The world of the armoured creatures is equally fascinating and bizarre. Galapagos giant tortoises solve the problem of making love in a suit of armour; a heated sea turtle orgy leaves females in mortal danger and we witness the explosive arrival of a baby pig-nosed turtle. Giant salt-water crocodiles crowd a flooded river-run to fish for mullet and a caiman leads her brood in a touching trek to a communal crèche.

Dr Iain Stewart investigates the counter-attack that was launched by the global warming sceptics in the 1990s. At the start of the 1990s it seemed the world was united. At the Rio Earth summit the world signed up to a programme of action to start tackling climate change. Even George Bush was there. But the consensus didn't last.
Iain examines the scientific arguments that developed as the global warming sceptics took on the climate change consensus. The sceptics attacked almost everything that scientists held to be true. They argued that the planet wasn't warming up, that even if it was it was nothing unusual, and certainly whatever was happening to the climate was nothing to do with human emissions of greenhouse gases. Iain interviews some of the key global warming sceptics, and discovers how their positions have changed over time.

Dr Janina Ramirez shows how medieval manuscripts gave power to the king and united the kingdom in an age of plague, warfare and rebellion, discovers that Edward III used the manuscripts he read as a boy to prepare him for his great victory at the battle of Crecy and reveals how a vigorous new national identity bloomed during the 100 Years War with France. In the British Library's Royal Manuscripts collection Dr Ramirez finds out that magnificent manuscripts like the Bedford Hours, taken as war booty from the French royal family, were adapted for the education of English princes. She also explores how knowledge spread through a new form of book - the encyclopaedia.

Having explained the science behind global warming, and addressed the arguments of the climate change sceptics earlier in the series, Dr Iain Stewart concludes the series by looking at the biggest challenge now facing climate scientists - Just how can they predict exactly what changes global warming will bring?
It's a journey that takes him from early attempts to model the climate system with dishpans, to supercomputers, and to the frontline of climate research today: Greenland. Most worryingly he discovers that scientists are becoming increasingly concerned that their models are actually underestimating the speed of changes already underway.

Every year grizzly bear families in North America depend for their survival on a spectacular natural event: the return of hundreds of millions of salmon from the Pacific Ocean to the mountain streams where they were born. The salmon travel thousands of miles to spawn and then die. The great run not only provides food for bears, but for killer whales, wolves, bald eagles, and even the forest itself. The question is: will the salmon return in time to keep hungry bears alive?
A mother grizzly and her cubs emerge from their den high in snowy Alaskan mountains. Filming from the air the team capture a TV first, following the bears as they negotiate a near vertical slope on their journey to the coast where they await the return of the salmon. Meanwhile, the salmon are making their way to the to river mouths where they must swim upstream and against the current. The programme reveals how they tackle the torrents and leap over waterfalls, a feat equivalent to a human jumping over a house. Dozens of hungry bears eagerly await the salmon that make it up river. In another TV first, underwater cameras record the ingenuity and fancy footwork they use to collect dead salmon from the bottom of deep pools.

Each year more than one million wildebeest and zebra invade the Serengeti grasslands, making it a paradise for the predators that live there. But what happens when the herds move off again? We follow the moving story of one lion family's struggle to survive until the return of the great migration. Nature's Great Events tells the story of the epic trek of herds that follow the rains to fresh pastures, and the tale of the predators they leave behind.
The crew captures the desperate plight of a single pride of lions, revealing a different side to the Serengeti. Rather than being a predators' paradise, it is a land in constant change, with wildebeest following the rains and leaving the lions to tough it out. The Ntudu pride has seven cubs, and is already suffering as the wildebeest leave to find fresh pastures. The four pride females struggle to find enough food for their hungry offspring. As weeks turn to months, the pride members become more emaciated and frailer, and the number of cubs dwindles to just two. As the herds begin to return, the plains reveal one final secret. For the first time since 1967 the Serengeti's only active volcano, Ol Doinyo Lengai, begins to billow ash and smoke. Filmed from the air, the team captures the exciting action. Fertilised by the volcanic ash over millions of years, these short grass plains are among the most productive grasslands in the world. After months of hardship, the pride's tragic story, through sickness, drought and fire, is over as the herds return, providing plentiful food.