The bottom line? In this simulation, the ice sheet does collapse when waters beneath fringing ice shelves warm 7 to 9 degrees Fahrenheit or so, but the process — at its fastest — takes thousands of years. Over all, the pace of sea-level rise from the resulting ice loss doesn’t go beyond about 1.5 feet per century, Dr. Pollard said in an interview, a far cry from what was thought possible a couple of decades ago. He, Dr. DeConto and other experts on climate and polar ice stressed that when Greenland’s possible contribution to the sea level is added, there’s plenty for coastal cities to consider. But for Greenland, too, some influential recent studies have cut against the idea that momentous coastal retreats are likely anytime soon.Well, that's good. I have to say, though, that rising sea levels have never seemed like the scariest threat from global warming. Terrible for Bangladesh, yes, and a few other places around the world; but something that, even on the scale of hundreds of years, let alone thousands, is something to which we could adapt. The collapse of ecosystems, the desertification or aridification of productive agricultural land, and the resultant famine, mass migrations, and political instability, though - those processes will play out in a much faster, unpredictable, and destructive way.
Over all, the loss of the West Antarctic ice from warming is appearing “more likely a definite thing to worry about on a thousand-year time scale but not a hundred years,” Dr. Pollard said.