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Accelerated Sea Level Rise – An Alternative Hypothesis – Raised by that?


Guest essay by Alan Welch – powered by Kip Hansen – May 14, 2022

Nerem et al. Paper, 2018, 4 years later

by Dr Alan Welch FBIS FRAS, Ledbury, UK – May 2022

abstract After analyzing NASA Sea Level readings for the past 4 years, it was concluded that the accelerometers due to Nerem et al. is a consequence of the methodology used and not included in the data. The analysis further predicts that the perceived accelerations will drop to near zero in the next 10 to 20 years.

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It has been 4 years since the paper by Nerem et al. (2018) first has been released. It produced many disaster shots, such as the Statue of Liberty with the sea lapping around her waist, and the rise in the BBC’s use of Climate Crisis or Climate Disaster in place of Climate Change, and Guardians.

It also started my interest in Climate Change, not because of what it presented, but because of the unacceptable method used to determine “acceleration”. I have inserted the acceleration in quotes because care must be taken in interpreting the physics behind the coefficients inferred in adjusting a quadratic equation. In the paper of Nerem et al. there are 3 stages.

Math – Calculated coefficient for a quadratic equation that fits the data set.

Physics – Labeled – “acceleration” – to 2 times the quadratic factor.

Unbelievable – Extrapolate to 2100.

The first is frank and acceptable. The second is highly dependent on the quality of the data and the length of the time period involved. The third is fraught with danger because the quadratic term governs the process when used outside the data scope. The last point is illustrated in Figure 1. This appears in https://edition.cnn.com/2018/02/12/world/sea-level-rise-accelerating/index.html with the caption “Nerem provided this chart showing sea level projections through 2100 using the newly calculated acceleration rates”.

Figure 1

As a retired Civil Engineer with 40 years of experience in technical analysis, I appreciate being careful when fitting curves that can be used to help understand a dataset. But to my mind, extrapolating 25 years’ worth of data over 80 years into the future is completely unacceptable. But it was this “acceleration” that caused press alarm after publication.

I will now discuss some aspects related to sea level data, including what could have otherwise been done in 2018, what the current situation is and what can be learned from this. study valuable data of the past 10 years. Prior to 2012, the data and any related analysis were more erratic, but over time a more stable picture is emerging.

Situation 2018.

The February 2018 data were the first to be analyzed. The data used is taken from the NASA website https://climate.nasa.gov/vital-signs/sea-level/. These data do not include any of the adjustments introduced by Nerem et al. but the calculated values ​​for slope and “acceleration” are not too different. When discussing “acceleration”, the process can be made simpler by taking values ​​of the line conformance, i.e. slope, different from the actual reading and working with what is called “residual”. Using residuals or full data results in the same “acceleration” but a more visible trend in using residuals.

Figure 2 below shows quadratic and sinusoidal joints starting from January 1993 to February 2018 using the latest values ​​of sea level. (See Note 1 below)

Figure 2

Situation in 2021.

A subsequent set of results covers the period from January 1993 to August 2021. The chart above has been updated in Figure 3 to show that x2 the coefficient is now 0.0441.

Figure 3

This update shows that the sine curve is still a reasonable alternative to the quadratic curve even though the time period can be extended to 24 or 25 years and the amplitude increases slightly. The 22-year period and amplitude were retained for continuity’s sake although the quadratic curve was re-evaluated at each update, which had the effect of slightly adjusting the slope and residuals.

Study the last 10 years dataset.

NASA data is analyzed for the past 10 years quarterly using the full dataset as of August 2021. “Acceleration” was calculated for each time step using data from 1993 to come every day. In parallel with this, a second set of “accelerations” is inferred by assuming the data follows the pure sinusoidal curve listed in the figures above. In the long run, these “accelerations” will be close to zero but when the wavelength and period are analyzed as non-representative “accelerations” the same will be inferred. Note 2 provides additional details for the sine curve to explain the process and results and illustrate the curve fitting process.

