A climate science bombshell: New proposal from NASA JPL admits to “spurious” errors in current satellite based sea level and ice altimetry, calls for new space platform to fix the problem.
People send me stuff. Today it is a PowerPoint presentation from NASA JPL that touts the new GRASP (Geodetic Reference Antenna in Space) satellite project. I’d say it is more than a bit of a bombshell because the whole purpose of this new mission is to “fix” other mission data that apparently never had a stable enough reference for the measurements being made. This promises to rewrite what we know about sea level rise and acceleration, ice extent and ice volume loss measured from space.
What is most interesting, is the admissions of the current state of space based sea level altimetry in the science goals page of the presentation:
The difference between tide gauge data and space based data is over 100% in the left graph, 1.5 mm/yr versus 3.2mm/yr. Of course those who claim that sea level rise is accelerating accept this data without question, but obviously one of the two data sets (or possibly both) is not representative of reality, and JPL’s GRASP team aims to fix this problem they have identified:
TRF errors readily manifest as spurious sea level rise accelerations
That’s a bucket of cold water reality into the face of the current view of sea level rise. It puts this well-known and often cited graph on Sea Level Rise from the University of Colorado (and the rate of 3.1 mm/yr) into question:
What’s a TRF error? That stands for Terrestrial Reference Frame, which is basically saying that errors in determining the benchmark are messing up the survey. In land based geodesy terms, say if somebody messed with the USGS benchmark elevation data from Mt. Diablo California on a regular basis, and the elevation of that benchmark kept changing in the data set, then all measurements referencing that benchmark would be off as well.
In the case of radio altimetry from space, such measurements are extremely dependent on errors related to how radio signals are propagated through the ionosphere. Things like Faraday rotation, refraction, and other propagation issues can skew the signal during transit, and if not properly corrected for, especially over the long-term, it can introduce a spurious signal in all sorts of data derived from it. In fact, the mission summary shows that it will affect satellite derived data for sea level, ice loss, and ice volume in GRACE gravity measurements:
In a nutshell, JPL is saying we don’t have an accurate reference point, and therefore the data from these previous missions likely has TRF uncertainties embedded:
The TRF underlies all Measurement of the Earth
Without that stable Terrestrial Reference Frame that puts the precision of the baseline measurements well below the noise in the data, all we have are broader uncertain measurements. That’s why the plan is to provide ground based points of reference, something our current satellite systems don’t have:
To help understand the items in the side panels:
GNSS = Global Navigation Satellite System – more here
SLR = Satellite Laser Ranging – more here
DORIS = Doppler Orbitography and Radiopositioning Integrated by Satellite – more here
VLBI = Very Long Baseline Interferometry – more here
Taken together, these systems will improve the accuracy of the TRF, and thus the data. It’s rather amazing that the baseline accuracy didn’t come first, because this now puts all these other space based measurement systems into uncertainty until their TRF issues are resolved, and that’s an inconvenient truth. We’ll never look at satellite based sea level data or GRACE ice volume data in quite the same way again until this is resolved.
PowerPoint here: Poland 2012 – P09 Bar-Sever PR51 (PDF)
More info: http://ccar.colorado.edu/~nerem/EV-2_GRASP-final.pdf
UPDATE: Here’s an estimate of impacts:
Source: http://www.gps.gov/governance/advisory/meetings/2011-06/bar-sever.pdf
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I wonder how large the error is compared to the effect being measured?
The comparison chart suggests it to be relatively small, but what if the error exceeds the effects?
I never believed it in the first place. The pretence that it could possibly be so accurate was always bogus.
Whenever you look at the post-glacial sea-level record, it is easy to see the rapid rise (punctuated by the Younger Dryas) which then peaked broadly several thousand years ago. The last thousand years or so appear to be on a slight decline. What with isostatic rebound etc. one would expect no sea-level rise if not a continuing fall with time.
We are heading back into a glacial epoch, after all…
So assuming this goes into place, don’t we have the problem of how to splice the new instrumental data on to the existing? Which means we will need some kind of correction to normalize the earlier records to the new reference. Or do we give up on an aggregated instrumental record and just say the satellite record for sea-level begins in 2013 (or whenever)?
So, we’ve been getting sea level data accurate to 0.02mm +/- 2m?
[/nonsense]
I should hope a next generation satellite is greatly improved over existing systems.We do need to get a handle on getting good measurements of the Earth’s features. Let’s hope GRASP exceeds its reach.
I have had a lot of experience with various types of space based measurements and we have always been aware of how many errors can enter the systems which ALWAYS make the data estimates. For instance, the ephemeris for the spacecraft always has some degrees of uncertainties so measurements taken from the spacecraft that depend upon time delay of arrival (and they almost do except for imagery) will be off at least somewhat. The errors are never consistent so you cannot just apply a correction factor. Other errors are occasioned because we don’t understand the geospatial aspects of the surface of the earth since the earth really isn’t round and the various kinds of relief on the surface also affect measurements as do different types of ground cover. There are many, many other factors entering into the process, none of which can be constrained.
Given all of that while we might get closer to accuracy, it can never be truly as accurate as ground based measurements. GPS is only as accurate as it because we use multiple spacecraft simultaneously. None of the data birds have that kind of multiple, overlapping measurements.
Cheers,
John
@ur momisugly Alan Watt 12:42 pm
The answer one chooses depends on one’s geo-politics.
Measured with a micrometer, marked with a piece of chalk, and cut with a gas torch.
I don’t like that “3-year lifetime” thing. I realize it is an expectations game, short the useful lifetime up front and later brag about it exceeding its plan later. But this has got to stop. Taxpayers should take note of these never-ending expenditures and demand the heads of those signing off on them.
