Posted on 15 June 2021 by Guest Author

This is a re-post from Yale Climate Connections by Gary Yohe and Eric Rignot

From 1900 to 2000, the ocean along the U.S. East Coast rose at twice the annual rate of the pace in the previous 19 centuries, according to a recent study from Rutgers University.

From Miami to New York to the Maldives to Venice, Italy, coastal cities worldwide know they have a lot of work to do to prepare for further sea-level rise and the flooding, erosion, and other problems it will bring.  As they plan and implement coastal adaptation options like planned retreat from the sea, researchers in the Antarctic can help them make wiser choices – if  governments provide a sharp boost in resources, and quickly.

For instance, the International Thwaites Glacier Collaboration, supported by the U.S. National Science Foundation and the UK Natural Environment Research Council, is already providing key scientific in-situ observations in critical, previously unexplored areas. But right now it is studying only one glacier for five years with overall funding of about $50 million.  The program needs much more funding to expand and intensify its work if it is to make timely progress on learning how the melting of the West Antarctic ice sheet is adding to global sea-level rise.

Meanwhile, other glaciers in East Antarctica, for instance the Totten and Denman glaciers, have started to melt away, with an even larger potential for sea-level rise than that from West Antarctica. But there is not enough funding and logistics support to investigate their local environments and determine their potential impact on future sea level.

Supporting critical needs for better local decision making

Supporting the Thwaites team and enabling additional research projects in critical sectors of East Antarctica will help give planners and policy makers much more comprehensive and coherent sets of observational scientific data over time.  The result will lead to much more reliable projections, which will be invaluable to cities and countries as they move forward with a broader effort to assess risks from climate change and put in place scalable adaptation and mitigation strategies.

Even with its current budget, the Thwaites team has been able to use innovative robotic devices to collect extraordinarily helpful data: warm water at 0 degree Celsius creeps in previously unmapped deep troughs in the sea floor and eats away the glacier at rapid rates.  Scientists for the first time learned this bad news for Thwaites once they had a chance to dip instruments beneath the compromised glacier, which satellites have diagnosed as melting away for the past 20 years. Curing the glacier from its predicament, however, is challenging given a single brief visit by experts. A fuller and extended workup is needed to give them a fighting chance to fully diagnose and take needed actions.

In the same way, better funding can help the Thwaites team answer many vital questions about the recently detected acceleration in the pace of glacial disintegration:

• Is the acceleration permanent or transient?
• Are the ocean waters surrounding the glacier warming-up and melting the glacier faster?
• How much time before the glacier retreats pass the last protecting ridge in the underlying bedrock and plunge into the deep part of West Antarctica grounded about 2.5 km below sea level?

With the current funding and staffing levels, it is difficult or impossible to answer those questions within the critical next five years.

Getting answers to these and other questions will be vital to coastal communities, many already existentially threatened.

Some of those communities  are thinking ahead about investments to protect themselves from coastal storms. In places like these, retreating or protecting too soon would be expensive, but retreating too late or otherwise delaying adaptive response courts disaster.

Places of critical importance are well known from satellites. But they also must be explored in situ using an ensemble of ocean robotic probes, ice-breaking ships, and autonomous underwater vehicles so researchers can sample ocean waters hidden beyond a thick sea ice barrier and beneath a permanent floating glacier ice cove. These are places where no human being has ever been, and reaching them is almost as challenging as making a moon landing. Scientists can do so, but only with proper equipment and investment.

The rate of retreats of glacier ice in these Antarctic environments – retreats that are the largest on the planet – are no small signal, making time of the essence.

Projecting the implications of these observations to coastlines around the world will enable more informed planning for how and when each coastal community should adapt.

The usual way to portray rising sea levels from human-induced warming involves plotting height against time for particular combinations of driving forces. These representations sometimes display cones of projected uncertainty and/or append uncertainty ranges rather than use specific dates like 2100. The figure, here, does both.

For decision-makers in places like Miami Beach, where a two-foot SLR limit has already been identified as a threshold of tolerable risk, it can be more productive to look at the corresponding distributions of the projected times when SLR will reach a specific height.

