From Watts Up With That?
Guest Essay by Dr. Alan Welch FBIS FRAS
We have now entered the 4th decade of measuring sea level rise using the quartet of satellites Topex and Jason 1, 2 and 3. The first 3 decades were reported in the trio of papers (Ref 1), (Ref 2) and (Ref 3). These concluded that.
1. The perceived “accelerations” are mathematical accelerations occurring due to the methods of calculation, i.e. quadratic curve fitting, as used by Nerem et al [.pdf] (Ref 4) in their 2018 paper. Also, the start date of Jan 1993 also plays a major role in how the “accelerations” pan out.
2. The “accelerations” are now generally reducing year on year and are predicted to reach levels compatible with the long term (over 100 years) Tidal Gauge values during the next decade or two before stabilising over the next few decades.
3. A time span of 30 years is much too short a period to calculate actual accelerations with 3 or more times this period being needed.
In this paper “accelerations” is used to indicate that those values are mathematically produced using twice the quadratic coefficient. Having said that the trends in values since about 2012 have settled sufficiently to make actual judgements regarding long term variation and trends.
The data for year 2023 will now be analysed with emphasis on 2 aspects, namely the predicted sizeable El Niño and the shenanigans concerning the data for October and November when nearly every data value changed with some changes being quite significant at over 8mm compared with annual increases of 3 to 4 mm.
Data releases via the NASA Global Climate Change/Vital-Signs/Sea Level Rise web site were made during 2023 for January, February, April, June, October, November and December but although all were analysed, not all will be reported on. Since February 2018 the analysis of the data has taken place in a standard manner every time a new set of data has been released. Extra processing has been also done when deemed of interest. In January 2023 the NASA site added an extra column (column 13) to the data which was as column 12 but with the GIA not applied [see column definitions just below]. The diagrams appearing on the NASA website showing sea level rises also changed at this stage in using column 13 instead of column 12. The inclusion of GIA or not only affects the rate of change and not any “acceleration” as it is set to a constant change of about 0.24 mm/year. In all the analyses for this paper and previous papers column 12 results have been used.
The full definitions of these 2 columns are,
Column 12 smoothed (60-day Gaussian type filter) GMSL (GIA applied) variation (mm); annual and semi-annual signal removed.
Column 13 smoothed (60-day Gaussian type filter) GMSL (GIA not applied) variation (mm); annual and semi-annual signal removed.
At this stage I would like to thank Kip Hansen for his patience in reading and replying to my steady stream of emails and whose comments have helped me formulate my ideas. Kip has not agreed with all my findings and ideas, but a friendly rapport has taken place between us.
Starting with the February data the “accelerations” have been calculated for increasing periods spanning the time from January 1993 up to the time of calculation. The results are shown in Figures 1 and 2.
Figure 1 compares the “acceleration” trend with that obtained from assuming the sea levels deviate from a straight line in a sinusoidal manner with a period of 26 years, an amplitude of +/-4.2 mm and with a suitable phase shift. The resulting graph of “accelerations” is labelled “Sinusoidal” on Figure 1. This curve is not a sinusoidal curve but a portion of a “damped” sinusoidal curve the derivation of which is shown in the Appendix to paper 1 (Ref 1). Its long-term variation is shown in Figure 3 together with average Tidal Gauge value. In this the sinusoidal curve is converging on zero but in reality, there could be a small long-term value commensurate with the Tidal Gauge value.
At this stage it had been stated that there may be a significant El Niño starting. Figure 4 below shows a plot of the El Niño Index. This is a more recent plot at the end of 2023, but the February 2023 data coincide with just about when the Index was zero but increasing.
It was decided to try to simulate the effect of an El Niño by taking the February 2023 data, which was available in May 2023, and extending the linear trend by about 5 years. Over the first 2 years a strong El Niño effect was achieved by raising the increase in sea level by roughly an extra 10mm. Over the next year the sea level drops back to the linear trend line. The Simulated El Niño is shown in figure 5 together with the linear trend.
A note to the purists. Every month when a new month is analysed the slope of the linear fit varies slightly therefore any actual residual sea level (actual minus linear value) or sinusoidal variation is measured to a slightly modified linear line. As the slopes are generally in the range 3.2 to 3.5 mm/year this is considered acceptable as being within “engineering tolerance” and being a retired engineer, I can sleep at night with this situation.
The modified data were analysed, and “accelerations” determined. The results are shown in Figure 6. The effect of the El Niño is to increase the “acceleration” temporary by about .01mm/year2 over the next 12 months or so and then resume a downwards trend. Interestingly two previous El Niños in 2015/16 (strong) and 2018/19 (moderate) show up as wiggles on the blue curve. The associated reduction in “acceleration” since 2020 is also shown in Figure 7
The next set of data to be analysed is for June 2023 resulting in Figures 8 and 9 which indicate a small influence of the El Niño starting.
