There’s some blogospheric carping about his statement in the JPL press release below regarding Greenland’s ice sheets:“… their cumulative loss could raise sea level by 15 centimeters (5.9 inches) by 2050.”
Well sure, it could be, but as this recent surprise study from GISS’s neighbors at Columbia illustrates, even though we’ve had the GRACE (Gravity Recovery And Climate Experiment) satellite looking at Antarctica, and concluding there’s been ice mass loss there, we have this new study that shows ice being added from underneath due to meltwater refreeze, concluding the models to be wrong.
It goes to demonstrate that we really don’t understand ice sheet mechanics well enough yet to make accurate forecasts, though some people think we can.
Add to that, GRACE has it’s own set of problems. And at least one model conlcusion has been revised post facto because the melt data is overestimated:
The melting of the ice sheets of Greenland and West Antarctica is about twice as slow as previously thought. The study, conducted by TU Delft, SRON and the Jet Propulsion Laboratory. The scientists published their findings in the September issue of Nature Geoscience.
We have concluded that the Greenland and West Antarctica ice caps are melting at approximately half the speed originally predicted.’ The average rise in sea levels as a result of the melting ice caps is also lower.
In fact, errors from GRACE may be quite large. So take this new release from JPL and the squawking about the forecasted sea level rise with a grain of salt. But more importantly, look at what the actual sea-level data is saying, and as Willis Eschenbach points out, natures seems to be Putting the Brakes on Acceleration.
From JPL: NASA Finds Polar Ice Adding More to Rising Seas
Store Glacier, West Greenland. A new NASA funded study finds that the Greenland and Antarctic ice sheets are losing mass at an accelerating pace, three times faster than that of mountain glaciers and ice caps. Image credit: Eric Rignot, NASA JPL
PASADENA, Calif. — The Greenland and Antarctic ice sheets are losing mass at an accelerating pace, according to a new NASA-funded satellite study. The findings of the study — the longest to date of changes in polar ice sheet mass — suggest these ice sheets are overtaking ice loss from Earth’s mountain glaciers and ice caps to become the dominant contributor to global sea level rise, much sooner than model forecasts have predicted.
The nearly 20-year study reveals that in 2006, a year in which comparable results for mass loss in mountain glaciers and ice caps are available from a separate study conducted using other methods, the Greenland and Antarctic ice sheets lost a combined mass of 475 gigatonnes a year on average. That’s enough to raise global sea level by an average of 1.3 millimeters (.05 inches) a year. (A gigatonne is one billion metric tons, or more than 2.2 trillion pounds.)
The pace at which the polar ice sheets are losing mass was found to be accelerating rapidly. Each year over the course of the study, the two ice sheets lost a combined average of 36.3 gigatonnes more than they did the year before. In comparison, the 2006 study of mountain glaciers and ice caps estimated their loss at 402 gigatonnes a year on average, with a year-over-year acceleration rate three times smaller than that of the ice sheets.
“That ice sheets will dominate future sea level rise is not surprising — they hold a lot more ice mass than mountain glaciers,” said lead author Eric Rignot, jointly of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and the University of California, Irvine. “What is surprising is this increased contribution by the ice sheets is already happening. If present trends continue, sea level is likely to be significantly higher than levels projected by the United Nations Intergovernmental Panel on Climate Change in 2007. Our study helps reduce uncertainties in near-term projections of sea level rise.”
Rignot’s team combined nearly two decades (1992-2009) of monthly satellite measurements with advanced regional atmospheric climate model data to examine changes in ice sheet mass and trends in acceleration of ice loss.
The study compared two independent measurement techniques. The first characterized the difference between two sets of data: interferometric synthetic aperture radar data from European, Canadian and Japanese satellites and radio echo soundings, which were used to measure ice exiting the ice sheets; and regional atmospheric climate model data from Utrecht University, The Netherlands, used to quantify ice being added to the ice sheets. The other technique used eight years of data from the NASA/German Aerospace Center’s Gravity Recovery and Climate Experiment (Grace) satellites, which track minute changes in Earth’s gravity field due to changes in Earth’s mass distribution, including ice movement.
