APEC blue is gone. Smog is back.

Blue skies did not last long over Beijing after the Asia-Pacific Economic Cooperation conference from Nov 5 to 11. The capital and its neighboring provinces are once again shrouded in severe smog, primarily because of central heating in North China that requires burning huge amounts of coal.

APEC blue, a term coined by some Chinese netizens to describe Beijing's clear skies during the APEC week, was the result of both compulsory measures and favorable meteorological conditions. During the weeklong conference, emission-heavy production in Beijing and its neighboring provinces and cities - including Tianjin municipality, Hebei, Henan and Shandong provinces - was suspended and half the cars were forced off the roads because of the odd-even license number driving rules. Plus, the weather condition in Beijing at the time was relatively conducive to dispersing air pollutants.