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This combination image of two photographs taken on December 3, 2015 (top) and two days earlier on December 1 (bottom) shows pedestrians walking past buildings under clear skies and in heavy pollution in the central business district in Beijing. The skies cleared in Beijing on December 2 and 3, after being swathed in choking smog that was nearly 24 times safe levels earlier in the week. AFP PHOTO / GREG BAKER / AFP / GREG BAKER (Photo credit should read GREG BAKER/AFP/Getty Images)

This combination image of two photographs taken on December 3, 2015 (top) and two days earlier on December 1 (bottom) shows pedestrians walking past buildings under clear skies and in heavy pollution in the central business district in Beijing. The skies cleared in Beijing on December 2 and 3, after being swathed in choking smog that was nearly 24 times safe levels earlier in the week. AFP PHOTO / GREG BAKER / AFP / GREG BAKER (Photo credit should read GREG BAKER/AFP/Getty Images)
Getty Images

AFP GREG BAKER