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.
===========================================================
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.
=============================================================
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”
=============================================================
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:
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
“J Martin says: CostCo said : on December 3, 2012 at 9:20 am
Heck, in some places and at some times the ice sheet surface is dropping 10+ meters per year!
And this despite temperatures in the Antarctic having fallen consistently for years. Presumably you can find a link for that apparent contradiction.”
Sea-water has warmed up in some areas around Antarctic and melted the ice-shelves and ice-streams from below.
“ntesdorf says: This paper was never about science, it was a propaganda piece timed to be released to bolster flagging spirits at Doha Round. As usual the usual Media suspects have responded as required and spread the misinformation before the public.”
Yeah, right, a landmark Science-paper by most of the best research teams in the world is not “science”. Nice try.
Rob Dawg says: CostCo says; “…the magnitude of the uncertainty is known,…”
Excellent. What is it?”
As already indicated a few times, the error has been circled on this slide from JPL:
http://wattsupwiththat.files.wordpress.com/2012/10/grasp_impact.png?w=640&h=380
P. Solar says:
This plot is based on the tide gauge record, from Jevrejeva 2008
“Recent global sea level acceleration startedover 200 years ago?”
http://i40.tinypic.com/nx3q1.png
———————–
Why would anyone prefer satellite data over tide gauge data ?
Sea level changes are so tiny, that any changes on board, equipment drifts, heat sources, orbit changes, satellite rotation, atmospheric pressure, atmospheric consistency, atmospheric extent, solar variation etc will cause not only noise but also bias. So many known unknowns and unknown unknowns, proven to exist by the never ending stream of new sorts of data adjustment..
Tide gauge data is still noisy, but the only bias may come from land going up or down, which is 1) adjusted for and b) rest error should cancel over all coastlines.
Does that data match this data:
http://motls.blogspot.com/2012/12/sea-level-rise-is-most-reliable-way-to.html ??
What acceleration?
P. Solar says:
December 3, 2012 at 1:18 pm
Thanks for the plot!
Coarse, goes only 8 years beyond the satellite start of 1992, we’re still missing another 11.
Not sure that the resolution will enable me to layer it on with any meaning. The change/yr seemed to be going down. The last 11 years would tell the tale.
[“Of course” instead? Mod]
This looks like a more balanced discussion of the Greenland Ice Loss Study. http://www.princeton.edu/main/news/archive/S35/40/38C46/index.xml?section=topstories
The paper in Science…the abstract stated…
“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.”
As you will note the errors are quite large…so the net ice loss for the planet ranges from -88 Gt/yr to -354 Gt/yr and global sea level rise ranges from 0.39mm to 0.79mm per year. This is a very small amount. In other words over a 50 YEAR PERIOD we can expect the sea level (assuming the melt rate stays steady) to rise somewhere between 19.5mm to 39.5mm. This is roughly somewhere between 0.76 inches and 1.55 inches…!!!
Antarctica currently contains roughly 30 million cubic kms of ice. Remember that 1 cubic km of ice weighs about 1 gigatonne, so Antarctica contains 30 million gigatonnes of ice and so it appears from this publication that Antarctica is losing roughly 71 gigatonnes per year.
Also this estimate has large error estimates, if we put these errors in then the following applies… East Antarctica ranges between +57 to -29 Gt/yr and West Antarctica ranges between -39 and -91 Gt/yr and the peninsula ranges between -6 and -34 Gt/yr….so if we take the positive gain in East Antarctica (+57) and add it to the lower losses elsewhere in Antarctica we could possibly have a net gain…this is probably unlikely. These figures IMHO are no cause for alarm.
Anyone want to download 2149 tide gauge records (some with data up to Oct 2012) and then collate all that data into a trend of sea level rise over time:
http://www.psmsl.org/data/obtaining/rlr.monthly.data/
What is interesting is the [shear] effort going into collecting this data by hundreds of organizations around the world and then making it virtually/completely impossible to be able to calculate a trend from it.
One would then have to compare these individual records to the local land uplift/subsidence records from GPS receivers here in order to be accurate:
http://www.sonel.org/IMG/txt/ulr5_vertical_velocities_table.txt
Station identifiers here:
http://www.sonel.org/spip.php?page=cgps
And then one could actually calculate the level of sea level rise over time without having to resort to a global warming-based isostatic model.
But this is months of work. Why is this made so difficult when they have all the data.
Billy Liar says:
December 3, 2012 at 2:13 pm
Can somebody tell me how these satellite altimeters compensate for the inverse barometer effect where there are no measurements of the surface pressure?
