cc: "Michael E. Mann" , "Raymond S. Bradley" , Keith Briffa , Tom Crowley , Caspar Ammann , Phil Jones , Michael Oppenheimer , Kevin Trenberth date: Thu, 05 Jun 2003 14:53:59 -0600 from: Kevin Trenberth subject: Re: EOS text to: Tom Wigley Tom I agree with Mike that it is not possible to directly confront their methods in this way. It can be confronted by stating clearly that cold periods that are not contemporaneous at different locations do not make for a cold hemispheric value: currently the article already makes this point to some extent but it can be made more directly relevant to SB. In fact it may be worthwhile pointing out that the LIA is defined by different authors to be in different periods precisely because they were looking at a different part of the world (like blind men exploring the elephant). And we can also say that it makes no sense to equate wet or dry period with cold or warm universally (ref SB). In fact what is found generally in mid lats is that warm in winter goes with wet (through moist and warm advection) and with dry in summer (drought and heat waves). So seasonality matters a lot. Maybe we can say womething like this: It is well established in current climate studies that warm conditions tend to accompany wet conditions in the extratropics in winter owing to the dominant role of the atmospheric circulation so that southerlies are warm and moist in the northern hemisphere while northerlies are cold and dry. But in summer, the weaker atmospheric circulation means that moist thermodynamics is more important so that dry conditions favor warm spells and heat waves, as heat from the sun no longer evaporates moisture and instead increase temperatures. In the Tropics, during El Nino events, droughts occur in one part of the world (e.g. Australia) while wet conditions and floods occur in other parts (e.g. Peru), and the wet spots tend to switch with the dry spots during La Nina. Accordingly, there is no unique link between wet or dry with warm or cold conditions (such as erroneously assumed by SB). Not sure if this is useful but I offer it anyway. Kevin Tom Wigley wrote: > Mike et al., > > I will send tracked editorial suggestions later. In the meantime, what > is lacking in my view is a clear statement at the start of the SB > method. At present, the context of your later comments is a bit > unclear to those who have not read the papers -- which will be the > case for most readers. I suggest adding the attached before your point > (1). What I say here overlaps with some things you say later, so minor > changes are needed (which I will send later) to avoid clear duplication. > > We are using this to educate people about the good paleo work, but a > key motivation is to demolish the bad stuff. I think, therefore, that > the criticism of SB must be more focussed and specific -- which is why > a statement of their work is essential. This suggested new material > also provides a balance, and makes what we now have appear less self > serving (which I know you are not trying to do, but there is still a > hint of this). > > Tom. -- **************** Kevin E. Trenberth e-mail: trenbert@ucar.edu Climate Analysis Section, NCAR www.cgd.ucar.edu/cas/ P. O. Box 3000, (303) 497 1318 Boulder, CO 80307 (303) 497 1333 (fax) Street address: 3080 Center Green Drive, Boulder, CO 80301