Earthquakes in London
Cottesloe Theatre, London SE1

Mike Bartlett's new play is pregnant - perhaps not with profound meaning, but with ambition, expectation, jokes and tension. Throughout, something terrible is about to happen - and that would be the end of the world by global warming. But more minor catastrophes are also imminent: a Lib Dem environment minister teeters on the verge of seduction by a cynical airline; a teenager flirts dangerously with her elder sister's husband; the sister is about to give birth to a baby she feels morally compelled not to have and ends up about to throw herself from Waterloo Bridge.

But I make it sound simple. Bartlett (My Child) and his director Rupert Goold (Enron) are in­tent on producing an evening that verges on chaos. An author's note to the text demands a crowded stage and scenes that jostle against each other: "The play is about excess and we should feel that." The designer Miriam Buether's solution is to present the action on a giant, S-shaped runway, around which lucky audience members sit, and less lucky ones stand. At either end of the auditorium, two window stages accommodate further scenes. The audience does a lot of head turning. At times during the three-plus hours, I wondered if I had hit upon the future of promenade theatre: the swivel chair.

The difficulty in dramatising a subject as big and general as climate change is not merely finding a way to stage it in a small space such as the Cottesloe, but working out a way to humanise it without trivialising it. The human soap aspect is achieved well enough. Jasmine, (Jessica Raine, working hard) is the delinquent teenager, running from the coming apocalypse into alcohol, drugs, sex and an unsuitable job that requires her to dance naked.

Lia Williams is the caustic Lib Dem minister Sarah, a banner waver and brick thrower in her day, whose marriage is collapsing, as well as her idealism. One of the best scenes is her evening out with Clive Hayward's airline executive, who promises her she can effect change from within the capitalist system. Hardest to fathom is the pregnant Freya, played by Anna Madeley, miserable about her forthcoming baby and, for some reason, feeling in need of guidance from the father she has not seen for 20 years.

Played with impeccable arrogance and cynicism by the excellent Bill Paterson, Robert is the play's masterstroke. He is, we are given to believe, the oracle - a research scientist who has sussed the end of the world. Yet he is a wicked man who has accepted bribes from the airlines in the past and proved incapable of loving his daughters. When he advises Freya to kill her unborn child on the grounds that the baby will never forgive her mother for being born ("Five billion people wiped from the face of the earth in a single lifetime . . . mass migration away from the equator, world wars, starvation, shooting on sight") is he speaking as a mercy-killer, or a sociopath?

Bartlett, however, is not content to let us wrestle with these human-scale mysteries. He drives his drama up towards the epic with one hand and levers it down to satire with the other. When Sarah is tempted by the airline boss, she is taken to a rooftop restaurant high above London: Jesus's mountain top. Pregnant Freya is accompanied on a long tramp round Hampstead Heath by an irritating schoolboy: Lear's fool. But undercutting these grand allusions are musical numbers, an encounter with a troupe of mindless Sloaney mothers (very funny) and Jess's topless dance routine, in which she half-dresses in the earth's depleting flora (gratuitous).

For a remarkable time, Bartlett and his performers manage to keep these ideas and styles together. I think I know when I guessed they wouldn't manage to do so to the end of the play. It was just before the interval, when Freya's foetus, revealed by a hospital scan, started crying to her mother for help. In the final hour, her fool turns out to be both her future child and her dead mother, and a cartoon is projected from the year 2525, celebrating an infant pro­phet who saves the planet.

We find ourselves in a weird sci-fi future where everyone dresses in white. By the time the lights go down, no one knows what is going on - which may, granted, be the truest commentary of all on the state of the planet. The great expectation that is finally dashed is that this will be the first great play of the new climatic era. Earthquakes in London miscarries.

“Earthquakes in London" runs until 22 September. Details: nationaltheatre.org.uk
Andrew Billen is a staff writer for the Times