Photo Smog returned to Beijing after emergency measures to clear the air during the Asia-Pacific Economic Cooperation summit meeting were lifted. Credit Fred Dufour/Agence France-Presse — Getty Images When Beijing experiences bouts of pollution that blacken the skies and burn the lungs, residents often joke that the Chinese capital needs to build giant fans to clear out the toxic air. Mountains to the north and west help trap smog in the city, and a stiff breeze from Mongolia is the surest way to ensure somewhat cleaner air. Beijing officials are now considering ways to help that process. Though giant fans are not on the menu, at least not yet, city planners are looking at ways to create corridors that encourage wind flow through the capital. The plan is inspired by research on urban heat islands, which shows that large buildings that block the wind are one of the causes […]