About That “Measured” Sea Level Rise
Posted by greg2213 on September 7, 2010
When shown graphs that look precise we tend to forget the errors bars, which, for some reason, weren’t included on the graph…
From a WUWT comment:
(commenter is responding to a previous comment, emphasis is mine.)
I have recommended this document in comments here several times in the past
It is the data products handbook for the Jason-2 satellite system, the latest and greatest of the our measurement systems for determining MSL (Mean Sea Level.) It’s worth studying for the large amount of basic information on the multitude of elements involved in attempting to derive what the global mean sea level is, but for the purposes of the discussion of the burgeoning rise in sea level the most pertinent section is 2.3.1 Accuracy of Sea Level Measurements. In particular this sentence ” The sea surface height shall be provided with a globally averaged RMS accuracy of 3.4 cm(1 sigma), or better, assuming 1 second averages.”
A number of points to consider regarding that sentence
1) Lay a +/- 3.4 cm error bar across that frequently published graph of rising MSL in the satellite era and it covers the whole graph quite nicely.
2) The 3.4 cm accuracy is a pre launch specification that is still TBD.
3) As I mentioned the Jason-2 is the latest and greatest iteration in our efforts, which has significant improvements relative to Jason-1, which was itself an almost order of magnitude improvement over the older TOPEX/Poseidon sats.
Also, if you peruse the Table at pg 17/67 of the PDF, you’ll see a line for significant wave height which suggests that the system is unable to read the surface to better than 0.4 METERS when waves are present, which makes the bold claims of achievable accuracy seem more than a bit suspect.
Even I occasionally fall into the trap of granting excess credibility to satellite data, but we would all be well advised to remind ourselves on a regular basis that, although these products of our incredible human ingenuity are published and quoted with amazing levels of precision, they are vastly complex systems which even if they could be operated at levels of physical perfection never achieved in any much less complex human mechanism, would still not be able to provide accuracy anywhere near that precision suggested in the presented data.
More on the subject:
- A Report on Sea Levels for the Greening Earth Society – a long discussion of issues involved with sea level measurements and some remarks on how little rise there has likely been.
- Rates of sea-level change over the past century in a geocentric reference frame – … leading to a reconciled global rate of geocentric sea level rise of 1.61 ± 0.19mm/yr over the past century in good agreement with the most recent estimates.
- Sea-level Expert: It’s Not Rising! – among other things, he says (regarding the IPCC sea level graph:) …So it was not a measured thing, but a figure introduced from outside. I accused them of this at the Academy of Sciences meeting in Moscow—I said you have introduced factors from outside; it’s not a measurement. It looks like it is measured from the satellite, but you don’t say what really happened. And they answered, that we had to do it, because otherwise we would not have gotten any trend!