Alastair B. McDonald wrote:

On Tuesday, 21 July 2020 at 18:25:34 UTC+1, N_Cook wrote:

snip


History of these results, ranking by R*R, goodness of fit, for best
curve type each time usual the indicial form and decreasing
acceleration , using 2003 to the latest datapoint to avoid the
early altimeter calibration problem and post-Pinatubo recovery SLR
flattening and including the 1993 to 2003 tranche does not actually
make much difference to projections.
Initially melding together the separate J1,J2 and J3 plots and then
since 2019 using the Aviso Reference data as the small GIA
component is getting less and less significant and less and less
confidence in the mission cross-over/overlap data, going in and out
of the filters. SLR to year 2100 using Dec 2017 data of May2017 ,
J1+J2 only , 56.2cm data to 25 May 2018 to 2100 , SLR 57.1 cm
data to 02 Aug 2018 to 2100 , SLR 50.5 cm
Update data to 01 Sep 2018, public output 07 Dec 2018
SLR to year 2100 , 49.0 cm
Update data to 01 Oct 2018, public output 18 Jan 2019
SLR to year 2100 , 50.9 cm
Update data to 29 Nov 2018, public output 02 Feb 2019
SLR to year 2100 , 77.4 cm
Update data to 26 June 2019, public output 07 September 2019
SLR to year 2100 , 80.2 cm

Update to 25 July 2019, 02 Nov 2019 public output,
SLR to 2100, 88.2cm

Update 11 January 2020
for data 2003.002659 to 2019.806999,
SLR to 2100 , 88cm

01 Dec 2019 output to the public 15 Feb 2020
SLR to 2100, 117cm (quadratic was the best fit that time, otherwise
indical was 89cm)

624 datapoints from year 2003.002659 to year 2019.9699
output to the public 29 Feb 2020.
SLR to 2100, 88.5cm

640 datapoints 2003.002659 to 2020.404245 website back working on
20 July 2010
SLR to 2100 = 82.9cm

Emlargement of the above and a few images on my page below
--
Global sea level rise to 2100 from curve-fitted existing altimetry
data http://diverse.4mg.com/slr.htm

I have downloaded the data into an Excel spreadsheet and fitted a
polynomial trendline which i have extended to 2100. The result was a
sea-level rise of ~80 cm which agrees with your indicial (best fit).
Nothing for me to worry about at 25m ASL, but bound to have
consequences for properties on the coast during storms, e.g.
Sandbanks nr Poole.

I would be very wary about fitting trendlines to processes that are
likely to be highly non-linear and which may have step-changes.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr