World-famous landmarks including the Pyramids, the Eiffel Tower and Beijing's Forbidden City will go dark Saturday as millions turn out the lights for "Earth Hour", a rolling grassroots movement aimed at fighting climate change.
Now in its fourth year, the event looks set to be the biggest yet with thousands of cities and towns in 125 countries -- 37 more than last year -- pledging to take part in the aftermath of a failed climate summit last year.
Despite December's fractious Copenhagen summit and recent controversy over climate science, public opinion still hopes for meaningful action to avert catastrophic global warming, according to Earth Hour founder Andy Ridley.
"24-hour wave of hope and action"
"There appears to be some fatigue to the politics around it... But people are far more motivated this year than they were last year," he told AFP in Sydney.
Now run by the WWF, Earth Hour began in Sydney in 2007 when 2.2 million people switched off the lights in their homes, offices and businesses for 60 minutes to make a point about electricity consumption and carbon pollution.
The campaign went global the following year, and this Saturday, more than 1,200 of the world's best-known sites will kill their lights at 8:30 pm local time in what organizers describe as a "24-hour wave of hope and action."
A raft of multinational companies including Google, Coca-Cola, Hilton, McDonalds, Canon, HSBC and IKEA have endorsed Earth Hour 2010 and pledged to darken their offices worldwide in support.
Sydney's iconic Harbor Bridge and Opera House will help kick off the energy-saving marathon, with Egypt's Pyramids and Sphinx, the Trevi Fountain and Tower of Pisa in Italy and all major landmarks in Paris to take part, led by a five-minute blackout of the Eiffel Tower.
In London, Big Ben, the Houses of Parliament, St. Paul's Cathedral and the London Eye ferris wheel were among the tourist hotspots set to plunge into darkness, along with Manchester United's Old Trafford football ground.
Some 30 U.S. states and municipalities were to mark Earth Hour with darkness falling on sites including Mount Rushmore, the Empire State Building, the Golden Gate Bridge and Seattle's Space Needle.
In Dubai the world's tallest skyscraper, Burj Khalifa, will also dim its lights as will the high-priced office towers and five-star hotels strung along Hong Kong's famed harbor-front.
Crossing geographic boundaries
The Forbidden City in rapidly developing China, which was blamed by many activists for Copenhagen's failure, will go dark, along with the "Bird's Nest" Olympic stadium.
Elsewhere in Asia, where 3.3 million people have registered to take part, the world's biggest observation wheel, the Singapore Flyer, will extinguish its main lights, while official buildings will be blacked out in Seoul and Jakarta.
Scores of cities in India were expected to take part, including the massive urban centers of Delhi and Mumbai, while the country's thriving Bollywood film studios were to shut down for the hour.
Japan's heritage-listed Hiroshima Peace Memorial, one of few buildings to survive America's 1945 atomic bomb attack, will take part, while major companies including Sony, Sharp and Asahi were to switch off across Tokyo.
But in Bangkok, city authorities said they were under military orders to halt their Earth Hour campaign for security reasons, as tens of thousands of anti-government protesters planned another major rally on Saturday.
Residents of Norway's Longyearbyen, the world's northernmost town, are set to brave an influx of curious polar bears normally deterred by lights after voting -- for the first time -- that participating was worth the risk.
"Earth Hour is meant to cross geographic, economic, country boundaries," said Ridley, admitting that it was mostly a symbolic act.
"It's one hour, one day, one year. We're not saving the planet by turning the lights off for one hour."