The blue distribution in the second figure reflects likelihoods of when a two-foot physical threshold for global SLR would be expected to be breached if the possibility of accelerated Antarctic ice-sheet melting were completely dismissed. The red distribution does the same with the effects of possibly accelerated melting appropriately integrated with the conventional wisdom of the blue distribution. (This is essentially what Bayesian updating does.) The shaded regions below the horizontal axis reflect unweighted 90% likelihood ranges for the two distributions; notice that they overlap.

Now consider decision-makers trying to anticipate when an investment in adaptation would best be completed. There are five cases they might consider:

1. Ignore the potential that ice-sheet melting is accelerating in Antarctica; i.e., assume that the blue distribution is correct, so TB(100/0) is the expected cost-minimizing time to complete adaptation for the 2-foot threshold.

2. Accept that ice-sheet melting is accelerating and assume that the red distribution is the correct projection of possible futures. In this case, TR(0/100) would be the targeted time for complete adaptation.

3. Use current science to give low confidence (25% likelihood) to the acceleration possibility, so hedging to minimize expected adjustment cost would be directed at TH(75/25) – later than in case 2 but earlier than in case 1.

4. New science detects an increase in the pace of ice sheet melting with enough significance that its confidence climbs to a “high” level of 75% likelihood; hedging would be directed at TH(25/75),  that is earlier than in case 3 but still later than in case 2.

5. New science does not confirm continued acceleration, so conventional wisdom would be reinforced, with increased confidence to support hedging to TH(90/10) that is earlier but close to case 1.

In the Miami example, decision makers’ two-foot tolerable risk specification requires an implicit likelihood to complete a risk calculation, so let’s assume that that is 10%. That makes the expected damage of an extreme event on $1 million worth of property after adaptation no more than $100,000. It means also that city leaders have recognized that achieving 100% protection is impossible or unaffordable. The table reports estimates of expected discounted damage based on these data calibrated in thousands of dollars per $1 million in property value.

These estimates may seem small, but they reflect discounted expected values per $1 million in current property value (with a 3% discount rate). They contrast with completely ignoring possible additional Antarctic ice-sheet melting, as in Case #1. Instead, they  show that with just a low 25% confidence in likelihood, as in Case #3, and on the basis of current knowledge, the expected discounted damage is reduced from $41,700 per million to around $23,700. The result totals nearly $300 million dollars in savings for $16 billion worth of vulnerable property distributed across a single city like Miami. 

Waiting for new science and hedging does even better. If the new data and understandings support the acceleration hypothesis, expected total vulnerability risk falls all the way down to $3.4 million. If the new science (incompletely) supports current wisdom (Case #5), the saving versus complete dismissal of acceleration is still substantial – down $33,100 per million (a citywide reduction of more than $130 million).

The unavoidable and transferable moral for Antarctica: institutions like the Intergovernmental Panel on Climate Change and the National Academies of Science, Engineering and Medicine is: 

Investments in new science that provide updated information about the likelihood of drivers for some of our most troubling sources of climate risk can largely pay for themselves, regardless of what they show about conventional wisdom, by allowing much more well-informed decision making. Planners can encourage a more leisurely pace when new evidence shows that those dangers will be delayed by a decade or two. They can also recommend earlier and more aggressive adaptation that can lower expected discounted damages when those dangers become more likely and therefore more threatening.

This lesson is not confined to Antarctic research.  Pure scientific research in many other areas like health and energy has the potential to do the same – lead to more reliable projections that will support broader efforts to assess future risks and implement scalable adaptation and mitigation strategies.

Gary Yohe is the Huffington Foundation Professor of Economics and Environmental Studies, Emeritus, at Wesleyan University in Connecticut. He served as convening lead author for multiple chapters and the Synthesis Report for the IPCC from 1990 through 2014 and was vice-chair of the Third U.S. National Climate Assessment.

Eric Rignot is the Donald Bren and Chancellor Professor of Earth System Science at the University of California Irvine. He served on the IPCC Assessment Reports 4 and 5.