My colleague Thomas in Beijing took these two photos in Beijing last January. They are from the same location at the same time of day.
The one on the left was taken on 3 January 2012. Air Pollution Index (API) was 46. One week later he took the photo on the right – that day the API was 494.
Spare a pitying thought for the millions in Beijing today as API soars above 900.
Take care Tom!