The three-day gathering comes days after the UN issued a fresh warning that current carbon-cutting pledges go nowhere near far enough to prevent dangerous levels of global warming.
These national pledges will underpin the global deal being sought from a November 30-December 11 UN summit in the French capital.
That meeting, set to be opened by some 100 heads of state and government including US President Barack Obama, China's Xi Jinping and Narendra Modi of India, is meant to deliver the first-ever universal climate rescue pact.
They will base their discussions on a rough draft of a deal compiled by rank-and-file diplomats over years of tough negotiations in the UN climate forum.
The blueprint remains little more than a laundry list of often directly-opposing national options for dealing with the challenge at hand.
The last round of technical negotiations in Bonn in October saw squabbles along well-rehearsed fault lines of developed vs developing nations.
Developing countries insist rich ones should lead the way in slashing emissions because historically they have emitted more pollution.
But industrialised countries point the finger at emerging giants such as China and India spewing carbon dioxide as they burn coal to power expanding populations and economies.
These crux issues must ultimately be settled at the political level.
France's top diplomat Laurent Fabius, who will preside over the year-end summit, said yesterday there were "objective reasons" for anticipating success.
Chiefly, "the phenomenon (of climate change) has strengthened, and awareness along with it," he told Europe1 radio.