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Asten 2012

A new discussion paper at Climate of the Past presents a new estimate of climate sensitivity from proxy records (H/T Bob Carter). The figure it comes up with is 1.1±0.4°C. This is in line with the Forster and Gregory estimate, and far below the IPCC's figure.

Climate sensitivity is a crucial parameter in global temperature modelling. An estimate is made at the time 33.4Ma using published high-resolution deep-sea temperature proxy obtained from foraminiferal δ18O records from DSDP site 744, combined with published 5 data for atmospheric partial pressure of CO2 (pCO2) from carbonate microfossils, where 11B provides a proxy for pCO2. The pCO2 data shows a pCO2 decrease accompanying the major cooling event of about 4 C from greenhouse conditions to icecap conditions following the Eocene-Oligocene boundary (33.7 My). During the cooling pCO2 fell from 1150 to 770 ppmv. The cooling event was followed by a rapid and huge 10 increase in pCO2 back to 1130 ppmv in the space of 50 000 yr. The large pCO2 increase was accompanied by a small deep-ocean temperature increase estimated as 0.59±0.063 C. Climate sensitivity estimated from the latter is 1.1±0.4°C (66% confidence) compared with the IPCC central value of 3 C. The post Eocene-Oligocene transition (33.4 Ma) value of 1.1 C obtained here is lower than those published from 15 Holocene and Pleistocene glaciation-related temperature data (800 Kya to present) but is of similar order to sensitivity estimates published from satellite observations of tropospheric and sea-surface temperature variations. The value of 1.1 C is grossly different from estimates up to 9 C published from paleo-temperature studies of Pliocene (3 to 4 Mya) age sediments. The range of apparent climate sensitivity values available 20 from paleo-temperature data suggests that either feedback mechanisms vary widely for the different measurement conditions, or additional factors beyond currently used feedbacks are affecting global temperature-CO2 relationships.

Climate of the Past has an open review process. I imagine this will be, ahem, colourful.

The paper is here. Discussions will be posted here.

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Reader Comments (38)


Do we whistle that bit in the middle?

Oct 6, 2012 at 9:19 AM | Unregistered CommenterJames Evans

Should the link to comments be:

Oct 6, 2012 at 9:34 AM | Unregistered Commenter@HG54

A splendidly short paper, low on waffle and high on information. It will be panned, but at least it shows that there are a growing number of scientists ready to put observations over models and say so. The more the merrier.

Oct 6, 2012 at 9:42 AM | Unregistered Commentergeronimo

Geronimo: Why do you think it will be panned? What is wrong with it?


Oct 6, 2012 at 10:32 AM | Unregistered CommenterChris Hope

Chris if true it takes the "catastrophe" out of global warming, that's what's wrong with and there are too many vested interests in keeping it in. The Team will be mobilised and will make every effort to discredit it.

Oct 6, 2012 at 10:41 AM | Unregistered Commentergeronimo

geronimo - how have you grown so cynical? I expect the paper to be warmly embraced by all sides of the debate and for the government to give me my money back with a note of apology.

Oct 6, 2012 at 11:00 AM | Unregistered CommenterAlan Reed

18O proxy data is fairly good at temperature but temperature alone does not drive weather/climate, heat does which is reliant on water content as well as temperature. How the water content data is found I have no idea but there might be a proxy out there.

Oct 6, 2012 at 11:13 AM | Unregistered CommenterJohn Marshall

Chris Hope et al.,

The author claims to estimate climate sensitivity to within 0.4K from a single borehole measurement from the bottom of the ocean. This would be truly amazing!

In summary, they claim they can measure global temperature change to within a couple of tenths of a degree from a single borehole proxy measurement at the bottom of the ocean from 33 million years ago. They assume that CO2 is the only driving factor for the observed change, ignoring solar, orbital, volcanic, methane etc factors. They assume no uncertainty in their base level of CO2. It is completely unclear how they use the ranges quoted for their S1 and S2 factors in Eqn. 4 to derive the uncertainties.

I simply cannot believe their estimate of +/- 0.4K.


Oct 6, 2012 at 11:24 AM | Unregistered CommenterEd Hawkins

Alan Read: I've got this bridge I'd like to sell...

(kidding! Just kidding!)

