The all-too-real prospect of climate catastrophe on a horizon of decades, not centuries, coupled with a rising tide of expectations, would seem to be powerful incentives to forge an agreement that is truly up to the task.
Science makes it clear that the laissez-faire alternative is a climate-addled future of mega-storms, drought, water wars and mass migration.
It is also a reminder that the window of opportunity for acting is barely ajar - if human emissions of heat-trapping greenhouse gases don't peak very soon and drop very swiftly, it may soon slam shut.
"Our concern is that we will end up with a lowest common denominator, where everybody just agrees on the least ambitious options," said Li Shuo of Greenpeace China.
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The last time the world tried to craft a "last chance" universal climate pact - in Copenhagen, in 2009 - it ended in tears, with more than 110 unhappy heads of state scrambling in overtime to piece together a three-page, face-saving "declaration" instead.
And yet, progress has been incremental and painfully slow.
Negotiators left the former East German capital yesterday after a week of closed-door meetings with very little to show and a draft agreement "not fit for a negotiation," in the words of the European Commission's top negotiator, Elina Bardram.
But it is unfair, analysts say, to place too much blame on rank-and-file diplomats, themselves deeply frustrated to have made so little headway with only five negotiating days left before the main event in Paris.
"You have a very tight brief coming here from your ministers and capitals that you can't go beyond," said Alden Meyer, a veteran climate analyst with the Union of Concerned Scientists.