NSF study: ‘…current carbon dioxide levels are not enough to destabilize the land-based ice on Antarctica’

We covered this yesterday, but today the official press release came out, so worth covering again. Via Eurekalert


Land-based portion of massive East Antarctic ice sheet retreated little during past eight million years

But increases in atmospheric carbon dioxide levels could affect stability and potential for sea level rise

NATIONAL SCIENCE FOUNDATION

Large parts of the massive East Antarctic Ice Sheet did not retreat significantly during a time when atmospheric carbon dioxide concentrations were similar to today’s levels, according to a team of researchers funded by the National Science Foundation (NSF). The finding could have significant implications for global sea level rise.

The East Antarctic Ice Sheet is one of three major ice sheets closely watched by scientists as global temperatures and carbon dioxide levels increase, glaciers melt and sea levels rise. Of the three, the East Antarctic Ice Sheet is the largest potential contributor to sea level rise.

To gauge the ice sheet’s stability, researchers took ultra-sensitive analytical measurements of chemical signatures in sediment samples taken from the ice sheet’s sea bed. They concluded that some ice on the southernmost part of the continent could be stable in a warming climate, as was the case during the Pliocene Epoch.

But they also caution that ongoing, rising carbon emissions mean that carbon dioxide levels will soon surpass the benchmark set during the Pliocene — approximately 5.3 to 2.6 million years ago — the last time Earth experienced carbon dioxide levels higher than 400 parts per million.

The findings were published today in the journal Nature.

The researchers relied on samples taken as part of the international ANtarctic geological DRILLing (ANDRILL) project. NSF funded the U.S. participation in ANDRILL.

This is image is by Peter Rejcek / NSF. CREDIT
Peter Rejcek / NSF

Examining sediment samples delivered from land-based sections of the ice sheet, the researchers found those areas that drain into Antarctica’s Ross Sea have been stable for the past 8 million years.

The geological history of the massive ice sheet — frozen both above and, in many places, below the ocean’s surface — has been difficult to pinpoint. The absence of data about the East Antarctic Ice Sheet’s response to warming in the past have hindered efforts to predict its role in future sea level rise.

This study focused on the portion of the ice sheet that sits above the ocean. It holds enough water to cause as much as 34 meters of sea level rise if the ice sheet were to melt completely.

Another component of the East Antarctic Ice Sheet, marine-based ice, sits below sea level and is thus directly affected by the ocean.

“Based on this evidence from the Pliocene, today’s current carbon dioxide levels are not enough to destabilize the land-based ice on the Antarctic continent,” said Jeremy Shakun, an assistant professor of Earth and Environmental Science at Boston College and a lead author on the paper.

“This does not mean that at current atmospheric carbon dioxide levels Antarctica won’t contribute to sea level rise. Marine-based ice is already starting to add to sea level rise and alone could contribute as much as 20 meters. We’re saying that the terrestrial segment of the ice sheet is more resilient at current carbon-dioxide levels.”

Shakun’s co-authors on the paper include Carling C. Hay, also of Boston College; researchers Lee B. Corbett, Paul R. Bierman, Kristen Underwood and Donna M. Rizzo of the University of Vermont; Susan R. Zimmerman of the Lawrence Livermore National Laboratory; Marc W. Caffee of Purdue University; and Tim Naish and Nicholas R. Golledge of Victoria University of Wellington, New Zealand.

Estimates on global sea level rise due to melt from the East Antarctic Ice Sheet during the Pliocene vary from 5 meters to more than 40 meters higher than today. The upper end of this range would imply that most of the ice on the planet melted, enough to raise sea levels by 63 meters.

If the land-based East Antarctic Ice Sheet was stable during the Pliocene, as Shakun and colleagues suggest, the Pliocene total could have been at most 30 meters.

The researchers analyzed sediment contained in drill cores taken from the sea floor. These cores contain geological records, but also chemical signatures — in particular, the rare isotopes beryllium-10 and aluminum-26, which were extracted at the NSF-funded Community Cosmogenic Facility at the University of Vermont and measured using particle accelerators at Purdue University and Lawrence Livermore National Laboratory.

Both isotopes are found in rock surfaces that have been exposed to cosmic radiation bombarding the Earth from outer space. Researchers usually examine rock samples from hillsides, mountain tops and rivers to determine where and when ice retreated during prior geological eras.

