In this photo taken on Friday, July 14, 2017, a student at a paramilitary camp for children calls the rank to attention outside Kiev, Ukraine. As the deadly conflict in eastern Ukraine entered its third year, some parents in Ukraine are anxious to make sure their children are ready to fight it, instead of swimming and playing volleyball. (Photo by Efrem Lukatsky/AP Photo)

Cooler temperatures begin this week as a polar vortex brings much colder conditions with the chance of snow for Snowdonia, Ogwen Valley, North Wales on 22nd October 2018. The Ogwen Valley and Tryfan Mountain looking splendid in the Autumn sunrise. (Photo by DGDImages/Alamy Live News)

Carnival revelers perform during the Academicos do Baixo Augustaa carnival “bloco” parade in Sao Paulo, Brazil, Sunday, February 24, 2019. (Photo by Andre Penner/AP Photo)

Bathers brave the cold waters of the North Sea as they take part in the annual Boxing Day dip at Redcar Beach on December 26, 2019 in Redcar, England. The event attracts hundreds of people each year who take to the cold water wearing fancy dress as they help to raise money for a number of charities. (Photo by James Glossop/The Times)

Climate change activist Greta Thunberg reacts during a news conference during COP25 climate summit in Madrid, Spain, December 9, 2019. (Photo by Juan Medina/Reuters)

Shaolin boys practice kung fu in the sweltering heat during the zen shaolin music ceremony at shaolin temple, Dengfeng, Henan province, China on August 4, 2019. Shaolin unique skills include: shaolin arhat formation, three gun sashimi, shaolin stick, shaolin stone lock skill, iron hand splitting bricks, water training, fist and foot sparring. (Photo by Sipa Asia/Rex Features/Shutterstock)

Flames and smoke rising after a fire that broke out in Izmir province of Aegean Turkey on August 19, 2019. Fire brigade crew continue their works. Forest fires have consumed some 500 hectares (over 1,200 acres) of land in Izmir, Turkeys Aegean coast. On Sunday, the fires broke out in four different regions – including two in the southwestern Mugla province and others in Izmir province, according to Agriculture and Forest Ministry. (Photo by Emin Menguarslan/Anadolu Agency via Getty Images)

The Aurora Borealis (Northern Lights) is seen over the sky near Inari in Lapland, Finland on February 14, 2019. (Photo by Alexander Kuznetsov/Reuters)