Below is a GRACE satellite map. The Earth looks like a warty ball, with red bumps and blue pits that represent measured fluctuations in the planet’s gravity. Note Greenland in the red. We’ve covered GRACE before, suggesting it may not be a good tool to measure ice loss in Greenland. See this WUWT story.
The red spots represent measurements where Earth’s gravity is stronger. The blue ones are where it is measured to be weaker. The universal force of gravity itself does not vary, but the pits and bumps are a local indication that Earth’s mass distribution isn’t smooth and uniform. As seen on the image above, tectonic mountain building in South America produces red zones; elsewhere, tectonic movements produce thin, blue, ones.
Even more interesting is the fact that the map changes over time, Earth as we know is not static.
CO2 science reviews this new paper, which suggests that for sea level rise and ocean mass, the signal to noise ratio is high low and adjustments further complicate the issue. It also suggests some studies aren’t appropriately correcting for these issues. For example, GRACE measurements related to Greenland and West Antarctica (which we also criticized in WUWT here and here):
“…non-ocean signals, such as in the Indian Ocean due to the 2004 Sumatran-Andean earthquake, and near Greenland and West Antarctica due to land signal leakage, can also corrupt the ocean trend estimates.”
Ocean Mass Trends (and Sea Level Estimates) from GRACE Reference
Quinn, K.J. and Ponte, R.M. 2010. Uncertainty in ocean mass trends from GRACE. Geophysical Journal International 181: 762-768.
Background
The authors write that “ocean mass, together with steric sea level, are the key components of total observed sea level change,” and that “monthly observations from the Gravity Recovery and Climate Experiment (GRACE) can provide estimates of the ocean mass component of the sea level budget, but full use of the data requires a detailed understanding of its errors and biases.”
What was done
In an effort designed to provide some of that “detailed understanding” of GRACE’s “errors and biases,” Quinn and Ponte conducted what they describe as “a detailed analysis of processing and post-processing factors affecting GRACE estimates of ocean mass trends,” by “comparing results from different data centers and exploring a range of post-processing filtering and modeling parameters, including the effects of geocenter motion, PGR [postglacial rebound], and atmospheric pressure.”
What was learned
The two researchers report that the mean ocean mass trends they calculated “vary quite dramatically depending on which GRACE product is used, which adjustments are applied, and how the data are processed.” More specifically, they state that “the PGR adjustment ranges from 1 to 2 mm/year, the geocenter adjustment may have biases on the order of 0.2 mm/year, and the atmospheric mass correction may have errors of up to 0.1 mm/year,” while “differences between GRACE data centers are quite large, up to 1 mm/year, and differences due to variations in the processing may be up to 0.5 mm/year.”
What it means
In light of the fact that Quinn and Ponte indicate that “over the last century, the rate of sea level rise has been only 1.7 ± 0.5 mm/year, based on tide gauge reconstructions (Church and White, 2006),” it seems a bit strange that one would ever question that result on the basis of a GRACE-derived assessment, with its many and potentially very large “errors and biases.” In addition, as Ramillien et al. (2006) have noted, “the GRACE data time series is still very short,” and results obtained from it “must be considered as preliminary since we cannot exclude that apparent trends [derived from it] only reflect inter-annual fluctuations.” And as Quinn and Ponte also add, “non-ocean signals, such as in the Indian Ocean due to the 2004 Sumatran-Andean earthquake, and near Greenland and West Antarctica due to land signal leakage, can also corrupt the ocean trend estimates.”
Clearly, the GRACE approach to evaluating ocean mass and sea level trends still has a long way to go — and must develop a long history of data acquisition — before it can ever be considered a reliable means of providing assessments of ocean mass and sea level change that are accurate enough to detect an anthropogenic signal that could be confidently distinguished from natural variability.
References
Church, J.A. and White, N.J. 2006. A 20th-century acceleration in global sea-level rise. Geophysical Research Letters 33: 10.1029/2005GL024826.
