McClatchy: In the world's most polluted city, a layer of smog hangs over everything, thicker year after year.
Dirty exhaust pours out of the more than seven million cars clogging the streets. Smoke from the open fires built for heating and cooking fills the air. White plumes puff steadily out of tall towers at the coal-fired power plants.
Thus, it's no surprise that after the United States and China, the world's two largest carbon emitters, reached a historic climate change deal in November, attention...