Shakun and some of the co-authors of the latest report used a different approach two years ago to offer one of the most comprehensive climatological accounts ever compiled of the Greenland Ice Sheet, dating back 7.5 million years.

In the Greenland study, levels of beryllium-10 found in sandy deposits brought out to sea in icebergs suggested the ice sheet has been a “persistent and dynamic” presence that melted and re-formed periodically in response to temperature fluctuations. The findings helped confirm that the Greenland Ice Sheet is a sensitive responder to global climate change.

Earlier studies of the East Antarctic Ice Sheet indicated that some marine-based portions of the ice sheet and its neighboring West Antarctic Ice Sheet retreated during the Pliocene. But it was unclear whether terrestrial ice also retreated.

Their analysis found “extremely low” concentrations of beryllium and aluminum isotopes in quartz sand in the marine sediment samples taken in the region, which leads to the conclusion that the ice sheet has been stable for millions of years.

While the sediment was the product of erosion from the continent, the low levels of tell-tale chemical signatures reveal that the sediment experienced only minimal exposure to cosmic radiation, leading the team to conclude East Antarctica must have remained covered in ice.

According to the paper’s authors, “the findings indicate that atmospheric warming during the past eight million years was insufficient to cause widespread and/or long-lasting meltback of the EAIS margin onto land.”

The findings not only clarify the past impact of rising temperatures on East Antarctic ice, said Shakun, but confirm the accuracy of models scientists are using to assess past and future consequences of a warming planet.

###

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ResourceGuy

If the land-based ice is not a problem, then the sea ice is not a reflection or extension of a land-based problem. Memo to the scare strategists

steve case

Antarctica is not melting, it’s well below freezing there nearly everywhere nearly all of the time. Antarctic ice mass balance is a function of snow that fell decades or centuries ago and the calving of ice bergs into the sea. Temperature has nothing to do with it. Hence CO2 has nothing to do with it.

The usual claim that it’s melting from underneath at the grounding line around the edges of the ice cap require warm water to sink and then flow uphill in order to accomplish the claimed melting.

If there is any melting, it’s due to vulcanism.

Hugs

Antarctica is not melting, it’s well below freezing

Hansen under oathpeer-reviewedly said that the sea level would rise 200 to 500 cm before 2100. That would require 2 cm/year or 0.8″/yr on average at this century.

‘Hansen’s best estimate was 2 to 5 meters (6–15 feet) by the end of the century’

So, we will soon see if Hansen was an idiot with a good paygrade, or a climate prophet, as Ed Markey (D) named him according to Seth Borenstein (AP). Or soon and soon, I guess we’ll all be dead before somebody at 2100 makes fun of Hansen.

There’s Popper for you. Yes, it is a scientific claim. It can be invalidated after I have been dead for 80 years.

HotScot

Hugs

by the time you’re gone we’ll have celestial laptops you can take with you, and me for that matter.

We can haunt the corridors of WUWT for millennia.

🙂

Roger Knights

Hansen’s high estimate of SLR was based on, not melting, but the rapid calving of ice from glaciers in Antarctica and Greenland, IIRC. That was also the basis of his West Side Highway under water prediction.

steve case

Whatever Dr. Hansen based his five meters possible by 2100 sea level rise on, it required a millimeter per day by December 2099.

Most of the breathless predictions that you read in the press, here’s an example


https://nextcity.org/daily/entry/hawaii-gets-explicit-about-sea-level-rise
that predicts 3.2 feet of sea level rise by 2060

simply don’t bother with the arithmetic which comes to an average of 23 mm/yr for the next 42 years.

WXcycles

It’s invalidated right now as the most melodramatic and hysterical “accelerated” CAGW worrier-rate is satellite pseudo-‘measured’ (i.e. projected), and computer-model ‘confirmed’ (i.e. hahaha) at a mere 0.6mm/yr, or just 60mm in one whole century of sea rise at that rate.

phft!

That’s totally in-CON-sequential! It’s a total joke, just like the other totally dimwitted nonsense about ‘acidifying’ carbonate super-saturated whole ocean basins! hahaha!