In order to get accurate sea levels you have to have accurate simultaneous atmospheric pressure measurements.
From the JASON 2 data products handbook I linked above
5.10.1. Inverted Barometer Correction
As atmospheric pressure increases and decreases, the sea surface tends to respond hydrostatically, falling or rising respectively. Generally, a 1-mbar increase in atmospheric pressure depresses the sea surface by about 1 cm. This effect is referred to as the inverse barometer (IB) effect.
The instantaneous IB effect on sea surface height in millimeters (see parameter inv_bar_corr) is computed from the surface atmospheric pressure, Patm in mbar:
inv_bar_corr = -9.948 (P – P) ∗ atm
where P is the time varying mean of the global surface atmospheric pressure over the oceans.
The scale factor 9.948 is based on the empirical value [Wunsch, 1972] of the IB response at mid latitudes. Some researchers use other values. Note that the surface atmospheric pressure is also proportional to the dry tropospheric correction, and so the parameter inv_bar_corr approximately changes by 4 to 5 mm as model_dry_tropo_corr changes by 1 mm (assuming a constant mean global surface pressure). The uncertainty of the ECMWF atmospheric pressure products is somewhat dependent on location. Typical errors vary from 1 mbar in the northern Atlantic Ocean to a few mbars in the southern Pacific Ocean. A 1-mbar error in pressure translates into a 10 mm error in the computation of the IB effect.
Note that the time varying mean global pressure over the oceans, P, during the first eight years of the T/P mission had a mean value of approximately 1010.9 mbar, with an annual variation around this mean of approximately 0.6 mbar. However, the T/P data products provided a static inverse barometer correction referenced to a constant mean pressure of 1013.3 mbar.
IB(T/P) = -9.948 (P -1013.3) ∗ atm
Sea surface heights that are generated after applying an inverse barometer correction referenced to a mean pressure of 1013.3 mbar are therefore approximately -9.948*(1010.9-1013.3) = 23.9 mm lower than those that are generated after applying an inverse barometer correction referenced to a time varying global mean pressure, and the difference between the two sea surface heights has an annual variation of approximately 9.948*0.6 = 6 mm.
Reminds me of the election polling by Nate Silver’s 538 blog? When you pool the data you tend to get more accurate results. I think the righties are going to like this study about as much as they liked Nate’s prediction. Math can be a bitch. JP
Thanks, Anthony, I’m quoting you and linking to this article.
Jet Propulsion Laboratory (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.
Liberal Skeptic says:
December 3, 2012 at 8:17 am
First post…..
______________________________________
I think this is the more important piece of information since it is when snow cover starts in the fall in the Northern Hemisphere. And that snow cover is INCREASING graph
It seems Ma GAIA didn’t get the CAGW message or maybe she is just thumbing her nose at Doha
December 2, 2012: Cold front to bring blizzard to NE China
December 02, 2012 Russia Scrambles To Cope With Monster Snowfall
02 December 2012 Snow Continues As Mercury Plunges: Forecasters are warning of more snow in parts of Britain after temperatures plunged as low as -6C overnight.
01 december Snowstorm causes major problems on E4: After intense snowfall – with a meter of snow in many parts of Sweden – sections of the E4 motorway were blocked on Saturday afternoon
1 Dec 12 Record lows as winter freeze grips Sweden
Anomalous winter disasters paralyze Moscow: Moscow was literally paralyzed at night of November 30. The city and the region experienced two natural disasters in one night: a super heavy snowfall and an ice storm.
Blizzard in Estonia: If the week’s previous weather was a snowstorm, this one was a blizzard,” …A fresh snowstorm arriving on Thursday evening from the southeast buried much of the country – with some places gaining up to 27 centimeters of fresh snow
FINLAND: 30,000 blacked out by snowstorm: Tens of thousands of households were without electricity on Friday as a result of a storm that dumped heavy snow across southern Finland
Winter’s first cold snap hits Fairbanks: This month is going to be in the top few coldest Novembers of record,” ….That would put it just ahead of November 2011, which ranked as the sixth-coldest November on record
Severe Snow Storm Hits Northern Japan: Northern Japan has been blasted with an intense snow storm today as northwesterly winds pelted the region causing widespread havoc to residents in Hokkaido and Northern Honshu. Winds gust up to 152kph in Japans northernmost prefecture knocked out power for at least 40,000 residents
27 November 2012 Britain faces coldest winter for 100 years as Big Freeze follows floods with wind so strong it blows water upwards
Snowfall paralyzes life in China: China has experienced the biggest snowfall in 52 years …Temperatures were brought down by as much as 14 degrees below zero in some areas
CHINA: Worst snow in 50 years damages 400 greenhouses…in Hegang, China’s Northeast Heilongjiang province on Nov 15, 2012.
