date: Wed, 22 Sep 1999 17:10:52 -0400
from: "Michael E. Mann" <mannatXYZxyztiproxy.evsc.virginia.edu>
subject: RE: IPCC revisions
to: "Folland, Chris" <ckfollandatXYZxyzo.gov.uk>, Keith Briffa <k.briffaatXYZxyz.ac.uk>, "Folland, Chris" <ckfollandatXYZxyzo.gov.uk>, 'Phil Jones' <p.jonesatXYZxyz.ac.uk>
(and sorry everyone else for the flood of emails). That sounds like a good
arrangement to me.
I look forward to working w/ Ian on that, and coming to some concensus
w/ Phil and Keith (hopefully we're pretty close on that score w/ the latest
draft I copied o you guys?)
At 09:56 PM 9/22/99 +0100, Folland, Chris wrote:
>IPCC is a concensus report or if there is a majority viewpoint and a
>legitimate minority point, both can be aired. So Mikes points need to be
>addressed one way or the other.
>I was only statiing, purely for the discussion, my own feelings based on the
>evidence I have read over many years about how global temperature might have
>varied over the last 500 years in particular. I am not contributing to this
>section, only acting as an editor. So I expressed my own thoughts, not
>Mikes, about what might ultimately turn out to be the case. In the meantime,
>the disagreement between the series, if all are shown, needs more comment.
>Mike, Ian will be getting round to your plots later tomorrow. I guess the
>existing diagram should be tarted up (please liaise directly with Ian on
>what you want and react to him) but there will be time for one change of
>mind in the coming working week should that is agreed between you. I will
>take no further part in the debate for now but watch it with interest.
>> -----Original Message-----
>> From: Michael E. Mann [SMTP:email@example.com]
>> Sent: 22 September 1999 17:35
>> To: Keith Briffa; Folland, Chris; 'Phil Jones'
>> Cc: firstname.lastname@example.org; mannatXYZxyzginia.edu
>> Subject: RE: IPCC revisions
>> Thanks for your response Keith,
>> For all:
>> Walked into this hornet's nest this morning! Keith and Phil have both
>> raised some very good points. And I should point out that Chris, through
>> fault of his own, but probably through ME not conveying my thoughts very
>> clearly to the
>> others, definitely overstates any singular confidence I have in my own
>> (Mann et al) series. I believe strongly that the strength in our
>> will be the fact that certain key features of past climate estimates are
>> robust among a number of quasi-independent and truly independent
>> of which is not without its own limitations and potential biases. And I
>> certainly don't want to abuse my lead authorship by advocating my own
>> I am perfectly amenable to keeping Keith's series in the plot, and can ask
>> Ian Macadam (Chris?) to add it to the plot he has been preparing (nobody
>> liked my own color/plotting conventions so I've given up doing this
>> The key thing is making sure the series are vertically aligned in a
>> way. I had been using the entire 20th century, but in the case of Keith's,
>> we need to align the first half of the 20th century w/ the corresponding
>> values of the other series, due to the late 20th century decline.
>> So if Chris and Tom (?) are ok with this, I would be happy to add Keith's
>> series. That having been said, it does raise a conundrum: We demonstrate
>> (through comparining an exatropical averaging of our nothern hemisphere
>> patterns with Phil's more extratropical series) that the major
>> discrepancies between Phil's and our series can be explained in terms of
>> spatial sampling/latitudinal emphasis (seasonality seems to be secondary
>> here, but probably explains much of the residual differences). But that
>> explanation certainly can't rectify why Keith's series, which has similar
>> *and* latitudinal emphasis to Phil's series, differs in large part in
>> exactly the opposite direction that Phil's does from ours. This is the
>> problem we
>> all picked up on (everyone in the room at IPCC was in agreement that this
>> was a problem and a potential distraction/detraction from the reasonably
>> concensus viewpoint we'd like to show w/ the Jones et al and Mann et al
>> So, if we show Keith's series in this plot, we have to comment that
>> "something else" is responsible for the discrepancies in this case.
>> Keith can
>> help us out a bit by explaining the processing that went into the series
>> and the potential factors that might lead to it being "warmer" than the
>> et al and Mann et al series?? We would need to put in a few words in this
>> regard. Otherwise, the skeptics have an field day casting
>> doubt on our ability to understand the factors that influence these
>> and, thus, can undermine faith in the paleoestimates. I don't think that
>> doubt is scientifically justified, and I'd hate to be the one to have
>> to give it fodder!
>> The recent Crowley and Lowery multiproxy estimate is an important
>> additional piece of information which I have indeed incorporated into the
>> revised draft.
>> Tom actually estimates the same mean warming since the 17th century in his
>> reconstruction, that we estimate in ours, so it is an added piece of
>> information that Phil and I are probably in the ballpark (Tom has used
>> a somewhat independent set of high and low-resolution proxy data and a
>> basic compositing methodology, similar to Bradley and Jones, so there is
>> some independent new information in this estimate.
