The Latest Antarctic Ice Sheet Alarmist Con

The media is buzzing frenziedly with tales of the impending doom of almost a quarter of the West Antarctic ice sheet, with ‘catastrophic’ rises in sea levels as a consequence. A new Antarctic ice loss death spiral study has been released and the lame stream media are loving it. I was going to comment on Geoff’s article, but the comment got too long, so I decided to post my observations here instead.

Despite being ‘new’, Shepherd’s paper tells us very little that is new. We already knew that that the Thwaites and Pine Island glaciers in the Antarctic Peninsula have been rapidly thinning since the 1990s.

The authors admit that the overall height of the Antarctic ice sheet has changed very little:

Although most of the AIS surface has changed little in elevation over the past 25 years (Figure 2), there are clear patterns of thinning and thickening in coastal sectors -especially in WAIS and the APIS.

So what do they do? They use models to supposedly discriminate between snow accumulation and ice sheet melting below the surface and demonstrate somehow that ‘vast’ areas of West Antarctic are in ‘dynamical imbalance’.

Changes in Antarctic ice sheet elevation arise predominantly due to fluctuations in accumulation and ice flow, which occur at the densities of snow and ice, respectively (Wingham, 2000). These processes can be distinguishable in altimeter records due to their coincidence with areas of rapid or changing ice flow, or due to their persistence over periods that are long in comparison to expected snowfall fluctuations. To discriminate them, we adjusted the satellite elevation changes to account for fluctuations in surface mass balance by removing model estimates of the firn layer thickness change (Ligtenberg et al., 2011; Melchior Van Wessem et al., 2018). We then classified regions exhibiting correlated patterns of sustained and significant thickening or thinning relative to the firn thickness changes as areas of ice dynamical imbalance.

Yay, guess what, they also found that Pine Island and Thwaites glaciers were retreating! Like, wow, what a surprise!

At the Totten glacier, dynamical imbalance affects just 3.6% of the drainage basin, and we found little evidence that either this or the rate of elevation change have changed over the 25-year survey. In contrast, ice drawdown within the Pine Island and Thwaites glacier drainage basins has spread rapidly inland, and now affects the majority (51% and 68%, respectively) of their catchments.

By far the largest signal of imbalance has occurred in the Pine Island and Thwaites glacier drainage basins (Figure 3), which have lost mass at average rates of -28±6 Gt/yr and -46±7 Gt/yr, respectively, since 1992 (Table 1).

But they’ve got models:

We used our classification of ice dynamical imbalance as the basis of a spatially-resolved mass balance calculation, as it allows us to separate elevation changes predominantly occurring at the densities of snow and ice. Our classification is an improvement over previous schemes because it uses model estimates of firn thickness change to locate the change in ice thickness, rather than attributing elevation changes within entire drainage sectors (Wingham et al., 1998) or otherwise defined regions (Shepherd et al., 2012)to ice. It does not, however, account for potentially coincident signals of meteorological and dynamical imbalance, and this is an acknowledged shortcoming.

And they estimated snowfall:

We instead treated snowfall as an additional source of elevation change uncertainty in mass balance calculations by summing an estimate of its variability (Table 1) in quadrature with the satellite elevation trend uncertainties.

While we’re on the subject of snowfall in Antarctica, I came across this little nugget a few years ago:

The Amundsen Sea sector of the West Antarctic ice sheet has been losing mass in recent decades; however, long records of snow accumulation are needed to place the recent changes in context.
Here we present 300 year records of snow accumulation from two ice cores drilled in Ellsworth Land, West Antarctica. The records show a dramatic increase in snow accumulation during the twentieth century, linked to a deepening of the Amundsen Sea Low (ASL), tropical sea surface temperatures, and large-scale atmospheric circulation. The observed increase in snow accumulation and interannual variability during the late twentieth century is unprecedented in the context of the past 300 years and evidence that the recent deepening of the ASL is part of a longer trend.

Oh dear. Definitely not what the Graun editor would like to see at this point in time when she is no doubt contemplating a change in the ‘style guide’ re. boring old ‘Antarctic ice loss’, following this latest catastrophic news that it’s worse, so much worse than we thought. ‘Antarctic meltdown’ is probably high on the list of options.