Snowfall freezes Kashmir valley: first snowfall of the season has yet to arrive in Srinagar, but the temperature has reached below zero degree for the first time this season…continuous snowfall over the last two days…temperatures have dropped to minus six degree in Kargil and Dras.
Pakistan Heavy snowfall: Nathia Gali including its surroundings 4 to 5 feet snow fall by …Snowfall season has been continuing since last 2 days …. Snow fall also is continuing in upper areas of Azad Kashmir.
Smoky Mountains: A record amount of snow fell across the higher elevations in October
October 28, 2012, Low Temperature Record Set In Central Texas
As Steven Goddard shows below
http://stevengoddard.wordpress.com/2012/12/03/more-sea-ice-than-on-this-date-in-1979/
” On this date in 1979, there was 20.15 million km^2 of sea ice on Earth. Today there is 20.20 million km^2.”
Where’s the ice loss?
CostCo says: “Subsidence of bedrock or what?”
You really are in over your head if you don’t understand how that could give false GW Alarmist readings.
CostCo says: “… the surface velocity of the ice is known, which can be used to infer what is going on.”
Infer as in take a Educated Wild Arse Guess.
As for SAR/InSAR velocity being known, go read up on what can effect SAR accuracy before you make such statements.
Darren Potter says: @ur momisugly December 3, 2012 at 9:07 am
….The scary part is not the possibility of Global Warming, but the world will enact inane policies based upon the recommendations….
_____________________________
The really scary part is the politicians will give the great unwashed very expensive/scarce energy and food and THEN we head into another Little Ice Age or even worse the big plunge.
We know diddly squat about what really drives climate because the money interests have been backing CO2 to the exclusion of anything and everything else. This means the world governments can easily get caught flatfooted if TSI is NOT the solar forcing that has the major impact on climate but something else like the solar magnet field or UV does as certain papers indicate. The cycles are there. Too many papers from different parts of the world using different methods support solar cycle, temperature/precipitation cycles for there to be any doubt.
Ag interests have already convinced the USA NOT to have a strategic grain reserve but to rely on BUYING grain if needed. The USA produces 25% of the world’s grain BTW.
Here is Poptech’s list of just the 1500 year cycle. The solar list is much longer. (Papers are linked at his site)
1,500-Year Climate Cycle
A Pervasive Millennial-Scale Cycle in North Atlantic Holocene and Glacial Climates
(Science, Volume 278, Number 5341, pp. 1257-1266, November 1997)
– Gerard Bond et al.
Late Holocene approximately 1500 yr climatic periodicities and their implications
(Geology, Volume 26, Number 5, pp. 471-473, May 1998)
– Ian D. Campbell et al.
The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change
(Proceedings of the National Academy of Sciences, Volume 97, Number 8, pp. 3814-3819, April 2000)
– Charles D. Keeling et al.
Timing of Millennial-Scale Climate Change in Antarctica and Greenland During the Last Glacial Period
(Science, Volume 291, Issue 5501, pp. 109-112, January 2001)
– Thomas Blunier et al.
Widespread evidence of 1500 yr climate variability in North America during the past 14 000 yr
(Geology, Volume 30, Issue 5, pp. 455-458, May 2002)
– André E. Viau et al.
Decadal to millennial cyclicity in varves and turbidites from the Arabian Sea: hypothesis of tidal origin
(Global and Planetary Change, Volume 34, Issues 3-4, pp. 313-325, November 2002)
– W. H. Bergera et al.
Timing of abrupt climate change: A precise clock
(Geophysical Research Letters, Volume 30, Number 10, pp. 17-1, May 2003)
– Stefan Rahmstorf
Possible solar origin of the 1,470-year glacial climate cycle demonstrated in a coupled model
(Nature, Volume 438, Number 7065, pp. 208-211, November 2005)
– Holger Braun et al.
The origin of the 1500-year climate cycles in Holocene North-Atlantic records (PDF)
(Climate of the Past, Volume 3, Issue 2, pp.679-692, 2007)
– M. Debret et al.