Ramillien, G., Lombard, A., Cazenave, A., Ivins, E.R., Llubes, M., Remy, F. and Biancale, R. 2006. Interannual variations of the mass balance of the Antarctica and Greenland ice sheets from GRACE. Global and Planetary Change 53: 198-208.
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I have to agree with John Cook. This quote from your article jumped out as a bit misleading when I read it.
“It also suggests some studies aren’t appropriately correcting for these issues. For example, GRACE measurements related to Greenland and West Antarctica”
The paper CO2 science highlights only discusses GRACE sea level estimates. The quote you use from the paper suggests what is happening in Greenland and Antarctica is affecting this measurement not that the Greenland and Antarctic data is in someway inaccurate itself. That may be true or not but it’s not what this paper is describing.
pat says:
July 20, 2010 at 6:28 pm
O/T but pertinent:
20 July: The Atlantic: IPCC Chief Says Grassroots Must Lead on Climate Action….
But no international accord has come together, and climate legislation remains stalled in Congress. Maybe that’s why Pachauri is sounding the grassroots note: twisting the arms of national leaders just hasn’t worked.
_______________________________________________________
Pachauri is not talking about real grassroots, he is talking about the UN lead NGOs. A few years ago I traced another “grassroots” initiative straight back to the UN.
dp says:
July 20, 2010 at 6:49 pm
I get the feeling we’re going to see another “trick” to make the data look the way they want it to look.
_____________________________________________________________
We have already seen what a mess can be made with something as simple as a thermometer reading. This is vastly more complicated from what I have read here so far, so it is certainly open to “misinterpretation.” Like the temperature data, I think the error is going to be larger than is publicly acknowledge.
John Cook and skepticalscience.com are entirely correct.
Temperature has nothing to do with ice melting.
Obviously, only CO2 (and climate scientists) can make ice melt.
And there were no icebergs in 1912 when the Titanic sank because CO2 was only 300 ppm at the time and the CO2 forcing was only 0.4 watts/m2 and temperatures were 0.8C less than today.
Its not like 3.8 km high glaciers push out to the sea and eventually break off or anything (caused by gravity which is what this post is all about). Now if temperatures are -50C at the 3.8 km high peak and -10C where they break off as icebergs, CO2 will still cause the ice to melt.
skepticalscience is different than logical science.
Plate tectonics and continental drift were refuted for 70 years, because most scientists believed that the earth was rigid and fixed. The same mistake which some people are making to arrive at incorrect interpretations of GRACE data.
Anyone who has studied geology knows that it can vary considerably over even very short distances. Yet GRACE interpreters delude themselves into believing that the earth is steady and fixed over vast distances underneath the ice and oceans.
The Skeptical Front of Judea…a pox on those buggers from the Judean Popular Skeptics Front.
Zeke the Sneak says:
July 20, 2010 at 4:01 pm
“Gravity is a curvature of space-time that just looks like a force.”
Actually “gravity is due to radially oriented electrostatic dipoles inside the Earth’s protons, neutrons and electrons.” Therefore, “If the electric field within the Earth changes, the amount of this dipolar distortion will change and the force of its gravity will change.”
Hope that helps.
“Electric Gravity” and “Newton’s Electric Clockwork Solar System,” by Wal Thornhill
Since you seem to seriously considering this proposal I find it necessary to stress, for the people who are not scientifically oriented and are reading this blog that there is no iota of scientific proof in the statement you propose.
Therefore it should be treated as science fiction at best.
For science fiction I recommend the series of books by Terry Prachett on Diskworld, a delightful universe he has invented where gravity does amazing things.Fun for satire, but it would be impossible to be taken seriously.
“Gravity is a curvature of space-time that just looks like a force.” is what has been verified experimentally at the moment. The statement might change in the future, but it will change in the way Newtonian statements have changed with the emergence of general relativity, become incorporated in a more encompassing theory.
Dr A Burns
Is there any real need to be particularly worried about a 28 to 34 cm rise in Sea Level by 2100? Surely that is somethng that the human race can adapt to!
