Sea Level Rise by Gary Walsh

“The sand erosion we are witnessing along San Clemente’s beaches is not the result of Sea level Rise.”

- Dr. Brett Sanders, University of California, Irvine, Professor of Civil and Environmental Engineering

SLR is exactly like it sounds – the level of the seas are rising.  According to The National Oceanic and Atmospheric Administration (NOAA) (a science-based federal agency within the Department of Commerce): “Global mean sea level has risen about 8–9 inches (21–24 centimeters) since 1880”, and additionally: “In 2022, global mean sea level was 101.2 millimeters (4 inches) above 1993 levels, making it the highest annual average in the satellite record (1993-present).”  

What is causing SLR?  According to NOAA: “The rising water level is mostly due to a combination of melt water from glaciers and ice sheets and thermal expansion of seawater as it warms.”  NOAA then connects the dots as to why the glacial ice caps are melting is due to “global warming.”  NOAA continues: “As global temperatures continue to warm, additional sea level rise is inevitable.”

It all sounds pretty dire and certain.  What this 2022 NOAA report doesn’t address is whether this has happened before.  It has.  The earth today is in the Holocene interglacial (melting period), which geologists deem to have started about 12,000 years ago. According to the geological record, SLR has risen by about 400 feet since the Last Glacial Maximum (when the continental ice sheets reached their maximum total mass during the last ice age).  Accurate records of the sea level has only occurred over the past 140 years or so.  A quick examination over that period shows a slow but steady increase, but also reveals those levels dropped in some years, and rose more dramatically in other years.  In other words, it shouldn’t be surprising that glaciers are melting.  

The great debate is what is causing the sea level to rise, and how quickly it will  rise, and what will occur.  The first part of the question will quickly lead one down a rabbit hole regarding the ozone, greenhouse gases, fossil fuels, and whether the cause of the melting is caused by man.  An argument for another paper. The second and third parts of the question are how quickly the SLR will occur and what we should do about it.

 NOAA: “Projections for U.S. sea level rise for the end of the century and beyond depend on which greenhouse gas pathway we follow and how the major ice sheets respond to this ocean and atmospheric warming.”

“How much and by when depends mostly on the future rate of greenhouse gas emissions. But another source of uncertainty is whether big ice sheets in Antarctica and Greenland will melt in a steady, predictable way as the Earth gets warmer, or whether they will reach a tipping point and rapidly collapse.”  

The key phases are those where NOAA hedges its bet by throwing in words like “depends”, and “uncertainty.”  They are being honest – accurate predictions in sea level rise hinge on a number of things.  Things that are difficult to predict.

But those uncertainties haven’t given pause to some.

 The Intergovernmental Panel on Climate Change (IPCC) has produced and predicted sea level rise reports every five years over the past 30 years.  Over the years the estimates range from a few inches to almost three feet by 2100.  Other researchers are bolder.  A paper issued by noted and quoted Dr. Griggs of UC Santa Barbara in 2017 predicts: “…the global mean sea levels could rise of 2.5 metres (8.2 feet) by 2100 worldwide, and the sea levels in front of San Francisco could rise more than 3 metres (9.8 feet)”

 Unfortunately, many policy makers use these reports to determine the future of cities and lands that interface with the ocean.  Take the California Coastal Commission for instance.  On their webpage regarding sea level rise they predict: “sea level rise is expected to accelerate in the coming decades, with scientists projecting as much as a 66-inch (5.5 feet) increase in sea level along segments of California's coast by the year 2100.”

 The reason I say unfortunately is because many of these studies are fraught with dubious assumptions and missing data points (necessary for accurate analysis), and therefore produce reports that are untrustworthy.  You might have already noticed that the three quoted SLR predictions are vastly different.  That should cause some concern for those in positions of determining the future of our coasts. Despite what one hears and reads on mainstream media, the science on whether these will occur on a concerning level is not agreed upon by the scientists.  In fact, many scientist are now questioning the conclusions of many past studies, which predicted that the sea would rise by alarming numbers within the next century.

 Dr Albert Parker and Dr. Clifford Ollier of Australia produced an article in 2017 (“California sea level rise: Evidence based forecasts vs. model predictions”) where they analyze the methods used and the way data is extrapolated.  A few examples: 

1)    NOAA: “NOAA sometimes neglects the data that are apparently misaligned to compute trends.”

2)     IPCC: “…the present tidal range added to a sea level rise of 1.67 m (5.5 feet) predicted is unrealistic” 

3)    Dr. Griggs’s published report: “The report never mentions the lack of any direct evidence of sea level rise, such as tide gauges.  Instead they claim, from speculative assertions about possible rapid Antarctic ice sheet mass loss…” 

 As you might have gathered by now, predicting the future of our climate is complicated. Dr. Steven E. Koonin, former Undersecretary for Sciences in the US Department of Energy under President Obama, points out in his book: “Unsettled”, “…the local rates of rise along the US Coast vary enormously due to local conditions.”  He also points out: “The height of the sea surface is affected by small differences in the earth’s gravity from place to place, by ocean currents, by the temperature/salinity of the ocean, and even by the earth-dependent air pressure.”  In short, when it comes to SLR one size (model or study) doesn’t fit all.

 Reading the various studies where predictions on SLR are made one will notice very low increases (several inches or less) with high confidence, and very large increase (multiple feet or more) with less confidence.  In fact, very little confidence.  That is because they are unlikely to occur.  Science is less confident predicting rises in the sea level in terms of feet over the next several decades as these predictions require a number of changes in the earth’s atmosphere.  Those predictions include rises in Co2 levels, rapid warming of both the earth and the ocean to.  Even if those occur it is not certain the oceans will rise in dramatic fashion anytime soon.  That too is speculative.

 Based on all reliable evidence we can expect SLR, but most likely in almost non-noticeable inches a year.  The last question posed at the beginning of this report is what to do about it – ADAPT.

 We need to channel our efforts toward adapting to the realistic and certain challenges ahead.  Relegating ourselves to policies such as “Managed Retreat” is a “throw-in-the-towel” proposal that smugly hopes for defeat, and one that no policy maker should consider (See my paper on Managed Retreat).

 Dr Parker and Ollier (the Australian professors mentioned before) caution:  “Those involved in coastal management should be aware of the significant uncertainties of model predictions.  They must use caution in using model-based predictions, and prefer adaption to demonstrable problems rather than taking extreme and expensive measures against invalidated predictions.”  This is the biggest takeaway from this article – Basing policy on speculative, and often bias, predictions is folly and a dereliction of the trust that citizens expect from policy makers.

 By the way, Dr Sanders, mentioned at the beginning of this report, attributes the basis of our loss of sand to the century old practice of choking off the main source of our sand from rivers and creeks. He also cites strong wave action.  It’s not SLR.  See the article “Sand Erosion.”  

 We’ve harness the atom, flown man to the moon, and we can create solutions that will ensure our coastlines remain intact – but only if we use valid analysis.