But it’s actually worse, as his prediction was for ~20mm/yr, but tidal guage actual observed data is (micro-arguably) just 0.33mm/yr. So then the actual degree to which Hansen is currently already totally wrong is a whopping;

20mm ÷ 0.33mm = 60.6 (times wrongishness)

So Hanson’s predicted rate of sea level rise is already greater than 60 times too small, thus he’s hysterically and laughably totally wrong now—this is a total non-event. Can you get more wrong than this? Well it’s only just possible to be even more wrong, it would take an Olympic-Gold medal effort but it could be made slightly more wrong.

But at the currently observed ocean rise rate of just ~0.33 mm/yr, it takes almost FIFTEEN HUNDRED YEARS for the ocean level to rise up to lower kneecap level!

arghahahaha!

Anyone who thinks that is, or will become a major ‘problem’, is a total DUNCE, and should be laughed out of town. And if they still persist with this utter rot, then flog them out of town, after a good and warranted tar and feathering.

1,500 years to get to your lower kneecap.

J Mac

Metaphorically, a glorious shaft of sunlight science just broke through the murky pollution of AGW propaganda.
The ‘catastrophists’ will be spinning this desparately….

J Mac

“The findings not only clarify the past impact of rising temperatures on East Antarctic ice, said Shakun, but confirm the accuracy of models scientists are using to assess past and future consequences of a warming planet.”

And that is the catastrophist (more funding, please!) spinning, David!

The authors claim that…

The findings not only clarify the past impact of rising temperatures on East Antarctic ice, said Shakun, but confirm the accuracy of models scientists are using to assess past and future consequences of a warming planet.

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This study has no relevance at all to “the accuracy of models scientists are using to assess past and future consequences of a warming planet.”

Ocean heat transport during the Pliocene was totally different than the Late Quaternary. The fact that it was 3-4 C warmer during the Pliocene with comparable CO2 levels, tells us nothing about the predictive skill of current climate models. Atmospheric CO2 has been relatively stable (200-500 ppm) for 25 million years…

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While temperatures have steadily declined since the Miocene…

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MarkW

If CO2 levels were similar and temperature levels were 3-4C warmer, then that is a direct refutation of the climate models.

Hugs

Is that 25Ma (8E14s in SI units;) ) stability because the cold circumpolar current keeps CO2 low?

Gary Pearse

Why is this written in such an equivocal manner. No problem in 8Myrs – Pliocene 400ppm CO2- on the one hand and that Gee we could be innundated with water 5metres up to 30meters. Plus our models have been validated by this. It seems the science didn’t have a problem with 400ppm and ice melt from WAS but the writers of the PR need some re-habilitation after decades of brainwashing catastrophy on the horizon.

J Mac

Just so, Gary!

commieBob

Ocean heat transport during the Pliocene was totally different than the Late Quaternary.

The Greenland ice sheet dates from when the Panama Seaway closed toward the end of the Pliocene. link

And that Seaway was one of the main reasons Pliocene ocean heat transport was more efficient.

Alan Tomalty

I am astonished that everybody missed the significance of the last sentence in the conclusion of the latest report on Antarctica melting.

“We suggest that variations in Antarctic ice volume in response to the range of global temperatures experienced over this period—up to 2–3 degrees Celsius above preindustrial temperatures4, corresponding to future scenarios involving carbon dioxide concentrations of between 400 and 500 parts per million—were instead driven mostly by the retreat of marine ice margins, in agreement with the latest models.”

What that last sentence says is that their own models are predicting no significant non – natural (CO2 by man ) melting of Antarctica due to a doubling of CO2 in the atmosphere from 280 to 560. What this means is their very own models are not predicting any disastrous effects from Antarctica melting. Don’t forget the 3C is the IPCC average sensitivity to a doubling of CO2. That sensitivity average hasnt changed in 30 years . If their very own models (over 125 worldwide) are saying that the cause is natural for Antarctica why wouldnt the cause be natural for Greenland as well? They actually said “driven mostly by the retreat of marine ice margins”. Well what that means is; they dont know the cause but they are saying that CO2 is a minor player. If CO2 is a minor player in ice sheet melting for a doubling of CO2 then it is a minor player in everything for CO2 doubling. Don’t forget that the models cannot tell them what % is by man and what % is natural.

That is the reason that the IPCC has always refused to put a number on it. Since the models can’t split out the effects of man vs natural, when they ran the simulations both forward and backward ; the forward simulation effects of the future of the ice melting must have ended up to be exactly the effects of the models running backward as well. Since the variables data are the same for both simulations the same results were obtained. That in itself is remarkable given the models propensity to become chaotic when running simulations. They in effect have had to fine tune out these chaotic simulations by flattening out the parameterizations for very long term predictions.

