Lights on landmarks, city halls, hotels, theaters and arenas will be turned off for an hour Saturday evening in cities across North America and some areas abroad in a display of concern about global warming. Earth Hour, as the March 29 event is called, is intended to show that individuals, business owners and public officials working together can make a difference in the fight against climate change. Participants will darken the outside of buildings, except for safety lights, from 8-9 p.m. local time.

The World Wildlife Federation organized the first lights-out demonstration last year in Sydney, Australia. About 2,100 Sydney businesses, plus an estimated 2.2 million Australians there and elsewhere, turned off their lights. Even the well-known Harbor Bridge and Sydney Opera House went dark for an hour. According to the Earth Hour Web site, www.earthhour.org, that 2007 blackout reduced Sydney's energy consumption by 10 percent -- the equivalent of taking 48,000 cars off the road for a year.

Now the nonprofit group is going global, with observances in 25 "flagship cities" in 10 countries - including Atlanta, Chicago, Phoenix and San Francisco - where non-essential exterior lights will go dark for an hour on many skyscrapers, theaters, sports arenas and other buildings. Even McDonald's will turn off its golden arches at all 485 of its sites in the Chicago area and Northwest Indiana.
Restaurants in some areas are creating Earth Hour menus to be served by candlelight, and numerous municipalities are hosting free public celebrations such as concerts. Local environmental groups and mayors' offices are promoting observances in Denver, Miami, Honolulu, Charlotte, NC, and communities in Massachusetts.

Mayor says: "The big picture is about creating a consciousness. Do we really need to have every single light on in our homes every night?" - Manny Diaz, mayor of Miami

Skeptic says: "This is the kind of big, symbolic gesture everyone loves. . . . Just remember, when and if you're doing it, that the real issues are more complicated." - Lorrie Goldstein, associate editor, Sun Media Group (Canada)

Earth Hour every day: Turn off appliances while not in use. Use energy-efficient light bulbs. Switch off lights when leaving a room.