Workers walk through an archway on a pol...

Xian, CHINA: Workers walk through an archway on a polluted day depicting Shaanxi Opera set up for Lunar New Year festivities along the south gate city wall, 08 February 2007 in Xian, in northwest China's Shaanxi province. Imperial China's ancient capital of Xian was the starting point for the great camel caravan trade known as the Silk Road, which brought precious silk, spices and technologies westward toward India, Central Asia and beyond going back some two thousand years. China, which celebrates the arrival of the Year of the Pig on 18 February, has no plans to radically change its reliance on coal and other dirty fuels despite already feeling the impacts of global warming, a leading Chinese meteorologist said 06 February. AFP PHOTO/Frederic J. BROWN (Photo credit should read FREDERIC J. BROWN/AFP via Getty Images)