Reconciling TOPEX/Poseidon sea level data

[Robert Chris]

I have come across the work of Nils-Axel Morner who holds that IPCC reports that sea level is rising are inaccurate and alarmist.  In his 2004 paper (http://www.sciencedirect.com/science/article/pii/S0921818103000973) he shows a graph of 'raw data' from the TOPEX/Poseidon satellite which shows that over the period from 1993 to 1999 there was no discernible change in global sea level.  In IPCC AR4 Ch5 reference is made to a 2004 paper by Cazenave and Nerem which presents the same TOPEX/Poseidon data extended to 2003 but now shows a clear rising trend (http://www.eos.ubc.ca/~mjelline/453website/eosc453/E_prints/2003RG000139.pdf).  In AR4 this series is further extended to 2006 and shows a continuing rising trend.  It is very much based on this paper that the AR4 drew its conclusions about sea level rise.

Can someone explain to me why, at least for the first 6 years, these two presentations of the same data show such divergent trends?

Morner is also reported as saying:

'In 2003 the satellite altimetry record was mysteriously tilted upwards to imply a sudden sea level rise rate of 2.3mm per year. When I criticised this dishonest adjustment at a global warming conference in Moscow, a British member of the IPCC delegation admitted in public the reason for this new calibration: ‘We had to do so, otherwise there would be no trend.’ (http://iceagenow.info/2011/12/satellite-sea-level-data-tilted-distort-figures-sea-level-expert/)

Robert Chris
The Open University
r.g....@open.ac.uk

[Ken Caldeira]

I would be very suspicious of indirect quotes attributed to unnamed ipcc authors. The truth of scientific statements depends on how they are qualified. 

I am no expert in this area but my understanding is that satellites are subject to decaying orbits, aliasing with respect to satellite orbits and tides, and a myriad of other complicating factors. 

Often, people who claim they are showing 'raw' satellite data are just displaying their ignorance of these complicating factors.  

My understanding is that satellites are often calibrated using tide gage data. See for example. 

http://imos.org.au/srscalval.html

http://imos.org.au/srscalval.html

Ken Caldeira

kcal...@carnegie.stanford.edu

+1 650 704 7212

http://dge.stanford.edu/labs/caldeiralab

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[Ken Caldeira]

http://sealevel.colorado.edu/

Mis-pasted link

[Ken Caldeira]

I think it is incumbent on Robert Chris to provide the name of the person who purportedly made the claimed statements so that we can verify the supposed facts that Robert Chris is promulgating. 

This group should not be allowed to be used to make unattributed And unsubstantiated defamatory comments. 

Robert, I think you should either provide support for your statements or apologize to this group for making unsubstantiated defamatory remarks. 

Ken Caldeira

kcal...@carnegie.stanford.edu

+1 650 704 7212

http://dge.stanford.edu/labs/caldeiralab

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[Ken Caldeira]

Maybe I over reacted in my previous post.  Robert Chris professed ignorance whereas the people he cites do not to my knowledge profess ignorance. 

I too am not an expert here, but my understanding is that the raw data are things like signal return times and phase shifts. There is no sea level that is raw data. 

There are tide gauges that measure local sea level. These same locations are observed by satellite and are used, to the best of my limited knowledge, to ground truth the satellites. So, the satellites can be thought of as a way to extrapolate from these local tide gauges out to the open ocean and other areas where there are no tide gauges and thus develop and estimate of global sea level. 

The satellites, as I understand it, are thus best thought of as spatial extrapolators and interpolators and not as the primary source of high confidence in sea level rise. 

Of course you also cannot naively interpret local tide gauge data either because factors like isostatic rebound from ice sheet removal can confound the global signal in a local record. 

Again, this is not my area of expertise so I may have some details wrong here. 

------

Can I please ask that people not post statements attributed  to unnamed people to this group even if that attribution was made in quoted text? This just propogates urban myths. 

If you have a question, please ask it, but try to avoid promoting a false premise. 

Ken Caldeira

kcal...@carnegie.stanford.edu

+1 650 704 7212

http://dge.stanford.edu/labs/caldeiralab

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[Robert Chris]

It seems my original post was might have been worded more clearly.  Ken, I was certainly not  promulgating anything, I was just asking a simple question and I did include links to the sources.  As a social scientist a major concern of mine is how the climate change/geoengeering issues are communicated.  When I get totally contradictory inputs from apparently reputable scientists in peer reviewed journal articles I have great difficulty in reconciling them and even more so when they appear to be drawing their conclusions from the same primary data set.

I have already written in this group about my contact with a climate 'sceptic'.  This thread has the same provenance.  Whereas previously I was reluctant to mention his name, he has now made it clear that his position is in the public domain and he is happy to be identified with it.  Richard Bean is the author of The Heretic, a stage play, which won some prizes in London and is about to open in Melbourne, Australia.  The play is a broadside against climate change.  Whether you agree with the message or not, it is a very good play (as is much of Richard;'s other work) and has some very funny lines in it.  You can see a brief synopsis here - http://junkscience.com/2012/04/17/andrew-bolt-mtc-shock-a-play-with-a-sceptic-as-hero/.  Richard is a constant source of references to contrarian views.  In our earlier discussions he relied extensively on conspiracy theory and extreme generalisation (A did X, X was wrong, therefore everything that A has ever done is wrong).  Making it clear that I was more interested in playing the ball than the man, he has resorted to supplying me with sources like Lindzen and now Morner.

