Leonardo DiCaprio delivered a Hollywood-style jolt Friday to divided UN climate talks in Paris, challenging negotiators to act boldly and swiftly to save mankind from disastrous global warming.

Joining Oscar-winner Robert Redford in the French capital, DiCaprio tried to inject much-needed urgency into efforts to strike a deal to curb greenhouse gas emissions that threaten to play havoc with Earth's delicate climate system.

"Please do not let fear and doubt slow you down. Be bold, be courageous, do everything in your power to change our current course," DiCaprio told a summit of local leaders at the Paris town hall, held on the sidelines of the UN conference.

DiCaprio, one of the world's most famous actors but also a longtime environment campaigner, told negotiators they had the option of being "timid" and settling for a face-saving agreement.
"Or they can lead. They can return to their home towns and with a real plan to save the planet," he said.

Redford, an Oscar-winning director and another passionate environment advocate, told the same gathering: "It is even more urgent than ever."

Adding more star power pressure on negotiators, Sean Penn arrives at the UN talks on Saturday to press for the safeguarding of forests, which play a vital role by soaking up carbon dioxide in the atmosphere, and Arnold Schwarzenegger is scheduled to swoop in early next week.

They will follow an historic summit of 150 world leaders who opened the talks on Monday with a chorus of calls for urgent action.

- Marathon struggle -
But at the venue for the 195-nation talks in Le Bourget on the northern outskirts of Paris, negotiators were on Friday entrenched in familiar battle-lines over who should shoulder the cost for the epic struggle ahead.

The planned agreement would establish a universal framework for cutting greenhouse gas emissions that trap the Sun's heat, warming Earth's surface and oceans.

Scientists warn Earth will become increasingly hostile for mankind as it warms, such as with rising sea levels that will consume islands and populated coastal areas, as well as catastrophic storms and severe droughts.

However, cutting emissions requires a shift away from burning coal, oil and gas for energy, as well the destruction of carbon-storing rainforests -- costly exercises that powerful business interests are determined to press on with.
Rich nations have also been reluctant during two decades of UN negotiations to comply with demands from poorer countries that they must pay for the shift to renewable technologies, as well as to cope with climate change.

At stake is hundreds of billions of dollars that would need to start flowing from rich to developing nations from 2020, under the planned Paris pact.

With frustrations at the conference mounting, UN Secretary-General Ban Ki-moon called on the world's developed economies to honour the financing pledge they made at the last major climate summit six years ago.

"I have been urging the developed world leaders that this must be delivered," Ban told reporters at UN headquarters in New York. "This is one very important promise."

United Nations Secretary-General Ban Ki-moon speaks during a meeting as part of the World Climate Change Conference (COP21) on December 4, 2015 in Paris
© AFP Alain Jocard

Participants in the Paris conference say the negotiations are constructive but too slow, with a December 11 deadline for a pact looming.

"The negotiating status is still very far away from the target of trying to achieve a comprehensive, effective, balanced and legally binding agreement which is equitable to all parties," Chinese negotiator Xie Zhenhua told journalists.

- That's the way it goes -

Chief US negotiator Todd Stern said attempts to draw up a draft deal acceptable to all sides were advancing, however.
"It's moving in the right direction," he said." "There's an option that we like. There's an option that we hate. That's the way it goes."

Another battleground is how much to try to limit global warming.

The biggest polluting nations, such as the United States and China, want to enshrine a target of 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-Industrial Revolution levels.

Weaker nations most at risk want a much tougher target of 1.5 C, which would require the global economy to transform away from fossil fuels and be fully reliant on renewables by 2050.

Lower-level negotiators have until Saturday to eliminate as many disagreements as possible from a draft text, before handing it over to ministers for them to begin debate on Monday.

They wrapped up formal discussions on Friday night after some compromises that eased tensions slightly, but with none of the major points of dispute resolved.
Source: AFP