By Phil Mercer
BBC News, Sydney
Sydney has made one of the biggest environmental statements Australia has ever seen.
The white sails of the Opera House were darkened during Earth Hour
Parts of the country's largest city have been plunged into near darkness to raise awareness of global warming.
Lights on the city's iconic coat-hanger bridge were switched off, while the famous white sails of the Opera House were darkened.
Families held candle-lit picnics on the edges of Sydney harbour, while thousands of suburban homes were blacked out.
"I'm feeling very happy because everyone's participating in something that is for the world," explained Mexican tourist Nayeli Dellafuente.
Twelve-year-old Alex Martuccio from Sydney was also enthusiastic about the big switch-off.
"Tonight's a good way to save power and to help the world be a cleaner place," he said.
Hundreds of businesses joined in too. Many tower blocks have spent the evening in the dark, although there were notable exceptions.
'Time to act'
Earth Hour wasn't embraced by everyone - far from it - but organisers were delighted at the response.
"Australians are ready to do something about climate change and it's time to start making a move," said Andy Ridley from the World Wildlife Fund Australia, one of the architects of the event.
"This country is the driest inhabited continent on the planet and we face some of the worst aspects of global warming," he warned.
Sydney's lights-off campaign has had support from Hollywood. Australian actor Cate Blanchett told the BBC that climate change had become a global emergency.
"It's massive. It's very difficult to grasp in all its magnitude and complexities so I think that the potency of tonight is that it's about a very simple beginning - you know - turning off a switch," the screen queen added.
Earth Hour has been largely a symbolic exercise to try to make Australians think more about global warming.
Per capita this vast continent is one of the world's largest producers of carbon dioxide and other gases that many scientists believe are helping to warm the Earth's atmosphere.
A long-standing drought and serious water shortages in Australia have focused much attention in recent times on climate change.
Environmental worries have moved to centre stage here and they will be key issues in a federal election due later this year.
Drag queens have also been enlisted to help raise awareness.
One of Australia's oldest gay pubs - the Newtown Hotel in Sydney - organised a special drag show where the audience was handed mini-torches to light up the stage and bar staff were issued with miners' hats.
"Some of the drag queens will tell you they do look better in the dark anyway," pub licensee Roger Robertson said.
Drag queen Vanessa Wagner did a version of An Inconvenient Truth
"One of our drag queens Vanessa Wagner has done her version of the Al Gore movie An Inconvenient Truth.
"It's all pie charts and facts and figures - all done in the style of a 1970s housewife."
The Sydney Morning Herald, one of the sponsors of Earth Hour, has given a sobering editorial on the state of the planet.
"These days, the bad news on the environment just keeps on coming," the broadsheet told its readers on Saturday.
"Bushfires, drought, more frequent cyclones and storms, drying rivers, melting glaciers... each piece of bad news strikes home like a new entry on a casualty list in a long war.
"Sydney will dim its lights for an hour, to show that action to reduce energy use is possible. It is not a solution to global warming.
"But by co-opting motivated individuals and businesses to this one simple, symbolic gesture it will raise the public's awareness that something can be done, and must be done."