The team reconciled the differences between techniques and found them to be in agreement, both for total amount and rate of mass loss, over their data sets’ eight-year overlapping period. This validated the data sets, establishing a consistent record of ice mass changes since 1992.
The team found that for each year over the 18-year study, the Greenland ice sheet lost mass faster than it did the year before, by an average of 21.9 gigatonnes a year. In Antarctica, the year-over-year speedup in ice mass lost averaged 14.5 gigatonnes.
“These are two totally independent techniques, so it is a major achievement that the results agree so well,” said co-author Isabella Velicogna, also jointly with JPL and UC Irvine. “It demonstrates the tremendous progress that’s being made in estimating how much ice the ice sheets are gaining and losing, and in analyzing Grace’s time-variable gravity data.”
The authors conclude that, if current ice sheet melting rates continue for the next four decades, their cumulative loss could raise sea level by 15 centimeters (5.9 inches) by 2050. When this is added to the predicted sea level contribution of 8 centimeters (3.1 inches) from glacial ice caps and 9 centimeters (3.5 inches) from ocean thermal expansion, total sea level rise could reach 32 centimeters (12.6 inches). While this provides one indication of the potential contribution ice sheets could make to sea level in the coming century, the authors caution that considerable uncertainties remain in estimating future ice loss acceleration.
Study results are published this month in Geophysical Research Letters. Other participating institutions include the Institute for Marine and Atmospheric Research, Utrecht University, The Netherlands; and the National Center for Atmospheric Research, Boulder, Colo.
JPL developed Grace and manages the mission for NASA. The University of Texas Center for Space Research in Austin has overall mission responsibility. GeoForschungsZentrum Potsdam (GFZ), Potsdam, Germany, is responsible for German mission elements.
More on Grace is online at http://www.csr.utexas.edu/grace/ and http://grace.jpl.nasa.gov/ .
JPL is managed for NASA by the California Institute of Technology in Pasadena.
===========================================================
Here’s the paper abstract at GRL:
GEOPHYSICAL RESEARCH LETTERS, VOL. 38, L05503, 5 PP., 2011
doi:10.1029/2011GL046583
Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise
E. Rignot
Earth System Science, University of California, Irvine, California, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
I. Velicogna
Earth System Science, University of California, Irvine, California, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
M. R. van den Broeke
Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, Netherlands
A. Monaghan
National Center for Atmospheric Research, Boulder, Colorado, USA
J. Lenaerts
Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, Netherlands
Ice sheet mass balance estimates have improved substantially in recent years using a variety of techniques, over different time periods, and at various levels of spatial detail. Considerable disparity remains between these estimates due to the inherent uncertainties of each method, the lack of detailed comparison between independent estimates, and the effect of temporal modulations in ice sheet surface mass balance. Here, we present a consistent record of mass balance for the Greenland and Antarctic ice sheets over the past two decades, validated by the comparison of two independent techniques over the last 8 years: one differencing perimeter loss from net accumulation, and one using a dense time series of time-variable gravity. We find excellent agreement between the two techniques for absolute mass loss and acceleration of mass loss. In 2006, the Greenland and Antarctic ice sheets experienced a combined mass loss of 475 ± 158 Gt/yr, equivalent to 1.3 ± 0.4 mm/yr sea level rise. Notably, the acceleration in ice sheet loss over the last 18 years was 21.9 ± 1 Gt/yr2 for Greenland and 14.5 ± 2 Gt/yr2 for Antarctica, for a combined total of 36.3 ± 2 Gt/yr2. This acceleration is 3 times larger than for mountain glaciers and ice caps (12 ± 6 Gt/yr2). If this trend continues, ice sheets will be the dominant contributor to sea level rise in the 21st century.
Received 4 January 2011; accepted 2 February 2011; published 4 March 2011.
Citation: Rignot, E., I. Velicogna, M. R. van den Broeke, A. Monaghan, and J. Lenaerts (2011), Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise, Geophys. Res. Lett., 38, L05503, doi:10.1029/2011GL046583.
