A young vendor hawks food on a market in Kara in the state of Ogun, on September 23, 2015. Nigeria imposed tight movement restrictions in the restive northeast after Boko Haram bombings that killed more than 100 raised fears of fresh attacks over the Eid al-Adha festival. The military said the use of all vehicles would be banned throughout Borno state during the Muslim festival, which is known as Sallah in Nigeria and marked with two days' public holiday from Thursday. (Photo by Pius Utomi Ekpei/AFP Photo)

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)

A woman carries a piglet as she runs on ice during a running challenge in Changsha, Hunan province February 8, 2015. A total of 20 people participated in the challenge requiring them to choose a pig ranging between 15 kg and 115 kg in weight, and carrying it while running on a 20.15-metre-long ice track. The participants that complete the challenge will be rewarded with the pig they carried, local media reported. (Photo by Darwin Zhou/Reuters)

Mercedes Formula One driver Lewis Hamilton of Britain sprays champagne at a grid girl as he celebrates his victory on the podium after the Chinese F1 Grand Prix at the Shanghai International Circuit, April 12, 2015. (Photo by Carlos Barria/Reuters)

A Tibetan mastiff dog is displayed for sale at a mastiff show in Baoding, Hebei province, south of Beijing on March 9, 2013. Fetching prices up to around 750,000 USD, mastiffs have become a prized status-symbol amongst China's wealthy, with rich buyers across the country sending prices skyrocketing. Owners say the mastiffs, descendents of dogs used for hunting by nomadic tribes in central Asia and Tibet are fiercely loyal and protective. Breeders still travel to the Himalayan plateau to collect young puppies, although many are unable to adjust to the low altitudes and die during the journey. (Photo by Ed Jones/AFP Photo)

A general view of the sunrise over Hawes, Wensleydale, UK on November 24, 2014. (Photo by Neil Squires/PA Wire)

Hot air balloons fly over the sky in Chiang Mai province, northern Thailand, December 6, 2014. The two-day International Balloon festival 2014 featuring balloon pilots from Germany, Spain, Netherlands, Britain, and Czech Republic is held on December 06-07 2014 to celebrate Thai King Bhumibol Adulyadej's 87th birthday and also aimed to promote the tourism industry in Chiang Mai northern city. (Photo by Pongmanat Tasiri/EPA)

Aerobatic pilot Sean D. Tucker flies in the two-seat Oracle Extra airplane over downtown Chicago skyline, Wednesday, June 8, 2016. Tucker will perform before the start of of the America's Cup World Series racing on Saturday and Sunday. (Photo by Kiichiro Sato/AP Photo)