He's shown us polar bears mating, devious Adélie penguins and elephant seals slugging it out on a rocky beach. We've watched the beauty of a polar spring melt into summer, then shivered as the seasons slow and freeze into autumn and winter once more. His voice has soundtracked wolves hunting in the tundra, emperor penguins huddled on Antarctic shores and even the bizarre habits of the Arctic's woolly bear caterpillar, which lives through 14 winters of suspended animation before becoming a moth. Along the way there has been plenty of the sort of high-definition natural history drama that we've come to expect. But tonight, the BBC's latest David Attenborough-narrated epic, Frozen Planet, draws to a close with a depressingly familiar message: it's a fragile world out there, the polar regions are warming and this has profound implications for all life on Earth.
We meet in Kew, a short hop from Attenborough's Richmond home, with the colours of autumn all around us. The reds and golds of the leaves suggest nature's reassuring rhythm; on the face of it, all seems well in the world.
However, the 85-year-old naturalist and broadcaster is conscious that our understanding of climate change has altered dramatically since his last major series on the poles, Life in the Freezer, which was broadcast in 1993.
"Global warming wasn't recognised when I did Life in the Freezer," says Attenborough. "We now know not only that it happens, but what the consequences are of it happening.
"It makes it much more urgent and much more meaningful than it was. In Life in the Freezer you felt that it was a bit of a jaunt, going off and seeing a part of the world you don't normally see. You now know that what has happened there is going to be of crucial importance right here."
Do programmes such as Frozen Planet help? Attenborough certainly thinks so. "People should have an impression of what it is like there even if they don't see it themselves. United Nations figures recently said over 50 per cent of the human population of the world is urbanised to some extent, which means that every other man, woman or child is out of touch with nature to some degree. Does that matter? Yes, it matters profoundly, because we are dependent on the natural world for the air we breathe and all the rest of it and it's in danger as a consequence of what we do.
"If you're going to ask people to accept that some of their hard-earned money that goes into taxes is going to be spent, not on old-age pensions and not on the army, but on something which will not produce a return for another generation, then they've got to understand why that's important. Television programmes are a way in which they can get a feel for what's happening in the world, for which they are responsible."
Much of Frozen Planet is about facing extreme conditions. Did he enjoy the cold as a child?
"I lived in Leicester and I vividly remember coming home and telling my parents that there was a field that had been flooded by the River Soar. There were people skating on it and you could go there for sixpence – and could I have a pair of skates? Of course, you get sodden and you get wet and you fall over, but you can't wait to get back again in the morning." Proficiency at winter sports, however, eluded him. "The war broke out in 1939, when I was 13 and those are the years when you would have started skiing," he says.
"In 1945 the war was over but I was in the services [in the Navy] and I didn't have time to learn how to ski. Then I was earning a living [initially in the 'Talks Department' of the BBC] and I hadn't got any money to go for a Continental ski holiday. I missed out on skiing, but I can't complain."
The changing seasons are important to Attenborough. "If I lived in the tropics it would be what I missed most about Britain," he says. "I like change. The breathtaking change of an English spring is irreplaceable; it's so exciting. What I missed most in those years that I used to go away [filming] for three or four months a year was spring."
One hundred years ago, Captain Robert Falcon Scott was embarking on his doomed Terra Nova Expedition to the South Pole, an endeavour about which Attenborough pays moving tribute in Frozen Planet: "They had no map to guide them and no idea of what lay ahead. It was a journey of extraordinary suffering." Does he, I wonder, feel any sense of continuity with the polar explorers?
"Well, I knew [Scott's son] Peter Scott very well. When I was the controller of BBC2 we discovered that the man [on the search party] who pulled aside the tent in which the bodies lay was still alive. His name was Tryggve Gran and he was Norwegian. I said we should do a programme about what happened after they died, which we did, but I realised when I saw the finished programme that we couldn't allow Peter Scott to see this account of the death of his father at the same time as millions of other people. So I invited him to BBC Television Centre with others who had Antarctic connections. We had dinner and then I showed the film. And when Tryggve Gran was explaining how he saw the bodies lying there I turned around and saw Peter with tears running down his cheek. He was three when his father died."
The events of 1911-12 in Antarctica still resonate with Attenborough: "The first time I went into Scott's hut, I was in the advance party and the helicopter went back to pick up the cameraman. When I was by myself, I opened the door, walked in – and of course it's all dark, so I was spraying this torch around and the beam was falling on Cadbury's chocolate and a horse's harness and an anorak hanging on a hook and a bunk with blankets on. And there was the smell of tar and decay and age. I found it quite creepy. I suddenly felt: 'I've got to get out of here.'"
Do his programmes encourage us to explore more? "Some people want to, some people don't want to; some people can afford it and some people can't. People react in whatever way they wish. Quite a lot of people would prefer not to go and sit at the South Pole and are perfectly happy to see it on the television – and why not?"
Next year, a trilogy of programmes is planned to coincide with Attenborough's 60th year in broadcasting. Is there anywhere he wouldn't go?
"Just now," he says, "I don't particularly want to go to the Moon. There's nothing there except bloody ash!" It seems that even David Attenborough has his limits.
'Frozen Planet' is available now on BBC DVD and Blu-ray.'Frozen Planet' by Alastair Fothergill and Vanessa Berlowitz, published by BBC Books, e-book £9.99
'It's impossible not to be entertained by them. Although for Mark Smith, who filmed them for four months in a tent, I dare say the joke ran a bit thin.'
'They're spy-hopping. They can see what's on land; there might be a seal there, after all – or a human being with a camera. They look entertaining enough, but they are huge.'
'Sometimes you've got plenty of time. There's nothing else in the shot and you can wait to get it right. But other times it's taken you all day; there's five of you; you may be having a rotten time and you come to a point where this is only going to happen once – and you'd better get it right, boy.'
'If you see one through your binoculars you are quite relieved, because he's hunting you and he can run faster then you can.'
The Dry Valleys
'There are stones that lie there, being sculpted by the wind and they haven't moved for a thousand years. If you turn them over you see the unpolished rough side – and you feel rather guilty and think you'd better put it back. Who are you to turn that stone over?'