What we can take from the study if you are correct is that the mean 20th C rate of SL rise is not worse than was previously thought, that the acceleration is no worse than previously thought, and that the projection for the future it is probably in the lower portion of the IPCC estimate range.
Given that the global ocean does not appear to have gained much heat since about 2003 or so I suspect there will be a leveling off in the rate of SL rise. Not much to be truely alarmed about.
anna v says:
“Since you seem to seriously considering this proposal I find it necessary to stress, for the people who are not scientifically oriented and are reading this blog that there is no iota of scientific proof in the statement you propose.”
“In 1850, Faraday performed experiments trying to link gravity with electromagnetism that were unsuccessful. However, his conviction remained: “The long and constant persuasion that all the forces of nature are mutually dependent, having one common origin, or rather being different manifestations of one fundamental power, has often made me think on the possibility of establishing, by experiment, a connection between gravity and electricity …no terms could exaggerate the value of the relation they would establish.”[12]
Faraday’s estimate of the importance of such a connection still stands. Today, there are a number of scholars pursuing this obvious line of inquiry. After all, the electrical and gravitational forces share fundamental characteristics—they both diminish with the inverse square of the distance; they are both proportional to the product of the interacting masses or charges; and both forces act along the line between them.”
~Wal Thornhill
@ur momisugly Zeke the Sneak July 20, 2010 at 4:33 pm
“However, important questions concerning the density of the thermosphere and non-gravitational accelerations need to be addressed.”
They have accelerometers to adjust for external gravitational forces. Different external effects will cause different changes in acceleration (this is commonly used in process control to assess the origin of a signal). The work you refer to uses the data to calculate the neutral density. There is still improvement to be done but you don’t get anywhere unless you try.
@ur momisugly John Trigge July 20, 2010 at 4:15 pm
You ask about external influences and specifically about the moon. You can calculate the influence of the moon yourself using acceleration = Gm/r^2. The worst case scenario would be when the two satellites have the biggest difference in their distance from the moon. This would be when they are travelling away from the moon and at their furthest distance apart (270km). Taking into account the distance of the earth’s centre from the centre of the moon and their height above the earth one would be about 384.465 and the other about 384.736 million meters away from the moon. Taking into account the mass of the moon as 7.35×10^22 kg the difference in the acceleration due to the moon’s gravity over the distance of 270km is about 4.77 billionth of the acceleration due to the earths gravity. As the satellites are trying to measure to an accuracy of 1 millionth of the acceleration of the earths gravity the moon would create a maximum error of about 0.5% of the measured value. This error, even though it can just be ignored, is quite predictable however. For unpredictable errors there are accelerometers on board. The nature of the signal will then give an idea of its source. For example high frequency erratic acceleration will probably be caused by wind.
Did you actually read the paper that you pretended to criticize?
ftp://ftp.csr.utexas.edu/pub/ggfc/papers/ngeo694.pdf
They specifically consider Post Glacial Rebound in their analysis.
Please attempt to accurately describe the research that you pretend to judge.
Zeke the Sneak says:
July 20, 2010 at 10:25 pm
Zeke,
The unification of all “forces” is the holy grail of current theoretical research. The difference with the quote you give is that the effort is not ad hoc, with whatever interesting “model” flies through one’s brain, ignoring the data of centuries that have been organized in very useful theories, and the inevitable non sequiturs that come from that.
The current effort to unify all known forces and incorporate the old theories are the string theories, the only ones that allow for quantization of gravity. They look hopeful but it will be a long time before experimental tests will be able to uphold or reject them.
There are lovely models in science fiction, as I said the Diskworld of Terry Pratchett, where the world is a disk carried on the back of four elephants that have to lift a leg when the sun comes under it :). The whole is resting on the turtle which swims in the vacuum. In the same way one has to suspend knowledge of the current world to enjoy the science fiction world, one would have to suspend knowledge of the real data to entertain models like the one you quote.
anna v says: “There is no iota of scientific proof in the statement you propose. Therefore it should be treated as science fiction at best.”
