NOAA just published this satellite picture of China, which shows just how bad its smog problem really is. This week the smog was so bad it shut down Harbin, a city of 11 million people.

Small particulate matter (with a diameter of 2.5 micrometers) reached a reading of 1,000 in some parts of Harbin. More than 300 is considered "hazardous," and the city has been forced to shut down schools, airports, and buses because of the air.

NOAA notes:

The heavy smog is caused by industrial pollution, coal and agricultural burning, and has been trapped by the mountains to the west and wind patterns. The thick haze of smog is clearly visible as the murky grey color in this true color VIIRS image from the Suomi NPP satellite, taken on October 22, 2013 at 05:30 UTC.

The gray areas on the image are the smog: