The official line is that the Copenhagen climate summit will not - cannot - be a failure. Yet behind the scenes, diplomats and analysts are already quietly totting up the political cost if the outcome on Friday turns out to be a fiasco overseen by two-thirds of the world's leaders. "Some 120 leaders are coming to this conference.
They cannot go back home empty-handed without an agreement which meets what the people are expecting," Stavros Dimas, European commissioner for the environment, told AFP Wednesday. A vast amount of political capital has been invested in the two-year process leading up to Copenhagen.
UN chief Ban Ki-moon has staked his prestige on the outcome, and statements from presidents and prime ministers around the world reflect - at least rhetorically - the will of 194 nations for a glittering success. Yet the prospects for the 12-day marathon started to dim months ago, when it became clear that it would not yield a fully-fledged, ready-for-ratification treaty, which was what was billed in Bali, Indonesia, in 2007.
At best, Friday will deliver an ambitious strategy for taming greenhouse-gas emissions, which will be followed by further talks next year to fill in the details. The problem lies partly with the hideous complexity of a two-track negotiation process and hundreds of peripheral issues that encumber the UNFCCC (UN Framework Convention on Climate Change) process.
It's a Gordian knot whose strands are then pulled even tighter by the defence of national interests when what is really needed is sacrifice for the global common good. Late Tuesday, conference chair Connie Hedegaard starkly spelled out to ministers that the much-ballyhooed Bali Road Map could end in a dead end.
"Success is still within reach," she said, as she kicked off the so-called high level phase of the UN conference with ministers and, on Friday, heads of state and government. Yvo de Boer, who, as head of the UNFCCC has been shepherding climate negotiations for nearly a decade, warned of the cost. "There will be huge political fallout if we fail to reach an agreement this week," he told AFP at the weekend.
"Civil society cares deeply and will continue to press this issue. If there is no agreement here, leaders will go home and some of them will pay some political costs," agreed Elliot Diringer, vice president of the Pew Center on Global Climate Change in Washington.
In the United States, "grassroots organisations will make it clear that senators who persistently refuse to let the Senate vote will pay the coin of the political realm at the polls," said Carl Pope, head of the Sierra Club, referring to legislators opposing climate and energy bills in Congress.
Expectations for Copenhagen have been stoked by genuine public alarm at scientists' warnings over the looming threat of flood, drought and rising seas. In some countries - such as fire-hit California and drought-ravaged Australia - an extreme weather event has been seized upon as evidence that the climate system is already going haywire.
"We have a global movement on this issue," said Britain's climate minister, David Miliband. "For the first time at an environmental summit, you have human rights organisations, trade unions, the World Council of Churches," said Kumi Naidoo, head of Greenpeace International and the world-wide TckTckTck climate campaign.
When Naidoo spoke Saturday to a throng of at least 30,000 climate activists as they set out on a six-kilometre (four-mile) trek across Copenhagen, one line in particular was met with roaring approval. "We can't change the science, so we have to change the politics," he said, leaving time for the set-up line to sink in. But it is an open question as to whether failure at Copenhagen could become a political career-killer.
Politicians are still elected on the basis of defending national interests, as opposed to global ones. By this yardstick, a leader who sacrifices too much for the common good is likelier to be punished than someone who defends jobs and prosperity.