2011-06-05 02:40:09Last Interglacial (Eemian . MIS 5e) Climate
Steve Brown

brownsg@gmail...
80.177.115.133

I have a proposal for a series of articles on the climate of the Last Interglacial (aka Eemian / MIS 5e) and if it can provide value in helping us predict the impacts of AGW.  The series will be based upon the dissertation that I submitted to complete my Geosciences degree last year.  I've pasted the abstract below which will give you a flavour of the series overall:



Abstract

Human society likely faces significant challenges in the next century and beyond due to the climatic effects of anthropogenic global warming related to increasing greenhouse gasses, changing land use and deforestation.  In order for us to mitigate the effects of climate change and minimise the impacts to our society and environment, it is essential to be able to make accurate predictions for the nature and severity of those impacts.  Much of our predictive ability at present relies on computer modelling which is unfortunately limited in power and accuracy by current technological limits, the complexity of the systems being modelled, and the uncertainties in current scientific knowledge.   The Last Interglacial, from ~130 to 116 ky, was a period when global temperature was up to 2oC higher than present, which is comparable to predictions made in the 2007 Intergovernmental Panel on Climate Change Assessment Report 4, for global temperature by 2100 under current levels of anthropogenic CO2 forcing.  This report reviews a range of  published palaeoclimatic and palaeoenvironmental research relating to the Last Interglacial and finds that its suitability for aiding prediction of future climate change is mixed.  The differences in orbital forcing during the Last Interglacial, and elevated atmospheric CO2  in the future, mean that a valid comparison of possible environmental effects is limited.  However, predictions of global sea-level rise, shrinking of ice-sheets, and the possible slowdown of the Atlantic Meridional Overturning Circulation by 2100 in response to a 2oC increase in global temperature are broadly comparable to what was found to have occurred during the Last Interglacial.  Comparison of the El Nino Southern Oscillation activity during the Last Interglacial and the recent past suggests that it is stable during interglacials, but that El Nino events may be becoming more frequent due to recent greenhouse warming.


Unfortunately, my dissertation had a tight word limit so large chunks of it are rather dry and clipped and will need a fair amount of rewriting to make it more readable for a casual lay audience (I wish I'd kept those earlier drafts!).  I'm happy to forward a copy of the original if you mail me at brownsg@gmail.com.

The series will consist of roughly the following instalments:


1. Introduction to the Last Interglacial (LIG) and it's importance to understanding future climate
2. The primary causes of climate change during the LIG - orbital and GHG forcing
3. Sea-level and ice sheet volume during the LIG
4. Oceanic controls of climate during the LIG - thermohaline circulation, NAO and ENSO
5. Terrestrial controls of climate during the LIG - albedo and vegetation changes
6. Summary and conclusion - what can and can't the LIG tell us?


In order to elicit comments and suggestions while I get my head around the article submission process, I've pasted an intial draft of the introductory instalment below:



Human society has benefited from the relatively stable climate of the Holocene, which has allowed agriculture, and technological civilization to flourish.  However, in recent decades there has been a growing evidence showing that human activities are beginning to have an impact on the stable climate of the past few thousand years through release of greenhouse gases from fossil fuels and deforestation.  Recent reviews of published climate research, such as those conducted by the IPCC have led to predictions of significant anthropogenic global warming and the consequential impacts on sea level, ocean chemistry, precipitation, drought, and extreme weather events, all of which are expected to have considerable negative effects for the human population and the other species that inhabit the Earth.

Many of the current predictions for future climate and environmental impacts in the literature have been made on the basis of complex computer models of the Earth's systems.  Though such models have been successful in many areas, and are improving in accuracy and fidelity with increasing computer power, they still carry large uncertainties and margins of error, especially the further into the future that models are run.  One way that such uncertainties might be reduced is by looking at the geological and fossil record for periods in Earth's history that were warmer than today and determine how the environment responded.  This may allow us to better estimate the effects of climate change that could face us.

