Massive New Study Confirms Antarctic Ice Collapse, Even With High Emissions, is a Long Process

The study also shows that curbing heat-trapping emissions now can lead to much less sea-level rise in centuries ahead.

As you likely know, “COLLAPSE” is one of my #Watchwords - words that, too often, confuse or alarm more than inform. When this word shows up in headlines or proclamations about Antarctic ice sheets driving a runaway sea-level surge, it’s vital to ask a simple question: “By when?”

A valuable new paper written by dozens of climate and ice researchers from around the world (led by Hélène Seroussi of Dartmouth’s engineering department) reinforces why this is vital. The study, Evolution of the Antarctic Ice Sheet Over the Next Three Centuries From an ISMIP6 Model Ensemble, assessed the output through 2300 of all the leading models of Antarctic ice dynamics in a human-heated climate.

It’s one study and one should always avoid the confirmation-bias pull leading to what I call “single-study syndrome.” But this one is significant.

The key finding? Under even high carbon dioxide emission scenarios that are already seen as totally unrealistic (see Roger Pielke Jr. and Justin Ritchie and Zeke Hausfather and Glen Peters), Antarctica’s contribution to sea level rise in this century doesn’t exceed 30 centimeters (1 foot). Profound coastal challenges would mount facing multi-meter sea rise from 2200 through 2300 and beyond.

"While the sea-level contribution from the Antarctic Ice Sheet is relatively limited during the twenty-first century (less than 30 cm SLE by 2100), it increases rapidly afterward under these high-emission scenarios, reaching up to 1.7 and 4.4 m SLE by 2200 and 2300."

Of course there’s also Greenland ice loss (projected to add a few inches under the unrealistic high-emission scenarios).

Another key finding: A shift to low-emissions tracks starting now does greatly reduce sea-level rise by 2200 - 2300.

The experiments with low-emission forcing have less than 0.5 m SLE by 2300. [SLE is sea-level equivalent].

The takeaways remain the same as they ever were:

• Cutting carbon dioxide emissions now and advancing ways to capture and store CO2 at climate scale are profoundly important imperatives if those of us alive today want to limit challenges (including coastal retreats) facing generations to come.

• Cutting coastal vulnerability now is vital as well, with or without global warming (see this post and Sustain What webcast).

• Don’t be swept away by doom-slinging efforts to drive CO2 action on the basis of ice-sheet news.

If you missed my Sustain What webcast looking at the many meanings - and misinterpretations - of the word “collapse” in warnings about global warming and Antarctic ice, now’s a good time to listen.

Watchwords: For Antarctic Clarity, Explore the Meanings of Collapse

In this discussion I dove behind hot "doomsday" headlines at the time around the Thwaites glacier with Antarctic scientists Bethan Davies of Royal Holloway University of London and Karen Alley of the University of Manitoba and Rob Larter of the British Antarctic Survey, both of whom are on the International Thwaites Glacier Collaboration.

Also joining was longtime climate journalist Jeff Goodell of Rolling Stone, who visited the Thwaites glacier in 2019 and has written in depth on sea-rise and ice melt.

This point made by Davies (which I’ve posted before and will post again) remains critically important to absorb and recall as you see further news on melting ice and rising seas:

Here’s a visual to share any time you see collapse used in a way that confuses more than informs:

Postscript - Watch this helpful video featuring the paper’s lead author Hélène Seroussi: Dartmouth Engineering Professor Studies Ice Sheets to Predict Sea-Level Rise