Earlier this week, a thick layer of smog rolled into China’s capital city, turning skyscrapers into shadows and clear air into a yellow fog. Caught on a time lapse by Chas Pope, the smog rolls in like a dust storm in a desert, billowing into the streets of Beijing.
Smog torpedoed air quality in Beijing and 24 other Chinese cities this week, leading authorities to declare a national red alert for ‘severe fog’—the highest level of alerts, and launching environmental police force.
Why does smog keep blanketing Beijing? Smog in China has many causes, including pollution from industries and traffic, but it tends to happen more often in the winter, when plummeting temperatures cause electricity demand to soar. This pollution can come from many sources, but burning coal has been linked to the largest number of air pollution deaths in China, causing 366,000 premature deaths in 2013.
In the winter, more families are turning on their heaters—and most of the energy used to run them comes from coal-fired power plants that send tiny particles of charred dust into the air.
Those tiny particles, or particulate matter, are what turns clean air into smog. Beijing's smog woes are compounded by an accident of geography, according to AccuWeather. Beijing is bordered by the Xishan and Yanshan mountains. When a high-pressure weather system moves in, air near the city’s surface doesn't move up and over the nearby mountain ranges. It just sits there, getting more and more polluted, and residents keep breathing it in.