Guest essay by Albert Parker
Today I was informed of an alarmist claim about the sea levels of Perth, Western Australia, Australia. It started with this story:
“In the next eight years our water level is going to increase by about 25cm, which is much higher than the water level increase for the last 115 years,” Professor Pattiaratchi said.
As I examined the Fremantle tide gauge in a recent peer reviewer work (Parker, 2016), I immediately checked if there was any change in the measured data to motivate such a claim.
I therefore downloaded again the relative sea level data of Fremantle, in Australia, the best tide gauge of the Indian Ocean.
As shown in Figure 1, the PSMSL data downloaded today June 6, 2018 from https://www.psmsl.org/data/obtaining/stations/111.php, suggest about same rate of rise and about same acceleration.
a
b
Figure 1 – (a) Fremantle relative mean sea level. Linear and parabolic fittings of the PSMSL RLR data, as it is or with gaps filled. (b) PERT (Perth) GPS dome. Image reproduced modified from SONEL.
With date range January 1897 to December 2016, the relative rate of rise is +1.67 mm/yr. and the acceleration is +0.006 mm/yr2 (the usual few micrometers per year squared).
As the completeness of the record is 92%, I decided to fill the gaps interpolating the data of same month in neighboring years. This way I computed a relative rate of rise of +1.70 mm/yr. and an acceleration of +0.005 mm/yr2.
Worth to mention, the rate of rise of the sea level in Fremantle is less than the likely rate of sinking of the instrument, as SONEL computes for the nearby GPS dome of PERT (Perth) a subsidence rate of -2.09±0.38 mm/yr. (analysis in www.sonel.org/spip.php?page=gps&idStation=812),
and in the similarly close-by GPS of HIL1 (Hillarys), where an even larger subsidence rate of -2.78±0.31 mm/yr. is measured (analysis in http://www.sonel.org/spip.php?page=gps&idStation=1918).
The Perth basin is indeed subjected to subsidence (Featherstone, Penna, Filmer, & Williams, 2015; Featherstone, Filmer, Penna, Morgan & Schenk, 2012), and the sea levels are rising here cause the land is sinking.
Therefore, nothing new from the measurements.
Which is therefore the novelty?
In performing todays’ analysis, I visited again the PSMSL and the SONEL web sites, and I discovered how the “adjustocene” progresses within intergovernmental projects.
- PSMSL does not link any more the Fremantle tide gauge information to the SONEL page of the PERT GPS dome.
- SONEL, that proposes the computed absolute sea level rises by correcting the relative rate of rise from the tide gauge with the subsidence rate from the GPS monitoring, does not propose any more the absolute rate of rise negative for Fremantle.
If you look at the images of Figure 2, with the same time window for the online graph, with reference to two years ago, the negative absolute sea level rise of Fremantle has disappeared, similarly to the negative absolute sea level rise of a Japanese tide gauge.
a
b
Figure 2 – Absolute sea level rates of rise (relative sea level rate of rise from tide gauge, absolute vertical land velocity from satellite GPS) in the World Tide gauges with theoretically same data 1900 to 2013 before and after Fremantle was eliminated. Images reproduced modified from SONEL, www.sonel.org. (a) Image downloaded 6 June 2018. (b) Image from Parker (2016). The inconvenient result for Fremantle could not have been accepted by the intergovernmental scientists.
Other changes may be spotted, even if less evident.
In many regimes, dissidents disappear. In the climate change dictatorship, inconvenient data suffer the same treatment.
Within Australian universities, from Murry Shelby to Bob Cater, from Peter Ridd to myself, academics not supporting the narrative are simply forced to leave, in a way or another, or not even start, as Bjorn Lomborg. I do not believe anyone within Australian universities will declare that the sea levels in Fremantle have been rising since 1897 without any significant acceleration component, and in the next 8 years they may rise on average of not even 25 millimetres, but 16 millimetres …..
References
Featherstone, W., Filmer, M., Penna, N., Morgan, L. & Schenk, A. (2012). Anthropogenic land subsidence in the Perth Basin: Challenges for its retrospective geodetic detection. Journal of the Royal Society of Western Australia, 95(1), pp.53-62.
Featherstone, W.E., Penna, N.T., Filmer, M.S. & Williams, S.D.P. (2015). Nonlinear subsidence at Fremantle, a long‐recording tide gauge in the Southern Hemisphere. Journal of Geophysical Research: Oceans, 120(10), pp.7004-7014.
Parker, A., (2016), The Sea Level Rate of Rise and the Subsidence Rate Are Constant in Fremantle, American Journal of Geophysics, Geochemistry and Geosystems, 2(4):43-50.
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