The world turns the lights off during Earth Hour

Beijing, China: A combination picture shows a tower in the Forbidden City before (top) and during Earth Hour (bottom).
Photograph: Jason Lee/Reuters

Singapore: A couple walks along a darkened street with the aid of a torch after the lights go out as part of Earth Hour.
Photograph: Wong Maye-E/AP

Kuala Lumpur, Malaysia: The Petronas Towers, the tallest twin buildings in the world, are thrown into near darkness.
Photograph: Lai Seng Sin/AP

Hong Kong, China: A traditional Chinese junk floats on Victoria harbour during Earth Hour as properties along the iconic waterfront go dark along with millions of homes.
Photograph: Daniel Sorabji/AFP

Beijing, China: The lights are gradually turned off at the National Stadium, otherwise known as the Bird's Nest.
Photograph: Grace Liang/Reuters

Financial district, Singapore: People gather by candlelight in a city park during Earth Hour.
Photograph: Pablo Sanchez/Reuters

Shanghai, China: A combination photo shows The Bund waterfront along the banks of the Huangpu River before (top) and during Earth Hour (bottom).
Photograph: Aly Song/Reuters

Beijing, China: Another view of the Forbidden City, before and during Earth Hour, as its lights are turned off in a show of support for tougher action on climate change.
Photograph: Jason Lee/Reuters

Beijing, China: The National Aquatics Center, also known as the Water Cube, before and during Earth Hour.
Photograph: Grace Liang/Reuters

Sydney: The Harbour Bridge
Photograph: Lisa Maree Williams/Getty

London: Tower Bridge
Photograph: Jon Freeman /WWF

Cardiff: The Welsh assembly
Photograph: WWF

London: Piccadilly Circus
Photograph: Jiri Rezac/WWF

London: The houses of parliament
Photograph: Jas Lehal/Reuters

London: Trafalgar Hotel, before and after
Photograph: Jonathan Short /WWF