A Chinese man wears a mask to protect against pollution as he waits at a red light while commuting to work in heavy smog on December 8, 2015 in Beijing, China. The Beijing government issued a 'red alert' for the first time since new standards were introduced earlier this year as the city and many parts of northern China were shrouded in heavy pollution. Levels of PM 2.5, considered the most hazardous, crossed 400 units in Beijing, lower than last week, but still nearly 20 times the acceptable standard set by the World Health Organization. The governments of more than 190 countries are meeting in Paris to set targets on reducing carbon emissions in an attempt to forge a new global agreement on climate change. (Photo by Kevin Frayer/Getty Images)

In this July 5, 2016 photo, a tamed elephant rests in a pool of water by a road in Baduraliya, a village outside Colombo, Sri Lanka. Even as the country cracks down on illegal ownership, the enduring demand for elephants has the government planning to set up its own pool of captive animals to be hired out to temples for ceremonies and maintained with budget funds. (Photo by Eranga Jayawardena/AP Photo)

Plaster cast moulds of victims of the Mount Vesuvius eruption lie on a display table in a laboratory at Pompeii October 13, 2015. An expert team made up of archaeologists, radiologists, orthodontists and anthropologists began on September 2015 to use CAT scan technology (computerised axial tomography) to peer inside the plaster cast moulds of Pompeii's victims, in a study that has added more detail to previous findings. A 16-layer scan had to be used in order to penetrate the hardened plaster but the results showed up impressive skeletal remains and near perfect teeth. (Photo by Alessandro Bianchi/Reuters)

Passengers wait at the departure hall of the Beijing Railway Station in central Beijing, China January 27, 2017 as China gears up for Lunar New Year, when hundreds of millions of people head home. (Photo by Damir Sagolj/Reuters)

Michelle Wie of the USA lines up a putt on the second hole during the final round of the HSBC Women's Champions on the Tanjong Course at Sentosa Golf Club on March 5, 2017 in Singapore. (Photo by Scott Halleran/Getty Images)

A picture taken on March 16, 2017 shows women dressed up as mermaids posing by a pool at a mermaid training school in Moscow. Russian women who have dreamt of becoming a mermaid since their youngest years, start turning their fantasies into reality with a new type of fitness – mermaid swimming. (Photo by Natalia Kolesnikova/AFP Photo)

A worker lifts up tiles during a bodybuilding contest for tile factory workers as part of celebrating Indonesia Independence day at Jatiwangi village in Majalengka, Indonesia West Java province, August 11, 2017. Indonesia Independence day is on August 17, 2017. (Photo by Reuters/Beawiharta)

Dancers of the Czech National Ballet warm up backstage during a performance of “The Nutcracker – A Christmas Carol” at the National Theatre in Prague, Czech Republic, late 16 December 2017. Peter I. Tchaikovsky's “The Nutcracker”, one of his most famous compositions and seasonal ballets, premiered in St. Petersburg, Russia, on 18 December 1872, celebrates its 125th anniversary this year. (Photo by Martin Divisek/EPA/EFE)