A tribesman loyal to the Houthi movement carries his rifle as he leaves a gathering held to show support for the group, in Yemen's capital Sanaa December 15, 2015. (Photo by Khaled Abdullah/Reuters)

Refugees disembark and make their way to a camp at a hotel touted as the world's most northerly ski resort in Riksgransen, Sweden, December 15, 2015. (Photo by Ints Kalnins/Reuters)

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)

Fireworks light the sky over Copacabana beach during New Year's Eve celebrations in Rio de Janeiro, Brazil, Thursday, January 1, 2016. (Photo by Mauro Pimentel/AP Photo)

A participant runs towards the waters of the North Sea during the annual New Year's plunge event in Ostend, Belgium, January 2, 2016. (Photo by Francois Lenoir/Reuters)

A woman visits a room in a house built upside-down in Russia's Siberian city of Krasnoyarsk, December 14, 2014. The house was constructed as an attraction for local residents and tourists. (Photo by Ilya Naymushin/Reuters)

Soldiers are reflected in a puddle during a military parade during the celebrations for Romania's National Day in Bucharest December 1, 2014. (Photo by Radu Sigheti/Reuters)

St Mary's Cathedral is illuminated as part of a Christmas lights display in celebration of Christmas on December 19, 2014 in Sydney, Australia. (Photo by Brendon Thorne/Getty Images)