On a visit to China a few years back, I asked a local official about pollution controls after enjoying my first sour, gritty taste of the country's air. China’s new coal-fired power plants and other industrial boilers often came equipped with expensive scrubbers to clean acid rain and smog-forming sulfur dioxide out of the hot mix of gases that went up and out the smokestack. But the scrubbers required energy to run, this official noted, and therefore were shut off except on days when dignitaries (or foreign journalists) visited.

According to Hu Tao, an ecologist and environmental economist who directs the China program at the World Wildlife Fund, not much has changed. On his recent visit to a coal-fired power plant, the scrubber was turned off for "inspection," he explained at a talk at the Woodrow Wilson Center's China Environment Forum on November 24. How often were such machines inspected, Tao inquired? Well, if no one from the government was visiting, the plant manager told him, the machine is turned off every day.

That is the current context for China's recent decree that the country will never consume more than 4.2 billion metric tons of coal per year, the action following a historic agreement with the U.S. to begin to combat climate change. Already, caps on the amount of coal a given locality can burn seem to have dropped coal's share of total energy in China for the first time in the 21st century, though overall it has tripled since 2000. "The vast majority of China's CO2 emissions are a result of coal combustion," said Jake Schmidt, director of the Natural Resources Defense Council's international program at the CEF event.

If the central government's cap is achieved, then China's carbon dioxide emissions would never top 12 billion metric tons per year or so—up from roughly 10 billion metric tons per year as of now. Already, China's coal burning alone accounts for 20 percent of the entire world's CO2 pollution.

For comparison, the U.S. emits slightly more than 5 billion metric tons of CO2 per year these days. And if the recent pledges hold firm, the American and Chinese lifestyles would converge at a pollution level of roughly 10 metric tons per person by 2030.

This is a tall order. To achieve such a halt in coal consumption, China will have to build as much wind, solar, nuclear and hydropower in the next 10 years as it has built coal-fired power plants in the last 10 years—as much as 1000 gigawatts worth of alternatives to coal, also including natural gas, whether pipelined from Russia or fracked out of the country's own shale deposits. And even if that dream is realized, an International Energy Agency analysis suggests such a build out, though possible, is not sufficient to slow rising coal consumption unless China's economic or electricity use growth also slow significantly. To truly get China's CO2 pollution problem under control will require yet more technology, such as CO2 capture and storage, to clean up the emissions from existing coal-fired power plants.

The question is: once that technology is installed, will it be turned on?

Coal is cheap and getting cheaper in China. In fact, though the country may require more and more coal imports to satisfy its voracious demand, the cost of coal is cheaper now than in 2000, according to an analysis by WWF's Hu. As a result, the owners of coal-fired power plants can still make money burning the polluting rock to generate electricity—and even more money if they keep pollution controls in the off position. Local governments have few reasons to complain (unless the provincial or central government steps in) given the resulting economic growth, increasing number of jobs and tax revenue. As a result, China's carbon intensity—the amount of CO2 produced per unit of economic output—has stopped declining in recent years, thanks mostly perhaps to the unprecedented boom in burning coal to make cement and steel to build China's burgeoning cities and infrastructure. "For the companies, one side is low coal price and the other side is coal cap regulations. Which one should they follow?" Tao asked, noting that a carbon tax could solve this conundrum decisively. "One says use more and one says use less."

The real crisis in China is not invisible CO2 but the more visible kind of air pollution, which, in addition to killing people prematurely, is obscuring entire cities. The joke the last time I visited China was that the smog shielded the country from U.S. spy satellites but the truth is that cities like Beijing, Jinan, and Shenyang suffer from soot and smog in the air at levels at an air quality index level above 200 on some days. The central government considers anything below 100 to be a "blue sky day" though the World Health Organization recommends the AQI should never go above 20 (the U.S. and Europe also fail to meet that standard). "If you live in Beijing, it doesn't matter if you are poor or rich, you cannot avoid air pollution," Schmidt noted.

As a result, air pollution has become a central focus of the central government—and the country's prime minister Li Keqiang went so far as to declare a war on it. "Air pollution has become one of the most important issues facing China today, both for social stability and also international reputation," said Barbara Finamore, NRDC's Asia director and Beijing resident, in a conference call with reporters on November 6. "Efforts to drive air pollution down are having very beneficial impacts on coal use."

WWF's Hu suggests the best way to reduce coal use even further is to make sure the price goes up by imposing the equivalent of a carbon tax—and the central government is considering a countrywide price on CO2 as part of a national cap and trade market in greenhouse gas pollution in coming years. Such a program might also give the central government a better chance of seeing what's actually happening with coal use and pollution control at the local level. "If we don't reduce coal consumption, we have no way to reduce PM 2.5," or particular matter of 2.5 microns smaller, more commonly known as soot, added Yang Fuqiang, NRDC's senior advisor on energy, environment and climate change in Beijing, at the CEF event.

But battling soot does not necessarily mean curbing CO2 pollution as well. One solution for air quality in a city like Beijing is to move factories and other coal-fired industry out of the city or to turn coal to gas or liquids before burning it, which reduces the soot choking lungs but results in even more CO2 pollution than just burning the coal directly. "There is a real potential for shifting coal use in China from most polluted regions inland, which is why a national cap on coal consumption that's mandatory is so important," Finamore said.

At the same time, regions in the west of China may now rush to build coal-fired power plants and industry before any national efforts take effect. "We give a warning to the western regions, you have to set up coal right now," Yang said. "In the future, it is too late."

In short, how China actually grows its energy system in the next decade or so will determine whether or not the world has any real hope to combat climate change. If the Chinese dream does include a good environment, as China's President Xi Jinping has said in the past, then a transformation even more remarkable than the one the country has undergone in the last 25 years will be required. And that means turning the pollution controls on for good.