Mer de glacé retreat question

New Topic
This topic has been archived, and won't accept reply postings.
 smithaldo 04 Nov 2021

So I was just wondering….

with the level of the glacier signs at montveners as you go up the steps…

are they where the glacier actually ended as such or just the height it came to looking to where it finished??

 Graeme G 04 Nov 2021
In reply to smithaldo:

Height it came to. Bloody depressing.

OP smithaldo 05 Nov 2021
In reply to Graeme G:

So height and physical presence as such???? I.e the sign would be put effectively where the glacier met the steps???

 cragtyke 05 Nov 2021
In reply to smithaldo:

https://www.ukclimbing.com/articles/features/100_year_time-lapse_of_the_mer...

A previous article here, the old postcard gives you a good idea of the extent of the retreat.

 gravy 05 Nov 2021
In reply to smithaldo:

Yep that's the meaning of the signs, at this height you'd be able to step onto the glacier.

If you think that's shocking, the point where you hit the Glacier Blanc is now over three hours hike from where it was 20 years ago. Last time I went I sunbathed on a rock while I ate my lunch that would have been under 100s of metres of ice the time I went before .

They've redrawn the maps a dozen times to keep pace with the change

Post edited at 18:08
3
 Graeme G 05 Nov 2021
In reply to smithaldo:

First time I visited (c. 2002) we stepped off the cable car and walked a bit down to the glacier to visit the St Bernardo’s in the wee cave. Last time (c. 20016) we walked, and walked, and walked ever downward past the signs. I couldn’t believe how much it had receded in such a short time. Mind you that was the summer they closed Mont Blanc as it was so warm.

Post edited at 19:10
1
 ed34 05 Nov 2021
In reply to smithaldo:

Here's another video showing how the access height has changed. I was last there in 1995, can't believe how it's changed. I also remember when you got on the glacier from the ladders it was reasonably clean, I mean lots of white and blue Ice visible, looking at the video now it seems that it's now just a rock covered mess where you access it!

youtube.com/watch?v=3MG4n2mEdvA&

Post edited at 22:30
In reply to ed34:

Jesus. I visited first in 2005 and remember those steps. I cant quite believe it's gone so far since. Depressing as anything. 

 henwardian 05 Nov 2021
In reply to smithaldo:

Just think of all the new bouldering that will be opened up when it's finally stopped shiftying the rocks about eh?!

3
 oureed 06 Nov 2021

While I agree that glacial retreat in the Alps is depressing, we should be aware that the height markers on the Mer de Glace stairs tell a slightly misleading story. The snout of the glacier is the part that is below the station at the moment and because it slopes away more steeply than the rest, the loss of depth is exaggerated. Someday soon they will stop adding markers altogether because the depth of ice will have stabilized (at 0!)

1
In reply to oureed:

But go further up the valley and the story is not misleading at all. The whole top surface of the glacier there has gone down (vertically downwards) several hundred feet. Obviously at the snout the vertical movements are amplified.

 65 06 Nov 2021
In reply to Graeme G:

Yep. I think it was 1989-90 I first went there and probably 91 when I crossed it. I didn't go back for many years, and did the TMB in 2015. Gobsmacked by the view across from La Flegere at how much the glacier had shrunk from what I'd remembered.

The other one that hit me was the Lower Grindelwald Glacier. We had a walk up towards the Schreckhorn hut two years ago and the glacier snout is a long way up the valley. I have memories from 32-33 years ago of a deep glacier and big seracs hanging out of the U-shaped trough between the Wetterhorn and Eiger, visible from the village.

 Martin Haworth 06 Nov 2021
In reply to gravy:

> Yep that's the meaning of the signs, at this height you'd be able to step onto the glacier.

> If you think that's shocking, the point where you hit the Glacier Blanc is now over three hours hike from where it was 20 years ago. Last time I went I sunbathed on a rock while I ate my lunch that would have been under 100s of metres of ice the time I went before .

