Bishop Hill IPCC to admit MWP warmer?
Aug 21, 2013 Climate: MWP The Washington Post has further leaks from the IPCC's Fifth Assessment Report. They can be seen here.
The conclusions about the millennial temperature reconstructions...
The 30 years from 1983-2012 was very likely the warmest 30-year period of the last 800 years.
are interesting when compared to what was said last time round:
Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1,300 years.
The shift from 50-year periods to 30 years periods makes direct comparison difficult, but this does seem to suggest something of a reining back. The Medieval Warm Period, located by AR4 in the centuries spanning the end of the first millennium, is now apparently accepted as probably being warmer than the current warming, at least if the Washington Post is to be believed.
Reader Comments (59)
First, for a comparison we need to know if the AR5 claim is global or just for the Northern hemisphere.
Second, you seem to be suggesting that the "correct" answer is that the MWP was warmer. Is this the case, and if so could you say which reconstruction you are relying on to support that?
Wouldn't it be more defensible would be to say that "the MWP may have been warmer"?
The MWP was warmer in the FAR - when certainty was rather lower. Of that we may be quite sure.
Most of these leaks are not really new.
Recall that Alec Rawls leaked the whole of the AR5 draft in December 2012. That version of the SPM contained almost exactly the same statetement:
Similarly, the attribution inflation from 90% ('very likely') to 95% ('extremely likely') was there in the previous leaked draft. This all suggests that the final version is unlikely to be significantly different from the version leaked in December.
( Responding to BH below, yes, the version being discussed now is probably a later version than the Dec one, but not quite the final one coming out at the end of Sept, and the close similarities suggest that the changes being made are very minor).
There is a whole section of CO2Science dedicated to showing the MWP was warmer with links to actual papers, data etc
Isn't that what is being stated here?
Paul Matthews
Yes, I'm kind of assuming that the WP article is based on the final report and not the draft, but that may not be the case.
Indeed. Increasing the kinetic resolution (as in, for example, shortening the observation period from 50 to 30 years) may well allow the disingenuous to claim that no similar period of greater warmth was detected in the past xyz years.
Et voila! With one bound they were free! If something can't be detected by your chosen method, then it doesn't have to be discussed. A bit like possibly higher previous concentrations of CO2 that may have been smoothed out in the ice cores.
Of course it is also possible that I am being too cynical, and there are honest reasons for presenting the data this way (inconsistent incompetence being one possible honest reason).
Cherries don't come any more carefully selected than that.
What would Sir Paul Nurse say?
We are truly lucky to be alive during such a benign period of warmth. Let's hope it continues for another 30 years, and that will see me through. With the cost of energy going through the roof, due to successive Government's misguided (insert alternative adjective) policies, we need all the warmth we can get.
It ain't 2007 or 2009 any longer. From notorious Justin Gillis:
Remember, we started from a position where little of the above would be mentioned at all...
"The shift from 50-year periods to 30 years periods makes direct comparison difficult, ......."
Objective achieved!
Remember the notorious statement by a member of "the Team"?
“We have to get rid of the Medieval Warm Period.”
http://stevengoddard.wordpress.com/2011/05/11/“we-have-to-get-rid-of-the-medieval-warm-period-”/
For years those climatologists who back the "consensus" have been claiming that the medieval warm period was a localised event affecting northern Europe and the north Atlantic. Presumably the apologies for getting it wrong will soon be forthcoming?
Reads to me as they have got rid of the MWP - by avoiding its dates.
I am surprised by this concession. The MWP is the achiles heal of manmade global warming since,
1. It gives an indication of the strength of natural variabily, and demonstrates that natural variability is such a powerful forcing that it can produce temperatures as warm or warmer than today.
2. If natural variability is powerful as indicated above, it makes the conclusion that the only explanation for the late 1970s to late 1990s warming (don't forget that temperatures fell post 1940 and have been in statsis this century) is CO2. In the light of the existence of the MWP at a temperature as warm as today, that conclusion is simply untenable.