Then there’s this equally inconvenient study by Zwally et al at NASA:

“We’re essentially in agreement with other studies that show an increase in ice discharge in the Antarctic Peninsula and the Thwaites and Pine Island region of West Antarctica,” said Jay Zwally, a glaciologist with NASA Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study, which was published on Oct. 30 in the Journal of Glaciology. “Our main disagreement is for East Antarctica and the interior of West Antarctica – there, we see an ice gain that exceeds the losses in the other areas.”  Zwally added that his team “measured small height changes over large areas, as well as the large changes observed over smaller areas.”

All Shepherd has done really is confirm that the Thwaites and Pine island glaciers have been melting and he’s used models of firn ice melt and estimates of snowfall to conclude that 24% of West Antarctica is now ‘unstable’. Ridiculous.

Lastly, but not leastly, global warming (or should that be global heating now?) has taken time off in Antarctica, so it can’t be the dreaded CO2 Thermageddon ‘death rays’ reflecting back onto the Antarctic ice which are causing it to melt ‘deep in the interior’. Got no idea what that might be to be honest . . . . .

The Antarctic Peninsula (AP) is often described as a region with one of the largest warming trends on Earth since the 1950s, based on the temperature trend of 0.54 °C/decade during 1951–2011 recorded at Faraday/Vernadsky station. Accordingly, most works describing the evolution of the natural systems in the AP region cite this extreme trend as the underlying cause of their observed changes. However, a recent analysis (Turner et al., 2016) has shown that the regionally stacked temperature record for the last three decades has shifted from a warming trend of 0.32 °C/decade during 1979–1997 to a cooling trend of − 0.47 °C/decade during 1999–2014.




  1. Jaime, thanks for a good summary of this latest Antarctic false alarm. The only point to add is the fact of sub-glacial volcanoes under that continent. In 2017 they had identified 91 such active sites underneath the Antarctic ice sheet, particularly on the Western side. For everything you want to know (but afraid to ask) here is a link (H/T tty) to glacial dynamics different for cold and warm glacial bases.


  2. Thanks Ron. I knew about the volcanic activity; was just leaving it for others to point out. It’s not a subject I know much about and I have no idea whether or not these volcanoes have significantly contributed to erosion of glaciers in the West Antarctic. But even so, I find that entire Graun article breathtakingly dishonest and it would seem that Shepherd himself is complicit in that dishonesty by conveying the message that West Antarctica is under imminent threat of melting due to man-made climate change.

    “A complete loss of the West Antarctic ice sheet would drive global sea levels up by about five metres, drowning coastal cities around the world. The current losses are doubling every decade, the scientists said, and sea level rise are now running at the extreme end of projections made just a few years ago.

    The research, published in the journal Geophysical Research Letters, compared 800m satellite measurements of ice sheet height from 1992 to 2017 with weather information. This distinguished short-term changes owing to varying snowfall from long-term changes owing to climate.”

    “From a standing start in the 1990s, thinning has spread inland progressively over the past 25 years – that is rapid in glaciological terms,” said Prof Andy Shepherd, of Leeds University in the UK, who led the study. “The speed of drawing down ice from an ice sheet used to be spoken of in geological timescales, but that has now been replaced by people’s lifetimes.”

    “Along a 3,000km [1,850-mile] stretch of West Antarctica, the water in front of the glaciers is too hot,” he said. This causes melting of the underside of the glaciers where they grind against the seabed. The melting lessens the friction and allows the glaciers then to slide more quickly into the ocean and therefore become thinner.

    Too hot? Climate change caused the water just along this particular stretch to become ‘too hot’? What kind of nonsense is that? Maybe volcanic activity caused it to become ‘too hot’, not GHG emissions from cars and factories in far off places like China, India, and the USA? Now there’s a radical thought.


  3. Ron, I skipped through the study which identified the 138 volcanoes. The authors do not believe that volcanic activity has contributed significantly to recent glacial retreat in West Antarctica:

    “Currently, the WAIS may be undergoing another such wholesale retreat, as ice in the Pacific-facing sector has consistently been retreating from the time of the earliest aerial and satellite observations (Rignot 2002; McMillan et al.2014; Mouginotet al.2014). We do not consider it likely that volcanism has played a significant role in triggering the current retreat, for which there is compelling evidence that the forcing has initiated from the margins (Turner et al.2017), but we do propose that subglacial volcanism has the potential to influence future rates of retreat by (1) producing enhanced basal melting that could impact upon basal ice motion and (2) providing edifices that may act to pin retreat.”