Oct 6, 2012 at 11:43 AM | Unregistered CommenterOtter

Oh noes! Its been panned.
John Marshall says:
October 6, 2012 at 2:40 am

It is not temperature that is important but heat content which varies at a given temperature with water content. It is heat that drives weather/climate. Whilst 18O proxy data is good for temperature it does not relate to heat content.
Go back and recalculate.

Oct 6, 2012 at 12:20 PM | Unregistered CommenterAlan Reed

"Climate sensitivity estimated from the latter is 1.1±0.4°C (66% confidence) "

I am currently re-reading Taleb's "Black Swan" and he has much to say on this sort of result.

It is very strange how people in any field are capable of being perfectly aware of numerous studies that come up with very different answers, and not being able to see quite clearly that while the estimated central value may derive from the data, the confidence interval cannot.

Realistically they should be saying that there is close to zero confidence that this particular study is any more accurate than any other. 66% is absurdly high. 95% is a joke. The simple existence of studies with high confidence levels and intervals that do not overlap with this result should reduce the confidence in this result.

Now if they'd said "Climate sensitivity estimated from the latter is 1.1±0.4°C (6% confidence) " that might be closer.

Oct 6, 2012 at 12:24 PM | Registered Commentersteve ta

Geronimo: Why do you think it will be panned? What is wrong with it?

Putting "Big Green"out of Business.

Oct 6, 2012 at 12:35 PM | Unregistered Commenterjamspid

Right, I can't even reproduce his error bars using his own numbers.

The central estimate is 1.1, but I reckon the 66% likelihood ranges should be 0.9 to 1.6 - and this is a highly skewed distribution. It may depend on what he assumes for the uncertainties in S1 and S2 - the paper doesn't say, but I used uniform between the ranges he quotes, but this doesn't really seem right either, or matter very much.


Oct 6, 2012 at 2:03 PM | Unregistered CommenterEd Hawkins

Ed, isn't the issue that deep ocean temperatures are simply not a good proxy for global mean surface temperatures? Take the last glacial period - cooling of 5 C at the surface, but much less in the deep ocean. And that's even before you get to the uncertainties in the co2 change or dating...

Oct 6, 2012 at 2:09 PM | Unregistered CommenterFrank

Frank - yes I agree. He uses the S2 parameter to try and represent this type of uncertainty, but I don't believe it is done adequately. [Also see my other concerns in a previous comment!]

Oct 6, 2012 at 2:28 PM | Unregistered CommenterEd Hawkins

If only we had land , sea , and ice albedo proxies for the Eocene-oligicene interlude , to go with the b and O systemics.

Oct 6, 2012 at 3:03 PM | Unregistered CommenterRussell

"In summary, they claim they can measure global temperature change to within a couple of tenths of a degree from a single borehole proxy measurement at the bottom of the ocean from 33 million years ago."

Why, that sounds exactly like the kind of thing you climatologists do all the time.

Only you roll out these 'skeptic-like' objections against work that doesn't play well with the "strategy of supporting the robustness" (aka data and claims that don't support alarm).

If a higher sensitivity were to be true, no single borehole should reflect anything else other.

Oct 6, 2012 at 3:41 PM | Registered Commentershub

The link you use for the discussion is the link for the paper, not the discussion.

The discussion is here: Looks empty to me so far.

You can delete this after fixing the link.

Oct 6, 2012 at 3:55 PM | Unregistered CommenterAtheoK

"In summary, they claim they can measure global temperature change to within a couple of tenths of a degree from a single borehole proxy measurement at the bottom of the ocean from 33 million years ago."

Ed, you're right of course, but where do you stand on using one tree in Yamal for the 20th century, or bristlecone pines to produce a 1000 year temperature record, when NAS says they're unreliable, or using upside down data from Tijander varves and ignoring critics who point this out to you?

Oct 6, 2012 at 4:57 PM | Unregistered Commentergeronimo


Also, Ed might like to give his views on a single borehole on the WAIS Divide being used by Orsi et al (2012) to show warming in the Antarctic as a whole whilst also apparently “confirming” Steig et al (2009).

