Franny Armstrong’s docudrama, a well-made warning about our world’s greed and stupidity independently financed by more than 200 small investors, opens with Pete Postlethwaite as an old man living apparently alone in the ecologically devastated world of 2055. He is sitting at his still-working computer in the Arctic looking at his own assemblage of archive footage. Why, he asks, didn’t we stop climate change when we had the chance?

Postlethwaite recently had a stab at Lear and appears a little like Shakespeare’s tragic king as he wags his figure at us disconsolately. Sometimes it feels like he’s lecturing us, as if we were a lot of naughty children. But the documentary footage is persuasive enough to suggest that we probably deserve it.

It includes a palaeontogolist who, after helping Shell find more and more oil, saved more than 100 people from Hurricane Katrina; an entrepreneur who successfully starts a low-cost airline in India; a poverty-stricken Nigerian who fishes in the oil-infested waters of a corrupt society; a wind farm developer who fails in his fight against nimby Cornish protesters; and an 82-year-old French mountain guide who has witnessed his beloved Alpine glaciers melt by 150 metres.

All this provides incontrovertible evidence that the old man trawling through his archive has a right to be depressed. But when all is said and done we get the feeling that we’ve seen it all before. Al Gore’s An Inconvenient Truth also lectured us but, by virtue of being the first such film, had more shock value.