20th century saw unprecedented rise in sea levels

A Rutgers University study has found that global sea levels rose faster in the 20th century than in the 27 centuries before.

Published in the Proceedings of the National Academy of Sciences, the study found that the global sea level rose by 14 centimetres from 1900 to 2000. For low-lying coastal areas it is a substantial increase that can make them vulnerable to inundation..

“Notably” the study also found that global sea level declined by about 8 centimetres during the cold period in the Middle Ages from around 1000 to 1400. During that time the planet cooled by about 0.2 degrees C.

Robert Kopp, the lead author of the study, said: “It is striking that we see this sea-level change associated with this slight global cooling. By comparison, global average temperature today is about 1 degree Celsius higher than it was in the late 19th century.”

The research was done by compiling a new database of geological sea-level indicators, including marshes, coral atolls and archaeological sites from the last 3,000 years. It used records from 24 locations around the world, and 66 tide-gauge records from the last 300 years.

Kopp collaborated with Klaus Bittermann and Stefan Rahmstorf at the Potsdam Institute for Climate Impact Research in Germany.  Academics from the University of York in the U.K. and the Woods Hole Oceanographic Institution also participated.

The study found that: “without global warming, 20th century global sea-level change would very likely have been between a decrease of 3 centimetres and a rise of 7 centimetres.”

To read the news report on phys.org, click here.