NEW YORK—From Asia to the Americas, Europe and Middle East, activists on Saturday rallied to mobilize public opinion against global warming 50 days ahead of a crucial UN climate summit.

The activists held events marking the number that the world needs to reach to prevent disastrous climate change: 350.

The number represents 350 parts per million of carbon dioxide emissions that the atmosphere can bear to avoid runaway global warming. The atmosphere currently reaches the safe upper limit of 390 ppm of carbon dioxide, according to research by NASA climate scientist James Hanse cited by 350.org.

In southern Philippines, some 1,000 students, soldiers and activists in Iligan City formed a human chain in the shape of number 350.

In Sydney, thousands of people assembled on the steps of the Opera House waving placards bearing the logo 350.

In New York’s Times Square, a crowd of demonstrators gathered around giant screens beaming images of the coordinated mass actions that organizers said were taking place in “more than 180 countries” at 5,200 events.

“It was ordinary people rallying around a scientific data point,” said 350.org founder Bill McKibben. “Nothing like that has ever happened before.”

McKibben, an environmentalist and author of “The End of Nature,” said the day was unique because it emphasized the science behind a politically complicated topic.

In Venezuela, volunteers formed a human chain marking the number zero on the beach at Catia La Mar, north of Caracas, to mark the spot where they said the ocean would reach if global warming is not stopped.

McKibben said volunteers also sent in photos of separate groups forming the number 350 around the Dead Sea, in Jordan, Israel and Palestinian territory.

Copenhagen meeting

Many of the events referred to the Copenhagen conference scheduled in December that will seek to reach a new global climate change treaty to replace the 1997 Kyoto Protocol on carbon dioxide emissions.

The Copenhagen summit has been billed as a last chance in avoiding a global catastrophe that could be felt for generations.

McKibben said there were lessons to be learned from the Kyoto Protocol, which the United States did not join.

“We saw what happened,” he said. “Everybody walked away once it was done, and there was no real progress. We need to pick up the pace.”

In France, politicians received a “wake-up” call from several hundred Parisians who chose clocks as their protest symbol.

Protesters, who met on a central square in Paris, set their alarm clocks and mobile phones to ring at 12:18 p.m. (1018 GMT) in reference to the closing date of the UN summit in Copenhagen scheduled on Dec. 7-18.

Environmentalists are hoping that world leaders shall be able to thresh out a new treaty curbing greenhouse gas emissions in place of the Kyoto Protocol, which expires in 2012.

Talks may fail

But senior officials from the United States and China, the world’s two largest polluters, have warned the December talks may fail.

There is growing concern that a treaty deal in Copenhagen could be hampered by issues that include US domestic politics and the problems of securing agreement between developed and developing countries.

In Berlin, some 350 protesters wearing masks with the face of German Chancellor Angela Merkel rallied in front of the Brandenburg Gate at the city center.

In London, more than 600 people gathered beneath the London Eye Ferris wheel by the River Thames to arrange themselves into the shape of the number 5, according to organizers Campaign against Climate Change.

An aerial photograph of the event will be added to pictures of a giant number 3 and number 0 from around the world.

“Hundreds of thousands of people are taking part (globally) and for us that’s so important, to have people out on the streets,” said campaign activist Abi Edgar. “We want serious action on climate change and we want it now.”

F note

Across the Thames, some 100 musicians playing trumpets, trombones, saxophones and clarinets gathered outside parliament to play the same note—an F made by the frequency of 350 Hz—for 350 seconds, organizers said.

In the Lebanese capital of Beirut, hundreds of activists wearing snorkels demonstrated at 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 350 logo.

“It’s not the first time Beirut will have gone under water,” Wael Hmaidan of the IndyACT that organized Beirut’s protests said as he explained the wearing of snorkels.

“But this time, it’s going down because of climate change, and not earthquakes,” Hmaidan said.

‘Sun, wind, right now!’

Environmental activists in the Turkish metropolis of Istanbul staged their protest in a boat, unfurling a banner reading, “Sun, wind, right now!” under the main bridge linking Asia and Europe over the Bosphorus Strait.

They then sailed to the ancient Maiden’s Tower, which sits on a tiny islet in the Bosphorus, and unfurled another banner reading “Jobs, climate, justice.”

Events in Asia included demonstrators in Dhaka riding bicycles to highlight one way of cutting emissions.

In Jakarta, around 100 students from the London School of Public Relations gathered to form the symbolic number 350, coordinator Candy Tolosa said on Detik.com news website. Reports from Richel Umel, Inquirer Mindanao, Agence France-Presse and Associated Press