Beachgoers are hit by a wave in La Libertad May 3, 2015. El Salvador emergency authorities declared a green alert along the pacific coats due to a large swell that affected the Salvadoran coast and originated from the extra-tropical storms that formed in New Zealand and the Southern hemisphere, according to El Salvador's ministry of environment and natural resources. (Photo by Jose Cabezas/Reuters)

A man rides his bicycle as a wave crashes at La Libertad malecon on May 13, 2015. El Salvador emergency authorities has declared an orange alert along the Pacific coast due to a large swell that affected the Salvadoran coast. The swell originated from the extra-tropical storms that formed in New Zealand and the Southern hemisphere, according to El Salvador's Ministry of Environment and Natural Resources. (Photo by Jose Cabezas/Reuters)

Members of the Cyclophonica band play instruments as they make a stop during a ride in Rio de Janeiro May 17, 2015. The Cyclophonica band was formed by a group of musicians riding bicycles around the city, mixing sport and culture and entertaining people on the streets, according to its founder Leonardo Fuks. (Photo by Pilar Olivares/Reuters)

Lebanese university students wearing municipality police costume regulate the traffic in the village of Brummana, east Beirut, Lebanon, 23 June 2018. The touristic town of Brummana is making a daring move in anticipation of the crowded summer season, by forming a group of young policewomen wearing mini shorts to regulate the traffic. (Photo by Wael Hamzeh/EPA/EFE)

To an outsider, their passion is at times illegal and often on the verge of life and death. But climbing rooftops of high-rise buildings and exploring abandoned facilities is in the blood of these young Muscovites. The small group calls itself “Rudex”, which stands for “roof and decay exploration”, and is akin a Western youth craze known as urbex or “urban exploration” of man-made structures. Here: Urban explorer Vad Him of Rudex team jumps whilst on a rooftop in Moscow, Russia, August 14, 2017. (Photo by Maxim Shemetov/Reuters)

A detail of the Sagrada Familia Basilica, designed by architect Antoni Gaudi, in Barcelona, Spain, Wednesday, October 21, 2015. Barcelona's breathtaking La Sagrada Familia Basilica has begun its final phase of raising six immense towers. Presenting the project Thursday, chief architect Jordi Fauli said the central "Tower of Jesus Christ," the tallest of the six, will rise 172.5 meters (566 feet) high, making it "the tallest religious building in Europe". (Photo by Manu Fernandez/AP Photo)

A worker carries a tray of boiled tofu in a traditional tofu factory in Depok, Indonesia, 21 January 2015. Tofu has been a common side dish for many Indonesian families. It is healthy, inexpensive and easy to find throughout the city. Tofu entrepreneurs in Indonesia are suffering due to the weakening of the rupiah against the US dollar and the rise in prices of imported soybeans in the international market, forcing tofu-makers to cut their production and lay off staff. (Photo by Adi Weda/EPA)

The Greenland ice sheet is a vast body of ice covering 660,235 sq miles, roughly 80% of the surface of Greenland. It is the second largest ice body in the world, after the Antarctic Ice Sheet. Some scientists predict that climate change may be near a "tipping point" where the entire ice sheet will melt in about 2000 years. If the entire 2,850,000 cubic kilometres (683,751 cu mi) of ice were to melt, it would lead to a global sea level rise of 7.2 m (23.6 ft).