Bishop Hill Leo Hickman on peace talks
Jun 21, 2011 Climate: other Leo Hickman in the Guardian muses about the possibility of peace talks to end the climate wars. Yours truly is mentioned:
I admit that I sometimes find it hard to detect the signal from all the noise when observing climate sceptics, but the most positive contribution the more moderate climate sceptics (or "luke-warmers", as they are sometimes described) such as McIntyre and Andrew Montford have brought to the debate is their dogged insistence that climate science must be transparent, open, fair and free from influence. I don't think anyone could argue that this is not a worthy goal and, even if you disagree with their motivations, tone and methodologies, we will come to thank climate sceptics in years to come for forcing these obvious improvements. So, would a "meeting of the moderate minds" within this debate be productive?
Bishop Hill
I'm in discussions about a formal response to Leo Hickman's suggestion. Watch this space.
Reader Comments (233)
Stephen Richards
Rubbish.
Explain your reading of my earlier comments in enough detail to demonstrate that you have understood what was said. Re post politely and I will respond.
Rob B @ Jun 22, 2011 at 2:59 AM
The current temperature is not varying as it has over the last several thousand years.
I posted a lengthy comment on the 'Reliable sources' thread at Jun 21, 2011 at 12:26 PM
BBD, I am sure you must have been one of my science lecturers way back in the past. If you were not, you are reacting in an eerily similar fashion to a really abrupt and grumpy lecturer I once suffered; it's not a good look. I hate challenging you, as I usually respect and enjoy your contributions to the discussion here, whatever the topic, but you are not doing yourself any favours when you employ such a hectoring tone. As they say in the military, over to you.
Alexander K
Amongst other things, Stephen Richards said:
I do not appreciate his tone and let him know it. And that's fair enough.
Pity about these responses. I think you should have taken (still should take) him up on this. We should have nothing to fear from open debate and should never be the ones to turn it down.
I wonder if in the middle of all this debate, Leo Hickman might like to investigate Mann's sea level paper a little closer. Kemp et al 2011 makes use of the Tiljander data which Mann used three years ago.
Tiljander herself said then that Mann's use of it was wrong (upside down) and yet it re-appears in this paper (still upside down).
"Transparent, open, fair and free fron influence", I think you said, Leo.
Have you got room in there for 'honest'?
BBD
Read my post again. My understanding was that you agreed with the KT argument to transpose the 'NUL HYPOTHESES'.
My post explained why no scientist would put that proposition on the table. If I misunderstood then either one of us can't write clear english or one of us can't read clear english.
SR
Or one of us is being deliberately obtuse about what it was that KT actually said.
Mr Hickman,
Thank you for your response. It is my belief that you were sincere.
You offered, as a starting point, a list of things in which sceptics and those supporting the consensus could find common ground. As you indicate, you are welcome to changes to that list. It is my view that many of the items in the list, while remaining superficially idealised environmental endpoints, are either (a) not a realistic representation of the structure of the world around us, including the humans that live in it, or (b) a source of great contention as to how to achieve these objectives, even if they were shared.
And there are many other desirables from the sceptics' side, which are not present on the list as well.
For instance, 'reducing local pollution', 'reducing asthma incidence', 'reducing environmental mercury' are not acceptable end-targets, as long as they are mere proxies for CO2 control. These are objectives that can well stand on their own legs. The same is true of energy issues as well.
What would a different list look like? I'll start with your list
Unimpeachable, transparent, uncorrupted science
-----------------------------------------------------------------
Advocacy for open data availability in climate science, if requested and where possible, even otherwise.
A call to exclusion of pressure group literature from IPCC assessments
Critical examination of issues thrown up Climategate
A shift in the moderation policies - only abusive, disruptive commenters be restricted
The beginning of investigation into the issues of 'climate money' (and I don't mean scientists' funding here) and science-advocacy in environmental and the climate fields
These prerequisites, as they are approached or fulfilled, would then lay a basic starting point to approach the items on your list.
SR
Might I politely suggest you read this?
SR
And this.
"we will come to thank climate sceptics in years to come for forcing these obvious improvements."
