A humpback whale mother and calf embark on an epic journey from tropical coral paradises to storm ravaged polar seas. Newly discovered coral reefs in Indonesia reveal head-butting pygmy seahorses, flashing 'electric' clams and bands of sea kraits, 30-strong, which hunt in packs. Elsewhere plagues of sea urchins fell forests of giant kelp. Huge bull fur seals attack king penguins, who despite their weight disadvantage, put up a spirited defence.

Sir David Attenborough journeys to both Polar Regions to investigate what rising temperatures will mean for the people and wildlife that live there and for the rest of the planet. David starts out at the North Pole, standing on sea ice several metres thick, but which scientists predict could be Open Ocean within the next few decades. The Arctic has been warming at twice the global average, so David heads out with a Norwegian team to see what this means for polar bears. He comes face-to-face with a tranquilised female, and discovers that mothers and cubs are going hungry as the sea ice on which they hunt disappears. In Canada, Inuit hunters have seen with their own eyes what scientists have seen from space; the Arctic Ocean has lost 30% of its summer ice cover over the last 30 years. For some, the melting sea ice will allow access to trillions of dollars worth of oil, gas and minerals. For the rest of us, it means the planet will get warmer, as sea ice is important to reflect back the sun's energy. Next David travels to see what's happening to the ice on land: in Greenland, we follow intrepid ice scientists as they study giant waterfalls of meltwater, which are accelerating iceberg calving events, and ultimately leading to a rise in global sea level. Temperatures have also risen in the Antarctic - David returns to glaciers photographed by the Shackleton expedition and reveals a dramatic retreat over the past century. It's not just the ice that is changing - ice-loving adelie penguins are disappearing, and more temperate gentoo penguins are moving in. Finally, we see the first ever images of the largest recent natural event on our planet - the break up of the Wilkins Ice Shelf, an ice sheet the size of Jamaica, which shattered into hundreds of icebergs in 2009.

The Arctic and Antarctic experience the most extreme seasons on Earth. Time-lapse cameras watch a colony of emperor penguins, transforming them into a single organism. The film reveals new science about the dynamics of emperor penguin behaviour. In the north, unique aerial images show a polar bear swimming more than 100km. Diving for up to two minutes at a time. The exhausted polar bear later attacks a herd of walrus in a true clash of the Titans.

A dramatic journey along the coasts of South America, from the Falklands to the tropical Galapagos. The cold currents create rich fisheries, and support such diverse marine life as dolphins, killer whales, sea lions and albatross. But the most biquitous creatures are the penguins, which inhabit surprising locations - lush forest, arid desert and even equatorial areas.

The polar regions of our planet may seem beyond the reach of most of us, but they are not beyond our influence. We, unintentionally, are changing these frozen worlds, and these changes will not just affect the poles but the whole planet. On the unforgiving frontier of climate change, polar bears, walruses, seals and penguins find their icy Edens in peril.

As almost all animal inhabitants of Antarctica are forced to migrate north, the sea underneath the frozen ice still provides a home to many specially adapted fish whose cells are protected from freezing through an 'antifreeze' liquid. Many of them feed on the faeces of other animals. The most notable larger animal that does not migrate north is perhaps the Weddell Seal, which can be found as close as 1300 kilometres to the pole. Groups of seals tear holes into the ice to dive for food and come up to breathe. The females come back to the ice to give birth. This episode also describes primitive plant life such as lichen, which can still be found on the continent in winter, even in the extremely dry and permanently frozen valleys conditions under which dead animals can lie frozen for many centuries without decomposing. It details the life of the Emperor Penguin, 'the only birds to lay their eggs directly on ice'. While other animals retreat, Emperors migrate not just to the ice, but into the Antarctic continent. The females lay eggs which are incubated by the males under the harshest conditions on Earth (huddling closely together for warmth), while the females return to the sea.