Whilst I have no doubt he is correct on the paper discussed on this thread and his points are valid, it will be interesting to see if he has the courage to apply the same standards of critique to many of those, shall we say, more “robust” papers, if you know what I mean ;)

What say you Ed?

Oct 6, 2012 at 5:56 PM | Registered CommenterLaurie Childs

geronimo, Laurie Childs (LC), shub:

Firstly, I am not an expert on palaeoclimate. Tamsin may be better placed to answer some of these type of questions if she is reading this thread. However....

IMHO, a time series from a single location tells us little about GLOBAL climate. I have discussed this for instrumental records, although not in detail, in a freely available article for Significance magazine ( The reason this Asten paper has been much discussed is that it has been picked up by blogs such as BH and WUWT. My views on the presentation of uncertainty would be the same if the sensitivity derived was 6K, but I probably wouldn't have heard about it. COPD is not a journal I read regularly.

Orsi et al. - from a reading of the abstract only - they are using a single (land?) borehole as representative of a small region of Antarctica (the WAIS Divide). This is definitely not the same as extrapolating from a single deep ocean temperature to surface global mean temperature, as I hope you would agree? And, they are not trying to extract a global climate sensitivity from this one measurement - they are using it as part of a wider discussion considering other observations.

As for Yamal, bristlecones, Tijander etc - I see a lot of arguments, counter-arguments, disagreements, intense and sometimes nasty discussions but I do not know enough of the details to comment further. However, the same principles that apply to needing lots of locations also applies to proxies - I think several different proxies are required to give confidence in any reconstruction, and the sensitivity to each source should be tested rigorously.


Oct 6, 2012 at 9:13 PM | Unregistered CommenterEd Hawkins

PS. Open science is a good thing! I am an author on an 'open discussion' paper in review at the moment, so feel free to read and (constructively) comment...


Oct 6, 2012 at 9:34 PM | Unregistered CommenterEd Hawkins

Oct 6, 2012 at 9:34 PM | Ed Hawkins-As for Yamal, bristlecones, Tijander etc - I see a lot of arguments, counter-arguments, disagreements, intense and sometimes nasty discussions but I do not know enough of the details to comment further.

Many of these "arguments" go right to the very core of the CAGW meme..yet so few people in their respective and relevant fields have managed the time to actual learn about them.?
How is that possible.???
It isn't of course..
I am just being kind..
The straw man "arguments" angle you are taking was a delightful way of muddying the waters..
Nice move.. :)

Oct 6, 2012 at 10:26 PM | Unregistered CommenterMike Williams

"Amazing.. Many of these "arguments" go right to the very core of the CAGW meme"

Ha. The amazing thing is that you really think this. You are vastly overstating the importance of reconstructions as a reason for concern about global warming, and when you get evidence (such as Ed's response) that it doesn't play much role in many scientists thinking, you think that *they* are confused. Double Ha.

Consider, just for a second, that you have actually got this wrong, and that the whole crusade against the paleo-climate proxy crowd is a complete red-herring....

Oct 6, 2012 at 11:39 PM | Unregistered CommenterFrank

At least the Brazilians seemed to like using the outer neritic bathyal benthic foram Cibicidoides for paleotemperature estimation -

'In this study we have compared the oxygen isotopic composition of two genera of benthic foraminifera (Uvigerina and Cibicidoides) from core-top samples with modern oxygen isotopic composition of seawater (δ18Ow). Based on a new relationship between δ18Ow and salinity for the mid-latitude western South Atlantic, we estimated the isotopic composition of equilibrium calcite (δ18Oeq) using two different equations: (1) O'Neil et al. (1969), modified by McCorkle et al. (1997) and (2) Kim & O'Neil (1997). When using (1), the small difference between δ18Oeq and δ18O of Uvigerina suggests that this genus precipitates its shell close to equilibrium with ambient seawater. The δ18O Cibicidoides data are 0.82 ‰ lower than the predicted (equilibrium) oxygen isotopic composition. Conversely, using (2) the Cibicidoides δ18O data show excellent agreement with the oxygen isotopic composition predicted from δ18O and water temperature while Uvigerina δ18O data are 0.69 ‰ higher than predicted oxygen isotope equilibrium values. Based on the evidences presented here and on the results from previous studies we suggest using the genus Cibicidoides and applying Kim & O’Neil’s (1997) equation for down-core paleotemperature investigations. In the absence of enough Cibicidoides specimens we suggest using Uvigerina δ18O data and applying a correction factor of -0.69 ‰.'