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“Validation of GOCE and GOCE/GRACE Data Products, Prelaunch support …”? http://earth.esa.int/goce04/first_igw/papers/Shum_etal.pdf
Alleagra says:
March 10, 2011 at 10:37 am
Oh I dearly love a pedant: especially when it comes to punctuation.
You are of course entirely correct; it’s is an abbreviation of It is; its the objective version of his, hers or indeed ours or theirs since its can be both singular or plural according to sense. Thous is an archaic form even, I believe, in dialect.
Kindest Regards
This is more of a post than a comment, but what is written goes to the heart of these studies: that models haven’t been thought through to how they would be expressed in the real world, and so fail the evidence test, not just the falsifiability test. It comes down to this:
Houston, we have a reconciliation problem, Houston. We are missing some major new rivers.
Consider the math in the above post about icecap mass loss and sea-level rise:
1) Greenland and Antarctica: 475 gigatonnes/year, or 1.3 +/- 0.4mm /yr, increasing 36.2 gigatonnes/yr or 0.10 +/-.0055 mm/yr increase/yr
2) Icecaps and Mtn Glaciers: 402 gigatonnes/yr, or 1.10+/- 0.5(?? harder to measure losses?) mm/yr, increase 1/3X that of Greenland & Antarctic, or 0.033 +/-0.016 mm/yr
3) Thermal expansion: 90mm over 40 yrs, or 2.25 mm/yr average
[4) Additional subsurface discharge: modeled but not measurable with the huge, freshwater discharge planet wide of 1103555 mm/yr. So let’s ignore this.]
Taken together, the total contribution comes to 4.65 +/-0.9(?) mm/yr, currently, of which 45% is thermal expansion. This glacial ice melt is increasing its contribution at 0.13 mm/yr. In three years, according to the above report, we will have a sea-level rise of 5.04 mm/yr. Let’s consider that these numbers are correct and see what it means in our world as we see it, not imagine it.
It is hard to get a grip on ice melt volumes and what they must be like. For comparison purposes, let’s consider that the Mississippi River discharges a volume of 12.74Em2/sec averaged over the year. If this volume did not evaporate, the oceans would rise 1.2 mm/yr by sheer volume alone. If the water were at 0C and warmed up to the oceanic average, the Mississippi would account for 1.74 mm/yr in the planetary global sea-level rise. Although it has been hard to determine what the historic sea-level rise has been, a 21 High Quality Tidal Station study found the 100-year average prior to 1980 was 1.85 mm/yr. By that number, the Mississippi River by itself without evaporation and with heating up, could have accounted for almost all of the sea-level rise from 1880 to 1980.
Today, though, according to the above studies, the sea-level rise is 4.65 mm/yr, or 2.5 times the historical average. By 2015 it is to be 2.7X the historical average. This means that since 1980 the equivalent of an additional 1.6 Mississippi Rivers (4.65-1.85/1.74) of new water is entering the oceans and been warming up each year. By 2015, it will be an additional 1.8 Mississippi Rivers, or the equivalent of another Mississippi River plus the Ganges River relative to what was causing the seas to rise between 1880 and 1980.
In fact, if what these studies purport is true, the “operating” day rates must be greater than that. Recall that floating ice sheets do not add to sea level rise, so we can’t consider additional melting of floating ice. We can also discount that there is more floating ice than before, as they would cause the area of ice shelves next to the landmasses of Greenland and Antarctica to be greater now than before. Which they aren’t. We can also delete from consideration that glaciers are flowing into the sea and calving ‘bergs more now than in 1980 as the IPCC, the WWF et al. say that the glacial tongues are retreating up valleys and exposing new rock, not advancing and spawning a horror-show of icebergs. Moreover, if we think a solid-to-vapour sublimation and subsequent precipitation can get ice into the oceans without a visible liquid step we are stymied by the lack of increased river flow – a fact, the IPCC/ WWF proffer to warn us about a future inadequacy of freshwater. No: the only way we can get all of this proposed additional Mississippi multiple of water into the oceans is by melting the land-bound ice and having it flow as a liquid. We have to find 1.6 new Mississppiis today.
