A combo shows visitors standing next to a paramilitary policeman as they visit the Tiananmen Square on...
A combination photo shows visitors standing next to a paramilitary policeman as they visit the Tiananmen Square on a smoggy day on December 1, 2015 (top), and on a sunny day on December 2, 2015 (bottom), after a fresh cold front cleared the smog that was blanketing Beijing, China. REUTERS/Damir Sagolj