IT BEGAN with a tinkle of bells on a sunny spring morning as Bikezilla, a multi-storey, seven-seat, six-wheeled cycle arced across the Melbourne Museum forecourt, leading about 1000 yellow-clad cyclists along Rathdowne Street for a rally to promote the 350.org campaign.
Three hundred and fifty is the number of parts per million of carbon dioxide in the atmosphere that campaigners argue is the safe upper limit if the planet is to avoid climatic catastrophe.
Organisers say that with the global level sitting at 390 parts per milion, drastic action is necessary at the Copenhagen international summit in December to turn the count around.
More than 5200 events were scheduled to take place in 181 countries and territories from Addis Ababa in Ethiopia to the Vinson Massif in Antarctica, calling for ''strong action and bold leadership on the climate crisis''.
Thousands of climate change activists rallied at the Sydney Opera House and other Australian locations to kick off a worldwide day of action billed as the largest ever. More than 2000 activists formed the number 350 with blue umbrellas in near perfect spring weather.
In Brisbane, 350 frisbees were thrown into the air simultaneously, and the same number was spelt out in a recently felled old-growth forest in Tasmania's Styx Rainforest.
The Great Barrier Reef was the focus for a northern Queensland rally while the Safe Climate Coalition rallied outside Western Australia's Parliament House in Perth and Darwin residents formed a human tide-line across the top of Jingili footbridge.
A blimp hovered above Melbourne's Alexandra Gardens as the cyclists, who had taken a slow circuitous route through the city, made a human sign of 350 to mark Melbourne's participation in the global event.
Anna Rose, Australia's Young Environmentalist of the Year, addressed the crowd, describing how the campaign came together and the significance of winning supporters such as Tim Flannery and UK economist Nicholas Stern.
Senator Bob Brown in Melbourne yesterday said meeting the 350 target would be tough but necessary in the face of cataclysmic climate change.