Workers walk past a billboard display showing a scene of Central Business District, as pollutant haze shrouds the skyline of Beijing. China is the world's biggest source of climate-changing gases. Photo: AP
Some 45 million people in Hong Kong, Shanghai and Tianjin will be displaced as the cities slip under the waves when global temperatures rise 4 degrees Celsius if nothing is done to curb climate change, according to a study released on Monday.