France's top diplomat, who will preside over a year-end Paris summit tasked with inking a climate rescue pact, warned Sunday of looming planetary "catastrophe" if negotiations fail.

"It is life on our planet itself which is at stake," Foreign Minister Laurent Fabius told journalists as ministers and climate envoys from 70 countries met for pre-summit talks to iron out tough political questions.

With the key UN conference just three weeks away, he also announced that Russia's President Vladimir Putin would attend the November 30 opening.

Russia, a major oil producer, is seen as a deal-maker or -breaker in the years-long attempt to negotiate the world's first truly universal pact to curb climate-altering greenhouse gas emissions.

"There is absolute urgency," said Fabius, to achieve the UN goal of limiting global warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.

The UN's climate science panel has warned of an average temperature rise of "four, five, six degrees, if we do not act extremely quickly," he said.

"This would have catastrophic consequences because there would be drought... and colossal migration problems, including problems of war and peace."

A global deal to prevent worst-case-scenario warming is meant to be inked by ministers at the end of a November 30-December 11 Conference of Parties (COP21) in the French capital.

It will be opened by UN chief Ban Ki-moon and some 100 heads of state and government including US President Barack Obama, China's Xi Jinping, Narendra Modi of India -- and now also Putin.

The three-day ministerial "pre-COP" from Sunday to Tuesday, must seek political convergence on key issues still dividing nations, to avoid a repeat of the 2009 Copenhagen summit which ended without a binding global pact.

"This pre-COP is a way to build the confidence and ensure that we will reach our objective in Paris at COP21," Peru's environment minister Manuel Pulgar-Vidal, who chaired COP20 in Lima last year, told ministers.

And Fabius urged them to "find a road of compromise on as many subjects as possible."

The Paris agreement will be underpinned by national pledges to curb greenhouse gas emissions from burning coal, oil and gas.

- High stakes -

But the UN this week issued a fresh warning that pledges submitted to date set the stage for warming of closer to 3 C, or more.

Last month, scientists said the first nine months of 2015 had been the hottest on record worldwide.

Ministers will base their discussions in the coming days on a rough draft of a deal compiled by rank-and-file diplomats over years of tough negotiations in the UN climate forum.

They cannot alter the text -- merely identify areas for potential political compromise to be fed back into it.

For now, the blueprint remains little more than a laundry list of often directly-opposing national options for dealing with the challenge at hand.

Developing countries insist rich ones should lead the way in slashing emissions as they have polluted for longer.

They also want assurances of finance to make the shift from cheap and abundant fossil fuel to greener energy sources, and to shore up defences against climate change-induced superstorms, drought, flood and sea-level rise.

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.

Ministers of all the negotiating blocs gathered in Paris on Sunday, including top envoys from major carbon emitters China, the United States, the European Union, India, Brazil, Russia and Saudi Arabia.

It is the third such ministerial round in Paris this year.

National pledges 'far from enough' to halt global warming: UN
Paris (AFP) Nov 6, 2015 - Carbon-cutting pledges from 146 nations are "far from enough" to stave off dangerous global warming, the UN warned Friday, three weeks ahead of a crucial climate summit in Paris.

The voluntary efforts to curb greenhouse gases -- if respected -- would only yield a third of the cuts needed by 2030 to keep Earth from overheating, according to a UN Environment Programme (UNEP) report.

Countries have made "an historic level of commitment" with their pledges, UNEP Executive Director Achim Steiner said in a statement.

"However, they are not sufficient to limit global temperature rise to the recommended level of two degrees Celsius (3.6 degrees Fahrenheit) this century."

Beyond that threshold, scientists say, lies a world plagued by deadly drought, superstorms, and mass migration.

The emissions reduction plans -- called Intended Nationally Determined Contributions, or INDCs -- would result in a temperature hike of 3.0 C (4.8 F) or more by 2100, UNEP said.

Other scientific estimates have varied between 2.7 C and 3.5 C.

The annual "Emissions Gap" analysis tracks the difference between projected CO2 pollution, on the one hand, and the levels required to stay under the UN 2 C target, on the other.

- 'Far from enough' -

This year's report is the first to take into account greenhouse gas reduction promises made ahead of the November 30-December 11 Paris summit, tasked with delivering the first-ever universal climate pact.

Without the INDCs, humanity is set to spew some 60 billion tonnes of carbon dioxide equivalent -- a measure that groups different greenhouse gases including methane and nitrous oxide -- into the atmosphere in 2030.

The INDCs would shave 6 billion tonnes off the top, leaving the total at 54 billion tonnes.

But to keep the 2 C target on track, total emissions in 2030 should not exceed 42 billion tonnes, according to the UN's climate science panel.

That means that the INDCs only cover a third of the 18 billion tonne gap between the current trajectory, and where we need to be in 2030.

"The submitted contributions are far from enough, and the emissions gap in both 2025 and 2030 will be very significant," the report said.

Moreover, it notes, greenhouse gas output would still be rising in 2030.

Many scientists say it is crucial to bend the emissions curve -- to make it peak, in other words -- as soon as possible.

The longer we wait, they say, the harder and more expensive it will be to transition to a low-carbon global economy.

In 2014, greenhouse gas emissions from all sources totalled just under the equivalent of 53 billion tonnes of CO2.

That output will have to drop to near zero by 2075 at the latest to stay under 2 C, scientists say.

The UNEP findings bolster a report released last week by the UN's climate body showing that even if these national carbon-cutting schemes were carried out, humanity will have exhausted two-thirds of its "carbon budget" by 2030.

- Periodic review -

The carbon budget is the total amount of greenhouse gases we can put into the air while still having a better than even chance of capping warming at 2 C.

Starting from this year, that budget is about one trillion tonnes.

Both reviews took into account the 146 INDCs submitted to the UN by October 1, which includes all developed nations and three-quarters of developing ones.

Collectively, they cover some 88 percent of the world's greenhouse gas emissions.

Many of the pledges from developing countries, such as India, are contingent on receiving financial support, one of the most sharply contested issues at the upcoming summit.

The UN Green Climate Fund said Friday it had approved $168 million -- the first funds to be made available -- for projects in Africa, Asia and South America to help poor nations adapt to climate impacts already visible or in the pipeline.

On a brighter note, many analysts have said that most INDC pledges are probably conservative, leaving room for greater ambition.

Another make-or-break issue in Paris will be crafting a mechanism that pushes countries to periodically review -- and boost -- their carbon-cutting pledges in light of new technologies and progress to date.

"We need provisions in the Paris agreement to encourage review and revision of the inital round of INDCs, and that should happen by the end of this decade," commented Alden Meyer, a climate analyst at the Washington-based Union of Concerned Scientists.