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For decades, the inevitability of many feet, even yards, of sea-level rise in a warming climate has been crystal clear. But society’s response, both in stemming heat-trapping greenhouse gas emissions and adapting to eroding coastlines, will always be more a function of the rate of change than the ultimate outcome.

That’s why it’s important to get beyond headlines — including the titles of papers — in considering new research pointing to the inevitable “collapse” of ice sheets in West Antarctica. To the public, collapse is a term applied to a heart attack victim on a street corner or a building stricken by an earthquake or bomb. To a glaciologist, it describes the transition to unavoidable loss of an ice sheet — a process that can take centuries to get into gear, and millenniums to complete.

[Insert, May 14, 6:45 a.m. | I encourage you to read two superb explanatory posts by Antarctic post-doctoral researcher Bethan Davies describing the research and glaciologists’ use of “collapse.”]

News articles by The Times, Time, the Associated Press and others capture the basics in two new papers, one on six West Antarctic glaciers that appear to have nothing holding back eventual disappearance, accepted for publication in Geophysical Research Letters, and the other taking a closer look at one of those ice masses, the Thwaites Glacier, posted online today by the journal Science.

Some headlines are completely overwrought — as with this NBC offering: “West Antarctic Ice Sheet’s Collapse Triggers Sea Level Warning.” This kind of coverage could be interpreted to mean there’s an imminent crisis. It’s hard to justify that conclusion given the core findings in the studies. (Am I trying to maintain a hold on reality or am I a “scold”?)

Take the Science paper: “Marine Ice Sheet Collapse Potentially Under Way for the Thwaites Glacier Basin, West Antarctica.” Using ice-flow models and observations, the researchers, led by Ian Joughin of the University of Washington, concluded:

Except possibly for the lowest-melt scenario, the simulations indicate that early-stage collapse has begun. Less certain is the time scale, with the onset of rapid (>1 mm per year of sea-level rise) collapse in the different simulations within the range of 200 to 900 years.

To translate a bit, that means sometime between 200 and 900 years from now the rate of ice loss from this glacier could reach a volume sufficient to raise sea levels about 4 inches (100 millimeters) a century. At that point, according to the paper, ice loss could pick up steam, with big losses over a period of decades.* But in a phone conversation, Joughin said the modeling was not reliable enough to say how much, how soon.

“Collapse is a good scientific word,” he told me, “but maybe it’s kind of a bad word” in the context of news. There’s more on this work in a well-written news release from Joughin’s university.

[Insert, May 14, 12:00 p.m. | Joughin sent this followup thought today: In defense of collapse, if I say, “The collapse of the Roman Empire,” you all pretty much understand what I mean and am talking about about a timescale similar to that for the WAIS. And I think most members of the public would too. If collapse can’t refer to extended periods such as decades to centuries, someone should contact Jared Diamond and ask him to change the title of his bestseller.

And someone should also talk to the astronomers: “The collapse to a white dwarf takes place over tens of thousands of years, (Wikipage on gravitational collapse)”. I think if we are clear about the time scales, the public is smart enough to figure out what we mean (that doesn’t mean we shouldn’t be cautious with how we word things).]

NASA has posted a heap of helpful context and description of the Geophysical Research Letters paper, written by Eric Rignot at the University of California, Irvine, and collaborators. In a NASA recording of a telephone conference call with reporters, Rignot tried to emphasize why the most familiar definition of “collapse” was inappropriate in this case:

Collapse in the imagination of most people sounds like a catastrophic event that is going to happen in the next few years. We are talking about a retreat that is unstoppable because we think we have enough evidence to say that these glaciers will keep retreating for decades and even centuries to come…. We’re talking about a slow degradation of ice in this part of Antarctica.

I particularly recommend “The ‘Unstable’ West Antarctic Ice Sheet: A Primer.” The NASA news release is clear and avoids some of the pumped-up qualities of news coverage, which is inevitably torqued by what I’ve long called “the tyranny of the front-page thought.”

Here’s an excerpt describing how the measurements on the six glaciers in the study relate to projections of sea-level rise:

These glaciers already contribute significantly to sea level rise, releasing almost as much ice into the ocean annually as the entire Greenland Ice Sheet. They contain enough ice to raise global sea level by 4 feet (1.2 meters) and are melting faster than most scientists had expected. Rignot said these findings will require an upward revision to current predictions of sea level rise. “This sector will be a major contributor to sea level rise in the decades and centuries to come,” Rignot said. “A conservative estimate is it could take several centuries for all of the ice to flow into the sea.”

So what does this mean for society? Curbing greenhouse gas emissions, and particularly the use of coal, makes sense for a host of reasons. But whatever happens on that front, there will be no new “normal” coastline for centuries to come.

For mayors of coastal cities, that means the persistent rhetoric of “we will not retreat” is a form of denial as unscientific as the stances of those saying greenhouse gases don’t matter.

Disturbingly, you can backtrack to 2009 and see a similar burst of “collapse” news around the release of two Nature papers, even though the science then also spoke of sea-level changes over millenniums. Click back to “Study: West Antarctic Melt a Slow Affair” for a bit of déjà vu.

Update, 8:03 p.m. | * At the asterisk above, I added a phrase indicating that the modeling showed abrupt and large ice losses at the discussed stage some centuries from now.