From Sydney Harbour to the Empire State Building, cities and world landmarks plunged into darkness Saturday as a symbolic energy-saving exercise unfolded across the globe.
Landmarks like the Petronas towers in Kuala Lumpar powered down
The pyramids at Giza in Egypt, the Acropolis in Athens and the Houses of Parliament in London cut their electricity as part of "Earth Hour," a worldwide call for action to avert potentially devastating climate change.
Some 371 landmarks powered down worldwide, including the Eiffel Tower, Niagara Falls, the Las Vegas casino strip and Beijing's "Bird's Nest" Olympic stadium.
The switch-off ended in Honolulu, capital of the US state of Hawaii.
Residents of the Chatham Islands, a territory of New Zealand in the southern Pacific Ocean, turned off light switches and kicked off the global Earth Hour. One of the event's dramatic episodes occurred in Sydney, where the iconic Opera House and Harbour Bridge plunged into darkness on Saturday night, killing their lights for an hour.
Millions of people turned out in Sydney, while Melbourne, Australia's second-largest city, came to life with a pedal-powered concert and others enjoyed moonlit picnics and barbecues.
The global grassroots movement began in Sydney two years ago, when 2.2 million people switched off their lights. Earth Hour has since grown to include 3,929 cities, villages and localities across the globe.
"It is a very positive, hopeful campaign," Andy Ridley, the event's director, told reporters in Sydney. "We want people to think, even if it is for an hour, what they can do to lower their carbon footprint and take that beyond the hour."
Organizers send message to world leaders
Ridley said he was aiming for one billion participants, hoping the event would send a resounding message to world leaders about significant emissions cuts.
Scientists have warned that global warming caused by burning fossil fuels on a massive scale could devastate the planet, hitting the poorest countries hardest with floods, droughts and disease.
Sceptics criticized the event as little more than empty symbolism, with Danish professor Bjorn Lomborg claiming the use of candles during the hour could produce more emissions than electric lights.
But United Nations Secretary-General Ban Ki-moon said in a video message earlier this month that "Earth Hour is a way for the citizens of the world to send a clear message. They want action on climate change."
Lights in the "city that never sleeps" began going dark at 8:30 pm (0130 CET) at some of New York City's most renowned buildings and landmarks, including Broadway theaters, the Empire State Building, the Chrysler Building and the signs of several big firms, including Coca-Cola's in Times Square.
In Washington, campuses of major universities and several embassies flipped the switch. People gathered at Freedom Plaza, which has an unobstructed view of the US Congress, to watch the lights dim on nearby buildings and hotels.
Iconic structures plunged into darkness
The famous Las Vegas strip went dim for Earth Hour
In London, the lights went off at the Houses of Parliament and the famous electronic billboard at Piccadilly Circus.
In Paris, hundreds of monuments and buildings, from the Louvre and Notre Dame Cathedral to the Arc de Triomphe, all went dark. For safety reasons, the lights on the Eiffel Tower were switched off for only five minutes.
Elsewhere across Europe, St Peter's Basilica in Rome and the Greek parliament in Athens were all plunged into darkness, while entertainers danced in front of the Romanian parliament in Bucharest.
In Egypt, the Giza pyramids, the Cairo Tower and the Alexandria Library on the Mediterranean all went dark.
In the United Arab Emirates, which has the highest per capita energy consumption in the world, Dubai's iconic sail-shaped seven-star Burj al Arab hotel turned off its nightly multi-colored light show.
The lights went dark in downtown Manila, as they did in the world's tallest completed skyscraper, the Taipei 101 building.
In South Africa, Table Mountain was to be seen only by starlight for an hour. And the Weekender newspaper reported that one couple would turn the lights down on their marriage at a vineyard near Cape Town.
The event ended in Honolulu, where municipal buildings darkened for the second consecutive year to mark the eco-friendly hour, according to local news reports.
A United Nations-led conference in the Danish capital later this year is meant to approve a new global warming treaty for after 2012, when the Kyoto Protocol for cutting carbon emissions expires.