Foreign and environment ministers and other high-level officials from 45 countries are set to gather in Paris Monday seeking to re-energise climate talks mired in technical details and political squabbling.
Just four months ahead of a UN conference in the French capital tasked with producing a historic climate pact, US scientists this week said 2014 was a record year for sea level rise, land temperatures, and the greenhouse gases that drive dangerous global warming.
But overwhelming consensus on the urgency of the problem has not translated into significant progress on united action to prevent the planet from overheating.
"The negotiations have not, strictly speaking, begun yet," Laurence Tubiana, France's chief climate negotiator, told journalists this week.
Ministers meeting on Monday and Tuesday "have to take ownership of the content of the negotiation, otherwise their negotiators will not really be able to engage on the key political issues," she said.
The political discussions will be followed in Bonn at the end of August with technical negotiations on the content of a draft agreement, with another ministers' gathering slated for September.
The 32 foreign and environment ministers and 13 senior negotiators in Paris, working under the guidance of France's chief diplomat Laurent Fabius, have their work cut out for them.
A draft agreement emerging from earlier rounds is little more than an exhaustive laundry list of problems and options, and is too unwieldy, Tubiana said.
The 195-nation UN Framework Convention on Climate Change (UNFCCC) has embraced a goal of limiting average global warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.
Scientists say disastrous climate change can be avoided at this threshold, but warn the planet is on target for double that, or more.
Small island nations and poor countries in Africa and Asia, which will be hardest hit by climate-change effects, say 2C is not ambitious enough, and favour a 1.5 C target.
"As a people and a nation, our very survival is absolutely threatened by the effects of climate change," Tony De Brum, foreign minister of the Marshall Islands, told AFP ahead of the meeting.
Projected sea-level rise and enhanced storm surges, even under optimistic emissions scenarios, may force the inhabitants of some island nations to relocate before the end of the century.
The Paris agreement will be supported by a roster of national emissions-curbing pledges. Many parties—including China, the United States and the European Union—have already submitted their plans.
"But there is no guarantee that when you combine the pledges they will collectively be consistent with the 2 C objective," Tubiana pointed out.
Hence the need for a mechanism to ensure pledges add up, and a review process to monitor adherence, she said. Both issues remain highly contentious.
An internal briefing document identifies seven major sticking points, and urges diplomats to focus on two in particular, "ambition" and "differentiation" .
In the jargon of the climate talks, ambition refers to the level of emissions cuts needed, and differentiation is about sharing out responsibility for action.
Poor nations say the West, which has polluted more for longer, should carry more of the burden for emissions cuts, but the US and other rich countries insist on equal treatment and point the finger to emerging economies like China and India now among the top emitters.
The question of money is another Gordian Knot.
Poor countries insist that rich nations must show how they intend to keep a promise of boosting climate finance to $100 billion (92 billion euros) per year from 2020.
Explore further: Pace of climate talks far too slow: UN chief