For the researchers to have admitted this in other reports is also astonishing . What this paper means is that there is no disaster syndrome. They are in effect admitting that RCP8.5 is impossible because RCP8.5 is a business as usual scenario with emissions continuing to rise. I am making the statement that in this case of Antarctica melting there cant be any CO2 effect if the same effects happened with the same input variables with the only difference being CO2 levels. If there isnt any effects on CO2 doubling there cant be any effects on CO2 quadrupling or more. RCP8.5 says that 5C increase happens only after 2081 to 2100.
Even the IPCC admits that 3C difference in the RCP8.5 doesnt kick in until after 2065 ; 47 years from now . If the doubling of CO2 doesnt produce any greenhouse effect on ice melting then all bets are off. The AGW house of cards falls flat on its face. Dont forget that Dr. Pierre Robitaille has proved that CAGW is impossible because of the fact that CO2 and H2O decrease emissions of back radiation with increase in temperature. Dr Michael Modest has also stated that in his bible of Radiative Heat Transfer.

I am sure the researchers will be getting a nasty call from both Gavin Schmidt and Michael Mann.

1) Since melting of the Arctic would only add 20mm and melting of all 200000 glaciers would add 400mm and if you take Greenland and Antarctica out of the picture then what do we have to worry about?

2)A measly 3C for a doubling of CO2 to 560PPM . We are way below the target of 3C anyway based on the past 70 years and it looks like it will take another 70 years to get to 560ppm. Is anyone in the world going to die of heat prostration from an increase of 3C especially since we got 50 -70 years to warn them ? What else is there to worry about?
3) Since CO2 is NOT responsible for extreme weather events. We know this since every government agency in the world that tracks these stats shows no increase in extreme weather events. Come to think of it Trump should protect the American extreme weather events databases from possible tampering by NASA, NOAA, and NCAR. I am astonished that I am living in a world that I would ever have to make the previous suggestion.

4) So the only other possible detriment to CO2 is that study that found some decreased levels of vitamins from crops that were grown with doubled CO2 levels. Well the amounts were small and there wont be malnutrition caused by that.

SO I FEEL LIKE ALFRED E. NEWMAN (fictional character) with his famous saying. “Whatttttt me worry?

Epilog: I would be happy except my PM Trudeau in Canada wants to bring in around $74 to $112 billion extra greenhouse gas taxes over next 5 years. All of that money will have been collected to decrease the world’s average temperature by 5/1000 of a degree C and that will only be 82 years from now. We in Canada unfortunately are living in the World of Oz and desperately need Toto to learn how to pull back the curtain

WXcycles

@Alan
” … Don’t forget that the models cannot tell them what % is by man and what % is natural. That is the reason that the IPCC has always refused to put a number on it. Since the models can’t split out the effects of man vs natural, … ”

Nah, just assume 100% is human caused, and play the long game, as that way when later on (or sooner?) this century when we get a 40 year ‘hiatus’, with some slow cooling component within it, that also will then have to be attributed to 100% human CO2 emission caused.

Ah, but the resulting cognitive-dissonance will be only micro-epic, as after about 3-days they’ll edit the documented reality and their rubbery facts™, and pretend that their religious belief (nay, hyper doom zealotry) was really just 97% a theory, and that they were really just being 97% super-sciencey, all along.

And thus is the foul one made ‘purified’, and doth come their salvation and righteousness—all self-excused with a hand-wave and quip!

It’ll work too.

Thus verily was the mortgage payed-off.

MarkW

Fascinating how they are focusing on CO2 levels, instead of the actual temperatures.

David Clothier

How can this be correct?

This study focused on the portion of the ice sheet that sits above the ocean. It holds enough water to cause as much as 34 meters of sea level rise if the ice sheet were to melt completely.

In order to raise sea levels 34 meters, doesn’t there have to be enough frozen water in the Antarctic to cover all the oceans + the addition land masses under 34 meters above sea level ? If all of Asia was covered in 34 meters of ice and it melted, it would not be able to raise just the Pacific Ocean 34 meters, let alone all the oceans.
Is that supposed to be 34 millimeters?

tty

The ice is about 3 kilometers thick in East Antarctica. If it should all melt sea-level would rise about 60 meters. If the ice in West Antarctica should melt it would only rise a bit over 3 meters.

