Guest Essay by Kip Hansen – 3 May 2022
Yes, I do know that acceleration, technically, means just a change in velocity. But, in every day English, we use acceleration to mean an increase in velocity – speeding up — and deceleration as a decrease in velocity – slowing down. I mention acceleration and deceleration because one of the major talking points of IPCC reported findings about sea level rise, the incessant media mantra, is that “Sea Level Rise is Accelerating”. (here, here, here, here, here and hundreds more here)
~ ~ ~ ~ ~ ~ ~ ~ ~ ~
LONG ESSAY ALERT: With apologies, this essay is for those who are interested in sea level rise and the question: Is sea level rise accelerating? It takes a lot of words and illustrations to explain the true situation. Those with limited time can just accept this simple answer and move on:
“Probably not at all, just maybe a wee tiny little bit that will not make any difference over the next century or two.”
~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Is sea level rising? Yes, of course it is. It has been rising since about 1750-1775, coinciding with the end of the Little Ice Age. This is widely accepted as shown below:
How do we know? The important aspect of sea level is how it affects the land at the edges of the oceans. The water level there is measure by tide gauges at the ports and harbors of the world. The levels recorded by tide gauges are of local Relative Sea Level (RSL) – the level at which the sea surface hits the land. This measurement includes both the actual rise in the sea surface height (think: distance from the center of the Earth) plus any vertical movement (VLM) of the tide gauge itself, either up or down. In many locations the land mass itself is subsiding (sinking) due to glacial isostatic adjustment (GIA) as the land mass readjusts itself for the melting of the glaciers of the last great Ice Age and at most tide gauge locations, the structure to which the tide gauge itself is attached, such as a pier or dock or sea wall, is also itself subsiding due to compaction of the soil underneath and the fact that many such locations are built on man-made filled substrate. To see if sea level is rising, it is only necessary to look at high quality tide gauge records for whom the VLM is known to be relatively constant. The linearity of these graphs is typical, there are many, many more. This image of the records of some such tide gauges:
Sea level is rising all around the world but at different rates as shown by the slopes of the trends. Why? NOAA says: “The graphs give an indication of the differing rates of vertical land motion, given that the absolute global sea level rise is believed to be 1.7 +/- 0.3 millimeters/year during the 20th century.”
As you can see, each of these long-term graphs have trends that are linear, that can be represented as straight lines, despite the wide amount of inter-annual variation. None of them swoop up or swoop down, accelerating or decelerating on the century time scale.
This is clear as shown in long-term tide gauge records at the PSMSL. If sea level rise was accelerating, it we would see it in these graphs. But we do not. Why then does the IPCC and the media go on and on about Sea Level Rise (SLR) Acceleration?
Boon and Nerem (and here). Both of these accomplished scientists have been publishing paper after paper (Nerem here, Boon here) claiming they have detected the sea level rise acceleration that we do not see in the tide gauge records.
I have discussed Boon and VIMS in the past. SEA LEVEL: Rise and Fall – Part 5: Bending the Trend.
I have written about the efforts of R. Steven Nerem at CIRES (Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder) and a major player at their Sea Level Group. Nerem is convinced that sea level rise must be accelerating. He has written papers and presentations and mostly convinced the IPCC and policy makers that that acceleration (by which he means sea level is rising faster and faster) it actually taking place in the real world in which we live and breathe.
Before we go on, readers should be aware of the potential bias in all of Nerem’s work:
BIAS WARNING: You should know that Nerem is one of the contributing author’s to this WaPo, May 2016, piece “10 things you should know about sea level rise and how bad it could be”, in which it is blandly stated “Scientists estimate that if it warms by about 4 to 5 degrees Celsius (7.2 to 9 degrees Fahrenheit), which is projected to happen by the end of the century if we don’t act on climate change, then all the ice will eventually melt. That’s 230 feet of sea level rise.” —– You should consider this whenever you see anything about sea level out of the Sea Level Research Group @ the University of Colorado — their blog actually contains a link to this newspaper article, as if it were a scientific paper or something to be proud of.
