The thousands of small-scale events, staged 50 days before a UN summit on climate change, began with a gathering on the steps on the Sydney Opera House, before spreading across the globe.
"We had no idea it we would get the overwhelming support, enthusiasm and engagement from all over the world that we’re seeing," Bill McKibben, the founder of 350.org which co-ordinated the day’s events, said.
"It seems far-fetched that you could get this many people to rally around a scientific data point, but the number just keeps climbing. It shows just how scared of global warming much of the planet really is, and how fed up at the inaction of our leaders."
In Paris, politicians received a "wake up" call from several hundred activists who chose clocks as their symbol.
Protesters who met in a central square had set their alarm clocks and mobile phones to ring at 12:18 pm (10:18 GMT) in reference to the closing date of the UN summit in Denmark, which lasts from December 7-18.
'Painfully slow'
Lars Lokke Rasmussen, the Danish prime minister, said on Saturday that talks ahead of the meeting Copenhagen had been "painfully slow" and warned that world leaders could fail an ambitious deal on emissions.
"The sense of urgency is setting in as we approach the deadline," he told an international meeting of parliamentarians.
"Clearly, at current speed, we will not make it in the remaining weeks."
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| The events began with a mass protest outside the Sydney Opera House [AFP] |
Officials are trying to secure a global treaty that would replace the Kyoto Protocol, which will expire in 2012.
Rasmussen said progress had been made on some fronts, such as measures to adapt to climate change, technology and measures related to forestation and deforestation.
But crucial political questions remain unresolved, including the commitment of industrialised nations to ambitious mid-term targets to reduce greenhouse gas emissions and developing countries' commitments to national measures to curb growth in their emissions.
In London on Saturday, more than 600 people gathered beneath the London Eye ferris wheel by the River Thames to arrange themselves into the shape of the number five, according to organisers at the Campaign against Climate Change.
An aerial photograph of the event will be added to pictures of a giant "three" and "zero" from around the world.
In the Lebanese capital Beirut hundreds of activists, many wearing snorkels, held demonstrations in key archaeological sites.
They gathered around the Roman ruins in central Beirut, in the ancient eastern city of Baalbek and along the coast, carrying placards bearing the logo 350.
"It's not the first time Beirut will have gone under water," Wael Hmaidan of the IndyACT group organising Beirut's protests said, explaining the goggle-wearing. "But this time it's going down because of climate change, and not earthquakes."