There were tense discussions over consensus with the Russian delegation at the end of last year's meeting in Doha
Negotiators from around 190 countries are meeting in Warsaw to try to advance steps towards a global climate agreement.
Participants say there is a growing sense of realism about the scale of what can be achieved in any new deal.
But there are concerns that the process could become bogged down in procedural wrangling after Russia asked for a review of voting procedures.
The meeting comes amid new warnings about global levels of warming gases.
This will be the 19th annual Conference of the Parties (COP) to the UN Framework Convention on Climate Change (UNFCCC).
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It's a recognition that where the rubber really meets the road is at the domestic level, and the agreement needs to reflect that”
Elliot DiringerCentre for Climate and Energy Solutions
At the meeting in South Africa in 2011, delegates adopted what's termed the Durban Platform which stated that a new international agreement should be negotiated by 2015 and come into force by 2020.
Pragmatic approach
Now in Poland, negotiators are coming to terms with the emerging shape of that deal.
"There is a fair degree of convergence emerging about the character of a new agreement," said Elliot Diringer from the Centre for Energy and Climate Solutions, a long-time observer of the negotiations.
"This reflects a greater sense of realism among the parties about what can accomplished in this process."
Climate campaigners believe the recent IPCC report settles the science over global warming
The delegates have been scarred by the experience in Copenhagen in 2009, when ambitions for a comprehensive deal foundered, despite the intense efforts of President Obama, Prime Minister Gordon Brown and others.
What's emerging now is a looser agreement whereby countries set their own targets, but are subject to some form of review by other nations.
"The sort of model that's emerging for Paris, this acceptance of the notion that commitments will be self defined, it's a recognition that where the rubber really meets the road is at the domestic level, and the agreement needs to reflect that," said Elliot Diringer.
The meeting comes after a series of studies indicating the scale of the climate challenge. The fifth assessment report from the IPCCpublished in September suggested that without concerted political action the accepted 2C threshold to dangerous climate change would be passed sometime in the middle of this century.
According to the UNFCCC executive secretary Christiana Figueres, Warsaw is a pivotal moment to advance momentum towards a deal.
"We still have time and the means to limit warming to 2 degrees C. And the international process must push forward now to build the foundation for an ambitious universal climate agreement in 2015," she said.
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Stumbling blocks
There are several issues that delegates have been divided on that could stall or derail momentum. Here are three of the most important.
Loss and damage - A key issue for developing countries which are looking for some form of compensatory mechanism for future damages caused by climate change. Developed countries are willing to provide assistance but are reluctant to set up a legal framework. A decision is due in Warsaw.
Money - Finance is always a rumbling source of discontent and in Warsaw countries must clarify how they will meet the goal of providing $100bn in climate finance annually by 2020.
MRV - It stands for the measuring, reporting and verification of pledges to cut emissions. Delegates in Warsaw will have to make a decision on how developing countries will verify their undertakings.
But there are a number of difficulties on the road to Paris where the 2015 meeting will be held.
Russia has emerged as a potential problem for the process as they have tabled an amendment on decision-making at the COP.
The process works on the basis of consensus but the Russians believe their objections were overruled at the meeting in Doha last year.
"Decision-making in the UNFCCC process has suffered evident setbacks over the past few years," the Russian delegation wrote in a statement.
It goes on to state that the voting system within the meeting needs to be addressed to rebuild confidence.
Climate cliff hanger
The Russian concerns led to stalemate at a sub-meeting in June. There are worries that this might continue to hamper progress in Warsaw, where delegates will be keener than ever to avoid a breakdown.
"This has been haunting the process even before the Russians brought it up," said Norine Kennedy, who will be representing US business at the meeting.
"We've had a succession of COP cliff hangers and one or two countries always get rolled over in the effort to find consensus and last year that was Russia.
"The consensus question will have to be faced sooner or later and it's better they do this now than in Paris," she said.
Another key question is the shifting nature of development. Where once the UNFCCC was neatly divided into developing and developed nations, with the richer ones making all the cuts in emissions, there is now a greater push for every country to bear some of the load.
But not everyone is keen on this.
"I saw some comments from the Chinese side, saying they are going to insist on a common but differentiated responsibilities point, said Norine Kennedy.
"That will be a hard fought fight and it will lurk behind most of the interventions we will hear over the next couple of weeks."
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