3. Given the above, it is impossible for there to honestly be 95% consensus that humans are responsible for the recent warming (ie., the period late 1970s through to late 1990s). Obviously, humnans cannot be responsible for warming between 1940 and say mid 1970s because there was no warming during that period, indeed it was cooling. Humans cannot be responsible for warming since the late 1990s since there is no statistical warming as from that time.
If that concession is left to remain in the final version of the report, the entire report is undermined and compromised by the concession. Readers should perhaps bear in mind the comparison between the warming during the first half of the 20th century and the warming during the second half. See the WUWT article on this
http://wattsupwiththat.com/2013/08/20/when-somebody-hits-you-with-that-new-ipcc-is-95-certain-talking-point-show-them-this/#comments
Roy (Aug 21, 2013 at 9:54 AM) rightly points outs " Remember the notorious statement by a member of "the Team"?
“We have to get rid of the Medieval Warm Period.”
http://stevengoddard.wordpress.com/2011/05/11/“we-have-to-get-rid-of-the-medieval-warm-period-”/
One can understand why the Team held that view. It is vital to the cause that there be no significant MWP since its existence completely and utterly destroys the claim that the only explanation for the late 20th century warming must be CO2.
That does not, of course, necessarily mean that CO2 does not warm, or indeed is not entirely responsible for the late 20th century warming, but it does mean that the claim that the only explanation for the late 20th century warming is CO2 must be wrong.
Natural variation is now the crux of the game. It is the only viable explanation for the stall in rising global temperatures and the longer these temperatures continue to stall climate scientists will be forced to concede the greater its significance in detrmining climate. Likewise, it is the 'thorn in the side' of Climate Sensitivity and is the reason why there have been some recent concessions towards lower sensitivity.
Natural variation will be seen to be the battle ground.
Paul, Andrew,
These articles are indeed based on the final draft of the SPM that was only sent to the governments in June (the review closed early August). Based on the comments the SPM will be modified and then the SPM will be discussed in a closed session (for the media) line by line end September in Stockholm.
I now learned that governments also received the final draft (Note: I mean one draft later than the SOD that was seen by the expert reviewers) of the chapters in June, together with the final draft of the SPM.
So governments are able to see the final final draft of all the chapters, expert reviewers are not!
This is problematic because there are always huge changes between the SOD and the final report.
See also my short post http://www.staatvanhetklimaat.nl/2013/08/21/full-ipcc-report-will-be-released-shortly-after-spm-on-monday-30-september/
Marcel
Whilst I agree the variation is due to natural causes, not least because there is clear evidence of cycles,
WUWT has a story about change being to clean air act
http://wattsupwiththat.com/2013/08/19/shocker-global-warming-may-simply-be-an-artifact-of-clean-air-laws/
unintended consequences? funny though
Richard Verney - I'll channel my inner Climate Scientist to reply that if the climate has changed in the past by a certain amount due to whatever cause, then it is possible that we might be the cause for it changing by similar or even larger amounts again in the future. So a warmer MWP doesn't necessarily mean AGW isn't happening.
This is perfectly plausible scientific reasoning that can be investigated, noting eg if there is anything different now than in the MWP, etc etc. So the fact that the usual suspects tried to delete the MWP from history doesn't imply that they knew it would have destroyed the AGW hypothesis.
It just mean they (a) didn't think AGW had solid scientific grounds, and (b) thought it was unable to withstand the existence of the MWP; and (c) weren't talking scientifically when they attributed 90% likelihood to AGW, in 2007.
The idea that the new 95% figure is suddenly scientifically sound, is beyond risible. Perhaps I should just add it to my list of AGW miracles.
As we are unable to empirically verify reasonably accurate temperature measurements prior to the beginning of the CET in 1659 it is interesting to note an example of natural variation within that record and prior to the beginning of the industrial revolution.
Between the years 1739-1741 the average monthly temperature went from 9.20 deg C in 1739 to 6.84 deg C in 1740 and recovered to 9.30 deg C in 1741. This was probably as a result of the eruption of Mount Tarumae in 1739. In terms of decadal activity it equates to -23.6 deg C/decade to 24.6 deg C/decade and can be considered a range of natural variation without the effect of man-made CO2.