> They've redrawn the maps a dozen times to keep pace with the change

I think you must be mistaken, do you really mean the Glacier Blanc in the Ecrins? The path has been diverted but the glacier is only about 100m shorter than 20 years ago, and a few meters lower.

 wercat 06 Nov 2021
In reply to 65:

in 1989-90 you could approach the glacier at the level of the river in the valley.  To go ice climbing on the glacier you had to go up on the Eiger side of it and approach from the side, high up where you'd find the entry to the Eisgrotto.  By 1995 the boulder down to valley level was completely exposed and there were ladders up to the cafe on the top where you could go still go on to the foot of the glacier, several hundred feet higher than the ice was in 1989.  Shocking, but as the summit of the Eiger was bare ground in 1990, perhaps understandable

Post edited at 14:14
 Babika 06 Nov 2021
In reply to ed34:

Wow. 

That video is very sad and makes me feel powerless

 flash635 06 Nov 2021
In reply to smithaldo:

Global glacier retreat started around 1850, well before any anthropogenic influence was of significance.  It is also almost certain that the glacier level was much, much higher (as was the treeline) during the Roman Warm Period - Roman (and Bronze Age) artefacts are being discovered on mountain passes that until recently were under permanent snow cover.

In 1854 the Mer de Glace was actually in the Chamonix valley floor - there is photographic evidence of this (see Nussbaumer, 2007).  It will not make me popular to point it out, but the fastest rate of retreat of the Mer de Glace was actually in the 19th century, between about 1860 and 1880 (see Nussbaumer & Zumbahl, 2011).

Alpine glacier retreat commenced far too early to have been caused by anthropogenic GHGs.  The retreat since the Little Ice Age ended (probably slightly earlier than 1850) has been in three waves with a periodicity of about 60-70 years.  This periodicity is also seen in the sea level rise (which also starts very early - about 1850 - and is linear to date) (Jevrejeva 2014).

If you don't believe me, read the references and do your own due diligence.  I am not going to get sucked into a flame war with people calling me a denier.  Just bear in mind that I have actually researched and published a conference paper on this topic at a recent Geological Society of London conference on climate change.

6
In reply to flash635:

Please could you give me the reference to your paper.

Ps. The industrial revolution was fueled by coal, and that really started to take off in ca. 1800 to 1820. In fact most things anthropogenic really started to take off (many exponentially) ca 1820. 

 65 06 Nov 2021
In reply to flash635:

> Global glacier retreat started around 1850, well before any anthropogenic influence was of significance. 

I'm not sure about this. This is c.150 years after the beginning of mass industrialisation. No cars and Ryanair flights perhaps, but a huge shift in what humans were expelling into the atmosphere. Someone more learned than I can elaborate.

 65 06 Nov 2021
In reply to John Stainforth:

You beat me to it.

 flash635 06 Nov 2021
In reply to John Stainforth:

John, it was a Zoom conference and only abstracts were provided.  Not sure if they are still up.  My final title and complete abstract are given below.

Regarding "industrial revolution" and anthropogenic influence on climate most people are (sadly) woefully misinformed on what IPCC AR6 and the CMIP6 model comparison study forcings actually show.  There are no warming forcings, only cooling ones, prior to about 1900-1910 in the AR6 climate model inputs.  And the anthropogenic forcings post 1950s are 3x larger than the early 20th century ones.  Which is a bit of a problem as the warming in the early 20th century is not 3x smaller than the late 20th century, its only about 1.4x smaller ie, a factor of >2 discrepancy.  And of course the IPCC AR6 forcings preclude any possibility of sea level rise or glacial retreat prior to about 1900-1910.  Which is a bit odd, because the physical evidence of retreat is very clear and unambiguous in both the sea level and glacier length data.

My Final abstract for Geol. Soc. Climate Change conference, May 2021:

Comparison of warming onset timing and rates post-LIA in Glacial, Sea Level and HadCRUT4 surface temperature datasets - Ashley Francis, FRAS, MI Soil Sci.

Surface temperature observations are used to construct global temperature averages. The different versions available are based on the same underlying station data. HadCRUT4 is selected as it has (a) the most stable change log with time and (b) is not spatially interpolated. For consistency with CMIP5 climate models, output is used up to 2011.


HadCRUT4 time series can be roughly characterised into four time-intervals defined as general trends. These are: neutral or slightly cooling 1852 - 1910; warming 1910 - 1945; neutral or slightly cooling 1945 - 1980 and stronger warming 1980 - 2011. The onset of modern warming is 1900 - 1910. The ratio of the warming rates of the two periods is 1.4x.


