10+ feet of sea level rise

East Antarctic glacier.  Source: EcoWatch

From EcoWatch:

A section of the East Antarctic Ice Sheet that contains three to four meters (approximately 10 to 13 feet) of potential sea level rise could melt if temperatures rise to just two degrees above pre-industrial levels, a study published in Nature Wednesday found.

Researchers at Imperial College London, the University of Queensland, and other institutions in New Zealand, Japan and Spain looked at marine sediments to assess the behavior of the Wilkes Subglacial Basin during warmer periods of the Pleistocene and found evidence of melting when temperatures in Antarctica were at least two degrees Celsius above pre-industrial levels for periods of 2,500 years or more.

"With current global temperatures already one degree higher than during pre-industrial times, future ice loss seems inevitable if we fail to reduce carbon emissions," Imperial College researcher Dr. David Wilson said in a University of Queensland press release published by ScienceDaily.

The East Antarctic Ice Sheet has been considered less susceptible to melting than the West Antarctic Ice Sheet because its basin is largely above sea level, but the Wilkes Subglacial Basin is below sea level and therefore more vulnerable, University of Queensland researcher Dr. Kevin Welsh said in press release.

"The evidence we have suggests that with the predicted two degrees Celsius warming in Antarctica—if sustained over a couple of millennia—the sheet would start melting in these locations," Welsh said.

During one of the periods studied, around 125,000 years ago, sea levels were 20 to 30 feet higher than they are now, The Washington Post reported.

University of California at Irvine glaciologist Isabella Velicogna, who was not involved in the study, told The Washington Post that it "contributes to the mounting pile of evidence that East Antarctica is not as stable as we thought."

[Read more here]

But why are we worrying about what will happen over the next millennium?  One answer is that we're stewards of the Earth and should look after her.  Another is that it might happen more quickly: 

Wilson told The Washington Post that the earth could see temperatures this century that would be warm enough to start the melting process eventually, but the study did not indicate how fast or slow that process would be.

"What we definitely can say is that during the [geological] stages where temperatures were warm for a couple of degrees for a couple of millennia, this is where we see a distinct signature in our records," Wilson told The Washington Post. "We can't necessarily say things didn't happen quick, but we can't resolve that in our data." 

Yet another is that this is the East Antarctic ice sheet, which had been thought to be more stable than the West Antarctic sheet. 

Even if we stop emitting CO2 over the next 30 years, global temperatures, which are rising by 0.2 degrees C every decade will still rise another 0.6 degrees and likely keep on rising by perhaps another 0.4 after CO2 emissions stop because of the thermal inertia of the oceans.  So 2 degrees is in the bag.  So therefore is 3 or 4 metres of sea level rise, even if it takes decades or centuries.  And that assumes we do something about CO2 emissions.  I think we will, but will we really?