BEIJING, CHINA - MARCH 23: This composite photograph shows a huge LED sky screen before and during the Earth Hour 2013 power switch off at the Central Business District on March 23, 2013 in Beijing, China. Earth Hour, launched in 2007 in Australia by the World Wide Fund for Nature (WWF), a global conservation group, calls on people, organizations and cities to turn off their non-essential lights for one hour starting at 8:30 p.m. local time. (Photo by Feng Li/Getty Images)
Earth Hour 2013
Cities around the world dimmed their lights to mark Earth Hour from 8:30 p.m. to 9:30 p.m. on Saturday, March 23.