There’s a paper (Shepherd et al) on ice loss and sea level rise that has been making the rounds in media (such as this article in Science Recorder, claiming it validates global warming) that is causing some stir, mainly because it has a powerfully written press release combined with a volume of researchers (47 scientists), plus additional never before used together satellite data, because more data and more scientists is always better, right?
Here’s the press release where they claim to have “clear evidence”. A deconstruction follows using NASA JPL’s own internal program documents showing that the “certainty” claimed in Shepherd et al really falls apart for lack of a stable reference for the data.
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From the University of Leeds
Clearest evidence yet of polar ice losses
International satellite experts release definitive record of ice sheet changes
An international team of satellite experts has produced the most accurate assessment of ice losses from Antarctica and Greenland to date, ending 20-years of uncertainty.
In a landmark study, published on 30 November in the journal Science, the researchers show that melting of the Antarctic and Greenland ice sheets has contributed 11.1 millimetres to global sea levels since 1992. This amounts to one fifth of all sea level rise over the survey period.
About two thirds of the ice loss was from Greenland, and the remainder was from Antarctica.
Although the ice sheet losses fall within the range reported by the IPCC in 2007, the spread of the IPCC estimate was so broad that it was not clear whether
Antarctica was growing or shrinking. The new estimates are a vast improvement (more than twice as accurate) thanks to the inclusion of more satellite data, and confirm that both Antarctica and Greenland are losing ice.
The study also shows that the combined rate of ice sheet melting has increased over time and, altogether, Greenland and Antarctica are now losing more than three times as much ice (equivalent to 0.95 mm of sea level rise per year) as they were in the 1990s (equivalent to 0.27 mm of sea level rise per year). The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) is a collaboration between 47 researchers from 26 laboratories, and was supported by the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA).
Led by Professor Andrew Shepherd at the University of Leeds and Dr Erik Ivins at NASA’s Jet Propulsion Laboratory, the study combines observations from 10 different satellite missions to develop the first consistent measurement of polar ice sheet changes.
The researchers were able to reconcile the differences between dozens of earlier ice sheet studies through careful use of matching time periods and survey areas, and by combining measurements collected by different types of satellites.
Professor Shepherd, who coordinated the study, said: “The success of this venture is due to the cooperation of the international scientific community, and due to the provision of precise satellite sensors by our space agencies. Without these efforts, we would not be in a position to tell people with confidence how the
Earth’s ice sheets have changed, and to end the uncertainty that has existed for many years.” The study also found differences in the pace of change at each pole.
Dr Ivins, who also coordinated the project, said: “The rate of ice loss from Greenland has increased almost five-fold since the mid-1990s. In contrast, while the regional changes in Antarctic ice over time are sometimes quite striking, the overall balance has remained fairly constant – at least within the certainty of the satellite measurements we have to hand.”
Commenting on the findings, Professor Richard Alley, a climate scientist at Penn State University who was not involved in the study, said: “This project is a spectacular achievement. The data will support essential testing of predictive models, and will lead to a better understanding of how sea-level change may depend on the human decisions that influence global temperatures.”
‘A reconciled estimate of ice sheet mass balance’ by Prof Shepherd et al is published in Science on 30 November 2012, DOI: 10.1126/science.1228102.
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All well and good, and it looks like a home run for Professor Andrew Shepherd at the University of Leeds and Dr Erik Ivins at NASA’s Jet Propulsion Laboratory and the team of 45 others if you just read the press release. But, let’s look a bit deeper, the paper abstract reads:
A Reconciled Estimate of Ice-Sheet Mass Balance
Abstract
We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth’s polar ice sheets. We find that there is good agreement between different satellite methods—especially in Greenland and West Antarctica—and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by –142 ± 49, +14 ± 43, –65 ± 26, and –20 ± 14 gigatonnes year−1, respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 ± 0.20 millimeter year−1 to the rate of global sea-level rise.
Note the key words here “satellite altimetry, interferometry, and gravimetry data sets” along with the second named author “Dr Ivins, who also coordinated the project…at NASA’s Jet Propulsion Laboratory”
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Hold that thought about the key words, and now read this, excerpted from our previous report: Finally: JPL intends to get a GRASP on accurate sea level and ice measurements
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.
This recent internal PowerPoint presentation (obtained from an insider) from NASA JPL 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, as shown in the “Key science goals” slide:
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:
That list of satellites, TOPEX, JASON 1-3, ICESAT1-2, and GRACE 1-2 pretty much represent all of the satellite data used in the new Shepard et al study released this week A Reconciled Estimate of Ice-Sheet Mass Balance.
In a nutshell, other JPL scientists (Yoaz Bar-Sever, R. Steven Nerem, and the GRASP Team) are saying we don’t have an accurate reference point for the satellites, and therefore the data from these previous satellite missions likely has TRF data uncertainties embedded. They say clearly in their PowerPoint presentation that:
The TRF underlies all Measurement of the Earth
And, most importantly, they call for a new space program, GRASP, to fix the problem.
