A tale of two superpowers
1926 CET: It's supposed to be about two degrees. It appears to have come down to two men.
As I write, US President Barack Obama and China's Prime Minister Wen Jiabao are locked in a room somewhere around this conference centre - a meeting that could answer the question of whether ther's a deal here.
They're deadlocked over a single sentence in the latest draft - the fourth - that leaders and their ministers have looked at today.
It says: "Mitigation actions taken by Non Annex Parties will be subject to their domestic measurement, reporting and verification..."
In language that suspicious members of the US Senate would use, this translates as: "We can't see what those dastardly Chinese are up to."
Yesterday, Hillary Clinton set out "transparency" as the key US demand. When the latest draft was presented, I'm told Mr Obama personally intervened and told everyone in the meeting this was unnacceptable.
In the corridors, a view is emerging that China doesn't really want a deal.
Four separate people on or close to national delegations have told me this; though as things stand, no-one will go on the record.
It's said that at the top levels of government, economic development now followed by fast climate protection when the impacts begin to hit is the preferred strategy.
One analyst said it's a "550 country" - meaning it has always privately favoured a target of keeping greenhouse gas concentrations in the atmosphere below 550 part per million (550ppm) rather than the 450ppm that most favour.
There is blame, too, for the US, which despite its claims of "global leadership" has offered nothing new here.
As to everyone else? Well, they won't all like the draft agreement, and delegations are trying to get certain bits changed even now.
The question they all have to judge is whether they take it, or take the chance of achieving something better next time around - indeed, whether there will be a next time around.
If the analysis that the US and China hold the key, then there are two outcomes from this summit. One sees Mr Wen and Mr Obama joining hands in mutual glory; the other sees them heading off to their respective capitals in their respective limousines, with each saying that they tried but the other side just wouldn't play ball.