cc: k.briffa@uea.ac.uk
date: Mon, 12 Mar 2001 08:55:39 +0000
from: Phil Jones <p.jones@uea.ac.uk>
subject: Re: broecker
to: "Raymond S. Bradley" <rbradley@geo.umass.edu>
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Ray,
I've been in Japan, but I'm happy to sign up to this. I saw Lonnie in
Japan and it
would be good to get a reference to his stuff as the retreat of glaciers
is really
convincing in the tropical Andes and on Kilimanjaro. There is a small
problem though
with their retreat. They have retreated a lot in the last 20 years yet
the MSU2LT data
would suggest that temperatures haven't increased at these levels. You
and Henry have
shown that high-elevation stations have warmed a lot and freezing levels
have risen.
Still the glaciers have clearly receded, but the temperature increases at
these
high-elevation stations isn't enough to explain the rapid retreat. Could
be that the stations
are at 3Km and the glaciers at 5-7Km ? Interesting enigma to solve with
the non-warming
of the free atmosphere from the satellites and radiosondes.
Important thing is that they all have medieval ice in nice layers so
it has to be warmer
today to explain part of the retreat.
Broecker has sent me another Perspectives piece, this time from PNAS
97 (2000),
1339-1342, where he claims the LIA was caused by changes in the thermohaline
circulation.
In all day if you want to call. I guess I'll see you in Finland in June.
Cheers
Phil
At 15:36 09/03/01 -0500, you wrote:
>Do you want to sign on to this? I don't want to fuss with it much
>more..will call you on Monday
>ray
>____________________________________________________________________________
>______________________
>
>Hemispheric mean temperatures reconstructed using a wide range of climate
>proxies indicate that temperatures were warmer in Medieval times than
>during the subsequent “Little Ice Age” (~1550-1850) (1-3). However, all
>studies of large scale climate variations reveal some regions which do not
>follow the global or hemispheric trend (e.g. 4) so selecting a few data
>points, as Broecker does, (5) adds little to resolving the question he
>poses (“Was the Medieval Warm Period Global?”). Furthermore, his claim
>that only borehole temperatures and snowlines can reconstruct temperatures
>to within 0.5ºC is not supported in the literature. Reconstructing global
>temperature requires a geographically extensive network of data, not just
>a few points. Could you begin to appreciate the beauty and complexity of
>a symphony by just listening to the percussion section of an
>orchestra? Studies that have listened to a wide range of “instruments”
>(1-3, 6-7) conclude that 20th century warming is unprecedented in both
>rate and magnitude, compared to the last 1000 years. This view may change
>as additional records become available, but that is the state of play
>right now.
>Medieval climate was clearly unusual in some areas (8-12) and further
>regional studies are needed. These may help to determine if Broecker's
>hypothesis (13) of a change in thermohaline circulation holds water.
>
>
>Raymond S. Bradley
>Department of Geosciences
>University of Massachusetts, Amherst, MA 01003
>
>Malcolm K. Hughes
>Laboratory of Tree-Ring Research
>University of Arizona, Tucson, AR 85721
>
>Michael E. Mann
>Department of Environmental Sciences
>University of Virginia
>Charlottesville, VA 22903
>
>References
>1. P. D. Jones et al., The Holocene 8, 455 (1998).
>2. M.E. Mann, R.S. Bradley, M.K. Hughes, Geophys. Res. Lett. 26, 759 (1999).
>3. T.J. Crowley, T.S. Lowery, Ambio 29, 51 (2000).
>4. P.D. Jones et al., Reviews of Geophysics, 37, 173 (1999).
>5. W.S. Broecker, Science, 291, 1497 (2001).
>6. M. K. Hughes, H. F. Diaz, Clim. Change 26, 109 (1996).
>7. K.R. Briffa et al., J. Geophys. Res., 106D, 2929 (2001).
>8. S. Stine, S., in Water, Environment and Society in Times of Climatic
>Change, A.S. Issar, N. Brown, Eds. (Kluwer, Dordrecht, 1998), pp. 43-67.
>9. M.K. Hughes, G. Funkhauser in The Impacts of Climate Variability on
>Forests, M. Beniston, J.L. Innes, Eds. (Berlin, Springer) pp.99-107.
>10. C. Pfister et al., The Holocene, 8, 535 (1998).
>11. V.C. LaMarche, Science, 183,1043 (1974).
>12. D. Dahl-Jenssen et al., Science, 282, 268 (1998).
>13. W.S. Broecker, S. Sutherland, T-H. Peng, Science 286, 1132 (1999).
>
>
>
>
>
>
>Raymond S. Bradley
>Professor and Head of Department
>Department of Geosciences
>University of Massachusetts
>Amherst, MA 01003-5820
>
>Tel: 413-545-2120
>Fax: 413-545-1200
>Climate System Research Center: 413-545-0659
>Climate System Research Center Web Page:
><http://www.geo.umass.edu/climate/climate.html>
>Paleoclimatology Book Web Site (1999):
>http://www.geo.umass.edu/climate/paleo/html
>
>
Prof. Phil Jones
Climatic Research Unit Telephone +44 (0) 1603 592090
School of Environmental Sciences Fax +44 (0) 1603 507784
University of East Anglia
Norwich Email p.jones@uea.ac.uk
NR4 7TJ
UK
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