Paris climate talks: Obama calls on world leaders to 'rise to the moment' to secure future for humanity

US president Barack Obama has called on world leaders to "rise to the moment" at the Paris climate change summit to secure our future.

More than 150 world leaders — including Prime Minister Malcolm Turnbull — have arrived in Paris to attend the United Nations talks, armed with promises and accompanied by high expectations as they look to hold back the Earth's rising temperature.

Mr Obama said a growing threat of climate change could define the contours of this century.

"As the leader of the world's largest economy and the second largest emitter ... the United States of America not only recognises our role in creating this problem, we embrace our responsibility to do something about it," he said.

"[The] future is one that we have the power to change right here right now, but only if we rise to this moment."

China's president Xi Jinping has pledged to work with Mr Obama, but said countries should be able to seek their own solutions to global warming.

"Developed countries should honour their commitment of mobilising $US100 billion each year from 2020 and provide stronger financial support to developing countries afterwards," he said.

"It is also important that climate-friendly technologies be transferred to developing countries."

Mr Xi also made it clear that poor nations should not have to sacrifice economic growth.

"Addressing climate change should not deny the legitimate needs of developing countries to reduce poverty and improve their people's living standards," he said.

"The Paris conference should reject the narrow-minded mentality of a zero-sum game and call on all countries — developed countries in particular — to assume more shared responsibilities for win-win outcomes."

China is the world's largest emitter of greenhouse gases on an absolute basis, but the United States emits far more per capita.

The world's two biggest carbon emitters, once on opposite sides on climate issues, agreed in 2014 to jointly kick-start a transition away from fossil fuels, each at their own speed and in their own way.

That partnership has been a balm for the main source of tension that characterised previous talks, in which the developing world argued that countries that grew rich by industrialising on fossil fuels should pay the cost of shifting all economies to a renewable energy future.

Statements of goodwill not enough: Hollande

French president Mr Hollande, who opened the summit, said that a deal to try to keep any further increase in global temperatures to below 2 degrees Celsius needed to be "universal, differentiated and binding", with richer countries contributing more than poorer ones.

"I can't separate the fight with terrorism from the fight against global warming," he said.

"These are two big global challenges we have to face up to, because we have to leave our children more than a world freed of terror, we also owe them a planet protected from catastrophes."

After decades of struggling negotiations marked by the failure of a previous summit in Copenhagen six years ago, some form of landmark agreement appears all but assured by mid-December.

Mr Hollande warned that there could not be a vague agreement.

"To resolve the climate crisis, good will, statements of intent are not enough," Mr Hollande said, telling world leaders that the future of humanity rested on their shoulders. "We are at breaking point."

Warnings from climate scientists, demands from activists and exhortations from religious leaders like Pope Francis, coupled with major advances in cleaner energy sources like solar power, have all added to pressure to cut the carbon emissions held responsible for warming the planet.

Most scientists say failure to agree on strong measures in Paris would doom the world to ever-hotter average temperatures, bringing with them deadlier storms, more frequent droughts and rising sea levels as polar ice caps melt.

As the summit opened in Paris, the capitals of the world's two most populous nations, China and India, were blanketed in hazardous, choking smog, with regulators in Beijing asking factories to limit output and halting construction work.

On the eve of the summit, hundreds of thousands of people from Australia to Paraguay joined the biggest day of climate change activism in history, telling world leaders there was "No Planet B" in the fight against global warming.

"This past year has been a turning point," Christiana Figueres, the UN's climate chief, told delegates.

Arriving in a sombre city where security has been tightened after Islamist militant attacks that killed 130 people on November 13, each leader will be allowed a brief opening speech, just a few minutes long.

Cooperation between China and US critical, Xi says

At the start of bilateral talks held on the sidelines of the Paris gathering, Mr Obama and Mr Xi pledged to work together for a climate change agreement that ensures a "low carbon global economy" this century.

Mr Obama said the two countries' decision to make their own emissions-reduction pledges last year had helped drive other nations to follow suit.

"As the two largest economies in the world and the two largest carbon emitters, we have both determined that it is our responsibility to take action," Mr Obama said, with Mr Xi sitting next to him.

"Our leadership on this issue has been absolutely vital."

Mr Xi said the two countries would work side by side to ensure the Paris conference achieved its goals, and he noted that cooperation between the United States and China at a time of multiple global challenges was critical.

"The world economy is recovering slowly, terrorism is on the rise and climate change is a huge challenge. There is more instability and uncertainty in [the] international situation," Mr Xi said.

Reuters