Bearing in mind that since the beginning of the CET in 1659 to 2012, the average monthly temperature has only risen 0.87 deg C in 353 years (0.0246 deg C/decade. This example shows what needs to be learned about the effect of volcanic eruptions and the possible large range of natural variation.
Ross Mckitrick has found evidence of man made warming which caused temperatues to rise by 1C in about 1 year (1990 to 1991).
This 1 year jump of 1C is larger than the "statistically significant" rise of 0.8C claimed by met office
http://www.uoguelph.ca/~rmckitri/research/nvst.html
curiously this corresponded with approximately 1/2 the weather stations in world stopping being used
Seriously? After all the methodological scrutiny given to temperature reconstructions over the last decade, you can't see the weaknesses in their analysis? I would have thought that even a casual reader of this site would be able to pick it apart pretty easily.
We all find it easier to accept evidence that backs up our current beliefs. Try looking at the methods used by CO2Science and ask yourself what you would say if those methods had been used to show the Current Warm Period was warmer than the MWP.
Especially together with the headline of the original post, this is claiming that 'unknown' = 'probably warmer'. That is not justified. Maybe we can put some error bars on what we think the MWP temperatures were, and maybe the IPCC has done so. I don't see any evidence in the Washington Post quote that suggests they have done this, so I don't see how you can claim the IPCC have made a quantitative claim about MWP temperatures ('probably warmer').
If we put the IPCC to one side, what is the best evidence about MWP temperatures. Is the CO2Science reference the best we can do?
"If we put the IPCC to one side, what is the best evidence about MWP temperatures. Is the CO2Science reference the best we can do?"
We could always wait for barley being harvested in Southern Greenland again. It ain't happened yet.
Moving the goalposts is endemic amongst those of an 'alarmist/warmist' persuasion...
sherlock1
A politician once complained that he hated having scientists on committees. Whenever new evidence came in, they changed their views.
He, of course, had to stick to his original opinion regardless of the evidence. If he changed he was accused of doing a u-turn!
How quickly things change.
It seems only a few months since Marcott et al was attacked on Bishop Hill for showing temperatures 1000 years ago that were warmer than the 20th century.
http://content.csbs.utah.edu/~mli/Economics%207004/Marcott_Global%20Temperature%20Reconstructed.pdf
Now the straw man is that temperatures were warmer, but the scientists refused to accept it!
The agricultural practices of a few thousand people on the edge of Europe may well tell us interesting things, and be an interesting topic of study. Call me a skeptic, but on their own I doubt they are a reliable proxy for global temperatures with subdecadal resolution.
Surely, if we want to use that sort of evidence we must not only study it as carefully as we can but, crucially, integrate it together with all the other available evidence. It seems to me that it is this step that is difficult, and that has come under legitimate scrutiny when claims of unprecedented warming are made. To properly characterise the MWP, what the pattern of temperature in space and time really was, that process has to be carried out. So far as I'm concerned a vague reference to a barley harvest in a single location, on it's own, doesn't get me far towards understanding this.
A global medieval warm period that is warmer than the thermal maximum of the 1940s on a decadal or multi-decadal scale is a sceptic's myth first propagated by the IPCC. Since the Stockholm Geological Conference of 1910 when the idea of a period in the Holocene warmer than 'the present' was first proposed on good scientific grounds there has never been such a school of thought. Show me the papers!
That graph in FAR that keeps popping up on skeptical posts...it was inserted where it did not belong. It was substituted for another graph. It does not reflect the text of FAR nor the views of anyone at the time. Nor the views of the skeptic Lamb who provided so much of the evidence. Nor Brook before him.
What the substituted graph does reflect is the deep currents of scepticism flowing through the IPCC at the time -- and especially among the authors of Ch 7 and Ch 8 (yes, I do mean Wigley...the evidence is all there). It is hard not to believe that there were folk in the author pool trying to hose down the climate change (cooling or warming) alarm as so many scientists had done before them in the many assessment reports of the 1970s and 1980s. But in FAR someone (whoever it was) went too far by inserting that graph where it did not belong.
