A picturesque supercell formation in the northwest of Booker, Texas from June 2013. (Photo by Mike Olbinski/Barcroft Media)

Children play football in front of an abandoned train compartment next to a railway track in Dhaka, in this May 29, 2014 file photo. (Photo by Andrew Biraj/Reuters)

A dog sits in the shade of a mangrove tree as a woman uses a fork to dig for shellfish on the reef-mud flats of a lagoon located at South Tarawa in the central Pacific island nation of Kiribati May 23, 2013. Kiribati consists of a chain of 33 atolls and islands that stand just metres above sea level, spread over a huge expanse of otherwise empty ocean. With surrounding sea levels rising, Kiribati President Anote Tong has predicted his country will likely become uninhabitable in 30-60 years because of inundation and contamination of its freshwater supplies. (Photo by David Gray/Reuters)

Three very colouful alpacas enjoy the hot weather at Toft Farm, Rugby, on July 19, 2013. (Photo by Caters News)

Jack, a Lurcher from Dogs Trust Salisbury, walks past a window display of models in a Dogs Trust shop window in Salisbury, as part of a campaign to discourage the impulse buying of dogs ahead of Valentine's Day, on February 10, 2014. (Photo by Matt Alexander/PA Wire)

A chevrotain or mouse deer feeds in its enclosure at Zurich Zoo, Zurich, Switzerland, October 17, 2012. (Photo by Patrick B. Kraemer/AP)

Three Chinese soldiers at the time of a civil war in China. (Photo by General Photographic Agency/Getty Images). 1922