Global Warming Every 1,500 Years: Implications for an Engineering Vision (PDF)
(Leadership and Management in Engineering, Volume 8, Number 3, pp. 153-159, July 2008)
– Dennis T. Avery
Holocene temperature records show millennial-scale periodicity (PDF)
(Canadian Journal of Earth Sciences, Volume 47, Number 10, pp. 1327-1336, October 2010)
– Craig Loehle, S. F. Singer
CostCo says: As already indicated a few times, the error has been circled on this slide from JPL:
And as already indicated several times, “The uncertainty is quite clear in Table 1, which has error ranges larger than the data in some cases”.
As you can see, we too can play the repeat game.
richard says:
December 3, 2012 at 10:21 am
All I know is that crocodiles swam in the arctic region many, many, many, many, moons ago, the Russians were using the NE Arctic passage commercially from the 1930′s onwards and underneath from Greenland to Siberia is a long line of Volcanoes that erupted a decade or so ago.
___________________________________
And do not forget the undersea volcanoes in Antarctica.
I can understand your beef with the altimetry and interferometry data in the paper but I don’t see how it affects the gravimetry data.
First, even with your argument, I think it’s safe to say that the data for Greenland is safe. The altimetry and interferometry data shows an average loss of 7 cm for the entire subcontinent using a machine that measures ocean surface in mm’s. So whether it’s 6 cm or 7 cm, a lot of ice is missing, and this is consistent with other recent reports.
But the Antarctic data is thinner, averaging about 1/2 cm loss over the entire continent.
Here’s where the gravimetry data really buttresses the paper. I don’t know how the gravimetry units work, but the satellite measures local changes in gravitational acceleration, and this correlates with local mass. The simple way to look at the gravimetry data is 1) whether it’s going positive or negative, and 2) its magnitude. The correlation of the gravimetry data with the altimetry and interferometry data was beautiful addition to the paper, and is hard to argue with. For example, in the West Antarctic data, the altimetry and interferometry data shows a loss, and so does the gravimetry data.
The other parts of the Antarctic data that are convincing are the local differences. That is, in places where there are other reports showing that the area is warming, the ice ablation is higher (West Antarctic) and where it is cooling, lower (East Antarctic).
CostCo says: ” a landmark Science-paper by most of the best research teams in the world is not “science”.
Well since it is a “landmark Science-paper” by “most of the best” research teams in “the world” then it must be absolute disputable fact. Like there were nine planets, huh? /sarc
mpainter says: @ur momisugly December 3, 2012 at 12:00 pm
But you need to support your claim that the largest sea level changes occur in open ocean. How can that be?
____________________________________
Trade Winds.
http://www.youtube.com/watch?v=lmjaNO5DD_Q
Gail Combs says: “… THEN we head into another Little Ice Age or even worse the big plunge. ” “We know diddly squat about what really drives climate because the money interests have been backing CO2 to the exclusion of anything and everything else. ”
Exactly, since we don’t understand what caused past climate changes, thanks to AGW group think and self-serving interests, and given proponents of AGW having been 0 for 30 on their dire warming predictions, it is remotely possible that an increase in CO2 leads to Global Cooling. Or more likely CO2 has no effect and we have been wasting resources looking at the wrong thing.
I am not surprised the Greenland ice sheet has decreased lately, because a few years ago, before finding Anthony’s informative blog, I stumbled across a website that detailed the temperature of the Gulf Stream (which flows to Greenland), and it showed that its SST has been increasing. So, that warmer water plus the warmer air blowing over it would naturally cause the Greenland ice sheet to recede, consequently, eliminating a need to invoke an AGW scenario when there exists a plausible physical effect.
I did not maintain “notes” back then, so I cannot provide a link. Shouldn’t there also be a SST site for the warm waters flowing north along the eastern Asian continent?
Most folks that went to junior high 45-50 years ago know that the earth is essentially an elastic ball of liquid and that the weight of all that ice in the Antarctic has severely depressed the underlying crust. Just like a balloon full of water, the effect of subsidence with more ice or some other tidal effect causing additional subsidence will cause an apparent sea level with no melting
Involved.
I am wondering if one of the fine minds in this free for all knows the answer to the following? GPS satellites have their clocks offset prior to launch due to the relativistic effects of gravity. Is there additional compensation applied due to the effects of variations in the earth’s gravity, the position of the moon, sun, Jupiter, etc? That would be a lot of look up tables.
It DOES change. I have a close friend who is a civil engineer. These reference points constantly drift on all three axes. The movement is checked and a new “epoch” is created. Surveys done in one “epoch” must have the drift of the benchmark accounted for if they are being applied to the current “epoch”. If you have a datum from 1973, it may not be in the same location in 2012. It might have moved a foot or more depending on where it is and how long ago the survey was done.