The Last Interglacial, also known as the Eemian and broadly corresponding to Marine Isotope Stage 5e (MIS 5e), was a period with a global average temperature up to 2 to 3oC higher than the present day and similar to some predictions for the next century by current research.  The Last Interglacial offers several benefits for comparison with the present day in that continental configuration, flora and fauna are near identical to today, as well as being a recent enough period to provide a range of high-resolution palaeoenvironmental proxy indicators.  The Last Interglacial was also a period with higher eustatic sea-level and a corresponding reduction in ice sheet area and volume,  which are consistent with IPCC predictions for responses to future global warming.

The Last Interglacial, as characterised by the Eemian stratigraphical stage and  Marine Isotope Stage 5e [fig.1: A,B & C], is of interest as it is the most recent geological analogue of our present warm period and was likely warmer and moister than today.  In Europe, the early part of the Eemian, as it was in transition from the preceeding glacial stage,  is distinguished by a steppe environment giving way to pine forests and then extensive oak and hazel forests as the climate warmed.  Global sea-level was estimated to have been ~5 m higher, resulting from a reduction in size of the Greenland and Antarctic Ice Sheets.  Coniferous forests were widespread at high-latitudes; deciduous forests were widespread at mid-latitudes [fig.1: G & H], with low-latitudes predominantly savannah.  Northwestern Europe, being isostatically depressed from the previous glaciation, was flooded by the Eemian Sea which connected the Barents and North Seas.  The Eemian climate is characterised as being predominantly oceanic i.e. with relatively cool summers, comparatively warm winters and reliable precipitation (Kukla et al., 2002; Brewer et al., 2008).

*****FIGURE 1 - to be added once I work out how to submit images as Firefox won't let me paste *******

Figure 1: Stratigraphic units A, B, marine isotope stages C, insolation D, SPECMAP benthic O-isotope record with Heinrich and Cold events E, Vostok proxy air temps F, arboreal pollen from marine core off Portugal G, pollen record from La Grande Pile and Ribains (France) H (Kukla et al., 2002)

Mean temperature peaked in the first 3000 years of the Eemian, while precipitation remained relatively low.  The Last Interglacial then progressed to a more oceanic climate in Europe with higher precipitation.  This oceanic climate may have been made more pronounced due to the connection between the Arctic and Atlantic oceans via the Baltic sea that opened up as global sea-level rose in the early Eemian (Zagwijn, 1996).

In Arctic Canada, the mean summer temperature was estimated to be 4 to 5oC higher than today and had vegetation similar to modern southwest Greenland (Frechette et al., 2006); in southern California the region experienced a Mediterranean climate similar to today, though possibly slightly warmer (Heusser L E, 2000).   Kienast et al. (2007), produced a pollen based climate reconstruction from the East Siberian Arctic and found the mean temperature of the warmest month during the warmest interval of the Last Interglacial was ~9 to 14.5oC, compared to 2.8oC today.  These reconstructions also suggest that mean annual precipitation was up to 50 mm higher than today.

In Alaska, summer temperatures were 1 to 2oC higher than today, but winters were 1 to 3oC cooler; in Greenland, summers were up to 5oC warmer than present.     The faunas identified in a variety of localities around North America indicate a warmer climate than present and provide consistence with Last Interglacial climatic reconstructions from Europe, Japan and Australia (Muhs et al., 2002).  This strong seasonality, with warmer summers and colder winters characterises the Last Interglacial climate (CAPE-Last Interglacial Project Members, 2006).

 

I'll aim to get a proper draft submitted of this first article in the next few days. In the meantime, I look forward to hearing any comments, criticism or guidance.

 

Thanks, Steve

2011-06-05 03:30:11
grypo

gryposaurus@gmail...
173.69.56.151

This is an outstanding idea!   Looking forward to the finished versions.

2011-06-05 07:45:53
Rob Painting
Rob
paintingskeri@vodafone.co...
118.92.123.2

Ditto on Grypo's comments.  

2011-06-05 08:05:21
Riccardo

riccardoreitano@tiscali...
93.147.82.122

Good idea. This is one thing people will easily understand.

The first two paragraphs are redundant. Just a couple of sentences explaining the analogy between the Eemian and future climate will suffice.

