Visitors take photos of a child dressed in a traditional costume before a folk performance in Panyu, Guangdong province, China on April 20, 2018. (Photo by Reuters/China Daily)

This undated photo provided by NOAA in May 2018 shows aurora australis near the South Pole Atmospheric Research Observatory in Antarctica. When a hole in the ozone formed over Antarctica, countries around the world in 1987 agreed to phase out several types of ozone-depleting chemicals called chlorofluorocarbons (CFCs). Production was banned, emissions fell and the hole shriveled. But according to a study released on Wednesday, May 16, 2018, scientists say since 2013, there’s more of a banned CFC going into the atmosphere. (Photo by Patrick Cullis/NOAA via AP Photo)

A picture taken with a drone shows the giant landart painting entitled “Message From Future” by French artist Saype in the park “La Perle du Lac” in Geneva, Switzerland, 16 September 2018 (issued 17 September). The artwork covering 5,000 square meters was produced with biodegradable paints made from natural pigments. The artist called the little girl “Future” as a symbol of the generations from the future and the small origami boats that she drops into Lake Geneva aims to represent a message of hope sent to the world. (Photo by Valentin Flauraud/EPA/EFE)

A youth skates next to a road in Palembang, South Sumatra, Indonesia on August 15, 2018. (Photo by Edgar Su/Reuters)

A swarm of starlings flies over the Altare della Patria monument (Unknown soldier) in the city centre of Rome during sunset, on November 27, 2018. (Photo by Vincenzo Pinto/AFP Photo)

Tourists enjoy hot pot and spring at the hotpot shaped spring during winter at a hotel in Hangzhou, east China's Zhejiang Province on December 26, 2018. (Photo by Sipa Asia/Rex Features/Shutterstock)

North Korean bodyguards run along a limousine transporting Kim Jong Un upon his arrival in Dong Dang, Vietnam, February 26, 2019. The second meeting of the US President and the North Korean leader, running from 27 to 28 February 2019, focuses on furthering steps towards achieving peace and complete denuclearization of the Korean peninsula. (Photo by Reuters/Stringer)

A little girl stands next to a painted buffalo during the “Buffalo Painting” contest that is part of the Tich Dien festival in Ha Nam province, Vietnam, 10 February 2019. Artists from all over the country have gathered for the festival which attracts thousand of residents and visitors. Tich Dien festival features the importance of agriculture and the role of farmers in the vietnamese society and contributes to preserving the local cultural values. (Photo by Luong Thai Linh/EPA/EFE)