    So I went to Turner et al’s paper which blows the concept of ice melt in West Antarctica being due to anthropogenic global warming clean out of the water, clearly pointing the finger of blame at changing ocean circulation bringing warmer waters to the shelf, possibly forced by atmospheric circulation changes. It’s a very long paper full of lots of interesting bits of information, so I’ll probably write it up as a kind of follow up to this post when I get the time. Thanks for the references!


  4. Off-topic – interesting news from Australia. The BBC said this morning that the Labor party was expected to win narrowly, and that climate change was a key issue in the campaigning. When I heard that, I thought maybe I should put a bet on. Regrettably, I didn’t.


  5. Should have taken the bet Paul..the great unwashed..voted against “climate action” whatever that idiocy means…everyone is “shocked” no we were not…the next card they might play is “russia dunn it”


  6. Obviously, Aussies weren’t that impressed by news that Antarctica was melting down on the day they went to the polls with the opportunity of voting for somebody who would reverse the decline with more windmills and more blackouts. They looked at the apocalyptic news and thought, “No worries, mate”. Labor are now considering giving penguins the vote.


  7. If Australia has been “lost”, where could it be? Did Brad have any part in causing this deprivation? Loss of an entire continent puts climate catastrophe (or whatever the latest shock-jock name for it is) in its place, doesn’t it?

    Liked by 1 person

  8. JAIME
    Thanks for putting some factual flesh on the bones of my rant. I like to keep my criticisms science-free, since my point is that a lot of the time no science is needed to see through the argument. The Guardian article managed to disprove its own point with its zigzagging graph, each zig being derived from a different satellite, and its 99.9% empty map of Antarctica.

    I’m curious to know whether the papers you cite deal with Shepherd’s big claim about Antarctica in the Attenborough programme, which was that  “…Antarctica is losing three times as much ice today as it was twenty five years ago.” Well, not that curious, not enough to actually read them. Since it is apparently impossible to measure the amount of ice without complicated models, I wonder how you manage to measure the rate of change in the growth or loss of ice?

    Liked by 1 person

  9. Loss is an entirely relative concept. When you’ve lost your mind and failed to convince a whole bunch of people to similarly lose theirs, I guess it can feel like a bereavement.

    Liked by 1 person

  10. We have to take these scary global warming warnings seriously, if we don’t, there will be no one prepared to pay those people for the work that they do. They are only trying to give meaning for the research they do. But neglecting their professional duty as a serious scientist, while trying to make a big deal out of nothing and misrepresenting their research, is an utter disgrace.


  11. Alarmists are always full of ‘ice loss’ dramas, but what about the gains?

    NASA Study: Mass Gains of Antarctic Ice Sheet Greater than Losses (2015)

    A new NASA study says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.


  12. This could be described as the ever expanding WAIS-line.

    “Giant ice sheet’s break-up ‘is a warning to world'” By David Derbyshire, Telegraph, March 2002 20/03/2002)

    “An ice shelf the size of Somerset has disintegrated off the coast of the Antarctic in less than a month, following decades of unusually warm weather.”

    2005-Scientists screaming: 2005
    “The controversial Kyoto Protocol becomes law next week, as scientists are all but screaming that the world is on a path to disaster unless we stop global warming.

    The birth of the controversial protocol, which runs until 2012, comes amid the most serious warnings yet that climate change is accelerating and humans have only a 10-year window in which to turn the problem around. While a small pocket of scientists remains unconvinced that climate change is a result of human
    intervention, most are now talking about how much warming the Earth can withstand to avoid huge impacts on the environment, such as the polar icecaps melting.”

    “humans have only a 10-year window” That would be 2015, enter the Paris Agreement, Son of Kyoto.

    2005 was the year the Blair government really stepped up the rhetoric, built around the Exeter Conference on Dangerous Climate Change, reported on by Benny Peiser here:

    It gave Chris Rapley a taste for appearing on stage, presenting the material summarised in their press release.