I see the narrative as a description of the nearest analog of our future climate. I'd leave more technical aspects (e.g. models) out.

"connection between the Arctic and Atlantic oceans via the Baltic sea". How did this connection work?

P.S. I'll be glad to read your dissertation: riccardoreitano@tiscali.it thanks.

2011-06-05 08:46:04
Glenn Tamblyn

glenn@thefoodgallery.com...
124.176.234.22

Go for it Steve

 

2011-06-05 20:51:16
John Cook

john@skepticalscience...
121.222.9.229
I would suggest adding some links. Eg - when you mention the IPCC, links to AR4.

I'd avoid or explain technical jargon like 'eustatic'. I like the idea of breaking it up into shorter posts like this but it needs some sort of conclusion. What's the take home from this post?

lastly, is it just me or is 5 metres sea level a huge bombshell (and I thought it was > 6 metres). That fact is buried in the middle - I'd make it more prominent, maybe even in an infographic (I can help with that if you wish)

2011-06-05 21:09:08
Rob Painting
Rob
paintingskeri@vodafone.co...
118.92.119.86

Sea level was 6-9 meters higher according to a couple of 2009 papers, IIRC. And why is 5 mtrs a bombshell if you thought it was greater than 6 mtrs?

2011-06-05 22:04:23Bombshell
John Cook

john@skepticalscience...
121.222.9.229
Not a bombshell for me, I was already aware of many metros of sea level rise from a few degrees of warming, but this is not commonly known by most people. To me, this is the most startling lesson from the Eemian - the sea level rise from just a few degrees of warming. It's a picture of our future and it's not a comforting one. Although we've mentioned it in the past on SkS, I'm sure mentioning it in this post, particularly if it's made more prominent, will shock a few readers.

What really gives me the heebie jeebies is 25 metres sea level rise from 3 million years ago - the last time co2 levels were 350 to 400 ppm. People ask me how I keep motivated to keep on doing SkS. Just that one figure - 25 metres - is all the impetus I need.

2011-06-05 22:11:35
nealjking

nealjking@gmail...
91.33.118.33

JC, there might have been additional factors as well as the CO2 concentration.

2011-06-06 01:26:32
Steve Brown

brownsg@gmail...
80.177.115.133

Some great comments above which I'll consider incorporating for the next draft.

@Riccardo - The Eemian Sea flooded much of northern Europe leaving Scandinavia as an island and providing a southerly connection between the Arctic and Atlantic oceans; effectively where the Baltic is today.

@John & Rob - When I did the literature search last year and dug up pretty much every paper in existence that considered Eemian sea-level, I found a fairly large spread of estimates ranging from 3 to 10 m.  However, the majority were in the 5-6 m ball-park, which seems to be the consensus.  The problem with the more extreme estimates is that they are based on a small number of sites where local tectonic influences can't be fully ruled out.  I would contend that ~5 m is plenty to be concerned about anyway. 

2011-06-06 01:47:58
Chris Colose

colose@wisc...
72.226.118.197

This is a good post, but the "2-3 degrees warmer than present" stuff at the Last Interglacial is almost certainly not right.  I point this out not to be picky, but because the spatial structure of how various places warm or cool gives a lot of insight into the forcing involved.  SkS has also been making a big deal lately about the issue of global vs. regional change so we need to be consistent.

At present, the greenhouse forcing is (to first order) more or less globally uniform and involves a reduction in the outgoing radiative heat loss.  For orbital changes though, there is no such global synchronous forcing.  There is some slight albedo change and greenhouse feedbacks that affect the global temperature between glacial and interglacial states, but you need to go back to the Pliocene to find times on the order of a couple degrees warmer than modern. 

This is not inconsistent with higher sea level in the last interglacial, since preferential forcing at the high latitudes can melt a lot of ice.

