Sea level rise is accelerating: PNAS study

A new report in the US-based Proceedings of the National Academy of  Sciences (PNAS) journal released Monday, says sea level rise is acceleratingand could reach 66 centimeters (26 inches) by the end of the century.

The projected rise is in line with UN estimates and would be enough to cause significant problems for coastal cities.

According to the report, the past annual rate of sea level rise — about 3 millimeters (.1 inch) per year — may more than triple, to 10 millimeters per year by 2100.

"This acceleration, driven mainly by accelerated melting in Greenland and Antarctica, has the potential to double the total sea level rise by 2100 as compared to projections that assume a constant rate — to more than 60 centimeters instead of about 30," said the author of the study, Steve Nerem.

"And this is almost certainly a conservative estimate," added Nerem, who is a professor of aerospace engineering sciences at the University of Colorado in Boulder.

The report, which is based on 25 years of satellite data, said the findings were "roughly in agreement with the Intergovernmental Panel on Climate Change's 5th Assessment Report (AR5) model projections."

Anny Cazenave, director of earth science at the International Space Science Institute in France, said sea level rise was a better gauge of climate change in action than temperature. Cazenave, who is one of the pioneers of space-based sea level research, edited the study.

How climate change affects sea levels

Climate change leads to rising sea levels in two ways. First, higher concentrations of greenhouse gases in the atmosphere boost the temperature of water and warm water expands.

Nerem said thermal expansion of the oceans had already contributed to about half of the 7 centimeters of average global sea level rise in the past quarter century.

Second, ocean levels rise with the increasing flow of water from rapidly melting ice at the poles.

Global sea levels were stable for about 3,000 years, said climate scientist Stefan Rahmstorf, of the Potsdam Institute in Germany. It was in the 20th century that they started rising and then accelerated due to global warming caused by the greenhouse gas emissions through burning fuels like coal, oil and natural gas. Rahmstorf wasn't part of the study.

Read more: Four climate change myths, debunked

"This study highlights the important role that can be played by satellite records in validating climate model projections," said a co-author of the study, John Fasullo, a climate scientist at the National Center for Atmospheric Research.

Co-authors on the study came from the University of South Florida, NASA Goddard Space Flight Center, Old Dominion University and the National Center for Atmospheric Research.

av/se (AFP, AP)