CMIP5 (and CMIP6) climate models respond only to the imposed prior forcing curves as a function of time that are used as inputs. The net forcing follows the same trend pattern described above for HadCRUT4. Like HadCRUT4 the climate model forcing input and resultant temperature output also show the onset of warming from about 1900 - 1910. The ratio of average net forcing 1975-2005 to 1910-1945 shows the later period is modelled with 3.7x the net forcing of the earlier period and this is also evident in the resultant climate model temperature output which has a ratio of 3.4x. There is therefore a discrepancy factor of at least two between modelled and observed warming rates. In addition, RCP8.5 forward model residuals are clearly structured and periodic with a period about 70 years.


Two other direct physical measurements are sensitive to temperature: global sea level (SL) and glacier length (GL) data. Using the SL dataset of Jevrejeva (2014), the ratio of the SL rate for the two C20th warming periods is 1.03x, consistent (but damped) with HadCRUT4 observations but not with climate models. The onset of the linear SL trend commences in 1856, but a cross-correlation of the rate of change of the SL data and HadCRUT4 (30 year slope, 100 year window) gives a cross-correlation peak of R=0.91 with a lag of about 16 years. Adjusting for this lag, the observed onset of SL rise would require the onset of a temperature trend no later than about 1840. This finding contradicts both HadCRUT4 and the climate model results.


Glacier data is based on the comprehensive and exhaustive dataset of Leclercq et al (2014) and the temperature reconstruction of Leclercq and Oerlemans (2011). The L&O2011 temperature reconstruction from GL data shows glacier response to a warming trend to have started no later than 1850 and potentially as early as 1833. The ratio of the GL derived warming rates for the two 20th century periods is 1.4x, the same as the temperature observations, but also contradicting the climate model results. A subset of the 18 longest glacier records is used for analysis and modelling. Three periods of retreat are clearly identified in the 19th century and two in the 20th century. The rates of retreat are all comparable, the post 1980s retreat is statistically slightly slower than the previous periods.


Forward modelling of the long record glacier data using HadCRUT4, RCP8.5, CMIP6 and a trivial trend+sinewave model shows that the trivial model performs best with a mean error of 64 m compared to the other series with mean errors from 134 - 152 m. This model also has a good fit to the glacial retreat and sea levels trends back to the early 19th Century.

3
 Martin Haworth 06 Nov 2021
In reply to Martin Haworth: My 100m might be an under estimation based on my own observations. The glacier blanc retreated significantly between 1985 and 2010 in total about 500m over the 25 years, but it actually grew a couple of years between 2010 and 2020. I have a photo from 2021 and a comparison from 2002(I will put them on two posts because of file size).

 Martin Haworth 06 Nov 2021
In reply to Martin Haworth:

2021


 Martin Haworth 06 Nov 2021
In reply to Martin Haworth:

2002


 rif 06 Nov 2021
In reply to thread:

Just had a quick look in Web of Science. Here's a relevant and recent (2020) academic paper that is open access:

https://tc.copernicus.org/articles/14/3979/2020/

It's about glacialogical modelling of changes in the Mer de Glace in the last few decades. The observed reduction in ice surface elevation at several locations, and the observed retreat of the snout, are in Figures 5b and 6. The model fits the observations well so they project it to 2050, with pretty scary results (Figure 7). The main driver of the shrinkage seems to be reduced accumulation in the upper (Geant) glacier.

 mbh 06 Nov 2021
In reply to flash635:

Was it this conference you published at?

https://bolin.su.se/about-us/events/geological-society-climate-change-in-th... 

It's on Youtube, but I can't see your talk.

And are you the ThinkingScientist that posted on this rather odd site?

https://wattsupwiththat.com/2020/10/26/study-suggests-no-more-co2-warming/?... 

Same references, same typo in  one of the reference authors as in your previous post, so I guess you probably are.

You say:

>There is therefore a discrepancy factor of at least two between modelled and observed warming rates.

but when I look at SPM.1, the first figure of the Summary for Policy Makers of the IPCC's AR6 WG1 report (The Physical Science Basis),

https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM_final....

there appears to be remarkable agreement between warming modelled using CMIP6 models, where anthropogenic forcings are included, and observed warming, from 1850 onwards.

What am I misunderstanding?

 pneame 06 Nov 2021
In reply to Martin Haworth:

> actually grew a couple of years between 2010 and 2020.