    BAS Press Release
    “Antarctica – an awakening giant?” BAS Press Release no. 03/2005 02 Feb 2005

    “The contribution that rapid thinning of the Antarctic ice sheet is making to global sea-level rise is a cause for concern according to Director of British Antarctic Survey (BAS), Professor Chris Rapley. speaking this week at a conference* in Exeter. The last IPCC report characterised Antarctica as a slumbering giant in terms of climate change. I would say that this is now an awakened giant.”

    Rapley seemed unaware that BAS was about to issue a Press Release 3 weeks later, that showed Antarctic Ice Shelves had collapsed before: Press Release 4/2005 23 Feb 2005

    “The retreat of Antarctic ice shelves is not new according to research published in the journal Geology by scientists from Universities of Durham, Edinburgh and British Antarctic Survey (BAS). (24 Feb, 2005)

    A study of George VI Ice Shelf on the Antarctic Peninsula is the first to show that this currently ‘healthy’ ice shelf experienced an extensive retreat about 9500 years ago, more than anything seen in recent years.”

    It mattered not, the narrative had to be maintained.

    BAS Press Release: First direct evidence that human activity is linked to Antarctic Ice Shelf Collapse
    16 Oct 2006

    “The first direct evidence linking human activity to the collapse of Antarctic ice shelves is published this week in the Journal of Climate. Scientists …. reveal that stronger westerly winds in the northern Antarctic Peninsula, driven principally by human-induced climate change, are responsible for the marked regional summer warming that led to the retreat and collapse of the northern Larsen Ice Shelf.”

    And now it’s deja vu all over again as catastrophe looms once more.

    Liked by 3 people

  13. A useful round up of Antarctic alarmism through the years. Thanks Dennis.

    Oldbrew, the NASA study is one of those I linked to in the post. Unlike Shepherd et al, which only appears to have considered recent meteorological additions to the mass balance (snow), Zwally et al considered long term dynamic thickening of the ice sheet from snow accumulation going back as far as the Early Holocene, and certainly the increasing dynamic thickening after the end of the Little Ice Age. Recall also that the 20th century snow accumulation in West Antarctica is unprecedented in the last 300 years according to another study I linked to above.


  14. This goes to the heart of the Shepherd paper I believe and illustrates why the authors have found ‘catastrophic’ thinning of glaciers – because they have dismissed the long term impact of snow accumulation affecting glacier dynamic imbalance:

    “Although most of the AIS surface has changed little in elevation over the past 25 years (Figure 2), there are clear patterns of thinning and thickening in coastal sectors – especially in WAIS and the APIS. Some of these signals have been identified in shorter records (Flament and Remy, 2012; McMillan et al., 2014; Pritchard et al., 2009; Shepherd and Wingham, 2007; Shepherd et al., 2002; Wingham et al., 1998; Zwally et al., 2005) and are now better defined because our time series is long in comparison to the period of snowfall fluctuations, which are typically decadal or less in Antarctica (Shepherd et al., 2012; Wouters et al., 2013). Most of the significant changes are coincident with glaciers and ice streams (Rignot et al., 2011).”

    Contrast this with Zwally et al (2015):

    EA dynamic thickening of 147 Gt a–1 is a continuing response to increased accumulation (>50%) since the early Holocene. Recent accumulation loss of 11 Gt a–1 in EA indicates thickening is not from contemporaneous snowfall increases. Similarly, the WA2 gain is mainly (60 Gt a–1) dynamic thickening. In WA1 and the AP, increased losses of 66+/-16 Gt a–1 from increased dynamic thinning from accelerating glaciers are 50% offset by greater WA snowfall. The decadal increase in dynamic thinning in WA1 and the AP is approximately one-third of the long-term dynamic thickening in EA and WA2, which should buffer additional dynamic thinning for decades.


  15. I don’t twitter, but Mann & gang really need to have their anti-scientific, antidemocratic nonsense highlighted.


  16. I see that Dr. Edwards gave a talk in in the UK the other day entitled Stories of extreme sea level rise-

    that was loaded up the u tube-

    “Published on May 16, 2019
    A Changing Planet seminar given by Dr Tamsin Edwards, Lecturer in Physical Geography at King’s College London and award-winning communicator, and organised by students of the Science and Solutions for a Changing Planet DTP.”