Oct 7, 2012 at 12:23 AM | Registered CommenterPharos

Just a thought ...

I believe that the concept of climate sensitivity relies on the assumption that there is a unique functional relationship between CO2 concentration and average global temperature, other things being equal.

But what if this is not necessarily true at all? Assume instead that the global temperature is largely independent of CO2 concentration in the air.

If something unrelated to CO2 warms the climate system there will still be an increase in CO2 concentration in the atmosphere, for example, from the release of CO2 by the oceans. Conversely, if the temperature falls, there will be less CO2 in the air because the oceans can now dissolve more. (It is accepted that CO2 is sensitive to temperature.)

However, according to the present argument, if atmospheric CO2 concentration increases for some reason other than a rise in temperature, there will be no resulting temperature change. (It is assumed that temperature is not sensitive to CO2.)

Since the physics is apparently not established beyond all doubt and the phenomena associated with CO2 dissolved in water and CO2 mixed with air are completely different, isn’t it logical to go no further than:

Global temperature increments may cause atmospheric CO2 increments, but
atmospheric CO2 increments need not cause global temperature increments.

Could this be why there are differing observational estimates of “climate sensitivity”?

Oct 7, 2012 at 12:33 AM | Unregistered CommenterMark Well

Would Pharos please illuminate why, habitat depth being equal , 18O differentiation should vary much metabolically from foram to foram ?

Oct 7, 2012 at 3:38 AM | Unregistered CommenterRussell

Frank..The reconstructions were just one of the litmus tests of the robustness of the science.
If they were not "important" why does/did "The Team" spend so much time refusing to show the raw data and fight any corrections.??
In Frank world..they didn't have to.
But in our world.."The Team" had too for a good reason.
Most people can work out why.
I never said Ed was "confused"..
I am aware that the robustness of the selection and use of raw data does not play much of a role in climate science..unlike other areas of science.
Thanks for mentioning it though..!!
I was pointing out it was handy to not be aware of some of the major problems in the data in a specific field.
Ed has the grace to admit he doesn't know anything about these problems..
You on the other hand Frank.. :)
Its amusing to hear that if people point out problems with proxies..thats really means ="a red herring". :)
What a weird view of science you chaps have..
As for the Ha`s..and double ha`s..?
Your kidding right.? :)

Oct 7, 2012 at 4:00 AM | Unregistered CommenterMike Williams

The Piltdown Mann's Crook'd Hockey Stick
Scooped froth, to you the scum will stick.

Oct 7, 2012 at 4:48 AM | Unregistered Commenterkim

Frank: "Ha. The amazing thing is that you really think this. You are vastly overstating the importance of reconstructions as a reason for concern about global warming, and when you get evidence (such as Ed's response) that it doesn't play much role in many scientists thinking, you think that *they* are confused."

I'm not sure where to start you're so far off-beam, but I'll try with the importance of the numerous false hockeystick reconstructions. Firstly, of course, they have nothing to do with science, they are political. To persuade people that the 20th century was unique they had to "get rid of the medieval warm period". The hockeystick did this and was the poster child of the TAR. I won't go into it any more because if you want to get into the detail I'd suggest you read a book called "The Hockeystick Illusion" the author's name escapes me, but it is the best science book you're ever likely to read.

As it happens though, the hockey stick was reliant upon a single set of bristlecone pines situated in SW USA to eradicate the MWP and show the strong uptick at the end of the 20th Century. All the hockeysticks that have followed have either used Graybill Pines as they're known, or the Tijander varves, upside down of course. The exception to this is are papers that use pine trees in Russia in particular the Briffa paper, Briffa used 5 Yamal pines for the 20th century, mysterioiusly ignoring 34 nearby pine trees which gave no uptick in the 20th century.

The importance of the hockeystick isn't in the science of course, it's in the fright it can give to people, and the removal of evidence of temperatures in excess of today's during the MWP when there was no significant human activity.

