Indigenous Sahrawi girls play on an improvised see-saw at a refugee camp of Boudjdour in Tindouf, southern Algeria March 3, 2016. UN Secretary General Ban Ki-moon is scheduled to visit the Sahrawi refugees in south-west Algeria's Tindouf region. (Photo by Zohra Bensemra/Reuters)

A girl paddles on her stand-up board on the waters of Guanabara bay at Bica beach in Rio de Janeiro Brazil, January 10, 2016. Few features capture the beauty, or the problems, of one of the world's most dramatic urban landscapes like Guanabara Bay - the finger-like inlet that forms the shoreline and harbor for Rio de Janeiro. The bay, which carves into southeast Brazil from the Atlantic Ocean, literally gave Rio its name when Portuguese mariners mistook it for a “rio”, or “river”. Four centuries later, the bay is preparing to welcome another sort of seafarer – Olympic sailors, who will navigate the bay when the 2016 Rio Olympics kick off in August. (Photo by Ricardo Moraes/Reuters)

Li Guoqiang talks on his phone outside his house at Guangfuli neighbourhood, in Shanghai, China, April 1, 2016. Li, 38, is a deliveryman who rents a place at Guangfuli. In a corner of Shanghai, surrounded by a cement wall, lies one of the world's most valuable fields of debris and garbage. On paper, the Guangfuli neighbourhood is a real estate investor's dream: a plot in the middle of one of the world's most expensive and fast-rising property markets. But the reality is more like a developer's nightmare, thanks to hundreds of people living there who have refused to budge from their ramshackle homes for nearly 16 years as the local authority sought to clear the land for new construction. (Photo by Aly Song/Reuters)

A car enthusiast races at the Goodwood Revival historic motor racing festival in Goodwood, near Chichester in south England, Britain, September 11, 2015. The three-day event held each September at Goodwood Circuit since 1998 attracts thousands dressed in period costume who watch motor racing in vehicles from the mid-twentieth century heyday of the venue. (Photo by Toby Melville/Reuters)

A witch doctor prepares an offering for the inauguration of the World People's Conference on Climate Change and the Defense of Life, prior to the World Climate Change Conference, in Tiquipaya, Bolivia, October 10, 2015. Almost 150 nations, including major emitters led by China and the United States, have submitted plans to the United Nations for curbing greenhouse gas emissions blamed by the U.N. for causing more floods, droughts and heat waves. France will host the conference in Le Bourget, near Paris, from November 30 to December 11, 2015. (Photo by David Mercado/Reuters)

A ballet dancer stretches backstage during Nacho Duato's “The Nutcracker” at the Mikhailovsky Theatre in St. Petersburg, Russia November 21, 2015. For theatregoers in St Petersburg, Nacho Duato's “The Nutcracker” demonstrates the global appeal of a Christmas classic. When the curtain rises at the Mikhailovsky Theatre, among the oldest opera and ballet houses in Russia, it's the culmination of hundreds of hours of toil and sweat by dancers, costume makers, set designers and musicians playing the famous score by Pyotr Tchaikovsky. (Photo by Grigory Dukor/Reuters)

Black-headed gulls sit on pickets at a riverside in Tokyo, Japan, December 27, 2015. (Photo by Toru Hanai/Reuters)

A colorful sky at sunset over the snowy mountains in Immenstadt, Bavaria, Germany, 20 November 2014. Cloudy weather is forecast in the region on 21 November. (Photo by Karl-Josef Hildenbrand/EPA)