Morner has published many papers on sea level.  His graph of the TOPEX/Poseidon data looks like this:

Fig. 2. Sea level changes in mm as recorded by TOPEX/POSEIDON between October 1992 and April 2000: raw data before any filtering or      
sliding mean average. The variability is high, in the order of F 5 – 10 mm. From 1993 to 1996, no trend is recorded, just a noisy record around      
zero. In 1997, something happens. High-amplitude oscillations are recorded; a rapid rise in early 1997 at a rate in the order of 2.5 mm/year,      
followed by a rapid fall in late 1997 and early 1998 at a rate in the order of 1.5 mm/year, and finally, in late 1998 and 1999, a noisy record with      
unclear trends. The new factor introduced in 1997 and responsible for the high-amplitude oscillations, no doubt, is the global ENSO event,      
implying rapid redistribution of oceanic water masses (characteristic for mode III in Table 1). This means that this data set does not record any      
general trend (rising or falling) in sea level, just variability around zero plus the temporary ENSO perturbations.      

Whereas, Cazenave and Nerem's, which is the basis for the IPCC AR4 looks like this:

Figure 5. Global mean sea level variations every 10 days      
from T/P (red circles, red triangles after T/P was moved to      
new ground track) and Jason (green squares) and after      
smoothing with a 60-day boxcar filter (blue line) [Leuliette      
et al., 2004]. No inverted barometer correction was applied      
to the altimeter data, and seasonal variations have been      
removed.      

These two graphs, supposedly presenting the same data at least for the first six years, show completely different representations, one suggesting that there is no sea level rise and the other that there is.  They can't both be true although they can both be wrong.  IPCC has relied on Cazenave and Nerem, while Morner doesn't even get a mention.  Morner on the other hand appears to have had a long career at Stockholm University concentrating on sea level during which he has published a considerable number of peer reviewed papers on the subject.

I have absolutely no idea how to deal with these conflicting conclusions.  The mere acceptance by the IPCC of the Cazenave and Nerem interpretation is not a sufficient basis to accept it is as valid.  Morner is explicit that he is representing raw data but in his other papers he is clearly very well aware of the limitations of satellite data and the complications generally of making any reliable measurements of sea level rise because of the multiple variables at play.  On the other hand, Cazenave and Nerem do not, at least to my untutored eye, make clear what they have done to the data if what they are showing is not the raw data, nor how they justify whatever corrections they have made.

My reading of Morner's papers do not suggest he's some kind of crank but I find it odd that I have not been able to find any refutation of his interpretations of the data; maybe I just don't know where to look.  As regards his statement about the British delegate confessing to tweaking the data in  order to establish the desired trend, people like Richard Bean love this stuff, it's manna from heaven for them.

Richard is a bright guy and I like to think that over time, presented with the scientific evidence he could be brought round to a better understanding of the climate threats of BAU.  I may be wrong about that but it does seem to me that it's people like him outside the science community that we need to convince.  Right now, he thinks that Morner's the man speaking the truth and the IPCC and it's scientists are pursuing a political agenda that isn't supported by the science.

Ultimately this is a communications issue and it seems to me that we have to confront it wherever we find it.  So, if anyone can explain to me how to reconcile these two conflicting conclusions from the same underlying data that would be another tick in the box and I'd be very grateful.

Robert Chris
The Open University

[Ken Caldeira]

Here is from Nereem et al (attached) rebutting the Moerner information pollution. Peer-review is an imperfect filter. It improves signal-to-noise, but is not completely effective at eliminating noise.

http://www.sciencedirect.com/science/article/pii/S0921818106002049

It would be nice if people would do a little due diligence before emailing this group with claims that are patently false.

------------------------- (quoted from Nereem et al ) ------------------

We feel compelled to respond to the recent article by Mörner (2004) because he makes several major errors in his analysis, and as a result completely misinterprets the record of sea level change from the TOPEX/Poseidon (T/P) satellite altimeter mission. One major criticism we have with the paper is that Mörner does not include a single reference to any altimeter study, all of which refute his claim that there is no apparent change in global mean sea level (GMSL) [see Cazenave and Nerem, (2004) for a summary]. The consensus of all other researchers looking at the T/P and Jason data is that GMSL has been rising at a rate of 3.0 mm/year (Fig. 1) over the last 13 years (3.3 mm/year when corrected for the effects of glacial isostatic adjustment (Tamisiea et al., 2005)).

