Bleary-eyed ministers began a final push on Friday to lay the groundwork at UN climate talks in Warsaw for a new, global deal to stave off planetary disaster.
Negotiators had worked late into the night to try and find some common ground on who needs to do what to meet the UN-backed goal of curbing average global warming to 2.0 degrees Celsius (3.6 Fahrenheit) over pre-industrial levels.
On Wednesday, environment and developmental observer groups walked out, saying the annual round of talks had produced little more than hot air since opening on November 11, and was "on track to deliver virtually nothing".
The conference is scheduled to close by 1700 GMT on Friday, but many are bracing themselves for another late night's work.
Gathering more than 190 nations, the negotiations are meant to pave the way to a pact by the end of 2015 to limit global warming by taming carbon gases emitted by burning coal, oil and gas.
On current emissions trends, scientists warn the Earth could face warming of 4.0 C or higher—a recipe for catastrophic storms, droughts, floods and land-gobbling sea-level rise.
But developed and developing nations are at loggerheads over divvying up responsibility for cutting greenhouse-gas emissions.
Developing countries want wealthy nations to shoulder a bigger share of emissions cuts to make up for a long history of fossil-fuel combustion.
The West, however, insists that emerging economies must do their fair share. China is now the world's biggest emitter of CO2, with India in fourth place after the United States and Europe.
Another point of contention is money.
Developing nations are challenging wealthy countries to show how they intend to honour a 2009 pledge to muster up to $100 billion (74 billion euros) by 2020, up from $10 billion a year from 2010 to 2012.
Still struggling with an economic crisis, however, the developed world is wary of unveiling a detailed plan at this stage, or pledging new short-term figures.
The money crunch also lies at the heart of another issue bedevilling the talks: demands by developing countries for a mechanism to help them deal with future losses from climate impacts they say are too late to avoid.
Rich nations fear this would amount to signing a blank cheque for never-ending liability.
The conference did not have many measurable targets, but negotiators and observers had hoped for progress on some of the most contentious issues, and a roadmap for an historic climate deal in two years' time.
By Friday morning, with just over eight hours of scheduled negotiations to go, a draft text went so far as to "invite" parties to announce emissions curbing commitments "well in advance" of the Paris meeting where the pact is to be adopted in 2015.
Explore further: Deep divisions as climate talks enter final stretch