Finally: JPL intends to get a GRASP on accurate sea level and ice measurements

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.

USGS Benchmark on Mt. Diablo – Image from geocaching.com

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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GlynnMhor

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.

eqibno

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…

Alan Watt, Climate Denialist Level 7

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)?

H.R.

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.

John Stover

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

Stuart

@ Alan Watt 12:42 pm
The answer one chooses depends on one’s geo-politics.

Bloke down the pub

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.

Alcheson

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.

Luther Wu

Stuart says:
October 30, 2012 at 12:53 pm
@ 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.

richardscourtney

Anthony:
You say

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:

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

Rob uk
JJ

“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.

Dr T G Watkins

Great comment from John Stover (12.50).

Kev-in-Uk

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!)

John Peter

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.

“This promises to rewrite what we know about sea level rise and acceleration, ice extent and ice volume loss measured from space.”

Unsettling.

Taphonomic

“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?

Dave

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.

Berényi Péter

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.

Jimbo

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.

Darren Potter

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

Brewster

Unfortunately the US VLBI network may be forced to shut down, possibly eliminating full global VLBI coverage for GRASP
http://physicsworld.com/cws/article/news/2012/aug/22/us-telescopes-faced-with-closure

Rob uk

George Monbiot
Fraser Nelson makes the biggest blunder of his career by putting Nils-Axel Mörner’s, a serial promoter of nonsense, in his magazine
http://www.guardian.co.uk/environment/georgemonbiot/2011/dec/02/spectator-sea-level-claims

Ray Boorman

For me, it has always been hard to imagine that you can measure, from a platform orbiting at a constantly changing altitude, something as changeable as sea level, (waves, tides, gravity bulges), to an accuracy measured in millimetres. If they showed error bars for these calculations, would the possible errors exceed the headline figures? As “alcheson” says above, it is only the sea level relative to the coastline that matters in the real world.

Kev-in-Uk

Not really in my knowledge base but another way of looking at it might be in relation to GPS accuracy. GPS can accurately place to within around 0.1 or 0.2m, I believe(?) – and that is using half a dozen or more ‘geostationary’ satellites to get the best precision via cross-referencing (I think also with cross referencing to fixed land bases??) So, if they can only do that with GPS, how the heck can they better with ‘single’ satellite measurements of a moving surface?.

AlexS

“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.”
-Maybe it can’t be resolved.
“Sorry, that’s just the way I am.”
-It is knowledge. If anyone has some knowledge of technology it is easy that know that all this claims of accuracy are bogus. A typical laser rangefinder has error of mm and we talking about 10km distance with both objects stationary.

Larry Ledwick (hotrod)

Reinterpret satellite altimetry and tide gauge records to determine global mean sea level rise relative to the GRASP-based TRF – how is 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

Unfortunately they betray their bias and expected outcome in this presentation, they are assuming as a given that both are accelerating.
If they were unbiased, the wording would be something like “Determine if sea level is changing” and “Determine if Ice mass is changing, and the direction of those trends.”
Unfortunately this looks like a problem of confirmation bias in action they are trying to verify and increase the precision of the presumed trend and accelerations. No statement of any uncertainty of those basic assumptions.
Larry

Berényi Péter says:
It is not only the missing heat they should look for now, but the missing water as well.

Lolz, good one.
I think most of it ended up in the water table in Yorkshire, judging by the amount of rain we got this ‘summer’.

Matt G

This is really poor show NASA, one minute temperature satellites aren’t recording data suiting your agenda, so claim there not good enough and use only land station data in the awful GISS, which invents data interpolated from hundreds of miles away. Now the sea levels aren’t supporting data with regards to your agenda, now want to build a satellite that apparently the same technology is not good enough for the GISS. Does hypocrite have to be included in your CV working at NASA or are people within having a disagreement?
Although this satellite is probably what we have been waiting for regarding trying to record more accurate sea level changes. Lets face it there has been two human changes in the data over recent years for no scientific reason, other to support further rises. One already quoted and the other, GIA correction is only applied to the global MSL time series, and has been estimated as approximately -0.3 mm/year [Peltier, 2006]

Rob R

Spock: “It’s knowledge Jim, but not as we know it.”

Just Say NO!
To muslim outreach de-fund NASA NOW!

This is a good first step in getting our “science” on a scientific basis instead of the ego driven hubris of modelers. I would think that we should be getting more real bang for our investment buck too.

Gary Pearse

Well we’ll wait and see if the instrument needs adjusting. In any case, the error in the current sea level rise (ice thickness etc.) must be noticeable and in the direction stated or there would be no need for this new equipment. I’m impressed that when the edifice begins to collapse it takes so much with it – one thing after the other. I guess thats what happens when the whole CAGW thing has been built in secret by a group of one mind with limitless support and funds and the power to gatekeep the science. There is not much holding it all together.

Jim Clarke

If GRASP is a step to more accurate measurements, I am all for it. What we have now gives the warmists an excuse to make claims that are within the very large (relatively speaking) error range of the current instruments. Decreasing the error range will work in favor of climate realists.
As for the money…it employees educated and talented technicians and engineers, who have made good life choices to be contributing members to society. The amount we spend on this satellite would be a tiny fraction of the amount we spend enabling drug addicts to avoid getting real help for their problems (just one example). We live in a society that rewards those making bad life choices and punishes those making good life choices. Talk about being unsustainable!

