People hold out money as butchers sell their remaining produce of the year at discounted prices during the traditional Christmas Eve auction at Smithfield's market in London December 24, 2015. (Photo by Neil Hall/Reuters)

A couple watches the sunset over a sea of fog covering the Geneva Lake from Chardonne, Switzerland, 28 December 2015. (Photo by Jean-Christophe Bott/EPA)

“The power of nature”. Magma, ash and gas erupt from Mount Etna in December 2015, rising to a height of several kilometres. Winner: Nature. (Photo by Giuseppe Mario Famiani/SIPA Contest)

Chen Ruolin of China performs a jump during the mixed team event final at the Aquatics World Championships in Kazan, Russia July 29, 2015. (Photo by Stefan Wermuth/Reuters)

A child looks at a polar bear swimming under a water in its enclosure on a hot summer day at Prague Zoo, Czech Republic, July 30, 2015. (Photo by David W. Cerny/Reuters)

A woman dressed as a Viking drinks local red wine during the annual Viking festival of Catoira in north-western Spain August 2, 2015. The festival re-enacts past Viking raids in the area and is celebrated annually on the first Sunday in August. (Photo by Miguel Vidal/Reuters)

Pakistani laborers transport the front portion of a vehicle using a handcart at a road in Peshawar, Pakistan, Monday, August 3, 2015. (Photo by Mohammad Sajjad/AP Photo)

Chantel Sydnor participates in the annual Sturgis Motorcycle Rally in Sturgis, South Dakota, August 4, 2015. This year marks the 75th anniversary of the rally expected to draw hundreds of thousands of motorcycle enthusiasts from around the world for events throughout the week-long festival, according to organizers. (Photo by Kristina Barker/Reuters)