Even as politicians dial down expectations for the December 7-18 UN climate talks in Copenhagen, analysts and activists detect a groundswell of anger, channelled through the Internet and voiced especially by the young, demanding action on global warming.

Conventional wisdom says environmental issues wax at times of prosperity and wane when belts are tightened.

But these sources believe that adage no longer holds true in the face of the unique threat posed by climate change.

When the talks to craft a post-2012 climate pact get underway, leaders may find themselves facing a coordinated movement cutting across continents, creeds and class, they argue.

"As evidence mounts of the severity of the threat, civil society groups will be fuelled by the urgency of acting now to avoid the worse consequences of a problem for which future generations will surely hold us accountable," said British expert Peter Newell.

"We can expect the continued and expanded use of all resources available to them -- legal and non-legal, constructive and coercive, national, regional and international," said Newell, a professor at the University of East Anglia in England.

Over the past half-century, broad-based movements -- from civil rights in the United States to anti-missile protests in Europe, "people power" revolts in the Philippines and South Korea -- have been largely confined to national borders.

Climate change, though, cuts across all frontiers. Some regions will be hit earlier and harder than others, but no place on Earth will be spared the greenhouse effect.

Awareness has also been boosted by disasters. Typhoon-driven floods that ravaged east Asia last month drove home the perceived links between warming and extreme weather, even if scientists point out such connections are far from linear.

"There is a growing awareness in developing countries that this issue is impacting them now and that they need to do something about it. That awareness is especially strong in Asia," Yvo de Boer, the UN's top climate official, told AFP.

Then there is the Internet, an infinitely more powerful organisational tool for protest than the cassette tapes, fax machines and roneo-copied "samizdat" leaflets of the recent past.

In authoritarian countries, notably China, it has helped civil society cohere around environmental and climate issues to a degree not tolerated for political and human rights, or trade unionism.

The prospects for a borderless protest movement will be put to the test on Saturday, selected by grassroots group 350.org as a "day of global action" with some 3,000 events around the planet.

The brainchild of US environmentalist Bill McKibben, 350.org takes its name from a warning issued by climate expert James Hansen, who says atmospheric concentration of CO2 must be pegged below 350 parts per million (ppm) to avoid potential catastrophe.

Levels are currently around 385 ppm and on track to bust a 450 ppm threshold previously viewed as safe.

Launched in March 2008, the Web-based network says it has nearly 200,000 activists in dozens of grassroots groups spread across 170 countries.

"It has worked beyond our wildest expectations," McKibben told AFP. "We've basically got the whole world organised, much of it for the first time. October 24 is going to be, by a very large margin, the most widespread day of environmental action ever."

Two demographic profiles dominate among 350.org's rank-and-file, McKibben said: educated youth and people linked by religion.

"I was aware of climate change but didn't know what I could do," Gan Pei Ling, 22, a student at Tunku Abdul Rahman University in Malaysia, said this month at climate talks in Bangkok, where she had come to lobby negotiators.

Meeting a small node of activists in Malaysia gave her the courage to speak out, and 350.org put her in touch with like-minded young people across Asia and beyond.

Gan Pei Ling and hundreds of other 20-something activists who converged on Bangkok -- many sporting T-shirts asking "How Old Will You Be in 2050?" -- see global warming as an injustice toward the poor and the young.

"Older people don't seem to care," said Lokendra Shrestha, a 28-year-old sociology student from Nepal, where vanishing glaciers threaten much of Asia's water supply.

Religion is also emerging as a lightning rod.

"Climate has risen up massively as an issue of concern in religious communities," said Stuart Scott, a former statistics professor from Hawaii who has crisscrossed the globe garnering support for his Interfaith Declaration on Climate Change (www.interfaithdeclaration.org).

His cause got a big boost when the declaration was included in an oecumenical ceremony at the UN Nations last month ahead of the world's first climate summit.

"It would be a huge mobilising force if people started to frame the issue of climate change in religious terms," noted Newell.

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