I'm not a glaciologist, but my impression has been (and I think this is one glaciological model) that a "growth spurt" is a sure sign of a subsequent rapid retreat as the growth spurt results from sub-glacial liquid increasing flow and acting as a lubricant. Thus ice moves, down, into a warmer zone, melts and this accelerates the flow rate overall resulting in overall reduction of ice mass. It is, of course, "complicated"!

Added: It is quite depressing when I think of when I first went to the alps in 1973 and we used to play on the Bossons. 

Post edited at 20:39
 flash635 06 Nov 2021
In reply to mbh:

You are not misunderstanding, you simply have not looked at the detail.  The problem with the climate models is they run 2 to 2.5 times too hot. They are tuned to the post 1950s warming, but they underpredict warming in the early part of the 20th century. If they fit one warming spurt but mispredict the other by a significant margin then they are incomplete. Its not the only evidence they are not correct and likely exaggerate the impact of GHGs by at least a factor of 2.

However the main point of my original post here is that the CMIP6 forcings do not show warming until around 1900 to 1910. Glacial retreat and Sea level rise starts 1850, too early to be anthropogenic according to the climate models.  Note that global temperatures also don't show warming from 1850, but from about 1900 to 1910. So why do sea level rise and glacial retreat start much earlier?

Regarding climate models, Steve Koonin's book Unsettled is very readable and written by a top flite physicist, which will take people through some of the concerns over models and how unsettled the science really is.

9
 flash635 06 Nov 2021
In reply to mbh:

Last answer from phone, at computer now.

Yes, that's the conference. Only the keynotes were recorded, I assume.

Regarding IPCC AR6 WG1 Fig1, we would be looking at the right hand panel.  The problems are (a) that panel shows no warming in temps or climate models until about 1910 and (b) there is a significant warming period 1910 - 1945 which the models get both the timing and the rate wrong.  The ratio of the warming period post-1950s compared to the 1910-1945 period is a ratio of 1.4x.  But the models have a rate difference of around 3.4x between the two periods.

The reason is easy to explain - the models only have anthropogenic GHGs as a warming mechanism and nothing else in the models can warm, natural impacts can only cool (which is basically volcanoes).  Because the model forcings in CMIP6 (and in the earlier CMIP5) are 3.6x larger post 1950s than the first part of the 20th century, that's what the models come out with.  The problem is that ALL the physically observed datasets (temps, sea level and glacial retreat) show the ratio to be about 1.4x (actually even less for sea level).  So the climate models only fit post-1950s warming (to which they are tuned) and get the rate wrong by a factor of at least 2x in the early 20th century warming.  Its a big error if you think you can then rely on a climate model to predict the temperature 80 years in the future (with unknown forcings) when you cannot predict correctly 80 years back in the past (with known forcings).

This is an aside though - that same IPCC AR6 Fig 1 claealry shows no warming in temps or models prior to 1910 - its completely flat.  So why was the Mer de Glace retreating at its fastest recorded rate 1860-1880 if AR6 temps and models say there is no warming until 1910?  Is also true of global glacier records.  The onset of glacial retreat and sea level rise is much too early for any  anthropogenic GHG factors to have impacted it.  And even the warming (and retreat) 1910 - 1945 is too fast to be explained by anthropogenic GHGs if you accept the climate model fit post-1950s.

8
 Martin Haworth 06 Nov 2021
In reply to pneame:

> I'm not a glaciologist, but my impression has been (and I think this is one glaciological model) that a "growth spurt" is a sure sign of a subsequent rapid retreat as the growth spurt results from sub-glacial liquid increasing flow and acting as a lubricant. Thus ice moves, down, into a warmer zone, melts and this accelerates the flow rate overall resulting in overall reduction of ice mass. It is, of course, "complicated"!

I think it was the volume of the glacier that increased, probably just a couple of years of high snowfall in the area, but as you say it is complicated.

> Added: It is quite depressing when I think of when I first went to the alps in 1973 and we used to play on the Bossons. 

I first went in the early 1980’s and walking up to play on the Boissons was my first time on a glacier.

 mutt 08 Nov 2021
In reply to flash635:

What is your point? This all sounds like climate change denial.  That really is quite old fashioned. 

Do you dispute anthropogenic warming?

And do you dispute the ability of models of the last and next 50years to show that warmer temperatures do actually melt glaciers? 

