The iconography of climate disaster has now acquired an almost religious inflexibility. Just as the image of the Crucifixion is inseparable from Christian devotions, the contemplation of planetary ruin is invariably attended by a set of familiar visual cliches. You'll get glaciers slumping into the sea, polar bears looking glum, chimney stacks belching smoke, and a passenger jet shimmying into the sky through a quiver of exhaust fumes. All were present, at one time or another, in Earth: the Climate Wars, which you might take as a marker of its confessional orthodoxy. But it began with a dummy punch that seemed to suggest quite the opposite.

In the 1970s the world seemed to be falling apart. From acid rain to overpopulation, ecological concerns were at the fore. And it was at this time that climate change first became a hot political issue. But it wasn't global warming that frightened scientists, it was the complete opposite; a new ice age.Dr Iain Stewart traces the history of climate change from its very beginning and examines just how the scientific community managed to get it so very wrong back in the Seventies. Along the way he 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.He shows how - 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. Because in the 1990s global warming would be transformed into one of the biggest scientific controversies of our age.

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.

Having explained the science behind global warming, and addressed the arguments of the climate change sceptics earlier in the series, in this third and final part Dr Iain Stewart looks 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.