Our point to Ed was that all these papers, accepted as gospel truth by the 97% of scientists who are ardent adherents to the theory of CAGW papers, use one location to generate a global temperature record, the Greybill pines, for Mann et al and various other members of the self-named "Hockey Team", the upside down varves by Mann et al, and the Yamal pines by Briffa. So, as Ed was quite quick to point out, and rightly so, that this paper relied upon one location to formulate a global view, for which I have to ask him another question, we, on this blog wondered why he, and the other 96.9% of scientists hadn't pointed this same flaw out in the famous Hockeystick reconstructions. Because he's right, and it's what sceptics have been saying since these hockeysticks first appeared they cannot represent global temperatures. (I'm guessing you haven't looked into this very much because of your ignorance of the issues, but Mann defended the use of the Greybill pines on the ground of "Teleconnection" which is, from what I can make out, a form of ESP enjoyed by bristlecone pines communicating across the globe. And he must know because he's a "scientist").

Oct 7, 2012 at 7:40 AM | Unregistered Commentergeronimo

Ever since it became obvious that the hockey stick was broken, the warmist party line has been to claim that it wasn't important, nobody ever thought it was, etc etc.

Anyone peddling that one on this blog of all places is probably trolling.

Oct 7, 2012 at 9:00 AM | Unregistered CommenterNW

Last night I dreamed that Dr Mann had fallen under a bus. I came here to be reassured.

Oct 7, 2012 at 9:06 AM | Unregistered CommenterAlan Reed

"I see a lot of arguments, counter-arguments, disagreements, intense and sometimes nasty discussions but I do not know enough of the details to comment further."

This again?

Dr Hawkins,
I work in a field quite removed from the climate as possible. However, I have followed key questions sceptics raise and they are really of a general nature, not quite unlike those you ask about this Asten et al paper.

Oct 7, 2012 at 11:02 AM | Registered Commentershub

" feel free to read and (constructively) comment..."

You know you pulled a Wilson there with that 'constructively', right?


Oct 7, 2012 at 11:04 AM | Registered Commentershub

Editing point:
"mysterioiusly ignoring 34 nearby pine trees which gave no uptick in the 20th century."

Sorry, getting mixed up the 34 trees showed a MWP, none of them show an uptick at the end of the 20th century, hence we've had to "hide the decline".

Oct 7, 2012 at 11:43 AM | Unregistered Commentergeronimo


You may find an answer here

But it surprises me not that a genus named Uvigerina might be inclined to take umbrage and thus be somewhat unobliging.

Oct 7, 2012 at 9:32 PM | Registered CommenterPharos

A mining geophysicist, comes along, gets openly available data, (google James Zachos Compilation Curve Data and you should be able to get it I think), looks at data from two drill sites (the diameter of these holes is about 15cm), from 33.8 to 33.0 million years ago (an 800,000 year interval)n across a deeply studied and very interesting palaeoclimatic boundary during the Cenozoic. Work by people such as Paul Pearson and many others looks at the changes that occurred here, with modelling support from the Rob DeConto. The E-O is a very complicated boundary with a number of key oceanographic changes as well as CO2 and other trace gases. It is fascinating work and really interesting to look at and it is important to understanding the climate system of the Earth.
The del18O signal measured here is from benthic forams, and as a result is giving the measure of the deep water or bottom water temperature. Climate sensitivity is by its definition the short term century scale changes in the climate system. So, this paper is attempting to derive climate sensitivity, from a signal that is changed on the region of thousands of years (ten times slower than climate sensitivity) with a resolution (or frequency of data points) of 10-15,000 years, i.e. he has one temperature measurement for every 10,000 year interval. This is not a problem for palaeo-climate studies, as these big changes have happened over occasionally a million years or so, but to derive a fast forcing in the climate.....?
Ultimately, the E-O is a really interesting time period to study, it holds clues as to some of the ways our climate changes on natural timescales, it is the time of the formation of the East-Antarctic Ice Sheet, which has survived ever since, but you can not derive climate sensitivity, from benthic del18O measurements, over a resolution of 10,000 years.

Oct 8, 2012 at 11:01 AM | Unregistered CommenterJohn

Looking forward to the reports by Roger Harrabin, Louise Grey and their friends.

Oct 8, 2012 at 2:41 PM | Unregistered CommenterJohn Page

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