cc: "Michael E. Mann" <mann@virginia.edu>, "Raymond S. Bradley" <rbradley@geo.umass.edu>, Keith Briffa <k.briffa@uea.ac.uk>, Tom Crowley <tcrowley@duke.edu>, Caspar Ammann <ammann@ucar.edu>, Phil Jones <p.jones@uea.ac.uk>, Michael Oppenheimer <omichael@princeton.edu>, Kevin Trenberth <trenbert@ucar.edu>
date: Thu, 05 Jun 2003 14:53:59 -0600
from: Kevin Trenberth <trenbert@cgd.ucar.edu>
subject: Re: EOS text
to: Tom Wigley <wigley@ucar.edu>

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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



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