Women walk through the snow on Wimbledon common with their dogs on February 10, 2012 in London, England. The Met Office cold weather alert remains at Level 3 as southern parts of England continue to suffer from cold weather and freezing conditions, with further snowfall overnight. (Photo by Peter Macdiarmid/Getty Images)

Water gushes out from the Xiaolangdi Reservoir on the Yellow River during a sand-washing operation on June 20, 2012 in Luoyang, China. The sand-washing operation, which started on June 19 and will last for about 20 days, is conducted to clear out the silt deposits at the dam. (Photo by China Foto Press)

Sheep are herded during the annual sheep parade through Madrid November 2, 2014. Shepherds parade the sheep through the city every year in order to exercise their right to use traditional routes to migrate their livestock from northern Spain to winter grazing pasture land in southern Spain. (Photo by Susana Vera/Reuters)