Trevor

“tty” I HAVE A QUESTION FOR YOU :
ANTARCTIC ICE . 3 km thick ICE . Must weigh quite a bit ! Yes ?
As it melts and runs off the land WON’T THERE BE REBOUND OF THE
LAND due to release FROM the vast ICE WEIGHT ?
Doesn’t THAT mean that somewhere the OCEAN FLOOR will SINK to
compensate for the UPLIFT of the LAND that was previously COMPRESSED ?
If SO , then there will be ROOM FOR THE WATER TO GO
without raising SEA LEVEL MUCH AT ALL.
If NOT…….then WHY NOT ?

tty

In short “Yes”. When an ice-sheet melts the rock underneath it will rise and the “forebulge” around it will sink back. But there will not be “room for all the water” for two reasons.

1. Isostatic adjustment is a slow process, 12 000 years after the end of the latest ice-age it is still going on in Northern Europe and Canada. Rock flows slowly.

2. Glacier ice has a density of about 0.9, rock is about three times denser, so it takes 3 cubic kilometers of ice to displace 1 cubic kilometer of rock.

So some day, perhaps after 20 000 or 30 000 years there will be room for something like a third of the water.

Johnboy

The study did not suggest that there would be no melt of East Antarctic. It estimates that, based on the similar warming of the Pliocene, East Antarctic would not be complete melt Of it. The report made now estimate of sea level rise back then The author suggests that even w/o East Antarctica, could see sea level rise of 65 feet. What a relief, eh? But the current issue is not how much sea level could rise in thousands of years. It’s about the amount of rise by the end of the century, which will have all sorts of problems for coastal communities and island nations. Leave it to WUWT to distort the point of the study with its headline and intro.

The study concluded that marine sediments under the Ross Ice Shelf have been covered with ice pretty well continuously for 8 million years. What does that tell you about the interior of the East Antarctic continental ice sheet?

tty

No. The rock grains in the sediments come from East Antarctica (mostly the Transantarctic Mountains and the Wilkes Subglacial basin). The lack of B10 and Al26 means that the source areas haven’t been ice-free for a very long time.

tty

As a matter of fact if all ice outside East Antarctica melts the sea-level would only rise about 30 feet.

tty

This more or less kills off fantasies about the Wilkes subglacial basin being ice-free in the Pliocene (something that was highly unlikely in any case given that ice in the Transantarctic Mountains was actually more extensive than now during the Pliocene).

And last year studies of the sediments offshore of the Aurora subglacial basin showed the same – no appreciable retreat during the Pliocene (http://sci-hub.tw/10.1038/nature25026).

And those two basins are the only parts of East Antarctica where there was even a remote chance of instability.

In short: the EAIS has been stable since the Middle Miocene. And the study of the Aurora basin mentioned above showed that there was an extensive icecap in East Antarctica which reached the coast in places even during the extreme hothouse climate of the early and middle Eocene.

Kristi Silber

tty, It seems to me it depends on what you call “stable.” From your link:

“Subsequently, ice advanced across and retreated from the Sabrina Coast continental shelf at least 11 times during the Oligocene and Miocene epochs.
Tunnel valleys associated with half of these glaciations indicate
that a surface-meltwater-rich sub-polar glacial system existed under
climate conditions similar to those anticipated with continued
anthropogenic warming. Cooling since the late Miocene
resulted in an expanded polar EAIS and a limited glacial response
to Pliocene warmth in the Aurora subglacial basin catchment.
Geological records from the Sabrina Coast shelf indicate that, in
addition to ocean temperature, atmospheric temperature and
surface-derived meltwater influenced East Antarctic ice mass
balance under warmer-than-present climate conditions. Our results
imply a dynamic EAIS response with continued anthropogenic
warming and suggest that the EAIS contribution to future global
sea-level projections may be under-estimated” (Numbers associated with citations removed for easier reading)

tty

Kristi: It is well known that Antarctica was periodically partially ice-free between the Oi-1 glaciation 35 million years ago and the Middle Miocene about 15 million years ago (though it was not previously known that there were so many oscillations, nor that there was tidewater glaciation before Oi-1). The described seabed geology is similar to what you find e. g. off Greenland, which is also intermittently partially ice-free.