Mörner gives no details for the source of the data or processing strategy he used to produce Fig. 2, other than to say it is based on “raw data”. Because the details of the analysis are not presented in his paper, we are left to speculate on how this result could have been obtained, based on our years of experience as members of the T/P and Jason-1 Science Working Team. Mörner was apparently oblivious to the corrections that must be made to the “raw” altimeter data in order to make correct use of the data.

As with any satellite data set, calibration and validation of the data must be performed after launch to determine if there are any instrumental errors, find the source of those errors, and evaluate their behavior over time. Satellite altimetry is somewhat unique in that many adjustments must be made to the raw range measurements to account for atmospheric delays (ionosphere, troposphere), ocean tides, variations in wave height (which can bias how the altimeter measures sea level), and a variety of other effects. In addition, the sea level measurements can be affected by the method used to process the altimeter waveforms, and by the techniques and data used to compute the orbit of the satellite. Early releases of the satellite Geophysical Data Records (GDRs) often contain errors in the raw measurements, the measurement corrections, and the orbit estimates that are later corrected through an on-going calibration/validation process defined by the T/P and Jason Science Working Team.

The original release of the T/P GDRs (as well as some subsequent re-releases) contained several errors that directly affect GMSL change. Based on our experience with these issues, and the shape of Fig. 2 in Mörner's paper, we believe that he used the original release of the T/P GDRs with no attempt to correct for two significant errors. One of the errors is caused by a drift in the TOPEX Microwave Radiometer (TMR). It was first observed in sea level via a comparison to tide gauges ( [Chambers et al., 1998] and [Mitchum, 1998]), and was verified to be caused by the TMR via comparisons to other orbiting microwave radiometers and radiosondes (Keihm et al., 2000). It caused a drift of nearly − 1.2 mm/year in measured GMSL until early 1998, and then a bias of − 5 mm. A second major error was introduced when the redundant TOPEX altimeter was turned on in early 1999 due to degradation in the original instrument (Chambers et al., 2003). Since the electronics of the redundant altimeter were different, it caused an apparent bias in the GMSL measurement related to the Sea State Bias (SSB). The sense of the bias was such to cause an incorrect sudden drop in GMSL from the end of 1998 to the beginning of 1999 of nearly 10 mm. This drop is apparent in Fig. 2 of Mörner's paper (and in comparison to tide gauge data (Mitchum, 2000)). This error is removed when an updated SSB model is applied (Chambers et al., 2003). Data with these corrections applied are available from both the U.S. and French processing centers, as well as products to correct the original GDRs.

When care is taken to make these corrections, the rate of sea level change over the entire T/P mission is 3.0 ±0.4 mm/year (http://sealevel.colorado.edu), 3.3 mm/year when corrected for the change in ocean volume due to glacial isostatic adjustment (Tamisiea et al., 2005). In light of this, the statement by Mörner that “This means that this data set does not record any general trend (rising or falling) in sea level, just variability around zero plus the temporary ENSO perturbations” is completely false and is based on his erroneous data processing. Mörner's paper completely misrepresents the results from the T/P mission, and does discredit to the tremendous amount of work that has been expended by the Science Working Team to create a precise, validated, and calibrated sea level data set suitable for studies of climate variations. Finally, Mörner ignores substantial other oceanographic (e.g. [Levitus et al., 2001], [Antonov et al., 2002], [Munk, 2003] and [Willis et al., 2004]) and cryospheric (e.g. [Dyurgerov and Meier, 2000], [Rignot et al., 2003], [Krabill et al., 2004] and [Thomas et al., 2004]) evidence of sea level rise which corroborate the altimeter observations.

_______________
Ken Caldeira

Carnegie Institution Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA
+1 650 704 7212 kcal...@carnegie.stanford.edu
http://dge.stanford.edu/labs/caldeiralab  @kencaldeira

Currently visiting  Institute for Advanced Sustainability Studies (IASS)  

and Potsdam Institute for Climate Impact Resarch (PIK) in Potsdam, Germany.

[Mike MacCracken]

Dear Robert--In response to a query that I sent, John Church, co-author of
the sea level chapter in the IPCC Third Assessment Report, sent along a set
of articles in response to the writings of Morner on sea level rise. Four
are attached and one will come in a separate message due to size of file.

Mike MacCracken

------ Forwarded Message
From: John Church <John....@csiro.au>
Date: Tue, 1 May 2012 06:43:09 +1000
Subject: RE: Found the Nereem et al rebuttal

Dear Mike

There were several rebuttals to the Morner papers as well as the Nerem
Paper. I think they are all attached

Regards
John

[Mike MacCracken]

Dear Robert--Fifth file attached. Mike

[David Appell]

It is astonishing to me (and disappointing) that anyone would present
raw satellite data in this context in a scientific paper -- as if
unaware that satellites are influenced by many factors that need to be
corrected for. And that it would pass even minor peer-review.

BTW, another factor that influences low-orbiting satellites are solar
storms, which can heat the upper atmosphere, causing it to expand,
which increases atmospheric drag on satellites. (TOPEX/Poseidon
orbited at a relatively low altitude of 1,330 km.)

David

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