China's smog emerges from invisible cloak The "airpocalypse" that descended on Beijing last weekend blocked out the sun, filled hospital respiratory wards and brought the highest concentrations of toxic smog to the city since records began about four years ago. Air pollution in the Chinese capital has been getting steadily worse but it has been terrible for decades. The difference now is that ordinary Chinese people have an inkling of just how harmful the choking clouds are to their health and the health of their children and loved ones. This is a serious problem for Communist party general secretary Xi Jinping and his new administration as they step up to take control of the world's most populous nation. For years I have worn a black face mask like those used by cycle couriers in London and consequently endured ridicule and scorn from local residents who insisted the pea soup blanket of hazardous pollution was actually "fog" or "mist." Beijing is one of the driest big cities on earth and apart from a couple of artificial lakes and the moat around the Forbidden City it is hard to see where any mist could come from. Until just a few years ago most Chinese people had never left their country and had no experience of breathing in a clean environment so they believed the government propaganda which insisted the air was fine and getting better all the time. Air pollution measurements were either manipulated or not reported and most people just ignored the stinging in their eyes, the headaches and the sore throats and went about their lives in ignorance. Arguing with otherwise well-educated and well-informed locals about whether or not the poisonous air was safe to breathe made me feel at times like the only sane person in a society gone mad. Not any more. In the space of about two years virtually everyone in Beijing, if not much of the rest of the country, has woken up to the scale of the problem and now they want the government to fix it. In the past week even tightly-controlled state media have published scathing critiques calling for action to clean up the atmosphere. The most interesting thing about the mass epiphany is that it originated from two seemingly unconnected sources - the US embassy in Beijing and the revolution of Chinese online social media. If the US embassy had not decided about four years ago to install a monitoring station on its own roof and publicise hourly readings of fine particle concentrations in the air outside, most Beijing residents would probably still be unaware of the problem. And without the explosion in China's Twitter-like microblogs the US embassy information would probably not have reached far beyond Beijing's expat community. To their great credit, US diplomats have stayed firm in the face of intense pressure from the Chinese government, which last year went as far as accusing Washington of violating the Vienna Convention on diplomatic relations by releasing the pollution readings. Thanks to a concerted public campaign, led by a flamboyant property tycoon, the Chinese government finally agreed last year to publish its own hourly data on levels of fine air pollution particles, which are the most dangerous to human health. The biggest difference between last weekend's shockingly bad air quality and past levels of pollution is probably not the severity of the smog but rather the fact that people are no longer pretending it doesn't exist. Incoming Chinese premier Li Keqiang acknowledged the problem and said the government needed to take more action in what environmental activists called an unprecedented act of transparency. The end of denial is hugely significant but for an administration that is expected to govern for the next decade it could also be quite dangerous. The public now expects their new leaders to do something to clean up the air that is poisoning their families but as Mr Li said this week, fixing the problem will take a very long time. It will also not be easy for an autocratic government that relies on dirty coal-powered growth to raise living standards and keep the masses happy. In the age of social media, the Chinese Communist party faces a sticky dilemma - act forcefully to clean up the air and risk hurting the rapid growth that is its main source of legitimacy or do nothing and risk the wrath of its increasingly well-informed and demanding citizens.