What a smug little [snip] The annointed blessing the beggars for having minded them to be a little more modest. God - when I have the misfortune to meet people like this, I just want to walk away. Life's too short to waste time with the.
Bish....Bish.....teacher....teacher!
How come I got snipped last night for just calling Leo dimwitted and deceitful - and Imran gets away with this much more satisfying epithet?
Hickman's article misses the point. This is not just a political dispute that can be solved by splitting differences. Fundamentally it is a quest for scientific truth in an extremely important area of applied science. The self-appointed "climatology" establishment has grown lazy and fat on directed funding which gave them the "right" conclusions and told them to find evidence for it, standing normal scientific practice on its head. Till those fundamental scientific mistakes are corrected there is no point in getting together around the campfire to sing kumbaya.
"How come I got snipped last night for just calling Leo dimwitted and deceitful - and Imran gets away with this much more satisfying epithet?"
Jun 22, 2011 at 3:29 PM |Foxgoose
Probably because Bish is now busy with his real job but it does not mean your thoughts were wrong..just that we rise above the Gardianista! ;-) Chill Foxy!
BBD
Your previous post describing the Schnidejoch area backs up that it has been getting hotter and colder routinely over the last few thousand years.
http://www.giub.unibe.ch/klimet/docs/climdyn_2007_grosjean_et_al.pdf
The authors nicely show it with their non hockey stick graph C for glacial advances and retreats and the description of how the pass appears to have been used during the warmer periods.
Rob B
Grosjean et al. shows the degree of variability in melt at the Schnidejoch ice field. It shows fluctuations. In 2003 the melt revealed Neolithic remains protected by the ice for 5ky. It's evidence for extremely unusual melting not previously seen since somewhat after the Holocene Thermal Maximum ca 5kya.
This is clearly stated in the abstract as a key finding. Why do you ignore it?
It's like dealing with lawyers.
I once met the other side half way simply to move on, and they then moved the goalposts.
When I objected they ran to the judge, who suggested that I met them... halfway to their new position.
Despite being 100% in the right, and 'winning', I ended up 75% worse off than deserved.
Hard to see how such issues are serving our kids' futures when treated like a combo between a Marrakesh market trade deal and negotiating with a 4 year old holding her breath 'til she turns blue.
~"thank sceptics...for forcing these obvious improvements", including transparency.
Hickman has just conceded the main component of the case against Climate Science's method of doing its "science". So there's no need for further engagement. But, no doubt, little does he know, and little will he admit.
BBD
Which does not seem, to me at any rate, to require much in the way of interpretation.What Trenberth said, according to www.climatesciencewatch.org here (http://tinyurl.com/67mh8x5) -- and I've tried to avoid using the obvious sceptic sites as my source -- was:
Who says that global warming is 'unequivocal' and is 'very likely' due to human influence? Inter alia Kevin Trenberth in his various capacities within the IPCC and his responsibilities for the compilation and publishing of the 2007 IPCC report.
So his contention that it is time to "reverse" the null hypothesis is already tainted.
Until (and I come back to my favourite hobby-horse) there is something other than assertion and computer modelling I doubt that 'Anthropogenic Global Warming' can even at this stage be considered as a hypothesis. It is still the situation that the climate scientists have not as yet provided any single coherent hypothesis on the subject that is falsifiable. If you disagree perhaps you would be good enough to express it and provide us with a source for that expression.
Until there is a coherent falsifiable hypothesis the default position remains that climate is constantly changing, that the earth goes through warmer and cooler periods and humanity may (indeed almost certainly does, but no-one has yet quantified it) have a marginal influence on climate.
And that's it. I don't have to prove anything. They are the ones saying it isn't so and they are the ones who carry the burden of proof.
And to cap it all he's posted a straw man because (as I've just said) there is every chance that humanity does have a marginal effect and asking for the null hypothesis to be proof that there is no influence at all is ludicrous.
Mike
Good comment. I said earlier on this thread that I'm uncomfortable with acting as an apologist for Trenberth, but in a way he is not relevant to the core of the discussion.
