Ministers seeking to avoid climate catastrophe reported rare cooperation Monday as they launched five days of frenetic negotiations in Paris to reach a historic global deal.

The 195-nation UN talks have been billed as the last chance to avert the worst consequences of global warming: deadly drought, floods and storms, and rising seas that will engulf islands and densely populated coastlines.

"The opportunity to rise to the call of history is not given to everyone or every day," UN climate chief Christiana Figueres told the conference, which aims to overcome decades of division and broker an elusive universal pact.

"History has chosen you here, now."

UN Secretary General Ban Ki-moon warned negotiators "the clock is ticking towards a climate catastrophe", and implored them to put aside the rows and soft compromises that have cursed previous UN climate campaigns.

"The world is expecting more from you than half-measures and incremental approaches. It is calling for a transformative agreement," Ban said.

"The decisions you make here will reverberate down the ages."

- Coal addiction -

Taking effect from 2020, the Paris accord would seek to limit emissions of heat-trapping greenhouse gases driven by coal, oil and gas -- the backbone of the world's energy supply today.

The goal is to limit global warming to under two degrees Celsius (3.6 degrees Fahrenheit) from pre-Industrial Revolution levels.

Scientists say the planet is already nearly halfway to 2C, which means the rise in fossil-fuel emissions must peak soon, and go quickly into reverse, to meet the precious objective.

The Paris talks opened November 30 with a record-breaking gathering of 150 world leaders issuing a chorus of warnings about mankind's fate if planet warming goes unchecked.

After a week of talks, negotiators met a Saturday deadline to produce a broad blueprint but left unresolved many of the deep and complex divisions that condemned previous UN efforts to failure.

Environment and foreign ministers, including US Secretary of State John Kerry, were then tasked from Monday with ripping out hundreds of bracketed words or sentences in the blueprint that denote disagreement.

The ministers have a Friday deadline to reach an accord, seeking to resolve the stubborn arguments that primarily pit rich nations against the poor.

- Flexibility, compromise -

Giving rise to cautious optimism, end-of-day work reports issued by the leaders of negotiating groups tasked with tackling the various flashpoint issues all reported a spirit of cooperation and a willingness to compromise.

"On a number of issues there has been growing convergence and also some flexibility by parties to move towards common ground," said Gabon's Emmanuel Issoze-Ngondet, who is facilitating debates on finance.

While no key breakthroughs were announced, the facilitators of the other debates echoed sentiments of "flexibility" and "convergence".

Among the slew of fundamental issues in dispute are how far and how fast to limit global warming, and how to review national commitments to curb greenhouse gas emissions.

Small island states at risk of being swamped in a warmer world are also part of a big coalition of vulnerable nations pressing for a more ambitious accord of limiting planetary warming to less than 1.5C.

"Any further temperature increase beyond 1.5 degrees Celsius will spell the total demise of Tuvalu and other low-lying island nations," Tuvalu Prime Minister Enele Sosene Sopoaga told the conference.

"If we save Tuvalu we save the world."

- Money fight -

Another potential deal-buster is money.

Rich countries promised in 2009 to muster $100 billion (92 billion euros) a year from 2020 to help developing nations make the costly shift to clean energy, and to cope with the impacts of global warming.

But how the pledged funds will be raised remains unclear -- and developing countries are pushing for a promise that the amount will be ramped up beyond 2020.

Meanwhile, rich nations are insisting that developing giants work harder to tackle their greenhouse gases, noting that much of the world's future emissions growth will come from their fast-growing economies.

"It is time to get rid of this rigid differentiation between developed and developing in a way that prevents us from maximising our progress going forward," Kerry said after flying in from the United States.

Even on this issue, the end-of-day work report heard that all sides had shown flexibility and a compromise solution was possible.

A new study released on the sidelines of the talks offered another ray of hope, reporting that emissions of major global warming culprit carbon dioxide were set to decline in 2015.

It would be the first such planetary-wide fall in a period of economic growth, said the report in the journal Nature Climate Change, explaining that decreased coal use in China was the main factor.

But it cautioned that 2015 was unlikely to be the year in which CO2 peaks -- a glittering objective for climate campaigners -- and said emissions would take years to decline "substantively".

In a timely reminder of a future in which emissions could go unchecked, a "red alert" for air pollution was issued in China's capital Beijing on Monday.