    Liked by 2 people

  17. Kakatoa, thanks. She’s one of the more reasonable climate scientists. Her message is basically that the ice melt apocalypse stories that the media are so fond of are exaggerated.

    Liked by 1 person

  18. I realize that this is not on-topic, but it’s the sort of stuff we confront in the US.


  19. I should add that what I’ve done is probably discouraged here, and if so I will not be offended if you take it down or move it.


  20. No problem John. I must admit that I don’t know a lot about earthworms and climate change! I doubt many other people do either. It strikes me that we may need more moles though. Your linked article comes under the category ‘if bad things happen, it must be due to climate change and when bad things happen, they make climate change worse’.


  21. In the news today, ‘it might be worse than we thought’. According to “structured expert judgement”, Greenland and Antarctica might melt down quicker than we thought and the sea level rise by 2100 might be 2 metres – twice what “expert judgement” says. The BBC has lapped it up of course. Who’s behind this latest piece of bizarre extremist nonsense? Why, Stefan Rahmstorf and the Potsdam Climate Institute of course and a Professor Bamber from the University of Bristol, who is lead author.
    It’s hard to keep up. Alarmist junk ‘science’ gets published in a prestigious journal one day and the next day it’s international news. Relentless climate propaganda aided and abetted by the lame stream media.


  22. @Jaime

    I think my fam are kinda fed up of me ranting at the radio. This particular report by Matt McGrath was one such opportunity for me. Alas, or perhaps thankfully, the disembodied voice on the radio couldn’t hear what I was saying.

    The first obvious point is that a study showing no terrifying flooding/400 million climate refugees would probably have been ignored, or not published. There is a reward for extreme opinions.

    Second: asking experts what they think is the opposite of science according to Feynman and I agree with him. I prefer to look at the record, which requires a major hockey stick to ascend to 2 m by 2100.

    Third: to say Bangladesh will be destroyed shows instantly that the authors know nothing about river deltas.

    Fourth: to say that climate models do not capture the nuance of ice sheet dynamics does not imply that “it’s worse than we thought.”

    Fifth: where is this suggested 5C rise in temps by 2100 supposed to come from?


  23. Apologies for a very long comment. As a (slightly manic) beancounter I like to reconcile data sets. The differing estimates behind the claims of accelerating ice mass loss in Antarctica do not reconcile, nor with sea level rise data.
    The problem of ice loss needs to be looked at in terms of the net of ice losses (e.g. glacier retreat) and ice gains (snow accumulation). Any estimate then needs to be related to other estimates. The Guardian article states

    Separate research published in January found that ice loss from the entire Antarctic continent had increased six-fold since the 1980s, with the biggest losses in the west. The new study indicates West Antarctica has caused 5mm of sea level rise since 1992, consistent with the January study’s findings.

    The paper is Rignot et al 2018 “Four decades of Antarctic Ice Sheet mass balance from 1979–2017“. The abstract states

    The total mass loss increased from 40 ±
    9 Gt/y in 1979–1990 to 50 ± 14 Gt/y in 1989–2000, 166 ± 18 Gt/y
    in 1999–2009, and 252 ± 26 Gt/y in 2009–2017. In 2009–2017,
    the mass loss was dominated by the Amundsen/Bellingshausen
    Sea sectors, in West Antarctica (159 ± 8 Gt/y), Wilkes Land, in
    East Antarctica (51 ± 13 Gt/y), and West and Northeast Peninsula
    (42 ± 5 Gt/y). The contribution to sea-level rise from Antarctica
    averaged 3.6 ± 0.5 mm per decade with a cumulative 14.0 ±
    2.0 mm since 1979, including 6.9 ± 0.6 mm from West Antarctica,
    4.4 ± 0.9 mm from East Antarctica, and 2.5 ± 0.4 mm from the
    Peninsula (i.e., East Antarctica is a major participant in the mass

    Jaime @ 19 May 19 at 7:56 am points to a New Scientist article in January claiming that Antartica ice loss has trebled. The underlying article is from Nature – The IMBIE Team – Mass balance of the Antarctic Ice Sheet from 1992 to 2017. The abstract states

    The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimeters (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992–2017 (5 ± 46 billion tonnes per year) being the least certain.

