Roped up climbers leave the summit of Breithorn at 4,164 metres (13,661 feet) on the ridge marking the border with Switzerland (left) and Italy in the Alpine resort of Zermatt August 4, 2014. Switzerland will vote on November 30 on an initiative from the group Ecopop which proposes a cap on the number of immigrants. The group says it is motivated by concerns about a lack of living space exerting too much pressure on the land and natural resources, rather than by opposition to foreigners. (Photo by Denis Balibouse/Reuters)

Cassandra Cantu shields her 7-week-old puppy Kamala from the snow as she walks with friends in the Bear Creek Dog Park in Colorado Springs, Colo., Sunday, May 11, 2014. A spring storm that has brought over a foot of snow to parts of Colorado, Wyoming and Nebraska and thunderstorms and tornadoes to the Midwest was slowing down travelers and left some without power Monday morning. (Photo by Mark Reis/AP Photo/The Gazette)

A woman holds her umbrella while walking against strong winds as Typhoon Soudelor approaches Taiwan in Taipei, August 7, 2015. (Photo by Pichi Chuang/Reuters)

It might have been foggy in the Willamette Valley, but Cerridwen Martin was able to revel in a view of the top of the clouds from the summit of Spencer Butte in Eugene, Ore., on Tuesday, December 16, 2014. Martin was joined by Joe Martinson, right, for the 1.1 mile trek. Fog shrouded much of the city for most of the day. (Photo by Andy Nelson/AP Photo/The Register-Guard)

Vehicles move past a man resting on a taxi, as he waits for passengers, along a road in Karachi, Pakistan, May 5, 2015. (Photo by Akhtar Soomro/Reuters)

An art installation formed with milk churns, made by land art artist Gerard Benoit a la Guillaume, is seen at the Chenau de Mayen in the resort of Leysin, Switzerland August 7, 2015. More than 80 milk churns were placed between the Tour d'Ai and the Tour de Mayen summits at an altitude of 2,000 meters (6,561 feet) above sea level under the direction of the artist, to be photographed for his ongoing art project entitled “Milk churns without borders”. (Photo by Denis Balibouse/Reuters)

Tiny pieces of space rocks, called meteorites, are seen burning in the atmosphere over the night sky near Salgótarján, some 109km northeast of Budapest, Hungary, 21 April 2018 (issued 22 April 2018). (Photo by Peter Komka/EPA/EFE)