Your citationing is however somewhat selective:

“An expanded polar EAIS occupied the ASB catchment and the Sabrina Coast continental shelf since the late Miocene, coincident with global climate, carbon and hydrologic cycle reorganizations, continent-wide ice-sheet expansion and stabilization, Antarctic
Circumpolar Current intensification, Southern Ocean cooling, and modern meridional thermal gradient development. Atmospheric cooling probably limited the amount of regional surface ablation, resulting in ice expansion and reduced surface-derived meltwater in the ASB catchment. Although open marine conditions intermittently existed on the shelf, the relative MS-III thickness and patterns of erosion within the ASB catchment suggest a maximum retreat of about 150km from its present location since the late Miocene. ”

That is about 10 million years of stability, including the Pliocene warm interval.

Red94ViperRT10

“…ice advanced across and retreated from the Sabrina Coast continental shelf at least 11 times during the Oligocene and Miocene epochs…”. In other words, same as it ever was! Even if the icecaps at both poles ceased to exist, whether just for one summer or “permanently” (longer then one summer), we have evidence it has happened before, and we are still here to talk about it! It ain’t no big deal, people! Get over it! The amount of money wasted on this AGW crap – the research, the unnecessary construction of useless windmills and solar farms (neither of which do anything to alter the temperature of the planet anyway) and the gratuitous rate increases in the prices for all energy – since the rigged Congressional presentation in 1988 (that 30 year anniversary is only months away) that money could have constructed the power plants and/or distribution to provide cheap reliable energy (maybe distributed generation) to everyone, all the way down to the most remote mud hut in Africa! And that’s the way to deal with this. People live all over this Earth, all the way from Antarctica to Djibouti, so even if extremes become more extreme for any particular location (and there is no evidence indicating they might) the best way to survive it is to make sure those residents so affected have plenty of cheap reliable energy!!! And if I misestimated the costs of building out a world-wide-grid, prove it with numbers and cite your references!

Sparky

The last sentence supporting models and Green-guesstimates seem contrary to the empirical evidence and historical known. A lot of cognitive dissonance and Gumby back twisting here by the climb-jedis.

Wiliam Haas

Despite the hype, there is no real evidence that CO2 has any effect on climate and plenty of scientific rational to support the idea that the climate sensitivity of CO2 is zero.

Kristi Silber

“The findings not only clarify the past impact of rising temperatures on East Antarctic ice, said Shakun, but confirm the accuracy of models scientists are using to assess past and future consequences of a warming planet.”

What I take from this is that when scientists run their models using data from past climate, the simulations are in good agreement with the evidence collected by the authors of the paper. So, this evidence confirms the accuracy of those models. Those models are the same ones used to assess future consequences of climate change. Therefore, the evidence collected by the researchers supports the accuracy of models used to “assess past and future consequences of a warming planet.”

I am not arguing that this claim is true – I don’t know, I haven’t read the paper – but at least this interpretation makes sense of the PR.

At any rate, there is always much more to the actual research than what is stated in the PR.

WXcycles

Oh really? Then what caused the LIA and MWP, Kristi?

The audacity to dope.

The “models scientists are using to assess past and future consequences of a warming planet” retro-cast the past instrumental record (<150 years) fairly well and have failed miserably at predictions of "furure consequences" over the past 30 years. When run over the course of the Holocene, those same models retro-cast Pleistocene glacial stage conditions during the Medieval Warm Period (slight hyperbole). These models can't even be applied to the Pliocene because atmospheric and oceanic circulation patterns were totally different.

It is nothing short of a bald faced lie ro say that this study confirms anything about general circulation models currently being used "to assess past and future consequences of a warming planet.”

tty

“there is always much more to the actual research than what is stated in the PR”

That is putting it diplomatically. Often they are completely different. This is what the paper actually says:

“Together with prior evidence for open waters at the AND-1B site during the Pliocene, our
findings agree with model simulations which show that the terrestrial EAIS experiences minimal melt when carbon dioxide levels are at their present value of roughly 400 parts per million for extended periods of time, whereas some marine-based ice-sheet sectors largely disappear”

So the data supports the stability of the EAIS, which is in accord with modelling. It isn’t really relevant to instability of marine-based ice-sheets (open water at AND-1B does not require collapse of the WAIS), but does not disprove it either.

Incidentally if we equate open water at AND-1B with WAIS collapse, then the WAIS has not collapsed since the MIS31-33 “superinterglacial” more than a million years ago.

