and a smoggy day, with an AQI of more than 500. AQI stands for Air Quality Index, which technically only goes to 500. On January 29th, however, Beijing's AQI reached 517.

Photographs of Beijing on a smoggy day (June 19, 2009) and a blue-sky day (June 22, 2009), courtesy of China Air Daily. (Lin Yang and John Billingsley/Asia Society) China Air Daily, a project of Asia ...

(NOTE: This article was originally published in the India Today issue dated March 16, 2015) For two weeks in the winter of 2013, Beijingers awoke every day to poisonous, smoggy skies. There was ...