Introduce Frozen Worlds.

Frozen Worlds is the opening episode and it’s a journey from the bottom to the top of the planet. Along the way we're revealing the incredible frozen worlds that exist all across it.

We start in Antarctica, the most hostile of all of them. Here we film two stories. The first story is about emperor penguin chicks fledging. Left by their parents they're making their journey alone to the ice edge to get to the ocean and they have to go through a number of different challenges. It's a classic, heroic tale featuring these individuals that seem to be quite ill equipped as, for instance, they can't walk very far and they can't climb things. It turns out to be a bit of a miracle that they get there in the end but, once they get to the water, you see that actually this is where they're meant to be and, off they go, into the Antarctic Ocean.

Then we do our first story about killer whales ‘wave-washing’. There’s a second story about this behaviour later in the series. This is an incredible piece of behaviour where the killer whales come together as a family. Because the seals are hauled up on pieces of ice, they worked out a hunting strategy where they create a wave and wash the seal off the ice. It’s one of the most sophisticated hunting techniques there is. They calculate the number of seals there are, the size of the wave depending on how far away they are, the number of whales needed to create it, etc. Not dissimilar to elephants, the knowledge of how to hunt and the best places to hunt is stored in the matriarch who runs the family and can get to over 100 years old. She’s utterly crucial to the whole pod’s survival. We follow her and see how the others must learn from her.

Then we journey to the mountains in Central Asia, home to the Himalaya, the biggest frozen world away from the poles. The Karakoram range is in the far west of the Himalaya and has the highest concentration of snow and ice anywhere outside the poles. We've done an aerial shoot there where we go big on the huge mountain glaciers.

That leads us to look in the penumbra of the Himalaya where there are other, even more surprising, frozen worlds like a desert that's covered in snow. Next to the desert is the steppe, a big grassland where we find our next character, the Pallas’s cat. It's the fluffiest cat in the world and we have a comedy sequence about it trying to catch gerbils and messing it up. Its paws get so cold on the snow it has to wave them to get the blood circulating back again. This makes its presence known before it can actually pounce.

We continue further north to our next frozen world which is a story about Siberian tigers, incredibly rare and hard to film, that go looking for hibernating black bears. We rigged caves and pathways and we can see the tigers entering the caves to look for prey. That hasn’t been filmed before.

In the tundra we have a quite intense and gruesome story with a brown bear attacking a herd of muskox and targeting calves.

Then we travel upwards to the Arctic Ocean for a bit of light relief as we meet the hooded seal. Its way of fending off other males and appealing to females is blowing a red balloon, the size of its head, out of its nose. We film a juvenile male who's not having any luck, though he's trying very hard with the females.

And then finally we look at how Greenland, the world’s largest island in the Arctic Ocean, is being affected by climate change. This culminates in a big calving event, with big bits of ice falling off the front of the ice sheet. We look at how this is affecting the Arctic’s wildlife, specifically a family of polar bears, and how hunting is getting harder and harder for them.

What of all those stories was the hardest to film?

The camera operator who filmed the muskox story had to camp out on the Arctic in blizzard conditions. He towed behind him a garden shed on his Skidoo and he lived in that. Not only did he have to deal with subzero temperatures and high winds, but also there was a very hungry brown bear circling around him at the same time. So that was definitely one of the most extreme places anyone had to work. Personally, I did the aerial filming in the Karakoram. Not only was it cold, but we were above 7000 metres, filming some of the highest aerials ever filmed. The oxygen level was so low there that it's probably the sickest I've ever felt. In addition, being in Kashmir, you have to work with the Pakistan military. We were using their helicopters so we had to divert to pick up casualties from the frontline and land on glaciers, 6500 metres up. They are incredible pilots but they push to the extreme what's possible in flying a helicopter at high altitude.

What new technologies did you employ?

Drones have played a big role. ‘Wave-washing’ behaviour was actually captured in the original Frozen Planet but without that aerial perspective. This is about as remote as you can be in the Antarctic Peninsula: it would be hard to get a helicopter out there and a helicopter could disturb their behaviour. Drones allow you to see how those whales are coordinating. It means we're able to bring new revelations. We've also had drones flying in new ways.

In order to capture how these environments are changing we've also undertaken a massive time lapse project across the production. We’ve been running time lapses from satellites in space to show the movement of ice in Greenland. And we've been putting cameras up on high altitude glaciers.

How will Frozen Worlds challenge people’s ideas of the frozen planet?

Our hope is that we can show people that the diversity of frozen habitats is huge. There's a frozen habitat on every continent on Earth and we literally cover all the continents in this series. Hopefully people realise that they're much closer to these places than they might think and that there's a greater diversity of life and animals that relies on and lives in these worlds. As a side, hopefully, that will encourage people to keep protecting them. Because climate change doesn't just affect the poles, it also affects all these other frozen worlds around the world. They're all at risk.

Alex Lanchester Biography

Alex is the producer of both the Frozen Worlds & Frozen Peaks episodes of Frozen Planet II. In the 14 years that he has been working for the BBC’s Natural History Unit his passion to deliver ground-breaking stories has taken him from the sewers of Bangkok (Wild Cities) to the high peaks of the Himalaya (Mountains: Life at the Extreme). Alex has worked extensively at high altitude and specialises in filming in extreme environments, such as the Arctic Tundra (Alaska: Earths Frozen Kingdom) and the remote jungles of Papua New Guinea (Attenborough's Paradise Birds).

For Frozen Planet II Alex travelled to Pakistan, to capture the splendour of the remote Karakorum mountains, deep into Greenland’s ice sheet to document the seismic changes occurring there due to climate change and to the far east of Russia to film the illusive Siberian Tiger.