2011-06-06 02:16:18
Steve Brown

brownsg@gmail...
80.177.115.133

@Chris - I accept your point about being careful with regard to regional versus global.  The overwhelming majority of proxy estimates of temp during the LIG are from the N. hemisphere, with much of the warming occurring within the Arctic (one estimate puts the East Siberian Arctic at +14oC warmer than today).  The +2oC average global temp that is often mentioned in papers covering the period is certainly open to argument due to the lack of a fully global proxy record.  I'll endeavour to keep the phrasing of my posts in line with this.

2011-06-06 07:14:17
Riccardo

riccardoreitano@tiscali...
93.147.82.122

Thank you Steve, I've never heard about it and couldn't immagine that a few meters could flood Finland (I guess) to such an extent. Could you give me a reference if you have one at hand?

I agree with Chris's comment. I think you should add something on the differences between the LIG and the projected future warming.

2011-06-06 08:02:23
Andy S

skucea@telus...
66.183.188.172

I'm looking forward to this series!

One thing that's sure to come up from skeptics is the question about how polar bears survived the Eemian. Comparisons with the  rate of change of Eemian warming with what we are doing now my be relevant to this question. The bears had much more time to adapt then, I believe.

Some comparisons between the Eemian and the Holocene would be helpful, particularly if you can shed some light on the pattern of many of the interglacials, which consists of an early temperature peak followed by a slightly lower plateau. Again, the slightly warmer temperatures (than now) in the early Holocene are a favourite skeptic talking point.

 

2011-06-06 15:51:55
Rob Painting
Rob
paintingskeri@vodafone.co...
118.92.121.208

Andy - it'll complement with your article(s?) on the Holocene quite well won't it?. Wasn't the Eemian highstand due to an eccentric orbit, greater obliquity than today and perihelion co-inciding with the northern hemisphere summer?, and you're covering the Holocene Climatic Optimum, when again, perihelion occurred at the same time as the northern hemisphere summer. Kinda highlights the fact the Earth's climate is very sensitive to perturbation. 

Steve - what was CO2?, 270-290ppm?. Gonna mention that in your first article?

2011-06-07 06:25:32
Steve Brown

brownsg@gmail...
80.177.115.133

@Riccardo - There's a good summary of what was going on with the Eemian Sea plus a few refs here.  Remember that N. Europe and Scandinavia had just lost a whopping great volume of ice cover so would likely have been more isostatically depressed compared to today.

@Andy & Rob - Yes, I will be covering the differences/similarities between the LIG and the Holocene.  As Rob mentions, the orbital configuration was significantly different during the LIG with correspondingly higher insolation compared to today.  CO2 was 250-290 ppm according to Rundgren et al. (2004), i.e comparable with the pre-industrial Holocene.  An interesting comparison to make will be that the warm Eemian climate was primarily influenced by high insolation, but that we are warming now even though we are heading on to a cooling orbital configuration since the Holocene Climatic Optimum.  Now, why would that be? ;-)

 

 

 

2011-06-07 06:55:55
Andy S

skucea@telus...
66.183.188.172

Rob: I don't think I'll be covering the Holocene in a dedicated article. The Holocene argument I enquired about previously is  part of a Gish Gallop rebuttal, I'm trying to write. I may even skip over it altogether because I think I'll have to focus on two or three other points that more clearly show show a wilful attempt to distort reality on the part of the original author, whereas his argument on the Holocene is just ignorant and not even original, using WUWT and JoNova as references.

I'm sure Steve's upcoming articles will cover the Holocene and LIG far better than I can and I'll be happy just to link to them.

2011-06-07 07:02:16
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.31.52

Righto Andy, I'll touch upon the HCO in the next Amazon drought installment anyway. For a moment there it looked like all the posts were going to tie together beautifully.  

2011-06-07 08:27:33
logicman

logicman_alf@yahoo.co...
109.157.215.19

Great idea for a series of articles!

 

"... in recent decades there has been a growing evidence showing that human activities are beginning to have an impact on the stable climate of the past few thousand years through release of greenhouse gases ..."

suggestion:

"... ever since 1938 there has been growing evidence showing that human activities are continuing to have an impact on the stable climate of the past few thousand years through release of greenhouse gases ..."