Actually, the problem is worse. As Greenland and the Antarctic melt only during about 4 months of every year, and not during the same time, whatever melt we have to produce during the year has to occur during an 8-month, not a 12-month period. If we have a global average of 1.6 new Mississippi discharges since 1980, then the actual discharge rate on an operating day basis has to be 2.4 Mississippis. And not 1.2 Mississippis each at opposite ends of the world. No: as Greenland is frozen when the Antarctic is melting, and vise versa, from August to September, there are 2.4 Mississippis worth of new meltwater coming off just Greenland, and then from November through February another 2.4 Mississippis worth of melting just from the Antarctic. And – taking the studies conclusions seriously, by January 2015, this increases to 2.7 new Mississippi Rivers (relative to 1980) draining Greenland and Antarctica on a rotating basis.
So where are they? We should already see them. The melt cannot be dispersed into a million rivers and impossible to recognize; the drainage of both icesheets isn’t like that.
The math is very simple. The mechanism is straightforward. The models are easy to understand. But where is the evidence? Where are the new Mississippis?
[BTW: aren’t these numbers out of sync with the new satellite data Hansen said was around 3.4 mm/yr (itself questionable)? But that is a different topic, though still a problem]
University of Colorado TOPEX and JASON data indicate a (60-day smoothed) 3mm per year mean sea level rise, with the trend since 2002 displaying a slight flattening:
http://sealevel.colorado.edu/current/sl_ib_ns_global.pdf
This trends is inconsistent with “accelerated” continental ice loss from Greenland and Antarctica, noting that steric expansion in the 1994-2000 time component of the Delta MSL trend accounts for part of this increase. It is of interest to speculate that the flattening of the Delta MSL-Time curve since 2000 may well be in accord with the absence of steric expansion resulting from global mean surface tenperatures displaying an absence of a warming trend.
R. Gates says:
March 10, 2011 at 11:37 am
Have you suddenly become 100% warmist?
Thanks R. Gates for the link, a very interesting JofC paper.
http://www.physorg.com/news/2011-03-earth-core-climate-insights.html
Another temperature proxy in need of “the trick” to hide the decline. The authors questioned everything for the breakdown in correlation except the GISS data.
Billy Liar,
Gates has always been 100% warmist. It’s in his nature.☺
Billy Liar says:
March 10, 2011 at 4:05 pm
R. Gates says:
March 10, 2011 at 11:37 am
Have you suddenly become 100% warmist?
______
I’ve never been 100% warmist, if by warmist you mean 100% convinced that AGW is happening.
Here’s where I stand, and what will change it one way or another:
I’m 75% convince that AGW is happening and is caused directly or indirectly by the build-up on anthropogenic GH gases– primarily CO2. I am current 25% “skeptic” in that I constantly look at other possible explanations for 20th century warming. Those other explanation include:
1) Unknown solar effects
2) Unknown ocean cycles
3) Unknown astronomical effects
Admittedly, I don’t put much real belief that there will be found some natural explanation other than AGW for the 20th century warming and related effects (such as sea ice decline, Greenland & Antarctica ice mass loss) but I try to be enough of a skeptic to actually put a few hours in each week of honest reading and research about the potential alternate explanations.
What events could cause me to become more of a skeptic?
1) A gradual turn-around in year-to-year arctic sea ice loss (ala what Joe Bastardi is expecting)
2) A 10 year period which does not show a warming trend decade over decade (i.e. if 2010-2019 is not warmer than 2000-2009 etc.)
3) A period of cold summer in which we see the majority of glaciers begin to grow, and even some areas of N. Cananda where the snowcover does not melt in the summer and new glaciers begin to form.
As it stands, I obviously doubt any of these happening, and in fact look for continued glacier, ice cap, and sea ice decline, and the decade to decade temps continuing to climb, and at some point (perhaps by 2020 at the latest) I expect to be 95%+ convinced in AGW, though hope to always reserve a bit of skepticism just because I never want to close my mind off from the chance of some new discovery.
wel says:
March 10, 2011 at 4:25 pm
Thanks R. Gates for the link, a very interesting JofC paper.
http://www.physorg.com/news/2011-03-earth-core-climate-insights.html
Another temperature proxy in need of “the trick” to hide the decline. The authors questioned everything for the breakdown in correlation except the GISS data.