>> One other key result with respect to our own work is from a paper in the
>> press in "Earth Interactions". An unofficial version is available here:
>> THe key point we emphasize in this paper is that the low-frequency
>> variability in our hemispheric temperature reconstruction is basically the
>> same if we don't use any dendroclimatic indicators at all (though we
>> certainly resolve less variance, can't get a skillful reconstruction as
>> back, and there are notable discrepancies at the decadal and interannual
>> timescales). A believe I need to add a sentence to the current discussion
>> on this point,
>> since there is an unsubstantiated knee-jerk belief that our low-frequency
>> variability is suppressed by the use of tree ring data.
>> We have shown that this is not the case: (see here:
>> and specifically, the plot and discussion here:
>> Ironically, you'll note that there is more low-frequency variability when
>> the tree ring data *are* used, then when only other proxy and
>> historical/instrumental data are used!
>> SO I think we're in the position to say/resolve somewhat more than,
>> than Keith does, about the temperature history of the past millennium.
>> And the issues I've spelled out all have to be dealt with in the chapter.
>> One last point: We will (like it or not) have SUBSTANTIAL
>> opportunity/requirement to revise much of this discussion after review, so
>> we don't have to resolve everything now. Just the big picture and the
>> important details...
>> I'm sure we can can up with an arrangement that is amenable to all, and
>> looking forward to hearing back from Keith, Phil, and Chris in particular
>> about the above, so we can quickly move towards finalizing a first draft.
>> Looking forward to hearing back w/ comments,
>> At 04:19 PM 9/22/99 +0100, Keith Briffa wrote:
>> >Hi everyone
>> > Let me say that I don't mind what you put in the policy makers
>> >summary if there is a general concensus. However some general discussion
>> >would be valuable . First , like Phil , I think that the supposed
>> >separation of the tree-ring reconstruction from the others on the grounds
>> >that it is not a true "multi-proxy" series is hard to justify. What is
>> >is that these particular tree-ring data best represent SUMMER
>> >mostly at the northern boreal forest regions. By virtue of this , they
>> >definately share significant variance with Northern Hemisphere land and
>> >land and marine ANNUAL temperatures - but at decadal and multidecadal
>> >timescales - simply by virtue of the fact that these series correlated
>> >the former at these timescales. The multi proxy series (Mann et al .
>> >et al) supposedly represent annual and summer seasons respectively, and
>> >both contain large proportions of tree-ring input. The latest tree-ring
>> >density curve ( i.e. our data that have been processed to retain low
>> >frequency information) shows more similarity to the other two series- as
>> >a number of other lower resolution data ( Bradley et al, Peck et al .,
>> >new Crowley series - see our recent Science piece) whether this
>> >'TRUTH' however is a difficult problem. I know Mike thinks his series is
>> >the 'best' and he might be right - but he may also be too dismissive of
>> >other data and possibly over confident in his (or should I say his use of
>> >other's). After all, the early ( pre-instrumental) data are much less
>> >reliable as indicators of global temperature than is apparent in modern
>> >calibrations that include them and when we don't know the precise role of
>> >particular proxies in the earlier portions of reconstruction it remains
>> >problematic to assign genuine confidence limits at multidecadal and
>> >timescales. I still contend that multiple regression against the recent
>> >very trendy global mean series is potentially dangerous. You could
>> >calibrate the proxies to any number of seasons , regardless of their true
>> >optimum response . Not for a moment am I saying that the tree-ring , or
>> >other proxy data, are better than Mike's series - indeed I am saying that
>> >the various reconstructions are not independent but that they likely
>> >contribute more information about reality together than they do alone. I
>> >believe , that it should not be taken as read that Mike's series (or
>> >Jone's et al. for that matter) is THE CORRECT ONE. I prefer a Figure
>> >shows a multitude of reconstructions (e.g similar to that in my Science
>> >piece). Incidently, arguing that any particular series is probably better
>> >on the basis of what we now about glaciers or solar output is flaky
>> >Glacier mass balance is driven by the difference mainly in winter
>> >accumulation and summer ablation , filtered in a complex non-linear way
>> >give variously lagged tongue advance/retreat .Simple inference on the
>> >precidence of modern day snout positions does not translate easily into
>> >absolute (or relative) temperature levels now or in the past. Similarly,
>> >don't see that we are able to substantiate the veracity of different
>> >temperature reconstructions through reference to Solar forcing theories
>> >without making assumptions on the effectiveness of (seasonally specific )
>> >long-term insolation changes in different parts of the globe and the
>> >contribution of solar forcing to the observed 20th century warming .
>> > There is still a potential problem with non-linear responses in the
>> >very recent period of some biological proxies ( or perhaps a
>> >through high CO2 or nitrate input) . I know there is pressure to present
>> >nice tidy story as regards 'apparent unprecedented warming in a thousand
>> >years or more in the proxy data' but in reality the situation is not
>> >so simple. We don't have a lot of proxies that come right up to date and
>> >those that do (at least a significant number of tree proxies ) some
>> >unexpected changes in response that do not match the recent warming. I do
>> >not think it wise that this issue be ignored in the chapter.