    The key problem is in the contribution to sea level rise. The Rignot study from 1979-2017 gives 3.6 mm a decade from 1989-2017 about 4.1 mm and from 1999-2017 about 5.6 mm. The IMBIE team estimates over the period 1992-2017 7.9 mm sea level rise, or 3 mm per decade. The Rignot study estimate is over 50% greater than the IMBIE team. Even worse, neither the satellite data for sea level rise from 1992, nor the longer record of tide gauges, show an acceleration in sea level rise. Yet, if Rignot is correct in recent years Antarctic ice loss must now account for around 20% of the sea level rise (satellite record) or >25% (tide gauges) of the sea level rise. What factors have a lesser contribution? It cannot be less thermal expansion, as heat uptake is meant to have increased post 2000, more than offsetting the slowdown in surface temperature rise.
    The secondary element is that Rignot estimates a net loss in mass in East Antarctica whilst the IMBIE estimates it is insignificantly different from zero.


  24. Thanks for the detailed contributions guys. The Con has of course invited one of the authors of this study to write an article on it. I’ve left a comment:

    “Uber alarmism. You basically took the most unrealistic worse case emissions scenario (RCP8.5), used a temperature projection for 2100 near the upper end of the spread of the model projections, then chose to concentrate on the 5% worst case tail end end scenario of extreme sea level rise resulting from that global rise in temperature. You call this “Structured Expert Judgement”. I call it evidence-lite catastrophism.”


  25. Jaime,

    You mention “structured expert judgement”. This is a subject dear to my heart and one day I may write an article on it. In the meantime, I offer the following quote taken from a paper written by Richard Moss and Stephen Schneider (1996) on the various efforts that had thitherto been made to “structure” opinions solicited from experts. In respect of such a structuring study performed by the Environmental Protection Agency, back in 1995, they had this to say:

    “Like the Morgan and Keith study, there was one scientist whose estimate of climate sensitivity was an order of magnitude less than the eight other scientists involved in the EPA climate model elicitation. There was also one glaciologist whose suggested parameters and model probabilities implied a 5 percent chance of a major Antarctic contribution to sea level rise while the other glaciologists provided parameters suggesting the probability to be only 0.5 percent. In both cases, the EPA authors weighted all of the scientists’ opinions equally in calculating the combined distribution, to ensure that the one “contrarian” scientist’s response, which resulted from his fundamentally different view of climate sensitivity, was given full effect. These aggregations were criticized in editorial comments by Keith, 1996, on the grounds that this is an inappropriate procedure when an outlier scientist clearly adheres to a different paradigm than the other scientists interviewed. Titus and Narayanan considered arguments against this approach, but, they argue, to simply ignore, for example, the outlier glaciologist’s opinion because it is a minority view would be to disregard the possible risk of a large rise in sea level from rapid Antarctic disintegration.”

    So my question is this: How did we get from a position back in 1995, when only a “single outlier” glaciologist was predicting major Antarctic contributions to seal level rise, to our current position, where such a prediction has become the mainstream view (at least as far as the media are concerned)? Could it, perhaps, have anything to do with the way that expert opinion has been “structured” over the years? What do you think?


  26. Jaime, I’ve put a comment a comment at the Con expressing my puzzlement that despite their commitment to being unbiased they are publicising this alarmist scaremongering rather than Tamsin’s work, and suggesting they might redress the balance.

    Here’s an interesting slide from Tamsin’s talk on sea level rise (actually from the IPCC), showing that sea level rise was far larger in the past (at the end of the last ice age)

    Liked by 2 people

  27. I have posted an amended version of my comment at 8:18 am with an important postscript. The Rignot et al 2018 paper cited by the Guardian gives similar results to Rignot et al 2011 for the acceleration in Antarctica ice mass loss. Prof Eric Rignot – along with three of the other four authors of the 2011 paper, also contributed to Shepherd et al 2012 – Reconciled Estimate of Ice-Sheet Mass Balance. This set the standard for the time, and was the key article on the subject in IPCC AR5 WG1. Shepherd et al Nov 2012 has the following Table 1.

