A threat to civilisation or a natural cycle in the life of planet earth? Although the scientific consensus is that man-made global warming is with us, there are still prominent deniers in the debate.
You must be a resident of Mars if the words “climate”, “change” and “Copenhagen” have yet to bore their way into your brain.
In fact if you are a Martian you may be wondering when exactly the stream of Earthling refugees, whose homes have been destroyed by floods, wildfires and giant hail stones, will start applying for residency. That is unless you are a sceptical alien who believes it is all part of a giant cycle.
Over the last decade the debate about climate change has snowballed.
No longer the preserve of environmental niche groups, the issue has been shunted into the mainstream.
From the Asian tsunami to Hurricane Katrina, a string of shocking natural disasters have brought home the potentially devastating realities of a world in which temperatures are rising.
Channel 4 News takes a look at what the campaigners and the sceptics have been saying.
Al Gore: Former US presidential candidate Al Gore is now more famous for his climate change film An Inconvenient Truth than his White House bid. The documentary brought the debate over carbon emissions to the mainstream, won him the Nobel Peace Prize, and has influenced US policymakers since its release in 2006.
Hadley’s scientists have worked on a variety of climate change reports, including the assessment report of the IPCC. Their climate projections were the basis for the Stern Review on the Economics of Climate Change.
Peter Cox: Professor of Climate System Dynamics at Exeter University, Peter Cox is one of 26 researchers behind The Copenhagen Diagnosis. The report concludes that global emissions must peak, then decline rapidly within 10 years, for the world to have a reasonable chance of avoiding the worst impacts of climate change.
He says: “We are like alcoholics who have got as far as admitting there is a problem. It is a start. Now we have got to start drying out – which means reducing our carbon output.”
Julia Slingo: Professor Slingo is chief scientist at the Met Office and Director of the Centre for Global Atmospheric Modelling at the University of Reading. She says “leaving the problem for the next generation to solve is folly”.
James Hansen: Nasa scientist James Hansen said, 21 years ago, he was “99 per cent sure global warming is upon us, most likely induced by humans”. In January 2009 he wrote an open letter to Barack Obama, urging the new president to take on board a series of detailed recommendations to halt climate change and its potentially devastating effects.
Andrew Derocher: Bioscientist Andrew Derocher is an expert on polar bears and teaches at Canada’s University of Alberta. “You don’t have to be a polar scientist to see that if you take away all the sea ice, you don’t have polar bears anymore.”
Voters in Brighton elected the UK’s first ever Green Party MP in a historic moment for the environmental movement.
After securing her win in Brighton Pavilion, Caroline Lucas
told supporters they had put “the politics of hope above the politics of fear.”
She added that the party had taken, for the first time, its “rightful place in our parliament.”
It has been a long but steady slog for the 49-year-old, from Greenham Common protests to the panelled rooms of Westminster.
Bjorn Lomborg: Political scientist Bjorn Lomborg wrote The Sceptical Environmentalist. Although he does not deny global warming, he insists: “Overall, the environment is in better shape than we might think“. He supports the argument in his book with over 2,900 footnotes.
Willie Soon and Sallie Balunias: Astrophysicists Willie Soon and Sallie Balunias have together argued that the 20th century was not the warmest century of the last 1,000 years and that human-induced warming does not exist.
William Gray: US hurricane forecaster William Gray, who is Emeritus Professor at Colorado State University, believes climate change is “a hoax”.
He has said: “I am convinced that in 15-20 years, we will look back on this period of global warming hysteria as we now look back on so many other popular, and trendy, scientific ideas.”
Lord Monckton: British politician Viscount Monckton of Brenchley, who served as an adviser to Margaret Thatcher in the 1980s, has attracted controversy by saying global warming is a less serious environmental problem than dog fouling.
He took legal action to stop Al Gore’s An Inconvenient Truth from becoming part of the syllabus in UK schools.
Amy Ridenour: Amy Ridenour is president of the National Center for Public Policy Research, a Washington DC conservative think-tank. She is a high-profile online climate change sceptic who believes claims about rising levels of carbon dioxide have been misleading.
Glenn Beck: US “shock jock” Glenn Beck does not believe human activity is behind climate change and has said even if it is, “not much can be done about it”. He has also claimed: “The goal (of the climate change believers) is globalisation. The goal is global carbon tax. The goal is the United Nations running the world. That is the goal.”