Politicians insist that urgent and widespread action can yet prevent the worst of global warming but the cracks in that argument have been showing for some time.
Officially, UK efforts on climate change are in line with a global ambition to limit the temperature rise above pre-industrial levels to below 2C - a threshold the EU has defined as dangerous. But in 2006 David King, then the government's chief scientist, said a 3C rise was likely. Last summer, Bob Watson, the chief scientist to the environment department (Defra), told the Guardian the world needed to prepare for the possibility of a 4C rise. This autumn, Oxford University will hold a conference to discuss life in a 4C warmer world.
Hit with a double whammy of spiralling carbon emissions from the coal-fired boom in developing countries such as China and political stalemate, many climate scientists have become noticeably nervous in recent years. While technical papers in academic journals have tracked increasingly desperate predictions, most have put on a brave face in public. Likely failure to meet the 2C target, and the certainty of dreadful consequences, has been the worst-kept secret in climate science.
No longer. Today's Guardian poll of attendees at a climate conference last month in Copenhagen exposes the gulf between political rhetoric and scientific thinking. Of more than 250 experts surveyed, more than half said the 2C target could still be achieved but only 18 thought that it would be. By the end of the century, most thought average temperatures would rise by some 4C.
The figure is not plucked from their imaginations. The authoritative report from the Intergovernmental Panel on Climate Change (IPCC) in 2007 laid it out in simple terms. If carbon emissions continue to rise at present rates, then the IPCC's best guess is a 4C rise by 2100. The Guardian poll merely highlights a belief that the warning has simply failed to penetrate. As one said: "I think a full understanding of what must be done quickly, and the consequences of insufficient action, is lacking among the policy makers and the public." Another said: "Current government actions are playing into the hands of ... an electorate that doesn't quite understand how serious climate change is."
Survey respondents were promised anonymity. Many scientists are reluctant to admit publicly that the 2C target is unrealistic, and several warned that simply raising the subject was sensitive. One said: "Telling people that x% people think it can't be done would be a self-fulfilling prophecy. Great things can only be achieved by everyone believing it can be done ... Churchill didn't stand around saying most people think we will lose the war. He said we will fight it on the beaches."
Several scientists said the G20 summit in London, where climate change was barely considered, had convinced them the action required would not be taken. Simon Lewis, a climate researcher at the University of Leeds, said: "The summit shows that political leaders do not regard climate change as an urgent issue. They were tasked to re-configure the global economy and they chose to re-affirm the old model, and not move to a low-carbon economy as scientists have urged. The summit was more of an end-of-the-world order than a new world order."
Bob Doppelt, director of the climate leadership initiative at the University of Oregon, said: "One of the problems is that the issue is still being framed as a scientific and environmental issue. This is a major mistake. Climate change is just a symptom of dysfunctional social and economic practices and policies. It is a social and economic issue. The emphasis needs to shift away from the biophysical sciences now to the social sciences if we have any hope of solving this problem."
Others said it could take a series of extreme weather events similar to Hurricane Katrina and the 2003 European heatwave to force political action. One said a "9/11-type event" that could be traced to increased greenhouse gas emissions might break the political deadlock.