New US Military Report Shows Fallacy to Predict Future Sea Level
A new study about sea level rise and coastal risk management is excellent – cover shown below. It says that due to the uncertainty of how quickly sea level will rise, that we must abandon the normal design and engineering concept of “predict-then-act.” We must look at a range of scenarios for planning purposes, rather than fooling ourselves expecting to “know the number” with further study and facts. The report was not the product of some environmental advocacy organization. It was done by the US Department of Defense (SERDP), NOAA, the US Army Corps of Engineers, and the Oceanographer of the Navy and speaks in very clear language. From the Executive Summary:
“The decision-making paradigm must shift from a predict-then-act approach to a scenario-based approach. As a decision-maker, the fallacy and danger of accepting a single answer to the question “What future scenario should I use to plan for sea-level change?” cannot be stressed enough. Those used to making decisions based on a “most likely” future may have trouble relating to this reality; however, a variety of uncertainties, including the uncertainties associated with human behaviors (i.e., emissions futures), limit the predictive capabilities of climate-related sciences. Therefore, although climate change is inevitable and in some instances highly directional, no single answer regarding the magnitude of future change predominates. Traditional “predict then act” approaches are inadequate to meet this challenge.”
Full report @ https://www.serdp-estcp.org/content/download/38961/375873/file/CARSWG%20SLR%20FINAL%20April%202016.pdf
It is a radical challenge to the entire way that we design things. Normally we determine the probability of a future situation in order to construct buildings, infrastructure and communities. We are conditioned to study the history of such events as hurricanes, earthquakes, and tsunamis as a means to predict the probability of future events. Engineers use statistics such as “standard deviations” to describe the likelihood that an event will occur. That technique works well when there is a large number of occurrences or a large sample size as a basis for prediction, and when the baseline conditions, the “environment” — using the term in the broadest sense possible — are stable.
To look at flooding, we can use those techniques to look the pattern of storms, the extremes of the 18.6 tidal cycle, and even heavy rainfall. The major factor for sea level, however, is the size of the ice sheets on Greenland and Antarctica. There are at least 3 reasons why we cannot accurately forecast future sea level in the coming decades.
1. The last time the ice sheets and glaciers collapsed was over a hundred thousand years ago. Even looking back at those known events, the geologic record can be imprecise about the rate of rise on a year-by-year basis. In geologic terms we usually look at centuries or longer.
2. Today the rate of warming is hundreds of times faster than in millions of years, causing a different rate of melting ice and rising seas. If you double the amount of warming, you do not immediately get double the rate of ice melting. There are some non-linear aspects due to heat transfer (thermodynamics), crystalline structure of the ice, changing ocean currents, etc.
3. We are still arguing about energy policy — questions such as the continued use of coal, tar sands, natural gas, economic incentives to switch to renewable sources. Without knowing how we will make our energy in the coming decades, it is not possible to know the amount of heat being added to the Earth system, which ultimately is what changes the size of the ice sheets, changing global sea level.
The fact is that we do not have hundreds of data points to do the statistical modeling for exactly how the ice sheets and glaciers will collapse, causing sea level to rise. What we do know is that sea levels have moved up and down hundreds of feet over the eons of time in response to changing temperature. Now we are in a totally new era with an abnormal warming period that correlates closely with the heat trapping greenhouse gas levels. It is no longer possible to accurately predict future glacial collapse and sea level rise down to the inches per year.
The study specifically looks at some of the scenarios for sea level rise this century, noting a range of as much as 2 meters — about 7 feet. But even that extreme level is not the true upper boundary it notes. It makes the case that the true uncertainty for extreme sea level is impossible to quantify at the present. Even more problematic is that many planners have been using lower figures, either from analysis that is years old, and out-of-date, or simply because of our training to “predict-then-act” based on the usual stationery environment, where the baseline conditions remain unchanged, allowing us to plan for the future based on the recent past, or what we can test in the laboratory, or a proven computer model. None of those situations apply to the collapse of the miles of ice on Greenland and Antarctica. In fact over the last decade the real world events in those two locations repeatedly “blow the projections right out of the water.”
I made this same point in a post, “Inability to Predict Sea Level Rise Similar to Avalanches”. Just looking that up as a point of reference, I am stunned to see that it was exactly one year ago today, May 13, 2015.
What this excellent new study and report by various US Government experts says is that where we are planning for infrastructure such as military bases that will last decades and that cannot be easily raised or moved, that we must plan for unexpected amounts of sea level rise. We must do so using a range of scenarios covering rather extreme situations.
Those responsible for planning cities, communities, and infrastructure in the civilian environment should heed this guidance too. The signs coming out of Greenland and Antarctica in recent months are ominous. The glaciers are showing increasing signs of collapse. It would be absolutely foolish to wait for them to fully disintegrate and then try to move our facilities, infrastructure and communities to higher ground in a decade or so. Frankly it is not possible.
We must stop waiting to have the exact numbers for sea level rise as a precedent to planning and development. Accepting that we need to work with a range of projections was point #2 of my five points of “Intelligent Adaptation” in my book, High Tide On Main Street:Rising Sea Level and the Coming Coastal Crisis (Chapter 15).
The sooner we begin to adapt to rising sea level the better. We must think bigger, stepping over the recent past in order to design and build communities of the future, whether that applies to the national security or civilian environment. We need to invest in the future. This goes beyond the issues of US national security or even cities. It is a global challenge. That is the underlying message of this report that deserves a much wider audience than just those who usually read such documents. Please consider sharing this.