Smog hangs over Beijing's main boulevard, Chang'an Avenue, looking west toward the Forbidden City, on Monday, Nov. 30, 2015. Although the city is cracking down on dirty vehicles and some power plants, the smog of the last week has demonstrated Beijing's pollution-control efforts have yet to produce lasting results. It comes as Chinese President Xi Jinping is in Paris pledging that China will reduce emissions linked to global climate change. (Stuart Leavenworth/McClatchy/TNS)
