This picture taken on January 22, 2013 shows a thermal power plant discharging heavy smog into the air in Changchun, northeast China's Jilin province. China has cleaned up its air before but experts say that if it wants to avoid the kind of smog that choked the country this week, it must overhaul an economy fuelled by heavily polluting coal and car use.  CHINA OUT     AFP PHOTO (Photo by STR / AFP)        (Photo credit should read STR/AFP/Getty Images)