A mass pillow fight in Trafalgar Square in central London on April 5, 2014 on International Pillow Fight Day. (Photo by Jane Scanlan)

An Iraqi Shi'ite boy poses for a photograph as Iraq Shi'ite Muslims commemorate Ashura in Baghdad, October 24, 2015. Ashura, which falls on the 10th day of the Islamic month of Muharram, commemorates the death of Imam Hussein, grandson of Prophet Mohammad, who was killed in the seventh century battle of Kerbala. (Photo by Ahmed Saad/Reuters)

An aerial view shows the 11/19 pit and twin slag heaps at the former coal mine site in Loos-en-Gohelle, northern France, November 1, 2015. Loos-en-Gohelle, a town of 7000 inhabitants in the North of France, marked by the closure of coal mines in 1970, has demonstrated a successful transition from coal to a green economy. (Photo by Pascal Rossignol/Reuters)

The rising sun illuminates the sky above the spires of a church in Vienna, Austria, November 17, 2015. (Photo by Heinz-Peter Bader/Reuters)

A woman holding an umbrella walks past the sculpture by Chinese artist Yue Minjun beside a road during a snow in Beijing, China, November 22, 2015. (Photo by Jason Lee/Reuters)

A hot air balloon floats over farm fields south of Washington, Ill., as the sun slips behind clouds on the autumn afternoon of Wednesday, September 24, 2014. (Photo by Ron Johnson/AP Photo/Peoria Journal Star)

An activist takes a selfie during a protest ahead of the 2015 Paris Climate Conference, in Paris, Sunday, November 29, 2015. More than 140 world leaders are gathering around Paris for high-stakes climate talks that start Monday, and activists are holding marches and protests around the world to urge them to reach a strong agreement to slow global warming. (Photo by Christophe Ena/AP Photo)

Aisha, 15, (L) (who asked to withhold her last name), a Syrian refugee from Raqqa, waits with a fellow refugee while harvesting cannabis in the Bekaa valley, Lebanon October 19, 2015. Syrian refugees work to harvest and process spiky-leafed cannabis plants in neighbouring Lebanon’s Bekaa Valley. Often farmers of cotton and wheat back home in Raqqa province – now the de facto capital of Islamic State – the conflict in Syria drove them to seek safety in a region where Syrian migrant workers used to spend a few months a year before returning home. (Photo by Alia Haju/Reuters)