From: "Michael E. Mann" To: "Dr. Nanne Weber" Subject: Re: workshop report Date: Mon, 18 Jun 2001 11:50:15 -0400 Cc: "Michael E. Mann" , Julia Cole , rbradley@geo.umass.edu, jto@u.arizona.edu, storch@gkss.de, wanner@giub.unibe.ch, tom crowley , k.briffa@uea.ac.uk Hi Nanne, Thanks for your comments. I've asked Julie Cole, who is attempting a revised draft, to incorporate your suggestions. Hans or you should also provide a revised paragraph 7 that is more to your liking than what I wrote. I'm requesting that Julie wait until the end of this week (Friday, Jun 22) to give the others time to get their comments in also. Then, after Julie provides me w/ her revised draft, I'll try to make a few more small changes and sent that onto the group for suggested final changes. I hope this sounds acceptable to all concerned? thanks, mike At 03:22 PM 6/18/01 +0000, Dr. Nanne Weber wrote: >Hi Mike (and others), > >Below follow some comments on the draft report for EOS that you send >around. The >general outline is fine for me. Responding to Julie's comment on the >large-scale/regional >reconstruction issue: I guess that the three different approaches >mentioned are not >necessarily restricted to large-scale. Especially (1) can be for all >scales, (2) will work >better for large scales, but (3) could be very well applied to regional >scales >like African monssoon or NAO. However, I do think that this 'scales >issue' >should be addressed explicitly in the text (as indicated in my >comments). > >We can not cover all of the workshop in a small EOS report, but I do >think >that there should be more emphasis on the different model strategies >presented, >process-based proxy modeling and some more mention of historical >documentary data. > >I am willing to take my share in the rewriting task. Just let me know >what is most >convenient for you. > > >One practical point: the Netherlands funding agency is called National >Research Program (NRP) of the Netherlands (KNMI is my affiliation, but >it >did not pay the bill) > >Thanks, > >Nanne >=================================================== > > >First para, first sentence: name all boundary conditions relevant >for geological timescales (astronomical forcing, orography, GHG >concentrations) >or none. > >First para, fifth sentence: Three distinct approaches have .... in >reconstructing >the LARGE-SCALE AND REGIONAL climate history of past centuries and >millenia. > >First para, point (3): the assimilation of paleoclimatic proxy data >directly >into (leave out 'forced') climate model integrations (using statistical >models to upscale the proxy data to large-scale climatic patterns), in a >manner >conceptually etc,. > > > >Second para: can be written in a more condense manner. One ore two >sentences >discussing the large-scale versus regional climate issue should be >added. For example: >(i) add after the second sentence ('The first method...'): This holds >for >spatial scales ranging from local (in the case of site-by-site >calibration) to >large scale (in the case of pattern calibration, e.g. ENSO and NAO) and >up to hemispheric/global. >(ii) add just before 'It was our belief that a meeting': The second and >third >approaches are more suitable for reconstructing the actual large-scale >climatic >state, as the local climate is inherently noisy and only to a limited >amount determined by external forcing or related to large-scale patterns > >like e.g. the NAO. > >Second para, modify the description of the third approach as follows: >The third approach can be thought of......, but it is nudged >toward the actual observed large-scale climatic state at the time >resolution provided by the proxy data. This method is more resistant to >the potential biases......model-based approaches, but it is relatively >untested to the application of proxy data. > > > >Fourth para: leave out second sentence "A frequency-domain...' (too much > >technical detail, in a too condensed form to be understandable to a >general >reader of EOS). > > > >Fifth para: very much biased toward the modeling of large-scale, forced >signal. >My go at modelling paragraph(s): >Three types of modelling experiments were distinguished: free >simulations without >any external forcing, giving insight into the patterns and timescales of > >internally-generated variability, forced simulations and simulations >constrained >by the assimilation of proxy data. Examples were presented, where models >used ranged >from an energy balance model (EBM), an intermediate-complexity climate >model (EMIC) to >atmospheric and coupled General Circulation Models (GCM). Simulations >with an >EBM as well as a GCM appear to explain variations over >century-to-decadal timescales >in proxy-based reconstructions of the Northern Hemisphere temperature >over the past millenium, using estimated changes in radiative forcing >(solar >irradiance changes, volcanic activity, GHG and aerosol concentrations). >Discrepancies, >however, etc.... (a bit long as it is now). > >Process-based models of glaciers and sea level were used to generate >synthetic >records of these low-frequency proxies on the basis of EMIC and GCM >simulations, >using unforced runs as well as orbital and solar-forced runs. >Over longer timescales simulated glacier lengths and sea level >variations >can be used to validate the models response in climatic parameters >which are not well constrained by existing proxy data, like the >hydrological cycle. >In addition, model-data intercomparisons can be carried >out on the level of the proxy itself rather than on the level of >reconstructed >climatic variables. Such process-based models require an understanding >of local meteorological processes as well as the complicated (physical, >biological or >chemical) processes determining the proxy itself. A promising new model >of >tree-ring growth was presented. > >A new data-assimilation approach to paleoclimatic reconstruction DATUN >(..) >was discussed at length.... >This paragraph is not very clear as it is. I can have a go at it, >but maybe Hans should. > > > >Para seven: This could be much shorter. Several points are mentioned >here >for the first time--> move up te earlier paragraphs (as indicated above) > >....currently emphasized high-resolution proxies such as tree rings, >HISTORICAL >DOCUMENTARY DATA, corals and ice cores. In addition, low-frequency >climate >variability may be reconstructed from low-resolution proxies such as >borehole >records, glaciers, foraminifera in marsh cores indicative of sea level >as well >as lake and ocean sediments which are not necessarily laminated. >Process-based proxy models would enable to better exploit the >information >contained in proxy records and help to resolve the origin of apparent >discrepancies between the different data sources. It is also important >to >better constrain the histories of radiative forcings prior to AD 1600. >It was >strongly felt that there should be an emphasis on developing >projects.... _______________________________________________________________________ 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.shtml