Last Saturday an air pollution monitor atop the U.S. Embassy in Beijing rated the pollution index at a shocking 755--on a scale of 0 to 500. (The EPA categorizes pollution levels over 300 as "hazardous.") A Time reporter wrote that the view from her 16th floor Beijing apartment was "akin to a sandstorm in Afghanistan." Even China's official People's Daily ran a front-page story on the appalling haze, calling it a "suffocating siege." My Beijing colleague Jingjing Qian said that mai, or smog, once a rarely-used word in Chinese, has been the talk of the town.

 CCTV building thick with air pollution

CCTV building, Beijing (courtesy Anthony Suen)

Dozens of cities in eastern China reported record-breaking levels of pollution last week. Children stayed indoors, while others only ventured out in masks. During the smog's peak, hospitals reported an uptick in patients with respiratory and heart complaints. This NASA satellite photo, in which grayish-brown smog completely blots out the cities of Beijing and neighboring Tianjin, was taken after the pollution began to dissipate.

air pollution across a wider area of china beijing region

NASA Earth Observatory

Weather conditions certainly played a role in trapping the smog above Beijing's flat plain, but the source of the pollution itself is entirely human--created, in large part, by the burning of coal. Since my last visit to China, when the never-ending haze left a metallic taste in my mouth, the Chinese government has taken steps to cut power plant pollution, improve environmental monitoring, and strengthen the transparency of environmental information. This newfound transparency has helped fuel the unprecedented, and largely critical, coverage on the smog by the Chinese media.

All this is important progress. But to prevent the occurrence of another "airpocalypse" in China, this transparency needs to spark more aggressive action to curb air pollution from coal, cars, and factories. China needs to continue to strengthen and monitor emissions standards for power plants and industrial facilities, accelerate the shift away from polluting industries, expand public transit and walkability in cities, and take steps to clean up its dirty diesel trucks and buses, which contribute huge quantities of particulate soot to Beijing's air. And possibly the most critical step China can take to clear its air will be to put a cap on the amount of coal it burns.

In 2011, China consumed 3.6 billion tons of coal--half the world's total consumption. And that number continues to rise. Significant progress on energy efficiency (NRDC has been working on this for more than a decade in China) and the expansion of renewable energy could reduce coal's share of total energy consumption by as much as 10 percent by 2020, according to an LBNL study. But total energy use in China is still on the upswing, which means total coal consumption--and emissions--will also rise.  

Continuing to burn billions of tons of coal each year, without adequate pollution controls, endangers not only the health of Chinese citizens, but also the health of the planet. Coal is a leading source of greenhouse gas emissions, and scientists warn that without effective, global action to curb this pollution, we are propelling ourselves toward catastrophic climate change. China, by virtue of its size and the rapid increase in its emissions from coal, can play an important global role in reducing the risk of severe climate impacts--and improve its own local air quality-- by moving quickly to reduce its reliance on coal.

China's CO2 emissions rose by about 9 percent in 2011, according to the IEA, largely due to increasing coal consumption. Continued growth at this pace will make it very difficult to keep global warming in check, especially as the world struggles to find ways to keep the warming needle under 2 degrees Celsius, the point beyond which, scientists say, we risk extreme environmental and societal disruption.

That's a fairly dire outcome. But no amount of scientific modeling is as compelling as a thick blanket of brown, soupy air smothering your capital; or the voice of your people who are tired of getting sick from pollution. This could be China's Cuyahoga moment: when an instance of pollution so severe, like the river that caught fire outside Cleveland in 1969, moves the people, and the government, to action. China has set soft targets for coal consumption in the past, but these are routinely, and overwhelmingly, exceeded. By setting a mandatory, enforceable cap on coal, China can make its air and water cleaner and its people healthier. It can also help the world steer clear of climate disaster