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 Photograph: Jason Lee/guardian.co.uk 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 Photograph: Wong Maye-E/guardian.co.uk Kuala Lumpur, Malaysia: The Petronas Towers, the tallest twin buildings in the world, are thrown into near darkness. Photograph: Lai Seng Sin/AP Photograph: Lai Seng Sin/guardian.co.uk 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 Photograph: Daniel Sorabji/guardian.co.uk Beijing, China: The lights are gradually turned off at the National Stadium, otherwise known as the Bird's Nest. Photograph: Grace Liang/Reuters Photograph: Grace Liang/guardian.co.uk Financial district, Singapore: People gather by candlelight in a city park during Earth Hour. Photograph: Pablo Sanchez/Reuters Photograph: Pablo Sanchez/guardian.co.uk 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 Photograph: Aly Song/guardian.co.uk 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 Photograph: Jason Lee/guardian.co.uk Beijing, China: The National Aquatics Center, also known as the Water Cube, before and during Earth Hour. Photograph: Grace Liang/Reuters Photograph: Grace Liang/guardian.co.uk Sydney: The Harbour Bridge Photograph: Lisa Maree Williams/Getty Photograph: Lisa Maree Williams/guardian.co.uk London: Tower Bridge Photograph: Jon Freeman /WWF Photograph: Jon Freeman /guardian.co.uk Cardiff: The Welsh assembly Photograph: WWF Photograph: guardian.co.uk London: Piccadilly Circus Photograph: Jiri Rezac/WWF Photograph: Jiri Rezac/guardian.co.uk London: The houses of parliament Photograph: Jas Lehal/Reuters Photograph: Jas Lehal/guardian.co.uk London: Trafalgar Hotel, before and after Photograph: Jonathan Short /WWF Photograph: Jonathan Short /guardian.co.uk