———————————–
Exactly. If this is a good proxy for surface air temperatures, perhaps a better interpretation of the data would be in quantifying exactly how bad the purported surface air temperature data is due to UHI, other real reasons, Hansenization and other fabrications.
The problem with this particluar report is that its flashed aound all the medie here in Oz and even the Climate Change Minister is using it re the Carbon Tax. I rarely see the promptness (if at all) when a report comes out against the AGW. They still have full buy in to the AGW arguement in the establishment. Its going to take something dramatic to change it.
According to another paper from one of the coauthors, the actual contribution of Greenland to sea level rise should be negative: http://www.phys.uu.nl/~broeke/home_files/MB_pubs_pdf/2009_Ettema_GRL.pdf
Verity Jones, on her site ‘Digging in the Clay’ http://diggingintheclay.wordpress.com/
posted “Power and Fury” with two short videos of the ocean displaying some of its power around lighthouses off the coast of France.
My response was to comment, as follows:
An American novelist (Ivan Doig) has written books about Scots coming to the US and in one of those (Dancing at the Rascal Fair) one of the young men (Angus) tells a story of his great grandfather who worked on the Bell Rock Lighthouse, 11 miles off the county of Angus on the east cost of Scotland. One day as the tide comes there is no boat to take them back – but then it shows up. This seems to be the 200th anniversary.
http://www.bellrock.org.uk/
Also, claimed . . .
“The last sea-tower to be built in the days of sail.”
and
“The oldest sea-washed tower in existence.”
Also, info here:
http://en.wikipedia.org/wiki/Bell_Rock_Lighthouse
————————————
Being the 200th anniversary of the construction of this on a rock peaking just through the ocean’s surface one might suspect that it would be long ago submerged – being so close to the heartland of the industrial revolution.
However, there is a photo marker at the following coordinates (Google Earth) 56.413945, -2.405869
I wonder if the base is inspected occassionally to see if any repairs are needed and if there is any indication the ocean is any higher than in the past. The same goes for the lighthouses off the coast of France. Maybe there is a reader here that lives in the area and can inquire.
R. Gates says:
March 10, 2011 at 11:37 am
“The general trend of both Greenland and Antarctic continental ice, as well as most the major glaciers of the world is not in question…they are losing mass.”
R, dude, we have been through this before. Earth is dynamic. It is always changing. So, the fact that continental ice is losing mass is no news, at least not in itself.
If you could predict that continental ice will lose enough mass that the oceans will rise by four inches a decade over the next hundred years, then you would have our attention. But you cannot do that and neither can anyone else. You cannot because you have no set of physical hypotheses which can be used to make such predictions. You do realize that you have no such hypotheses, right?
If you could show a causal mechanism between increased concentrations of manmade CO2 and sea level rise of four inches a decade over the next hundred years, then you would have our attention. But you would need physical hypotheses to specify that causal mechanism. You are aware that you have none, right?
So, the sum total of your assertion is that continental ice mass is declining and manmade CO2 concentrations are increasing. Yet you have no idea whatsoever of some connection between them.
So, what are you asking us to do? Do you expect us to conclude that there is a connection when none can be specified in scientific terms? Do you believe we are fools? Al Gore believes we are fools. The AGW computer modelers believe we are fools. All they have are their hunches about the environment running as a computer simulation. Yet they too have no physical hypotheses that can be used to explain or predict sea level rise or the effects of rising CO2 on ice mass loss. Until you have the necessary physical hypotheses, you have nothing to say about the matter. Show humility. Express your hope that in forty years or so there will be a science of climate change based on real physical hypotheses. But there are none now. Nobody knows what sea level is going to do in the next ten or hundred years.
Enjoy the changes in ice mass along with the gazillion other changes that are happening all the time. End of story.
