Mother Nature Network: China's latest spell of severe pollution can be seen from space. NASA's Terra satellite captured this image of the thick smog lingering over China, from Beijing to Shanghai, on Dec. 7. The haze is shown in gray, while the white areas represent clouds and fog, according to NASA's Earth Observatory. At the time, the Air Quality Index had climbed to 487 in Beijing and 404 in Shanghai. The scale goes up to 500, but levels above 300 are considered dangerous. Smog is the result of sunlight reacting...