cc: tkarl@ncdc.noaa.gov date: Wed, 22 Sep 1999 17:10:52 -0400 from: "Michael E. Mann" subject: RE: IPCC revisions to: "Folland, Chris" , Keith Briffa , "Folland, Chris" , 'Phil Jones' Thanks Chris, (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?) thanks all, mike. At 09:56 PM 9/22/99 +0100, Folland, Chris wrote: >Dear All > >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. > >Best wishes > >Chris >> -----Original Message----- >> From: Michael E. Mann [SMTP:mann@multiproxy.evsc.virginia.edu] >> Sent: 22 September 1999 17:35 >> To: Keith Briffa; Folland, Chris; 'Phil Jones' >> Cc: tkarl@ncdc.noaa.gov; mann@virginia.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 >> no >> 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 >> discussion >> will be the fact that certain key features of past climate estimates are >> robust among a number of quasi-independent and truly independent >> estimates, >> each >> 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 >> work. >> >> 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 >> myself). >> The key thing is making sure the series are vertically aligned in a >> reasonable >> 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 >> mean >> 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 >> seasonality >> *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 >> series. >> >> 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. >> Perhaps >> 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 >> Jones >> 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 >> estimates >> 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 >> very >> 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: >> >> http://www.ngdc.noaa.gov/paleo/ei/ei_cover.html >> >> 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 >> far >> 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: >> http://www.ngdc.noaa.gov/paleo/ei/ei_datarev.html >> and specifically, the plot and discussion here: >> http://www.ngdc.noaa.gov/paleo/ei/ei_nodendro.html >> 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, >> frankly, >> 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 >> I'm >> 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, >> >> mike >> >> 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 >> true >> >is that these particular tree-ring data best represent SUMMER >> temperatures >> >mostly at the northern boreal forest regions. By virtue of this , they >> also >> >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 >> with >> >the former at these timescales. The multi proxy series (Mann et al . >> Jones >> >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 >> do >> >a number of other lower resolution data ( Bradley et al, Peck et al ., >> and >> >new Crowley series - see our recent Science piece) whether this >> represents >> >'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 >> longer >> >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 >> any >> >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 >> do >> >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 >> that >> >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 >> indeed. >> >Glacier mass balance is driven by the difference mainly in winter >> >accumulation and summer ablation , filtered in a complex non-linear way >> to >> >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, >> I >> >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 >> fertilisation >> >through high CO2 or nitrate input) . I know there is pressure to present >> a >> >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 >> quite >> >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 >> warming >> >is so clear in the summer responsive data. I believe that the recent >> warmth >> >was probably matched about 1000 years ago. I do not believe that global >> >mean annual temperatures have simply cooled progressively over thousands >> of >> >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 >> future >> >background variability of our climate. I think the Venice meeting will >> be >> >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 >> Policy >> >>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 >> glaciers >> >>and, less clearly, suspect about solar variations). The tree ring >> results >> >>may still suffer from lack of multicentury time scale variance. This is >> >>probably the most important issue to resolve in Chapter 2 at present. >> >> >> >>Chris >> >> >> >>> -----Original Message----- >> >>> From: Phil Jones [SMTP:p.jones@uea.ac.uk] >> >>> Sent: 22 September 1999 12:58 >> >>> To: Michael E. Mann; k.briffa@uea.ac.uk >> >>> Cc: ckfolland@meto.gov.uk; tkarl@ncdc.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 >> evidence >> >>> 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 >> exclude >> >>> the >> >>> tree-ring only reconstructions. Keith's reconstruction is of a >> different >> >>> character to other tree-ring work as it is as 'hemispheric in scale' >> as >> >>> possible so is unlike any other tree-ring related work that is >> reported >> >>> upon. >> >>> If we go as is suggested then there would be two diagrams - one >> simpler >> >>> 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 >> them >> >>> into context. >> >>> The most important bit of the proxy section is the general >> discussion >> >>> of >> >>> 'Was there an MWE and a LIA' drawing all the strands together. Keith >> and >> >>> I >> >>> would be happy to look through any revisions of the section if there >> is >> >>> 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 >> a >> >>> 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 >> types >> >>> and >> >>> the modellers/detectors there). I suggested to Peck that this was >> early >> >>> in the week as I have to leave on the Thursday to go to the last day >> of >> >>> a Working Group meeting of the Climate Change Detection group in >> Geneva >> >>> ( a joint WMO Commission for Climatology/CLIVAR). I hope to report on >> the >> >>> main findings of the Venice meeting. >> >>> >> >>> Another issue I would like to raise is availability of all the >> series >> >>> 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 >> be >> >>> 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.jones@uea.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: mann@virginia.edu Phone: (804) 924-7770 FAX: (804) 982-2137 >> http://www.evsc.virginia.edu/faculty/people/mann.html > > _______________________________________________________________________ Professor Michael E. Mann Department of Environmental Sciences, Clark Hall University of Virginia Charlottesville, VA 22903 _______________________________________________________________________ e-mail: mann@virginia.edu Phone: (804) 924-7770 FAX: (804) 982-2137 http://www.evsc.virginia.edu/faculty/people/mann.html