Without that stable Terrestrial Reference Frame that puts the precision of the baseline satellite measurements well below the noise in the data, meaning 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.
See the JPL PowerPoint here: Poland 2012 – P09 Bar-Sever PR51 (PDF)
Summary:
1. JPL admits that satellite measurement of the Earth has issues because a stable Terrestrial Reference Frame was never established for any of the satellite programs. It’s like setting out to do a terrestrial survey without having an accurate benchmark first. This puts all subsequent data derived with the stable benchmark (the stable TRF) into question.
2. The lack of a stable TRF affects most if not all satellite programs used in this new Shepherd et al paper ‘A reconciled estimate of ice sheet mass balance‘ including ICESAT and GRACE, upon which the paper heavily relies.
3. In searching both the full paper (which I purchased from AAAS) and from the extensive supplementary materials and information (SM-SI available here: Shepherd.SM-SI.pdf ) for Shepherd et al, I find no mention of TRF or “Terrestrial Reference Frame” anywhere. It appears that all 47 authors are unaware of the TRF stability issue, or if they were aware, it was never brought to bear in peer review to test the veracity of the paper and its conclusions from the satellite data. Section 3 of the Shepard et al SM-SI deals with uncertainty, but also makes no mention of the TRF issue.
4. The lack of a stable TRF puts all of the space based geodetic data into question, thus the conclusions of the Shepherd et al paper are essentially worthless at the moment, since there isn’t any good way to remove the TRF error from the data with post processing. If there were, the GRASP team at NASA JPL wouldn’t be calling for a new satellite platform and mission to solve the problem. Obviously, this isn’t an issue they take lightly.
In my opinion, the folks at NASA JPL really should get those two teams talking to one another to get a handle on their data before they make grand announcements saying :
An international team of satellite experts has produced the most accurate assessment of ice losses from Antarctica and Greenland to date, ending 20-years of uncertainty.
A good first step would be to get the GRASP mission funded and then go back and redo Shepherd et al to see if it holds up. Until then, it’s just noisy uncertain data.
UPDATE: Figure 4 in the Shepherd et al paper shows clearly how uncertain the GRACE and other data is. They used a brief bit of Laser Altimetry data, shown in green. Laser Altimetry is more accurate that the radar/microwave based data from the other satellite platforms, and is one of the keystones specified for the proposed GRASP mission to clean up the noisy radar/microwave based data.
Note that the Laser Altimetry data in green is essentially flat across the short period where it is included in all four panels, though there is a slight drop in Greenland, but the period is too short to be meaningful.
The uncertainty is quite clear in Table 1, which has error ranges larger than the data in some cases:
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“In my opinion, the folks at NASA JPL really should …” shut the ‘H’ up about any ice loss and sea level rise claims until they have a handle on Terrestrial Reference Frame. They are showing themselves to be nothing more than political tools.
“An international team of satellite experts has produced the most accurate assessment of ice losses from Antarctica and Greenland to date, ending 20-years of uncertainty.”
Something akin to Maxwell Smart’s admission of ‘Missed it by that much’.
As for ending the uncertainty, all they have done is cast doubt on their current claims, by acknowledging their previous accurate claims were in fact inaccurate.
Do any of those posters eager to reject the finding of exceptional ice melting exceeding any since the start of the Holocene care to detail what error the problems with TRF impart to the data ?
Does it cause an error of less than 1%, less than 5% or more than 10% ?
Unless you know the magnitude of the error you cannot just discard data you dislike.
REPLY: In your zeal, you clearly don’t understand what is going on here. The error won’t be known until they can compare the data in hand to the stable baseline. – Anthony
Notwithstanding the Envisat story, even before the satellite data were considered unaffected by orbital decay… the sea level rise was minimum.
Actually, the science is fairly certain with Earth’s water (oceans and seas) levels. Mostly due to soil erosion, water levels are rising. It will take megatons of data, and megayears of arguing, to know with any certainty the rate of rise. To link the rise to CO2, is where the science stops and the BS begins.
All I want to know is when is my place back from the beach going to be prime Esplanade property?
I’m trying to tell the punters it won’t be long now and to get in early but the thick-heads are in denial.
How do I get the joint listed as a Terrific Reference Frame or whaddyamacallit thingy with these whitecoats to impress them? Do they do after hours assessments or do they just use Google Earth and I don’t really need to be there to let them in?
The sealevel data graph shows tidal guages and satellite data have different rates. What happened to the tidal guage data after 1992? Why don’t we see that data continuing to present?
Is this because it bad news for both sides, that there is an increased rate after 1992 but less than the altimetry data?