I don't really see that climate models need to necessarily produce accurate glacier heights? Their role is to predict atmospherics and ocean contributions. Glacier retreat does not drive either of those so why would they try and model them. We have numerous other more direct measurements to work with.

And I'd have though that it was self evident that glaciers melt under any form of warming and anthropogenic warming is not at all contentious.

1
 inboard 08 Nov 2021
In reply to flash635:

Was your poster presentation peer reviewed at all?

While I don’t challenge the timing of Chamonix glaciers retreating in the 19th century, I am sceptical of some of your other statements.

I’m not a climate scientist (though I do work in a related field), but I know Steve Koonin’s book has attracted very critical reviews from respected reviewers who are climate scientists, and I also note that you appear previously to have aligned yourself with Net Zero Watch (an organisation which includes Nigel Lawson and Andrew Mountford on the board, is funded by the Global Warming Policy Foundation, and appears to exist in order to prolong notions that climate science is much less settled than it is as a diversionary tactic aiming to slow responses to climate change), as a co-signatory of a letter to Geol Soc London about their corporate stance on climate change. As such, I’m sceptical about your motivations in preparing your poster.

1
 flash635 08 Nov 2021
In reply to mutt:

And very quickly a commenter lowers the tone with accusations of climate denier, thus playing the man and not the ball. Very predictable.

The rest pf your comments are insubstantial and trivial and add nothing to the discussion. Perhaps you would like to provide a criticism  of a point I actually made rather than coat racking your own prejudices into the thread.

4
In reply to flash635:

mutt and inboard have asked you some questions that are not trivial. 

1
 flash635 08 Nov 2021
In reply to inboard:

Thank you for your comments.  With regard to your question as to whether my poster presentation was peer reviewed the answer is yes but only in as far as any poster presentation ever is which is clearly limited.  It was a "poster" in the virtual sense (it was on Zoom) but I had to defend it against questions from the Geol. Soc Fellows attending the conference.  I think it would be fair to say that most of them were hostile to my views, given the questions I received and the other presentations I saw at the conference.  I think I defended my points without anyone being able to offer any substantial evidence to the contrary.

With regard to Steve Koonin's book, regrettably his views will be treated with prejudice by those who don't agree with him.  Unfortunately this is the nature of climate science today.  Instead of politely disagreeing, motive is assigned and critics resort to ad homs.  I came across Koonin when he chaired the APS seminar on climate science.  That was an on-the-record debate between 3 pro- and 3 sceptic climate scientists, all high flyers with impeccable credentials.  Koonin chaired the meeting.  The transcript (500+ pages) is available on line (google is your friend) and is probably the most accurate and honest statement of the true state of climate science on record.  As regards Koonin, in my opinion he is the closest we have to an heir to Feynman and his credentials are impeccable.   He studied physics under Feynman at Caltech.  He wrote some of the earliest texts on computer modelling.   He was an Undersecretary Science Advisor in the Obama Administration and he is a life long Democrat (as far as I can tell).  My advice therefore is that of the motto of the Royal Society - Nullius in Verba.  Take no-one's word for it.  Read his book.  If you disagree, fine.  We are all free to make up our own minds.  If you don't want him to benefit from purchasing it buy a second hand copy.

I have to politely disagree with what I consider to be your mis-characterisation of the GWPF and Net Zero Watch.  The claim they are trying to prolong dissent is untrue.  It would appear that pointing out that the Net Zero policies being currently debated and proposed will be both ruinously expensive and ineffective is insufficient to get you labelled along with the deniers.  Whatever happened to commonsense?

Yes, I was a co-signatory to the letter to the Geol. Soc.  I strongly disagree that it was a "corporate stance" and to my mind that is a propaganda statement put about by people who disagree but are too cowardly to debate in public in case they lose.  I know a number of the signatories personally, none of them (including myself) signed except in a personal capacity and many of them are retired.  Remember that the Fellows of the Geol. Soc., especially those who have trained in and practised as Geologists for over 50 years know as much about paleo-climate as anyone.  Science is not consensus, its politics.

