About 6 percent of land in China’s coastal cities currently has a relative elevation below sea level. If the global average sea level rises by 0.87 meters, or a little less than 3 feet, by 2120 (the higher of two commonly used scenarios considered by the researchers) that proportion could rise to 26 percent, this study found.

Nearly half of China's major cities are sinking because of water extraction and the increasing weight of their rapid expansion, researchers say. Some cities are subsiding rapidly, with one in six exceeding 10mm per year.

The pair note that traffic vibration and tunnelling is potentially also a local contributing factor – Beijing has sinking of 45mm a year near subways and highways. Natural upwar