A Police officer checks a man wearing a carnival costume in Venice, Italy, Sunday, January 31, 2016. Carnival-goers in Venice are being asked by police to momentarily lift their masks as part of new anti-terrorism measures for the annual festivities. Police are also examining backpacks and bags and using metal-detecting wands before revelers are allowed into St. Mark's Square, the heart of the Venetian carnival. (Photo by Luigi Costantini/AP Photo)

People look at a man, who residents said was killed by al Qaeda militants, hanging on a bridge in Yemen's southeastern city of Mukalla June 17, 2015. Al Qaeda militants in Yemen killed two alleged Saudi spies, residents said, accusing them of planting tracking devices which enabled the assassination of the group's leader in a suspected U.S. drone strike. (Photo by Reuters/Stringer)

The sculpture “It Takes Two to Tango” by Scottish sculptor David Mach is seen in front of the headquarters of the CMA-CGM shipping company office tower in the port of Marseille, France, March 15, 2016. (Photo by Jean-Paul Pelissier/Reuters)

Justin Nelzen, in red vest, joins others as they work to rescue up to 70 horses along Cypresswood Drive near Humble along Cypress Creek, Monday, April 18, 2016, in Houston. More than a foot of rain fell Monday in parts of Houston, submerging scores of subdivisions and several major interstate highways, forcing the closure of schools and knocking out power to thousands of residents who were urged to shelter in place. (Photo by Mark Mulligan/Houston Chronicle via AP Photo)

African women in their grandmothers' clothes: Joana Choumali’s portraits show modern African women swapping jeans for kente cloth – and diving into the dazzling cultural heritage of their families. (Photo by Joana Choumali/The Guardian)

Gas-masked men of the British Machine Gun Corps with a Vickers machine gun during the first battle of the Somme, 1916. (Photo by General Photographic Agency/Getty Images)

Clash of the storms, New Mexico, US by Camelia Czuchnicki. “A clash between two storm cells in New Mexico, US, each with its own rotating updraft. The curved striations of the oldest noticeable against the new bubbling convection of the newer. It was a fantastic sight to watch and it’s the rarity of such scenes that keep drawing me back to the US Plains each year”. (Photo by Camelia Czuchnicki/Weather Photographer of the Year 2016)

A young Shiite Muslim child participates in a Muharram procession in Ahmadabad, India, Sunday, October 9, 2016. (Photo by Ajit Solanki/AP Photo)