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.

Major cities across eastern China are sinking due to groundwater extraction and the weight of buildings, potentially exposing millions of people to flooding and damage in the next 100 years.

Nearly half of China's major cities are suffering "moderate to severe" levels of subsidence, putting millions of people at risk of flooding especially as sea levels rise, according to a study of nationwide satellite data released on Friday.