The results of these two analyzers are plotted in Figure 4 as “accelerations” relative to the date the NASA dataset was released and analyzed. For example, the two “accelerations” for 2018 would be those inferred using a quadratic fit for both the NASA data and the pure sinusoidal curves for the respective period from January 1993 to January 2018. The graph on the left shows the “acceleration” of the NASA data and the sine curve. Their shape is very similar but offset about 3 years. Shifting the sine curve for 3 years shows how closely the 2 curves follow each other. This close fit is of interest. NASA’s “acceleration” peaked around January 2020 and is steadily decreasing from then on, decreasing by about 8% over 2 years. Working against the peak, the “accelerations” continued to decrease until around October 2012, they were negative, i.e. deceleration. The close fit to the shifted sine curve may be random but there seems to be a clear message there, namely the high “acceleration” cited by Nerem et al. more is a result of the method used and not in the underlying data.

Figure 4

The next few years will tell whether the sinusoidal approach is more representative of the actual behavior, and whether the NASA data continues to produce a reduced “acceleration”. If the actual “acceleration” curve follows the trend of the sinusoidal curve, the perceived “acceleration” will be halved in about 6 years and close to zero in about 15 years.

1. Nerem, RS, Beckley, BD, Fasullo, JT, Hamlington, BD, Masters, D., & Mitchum, GT (2018). Rapid sea level rise due to climate change 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

Note 1. NASA data changes month to month. Typically, this is limited to the previous month or two of data due to the method used to smooth the readings. In July 2020, there was a big change for all data up to 2.5 mm, very little effect on slope, but “acceleration” was reduced by about 0.005 mm/year2. I couldn’t pinpoint the reasoning behind these adjustments, but they had very little effect on the overall results.

Note 2. The sine curve shown in Figure 5 will be analyzed.

Figure 5

The “acceleration” obtained from analyzing this sinusoidal curve over a period from 2.5 years to 70 years is shown in Figure 6.

Figure 6

The next 5 figures illustrate the curve fitting process in different time intervals.

Figure 7 uses a short 5-year period, and the adjusted quadratic curve is very close to the actual sine curve and immediately gives an “acceleration” of -0.2716 mm/year2 very close to the maximum acceleration of the curve of 0.285 mm/year2 obtained by distinguishing the two equations.

Figure 7

Figure 8 uses a 15-year period and the “acceleration” drops to -0.0566 mm/year2.

Figure 8

Figure 9 is very close to the period used by Nerem et al. of which it uses 25 years. The resulting “acceleration” of 0.0904 mm/yr2 is similar to Nerem’s parade.

Figure 9

Figure 10 covers 35 years and results in a rapid decrease in “acceleration” to 0.118 mm/year2.

Figure 10

Finally, extending the time to 65 years, which is almost 3 periods of 22 years, results in an “acceleration” of almost zero as shown in Figure 11.

Figure 11

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About Dr. Alan Welch:

Dr. Welch received a Doctorate in Civil (Grade 2A). From University of Birmingham and his doctorate from University of Southampton. He is a Construction engineer is run (United Kingdom), a member of Institute of Civil Engineers (UK) (retired), a member of British Interplanetary Associationand a member of Royal Astronomical Society.

Now retired, he has over 30 years of professional experience in many areas of technical analysis. Complete CV is here

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Comment from Kip Hansen:

Dr. Welch has worked on this analysis for many years and has compiled his findings at my suggestion in the form of an essay here. The above is the result of multiple versions that have been edited and presented here as an alternative to Nerem (2018) ( .pdf )and Nerem (2022). In a practical sense, Nerem (2022) does not change anything significantly from the 2018 paper discussed by Welch

On a personal note: This is not my theory. I am not in favor of curve fitting in general and alternative curve fitting would not be my approach for sea level rise. I endorse my most recent opinions expressed in “Sea level: Rise and fall – Slow down to increase speed“. Overall, my views have been fully aired in my previous essay on sea level here at WUWT.

I feel that Dr. Welch’s analysis is worth seeing and discussing.

Dr Welch lives in the United Kingdom and his response to comments on this essay will be made on UK daylight saving time: UTC +1.

Praise for his work in comments should be generous and criticism mild.

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