So the melting of ice might have contributed a 5th of the total measured sea level rise and this amounts to just 2 inches over the next one hundred years and this might be attributable to CO2 (except for the last 16 years cause there’s been no warming for 16 years). On this basis they want me to turn off my central heating?
@izen,
As Anthony pointed out in his direct reply to you, the magnitude of the errors to to TRF problems can not be known until a stable TRF is established.
If the error range is large enough that could actually mean that the real trend is the opposite sign from what the current satellite data show.
This means that none of the satellite measurements reliant on a TRF can be trusted until a stable TRF is established. Even the sign of the trend can not be trusted.
“Sheet Mass Balance Inter-comparison Exercise”
Translation: we did a ‘meta-analysis’ combining apples, oranges, pineapple chunks, corn syrup, and miniature marshmallows into a fruit salad and declared it nutritious.
First post.
Go Gentle please, been lurking for a while now
http://www.esa.int/esaCP/SEMP7ZE16AH_index_0.html?utm_source=dlvr.it&utm_medium=twitter
Another story to worry us (well, apparently)
“Northern hemisphere snow cover low record”
“faster than climate models”
I’m noticing a pattern. Regardless of whether these papers are support skeptical viewpoints or non-skeptic viewpoints it’s all happening at rates not predicted by the Models. All this tells me is that we still have no idea what is going on. So how can we possibly base any sort of policy on it? For now we just need to keep going, adapt to what ever is happening as it happens and if we ever get to the point where we can predict what is happening base policy on that.
^ Don’t think we’ll ever reach that point.
Yours a Liberal Skeptic.
Does anyone have a quick conversion factor between 100 Gt water = X mm Sea Level @ur momisugly 4 deg C ?
The first chart with the red Tide Gauge and Blue Altimetry set me off. Another “Hide the Decline” in the making. We start measuring Altimetry in 1993, ok. But you expect me to believe that we STOPPED measuring Tide Gauges in 1993? No, they just stopped plotting the tide gauge data because — why? — it disagrees with the Altimetry? Hmmm?
“The lack of a stable TRF puts all of the space based geodetic data into question, thus the conclusions of the Shepherd et al paper are essentially worthless at the moment, since there isn’t any good way to remove the TRF error from the data with post processing.” You wanna bet, matey???? 🙂 They’ll find a way, that’s why they “reinterpreted” the satellite data, in an effort to “reconcile” it!
I have a real problem with people who want to “re-interpret” or “re-evaluate” something that didn’t show them what they wanted it to show, without “processing”, adjusting”, “refining”, or “smoothing” it afterwards to give them the picture they wanted to see!! Or is it just l’ill ol me? What a cynical old b’stard I have become in my seniority! They seem to have forgotton the fact that UNIPCC AR4 2007 SPM concurred that the Arctic was warmer in the 1940s than it is today, amongst many other things they “agree” with, particularly differences between satellite/radio sond temperature data & models being “largely resolved”, whatever that might mean!!! They just can’t seem to arrive at the logical conclusion without invoking the “Precautionary Pinciple”!
You guys are deluded if you imagine the TRF-uncertainty is big enough to change the current trend to an “opposite trend”. Check what the maximum size of the uncertainty is (hint: the JPL PowerPoint) and post it here please (I tried to do that when it was 1st reported but nobody on WUWT gived a damn).
Note also that the reference-frame affects altimetry- and gravimetry measurements differently and that it does not really affect the SAR/InSAR velocity measurements. SAR, altimetry and gravimetry show pretty much the same thing, as demonstrated in Shepherd et. al.
The GIA-models have a much larger uncertainty on Antarctica where one just cannot place GPS-stations where one pleases (no bedrock nearby on huge areas). On Greenland the problems are much smaller as the ice-sheet is relatively narrow and GPS-station can be places relatively nearby. Use of a different GIA-model will NOT reduce the Greenland mass-loss estimate by 50%.
REPLY: Look at the short period of Laser Altimetry data in Figure 4 – essentially flat. Note that LA is one of the keystones of the GRASP mission to clean up the noisy data which in table one has quite error bars. If you are makign bold predictions, would you not want to get the best available data?
And, why would you need to hide your identity at ESA if you are so sure of your claims? – Anthony
Stephen Rasey, there are zero tide-gauges in the open ocean, where incidentally much of the largest sea-level changes have happened. Referring to the satellite time-series is a much more comprehensive measurement of global sea level. Tide-gauges and satellite-data agree where they can be compared.
When I first read about the study I focused on the starting point, 1992. I then asked why they were not using data from tidal gauges. Tidal gauge data that goes back over 200 years shows us a 60 year cycle of up and down sea level. By using only 20 years when the tidal gauges were showing a rising sea level they of course end up with the results they did. It is the kind of “science” that con artists would use to convince the gullible.When dealing with cyclic events you always need to look at when the study starts and whether it includes at least one cycle. If it doesn’t, then the study is majorly suspect, unless it is noted that the study does not include a full cycle and was done in order to comply with grant requirments in which case it is again suspect.
