we had the chance. "Is the answer that at some level, we didn't think we were worth saving?" That sounds like a glib line from the pulpit rather than a useful argument.

Armstrong has more success showing the connections between disparate problems. She's trying to come up with a theory of everything, linking consumerism, oil, the aspirations of the Third World and the First World's failure to take responsibility for its energy use, all against a ticking clock.

It's not about the science any more. We are beyond that, according to this film. We don't have years to decide to do something radical — more like months.