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)
Samburu women of the Lorubai traditional dance group are seen wearing traditional beaded necklaces during a Peace Marathon for pastoralist communities at the Archers post in Isiolo, Kenya on April 26, 2018. The aim of the event is to bring the warring pastoralist communities of Samburu, Turkana, Borana and others together, and end the rivalry due to scarcity of pasture and water in the region. The peace marathon is organized by Kenya's Northern Rangeland Trust. (Photo by Simon Maina/AFP Photo)
A citizen rides in smog on December 20, 2016 in Jinan, Shandong Province of China. Air quality index (AQI) readings exceeded 400 and some schools have suspended classes in Jinan. (Photo by VCG/VCG via Getty Images)
Fire fighters, emergency service vehicles and a helicopter in Moskovsky Prospekt at the entrance to Tekhnologichesky Institut station of the St Petersburg metro in the aftermath of an explosion which occurred in a train at 14:40 Moscow timeon April 3, 2017. (Photo by Peter Kovalev/TASS)
A woman cries as she stands next to house destroyed by the earthquake in the Pacific coastal town of Pedernales, Ecuador, Sunday, April 17, 2016. A magnitude-7.8 quake, the strongest since 1979, hit Ecuador flattening buildings, buckling highways along its Pacific coast and killing hundreds. (Photo by Dolores Ochoa/AP Photo)
Participants pose as they take part in a bodybuilding and fitness event named “China Fit”, in Beijing, China, June 15, 2016. (Photo by Reuters/Stringer)
In this September 1, 2016 photo, 90-year-old street vendor Antonio Bauza waits for tourists to sell his bananas, next to the village church in Remedios, Cuba. With the arrival of the first commercial flights from the U.S. to Cuba in more than 50 years, the Cuban government is welcoming the wave of new visitors and struggling to update infrastructure that's already overwhelmed. (Photo by Ramon Espinosa/AP Photo)