My previous work on Nerem and the Sea Level Research Group:
Now, Nerem et al. have been at it again – still beating the sea level rise acceleration drum, but now with a longer data set and a much weaker position. As of today, the full paper is available as “Extrapolating Empirical Models of Satellite-Observed Global Mean Sea Level to Estimate Future Sea Level Change” by R. S. Nerem, T. Frederikse, B. D. Hamlington.
From their abstract:
“We estimate a quadratic model of climate-driven global mean sea level (GMSL) change based on the satellite altimetry record (1993–2020), including a rigorous assessment of the errors in the quadratic coefficients. We then extrapolate this model 30 years into the future to 2050 and compute the 90% confidence interval. We find GMSL rise in 2050 relative to 2020 will be 16.4 cm higher, with an uncertainty range of 11.3–21.4 cm…..” (11.3 cm = 113 mm or ~ 4.45 inch : 21.4 cm = 214 mm or ~ 8.4 in)
First, let’s be clear, Nerem et al.’s paper does not find anything. No one can find something/anything in or about the future. What their paper does do is it extrapolates a rise in sea level of 16.4 cm or 6.45 inches by 2050, now 28 years away, through a model primed with the concept of a quadratic curve of acceleration that they believe exists in the current sea level data.
As of today, NOAA shows a sea level rise rate of 3.0 ± 0.4 mm/yr. The slope trace (black) is on the original. This is lower than that claimed by NASA’s on their special sea level rise page of 3.4 mm/yr in the next image:
Both of the above images, from data up to the same day, are based on the same data set from the same satellite missions. The difference in 30 year trend – over 10% – is the based on methods of adjustments for the variables as Nerem stated in an earlier paper: “Satellite altimetry is somewhat unique in that many adjustments must be made to the raw range measurements to account for atmospheric delays (ionosphere, troposphere), ocean tides, variations in wave height (which can bias how the altimeter measures sea level), and a variety of other effects. In addition, the sea level measurements can be affected by the method used to process the altimeter waveforms, and by the techniques and data used to compute the orbit of the satellite.”
The above graph from NASA shows a minor downward shift in SLR in about 2006 through 2015, but the sub-set of data has the same slope (trend) as the entire set. The NASA shows no curve, no acceleration. For details on Nerem‘s previous SLR acceleration claims, see my three essays linked above.
Here is the money plot from Nerem et al. (2022):
Nerem et al. attempt to support this projection with a back-projection that they claim matches the historical record:
In this graphic, the orange trace and shading is the observed SLR from Frederikse (2020). Note that Frederikse is a co-author on Nerem (2022). Nerem starts his curve with his previously speculated curve in the satellite data and extends it back over Frederikse’s “tide gauge record”.
Ignoring the fact that Nerem’s quadratic fit back in time shows that sea level should have continued to rise into the past (prior to 1965) as his curving quadratic trend then begins rising, what is most obvious is that Nerem uses the slow-down in sea level rise to create an acceleration.
There is one major feature of Nerem’s Figure 4 that is not mentioned in the caption or the text of the paper. It is the most prominent feature of the graph and yet Nerem is silent on what it might be or what it means. He is even silent after I wrote him by email and politely asked about it. Can you pick it out?
Yes! The giant grey shaded triangular feature. Such a shaded area is normally used to represent uncertainty in data or a projection. The only mention of what the grey area might be is this: “Figure 4 shows the results of the extrapolation backwards in time prior to 1993 compared to the tide gauge GMSL record. Although the errors on the extrapolation are large, the differences with the tide gauge record have a standard deviation of only 5 mm. Since our quadratic model performs well for the period 1960–1993, it can reasonably be expected to perform similarly for the next 30 years.”
