date: Tue, 15 Feb 2005 18:09:25 +0100
from: Valerie Masson-Delmotte <Valerie.MassonatXYZxyz.fr>
subject: B4 read
to: Keith Briffa <k.briffaatXYZxyz.ac.uk>, Tim Osborn <t.osbornatXYZxyz.ac.uk>
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
- 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
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
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?
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