Which can be simplified further still:
- Hypothesis 1 states that based on the uncontroversial and long-established physical properties of CO2, increasing the amount in the atmosphere will increase the amount of energy in the climate system.
- Hypothesis 2 states that despite the uncontroversial and long-established physical properties of CO2, increasing the amount in the atmosphere will not increase the amount of energy in the climate system.
Hypothesis 1 is self-contained. Hypothesis 2 is not and requires the suspension of the laws of physics or a large misunderstanding of the way energy moves around in the atmosphere.
Trenberth - or BBD if you prefer - states that Hypothesis 1 is validated by observations of GATA and that Hypothesis 2 be rejected.
For the life of my, I cannot see why this is a problem.
The argument is and has always been about climate sensitivity.
Jun 22, 2011 at 4:37 PM | BBD
I didn't ignore the abstract. I think it is vitally important to get work like this into the IPCC report. Currently the IPCC states little variability in the past climate (and emphasise that the variability we are seeing here is limited to Europe). Also it is vitally important that the models they are using for the predictions can reproduce this variability before we start using them for any kind of forecasting.
You seem to go from this abstract of leather shoes showing up after a really, really warm summer => imminent manmade CO2 disaster (I'm not actually sure what your position is on CAGW). Personally I can't see any possible physical mechanism that would heat the alps more in the height of summer without having heated the worlds oceans by a fair few degrees first. It is plausible physical mechanisms backed up by evidence that is what we need.
BBD,
A small note here.
You misunderstand the term 'null hypothesis'. Either that, or you use the term loosely.
When you study, you eventually quantify what is known as an 'effect', or establish relationships between two or more phenomena.
The null hypothesis is simply a statement that there is no effect, or that there no relationship extant between the studied phenomena.
A null hypothesis is not equivalent to a 'competing hypothesis' in meaning.
When you propose a hypothesis (There is a significant anthropogenic influence on the climate in rapid climatic timescales), you frame the null hypothesis: "the anthropogenic influence on the climate is negligible. You then try to reject it or disprove it.
As an outsider, a sceptic is under no duress to come up with alternative explanations for hypotheses for which the null hypothesis is not satisfactorily rejected. He or she can just say: " I don't know, don't ask me" which is completely fine and does not make him or her a 'denier' or 'close-minded'.
Addendum: Just because a null hypothesis is rejected, it does not mean that the proposed hypothesis is true.
Rob B
I'm a lukewarmer.
The Holocene Thermal Maximum isn't modelled by the GCMs referenced in AR4 because it was caused by Milankovitch forcing which is not directly relevant to C20th and C21st climate or the IPCC's remit - which is to review the evidence for AGW.
The point about ancient leather is that it needs to have been permanently frozen and covered by ice for 5ky or it would have been destroyed almost immediately on exposure.
This shows that the hot summer of 2003 achieved something not seen in that region for 5ky - enough melt at Schnidejoch to expose Neolithic artefacts. In the same year, the 'Ice Man' emerged in the Oetztaler Alps, where he had been frozen solid for 5.3ky.
My point was that, taken with the Polyak study and the World Glacier Monitoring Service report, the evidence of extremely unusual conditions affecting the cryosphere is pretty solid.
And I have gone to the trouble of backing up what I say with some examples. Unlike those here arguing that it's all normal, natural variation. If that is so, then why is 5ky old ice melting now? What is the cause?
This is not well thought out. You can have a sufficient warming of the atmosphere to heat an ice field in summer enough to melt it without necessarily having the oceans warmed by 'a fair few degrees first'.
As you say, plausible physical mechanisms are important. And there is nothing inherently implausible about radiative forcing from CO2. In fact the basic effect isn't remotely controversial. I discussed this with Mike above.
Shub
You say:
And I said:
- Hypothesis 1 states that based on the uncontroversial and long-established physical properties of CO2, increasing the amount in the atmosphere will increase the amount of energy in the climate system.
- Hypothesis 2 states that despite the uncontroversial and long-established physical properties of CO2, increasing the amount in the atmosphere will not increase the amount of energy in the climate system.
