Sydney: Tens of thousands marched across Australia Sunday on a third day of worldwide rallies as pressure mounts on global leaders to strike a pact on slashing greenhouse gases at crunch talks in still-shaken Paris.

Some 150 leaders including US President Barack Obama, China’s Xi Jinping, India’s Narendra Modi and Russia’s Vladimir Putin will attend the start of the UN conference Monday, 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), perhaps less, over pre-Industrial Revolution levels by curbing fossil fuel emissions blamed for climate change.

Rallies demanding curbs to carbon pollution have been snowballing since Friday with marches across Australia Sunday kickstarting a final day of people-powered protest.

Similar events were planned for Seoul, Rio de Janeiro, New York and Mexico City, among others cities, with scientists warning of superstorms, drought, and rising sea levels that swamp vast areas of land if concrete action is not taken.

‘There is no Planet B,’ said one placard in Sydney where tens of thousands of people converged, while another read: ‘Solidarity on a global scale’.

A large event in Melbourne on Friday kick-started the global campaign, with rallies on Saturday from New Zealand, to the Philippines, Bangladesh, Japan, South Africa and the UK.

‘Man’s worst enemy’

A march of some 5,000 people in Adelaide on Sunday focused on the global impacts climate change has on health, food security and development, particularly among the world’s poorest.

‘Those who did the least to cause the problem are feeling the impacts first and hardest, like our sisters and brothers in the Pacific,’ said Judee Adams, a community campaigner with Oxfam.

Many low-lying Pacific nations such as Kiribati, Tuvalu and the Marshall Islands fear they could disappear beneath the waves completely as sea levels rise.

The message to curb global warming and help poor countries deal with climate change was hammered home by religious leaders in Paris delivering petitions with almost 1.8 million signatures from people around the world.

This week, the UN’s weather body said the average global temperature for the year 2015 is set to touch 1 C, halfway towards the Paris conference’s attempted limit.

And analysts say voluntary carbon-curbing pledges submitted by nations to bolster the Paris pact, even if fully adhered to, put Earth on track for warming of 3 C.

On the eve of Saturday’s protests, French President Francois Hollande, host of the November 30-December 11 talks, warned of obstacles ahead for the 195 nations seeking new limits on heat-trapping gas emissions from 2020.

‘Man is the worst enemy of man. We can see it with terrorism,’ said Hollande, who spoke after leading ceremonies in Paris to mourn the victims of the 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.’

The French leader called for ‘a binding agreement, a universal agreement, one that is ambitious.’

But he also spoke of fears that a handful of countries — which he did not name — may stymie consensus if they felt the deal lacked guarantees.

Stumbling blocks

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.

In Paris, French authorities cancelled two demonstrations following the onslaught by gunmen and suicide bombers which killed 130 people across the city on 13 November.

Activists now plan to create a two-kilometre (1.2-mile) human chain along the original march route on Sunday. They will break it 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.

In a sign of the urgency of the talks ahead, the start of the climate negotiations themselves, conducted by rank-and-file bureaucrats, have been brought forward to Sunday on the eve of the official opening.

About 2,800 police and soldiers will secure the conference site, and 6,300 others will deploy in Paris with French Interior Minister Bernard Cazeneuve saying nearly 1,000 people thought to pose security risks had been denied entry into France.