I think that for many people - especially the under 50s - 'recent decades' implies something of the order of 30 years or less.  In fact, the evidence for the warming effects of anthropogenic CO2 mounted at first slowly from 1938 to about the mid 1950s and then accelerated more post- 1970s.

Callender's 1938 paper* stands at the point when writings on atmospheric CO2 moved from being predominantly about explaining ice ages to being predominantly about explaining global warming - a term already current in the 1930s.

 

[*] - Callendar, G.S., 1938. The Artificial Production of Carbon Dioxide and Its Influence on Temperature. Quarterly Journal Royal Meteorological Society vol. 64, pgs. 223–240.

http://www.rmets.org/pdf/qjcallender38.pdf

On page 231 the reason is given why Callender did not see CO2 as a long-term problem: he expected CO2 emissions to remain low due to continual improved efficiency in fossil fuel combustion.  He was a steam technologist writing in an era when records were being broken by steam ships and railway locomotives due mainly to improvements in combustion technology and steam engine efficiency.  This is what I call 'the tragedy of tomorrow': the failure to see a problem or to act on it which arises from a belief that our descendants will automatically know how to deal with it.

Many favorite denier talking points are covered and rejected in the paper and the discussion.  Note that in this paper the 'discussion' section records real discussions of the paper, rather than the currently more usual topics for future discussion.

2011-06-08 05:55:58
Steve Brown

brownsg@gmail...
80.177.115.133

I've now posted my working draft of part 1: http://www.skepticalscience.com/LIG1-0706.html

I still need to work on the formatting and adding reference links.  The formatting buttons in Author Admin don't seem to work in IE9 for me for some reason??  Anyone else have that problem?  Also, the palaeo reconstruction diagram I've added is fairly unreadable after having been reduced to 500 pixels.  I'd be interested in your opinion as to whether that graphic is worth salvaging.  Otherwise, there are a couple of other graphics in AR4 WG1 Ch.6 that I could look to use instead - though not similar.

2011-06-08 06:12:58
Rob Painting
Rob
paintingskeri@vodafone.co...
118.92.100.83

Steve, follow the Yooper's (Dan) suggestions here.  That way when the cursor moves over the image, the reader can click on the larger version.

Don't use IE9 so can't help you with that problem. If you're having issues with adding links, have you highlighted the portion in the text first?, once you do so the link/un-link buttons become visible.

I think you'll find the html editor has a resident poltergeist anyway.  

2011-06-08 06:46:43Image size
John Cook

john@skepticalscience...
121.222.9.229

You can go up to 570 pixels wide without breaking the SkS design.

What do you think of linking to http://sks.to/past for your closing paragraph where you mention past climate change?

2011-06-08 10:08:09A Resource Document Needed
John Hartz
John Hartz
john.hartz@hotmail...
99.95.221.238

This article would benefit greatly if SkS had a resource doument about geological time that the average person could check out if he/she wanted to see where the Eemian fits into "big picture."  

See http://www.skepticalscience.com/thread.php?t=1780&r=1

 

2011-06-09 06:00:28
Steve Brown

brownsg@gmail...
80.177.115.133

Some great suggestions there folks.  I've stumbled upon some absolutely superb graphics of Eemian orbital forcing, sea-level etc. by John Garrett (jg) who has guest posted at least once for SkS:  http://www.skepticalscience.com/ice-data-made-cooler.html and also on his own blog.  It would be great to link to if he doesn't mind and it would come close to what Badgersouth has suggested!

2011-06-09 06:07:26
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

People are generally quite pleased when you link to their posts, Steve :-)

2011-06-09 07:49:18
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.8.61

Steve, perhaps the wording can be simplified a tad? Neal King (Nealstradamus) is always on at me about that - and rightly so, we're aiming at the layperson. It won't be obvious, even to most climate blog lurkers, what a steppe environment is, for instance. 

2011-06-13 01:49:02Final draft ready
Steve Brown

brownsg@gmail...
80.177.115.133

The final draft of LIG Climate Part 1 is now ready.   Votes for it being ready to publish would be appreciated.