Trevor

KRIST !!! Sorry Kristi !!
YOU QUOTE :
“this evidence confirms the accuracy of those models. Those models are the same
ones used to assess future consequences of climate change.”
YOU MEAN THE SAME MODELS THAT HAVE BEEN PREDICTING……WRONGLY…..
FOR SO LONG ……….HAVE NOW GOT IT RIGHT ALL OF A SUDDEN ????????
THEN YOU STATE:
“I am not arguing that this claim is true – I don’t know”
NOW……….. THERE………I AGREE WITH YOU !!

tty

And they aren’t the same models. Models that include glaciology are separate from GCM:s.

Kristi Silber

Thank you for your input, tty; you have far more knowledge of the matter than I. I wondered whether the models the authors claimed their work supported were not actually GCM models – it’s impossible to tell from the PR (I bet PRs are responsible for much media mediocrity, not to mention many mistakes here). The evidence supports “model simulations which show that the terrestrial EAIS experiences minimal melt when carbon dioxide levels are at their present value of roughly 400 parts per million for extended periods of time.” Were these models run according to estimated Pliocene conditions, and are the same ones used to project future states using different data?

Do you, or does anyone here, have a non-paywalled link to the full study? I could only find the abstract.

tty

You can get the study from sci-hub.tw by searching for the doi-number.

Kristi Silber

GENERAL COMMENT
As I said, I don’t presume to know whether the authors are correct – for me there is no shame in admitting insufficient knowledge. I am mainly concerned that some people may be making assumptions that the authors are “lying” without adequate evidence and based on potential misinterpretations of their words. In my experience this is not uncommon, nor is it uncommon to choose to believe evidence that appears to support a narrative while ignoring or dismissing the evidence that doesn’t.

As it stands (and assuming that the scientists are not fools or frauds), I take this research to simply be more data on which to build a better understanding of Antarctic climate, what affects it, and how it fits with effects and influences of global climate. This is an area that researchers admit is still incompletely understood. I am well aware that it is not the only one, and that climate models are not perfect; they are works in progress. It doesn’t trouble me that they are not able to accurately predict every climate parameter, and I am certainly not concerned that the climate fluctuations over the last 30 years were not accurately predicted by GCM models developed 30 years ago. Not only are those models old, they were not designed to predict short-term natural variability like ENSO and vulcanic eruptions. The models will never be able predict the future with any precision no matter how much physical data and theory they have or the perfection of the models because they cannot anticipate the human effect, not just on GHG emissions, but on land use. This affects the sources and sinks of GHG and water vapor, albedo, energy storage and atmospheric particulate matter.

I don’t understand the assertion that GCM projections have completely failed. For instance, they correctly suggested an increase in Antarctic snowfall. (This is a nice summary of modeling Antarctica, including its pitfalls – https://www.environments.aq/information-summaries/predicting-antarctic-climate-using-climate-models/ Any quibbles with it? ) I’ve seen many graphs on WUWT purporting to show failure of predictions, but there is so much posting of poorly-explained, cherry-picked data, ignoring caveats, uncertainty, and original interpretations, that I no longer take them at face-value. David’s graphs above are a case in point. I don’t know if “Pagani, 2005 alkenones” actually refers to Freeman and Pagani, 2005, or what it even means. The “Tirpati” [sic] reference, as far as I can tell, actually refers to research done at Sri Venkateshwara Univ., Tirupati, based on one area near India. Couldn’t figure out where he got the data on stomata from Royer, 2006, but I could have missed it (I’m not yet convinced stomatal indices are a good proxy for CO2 levels, anyway). There are no error bars. A graph like this, with no explanation of how the data are derived, is meaningless to a real skeptic, and David didn’t post a link to anything that might explain it.

The second graph is worse. David does not state that it represents oxygen isotopes (or temps) in the deep sea or that the temperature calculation is for ice-free oceans and only applies until the period before about 35 mya; it is therefore not evidence that temperature “steadily declined in the Miocene,” as he asserts. From the early Oligocene to the present, much of the variability in oxygen isotopes reflect ice volumes at N and S poles. This is all in the caption to the original graph, so it’s hard to imagine how he could have missed it – yet he accuses others of lying?(http://www.essc.psu.edu/essc_web/seminars/spring2006/jan18/Zachosetal.pdf) (Oh, I see David provides a caption elsewhere: ” The left vertical axis uses a conversion suitable for the Quaternary; however, the baseline is probably wrong. SST’s shouldn’t be negative. However, the relative change should be reasonably accurate.”

