Recent analysis of GRACE data indicate that the Antarctic ice sheet might have lost enough mass to cause the worlds' oceans to rise about .05 inches, on the average, from between 2002 and 2005. Image credit: NASA/GRACE team/DLR/Ben Holt Sr.
Sea level rise could be in the range of 39 inches (1 m) or possibly more by 2100, according to information released by the Centre for Australian Weather and Climate Research (CAWCR), with the lower end of the spectrum unlikely to be less than 20 inches (50 cm).
Thus, if global emissions of greenhouse gases are not reduced quickly and substantially, even the best case scenario will drastically affect low lying coastal areas – where one in ten people live, worldwide.
“The most recent satellite and ground based observations show that sea level rise is continuing to rise at three millimeters per year or more since 1993, a rate well above the 20th century average,” said Dr. John Church of CAWCR. “The oceans are continuing to warm and expand, the melting of mountain glacier has increased, and the ice sheets of Greenland and Antarctica are also contributing to sea level rise.”
The thinning of Greenland’s ice sheet (indicated as blue) helps scientists forecast sea level rise. Image: courtesy NASA/JPL-Caltech
New insights into causes include the loss of ice from the Antarctic and Greenland ice sheets. The ice loss in Greenland has accelerated over the last decade. The upper range of sea level rise by 2100 might be above one meter or more on a global average, with large regional differences depending where the source of ice loss occurs,” said Konrad Steffen, Director of the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado, Boulder.
“Unless we undertake urgent and significant mitigation actions, the climate could cross a threshold during the 21st century, committing the world to a sea level rise of meters,” added Church.
Rapid sea level rise exceeds projections
“Measurements around the world show that sea level has risen almost 20 centimeters (7.8 inches) since 1880,” explained Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany. Data also revealed that the rate of sea level rise is closely linked to temperature: sea level rises faster the warmer it gets.
“If sea level keeps rising at a constant pace, we will end up in the middle of that 18-59 centimeter (7-23 inches) range by 2100,” says Rahmstorf. “But based on past experience, I expect sea level rise will accelerate as the planet gets hotter.”
The impact of sea level rise – even in the lower ranges of the current predictions – looks to be severe. Approximately ten percent of the world’s population – 600 million people – live in low-lying areas in danger of being flooded. A previously released study led by Church showed that even a modest sea level rise of 20 inches (50 cm) will result in a major increase in the number of coastal flooding events.
“Our study centered on Australia showed that coastal flooding events that today we expect only once every hundred years, will happen several times a year by 2100,” Church said. “Sea level is currently rising at a rate that is above any of the model projections.”
“Different groups may come to slightly different projections, but differences in the details of the projections should not cloud the overall picture, where even the lower end of the projections looks to have very serious effects,” Steffen summed.