Neil Jordan

American Council on Surveying and Mapping offers additional practical information on measuring sea level. A reprint of their December 2008 article is posted here:
http://tidesandcurrents.noaa.gov/publications/Understanding_Sea_Level_Change.pdf
Note that surveying practice is to measure sea level over a “tidal epoch”, which is defined as the 18.6 year lunar cycle (Metonic cycle in some references). See Figure 2 in the article. Quoting from the ACSM article (emphasis added in upper case for last sentence):
“Although current research on global sea level rise has been
focused on determining the water volume added from the melting
of glaciers and the extent of the thermal expansion of the oceans
due to global warming there is another aspect of climate and
sea-level change that needs to be considered. IT IS THE INTERANNUAL-
TO-DECADAL SEA LEVEL SIGNAL WHICH CAN BE LARGER THAN THE
ACTUAL GLOBAL SEA LEVEL TREND.”

KnR

Sorry but while Dr Doom hangs around NASA like tombstone ready to ‘adjust to death’ anything he does like like , this is not going to work.

Louis Hooffstetter

I second what John Stover & Kev-in-UK say. The GPS systems using Continuously Operating Reference Stations (CORS) are the most cost effective and accurate way of measuring sea level. Data is collected continuously 24/7/365 from multiple satellites, which allows crustal motions to be corrected for, and therefore eliminated. The result is absolute sea level motion with sub millimeter accuracy. GPS is an under-utillized and under-rated source of valuable sea level and plate tectonic motion data.

Whatever follows on from this, I trust we’ll have some sound wayback data recorded,
Given the extraordinary statement to Mörner in 2003: ” … we had to do it, because otherwise we would not have gotten any trend!”, I anticipate further scope for adjusters and tinkerers.
I go with Kev-in-Uk’s comments on GPS. My $80 in-car GPS gets speed limit changes to within a couple of metres at 100km/hr, so I would expect fixed GPS altimetry to be more accurate than anything else.
With regard to tide gauges, I keep an eye on three locally, out of about 40+ in NQ Australia, and have only noted small cyclical changes.
Ok – there are differences between tide gauges:
Equipment: (radar, laser ranging);
Purpose: (keel clearance, storm surge calculations, sea-level change)
Also: Land changes (subsidence, uplift); Coastal topography – characteristics and changes.
All differ, none are necessarily “wrong”.
MSQ (Maritime Safety Queensland) lists 44 operational permanent tide gauges in Queensland:
Port Authorities – 11; MSQ – 2; AMSA (Australian Maritime Safety Authority) – 5; DERM (State agency) – 24; NTC (BoM – Federal agency) – 2.
Some of these are co-located, so there is some scope for detecting tinkering, use of model output instead of observations.
Mörner’s paper: “The great sea-level humbug” (covered above)
JCU paper 2008: “Mid-late Holocene sea-level variability in eastern Australia”
http://eprints.jcu.edu.au/1855/

Oso Politico

I don’t know how much credence the NOAA has, but take a look at this link: http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml
Notice all of the little green arrows pointing up and indicating a positive rise in sea level. Well, if you look at the box below you will see that ‘green’ is for 0 to 3 mm per year. Zero. So one doesn’t know if there is really some indication of a rise. They could all be zero, for all we know.
The point being, the presentation of the data and analysis can be heavily biased in spite of showing null results.

Larry Ledwick (hotrod) says:
October 30, 2012 at 2:36 pm

Reinterpret satellite altimetry and tide gauge records to determine global mean sea level rise relative to the GRASP-based TRF – how is 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

Unfortunately they betray their bias and expected outcome in this presentation, they are assuming as a given that both are accelerating.
If they were unbiased, the wording would be something like “Determine if sea level is changing” and “Determine if Ice mass is changing, and the direction of those trends.”
Unfortunately this looks like a problem of confirmation bias in action they are trying to verify and increase the precision of the presumed trend and accelerations. No statement of any uncertainty of those basic assumptions.

Either that, or this is a canny way to get funding in the current environment.

The graph merges tide guage and satellite, as if the tide guage data stopped being recorded in 1990.
What is the tide guage record from 1990 to 2012?

Nasa has proven itself unworthy of funding. As long as they employ charlatans like James Hansen, they can not be trusted to objectively look at data.
The importance of finding “evidence” of sea-level rise (a preconceived expectation, based on their statement) is far outweighed by the 16+ trillion dollars in deficit that we are carrying around.
Not only “no,” but hell no.

A Crooks

What these NASA guys need is an excuse to tap into a budget line to ensure their pay checks into the future. It will also give them 17 years breathing space before any new trend becomes “significant.” I’m surprised they didnt ask for money to build a satellite that could travel back in time and measure sea levels retrospectively. Now that would have required a budget line that would have kept them in cream forever!

Geoff

Rob UK – The Monbiot post you link to seems to be a guest post by Mark Lynas, who is among other things was “climate adviser to the [former, now deposed] President of the Maldives”. It would be interesting to look into Mark’s possible role in the staged propaganda piece of the underwater Maldives cabinet meeting (see http://news.bbc.co.uk/2/hi/8311838.stm ).

DR

Whatever happened to Cryosat? Wasn’t that supposed to settle the questions on Arctic ice extent and volume?
What’s the next mission, STRAW? GRACE GRASP STRAW….sounds about right.

Jimmy Haigh

Are there any alarmists out there prepared to comment?