Despite being riddled with conflicting proposals on most key points, the draft drawn up in four years of tough talks is the skeleton of what has been described as the most complex and consequential global accord ever attempted.
The stakes are high. Ministers from across the world will descend on Paris to try from Monday to transform the draft into an agreement that can rein in emissions that trap the Sun's heat, warming Earth's surface and oceans.
"In the words of Nelson Mandela, it always seems impossible until it is done," said South Africa's negotiator Nozipho Mxakato-Diseko after the 48-page draft accord was adopted to loud applause.
Scientists warn our planet will become increasingly hostile for mankind as it warms, with rising sea levels that will consume islands and populated coastal areas, as well as catastrophic storms and severe droughts.
However, cutting emissions requires a shift away from burning coal, oil and gas for energy, as well as from the destruction of carbon-storing rainforests -- costly exercises that powerful business interests are determined to press on with.
More than 50 personalities committed to combating climate change, from Sean Penn to US billionaire Michael Bloomberg and Chinese internet tycoon Jack Ma, gathered to inspire the UN conference at Le Bourget on the northern outskirts of Paris.
- Sean Penn says time to act -
"Perhaps this is the most exciting time in human history," Penn told a special event at the conference.
"Those illusions of having too many difficult choices have always created chaos. Now we live in a time where there are no choices. We have certainty. The days of dreams have given way to the days of doing."
Negotiators seem confident they can avert a repeat of a similar effort that failed spectacularly in the 2009 edition of the annual UN talks in Copenhagen, which aimed at a post-2012 deal but broke down, riven by recriminations between rich and poor nations.
It was two years after that failure, at Durban in 2011, that nations agreed to try again for a truly universal climate-saving pact.
Any deal emerging from Paris is likely to fall far short of what is needed to cap global warming at 2.0 degrees Celsius (3.6 degrees Fahrenheit) or below.
The key, analysts say, will be agreement on a review every five years atwhich nations' commitments may be strengthened, a so-called ratcheting-up mechanism.
There is still no agreement on fundamental issues: how fast and how far toslash greenhouse gas emissions; who shoulders most of the burden and, critically, who should pay.
- Sleep-deprived negotiators -
Poorer countries have demanded finance to pay for the costly shift to renewable technologies, as well as to cope with climate change.
At stake is hundreds of billions of dollars that would need to start flowing from rich to developing nations from 2020, under the planned Paris pact.
The biggest polluting nations, such as the United States and China, want to enshrine a target of 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-Industrial Revolution levels.
But weaker nations most at risk want a much tougher target of 1.5 C, which would require the global economy to transform away from fossil fuels and be fully reliant on renewables by 2050.
The Paris conference is scheduled to conclude on December 11.
But such deadlines are frequently ignored with weary, sleep-deprived negotiators often slogging through the night to get an accord.