French Foreign minister and president of the COP21 Laurent Fabius visits the location of the upcoming COP21/CMP11 climate change talks in Le Bourget, near Paris, on November 8, 2015

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.

Foreign Minister Laurent Fabius's remarks came as separate reports warned of the devastating effects of global warming on the poor and those living in megacities around the world.

"It is life on our planet itself which is at stake," 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."

'Existential danger'

Separate reports released Sunday echoed those concerns.

A World Bank study warned that global warming could elevate levels of disease, ravage crops and push 100 million more people into poverty.

Graphic detailing national carbon-cutting pledges so far and an evaluation of whether or not they are sufficient to prevent global warming exceeding +2°C

"The poor are more vulnerable to climate-related shocks than wealthier people because they are more exposed, lose more in relative terms, and lack the financial systems and social safety nets that would allow them to better prepare and cope," it said.

Another study by the US-based research group Climate Control, meanwhile, warned that a 2 C rise in temperatures could still pose a "long-term, existential danger to many great coastal cities".

It added that a worse-case scenario of a 4 C rise could particularly affect China, with four of the 10 most devastated cities in that forecast set to be Chinese.

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.

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

Hottest on record

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.

A three-day ministerial gathering near Paris, from Sunday to Tuesday, must seek political convergence on key political issues still dividing nations negotiating for a climate pact

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.

Russian President Vladimir Putin has confirmed he will join more than 100 heads of state and government at the UN climate summit in Paris in December

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.

Explore further France's Fabius urges stragglers to publish emissions data

© 2015 AFP