A Macedonian police officer hits a stranded migrant attempting to cross the Greek-Macedonian border, near Gevgelija, Macedonia December 2, 2015. Picture taken from the Greek side of the border. (Photo by Alexandros Avramidis/Reuters)

A Somali woman shows traditional items and food during an event to showcase traditional Somali culture in Hamarweyne district in the capital Mogadishu, December 3, 2015. (Photo by Feisal Omar/Reuters)

A Harley Davidson biker is dressed as Santa Claus as he takes part in a charity ride in Zurich, Switzerland December 6, 2015. (Photo by Arnd Wiegmann/Reuters)

Anti-Heathrow expansion activists walk through the “Grow Heathrow” protest camp in the village of Sipson near to Heathrow Airport, west London Britain December 7, 2015. (Photo by Peter Nicholls/Reuters)

The Chavo del Ocho balloon makes its way along the streets during an annual Christmas parade at Santiago town in Chile, December 13, 2015. (Photo by Pablo Sanhueza/Reuters)

A man works inside a bakery in the rebel-controlled area of Maaret al-Numan town in Idlib province, Syria December 17, 2015. (Photo by Khalil Ashawi/Reuters)

A young Chinese girl dressed in Christmas costume, hugs a pedestrian on a street to celebrate Christmas in Nanjing city, east China's Jiangsu province, 23 December 2015. (Photo by Imaginechina/Splash News)

Swimmers prepare to take part in the annual Christmas Day Peter Pan Cup handicap race in the Serpentine River, in Hyde Park, London, December 25, 2015. (Photo by Andrew Winning/Reuters)