Many have thought that it might have been warmer globally some time in the Medieval period -- its a good hypothesis -- but no one found good evidence that this was the case. The problem was that warming somewhere at some time was compensated by cooling elsewhere. And too much data is missing -- especially in the South.
I s'pose I keen saying this, but have never properly explained...and so I will get a post together on the weekend to show what happened in FAR and why we should be skeptical of the hockey stick etc for many reasons...but not this one.
This meme that Jonathan Overpeck supposedly wrote "We have to get rid of the MWP" keeps popping up from time to time, but does anyone actually have that email? I'm sceptical that he actually wrote that, and I certainly don't believe he was part of some conspiracy to fiddle the data, as seems to be implied.
It's all very well criticising papers linking climate scepticism to conspiracy theories (and as you know, I have joined some of this criticism) but when a juicy-sounding phrase gets repeated without any actual evidence that it was actually said, just because it seems to support an idea that some people were up to no good, it's no surprise that other people will dismiss you as conspiracy theorists.
Bish said: "The Medieval Warm Period ... is now apparently accepted as probably being warmer than the current warming"
If the IPCC is no longer saying that the current warm period (50 years) is warmer than the MWP, that doesn't imply that the converse must be true: the MWP is warmer than the CWP. There is huge gap (statistically speaking) between demonstrating the former (CWP>MWP) and the latter (MWP>CWP). In the gap, all we can say is that we don't know which is warmer (although it appears that the IPCC has avoided stating this).
Now that the ludicrous terminology "more likely than not" has been abandoned by the IPCC, there is no weaker statement that the IPCC can use than "likely". Since the 30 years before AR5 have been warmer on average than the 50 years before AR3 and AR4, shortening would make it easier to demonstrate that CWP>MWP. However, this assessment probably hasn't been made by statistical analysis of all the reconstructions that have survived close scrutiny, it has been made by expert opinion.
Furthermore, the word "likely" is equivalent to the experts concluding that one die tossed will turn up a number less than 5 or 6, ie less than 66% to 83% of the time. In science, the traditional standard is p<0.05, which is roughly equivalent to saying that two dice are going to yield a total of 3-11 spots.
Richard Betts: I'm sure you will have read Steve McIntyre's typically thorough review of the evidence in October, particularly the section Deming in Context. I don't think anyone's claiming today that Deming still has the email. But this is damning testimony:
Needless to say it all depends who you trust.
Richard Verney
There's a good candidate for the natural variation you describe. It is the long term cooling trend due to reduced insolation as orbital changes move us away from the Holocene climatic optimum. This would lead us to expect warmer temperatures during the MWP and an ongoing cooling thereafter.
Of course, we are then left with the problem of explaining the sudden reversal of that trend since the latter 1800s and the ongoing warming observed since then. :-)
omnologos:
Very well said. But the hockey stick graph, with MWP duly flattened, nevertheless came to represent the idea of unprecedented warming due to man. This helped convert someone as smart as Matt Ridley to no longer be a 'sceptic about the science of climate change'.
So there was always a difference between the real science and the propaganda. And this is the context for the debate about Deming's testimony against Overpeck, which seems so neatly to lead on the Michael Mann's pioneering work and rapid elevation within the priesthood of the IPCC. As conspiracy theories go it's at least highly consistent.
I think that's only partly true. As I understand it, Deming first put this in print a decade after the alleged email, and never put the words in quotation marks himself.
I think it likely that he received an email, of which this a paraphrase. But I would not trust anyone to recall an exact wording over that period of time without further evidence. Perhaps Deming made a record at the time or just has very exceptional memory. But I know from introspection that when I try to paraphrase arguments with which I disagree, when I go back to check against the original text I have usually unconsciously made my job of criticism easier (that is why I try to go back an check!).
Deming never claimed this was more than a paraphrase, at a decade's distance. I good reference might be to look in the historical literature at how historians treat similar claims, which must often been made. I would say the evidence here is quite strong that Deming had a corespondent who was interested in the MWP, and probably in ways in which estimates of MWP temperatures could be reduced. Without more context or quotation I find it hard to say more.