Additionally, it introduces extra variables into the long term dataset. In 3 years another bird needs to be launched which will be in a slightly different orbit and which will have different equipment, then we will stitch together their data and compare them without any regard for possible variation, much like we do now with our 30+ so-called pristine satellite record.
Whoa!
Quote:
Reinterpret satellite altimetry and tide gauge records to determine global mean sea level rise relative to the GRASP-based TRF – how sea level accelerating
Reinterpret satellite ICESat and GRACE data records to determine ice mass loss relative to the GRASP-based TRF – how is ice mass loss accelerating
Shouldn’t the be “reinterpreting” in order to see if global mean sea level either rising or falling and ice mass is either rising or falling?
Just wondering.
Still in the end… it’s only the sea level relative to land levels that are important and that is by far best measured by tide gauges on the ground. After calibration, GRASP could claim the oceans are rising at 1 meter per year and it wouldn’t mean squat. If tide gauges show 1.5mm/yr, it will still be the number that counts.
Stuart says:
October 30, 2012 at 12:53 pm
@ur momisugly Alan Watt 12:42 pm
The answer one chooses depends on one’s geo-politics.
___________________
If past is prologue, the warmistas have nothing to worry about.
NASA’s James Hansen is on the job.
Anthony:
You say
I have always said I think both the tide gauge data and space based data lack adequate accuracy and lack adequate precision. And, sadly, I am not convinced that the additional satellite will correct this problem because of the rates and the changes in surface heights relative to sea level across the planet.
Richard
REPLY: You have to start somewhere and this is a good place to start to make sure the previous work is properly referenced. All measurement systems evolve. – Anthony
Seems Nils-Axel Morner may be correct.
http://www.21stcenturysciencetech.com/Articles_2011/Winter-2010/Morner.pdf
“This promises to rewrite what we know about sea level rise and acceleration, ice extent and ice volume loss measured from space.”
No, it promises to provide an excuse for rewriting what, inconveniently, aint happening.
Great comment from John Stover (12.50).
I can understand that radio telemetry/altimetry is inaccurate for transmittal reasons. What I cannot understand is how they can then ‘work’ back to a supposed accuracy of 1/10s of mm per year on a moving irregular surface! Sorry, but it just doesn’t compute……..
To my mind – it would be like estimating the surface area of a the leaves on a large tree from a mile away, with a stiff wind blowing! (at thats just in the summer!)
Reference RobUK above, there is also this PDF http://www.21stcenturysciencetech.com/Articles_2011/Winter-2010/Morner.pdf
In which Dr. Nils-Axel Mörner actually states:
“Now, back to satellite altimetry, which shows the water, not
just the coasts, but in the whole of the ocean. And you measure
it by satellite. From 1992 to 2002, [the graph of the sea level]
was a straight line, variability along a straight line, but absolutely
no trend whatsoever. We could see those spikes: a very rapid
rise, but then in half a year, they fall back again. But absolutely
no trend, and to have a sea-level rise, you need a trend.
Then, in 2003, the same data set, which in their [IPCC’s]
publications, in their website, was a straight line—suddenly it
changed, and showed a very strong line of uplift, 2.3 mm per
year, the same as from the tide gauge. And that didn’t look so
nice. It looked as though they had recorded something; but
they hadn’t recorded anything. It was the original one which
they had suddenly twisted up, because they entered a “correction
factor,” which they took from the tide gauge. So it was
not a measured thing, but a figure introduced from outside. I
accused them of this at the Academy of Sciences 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!” and then he continues
“That is terrible! As a matter of fact, it is a falsification
of the data set. Why? Because they know the answer. And
there you come to the point: They “know” the answer; the
rest of us, we are searching for the answer.”
So the sooner this “introduced trend” is replaced with reality the better.
Cracking post Anthony. John Daly was saying this 16 years ago. The error range was +/- 75mm at best. That’s twice the sea level rise since 1993. Signal lost in noise indeed. I don’t see how this new gizmo is going to recover those data though. Changes in orbits due to solar wind variation etc are not steady or regular in magnitude.
There is also the human factor:
“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.’”
-Nils -Axel Morner-
http://tallbloke.wordpress.com/2011/12/02/sea-level-scare-stories-simply-scandalous/
I hope JPL will be telling us a lot more about their methodology than the article reveals so far. Well done for flagging up this important measurement issue.
Unsettling.
“TRF errors readily manifest as spurious sea level rise accelerations”
I feel like Captain Louis Renault in Rick’s Café Américain; now where are my winnings?
To me it sounds like the folks from JPL are looking for something to do… and funding to do it with. What better way than to say that there are problems with a satellite used to determine the effects of global warming.
I wonder how many folks would be unemployed without something new to work on.
They are simply getting desperate. Finding the appropriate kind of errors may help to hide the decline perhaps. For there is a decline indeed in satellite measured rate of sea level rise. Raw data from the CU Sea Level Research Group clearly shows that. There are 678 data points in that data file, since Dec 16 1992. The first 339 points show a rate of 3.5 mm/year, while the second half is 2.25 mm/year. That’s a 55% decrase in rate, which is huge. Especially because sea level rise is projected to accelerate.
It is not only the missing heat they should look for now, but the missing water as well.
Thanks John Stover for your insight.
I for one have always been sceptical about satellite measurements sea level rise to within a few millimeters. Sorry, that’s just the way I am.
Sorry NASA. You have hoodwinked us Taxpayers before on AGW. Your past results have been Alarmists and unscientific. And you have failed to purge yourself of the likes of Hansen.
As such, GRASP looks to be another excuse for NASA to get a Grasp on OUR money, while Grasping at the straws of Global Warming.
Answer: Just say No to GRASP