The mayor of Sydney, Australia, led the city in a global warming awareness exercise this weekend by turning off all the lights for one hour to save power and cut emissions. From the suspension lights of the famous harbor bridge to suburban homes and skyscrapers, many lights that are normally left on in deserted buildings were turned off as a reminder that every little switch counts. (Compare the photos from AP.) A poll found as many as half the population — as many as 2.2 million — participated.