Thursday, December 15, 2011


From: Jonathan Overpeck <>
Subject: Re: Glaciers Ch 6
Date: Mon, 10 Jan 2005 17:20:06 -0700
Cc: Keith Briffa <>, Eystein Jansen <>,, "Ricardo Villalba" <>

V - well said. Eystein and I will be working on your Holo section -
more tomorrow. thx, Peck

>- the various NH T reconstr use polar records : to my knowledge only
>use of melt index that itself does not calibrate properly in Mann's
>reconstruction. I sent you Keith winter d18O from Vinther 2003 which
>provides a reconstruction of NAO changes (I think this is the more
>detailed calibration study for Greenland isotopes).
>On a decadal time scale calibration studies for Antarctica (Vostok
>and Law Dome, inland vs coastal sites) using available instr records
>(50 years) show correct decadal scale temperature signals. Even at
>places with subannual resolution like Law Dome I think that you
>cannot use the isotopes on a yearly basis but only decadal scale.
>- tropical glaciers : works conducted here on Andean ice cores
>together with modelling of isotopes in a GCM all showed a consistent
>decadal variability on the 20th century, most of which interpreted
>to be related to precip change (see for instance Hoffmann et al,
>Science, "Taking the pulse of the tropical water cycle", Science,
>2003). For more ancient past periods it is thought that part of the
>signal is due to T (and vertical lapse rate change), part to
>precip.I would not like to cosign any text claiming for a T
>reconstruction based on Andean ice cores.
>Keith Briffa wrote:
>>I agree with suggestion - there is the problem of the isotopic
>>analyses from tropical (and to some extent polar) ice cores still .
>>I am not happy simply to show these in a Figure relating to the
>>large-scale temperature changes - because we are not sure of the
>>extent to which they can be interpreted as such . The various NH
>>reconstructions use some polar isotope records but looking at plots
>>of the tropical records throws up some strange behavior over the
>>last 2000 years . I am not happy to write about these as Valerie
>>and Olga are better qualified and because I would like to see more
>>formal calibration against even short temperature records . I have
>>therefore , not as yet explicitly said anything about these
>>tropical records. I will sendthe latest text and latest draft
>>FIgure 1 later today
>>At 10:03 09/01/2005, wrote:
>>>Dear Olga,
>>>My suggestion would be, and I believe this is echoed by Peck, is
>>>that the box
>>>we produce comes in the overall Holocene sub-chapter, thus to avoid
>>>repetition. The figure should mainly give syntheses of the glacier extent
>>>variations through the Holocene, if possible, or a fraction of it
>>>if data only
>>>exists e.g. for the last few millennia, for those regions where there is a
>>>reliable data set. Then with text explaining what we think drove these
>>>variations. I think it should be a box in Ch6, and could also include the
>>>recent trends I have just talked with Atle and he is able to contribute
>>>curves for Scandinavia and the Alps into a figure before the end of the week
>>>(in a couple of days). He feels putting something together for North America
>>>and perhaps New Zealand is feasible, but he cannot do this before the ZOD
>>>deadline. Perhaps you might be able? If we get something for the
>>>tropics from
>>>Lonnie and Ellen and what you have, I will be able to put this together in a
>>>figure for the box via assistance here. We can in such a figure leave space
>>>open for curves we anticipate including for the First Draft.
>>>It might be a good idea to in this figure also include the recent,
>>>instrumental evidence for the same regions, akin to what will be in Ch4, and
>>>of course, in the next iteration come back to possible joint Ch4
>>>and 6 figure.
>>>How does this sound?
>>Professor Keith Briffa,
>>Climatic Research Unit
>>University of East Anglia
>>Norwich, NR4 7TJ, U.K.
>>Phone: +44-1603-593909
>>Fax: +44-1603-507784
>Attachment converted: Macintosh HD:masson 5.vcf (TEXT/ttxt) (000C2383)

Jonathan T. Overpeck
Director, Institute for the Study of Planet Earth
Professor, Department of Geosciences
Professor, Department of Atmospheric Sciences

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