Cities switch off for Earth Hour

Major cities and global landmarks have been plunged into darkness as millions of people switched off lights for an hour to protest against climate change.

The initiative, Earth Hour, was begun in Sydney two years ago by green campaigners keen to cut energy use.

Correspondents say the aim is to create a huge wave of public pressure to influence a meeting in Copenhagen later this year to seek a new climate treaty.

Critics describe the event as a symbolic and meaningless gesture.

The switch-off was planned to take place in more than 3,400 towns and cities across 88 countries, at 2030 in each local time zone.

Earth Hour was launched in 2007 as a solo event in Sydney, Australia, with more than two million people involved. Last year's event claimed the participation of 370 cities.

Organisers said they wanted to demonstrate what people can do to reduce their carbon footprint and save energy, thus drawing attention to the problem of climate change.

China debut

This time Sydney was one of the first places to switch off. The BBC's Nick Bryant described a city where skyscrapers were hard to make out against the night sky.

In pictures: Earth Hour

Is your city taking part?

Hours later, Beijing's most prominent Olympic venues, the Bird's Nest and Water Cube, went dark. China is taking part for the first time, with major cities like Hong Kong, Shanghai and Guangzhou also dimming their lights.

Other locations due to take part this time include Edinburgh Castle in Scotland, St Peter's Basilica in Rome, Paris' Eiffel Tower, the Egyptian Pyramids and New York's Empire State Building.

Fast-food giant McDonald's has pledged to dim its "golden arches" at 500 locations, while celebrities such as actress Cate Blanchett and Archbishop Desmond Tutu have promised support.

UN Secretary-General Ban Ki-moon backed the initiative in a video posted this month on the event's YouTube channel.

"Earth Hour is a way for the citizens of the world to send a clear message," he said. "They want action on climate change."

People are invited to provide blogs and short video clips on how they spend their time.

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