I think those above who attribute a direct quotation to Overpeck (something that Deming did not do) are wrong. I don't think this position implies that Deming (or Overpeck) are dishonest.
I'm the author of the blog post on the IPCC report. My post was just featured a handful of findings... it's not at all comprehensive...just a teaser.
As I note in my post, I'll dig deeper into the report once it's finalized. As for the MWP, the IPCC says a couple things:
"Analyses of paleoclimate archives indicate that in 4 the Northern Hemisphere, the period 1983–2012 was very likely the warmest 30-year period of the last 800 years (high confidence) and likely the warmest 30-year period of the last 1400 years (medium confidence)."
"Continental-scale surface temperature reconstructions show, with high confidence, multi-decadal intervals during the Medieval Climate Anomaly (950−1250) that were in some regions as warm as in the late 20th century. These intervals did not occur as coherently across seasons and regions as the warming in the late 20th century (high confidence)."
The IPCC stresses these statements are draft and subject to change via the government review.
Thanks for reading...
Jason: Thanks - and give our love to Jeff Bezos while you're at it. :)
JK:
No I think it's wholly true. And you have helpfully given some good reasons why we might be wise not to trust Deming completely on the content of the email. I was actually very mindful of this when I wrote what I did. That's why I quoted Deming beginning with
Because it's the whole of the testimony that is damning. I agree about what so often happens when we go back to material we haven't viewed for a while but about which we have formed a particular view - taken sides, if you will.
However, my reading is that it took courage and a deep concern for the truth for Deming to testify as he did. This militates in favour of trusting him. Though it would I agree be unwise to take the Overpeck as verbatim it seems unlikely that Deming didn't correctly 'get his drift'.
Aug 21, 2013 at 11:44 AM | omnologos
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It seems that you are agreeing with me.
As I noted, the existence of the MWP driven by natural variation "...does not, of course, necessarily mean that CO2 does not warm, or indeed is not entirely responsible for the late 20th century warming, but it does mean that the claim that the only explanation for the late 20th century warming is CO2 must be wrong."
In my opinion, the existence of the MWP driven by natural variation makes the 95% confidence in manmade warming being behind the late 20th century warming untenable. As you say "The idea that the new 95% figure is suddenly scientifically sound, is beyond risible."
Further to the point raised by Richard Drake (Aug 21, 2013 at 3:35 PM), I am sure that most readers are aware that the importance of the hockey stick to "the Team" was not the blade, but the handle. It was important that that was nearly as flat as possible since pre-industrial CO2 levels were said to be stable for thousands of years and if CO2 controlled temperature there ought to be little variation in temperature if CO2 was the main driver of temperature as claimed, ie., the claim that it was dominant over natural variation and thereby had dominion over all.
Richard B, as I expect you are aware, the primary source for "we have to get rid of the MWP" is a statement to a US senate Committee from David Deming, attributed to "a major researcher in the area of climate change".
Regarding the leak, Judith Curry describes it as "this orchestrated leak by the IPCC", and Ryan Maue says "now its [IPCC] PR firm is coordinating them". I wonder what evidence these people have that the leak was deliberate? Is it just the fact that all the leaks went to sympathetic journalists and climate activists?
Well it's in quotes in the official transcript Paul links to above.
Foxgoose: Fair point. And if perchance it turned out that one or two of the words were misremembered but the thrust was correct then I'm sure Deming wouldn't be accused by senators of misleading them. I don't think it's the punctuation marks that are the crucial thing here. This is something one would remember.
Jonathan Overpeck has stated quite clearly both in a climategate email and in a public statement that it was probably not him.
The following Climategate email chain was initiated in March 2008 as a result of a direct question to Jonathan Overpeck from David Holland.
1206628118.txt
"I have no memory of emailing w/ him, nor any
record of doing so (I need to do an exhaustive
search I guess), nor any memory of him period. I
assume it is possible that I emailed w/ him long
ago, and that he's taking the quote out of
context, since know I would never have said what
he's saying I would have, at least in the context
he is implying."
David Deming is on record in correspondence with Geoff Brown in January 2009 as refusing to put the name of the email author in writing. I am aware David Deming has restated this position to at least one other person.
