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We need a plan for inevitable sea level rise

Planning for sea level right is hard but it's beyond necessary.

An example of sea level rise in Monaco, New Zealand

An example of sea level rise in Monaco, New Zealand.

Excerpted with permission from "Moving to Higher Ground: Rising Sea Level and The Path Forward" by John Englander. Copyright 2021 by John Englander. All rights reserved. This book is available wherever books and ebooks are sold. The above is an affiliate link and we may get a small commission if you purchase from the site.

Moving to Higher Ground book cover. Ocean and sky in background with word that read 'Moving to Higher Ground' and 'John Englander'

It even surprises many experts to learn how severely the IPCC understates projected sea level rise (SLR). Paradoxically, the omission is due to their good science and rigorous discipline. Since they can’t agree on exactly how much Antarctic melting will contribute to ocean volume this century, they have effectively used an asterisk. The uncertainty is covered in a footnote to the huge report that few read. Many scientists agree with my belief that the report presents the case for rising sea level poorly. Even highly respected research companies and government organizations around the world often look only to the IPCC’s top-line figure of less than about 3 feet as the worst-case scenario for future sea level this century. Often they don’t notice that Antarctica — which holds 88 percent of potential SLR — is largely omitted from the projections. While I appreciate their dilemma and their wish to follow protocol, it is dangerously misleading. 

To be specific, the IPCC assessment runs four scenarios for climate change, ranging from a "best case" with drastic reductions in greenhouse gases and global warming (RCP 2.6) to the "worst case," business-as-usual, largely following our current path of growth, consumption and increase in greenhouse gases and temperature (RCP 8.5). In that upper-end scenario, their top-line figure for global sea level rise by the end of this century is 32 inches. That figure is the most commonly referenced figure in the world for future sea level. In their worst-case scenario, with global average temperature warming almost 9 degrees Fahrenheit by 2100, it includes just 6 inches of sea level rise from Antarctica. As mentioned in the last chapter, that’s out of a potential 186 feet of sea level contribution from the southern continent. That 6 inches is not at all representative of what the glaciologists believe to be at stake. Think of it more as a placeholder until we have better information. I call it the "Antarctic Asterisk."

There are other projections for worst-case sea level rise, higher than the IPCC’s. Recent studies from 2017 to 2019 by the U.S. government, the British government, California and New York state are all looking at high-end scenarios of 8 to 10 feet for SLR this century. They are able to change their protocols more easily than the huge international IPCC. Still, they are unable to answer the question of the probability of such a worst case. That comes back to the unpredictability of the rate of warming in the coming decades and the mysteries of glacial collapse. 

Definition of Antarctic Asterisk. It reads. "The IPCC Report and the understated sea level projections are explained in Deeper Dive Note #6 in the online material at The previously cited Deeper Dive Note #2 gives more information about Antarctica, and possibly more up-to-date information."

Unfortunately, it’s not realistic to wait to adapt to rising sea level until we know precisely how high and how soon it will rise. As with anticipating earthquakes or pandemics, we need to plan for rising sea level and flooding without knowing the specific timing or the magnitude. While that may seem overly cautious, we fully accept unpredictability when it comes to planning for other risks. For example, no one doubts there will be another severe earthquake in the San Francisco area, perhaps even worse than the famous 1906 quake rated to have been a 7.9 magnitude. Yet we have no idea when the next one will occur. Even with hundreds of strain gauges monitoring the fault lines, the guidance for building codes and construction is essentially: There is a 10 percent chance of a magnitude 8.0 or greater seismic event in the next 50 years in the Bay Area. Could that be more vague? Yet that’s the basis for their planning, engineering, architecture and emergency response. We plan and design for another big earthquake in San Francisco and in dozens of other places around the world where there are active fault lines and zones of tectonic plate convergence, despite having no idea when it will occur or what its magnitude will be. 

Making the challenge of planning for SLR even harder is the fact that the estimates vary hugely. Let’s take a closer look at why it is difficult to project the rate of SLR from melting ice sheets. Visualize an ice cube on a table. How many seconds it will take to melt depends on many factors: temperature in the room, air currents, the closeness of your body heat and exhalation, and the density of the ice — which varies with the pressure where it was formed. Size also matters, though even ice cubes from the same freezer tray will often melt at slightly different speeds. Predicting the potential rate of melting of the two gargantuan ice sheets and glaciers is both similar and far more complicated, given that we are talking about ice sheets the size of North America, which are miles thick, working their way over the rough, mountainous terrain of Alaska, Greenland and Antarctica. When ice is more than 150 feet thick, it deforms rather like modeling clay. Referred to as plasticity, that bending and reshaping greatly affect the time it takes for the gigantic glaciers to reach the sea, breaking off as new icebergs or becoming rivers of meltwater, the two primary causes of future SLR. 

John Englander was recently on the GreenBiz 350 podcast. Listen to the interview on Episode 261: Sea changes, strategy shifts.

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