A motorway bridge crosses the icy Hunhe River in Shenyang, China on December 12, 2019. (Photo by Costfoto/Barcroft Media)

A municipal worker who helped with traffic control near a school is presented with flowers at the end of the national college entrance examinations, known as the gaokao, in Beijing, Friday, June 10, 2022. More than 11 million high school students throughout China took the annual college entrance exams which started on Tuesday after the country has just overcome severe COVID-19 outbreaks in Shanghai and Beijing, according to state media. (Photo by Ng Han Guan/AP Photo)

Artists perform during a “Yandu Story” Show performance, in Yancheng, Jiangsu province, China, 20 September 2022. The story dates back to some 100 years when – according to the organizers – two prominent local families, Gu and Ling, were committed to get out of a predicament, but parted due to different development concepts and ended in a turmoil. The large-scale immersive series of performances took more than a year of careful planning and consists of two parts: a daytime performance and a 90-minute night performance, they added. (Photo by Alex Plavevski/EPA/EFE/Rex Features/Shutterstock)

Mainland Chinese tourists run along a promenade during a typhoon in Hong Kong, Monday, July 17, 2023. Schools and the stock market were closed in Hong Kong on Monday as Typhoon Talim swept south of the city. (Photo by Louise Delmotte/AP Photo)

Costumed attendees participate in the Dragon Con Parade, during the annual science fiction, pop culture and fantasy convention in Atlanta, Georgia, USA, 02 September 2023. Thousands of attendees, some costumed, crowd downtown Atlanta for the annual Labor Day Weekend gathering. (Photo by Erik S. Lesser/EPA/EFE)

Faces adorn crosses placed in the Garden of Remembrance of some of Britain's armed forces members who have died in Afghanistan in the Garden of Remembrance outside Westminster Abbey at the official opening of the Royal British Legion's Field of Remembrance on November 5, 2009 in London, England. (Photo by Alastair Grant-Pool/Getty Images)

Mazda Motor introduces the company's concept vehicle, Taiki during the press day of the 40th Tokyo Motor Show at Makuhari Messe, on October 24, 2007 in Chiba Prefecture, Japan. (Photo by Koichi Kamoshida/Getty Images)

“Contrails (short for “condensation trails”) or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets or, if the air is cold enough, tiny ice crystals”. – Wikipedia

Photo: An airplane leaves a vapor trail as it flies in front of he moon on January 17, 2007 above Hanover, Germany. (Photo by Alexander Hassenstein/Getty Images)