The Salt Lake Temple and the Salt Lake City-County Building will be among local landmarks going dark for an hour Saturday night as part of the worldwide Earth Hour efforts calling attention to global climate change.

And it won't be the first time temple lights have been dimmed for an energy-conscious cause.

The World Wildlife Fund, organizer of the Earth Hour, hopes 1 billion people respond to the call to turn off lights Saturday night from 8:30 to 9:30. Nearly 3,000 cities in 70-plus countries have agreed to participate in the third-year of the effort, which started in Sydney in 2007 with an estimated 2.2 million homes and businesses participating.

Other cities — including Rome, London and Paris — instituted similar efforts that year; Utah was the first state nationally to join the cause with its September 2007 "Lights Out Utah" campaign.

Organizers in 2007 approached leaders of The Church of Jesus Christ of Latter-day Saints to participate by briefly dimming the Salt Lake Temple's exterior floodlights. For the third time in as many years, the Salt Lake Temple will go dark for Saturday night's designated hour; interior lights accommodating temple patrons will remain on, as will lighting in the visitors center and for public safety in and around Temple Square.

"Prudent stewardship and wise use of resources are principles that church leaders have emphasized throughout the history of the church," said LDS Church spokesman Scott Trotter. "The church encourages its members to join with their fellow citizens in supporting worthy programs that will make their communities better places to live and raise their families."

Salt Lake City will participate in the event by switching off the lights at the City-County Building.

"We're wanting to at least do our part," said Vicki Bennett, the city's sustainability director. "People need to be aware of how much energy they are using in their everyday lives and how much they can reduce it if they try."

Besides participation from banks, hotels and other high-profile businesses, corporate involvement will range from McDonald's dimming their trademark golden arches to Broadway marquees going dark in New York City. Even the lights along the Las Vegas Strip will shut down for an hour.

That city's signature lighting only goes off for a minute or so at a time to honor recently deceased legendary Vegas entertainers.

An estimated 50 million participated last year in the first coordinated global effort, with lights off at San Francisco's Golden Gate Bridge, Rome's Colosseum, Sydney's Opera House and New York City's Coca-Cola billboard at Times Square.