>> > For the record, I do believe that the proxy data do show unusually
>> >warm conditions in recent decades. I am not sure that this unusual
>> >is so clear in the summer responsive data. I believe that the recent
>> >was probably matched about 1000 years ago. I do not believe that global
>> >mean annual temperatures have simply cooled progressively over thousands
>> >years as Mike appears to and I contend that that there is strong evidence
>> >for major changes in climate over the Holocene (not Milankovich) that
>> >require explanation and that could represent part of the current or
>> >background variability of our climate. I think the Venice meeting will
>> >a good place to air these isssues.
>> > Finally I appologise for this rather self-indulgent ramble, but I
>> >thought I may as well voice these points to you . I too would be happy to
>> >go through the recent draft of the chapter when it becomes available.
>> > cheers to all
>> > Keith
>> >At 01:07 PM 9/22/99 +0100, Folland, Chris wrote:
>> >>Dear All
>> >>A proxy diagram of temperature change is a clear favourite for the
>> >>Makers summary. But the current diagram with the tree ring only data
>> >>somewhat contradicts the multiproxy curve and dilutes the message rather
>> >>significantly. We want the truth. Mike thinks it lies nearer his result
>> >>(which seems in accord with what we know about worldwide mountain
>> >>and, less clearly, suspect about solar variations). The tree ring
>> >>may still suffer from lack of multicentury time scale variance. This is
>> >>probably the most important issue to resolve in Chapter 2 at present.
>> >>> -----Original Message-----
>> >>> From: Phil Jones [SMTP:email@example.com]
>> >>> Sent: 22 September 1999 12:58
>> >>> To: Michael E. Mann; k.briffaatXYZxyz.ac.uk
>> >>> Cc: firstname.lastname@example.org; tkarlatXYZxyzc.noaa.gov
>> >>> Subject: Re: IPCC revisions
>> >>> Mike,
>> >>> Been away in Japan the last week or so. Malcolm was there in a
>> >>> wheelchair
>> >>> because of his ruptured achilles. We both mentioned the lack of
>> >>> for global scale change related to the MWE and LIA, but all the later
>> >>> Japanese speakers kept saying the same old things.
>> >>> As for the TAR Chap 2 it seems somewhat arbitrary divison to
>> >>> the
>> >>> tree-ring only reconstructions. Keith's reconstruction is of a
>> >>> character to other tree-ring work as it is as 'hemispheric in scale'
>> >>> possible so is unlike any other tree-ring related work that is
>> >>> upon.
>> >>> If we go as is suggested then there would be two diagrams - one
>> >>> one with just Mann et al and Jones et al and in another section
>> Briffa et
>> >>> al. This might make it somewhat awkward for the reader trying to put
>> >>> into context.
>> >>> The most important bit of the proxy section is the general
>> >>> of
>> >>> 'Was there an MWE and a LIA' drawing all the strands together. Keith
>> >>> I
>> >>> would be happy to look through any revisions of the section if there
>> >>> time.
>> >>> One other thing, did you bring up the possibility of having a
>> >>> proxy-only
>> >>> chapter ( albeit short) for the next assessment ?
>> >>> On Venice I suggested to Peck that you and Keith give talks on the
>> >>> reconstructions - frank and honest etc emphasising issues and I lead
>> >>> discussion with you both and the rest of those there where the issues
>> >>> can be addressed ( ie I would like to get the views of other proxy
>> >>> and
>> >>> the modellers/detectors there). I suggested to Peck that this was
>> >>> in the week as I have to leave on the Thursday to go to the last day
>> >>> a Working Group meeting of the Climate Change Detection group in
>> >>> ( a joint WMO Commission for Climatology/CLIVAR). I hope to report on
>> >>> main findings of the Venice meeting.
>> >>> Another issue I would like to raise is availability of all the
>> >>> you use in your reconstructions. That old chestnut again !
>> >>> How is life in Charlottesville ? Do you ever bump into Michaels
>> or is
>> >>> always off giving skeptical talks ?
>> >>> Tim Osborn is making great progress with his NERC grant and will
>> >>> looking
>> >>> into dates soon for coming to see you.
>> >>> Cheers
>> >>> Phil
>> >>> Prof. Phil Jones
>> >>> Climatic Research Unit Telephone +44 (0) 1603 592090
>> >>> School of Environmental Sciences Fax +44 (0) 1603 507784
>> >>> University of East Anglia
>> >>> Norwich Email p.jonesatXYZxyz.ac.uk
>> >>> NR4 7TJ
>> >>> UK
>> >>> --
>> >Dr. Keith Briffa, Climatic Research Unit, University of East Anglia,
>> >Norwich, NR4 7TJ, United Kingdom
>> >Phone: +44-1603-592090 Fax: +44-1603-507784
>> Professor Michael E. Mann
>> Department of Environmental Sciences, Clark Hall
>> University of Virginia
>> Charlottesville, VA 22903
>> e-mail: mannatXYZxyzginia.edu Phone: (804) 924-7770 FAX: (804) 982-2137
Professor Michael E. Mann
Department of Environmental Sciences, Clark Hall
University of Virginia
Charlottesville, VA 22903
e-mail: mannatXYZxyzginia.edu Phone: (804) 924-7770 FAX: (804) 982-2137