I would prefer that it was not published for at least another week.  I'd like to get a draft of Part 2 in progress, so as to avoid a long stretch of time between postings.

 

Thanks, Steve

2011-06-13 02:56:00Riccardo
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
97.83.150.37

Robert Rohde has a good SLR viewer here.

This is a view centered on Scandinavia.  Looks like at least the GIS and the WAIS sheets will both need to melt before Scandinavia becomes separated from Europe again.

2011-06-13 04:06:16
grypo

gryposaurus@gmail...
173.69.56.151

looks good to me.

2011-06-14 04:19:22
Andy S

skucea@telus...
66.183.170.32

Some of the links to papers towards the end of the article don't work. I.e., Frechette, Kienast, Muhls

I think that you may have overdone some of the hyperlinks. Although links to things like "savanna" and "isostatic rebound" are handy for non-specialists, I don't think your link to the IPCC is needed, for example.

The way you have done the figure caption is a little misleading by puting the letters (A,B,C etc) after the descriptions rather than before, You could fix this either by putting the letters first or by separating the subcaptions with semi-colons intead of commas.

There appears to be something of a contradiction between this

Overall, the Eemian climate in the Northern Hemisphere was characterised as being predominantly oceanic i.e. with relatively cool summers, comparatively warm winters and reliable precipitation

and this

In Alaska, summer temperatures were 1 to 2oC higher than today, but winters were 1 to 3oC cooler;

But perhaps Alaska was just an exception to the rule.

Otherwise it's very good.

2011-06-14 06:01:53
jyyh
Otto Lehikoinen
otanle@hotmail...
85.77.205.93

Good call of the isostatic rebound raising the Karelian Isthmuses, though nowadays similar sea level opening would require quite a bit of EAIS to melt too (f.e. the summit of the White sea canal is about at +90m, but it's not on the lowest possible route). Looks good.

(edited to correct the ASL... some other place said rise of 20 meters above Onega)

2011-06-14 06:29:31
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
97.83.150.37

Thumbey

2011-06-14 07:28:18
Steve Brown

brownsg@gmail...
80.177.115.133

Thanks for the thumbs and comments guys.  I'll do a tidy up and have a look at the broken links tomorrow.

WRT isostatic depression, it can be of the order of several hundred metres in the thickest and most massive parts of ice sheets.  For example, Northern Europe is still rising from the last glacial at a rate of 1 cm/yr and will continue to do so for a few thousand years yet! :-O

2011-06-14 08:42:01
Andy S

skucea@telus...
66.183.170.32

A rough rule-of-thumb using Airy isostasy (ie, Archimedes' principle) is that the ice (density 1) displaces the mantle (density 3.3) in an equal mass, so 1 km of ice depresses the crust into the mantle by about 300 metres. This is complicated by the fact that the crust has some flexural strength (so it bends like a sheet of plywood) and the flexural response is time dependent, so adjustment can take many thousands of years, as Steve said.

2011-06-14 09:10:17
michael sweet

sweetdreamfiji@hotmail...
96.228.135.17

Hansen estimates temperature rise of only 1C from the temperature peak of the LIG.  Can you explain the difference?  Is Hansen too low?  I am also frequently confused when it is said 2C higher temperatures.  Does that mean 2C higher than pre-industrial or 2C higher than 2011 temperatures?  There is almost 1C difference between those two.  Can you specify which of those you mean.

The basic idea of comparison to the LIG by someone who is well informed (like you) is great.  I think the series will be well worth reading.

2011-06-14 11:56:55
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Hi Steve,

I got your message about my Eemian illustrations. I'm eager to share, redraw, or let John Cook redraw anything I have. I could also have a go at redrawing the figure you're currently using, if John C's not already working on that.

Kind of an aside, but may be relevant: I'm revisiting my Eemian illustrations in light of 1) the Hansen paper that Michael Sweet cites and 2) a recent paper in 28 April Nature about the role of the southern hemisphere westerlies and the southern polar front regulating how much salt water leaks around South Africa to facilitate the AMOC. In other words, I hesitate to link the deglaciation of the Eemian to orbital forcing without a better understand of what triggers may be in the southern hemisphere.

thanks,

jg 

 

2011-06-14 21:18:05
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.4.254

Thumby too.