Electric Gravity theory states in part that:
1. There are alternative explanations for the proofs offered for Einstein’s theory of gravity, ie the bending of light and Mercury’s orbit.
2. Insoluble mysteries for current understandings of gravity include: Astronomical Unit (AU) inflation, Lunar eccentricity, the ‘Pioneer Anomaly’, and oddball orbits.
“Surprise results are a signal that our understanding of the problem is faulty. We should be re-examining the assumptions that underpin our models rather than adding more complexity to patch over the cracks.” ~Wal Thornhill
It is true that Electric Gravity challenges Einstein’s theories. But it is now high time for that; if to do so is “science fiction” in some people’s minds, so be it.
Chris Noble
The fact that someone says they are making an attempt to do something does not mean they are doing it either correctly or in a meaningful fashion.
Why is it that the same people who nitpick about the most trivial details here, are willing to blindly accept AGW BS without the even the most simple questioning or doubt?
Because it is a faith based religion.
Chris Noble says:
July 20, 2010 at 10:35 pm
In the previous thread linked above, there was extensive discussion of the lack of taking into account tectonic changes and volcanic ones too. Ice rebounds are not even half of the story. If one looks at the warty globe above, one sees large variations due to tectonic motions all over the globe, where no ice was. The antarctic and the arctic are not immune to these motions, and subject only to ice rebound and pressure changes. There are too many variables with too few equations to be able to solve for ice thickness using the GRACE data.
If I was unclear, Electric Gravity does not attempt to find a holy grail. As I understand, it makes a strong and detailed case that mass is an electrically variable property of matter, and that gravity is happening at a subatomic level.
Zeke the Sneak says:
July 20, 2010 at 11:25 pm
It is true that Electric Gravity challenges Einstein’s theories. But it is now high time for that; if to do so is “science fiction” in some people’s minds, so be it.
What you and the people peddling their pet theories refuse to see is that the known world is influenced by four forces, not only by gravity and electromagnetism. ( btw the Kaluza Klein theory had unified those, I think before the war, but fails to take into account weak and stong forces as we have extensively measured and observed).
Many attracted by the glory of defeating Einstein go around like Don Quixote tilting at windmills.
Electromagnetism in the gauge theory formulation of Maxwell gave the input to unify all three forces, electromagnetism, weak and strong in what are called gauge theories that have been verified beautifully with the experiments at LEP, in CERN the past decades.
Theorists trying to include gravity in, and gravity is also a gauge theory, and unify all four forces had the problem that gravity’s infinities could not be compensated/calculated. This is due to the nature of gravity: no antigravity.
Until string theories.
In a nutshell, from string theories the standard particle model comes out naturally and at the same time gravity is included and quantized.
Simplified, each particle is a vibrational mode on a string ( the music of the spheres).
There is a long way to go until this string dream is verified, but at least there is no contradiction with existing data from the start.
The problem with ad hoc theories grabbing out of the bag electromagnetism and gravityin order to have the glory of defeating Einstein is that they cannot include/predict the beautiful data for the other two forces, weak and strong.
“What about the GPS measurements of crustal uplift that support GRACE measurements of the loss of ice mass? Nothing like two independent methods cross validating each other.”
Unfortunately there aren’t any GPS measurements where it counts, i. e. under the icecaps. Also note that crustal uplift and loss of ice can but need not be related. In Scandinavia for example uplift is still considerable (up 10 mm/year) more than 10,000 years after the ice melted. Since the ice in Antarctica and Greenland retreated from the continental shelf approximately at the same time uplift round the edges of the icecaps is only to be expected.
Quite amazing that in all the years since Newton we still do not have a solid understanding of the mechanism underpinning his simple gravity equation. Perhaps no surprise then that the GRACE results are less than solid.