Is it just me, or are you splitting hairs without actually saying anything that matters?
You go on:
No, it just leaves them in the unfortunate position of sounding ill-informed and not at all convincing.
BBD
Thanks for the elaboration.
Hypothesis 1 is surely contradicted (at least as far as AGW goes) by (a) the evidence that increases in atmospheric CO2 lag increases in temperature by ~800 years, and (b) the observational evidence that during the 20th century there is no particularly good fit between increasing CO2 levels and increasing temperatures.
It may be the case that "increasing the amount [of CO2] in the atmosphere will increase the amount of energy in the climate system" but if so it cannot - given (a) and (b) - be causing a temperature increase, which may explain Trenberth's "travesty" remark. What other possible effects are there? Absorption by the oceans at a greater level than anticipated? Transmission out of the system to space at a faster rate than anticipated? It seems that the models do not accept either of those possibilities but until they have been properly considered it would seem that Hypothesis 1 fails adequately to explain global warming and says little or nothing about the anthropogenic element.
And I'm in imminent danger of getting out of my depth here!!
BBD,
You don't understand how formal science works.
While an inability to reject the null hypothesis leaves those who propose hypothesis on shaky ground, those who brings evidence that argues against said hypothesis are in no way left looking 'ill-informed'.
Both your hypothesis 1 and 2 are mere rhetorical sleights of hand.
@Jun 22, 2011 at 7:02 PM | BBD
As an aside, Otzi the Iceman was found in September 1991. Thursday, September 19, 1991 – 1.30 p.m.
About lunchtime in fact ;-)
http://www.iceman.it/en/node/233
No-one has pointed out the most insulting comment in Leo’s piece, when he says that he’s willing to risk being cast as a climate appeaser. Nice.
Is Your Grace thinking of annexing the Sudetenland?
Mike
My understanding of the 'Vostock lag' is that warming events caused by Milankovitch forcing and ice sheet dynamics (Bond cycle) caused the oceans to release CO2 into the atmosphere. The elevated CO2 may have amplified the initial warming but was not sufficient to over-print subsequent cooling, which also caused the oceans to re-absorb CO2 and bring levels down again.
This does not invalidate the AGW hypothesis which claims that substantially elevated levels of CO2 (well above the paleoclimate range of variation as shown by the Vostock and Greenland ice core studies) will become the dominant forcing acting on the climate system.
The terms 'energy' and 'temperature' can be used interchangeably. Increasing the amount of energy within the climate system will cause it to warm.
The temperature history of the C20th varies as it does because (as in paleoclimate) CO2 is not the only forcing. Other factors affect the climate. The AGW hypothesis argues that CO2 is gradually becoming dominant as levels continue to rise. Meanwhile, natural variation continues, hence the imperfect fit between the Keeling curve and GATA.
You go on to repeat almost word for word some points I made earlier on in this thread, which are the questions presumably keeping Trenberth up at night. These factors, particularly the rate at which the real - not the modelled - climate system radiates energy to space in response to CO2 forcing are central to the lukewarmer position.
As I keep saying, the argument is - or should be - about climate sensitivity. And when we look at the observed temperature and compare it with the multi-model mean (done by Lucia at the Blackboard) we see that it is significantly lower than the projection.
Trenberth and Hansen speculate that the 'missing' energy may be in the deep ocean. Hansen speculates that stratospheric aerosols are reflecting solar SW back into space and so reducing the effect of CO2 forcing. Neither has proved their case.
It's all very interesting, much more so than 'debates' surrounding the supposed non-effect of CO2 on climate.
woodentop
So he was. My mistake there.
Shub
Yes, I do.
What evidence?
No, they aren't. And you know it, which is why your argument is disappearing into obfuscation.
Shub
I'm a lukewarmer, as you know. Nothing would give me greater pleasure than to learn that the actual effect of increasing CO2 forcing is right at the bottom end of the proposed range. Just so we are clear about this.
The evidence that is brought to play to argue against the provenance of the theory of anthropogenic (CO2-driven) rapid warming is the same evidence, in the face of which the consensus maintains its status quo.