2011-06-14 21:25:40Redrawing pics
John Cook

john@skepticalscience...
121.222.9.229

I haven't been redrawing any pics related to this post so JG, you're welcome to. I don't see why your figures need redrawing - they already look awesome.

2011-06-15 00:15:36
jg
John Garrett
garrjohn@gmail...
108.23.2.2

Thanks John. Let me rephrase: by redrawing, I mean custom tailoring to Steve's article, if he would like. I picture a split globe view showing now and then, summarizing some of the comparisons cited in the article, e.g., sea level, opening of the Scandinavian strait, temperatures. But first, the figure should be cleaned up. So, I'll start on that. Steve, stop me if you have other plans for the figure.

jg (John Garrett)

2011-06-15 05:29:15STOP THE PRESSES!!
Steve Brown

brownsg@gmail...
80.177.115.133

@John G - please continue with producing a comparative illustration - a great graphic beats any words I can muster. :-)

@John C - I'm OK with holding off posting part 1 until JG is ready.

@michael - The ~2oC to 3oC global temp you often see quoted for the Eemian is mainly based on AO-GCM model studies that start with the predicted orbital configuration and estimated GHG forcings of the period, though actual evidence is only regional.  This is covered in chapter 6 of AR4 WG1 and also papers such as Crucifix & Loutre (2002) and Kaspar et al (2005).  The comparison is typically with the present day i.e 2000 - 2007 (comparisons with pre-industrial are often for CO2).  There are a great many proxy reconstructions for the period that show average summer temps from 4oC to 14oC above those today for individual sites - mainly at high northern latitudes.  The figure in Hansen's paper that I think you got your 1oC difference from is based on a delta-18O proxy of deep ocean temperature and is consistent with the estimates provided in AR4.  Palaeoclimate is not a precise science and I would say that Hansen's estimate is pretty consistent with picture thats been building.

2011-06-15 05:43:07Confirm use of this figure and I'll redraw the whole thing
jg
John Garrett
garrjohn@gmail...
108.23.2.2

Steve,

I redrew one panel (See INSOLATION colum) in your figure, and I'd like to show it to you before I redo the whole thing and polish it. I want to confirm that you want to use this figure, considering that a goal here is to simplify and not show thorough data. That said, I think we can simplify that figure with highlighting, removing unnecessary parts, and replacing abbreviations. (or, I might be able to put the relevent parts into the comparative illustration). If you use this figure, consider the vertically oriented version I've put here with a 570 pixel reference for page formatting. Let me know what to do.

vertical layout with one panel change

original orientation

jg

2011-06-15 20:14:46These two sentences seem to contradict each other
James Wight

jameswight@southernphone.com...
112.213.161.21
  • “Overall, the Eemian climate in the Northern Hemisphere was characterised as being predominantly oceanic i.e. with relatively cool summers, comparatively warm winters and reliable precipitation”
  • “This strong seasonality, with warmer summers and colder winters characterises the Last Interglacial climate”

I notice Andy has already mentioned this but it hasn’t been corrected.

2011-06-16 04:28:07Fine-tune the wording of the final paragraph
John Hartz
John Hartz
john.hartz@hotmail...
99.95.221.238

The final paragraph now reads:

So here we have a warmer, wetter world than today, with higher sea-levels, smaller ice-sheets, but a level of atmospheric CO2 much lower than today.  Does this mean that CO2 is not to blame for global warming after all? Climate always changes and we have nothing to worry about, right?  We'll look into these questions and more in this continuing series of posts on the Last Interglacial climate......

I suggest rewording it along these lines.

So the Eemian was a warmer, wetter wrold than today's with higher sea-levels, smaller ice-sheets, but with a level of atmospheric CO2 much lower than today's. Does this mean that incressing levels of CO2 do not cause global warming after all? The climate always changes and we have nothing to worry about, right?  We'll explore the answers to these questions and more in this continuing series of posts on the Last Interglacial climate......

