A colourful morning sunrise on Christmas Eve at Victoria Tower on Castle Hill, West Yorkshire, England on December 24, 2017. The history of human activity on the Castle Hill goes back over 4000 years. The site was developed as an iron age hill fort, surrounded by defensive ditches and ramparts. In the Middle Ages there was a castle on the hill, of which the well remains. The present tower was built to commemorate Queen Victoria's Diamond Jubilee of 1897. (Photo by Charlotte Graham/ZUMA Wire/Rex Features/Shutterstock)

Israeli soldiers of the Search and Rescue brigade take part in a training session in Ben Shemen forest, near the city of Modi'in May 23, 2016. (Photo by Amir Cohen/Reuters)

A competitor takes part in the 31st World Bog Snorkelling Championships, held annually at Llanwrtyd Wells in Wales, Britain August 28, 2016. Entrants must negotiate two lengths of a 60-yard trench through the peat bog in the quickest possible time without using any conventional swimming strokes. (Photo by Rebecca Naden/Reuters)

Kashmiri children play with snow on a wooden foot bridge in the interiors of Dal Lake in Srinagar on January 16, 2017. A cold wave has further tightened its grip in Jammu and Kashmir, with most places in the state recording sub-zero temperatures. (Photo by Tauseef Mustafa/AFP Photo)

A walker has left a handprint on a snow- covered tree trunk on Grosser Feldberg mountain in the Taunus mountain range, Germany, 16 January 2017. (Photo by Frank Rumpenhorst/DPA)

A supercell thunderstorm develops, May 8, 2017 in Elbert County outside of Limon, Colorado. With funding from the National Science Foundation and other government grants, scientists and meteorologists from the Center for Severe Weather Research try to get close to supercell storms and tornadoes trying to better understand tornado structure and strength, how low-level winds affect and damage buildings, and to learn more about tornado formation and prediction. (Photo by Drew Angerer/Getty Images)

In this photo taken Tuesday, February 2, 2016, asylum seekers gather round a fire as they cook a meal overlooking the temporary Altnes camp refugee camp on the island of Seiland, northern Norway. Waiting for their asylum claims to be processed, hundreds of people in emergency shelters in Hammerfest and neighboring towns are slowly getting used to the extreme climate and unfamiliar customs of the High North. They say they have adapted to the cold – the temperature rarely drops below minus 10 degrees C (14 F) along the coast, though it gets much colder further inland. It’s the darkness that throws them off. (Photo by Alastair Grant/AP Photo)

An aircraft passes over houses at it lands at Heathrow Airport near London, Britain, December 11, 2015. Picture taken December 11, 2015. (Photo by Neil Hall/Reuters)