It is indeed a strange situation, where the 'evidence' for anthropogenic warming resides in the computer models, and consequently the lack of a matching reality itself becomes 'evidence' that sceptics are forced to persuade their opponents with.
Shub
Not sure I fully understand the above (especially 1st para). Are you talking about the divergence between observations and the multi-model mean?
BBD - your 5000 year ice argument looks strong, and I do not dispute that there is not as much permanent ice in the high alps as there used to be. But less ice loss is not just a function of increased temperatures, as has become apparent wrt Kilimanjaro for example, where recent snow field/ice loss has been found to be due to increased sublimation through lower humidity (resulting from loss of forests on the adjacent plains), not an increase in temperatures (iirc the average temperature at the summit is -4C). Increased solar radiation (through decreased cloud cover) is also a more plausible contributory factor in all areas where the average temperatures are well below zero for most of the year.
Even if GATA have increased by 1C in the last 100 years, there's nothing to link this with increased CO2 concentration. And there is plenty of evidence that temperatures were just as warm 1000 years ago than they are now, e.g. here are just a a couple of links:
climate - MWP warmer 1000 years ago - Saragasso Sea:
http://www.sciencemag.org/content/274/5292/1503.abstract
climate - MWP just as warm 1000 years ago, Indo-Pacific Warm Pool, Nature 2009:
http://www.whoi.edu/page.do?pid=7545&tid=282&cid=59106&ct=162
Here's an image of the Jakobshavn glacier verses Hadcrut NH for you to ponder:
http://farm5.static.flickr.com/4139/4753025383_5c34f3dd93_b.jpg - this suggests to me at least that the main reason for the glacier's retreat is due to lag from the LIA, not CO2.
BBD,
You drag everything to your playground - 'climate sensitivity'. I don't see how that is productive.
What are your views on Hickman's peace overture? Do you accept it? reject it? What do people like Hickman bring to the table when they ask for peace and a 'meeting of moderate minds'? These are more interesting questions at the moment.
Yes, we all need to do better, not abuse scientists, agree to what the data says, and the warmists need to not call people deniers and other epithets. But that will not resolve the underlying fundamental differences. More immediately, for example, a certain level of trust between scientists and citizens that was present pre-Climategate was broken. It needs to be built back slowly - by efforts on both sides no doubt, but it is clear to me that the other side has major responsibilites in this regard which they wish to simply shirk away.
As a journalist, Mr Hickman can certainly help. Why not call out on the bad apples? Instead what he has written are puff pieces defending the establishment, by simply reproducing their claims and taking them at their word.
Show me one article from Mr Hickman where he lays out a clear and consistent call for openness in the practice of climate science. Show me one article where he is anything as mildly critical of the IPCC. I just went through the complete listing of his articles at the Guardian.
Hickman asks for transparency from the IPCC today, because what they do is a public relations nightmare to his side, not because he wants 'unimpeachable science'. He says so himself.
What do you think about his piece?
BBD
You say "This shows that the hot summer of 2003 achieved something not seen in that region for 5ky - enough melt at Schnidejoch to expose Neolithic artefacts."
5000 years takes us back only about as far as the time the pyramids were built: well into the recency of recorded history.
The hockey team claimed that current warming is unprecedented in the last 1000 years. So what? The Schnidejoch evidence shows that it's certainly not unprecedented in the last 5000 years. Not much difference in my view. We're hardly talking about "geological" timescales.
Lapogus
Agreed wrt Kilimanjaro. But that's why the combined evidence of unusually high rates of ice loss is interesting. Natural variation - including the various warm periods - has not been sufficient to cause the breakup of the ice sheets off Ellesmere Island or the melt in the ice fields that have yielded up perishable Neolithic artefacts. In both cases, something has happened that is apparently unique in the last five thousand years.
Jakobshaven is one glacier. The World Glacier Monitoring Service does what it says on the tin, and shows a global shrinkage which the cryosphere specialists think is unusual.
It always tends back to the simple argument: what's new?