Saying that “the errors on the extrapolation are large” is an historic-scale understatement. The error range in the backwards projection from 2022 back to 1960 is larger than the entire illustrated sea level rise over the same period. The extrapolation basically means “the sea level could have been anything over a more-than 150 mm range” – totally, utterly worthless.
[ASIDE: I will admit, that when I first read this paper, and page-downed to the page containing the graph, I literally laughed out loud.]
Now, let’s look at the real full record from Frederikse 2020 (used as the orange trace and shaded area in Nerem’s Fig. 4 above):
The Frederikse data is not the real observed global sea level from tide gauges, but is a reconstruction. But we will let that stand, as no one can determine global sea level, rise or fall or rate, from tide gauge data.
Looking at only the blue trace, and its shaded area, labelled observed SLR, we see sea level rising from 1900 to about 1960, when the rise obviously slows, becoming nearly flat. Note as well that in 1940, the claimed uncertainty is about ±20 mm and then reduces to about ±10 mm in 2021 – both of which may be off by an entire order of magnitude (reference my earlier essays linked at the beginning). Then, around 1980, sea level rise begins to regain its prior rate. Nerem uses this slow-down to create the illusion of an acceleration curve that extends up into the satellite data. But, the satellite record, original data directly from JPL and NASA, contains no curve:
This next graph is directly from the published data set of the 10-day data points from each of the Topex/Jason satellite missions as of April 29, 2022:
Both graphs show the decade-long slow-down, 2006-2015, and then a return to the linear trend of the 1990s.
Here is the money question, from a climate pragmatist viewpoint:
To get Nerem’s 16.4 cm by 2050, sea level would have to rise at 5.47 mm/yr for the next 28 years — almost twice the rate of today. For Nerem’s higher extrapolation, 21.4 cm by 2050, sea level would have to rise at 7.13 mm/yr.
As of the latest data from the Jason-3 satellite mission, sea level rise is continuing its long-term linear trend of about 3 mm/yr, with no acceleration as of yet.
For those interested, Nerem et al. give a Kipling-esque ‘Just So story’ on how it could be that sea level rise is accelerating in their paper, starting on page 5 with the sentence “The process-based argument for using a quadratic model is as follows….” .
Even at their most enthusiastic, Nerem et al. have sea level rise acceleration at 0.1 mm/yr2.
1. Globally sea level is rising. It has been rising since the end of the Little Ice Age and will continue to do so unless there is a major change in the planetary climate leading to another similar cold period.
2. There is no good, sufficient or convincing evidence that global sea level rise is accelerating – there is only hypothesis and speculation. Computation is not evidence and unless the results can be practically viewed and measured in the physical world, such results must not be presented as such.
3. It is not scientifically legitimate to splice tide gauge records to satellite records – ever – as they measure different physical things. As the tide gauge record extends to the present and continues to improve in quality, it should stand alone. Tide gauge records apply only to the locality of the tide gauge and its Relative Sea Level.
4. The global tide gauge record is quantitatively problematic, but individual records can be shown as qualitative evidence for a lack of sea level rise acceleration.
5. Sea level and sea level rise are part of the modern scientific controversy generally known as Global Warming or, more recently, Climate Change. Most facts presented in discussions on all sides of the issues involved are more than likely to be opinions and, as always, opinions vary. Wildly.
6. Only actually measured, validated raw data can be trusted and even then, you have to really understand what has been measured, exactly, and how it has been measured. One such example is the original data record of your local tide gauge – unadjusted, untampered-with, un-averaged.
# # # # #
This field-wide effort to convince the world that sea level rise is accelerating is very destructive. Localities on sea shores are being forced to try to plan and prepare for frightening sea levels that will not be seen for centuries, if ever.
The situation could be likened to civil engineers of 1900 being forced to plan their streets and highways to accommodate the speeds and sizes of today’s high-powered automobiles and tandem tractor trailers. The difference being that today’s cars and trucks actually materialized, while the scary IPCC-projected RCP8.5 sea levels never will.
Thanks for reading.
# # # # #