Wrong. The latest estimate from the new glacial isotatic adjustment models using new GPS data now shows that the rock below the center of the Greenland ice sheet is sinking not rebounding as previously thought. The new estimate is -230 GT/yr.
http://thegwpf.org/the-observatory/1438-ice-sheet-loss-cut-in-half.html
As a result Isostatic rebound now is called isostatic adjustment. Look at the before and after isosatic adjustment maps in the above link.
Doug Proctor says:
March 10, 2011 at 3:38 pm
Your “Reductio” argument is such a work of beauty that I am crying. Too bad the Warmista do not have a clue what you have just done. Being altogether averse to logic, they have not a clue what a “Reductio” is.
R. Gates says:
March 10, 2011 at 4:54 pm
I see your problem. Your time periods are way too short for the purposes of science.
Apparently, it the temperature was at a constant 15˚ C over Antarctica ice sheet all year round it still would take too long to even melt 1/5 of the ice.
Gates says:
“I’m 75% convince that AGW is happening and is caused directly or indirectly by the build-up on anthropogenic GH gases– primarily CO2. I am current 25% “skeptic” in that I constantly look at other possible explanations for 20th century warming. Those other explanation include:
1) Unknown solar effects
2) Unknown ocean cycles
3) Unknown astronomical effects”
Gates just gave us a perfect example of the argumentative fallacy, Argumentum ad Ignorantium: “Since I have no other explanation for the current Arctic cycle, then it must be due to CO2.”
Aside from the fact that there is no credible evidence showing that a few hundred parts per million of a minor trace gas is melting the Arctic, Gates ignores the elephant in the room: natural variability.
Three million years ago there was no Arctic ice cap. And wasn’t there a paper just submitted, IIRC, that said CO2 levels have been very low for the past 20 million years? So natural variability made the ice cap disappear naturally then, but Gates claims that now it’s different. Argumentum ad Ignorantium.
Drop the computer models, Gates, and step back. We need evidence, not GIGO. Where is your empirical, testable evidence that CO2 is melting the Arctic?
Or are you running on True Belief?
R. Gates says:
March 10, 2011 at 11:37 am
“Combine the shrinking year-to-year arctic sea ice, to ice mass loss in Greenland, Antarctica, and the majority (though not all) major glaciers around the world the 40% rise in CO2 since the 1700′s, and studies such as the one referenced above, and it would seem to get harder and harder to maintain a skeptics position. ”
====================
Please define “skeptics position”, as I may have one, but have yet to see a definition.
I think we are at the stage of this mania where those producing the evidence are simply blinded by their noble cause corruption.
Additionally, the new evidence that the ice sheets refreeze from the bottom calls into question the entire interpretation.
Unless CO2 changes the physics of water, and unless the AGW promoters can find evidence that somehow the deep water, against all evidence is warming, then there is a huge problem with the studies: The ice is not melting.
GRACE data can be interpreted by true believers all day long, but unless they can show a mechanism that causes melting in sub-freezing locations, they have a problem and they know it.
So much of AGW propaganda turns out to be magical thinking veneered over with science lingo. Sort of like a Start Trek dialog.
Here we go again … models … I think I have already said enough about them. Nothing to see here .. move along
Edit note for post:
Add to that, GRACE has it’s own set of problems. And at least one model conlcusion
its own set … conclusion
u.k.(us) says:
March 10, 2011 at 6:56 pm
R. Gates says:
March 10, 2011 at 11:37 am
“Combine the shrinking year-to-year arctic sea ice, to ice mass loss in Greenland, Antarctica, and the majority (though not all) major glaciers around the world the 40% rise in CO2 since the 1700′s, and studies such as the one referenced above, and it would seem to get harder and harder to maintain a skeptics position. ”
====================
Please define “skeptics position”, as I may have one, but have yet to see a definition.
______
My definition of skeptic…”I’m not convinced yet that x is happening and y is the cause. I’ll wait for more data”. Simple, but to the point.
Gates,
Wrong definition.
Skeptics merely say, “Prove it.”
But the alarmist crowd isn’t even close. They rely on True Belief.