My motivation in preparing my poster was to point out a number of glaring inconsistencies in climate science.  If you would like me to share the poster slides with you or discuss it I would be very happy to do so, although I am not sure how that could be achieved through this thread.  I am very happy to defend my findings to valid criticism, but I am not prepared to subject myself to a series of ill-considered ad hominen attacks.  As a scientist trained as a geophysicist with 37 years of specialisation in forward and inverse modelling as well as geostatistics I consider that I would be not fulfilling my responsibilities if I did not point out serious issues that need to be answered.  I have written to my MP on these matters.  He is unsupportive, as is his prerogative, I will continue to put my case.  I have also taken part in a public debate, hosted by the Cumbria section of the Geol. Soc. against an eminent Physics Professor.  I think he almost certainly lost, but then I would say that wouldn't I?

3
 mbh 08 Nov 2021
In reply to flash635:

What marks you in particular out as a fruitcake to be ignored is your obsession with one tiny issue within the whole mega-subject of climate change. It's complicated, right so if glaciers melt at this or that rate before or after anthropogenic emissions picked up, don't you think you should at least put that in the context of the plethora of other evidence that suggests that anthropogenic activity might have something to do with the various signals of climate change that we are now witnessing, rather than simply arrow solely on your one point. 

And, please answer the questions you have been asked: are you the TruthfulScientist on that site of weirdos, and was your 'published' article/presentation/whatever it was peer reviewed?

5
 flash635 08 Nov 2021
In reply to John Stainforth:

Mutt is making ad hom. comments - I have no intention of getting in a flame war and replied accordingly.  If people are not prepared to be polite and civil and avoid accusations, don't bother.  One of the problems with climate science on a public forum is the number of people with huge prejudices who basically know very little and simply wade in with ad homs.  Play the ball and not the man I will reply as best I can.  

Inboard has made valid and interesting comments to which I have replied in full and, I hope, respectfully disagreeing.

FYI, I don't sit at home waiting and monitoring this thread continuously for 2 days just in case someone responds.  I do have a life and it includes climbing.

5
 flash635 08 Nov 2021
In reply to mbh:

And here we go again!  "fruitcake", "obsession", "site of weirdos".

If the best you can muster is a series of rude ad hominens then I fail to see why you would even expect me to reply.  If you want to learn something, ask a relevant question.

And ask it nicely.

4
 blurty 09 Nov 2021
In reply to smithaldo:

I started to think about all this when I went to the Alpine museum in Chamonix, and there are oil paintings from the 1700s showing the glaciers reaching the valley floor. The models, which we are rightly so concerned about show AGW starting around the turn of the last century, but by then the glaciers had already retreated up to the balcony.

Something doesn't add up for sure

Incidentally I had a conversation with a PHD student who has specialised in glaciers. He thought that glaciers are influenced more by temperature than accumulation. I.e. a few bumper snow years in the vallee blanche aren't going to help much. It's more like a rising tree line, as average temperature rises at any given altitude.

Post edited at 10:32
 LakesWinter 09 Nov 2021
In reply to blurty:

Well its more that GHGs started to build up properly in the 19th Century and also in the 19thC NW Europe and possibly the wider world were coming out of the naturally forced Little Ice Age, which itself followed a slightly warmer period in Medieval times.

The more rapid ice loss began in the 1910/20s in response to greenhouse gas forcing, there was then a period of slight glacial growth 1950-80 approximately which is likely linked to cooling associated with high levels of sulphur dioxide in the atmosphere from industrial processes. When industries in many places cleaned themselves up to stop the sulphur dioxide etc causing acid rain then the cooling effect of these aerosols was lost.

If you link the removal of the cooling aerosols to the ever increasing CO2 and methane forcing to the natural forcing of a positive North Atlantic Oscillation in the late 80s and 90s then this explains the rapid ice loss since around 1985

 flash635 09 Nov 2021
In reply to LakesWinter:

You said "Well its more that GHGs started to build up properly in the 19th Century..."

The IPCC science used for climate models does not say that, although it is a widely believed meme.  According to the IPCC AR6 CMIP6 model forcings, anthropogenic GHG effects in the 19th century are effectively zero.    The only factors of any significance assumed to be operating are natural cooling from volcanos.  If you follow the link given by mbh upthread:

https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM_final.... 

and look at the right hand panel of Figure 1 it is very clear that both the temps and the climate model mean are flat and show no warming prior to about 1910.  Yet from 1850 to 1900 global glaciers were in retreat and sea level rising at statistically indistinguishable rates than those observed in the early or late 20th century.