Wow!! All we need is a new satellite!! The bid notice follows:
Notice to Bidders for NASAs GRASP
1. The work we want did is clearly showed on the attached plans and speserfacations. Our enganear, whose had plenty of college, spent one hell of a lot of time when drawed up these here plans and speserfacations. But nobody can think of everthing! Once your bid is in, that’s it, Brother! From then on, anything wanted by our enganear, or any of his friends, or anybody else (excep the contrakter) shall be cusidered as showed, speserfide, or emplide and shall be pervided by rhe contrakter without no expence to nobody, but hisself (meanin’ the contrakter).
2. If the work is did without no extry expence to the contrakter, then the work will be took down and did over again until the extry expence to the contrakter is satisfactory to our engangear.
3. Our engangear’s plans is right as drawed. If sumthin’ is drawed wrong, it shall be discuvared by the Contrakter, kerected and did right with no extry expence to us. It won’t cut no ice with us or our enganear if you point out any mistakes our enganear has drawed. If you do, it will be one hell of a long time before yu do any more work for use or him (meaning the engangear)!
4. The contrakter is not sposed to make fun of our enganear, his plans, or the kind of work we’re having did. If he do, it’s jest too bad for him (meanin’ the Contrakter).
5. Any Contrakter walkin’ around the job with a smile on his face is subject to review of his bid.
6. If the Contrakter don’t find all or our enganear’s mistakes before he bids on this job, or if the contrakter ain’t got enough sence to know that our enganear’s goin’ to think yp a bunch of new stuff that’s just too bad for him (meanin’ the contrakter)!
7. The Contrakter gotta use all good stuff on this job – none of this crap from Solyndra.
The laser altimetry is essentially flat since a) it was done on a campaign basis, not continuously and so it didn’t capture changes within years and b) the time-series is so short that the results depend on ice sheet “weather”. Shepherd et. al. nicely demonstrates the clear need for continuous long time-series to see what is really happening.
REPLY: “…to see what is really happening.” Agreed, they simply don’t know. This paper is just another guess based on noisy data, and having a stable baseline is key to that. There’s no getting around the need for a stable baseline – Anthony
Even IF the numbers are correct, where is the proof that any ice sheet loss is due to CO2? How does this match up with the fact that there has been no warming for 15 years? So, if even the ice sheets are shrinking there must be other exogenous variables involved, ie cloud patterns, storm systems, under sea volcanic activity, etc.
izen says: “Unless you know the magnitude of the error you cannot just discard data you dislike.”
Yet according to proponents of Global Warming one must accept conclusions derived from data with unknown magnitude of error. As in claim of 0.020** or 0.013** or 0.016** or 0.007** degree C rise in temperature per year based upon weather station data with an average error of +/- 1.86 degree C per daily reading.
**Pick your Global Warming Alarmist claim/prediction – which demonstrates the utter inaccuracies of Global Warming Faux-Climatologists, since they can’t even agree within 18% of each other.
According to JPL the TRF-related uncertainty is 0.45mm/year, see last slide here:
http://wattsupwiththat.com/2012/10/30/finally-jpl-intends-to-get-a-grasp-on-accurate-sea-level-and-ice-measurements/
REPLY: and if that were fully true, then they wouldn’t need to push for a new space platform and mission to correct the problem. Bottom line is we don’t know. All we have are estimates based on noisy data. If this were a skeptical paper, such things would be demanded, as it stands you give this paper a free pass, part of the problem with government funded group think of which you are a part. – Anthony
Liberal Skeptic says:
December 3, 2012 at 8:17 am
You failed to point out that the Northern hemisphere snow cover low record was for the month of June and the record is only 45 years long. Maybe Eurasia is having a drought? They make no statement about the rate of change of annual precipitation in the relevant area – I wonder if that’s reducing too?
Liberal Skeptic says: “All this tells me is that we still have no idea what is going on. So how can we possibly base any sort of policy on it?”
The scary part is not the possibility of Global Warming, but the world will enact inane policies based upon the recommendations / demands of Global Warming’s scientists (Faux climatologists), experts (self-proclaimed), and politicians (aka dictators).
“(Not) off topic:
Why is it that while Europe, from Britain to Siberia down to Spain and Portugal and Italy have been taken over by snowstorms and near record cold we do not hear anything form the MSM?”
Simple, high temperatures (the new normal) are global warming, low temperatures are just weather UNLESS they are really low, then it’s climate change. Got it?
I hope we’ve learned that if the satellites can’t be calibrated on the fly against a stable reference then launching them is a waste of money. Reminds me of the ACRIM vs PMOD debates.