By Tom Heap

BBC Panorama

Tom Heap puts the climate 'Wall of Certainty' to the experts Climate change is often presented in religious terms - believers versus deniers disputing the fate of mankind. In the last year it really felt as though the gods unleashed a plague of events to test the faith. Dodgy e-mails gave us "climate-gate", the shifting jetstream gave us a freezing winter, United Nations-backed climate scientists gave us crass errors of glacial proportions and Copenhagen gave us, well, virtually nothing. Those who never believed we were changing the weather shouted triumphantly, while many who did seemed confused. Friends asked: "What are the facts, where does the certainty lie?" A good question, and one that Panorama set out to answer. 'Wall of Certainty' Much of the science about climate change and global warming has been taken on trust, a belief that so many senior scientists could not be wrong. The revelations of "climate-gate" fractured that trust and probably many in the environment movement felt the same way. This story provided a good opportunity to look back at the basics of climate science. But how does one present uncertainty clearly? Journalism, not least programmes of authority like Panorama, likes to deal in definites. Our goal was to clear as much of the fog as possible, but in some areas of climate science delivering information as hard fact would be a lie and doubt, in some instances, is the truth. To help us illustrate this story, we borrowed a trick from the fossil-fuelled funride that is Top Gear. Where the boys have their "Cool Wall", used to judge where a car should sit on a sliding scale of cool, we at Panorama brought out our "Wall of Certainty". Our wall has a scale from "certain" to "no way" and we asked everyone from professors to punters to tell us where to stick the varying theories of climate science. We even made a miniature version to take to the US. There are two undeniable facts that underpin the science of climate change. Post-industrial age levels of carbon dioxide are notably higher First, carbon dioxide is a greenhouse gas - it traps more heat than air. We saw the lab and handled the apparatus where this discovery was made 150 years ago. Second, thanks to mankind's recent burning of coal, oil and gas, there is more CO2 in the earth's atmosphere, up from a pre-industrial level of 280 parts per million (ppm) to 379 ppm by 2005. This is like the world putting on a thicker jumper - it means we retain more heat. When asked directly, or pinned to the "Wall of Certainty", no one we spoke to in making the programme disputed these two facts. Ferocious debate In the sceptical corner of our wrestle for the truth on climate change we have John Christy, an atmospheric chemist from the University of Alabama in Huntsville, and Bjorn Lomborg, author of The Skeptical Environmentalist, who has just finished a film to counter Al Gore's An Inconvenient Truth. Both of these men agree that the world is warming and man is at least partly responsible. John Christy reckons our impact is minimal, while Bjorn Lomborg, to my surprise, agrees that man-made climate change would trigger bad weather events of greater severity - especially hurricanes. In the other corner, we have government science advisers, Bob Watson and Bob Ward, who campaign for policies to tackle global warming. The two sides start from a position of agreement on the basic science - surprising when you consider the ferocity of much of the public debate. Please turn on JavaScript. Media requires JavaScript to play. Splits emerge when you begin to forecast what will happen in the future and what we should do about it. Watson and Ward believe temperature rises could be above three degrees in the next century - closer to the upper end of the Intergovernmental Panel on Climate Change's predictions - Christy and Lomborg would go much lower. Put another way, while they all think change is coming, one side thinks it will be manageable, the other, catastrophic. But neither side can deliver copper-bottomed facts about the future. Absolute certainty, it seems, will not be there to guide us as we make tricky personal and political decisions on this issue. It is a question of risk. You do not expect to crash your car - but you have plenty of expensive safety features fitted just in case you do. Panorama: What's Up With the Weather? BBC One, Monday, 28 June at 2030BST and then available in the UK on the BBC iPlayer . Producer Mike Rudin discusses the programme at The Editors blog .



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