Your further comment saying "The more rapid ice loss began in the 1910/20s in response to greenhouse gas forcing..." is also not what the IPCC CMIP6 forcings or models really show.  Again, it is widely believed by the general public but actually the science does not say what people think it says.  The IPCC really only claims warming post-1950s is largely anthropogenic.

To expand on that point further, the model forcings assumed due to anthopogenic GHGs (aGHG) in the post-1950s period are approximately 3.6x larger than the assumed aGHG forcings in the period 1910 - 1945.  And yet the warming rate for the period 1975-2010 (HadCRUT4) is statistically indistinguishable from the warming observed in the period 1910-1945.  This is why in the Fig 1 in AR6 the models skim through at a much slower warming rate in the earlier period than the match (achieved by tuning to make it fit) in the later period.  The model mismatch, represented as a ratio of the two periods of warming is greater than a factor of 2.

It may also surprise people to learn that in the model forcings used by the IPCC in the CMIP6 climate models there are no natural factors of any significance that can cause warming.  The only natural factor of any significance included in the models is cooling via volcanoes.  The only warming factors present in the model forcings are all anthropogenic.  If you think the IPCC modelling is correct, how were global glaciers in retreat and sea level rising in the 19th century?

Finally, LakesWinter mentions the AMO.  Some climate scientists now disown the AMO, but I think some form of internal ocean variability is likely an important factor.  Subtracting the climate model response from observed temps allows us to inspect the residuals, a standard test for forward modelling in geophysics (which is what this is).  If the climate models capture the essential features of warming over the period we would expect the residuals to be trendless and unstructured and only punctuated by short period (2-5 year) features such as El Nino/La Nina which they cannot simulate.  In fact we find the residuals are structured and contain a significant quasi-periodic signal with a period of the order of 60 - 70 years.

In my poster presentation to the Geol. Soc. I showed some glacier forward modelling to demonstrate how a trivial constant linear trend model + sine wave of period about 70 years is a much better fit to glacial retreat data (long records only, back to at least 1800) than any of the climate model inputs or outputs.  It is a significantly better fit to glacier retreat data through the 20th century AND it can fit the 19th century warming pulse.

Post edited at 11:53
3
 flash635 09 Nov 2021
In reply to blurty:

Your understanding of glacier response from your PhD student corresponds with my understanding having read a significant body of literature on post Little Ice Age retreat of glaciers and the associated forward and inverse modelling.  The influence of temps far outweighs any accumulation effects.

Your description of the treeline analogy is also accurate.

2
 LakesWinter 09 Nov 2021
In reply to flash635:

The more rapid ice loss in the Alps did begin in the early 20th century, did plateau or even turn into growth 1950-80 and did show rapid retreat after that. This is consistently observed through glacier measurements throughout the Alps. The last maximum of the "little ice age" was around 1890. 

I know the idea of the little ice age is disputed - not getting into that now as it will confuse the debate

 flash635 09 Nov 2021
In reply to flash635:

Its quite funny to observe that the post by blurty gets an up vote (it deserves more) but my post in reply which says I agree with blurty is immediately downvoted!

Hands up which one is the playground child with their fingers in their ears going "Lalalala I can't hear you" whenever I post?

LOL.

 ebdon 09 Nov 2021
In reply to flash635:

What am I missing here? Surely Little ice age ends, glaciers retreat, global temps get a bit cooler again early mid 20th century, glaciers grow a bit. AGW happens mid late 20th century, global temps massively increase at a previously unseen rate throughout the geological record and glaciers shrink again.

Post edited at 12:58
1
 LakesWinter 09 Nov 2021

> To expand on that point further, the model forcings assumed due to anthopogenic GHGs (aGHG) in the post-1950s period are approximately 3.6x larger than the assumed aGHG forcings in the period 1910 - 1945.  And yet the warming rate for the period 1975-2010 (HadCRUT4) is statistically indistinguishable from the warming observed in the period 1910-1945.  This is why in the Fig 1 in AR6 the models skim through at a much slower warming rate in the earlier period than the match (achieved by tuning to make it fit) in the later period.  The model mismatch, represented as a ratio of the two periods of warming is greater than a factor of 2.

You've cherry picked your time points there to split the period where aerosol pollution was causing global dimming. This has confused your averages so they fit your point. Its not really good data use imho.

  If you think the IPCC modelling is correct, how were global glaciers in retreat and sea level rising in the 19th century?

