Home > Earth changes > The latest unsmoothed global sea level data from JASON shows a sharp downtick and slight downtrend

The latest unsmoothed global sea level data from JASON shows a sharp downtick and slight downtrend

April 18, 2011


One of the great things about WUWT is that it attracts commenters with a wide range of skill sets, who can often contribute far and beyond what we even see from our government sources. I’ve lamented the lack of updates from the University of Colorado sea level website, and when I got no response to emails, I decided to make a rare phone call and ask why. The answer I got from Dr. R. Steven Nerem was:

“This new website design won’t work with our current format, so if you can just be patient and wait a couple of weeks we’ll have it online.”

Not content to wait, and prodded by another commenter in an online tussle, CA and WUWT regular Roman M decided to find out himself. The results speak for themselves, quite a drop in the latest JASON-1 datapoint, with a general slight downturn in the JASON1-2 data since late 2009:

Sea Level Data ensemble, from Roman M, annotated by A. Watts – click to enlarge

Here’s the dialog on how this came about, from RomanM’s comment here:

Nullius in Verba wrote:

“… and am very curious to see what the most recent data looks like.”

So why not go and look at it?

Excellent suggestion. I did exactly that.

First, I went to the Aviso web site and found the place where one can generate sea level graphs. I generated the “Reference” version (“Reference” products are computed with the T/P-Jason-1-Jason-2 serie for the time series and with merged datasets for the maps) with the options: inverted barometer, seasonal removed and without isostatic adjustment. I got a graph with some points and a line drawn through it (which I have also saved at this location.

Below the graph, it said

Quick-look of selected data. Click on “download the image”
to retrieve the image in high resolution
or on “download the data” to get the data.

Since it appeared that the “data” was rather sparse and since I enjoy playing with numbers, I chose to download the data. I assume that you didn’t try this, because to my surprise, I got the message:

550 /pub/oceano/AVISO/indicators/msl/MSL_Serie_MERGED_Global_IB_RWT_GIA_Adjust.txt: No such file or directory

Must be a glitch, I thought! After a period of time with the same type of message appearing EVERY time that I tried to download data for a variety of variables, I got the idea that perhaps (as you suggested in an earlier comment) “somebody forgot to update it, or has been busy with other things, or the person who originally did it has left and nobody else was interested” at Aviso as well. must be a lot of that going around in the climate science community, right? 😉

Anyway, not to be defeated so easily, I managed to actually locate some updated results (into January 2011) at NOAA in NetCDF format. I drew what was purportedly the same graph from that data and got something that was quite different.

Let me explain it to you. What you saw in the graph at Aviso was “smoothed results from the data”, not the actual data itself. Furthermore, despite the fact that they obviously shared their data in the past (because they put links into their page for that purpose), they were not doing so for the past 24 hours that I have been accessing their site – maybe they sent it all out to be “cleaned”.

I have other graphs, but I will just show one more using all of the satellites. This one used real data, not the processed results chosen by Aviso and not even shared by them.

Nullius in Verba seems to be appropriate an appropriate description of your credibility: “don’t believe anything he says” … 😉

Another curiosity:

P. Solar says:

The other reason things have gone quiet may be an unprecedented swing in the Jason 2 calibration curve.

I don’t know if they have published any findings on why it jumped by 10 mm at the end of 2009 but if it has skipped again maybe they are frantically trying to tidy things up before publishing data.

He has a point, have a look at this calibration curve published on the (CU sealevel website) for JASON1 and 2:

Compare that to the curve from the previous TOPEX A and B satellites:

Curiouser and curiouser.

To be fair, and to compare to what RomanM plotted I’ll also show the similar ensemble graph provided by NOAA, which uses smoothed data points:

Categories: Earth changes Tags: , , ,
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