date: Tue, 15 Feb 2005 18:09:25 +0100
from: Valerie Masson-Delmotte <Valerie.Masson@cea.fr>
subject: B4 read
to: Keith Briffa <k.briffa@uea.ac.uk>, Tim Osborn <t.osborn@uea.ac.uk>

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Dear Keith and Tim,

I have been through B4 text which I think needs to be partly rewritten

- to make the state of the art more explicit (where will this be 
together with key references?) and avoid repetitions

- to make more explicit the links between the different subtasks.

I would suggest in page 1 (introduction) to include :
- place the well described climate variability of the last millenium 
into a broader perspective of decadal to millenial scale variability.

- temporal resolution, calibration, quantitative reconstructions have to 
be also highlighted. I would suggest to state that : in the last decade, 
intensive efforts have been conducted in different communities to 
provide decadal to millenial scale reconstructions of past climate 
change. This project wants to build bridges over these various 
communities dedicated to specific archives (marine, terrestrial, ice 
core work) in order to evaluate clearly the spectral part of climate 
variability that each proxy record captures.

- I think that the introduction and objectives have to pose scientific 
questions and must not only focus on methods (which looks a bit boring). 
So we should clearly say that in order to improve the current 
understanding of climate change, we need to understand how climate 
variability changes together with mean climate. Until now, efforts to 
disentangle these two factors have failed because of the different 
"sampling" of climate variaibility in different proxies. The Holocene 
perspective offers the possibility by combining different types of proxy 
records to evaluate how the mean state and the variability (including 
the seasonal cycle, temperature and precipitation effects) vary in 
response to a variety of climate forcings (orbital forcing with both 
precession and obliquity components driving both changes in seasonal and 
latitudinal gradients of incoming solar radiation; irradiance with a key 
necessity to better quantify it; and intervals of more or less frequent 
volcanic activity).

- it should be made clear that the focus will be on describing past 
temperature AND precipitation variability all way through in a way to 
assess not only the realism of the simulated temperature but also the 
mechanisms involved in climate feedbacks (water cycle).

- forcings. Do we have to say anything about land use changes? (you have 
the Ruddimann hypothesis for the Holocene; and also changes known to be 
very significant during the last centuries). It is not very explicit in 
the WP1 but I am sure that modellers such as Fortunat Joos or Victor 
Brovkin will play with this factor.

- all way through : we have to be very consistent about places of 
interest. You can see from B4 draft places of interest ranging from 
Europe and Africa, surrounding oceans, poles, Antarctica, Greenland, 
North American droughts and various ocean basins.

I think that it would be much better to pose the questions in terms of 
forcings and responses together with modes of variability rather than in 
geographical structure. Then you have the orbital forcing and you need 
to have latitudinal gradients to look at the climate response because 
the forcing includes lat and seasonal gradients.

It should be made clear that it not understood what may organise (and 
cause?) millenial scale variability throughout the Holocene and that the 
collection of data should enable to evaluate the local vs global 
character of this variability (is it common in proxies of ocean 
circulation and terrestrial records, and common between the different 
latitudes).

The north American droughts arrive here a bit strangely, why not first 
ask about variability of temperature (seasonal, annual) and 
precipitation (incl droughts), and put the reconstructions in Europe and 
Africa in a broader context of hydrological cycle variability incl north 
America?

For task 1.1, I would suggest to classify the likey results (I would 
prefer to call it deliverables) by temporal scale covered starting by 
documentary evidence, European scale, and then broader scale including 
the poles. It should be made clear that an improved knowledge about 
polar variability is also an outcome of 1.5 with a better reconstruction 
of forcings together with common time scales for the 2 poles.

- reference to links outside IMPRINT: we should ask clearly all partners 
to list their national and EC projects (including ESF Euroclimate 
projects now accepted)

- in several tasks it is mentioned "selected regions". It should be made 
clear what are the selected regions and what the criteria are.

- task 1.3 is a bit too explicit about Jan and Jul temperature 
(winter/summer could be enough, because of previous calibration works on 
biomes with coldest month,
warmest months or other bioclimatic variables)

- I like task 1.4 the way it is formulated now, maybe too much detail in 
the likely results

- forcings : I do not understand what is meant by "to make predictions 
about the future". Predictions of future forcings? Predictions of 
possible variability due to natural causes in the future that may offset 
greenhouse increase? Sentence about orbital parameters to be rewritten 
to : The orbital forcing is the only forcing which can be precisely 
calculated both for the past and the future...
What is " a range of physically plausible" models? (I would say : a 
hierarchy of climate models see WP4).

Do you think that we should include a schematic diagram about sites, or 
about the combination of different archives with different time 
resultions in the different tasks?

Valerie.



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