Tuesday, January 20, 2015
A Rutgers and Harvard study published in the journal Nature says a recalculation of sea level numbers indicates that the rate of sea level rise is accelerating.
And other studies suggest massive melting in both Greenland and West Antarctica are partly at fault.
The Rutgers-Harvard study says sea level was rising at 1.2 millimeters a year from 1901-1990—less than previously estimated. That works out to about an inch every 20 years. But in the past two decades, 1993 to 2010, the authors say, it has speeded to 3 millimeters per year, or more than an inch a decade.
With classic scientific understatement, they say “The increase in rate relative to the 1901–90 trend is accordingly larger than previously thought; this revision may affect some projections of future sea-level rise.”
The paper, by Carling Hay, Eric Morrow, Robert Kopp and Jerry Mitrovica, is entitled, “Probabilistic reanalysis of twentieth-century sea-level rise.”
That paper confirms earlier work by other researchers that suggests sea level rise is speeding up dramatically. One of those papers was a 2012 report in the journal Environmental Research Letters, which suggested sea level rise was 60 percent higher than the Intergovernmental Panel on Climate Change was projecting, at 3.2 millimeters per year.
Perhaps one reason for the increase is found in another study just released, which suggests that increased warming results in much increased melting on the Greenland ice sheet.
Why is that an issue? Because there is enough ice on Greenland to raise ocean levels 24 feet. Think virtually every coastal city flooded yards deep. Just one yard would displace a billion people. This study is in the journal Climate Dynamics. The authors are Pennsylvania State University’s Patrick J. Applegate, and Byron R. Parizek, Robert E. Nicholas, Richard B. Alley and Klaus Keller.
“Satellite observations and paleo-data suggest that the Greenland Ice Sheet loses mass in response to increased temperatures, and may thus contribute substantially to sea level rise as anthropogenic climate change progresses,” they write.
Another source of sea level rise is the collapse of the West Antarctic ice sheet. Papers in Science and Geophysical Research Letters in mid-2014 suggested that sections of the West Antarctica ice sheet have been collapsing.
One of those studies concluded “the average rate of ice thinning in West Antarctica has...continued to rise, and mass losses from this sector are now 31% greater than over the period 2005–2010.”
The Jet Propulsion Laboratory of the California Institute of Technology has a release on another paper on the issue here.
Glaciologist Eric Rignot, of JPL and UC Irvine, said the Antarctic ice sheet collapse may now be unstoppable. There’s about 4 feet of sea level rise represented in the ice sheet.
"This sector will be a major contributor to sea level rise in the decades and centuries to come," Rignot said
A common theme in some of the papers cited above is that the Intergovernmental Panel on Climate Change may be too conservative in its estimates of how bad sea level rise could be. In fact, the evidence suggests it may be rising lots faster than earlier estimates suggested.
© Jan TenBruggencate 2015