Whose conversion? And how are we supposed to read a graph that has two different temperature scales, when it’s based on a continuous set of isotope data? Am I not getting something here?

After countless examples of WUWT article writers making questionable or false assertions and misrepresentations of quotes, research and data, many (not all) have lost credibility with me (not that they care).

I want to keep an open mind. I am no climate scientist, and it’s possible that skeptics are right and the dangers are overestimated. However, after two years of reading skeptics’ arguments and checking them against their sources, my overwhelming impression is that policy and prejudice are far more influential than scientific integrity. That doesn’t mean that mainstream science has everything right, but I’m more inclined to trust peer-reviewed research and articles that discuss weaknesses in our current science in a constructive manner, with the goal of improving rather than disproving it.

The conversion of δ18O temperature varies with oceanic conditions.

The temperature scale on the right axis is suitable only for an ice free ocean. Zachos et al, 2001 clearly state this in their paper. As such, they also state that it only applies before the Early Oligocene. They also state that the deepwater benthic foram’s used in their study were a suitable proxy for high latitude sea surface temperatures.

In order to approximate SST since the Early Oligocene, I used Epstein (1953), described here…

Based on the simplifying assumption that the signal can be attributed to temperature change alone, with the effects of salinity and ice volume change ignored, Epstein et al. (1953) estimated that a δ18O increase of 0.22‰ is equivalent to a cooling of 1 °C (or 1.8 °F).[2] More precisely, Epstein et al. (1953) give a quadratic extrapolation for the temperature, as

T = 16.5 – 4.3*δ18O + 0.14*δ18O^2

where T is the temperature in °C (based on a least-squares fit for a range of temperature values between 9 °C and 29 °C, with a standard deviation of ±0.6 °C, and δ is δ18O for a calcium carbonate sample).

https://en.m.wikipedia.org/wiki/Δ18O

Personally, I don’t care how you “read” the graph. Ice volume today is massively higher than it was during the early Cenozoic and salinity is also higher. So, as the authors state in the paper, the SST scale on the right axis is unsuitable for the period of interest, the Pliocene.

The fact that it yielded negative numbers for SST, leads me to think that the temperatures are too low. However, the relative change in temperature is accurate because a “δ18O increase of 0.22‰ is equivalent to a cooling of 1 °C.” Had I used the same equation as Zachos, the temperatures would have been even lower.

dmacleo

Marine-based ice is already starting to add to sea level rise and alone could contribute as much as 20 meters
**********************************************
ok that statement has bugged me, isn’t marine based ice positioned over actual water meaning its displaced water to form and melting adds nothing?
or am I misunderstanding term marine based ice?

Pillage Idiot

“Marine ice” is a category of sea ice. It refers to ice that is grounded on the sea floor.

The melting of this type of ice would raise sea level.

tty

Marine-based ice is not sea-ice. It is glacier ice based on bedrock below sea-level.

And there isn’t nearly enough of it to raise sea level 20 meters.

There is very little of it in the northern hemisphere, and the two significant subglacial basins in East Antarctica (Aurora and Wilkes) are highly stable . Remains the marine-based ice in West Antarctica which paradoxically would have rather limited effect on sea-level because the bedrock is up to 2000 meters below sea-level, which means that most of the melt-water would be used up to fill out the same volume it occupied as ice (sea-water is more than 10% more dense than glacier ice). A complete collapse of the WAIS would raise sea level a little more than 3 meters, i e less than half as much as a complete melting of the Greenland Ice:

https://www.researchgate.net/publication/24428838_Reassessment_of_the_Potential_Sea-Level_Rise_from_a_Collapse_of_the_West_Antarctic_Ice_Sheet

dmacleo

thank you both, you’ve given me a direction to search in.
wondered if was a terminology item that escaped me.

Johann Wundersamer

“This does not mean that at current atmospheric carbon dioxide levels Antarctica won’t contribute to sea level rise.

Marine-based ice is already starting to add to sea level rise and alone could contribute as much as 20 meters.” — won’t happen in the lifetime of that “researchers”.

Mankind’s evolution spans 2-4 mil. years.

Antarctic Ice Shield endured 100s of mill. years.