See
http://agmates.ning.com/group/climatscepticsparty/forum/topics/smokin-gun?xg_source=activity
and
http://joannenova.com.au/2009/06/the-wong-fielding-meeting-on-global-warming/
"I don't have a copy of the email in question.
When I received it, around 1995, global warming was not the contentious issue it is today. So, although I thought the message was astounding, I did not bother to archive a copy. Therefore, I am only 99 percent certain of the identity of the person in question.
I have told people orally what my recollection is. But I have never given the name in writing, because I cannot be absolutely certain.
In any event, the real significance is not the identity of an individual, but that science is being twisted and perverted to serve an ideology."
The uncertainty suggests that David Deming may have been in contact with more than one person ("one of them") and has a lingering doubt about which one of them actually sent the email.
Jonathan Overpeck was originally named as the author of the email in 2005 by speculation at several forums by a poster called Andre. The basis of the speculation was quite stunningly poor (googling the authors of the 2001 IPCC TAR looking for certain keywords!). Despite this Steve McIntyre took a liking to the speculation and kept pushing it on 4 separate occasions until it was turned into a "fact" in early 2008. It is clear this has happened because at least one prominent skeptic who subsequently named Jonathan Overpeck then linked back to a post by Steve McIntyre at climateaudit as the source of the "fact". To be fair to Steve McIntyre he has always admitted it was speculation. I dont believe that Andre got lucky with his speculation and in my opinion the evidence now strongly suggests he missed the proper target by a distance.
In June 2009 David Deming published a further article. See
http://www.lewrockwell.com/orig9/deming3.html
"Earlier this month, the Obama administration issued a report that concluded global warming would have a number of deleterious effects on the US. In 1995, one of the lead authors of this report told me that we had to alter the historical temperature record by "getting rid" of the Medieval Warm Period".
David Deming was probably well aware that people were already naming Jonathan Overpeck when he pointed to this report. Is his decription of "lead author" deliberate and significant or did he make a mistake and really mean one of the 30 members of the Author Team which includes Jonathan Overpeck and Ben Santer? The production of this glossy report was sufficiently poor that perhaps it did have 30 "lead" authors all contributing to its photoshop photo of a flooded house and other delights.
However there are 3 people who are listed in the author team who have the title "co chair and editor" and who may be a better match to the description lead author. They are Thomas Karl, Jerry Melillo and Thomas Peterson. See
http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts/production-team
It can be confirmed that David Demings work was of interest to IPCC researchers in 1995 because it is referenced in Chapter 3 of the 1995 SAR wg_I_full_report.
http://www.ipcc.ch/ipccreports/sar/wg_I/ipcc_sar_wg_I_full_report.pdf
By what must be pure coincidence Thomas Karl is an author of this chapter 3 and Thomas Peterson is listed as a contributer. Ben Santer is also a contributer to this chapter.
Jonathan Overpeck is not listed as an author or contributer to this chapter 3 but is listed as a contributer to chapter 9 where Jerry Melillo is an author. Jonathan Overpeck appears to have been a relatively minor IPCC researcher in 1995.
Foxgoose:
Yes, that's interesting. I was misled by the extract from the SEPP reprint from Journal of Scientific Exploration at Climate Audit, where Steve is usually meticulous but for some reason the quotation marks went missing in action.
The Journal of Scientific Exploration article has a mix of direct quotes and quotes from conversations which would seem very likely remembered, so it isn't clear whether the MWP quote is intended to be direct or a paraphrase. From the fact that Deming says he no longer has the email, I presume it's a paraphrase.
From Steve M ... a note from Overpeck....
While the identity of Deming’s correspondent remains uncertain, a Climategate letter from January 13. 2005, written as an instruction from Overpeck as Coordinating Lead Author to IPCC Lead Authors Briffa and Osborn (cc Jansen, Masson-Delmotte), states that Overpeck wants to “deal a mortal blow” to the MWP (and Holocene Optimum) “myths” (480. 1105670738.txt).