Unfortunately, we know the answer to that, and the hypothesised effects.
I did mention the other day that thing about choice of words ;-)
If you think climate sensitivity is not relevant to the climate debate, fine. We must agree to differ.
I've refrained from comment on Mr Hickman on this thread because there's plenty to go round. Let's say that rational dialogue is better than trench warfare, and sometimes compromises have to be made. Or nothing happens.
If you are asking whether I endorse Mr Hickman's house style, then no, I do not.
Simon Abingdon
What matters is why it is as warm now as it apparently was 5kya. The warmth then was the afterglow from the recently passed Holocene Thermal Maximum. This was in turn caused by Milankovitch forcing.
That's not happening now, so the inevitable question is: what's going on?
Lapogus
I'm not sure that you've been keeping your eye on BBD's thimble.
If we have now got to the point that warming has uncovered Neolithic artefacts that in itself tells us nothing except that temperatures now may be similar to what they were 5,000 years ago. (The other points you make about ice loss are, of course, equally valid).
Since the world seems to have survived without major catastrophe since that time the presumption must be that there is nothing about present-day temperatures that need give us cause for concern.
Which reinforces the argument that it is for the climate scientists to come up with some convincing evidence that this time things are different.
Climate, from what I have learned about it over the last few years, is partly chaotic and partly cyclical. Why should the early 21st century be any different -- except that there are those with a misanthropic philosophy which demands the reduction or elimination of humanity's use of natural resources, especially fossil fuels, and CO2 is a heaven-sent peg to hang their belief system on.
They may call themselves environmentalists or even conservationists but they are as far removed from genuine environmentalism or conservation as chalk is from cheese.
BBD
If the points I made earlier about the CO2 time lag and the lack of correlation between CO2 and temperature during the 20th century are correct then feedback is not relevant. And in any event we know squat about feedback which is one of the battles that is going on, isn't it? And since we know that models don't do clouds very well and they are an important factor in feedback (we are told), we don't actually no squat about anything very much.
And on that basis alone I am not inclined to listen to Trenberth (or anyone) telling me what I have to believe on pain of "I know not what but they shall be the terrors of the earth" (King Lear) punishments, without a good deal more empirical evidence than I have been presented with so far, which is approximately none.
Mike
I'm not trying to deceive you. And I'm sorry that you might think I am.
Our posts seem to have crossed so I won't repeat what I said above.
Why? Increasing CO2 is a feedback from a warming event (biosphere and OHC lagged response). The additional CO2 moderately amplifies the initial warming, but gets overwhelmed by the next temperature crash when something freshens and cools the N Atlantic.
Something being the collapse of the Hudson Bay ice sheet or massive episodes of flooding as the North American ice sheet melts at the end of each Ice Age.
None of this conflicts with the AGW hypothesis, which is why I accept it. Not being unusually stupid, I can see that there are... issues with all sorts of aspects of the way this is being 'explained' to Joe Public.
Which is one of the reasons I come here.
Hi Bish & Leo
with regards the post & comments especially last post BBD Jun 22, 2011 at 11:04 PM with -
"issues with all sorts of aspects of the way this is being 'explained' to Joe Public"
this in my opinion sums up the main problem, the majority of Joe Public will listen to smartasses/experts for so long & then ignore them as not relevant to there day to day lives.
Leo, even if all the Science & "luke-warmers" could agree to disagree on the Science, do you really think when push comes to shove, with real life consequences, Joe Public (UK) will be on side to change their habits?
just asking
Jun 22, 2011 at 7:02 PM | BBD
As explained in the paper you referenced you correctly point out the Holocene maximum was likely due to Milankovitch forcing. At least you agree with many sceptics in refuting Mann's work (ie 'The Hockey Stick Illusion' for example where the MWP and little ice are missed out unlike in this work and also not explained by Milankovitch forcing.
There are lots of possible explanations for why artifacts were buried for 5000 years, not ruling out natural variability burying something in this location for that long as we are currently in a warm period. The same kind of fact of recent melting revealing viking settlements in Greenland for example, is used to suggest a warmer medieval period for there an then. You need lots of corraborating evidence either way to start suggesting what might actually be causing the changes.
