The Weekend's TV: Earth: The Climate Wars, SUN, BBC2<br />Joanna Lumley In The Land Of The Northern Lights, SUN BBC1<br />Harry & Pau, FRI BBC1

It's not the end of the world, you know

The iconography of climate disaster has now acquired an almost religious inflexibility. Just as the image of the Crucifixion is inseparable from Christian devotions, the contemplation of planetary ruin is invariably attended by a set of familiar visual clichés. You'll get glaciers slumping into the sea, polar bears looking glum, chimney stacks belching smoke, and a passenger jet shimmying into the sky through a quiver of exhaust fumes. All were present, at one time or another, in Earth: the Climate Wars, which you might take as a marker of its confessional orthodoxy. But it began with a dummy punch that seemed to suggest quite the opposite. Back in 1972, Dr Iain Stewart told us, a group of eminent scientists had written to the American president with a prediction of imminent climactic disaster. "They warned that war and pestilence were on their way," he said, and instinctively you thought "Why didn't the idiots listen?" Then Stewart revealed that the feared threat was another ice age, an apocalyptic cool-down that had one contributor to a Horizon of the time putting our chances of getting past the millennium at just 1 or 2 per cent. "If scientists were so wrong back then, can we be sure they've got it right today?" Stewart asked.

Climate-change sceptics would ask this question to elicit the answer "We can't". But Stewart isn't in the denial camp. This rug-pulling opener served instead to lay a gloss of candour over his three-part précis of the current debate (a kind of promise that contradictory facts would not simply be swept under the carpet). It also underlined how far we have come in just 30 years. In a neat sequence, snapshots of Stewart himself, flicking backwards in time through first job, college larking, unwise Eighties haircuts and childhood holidays, underlined the fact that our dawning understanding of the scale of climate change can be contained in half a human lifetime. And then we got history in the other direction – in a useful summary of how carbon dioxide was first identified as the chief ecological villain – and then given an alibi by Ronald Reagan's favourite scientist.

The man who fingered carbon dioxide was Charles David Keeling, who first of all worked out how to accurately measure how much of it there is in a sample of air (who knew it was difficult?) and then dedicated his life to assembling the raw data. His results showed a steady increase. "The one undisputed piece of evidence in the global-warming debate", as Stewart described it. Stewart then followed it with a contention that many diehards would still argue with, including the current Republican candidate for the vice-presidency: that the human race is responsible for the rise in carbon dioxide. Back in the 1970s, very few scientists were quibbling with this, but then Ronald Reagan appointed a true-believing free-marketeer called William Nierenberg to look into the matter and he insisted that there wasn't anything to worry about, inaugurating more than 20 years of partisan statistic bandying. Oddly, in this ideological combat over potential apocalypse, Margaret Thatcher appeared as an unexpected heroine. "No generation has a freehold on this earth," she insisted. "All we have is a life tenancy with a full repairing lease." Earth: the Climate Wars looks as if it will offer a useful guide to the continuing row over what we should do about the central heating.

At least there was still plenty of ice left for Joanna Lumley in the Land of the Northern Lights, in which the actress finally made good on a childhood dream stirred up by a book called Ponny the Penguin, which featured an illustration of the aurora australis. The Arctic being a good deal more accessible than the Antarctic, Lumley headed north from Trondheim to fill up on snow and ice and – she hoped – the spectral veils of the northern lights. She looks very lovely in a fur coat (artificial, she carefully pointed out) and the variety of beardy Norwegians she met along the way appeared giddily pleased to have something to gaze at besides reindeer and dried cod. She eventually got her light show too, reduced to tears by skeins of emerald light flickering across the sky. "I can't believe I'm seeing this," she said. I couldn't quite either, a little suspicious about how you capture such an evanescent phenomena when your presenter is crisply in focus in the foreground. I hope the colourist didn't get carried away.

Harry & Paul, back for a new series, wasn't the unmixed pleasure it might have been, not because it wasn't good (there were some fine new sketches and very funny variations on the best of the old ones), but because it was hard to watch it without melancholy thoughts about its producer, Geoffrey Perkins, who died suddenly just a week before transmission. I met him a couple of times and he was as nice as he was talented, which is saying a lot.