    Antartica as a whole (AIS) has very little acceleration in ice mass loss from 1992-2011. Rignot et al 2011 have acceleration of 14.5 ± 2 Gt/yr2 for 1993-2010. Rignot et al 2018 states

    The total mass loss increased from 40 ± 9 Gt/y in 1979–1990 to 50 ± 14 Gt/y in 1989–2000, 166 ± 18 Gt/y in 1999–2009, and 252 ± 26 Gt/y in 2009–2017.

    Questions need to asked why, from the same data, such wildly different estimates are obtained. Estimates of accelerating ice mass loss for Antarctica do not accord with the IPCC standard, nor with the lack of acceleration in sea level rise, whether measured by tide gauges or satellites.

    Liked by 1 person

  28. John, I’m not sure what this “structured expert judgement” is but it seems to relate to something you wrote a while back about risk aversion and uncertainty aversion and it does appear to me that they are trying to repackage the Precautionary Principle as some kind of ‘consensus’ expert judgement. It will be interesting to hear what you have to say about SEJ if you do write a post about it. As far as I can see, all they’ve done is take the expert estimates of SLR under RCP8.5 (0.5-0.98m), inserted an uncertainty/risk multiplier because of the lack of really good ice models and come up with a 2m sea level rise in 2100! As somebody at the Con amusingly points out, the mathematical equation for this can be written:

    Risk = guess + ideology x Greta Thunberg

    (though there should be brackets to make it mathematically precise – or maybe not!)


  29. Paul, I’ve yet to view Tamsin’s video as I’m away at the moment with limited download but I’ll play it when I get back. I really do doubt if the Con will invite her to dispel the myths about catastrophic sea level rise. They seem to be on a mission atm to create as much panic about the ‘climate crisis’ as they can.


  30. This seems interesting. In the Con article there is a graph with the caption

    “Reconstructed sea level for the last 2500 years. Note the marked increase in rate since about 1900 that is unprecedented over the whole time period. Robert Kopp/Kopp et al. (2016), Author provided”

    But I’ve looked at the graph in the Kopp et al paper and it says

    “(A) Global sea level (GSL) under prior ML2,1. Note that the model is insensitive to small linear trends in GSL over the Common Era, so the relative heights of the 300–1000 CE and 20th century peaks are not comparable.”

    Am I missing something here or are Bamber and Oppenheimer indulging in some major mis/re-interpretation here?


  31. I believe one of the methods used to evaluate the poorly known, and falling under the umbrella of structured expert judgement is the Delphi Technique whereby experts are asked to pool their estimates (=informed guesses) to arrive at some “best guess”. I first came across this when working for a North American oil company that wished to exploit its in-house knowledge base to estimate its future resources. Later I found it very briefly described as the most simple and most inaccurate method to estimate resources in an area described in a textbook devoted to mineral exploration.

    Rather than seeking out the opinion of the most knowledgeable expert, the method presumably believes in, and exploits, the “wisdom of (informed) crowds. I cannot understand how using such methods can improve estimates of SLR. Such determinations are likely to be dominated by the most forceful, opinionated or senior participant’s opinions (as was my oil company experience).

    At an earlier time, when working for a Provincial Geological survey, we were asked to evaluate possible and probable oil,gas and mineral resources that were to be given up if an area were to be released from.Provincial control to establish a Federal National Park. Here each of us was asked to evaluate the resource base of the strata of which we were supposed to be expert, and that constituted the entire assessment. Who knows if we had each made our own assessment of the entire rock sequence (most of which we had imperfect knowledge) and averaged them, whether that would have been closer to reality. Certainly, in retrospect, huge changes in technology have meant that our estimates could have been gross underestimates.

    Liked by 3 people

  32. Paul, firstly they didn’t show the entire figure, which includes the Marcott, Mann et al temperature reconstructions and estimated SLR. Also, as you point out, they neglected to mention that the pre 1900 estimates were based on low resolution proxy data, whereas after 1900, they used higher resolution Hadcrut 4 instrumental data – hence the peaks are not comparable. They just shoved that graph in the article with little explanation expecting people to believe that SLR accelerated dramatically after 1900.


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