When the October data were analysed, it was clear that there had been a dramatic change in the data readings as shown in figure 10.
Figure 11 below shows the differences between the October 2023 data and the June 2023 data. Over the first 10 years there had been increases in the October data of up to over 8mm. For the next 13 years the values stayed roughly the same with a reduction of about 2 mm over the last 7 years. The kick up at the end is mainly due to the El Niño. The consequences of these changes were to reduce the slope by about 0.3 mm/year and increase the “acceleration” by about 0.008 mm/year2. As of now no explanation has been found as to why these changes occurred. The last time any changes had occurred was in August 2021 with those changes varying between -2.5 mm and 0.5 mm resulting in little change in slope and a reduction in “acceleration” of 0.004mm/year2.
The November and December data release were anticipated with some trepidation and then analysed. The changes from June 2023 to November 2023 were lower as shown in Figure 12 with a maximum change now being about 5mm. From June 2023 this resulted in a reduction in slope of about 0.2mm/year and a reduction in “acceleration” of about 0.003mm/year2.
At this stage it was decided to create a combined plot of the November data showing the NASA data and the curve produced by combining the linear line with the sinusoidal variation, Figure 13.
Figures 14 and 15 show the latest (December 2023) plots of “acceleration” and reduction in “acceleration” since the 2020 peak.
A final plot, Figure 16, shows a comparison of “accelerations” since Jan 2020 based on the February 2023 data with the added El Niño simulation and the December 2023 data. If the 2024 trend follows the simulation trends the “accelerations” will peak at about .085 mm/year2 in the late summer of 2024 and quickly start reducing at nearly 0.01mm/year2 until the next significant El Niño appears.
Who doesn’t like a prediction? I’ve put my head up over the wall but at 86, with no agenda, reputation, University role or job to keep it’s nice to have that freedom. Just have to keep taking the tablets to see it all come to fruition!!
One conclusion is that the “accelerations” as calculated are not the harbingers of Doom and Gloom that many Climate Scientists, the BBC and the Guardian Paper portray. These “accelerations” may just be mathematical quirks and not of any major physical significance, but it could be revealing to try to match them and predict future variation especially over the next 10 years or so.
# # # # #
1. https://wattsupwiththat.com/2022/05/14/sea-level-rise-acceleration-an-alternative-hypothesis/
2. https://wattsupwiththat.com/2022/06/28/sea-level-rise-acceleration-an-alternative-hypothesis-part-2/
4. Nerem, R. S., Beckley, B. D., Fasullo, J. T., Hamlington, B. D., Masters, D., & Mitchum, G. T. (2018). Climate-change-driven accelerated sea-level rise detected in the altimeter era. (full text .pdf) Proceedings of the National Academy of Sciences of the United States of America, 115(9). First published February 12, 2018
# # # # #
Comment by Kip Hansen:
I have facilitated the publication of this essay, the fourth of Dr. Welch’s contributions here. Dr. Welch and I have had a long-standing continuing conversation, over several years, about sea level rise [SLR] rates and the assertion by some, Nerem et al. and others, that sea level rise is accelerating (meaning for SLR, rising faster and faster). NASA/NOAA likewise call the change in the rate seen when the satellite-calculated SLR is tacked on to the global tide gauge record at the year 1996 ‘accelerating SLR”. As with all numerical data that can possibly be associated with Climate Change, there is and has been a lot of fiddling with the methods, calculations, and resulting numbers. Thus, with sea level data, for which the annual changes are small compared to the magnitude of the confounding factors, little if anything can be ascertained with any degree of scientific certainty.
Long-time readers will remember that I am not a fan of the SLR Acceleration topic – for reasons stated above.
Dr. Welch’s take on acceleration is as valid as any other out there.
Earth’s sea levels are rising – they will continue to rise for all the reasons they have risen for the last few hundred years. It is my opinion that they will continue to rise at the same rate – 2 or maybe even 3 mm per year – into the future. This slow steady rise can and will be a problem for highly developed low-lying areas. Building within 8 inches of the today’s sea level – mean high tide — is and was always exceptionally foolish.
My thanks to Dr. Alan Welch for his continuing efforts to keep a close eye on the topic which allows him to catch repeated alterations of the data sets being used.
Dr. Welch is a guest here, please treat him like you would a guest in your own home.
Share this:
Discover more from Climate- Science.press
Subscribe to get the latest posts sent to your email.
You must be logged in to post a comment.