Hi Keith and Tim -
…
In reading Valerie [Masson-Delmotte]‘s Holocene section, I get the sense that I’m not the only one who would like to deal a mortal blow to the misuse of supposed warm period terms and myths in the literature. The sceptics and uninformed love to cite these periods as natural analogs for current warming too – pure rubbish.
So, pls DO try hard to follow up on my advice provided in previous email. No need to go into details on any but the MWP, but good to mention the others in the same dismissive effort. “Holocene Thermal Maximum” is another one that should only be used with care, and with
the explicit knowledge that it was a time-transgressive event totally unlike the recent global warming.
Thanks for doing this on – if you have a cool figure idea, include it.
Best, peck
[Update - Apr 10, 2010. In an email on Jul 18, 2005 (551. 1121721126.txt), Briffa wrote Overpeck, Jansen and Crowley, expressing concern about a figure that Crowley had proposed observing:
there are intonations in some of Peck's previous messages that he wishes to "nail" the MWP - i.e. this could be interpreted as trying to say there was no such thing..
Aug 21, 2013 at 3:30 PM | Entropic Man
///////////////////////
Entropic Man
Thanks your response.
I do not know enough about natural variation to ascribe it all to changes in insolation. Personally, I do not consider that natural variation is restricted simply to orbital changes, but I do consider that changes in insolation to be material, and I do consider that we do not know enough about clouds and the extent of cloudiness during the 20th century still less for earlier periods (eg. periods going back 1000 or so years) to be able to assess whether this is the dominant cause or a significant cause of variation in temperatures over the course of the last century and during earlier periods extending back some 1000 years.
fSo that I can better understand your point. and in particular your cliam that the waming post the LIA is problematic, please will you:
1. Set out the orbital path of the planet between say 800 to 2000AD in relation to the sun.
2. Detail on say a 50 year basis, the insolation being experienced by planet Earth between the above dates.
clivere: Thank you for such a thorough report. I was clearly wrong to think that the identification of Overpeck as author was a given. (Thanks Paul Matthews and Alan Reed for the same point.)
Alan Read,
I can well imagine that Deming received a similar email, albeit a decade earlier. But note the wording, even in an informal email: 'deal a mortal blow to the misuse of supposed warm period terms and myths in the literature.' It's hard to arguing with wanting to stop a 'misuse' or terminology or with wanting to get rid of 'myths'.
But of course that would take us back to the substance - is it really a 'misuse' or 'myth' to argue that there was a natural analog to current warming in the MWP? Overpeck believed so, while others disagree. I'm not sure that this email, or the one that Deming received take us much further than that.
To do so we would have to know on what basis Overpeck believes that the skeptic arguments are 'pure rubbish' Does he have good reasons - or any reasons? I don't see that discussed here, so we can't say if his reasons are good or bad, or just motivated by politics or grant funding.
(Obviously the reasons held by the different parties to the debate have been extensively debated elsewhere - just not here.)
This email and Deming's testimony seem to me to be telling us that Overpeck was convinced that use of the MWP as an analog for modern warming is 'pure rubbish'. But is this any different to what he would have said in public if he had just been asked? Do we have here a divergence between public and private? e.g. in public Overpeck is respectful of the uncertainty, saying that the evidence is not in, while in private working for the IPCC he reveals his true belief and is prepared to distort the record in that direction.
If such public statements from the period 1995 or 2005 can be found, i.e. Overpeck saying in public that the judgement is not yet in on the MWP, then I think that this email and Deming's testimony might add something important.
Otherwise, although Overpeck may or may not be wrong, I don't think the email or testimony add much to the debate.
@Richard and others.
Please DNFTT.
Hi Don. Which Richard? There are three of us so far. And which troll?
OK JK let's leave it there.
@Richard Drake- I was referring to EM
Richard Verney
This will get you started. Note particularly the two graphs at the end.
Richard Verney
This is probably one of the best recent discussions, with graphs for the orbital and insolation parameters you requested.
http://www.google.co.uk/search?q=An+Exceptionally+Long+Interglacial+Ahead%3FA.+Berger,+M.+F.+Loutre&rls=com.microsoft:en-gb:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=&gws_rd=cr&ei=QlQVUsO_BOqm0AWF1oCwBQ