Global warming, and how to combat it, has provoked intense debate, changed the way we see the planet and created headlines around the world. But when and how did scientists first discover global warming, why has it led to such furious debate? In this three-part series geologist Dr Iain Stewart presents a definitive guide to the history of climate change.
Battle Begins uncovers some of the great unsung heroes of climate change science, and introduces us to a secret organisation of American government scientists, known as Jason, who wrote the first official report on global warming as far back as 1979. By the late 1980s global warming had already become a serious political issue. It looked as if the world was uniting to take action. But it turned out to be a false dawn.

An Ice Age relic found in a mysterious cave is evidence of prehistoric humans' connection to the supernatural. Using cutting-edge tech, experts investigate this 40,000-year-old treasure to reveal why it was made and the long-lost myths it represents.
In the summer of 1939, a team of explorers unearthed hundred of mammoth ivory fragments within a cave in Germany. Due to the start of World War II, the explorers were forced to abandon their findings, and the fragments laid forgotten in a museum. Decades later, as archeologists began piecing the fragments together, an extraordinary artifact emerged -- a figure with both animal and human features, now known as the 'Lion man.'

Are rising temperatures driving Earth's ecosystems past a point of no return? We have promising technologies that put solutions within our grasp. Scientists are exploring solutions: from geoengineering to sucking carbon out of the air to cloud brightening, as means to cool the planet. Cutting-edge solutions and high-risk measures. But would they work? And what are the risks of engineering Earth's climate?

What sort of alien civilizations might exist in the vastness of space? Terra is the fictional world imagined in Episode 4, a planet nine billion years old, twice as old as Earth. Old enough that a truly advanced intelligence could evolve. It was once a fertile world, now it is barren. But life can still thrive here in artificial domes. Over time, they've evolved not to need their bodies. They exist only as neural tissue. They never age, they never die. They're monitored and maintained by robots.
If alien civilizations are statistically so likely, why haven't astronomers found any sign of them? Where is everyone? Every time we look at an individual star, that's like dropping a bucket in the ocean. We're going to have to look at a lot of stars and to search through a lot of data until we find the clue that leads us to another civilization.

Planets beyond our solar system are known to astronomers as exoplanets. They are at trillions of miles from Earth and yet, it might be possible to detect a faint signature of life in them. From the light of the stars they orbit that passes through the atmosphere of an exoplanet, it is possible to capture the chemical fingerprint of the elements in that atmosphere.
The fictional world Eden is orbiting not one star, but two. The light from its twin stars powers photosynthesis, pumping more oxygen into the atmosphere than in Earth, allowing life to thrive. Grazers are constantly alert to danger, because the canopy is home to predators perfectly evolved to live among the trees. In Episode 3, another topic are fungi and the role they could play on exoplanets. Ecologist Thomas Crowther talks about the role mycelial networks play in the Rothiemurchus forest in Scotland.

Most planets we know of are so hellish, it seems impossible that anything could live. But it's amazing where life can take hold in the Earth. Astrobiologists look for simple single-celled microbes known as extremophiles in places as Danakil Depression, known in Ethiopia as 'The Gateway to Hell.'
In Episode 2, the fictional world is Janus, a planet in such a close orbit than its rotation is locked by the star's gravity and it always shows the same face to its sun. On one side of the planet, it's always daytime, a searing desert. On the other side, it's forever night, a frozen shadowland. Squeezed between the two, a sliver of perpetual twilight. Freezing meltwater flows from the cold side, carving canyons through the landscape. Deep in these canyons lives an extraordinary five-legged creature.