2011-06-16 06:18:20
Steve Brown

brownsg@gmail...
80.177.115.133

@John G - On further consideration, I think we should drop that proxy reconstruction diagram.  It will just confuse non-specialists.  In addition to your comparative illustration, what would be helpful is some sort of geological timeline diagram that shows where the Eemian is in context - something that Badgersouth suggested previously.  For part 2 of the series I'd like to use the orbital forcing illustrations you have on your blog.  Thanks! :-)

@James / Andy - I think I've tracked down the apparant contradiction. The first statement appears to relate to the late Eemian, while the 2nd relates to the climatic optimum.  I'll resolve the wording appropriately.

@Badgersouth - suggestion accepted.  The subtle change in wording is more accurate.  Thanks!

2011-06-16 12:12:52
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Steve,

I agree with dropping the proxy reconstructions, especially since the pollen data at the bottom panel is illegible to me. I'll do a timeline and share it.

jg

(I couldn't resist finishing the proxy diagram. You can see it here: proxy diagram)

2011-06-17 01:12:06
jg
John Garrett
garrjohn@gmail...
108.23.2.2

Hi Steve,

I sketched a timeline. Let me know if you need any part of it fixed or embellished in any way.

PNG format:

timeline in png

JPG format:

timeline in jpg

 

2011-06-17 02:14:34
Steve Brown

brownsg@gmail...
91.220.25.25

JG - those timelines are perfect.  The redrawn proxy reconstruction diagram is a remarkable improvement.  I think what we can do is maybe add it to the final summary post with a link back to the original Kukla et al (2002) paper.  BTW the illegible word you couldn't make out is "Ribains", which is the site in France that the pollen cores were taken.

I'll get to work on updating part 1 on Saturday.

Thanks, Steve

2011-06-17 03:00:35
jg
John Garrett
garrjohn@gmail...
108.23.2.2

Steve: I should have some variations of the comparitive diagram ready for you on Sat or Sun too.

If you use the proxy diagram, consider having me flip some of the graphs so that proxies for high and low temperatures will rise and fall. For example, after I rotated the diagram to fit the 570 pixel limit, I noticed that warm periods are shown as lower and cold as higher on the Vostok proxy graph.

jg

2011-06-18 05:16:24
Steve Brown

brownsg@gmail...
80.177.115.133

JG - How would you prefer to be referenced in the post: jg or John Garrett?  Do you want a link back to your blog or website?

2011-06-18 12:03:58
jg
John Garrett
garrjohn@gmail...
96.229.221.76

Steve: "jg at brightstarswildomar" is fine. I'm not eager for attention, nor do I want to draw people away from your post.

I did a sea level sketch comparision; use it if you like. I'll take the text bubble out, but thought I'd share in its uncensored form:

sea level comparison of Eemian estimates to current level

2011-06-19 02:27:29
Steve Brown

brownsg@gmail...
80.177.115.133

OK, I've updated the part 1 post with some corrections to wording, removal of the proxy reconstruction diagram and addition of jg's timeline.  link here.

I might be ready to post a draft of part 2, which covers orbital forcing by tomorrow.  I'll start a new forum thread for it too.

2011-06-19 11:39:12
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.102.37

Think you're ready to post part 1, Steve?

2011-06-21 05:51:43
Steve Brown

brownsg@gmail...
80.177.115.133

I think part 1 is good to go, Dana.  The illustrations that jg is working on will be better suited to the follow up parts, so no reason to delay part 1.

Thanks!

2011-06-22 00:46:11illustrations
jg
John Garrett
garrjohn@gmail...
108.23.2.2

I agree. Don't wait for me, but I did a sketch of the scandanavian region if you want to use it. I'm putting it into a larger diagram of comparisions, so no need to use in part one. I'm curious if it agrees with you on the approximate shape of the ocean in this region at this time:

scandavia as an island 

2011-06-22 05:33:30
Steve Brown

brownsg@gmail...
80.177.115.133

jg - that sketch is excellent, though we'll need to make clear that it's just a possible scenario.  Look forward to seeing the rest of the diagram!