Demonstrators protest on November 28, 2015 in Geneva, during a rally ahead of the UN climate summit COP21
Masses of people joined a worldwide wave of marches on Saturday demanding leaders craft a pact to avert a climate catastrophe when they gather in a still-shaken Paris.
From Australia to New Zealand, the Philippines, Bangladesh and Japan, people rallied at the start of a weekend of popular protests urging world powers to seal a deal at the UN climate summit that officially opens in the French capital Monday.
"Protect our common home," declared placards held aloft as thousands gathered in Melbourne, a call echoed on the streets of Johannesburg and Edinburgh.
In Paris, religious leaders delivered petitions with almost 1.8 million signatures from people around the world urging politicians to take decisive action to curb global warming and help poor countries deal with climate change.
Some 150 leaders, including US President Barack Obama, China's Xi Jinping, India's Narendra Modi and Russian President Vladimir Putin, will attend the start of the Paris conference, which is tasked with reaching the first truly universal climate pact.
The goal is to limit average global warming to two degrees Celsius (3.6 degrees Fahrenheit) or less over pre-Industrial Revolution levels by curbing fossil fuel emissions blamed for climate change.
If they fail, scientists warn the world may become increasingly inhospitable to human life, with superstorms, drought and rising sea levels that swamp vast areas of land.
On the eve of Saturday's protests, French President Francois Hollande warned of the obstacles ahead for the 195 nations that will be represented at the talks following more than two decades of bickering.
"Man is the worst enemy of man. We can see it with terrorism," said Hollande, after leading ceremonies in Paris to mourn the victims of the deadly November 13 bombing and shooting attacks that sowed terror in the French capital.
"But we can say the same when it comes to climate. Human beings are destroying nature, damaging the environment. It is therefore for human beings to face up to their responsibilities for the good of future generations."
- Compromise call -
Potential stumbling blocks in Paris abound, ranging from financing for climate-vulnerable countries to scrutiny of commitments to curb greenhouse gases and even the legal status of the accord.
The last attempt to forge a global deal -- the ill-tempered 2009 Copenhagen summit -- foundered upon divisions between rich and poor countries.
UN Secretary General Ban Ki-moon said he was optimistic of success in the talks, due to end on December 11, but emphasised all sides must be prepared to compromise.
"I am urging the world leaders that they must agree on the middle ground, there is no such perfect agreement in this world," Ban told France 24 television on Saturday.
French Foreign Minister Laurent Fabius said 183 nations, covering 95 percent of greenhouse gas emissions, had submitted plans on how they intended to fight climate change -- a key part of the planned Paris agreement.
"This is extremely good news," he told reporters.
Speaking alongside Fabius, UN climate chief Christiana Figueres said the voluntary carbon-curbing pledges would still put Earth on track for warming of between 2.7 and 3.5 C.
Figueres said the pledges had moved the world away from warming of up to six degrees, calling it "fundamental progress", she said, adding the Paris agreement could "chart the path" for continued improvement in the years ahead.
Commonwealth nations, which represent a third of the world's population, also pledged Saturday to work for an ambitious and legally binding Paris agreement.
After a summit in Malta, leaders from the diverse group of 53 nations, also agreed to set up a billion-dollar "Green Finance Facility" for environmental projects.
- Human chain in Paris -
Protest organisers say they expect hundreds of thousands to take to the streets globally this weekend, with rallies planned for Sunday in Sydney, Seoul, Rio de Janeiro, New York, Kiev and Mexico City.
In Paris, French authorities cancelled two demonstrations following the onslaught by gunmen and suicide bombers which killed 130 people at restaurant terraces, a concert hall and the national stadium on November 13.
Demonstrators have declared their solidarity with activists unable to rally in Paris with a social media campaign tagged #march4me.
Activists still plan to create a two-kilometre (1.2-mile) human chain along the original march route on Sunday.
They will break the chain as they pass the Bataclan concert hall, where the worst violence claimed 90 lives, as a mark of respect to the victims.
Protesters also plan to leave scores of shoes on Place de la Republique square to symbolise the thousands left frustrated in their plans to march.
Negotiations by bureaucrats ahead of the official opening of the Paris conference, which will gather some 40,000 people, including 10,000 delegates, have been brought forward to Sunday.
About 2,800 police and soldiers will secure the conference site, and 6,300 others will deploy in Paris.