Earth hour - Sydney Opera House
The Sydney Opera House goes green for Earth Hour! Image from WWF Australia. (official Facebook Site of Earth Hour)

Earth Hour 2013 will be observed across the globe on Saturday (23 March) in a bid to campaign against climate change.

Earth Hour is an event organized by the World Wide Fund for Nature (WWF). Hundreds of millions of people worldwide are expected to turn off the lights on Saturday night at 8:30 p.m. - 9:30 p.m. Lights will be switched off in many of the world's important landmarks including the Empire State Building in the United States, the Effiel Tower in Paris and the Sydney Opera House in Australia.

Earth Hour originated in Australia so as to raise awareness about carbon pollution. This year's Earth Hour Australia has asked the people to move to renewable energy. Unlike in the past, the lights at the Sydney Opera House will not be turned off. Instead, it will glow a deep green.

"What started as an event in Sydney in 2007 with two million people has now become a tradition across the country and across the world," Dermot O'Gorman, head of WWF-Australia, said, according to Agence France-Presse news agency.

"It's now an organic, people-powered movement... which is fantastic."

Last year, Earth Hour was observed on 31 March. A record number of 150 countries and territories across 6,494 towns and cities took part in the Earth Hour event and turned off the lights in an effort to raise awareness about global warming and support for renewable energy.

India joined the Earth Hour movement in 2009, when five million people across 56 cities turned off the lights and saved about 1000 MW of power in that one hour. In 2011, a record number of 130 Indian cities switched off the lights and committed to a low carbon lifestyle, according to Earth Hour's official website.

This year too, many Indians are expected to observe Earth hour on Saturday night. The Gateway of India and India Gate are just two of the significant landmarks in India that will switch off the lights on the eve of Earth Hour.

Prominent stars, celebrities, sportspersons, national leaders have also pledged their support to Earth Hour. The list includes Bollwood actors Ajay Devgn, Abhishek Bachchan, world boxing champion Mary Kom, former cricketer Venkatesh Prasad, Telugu actor Shruti Hassan, Tamil actor Jiiva, Bengali actor Parambrata, Chief Minister of New Delhi, Sheila Dixit; and Chief Minister of Himachal Pradesh, Virbhadra Singh.

Earth Hour 2013: World Landmarks Plunge into Darkness [STUNNING PHOTOS]