One effect not taken into account by the various computer models used by GRACE is gravitomagnetism, and this could further skew the measurements. The NASA satellite, Gravity Probe B, is currently trying to confirm the existance/size of the gravitomagnetic effect, although it seems they could have been beaten to the punch.
“…in a lab in Austria, Martin Tajmar and his team have already succeeded in detecting a faint signal that seems to be due to this elusive component of gravity. A reason for celebration? Not quite. Puzzlingly, the force they seem to have generated is vastly more powerful than anyone else expected.”
New Scientist magazine, 11 November 2006 – “Gravity’s Secret”
http://www.newscientist.com/article/mg19225771.800-gravitys-secret.html?page=1
Chris Noble says:
“Did you actually read the paper that you pretended to criticize?
ftp://ftp.csr.utexas.edu/pub/ggfc/papers/ngeo694.pdf
They specifically consider Post Glacial Rebound in their analysis.
Please attempt to accurately describe the research that you pretend to judge.”
In that paper they used the IJ05 model for glacial rebound. The paper describing the model (http://journals.cambridge.org/action/displayFulltext?type=1&fid=355410&jid=ANS&volumeId=17&issueId=04&aid=355409)
contains this rather significant sentence:
“Our estimate of the error in ice load history is that a one sigma level error is roughly at 50 to 100% for any given
post-LGM time for ice differential thicknesses larger than about 500 m.”
Meaning that the Post Glacial Rebound is rather uncertain, to put things mildly.
Alex Buddery says:
July 20, 2010 at 10:30 pm
Thanks for the data and the explanation.
Now, as tides are caused by the gravity effect of the moon and some tides have a low/high variance of many 10’s of feet (from Wiki: The world’s biggest tidal differential occurs in the Bay of Fundy in Eastern Canada, where the sea level changes by up to 17 meters (55 feet) during the day.) what gravity variances are there due to such huge amounts of sea water moving around?
Does GRACE make allowances for high/low tides?
“Grace matches up well with all the other methods of estimation for ice losses.”
Well it would. Since you cannot use the raw data from GRACE directly, you need to feed it into a computer model to get any results at all. And since GRACE is used to measure ice loss, it would not surprise me at all to discover that the results from GRACE have been calibrated to match the estimate of ice loss from other means. Given that GRACE is not sufficiently accurate to detect known geological features on the surface of planet Earth such as the Mid-Atlantic ridge, it would be extraordinary if it could detect small changes in ice volume over short periods with sufficient accuracy to confirm the existing estimates of ice-loss.
I suspect that the models are merely gross examples of confirmational bias.
I, for one, find it extraordinary that anyone suggest the GRACE measures anything very useful at all. The measurements that GRACE produces (if you assume they have anything like the accuracy suggested) are monitoring the dents in spacetime caused by “gravity” – and are therefore subject to mass changes throughout the entire sphere. At the same time they are influenced by the Sun and the Moon which change the shape of the sphere itself by up to 0.55m at the equator whilst also shifting up to 17m of water across the surface. It would be extremely difficult to extract these effects with the required accuracy to leave you with a distriubtion of the stationary mass at the surface, let alone very small changes in that mass.
Agile Aspect says:
July 20, 2010 at 5:07 pm
Thank you for emphasising the difference between G and g. It’s really elementary physics, shame it’s not so well understood.
I have yet to see an estimate of the spatial resolution of this lettle pair of coupled toys. There is not really a fixed resolution, just a complex reduction of g with distance. Has ontone seen figures like “90% of the instantaneous measured signal comes from an earth area of 100,000 sq km” or whatever?
The ditance measurement between the satellites is so small that puffs of cosmic wind would upset it, or a hit from a micrometeorite. Does anyone know if a correction is applied for turbulence, small though it might be?
Zeke the sneak,
“It is true that Electric Gravity challenges Einstein’s theories. But it is now high time for that; if to do so is “science fiction” in some people’s minds, so be it.”
Challenge by all means, with all scientific rigor. But earlier in your post you asserted the electric dipole theory of gravity as if it was a fact, when it is clearly only a conjecture.