Vehicles pass through the heavy fog and air pollution that cover Skopje valley in the early morning, in Skopje, The Former Yugoslav Republic of Macedonia, 14 December 2017. According to media reports, Skopje is considered one of the most polluted cities in the world. (Photo by Georgi Licovski/EPA/EFE)

An artist gets ready backstage to perform an Indian art form of dance called “Ottamthullal” at the annual eight-day long Vrischikolsavam festival, which features a colourful procession of decorated elephants along with drum and trumpets concerts, at Sree Poornathrayeesa temple in Kochi, India, December 7, 2018. (Photo by Sivaram V/Reuters)

A man stands by an installation depicting “2019” in the Red Square in Moscow, Russia on December 17, 2018. (Photo by Maxim Shemetov/Reuters)

A picture made available on 08 July 2015 showsa lightning strikes during a heavy storm over Poznan in the night of 07 July 2015. Severe storms passed last night over Poland causing lots of damages to buildings, trees, electricity and railway tractions. (Photo by Lukasz Ogrodowczyk/EPA)

A cat walks past a Soyuz space ship installed at a museum, at the Russian leased Baikonur cosmodrome, Kazakhstan, Tuesday, November 15, 2016. The start of the new Soyuz mission to the International Space Station (ISS) is scheduled on early Friday, Nov. 18 local time. The Russian rocket will carry French astronaut Thomas Pesquet, Russian cosmonaut Oleg Novitsky and U.S. astronaut Peggy Annette Whitson. (Photo by Dmitri Lovetsky/AP Photo)

Pakistan girls make selfies holding a Pakistan-made weapon displayed at the four-day International Defence Exhibition and Seminar (IDEAS) 2016 in Karachi, Pakistan, Wednesday, November 23, 2016. (Photo by Shakil Adil/AP Photo)

Girls take part in the traditional seasonal Christmas run along the streets of Vilnius, Lithuania, Sunday, December 17, 2017. The festive run attracts many hundreds of people to the capital dressed as Santa Clause to take part in the sporting event. (Photo by Mindaugas Kulbis/AP Photo)

A demonstrator confronts riot police during a rally in defense of the nationalization of lithium reserves in the country, in Santiago, Chile on January 29, 2018. (Photo by Pablo Sanhueza/Reuters)