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Cities Worldwide Observe Earth Hour

The World Wildlife Federation in Australia began a campaign in 2007 to raise awareness of the human impact on climate change by asking the city of Sydney to turn off their lights for an hour. Organizers say Sydney cut is greenhouse gas emissions for the hour by more than 10 percent last year.

This year, more than 35 nations will observe Earth Hour by turning off non-essential lights at 8 p.m. local time.

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