Natural forcings on many interacting timescales cause natural variablility in climate. Anthropogenic GHG emissions are another forcing, its just that the current anthropogenic forcing is so large it is overriding or making a far greater contribution to what is observed than natural forcing mechanisms.

1
 flash635 09 Nov 2021
In reply to LakesWinter:

Thank you for your reply.  I largely agree with your first two sentences.

However I do not agree with your third sentence "The last maximum of the "little ice age" was around 1890".  That is directly contradicted by results shown in Nussbaumer and Zumbuhl (2011) and also in the global temperature reconstruction from glacier data published by Leclercq and Oerlemans (2011).  The latter states "Our reconstruction shows a fairly constant global mean temperature from 1600-1830.  From 1830 until 1940 temperatures continuously increased....From 1940 to 1970 there is a temporal decrease of global mean temperature.  After 1970 temperature is increasing...".  The rate of warming post-1970s, according to AR6 climate modelling, should be over 3x faster than the rate of warming observed in the period 1910-1945.  But it isn't in L&O2011, its only 1.4x, a factor of >2x mismatch.

Finally the sea level reconstruction of Jevrejeva (2014) also confirms that sea level was rising on a pretty much linear rate curve (with a quasi-periodic signal of about 60-70 years superimposed) from about 1860.  Sea level rise lags temperature by about 17 or 18 years, so that would place the onset of warming about 1845 or so for that data set.  And the ratio of the rate of sea level rise post 1970s compared to 1910-1945 is even less than 1.4x (about 1.03x, but the lag effectively truncates the series so its probably comparable to the 1.4x seen in glacier reconstructions and HadCRUT4 temps).

 flash635 09 Nov 2021
In reply to LakesWinter:

You said "You've cherry picked your time points..."

Not true.  I have chosen two (equal length) 35 year periods which are the peak warming in the two periods.  Using the period up to 2010 is required for any comparisons to be made to AR5 models (which is where I started this work) because observed AR5 forcings end in 2011.  My choice of periods are marked out on the following graph of HadCRUT4:

https://woodfortrees.org/plot/hadcrut4gl/plot/hadcrut4gl/from:1910/to:1945/...

On your second point about natural variability note that in the IPCC models there are no natural forcings of any significance that can cause warming on scales of decades to a century or two.  The only significant natural forcings are volcanoes which are short lived cooling pulses.  To get a cooling trend you have to have a coherent sequence of sustained volcanic eruptions.  But natural warming trends on the scale of decades to a century or two are impossible in the IPCC climate model world.

I don't disagree with you about the principal of natural variation per se, I am simply pointing out it is excluded in IPCC modelling (other than cooling from volcanoes).

 flash635 09 Nov 2021
In reply to ebdon:

Yes, in broad brush terms thats ok, but not in detail.

Glaciers were retreating and sea level rising at some 60 - 80 years earlier than is compatible with IPCC AR6 climate models.  That's a very large discrepancy.  As an aside, while people are "sad" etc about alpine glacier retreat (me included, they are amazing natural features) it is worth noting that for the majority of the holocene period and almost certainly through the Bronze age and Roman warm periods the alps were largely ice free, or at least with a substantially higher ice line and tree line.

My second point is more technical, but the rate of warming for the late 20th century versus the early 20th century is modelled to be about 3x faster.  But the actual observations of sea level, temperature and glacial retreat data put the ratio at about 1.4x (actually even less for sea level).  That a >2x discrepancy in warming rates between climate models and observational data.

1
 flash635 09 Nov 2021

Here's a reading comprehension test.  The following is lifted directly from the AR5 Summary for Policy Makers.  It's verbatim, the numbers in [brackets] are the error bars:

"It is very likely that the mean rate of global averaged sea level rise was 1.7 [1.5 to 1.9] mm per yr between 1901 and 2010, 2.0 [1.7 to 2.3] mm per yr between 1971 and 2010, and 3.2 [2.8 to 3.6] mm per yr between 1993 and 2010. Tide-gauge and satellite altimeter data are consistent regarding the higher rate of the latter period. It is likely that similarly high rates occurred between 1920 and 1950"

You can use the upvote or downvote buttons to agree/disagree with the following statement:

The rate of sea level rise accelerated during the 20th Century

If you agree up-vote it, if you disagree down-vote it.


New Topic
This topic has been archived, and won't accept reply postings.
Loading Notifications...