As I've said I like Svensmark's hypothesis together with long term oceanic variability (It takes thousands of years to turnover) as describing a lot of the past climate. I think any radiative CO2 effect should be cancelled out by negative water cycle feedback (mainly clouds) and don't understand why many people think this should be a positive feedback when commonsense suggests otherwise. Matching observations will show which theories work out being correct though.
@BBD
As Rob B already pointed out the regular occurring warming periods in the Holocene
seeming to have cycles of about 1000 y, there are also many other cycles.
All of them are easy linkable with astronomical cycles as also the Milankovitch forcing.
Here a good read about cycles in secular timescales:
http://www.fel.duke.edu/~scafetta/pdf/scafetta-JSTP2.pdf
Some text from the Conclusion:
Herein, we have found empirical evidences that the climate oscillations within the secular scale are very likely driven by astronomical cycles, too. Cycles with periods of 10–11, 12, 15, 20–22, 30 and 60 years are present in all major surface temperature records since 1850.
It has been discussed at: http://judithcurry.com/2011/04/14/scafetta-on-climate-oscillations/
The other thing is the so called "Greenhouse Effect" of which you believe it is based on Physics.
The exact opposite is the case:
http://greenhouse.geologist-1011.net/
Those who think this is all about science should not be fooled. In reality, it's all about the Socialist Alliance, which used to be the Socialist Workers' Party, crashing the economy by power starvation thus making the population so poor it will rise in revolt.
BBD - I like how you are seeking reasons to explain the big variability in temperatures in the post glacial millennia. As someone who had a father who instilled in me to always question and think, I have always wondered (having grown up in the glacial landscapes of Argyll and Perthshire) what it was that triggered the Loch Lomond re-advance (as it was known in my school days) and also the warm periods which enabled the neolithic and Bronze Age people to live at higher altitudes than we do today (despite their lack of central heating and celotex). I think the rapid break up of the Hudson Bay ice dam can explain a lot (and quite possibly the sunken stone circles off Norfolk and Carnac in France) but not all. I think changes in ocean currents (as an indirect result of sea level rises, rather than just the sudden release of colder fresh water from the North-American ice-sheet) have a big part to play here.But why this interglacial has persisted unlike the preceding four is the big question to me, and have a feeling a lot of it comes down to the North Atlantic Drift aka Gulf Stream. This will probably cause you consternation but I am going to throw it in anyway. About 30 years ago Otto Muck (a German engineer) wrote a well researched and book and argued that Plato's was right, and that there was considerable (admittedly circumstantial) evidence for the existence of an island in the Atlantic, roughly where the Azores are now - they were the mountain tops) which Muck suggested was not lost through rising sea levels, but by collapse of the thinner crust below the ocean floor (more a kind of Prof. Hapgood event / rather than a Storegga Slide, but who knows). A consequence of this was that the gulf stream could then flow unimpeded into the north Atlantic (and Norwegian Sea), triggering the Holocene and making much more difficult for substantial year-round ice sheets to remain in the Arctic and north-west Europe. And a whole new ball game for ocean currents which could explain the unprecedented persistence of this interglacial. You will probably laugh this off, but a lot of it makes sense and as the decades have passed since I read the book I (and other readers judging from the recent reviews on Amazon) it all still seems like a credible thesis (remember that just because 99% of the stuff written about Atlantis is garbage it does not mean that that there may not be something valuable in the trash can). So there may be much more to the transition from glacial to Holocene than just Milankovitch cycles. What I do fail to accept is that CO2 is the only credible hypothesis - I much prefer Tallbloke's thesis - http://tallbloke.wordpress.com/2011/06/02/what-caused-global-warming-in-the-late-c20th/ and would be interested in your thoughts on this.
BBD,
When you look at the ebb and flow of the glaciers in Grosjean et al, do you not see what I see - namely that the current extent is within historical range?
If the graph in Grosjean were to become the IPCC poster child - replacing the Hockey Stick - there'd be no CC to merit an IP, methinks.