cc: jcole@geo.Arizona.EDU, sandy.tudhope@ed.ac.uk, k.briffa@uea.ac.uk, mhughes@ltrr.arizona.edu
date: Fri, 11 May 2001 09:00:03 +0200
from: Keith Alverson <keith.alverson@pages.unibe.ch>
subject: Re: comments?
to: "Raymond S. Bradley" <rbradley@geo.umass.edu>, Keith Alverson <keith.alverson@pages.unibe.ch>

Dear All,

 Attached the word file that Ray sent you, this time without his electronic
flu. Isabelle is the primary author but is out of town so I am dealing with
it. This is for the PAGES contribution to the IGBP newsletter that will
appear at the time of the congress in Amsterdam.

 If you are able to make some quick comments they would be greatly
appreciated. Although the deadline is technically today, I can probably get
away with early next week. Thanks for your help.

Keith

Ascii version:

Recent Destruction and Alteration of Paleoarchives

Isabelle Larocque and Keith Alverson
PAGES International Project Office

Warming has been measured over most parts of the globe during the late 20th
century. But instrumental data provide only a limited perspective on this
climate change. Because instrumental measurements cover mainly the period of
industrialization, they offer little information with which to distinguish
between natural and anthropogenic causes of the observed warming.
Paleoarchives can provide such information by extending the climate
reconstruction over decadal to millennial temporal scales. Furthermore,
paleodata can be used to predict future ecosystem changes associated with
climate change, based on ecosystem responses to climate changes in the past.
Climatic variables such as temperature, salinity, pH, oxygen level, CO2
concentration, moisture balance and circulation strength can be
quantitatively reconstructed using various biological indicators (pollen,
chironomids, diatoms, cladocereans), isotopes, and other proxy measurements
in lake and ocean sediments, corals, stalagmites, polar ice, tree rings,
mountain glaciers and other paleoarchives. Although tapping the information
contained in these paleoarchives has an enormous potential to contribute to
our understanding of linkages between ecosystems and climate, recent
anthropogenic factors are leading to the destruction of many of these unique
sources of valuable information.

     A first example of destruction of paleoarchives is the ongoing
widespread bleaching of corals. Measurements in corals have been used
successfully to reconstruct sea surface temperature and salinity and even
the surface circulation of the tropical oceans for the past several hundred
years, and for isolated windows during the more distant past, often with a
temporal resolution of only a few weeks (Gagan et al. 2000; Tudhope et al.
2001). Furthermore, corals have recorded past changes in the frequency and
magnitude of El Nino events with direct consequences for predictability.
Coral based reconstructions, for example, indicate a shift from primarily
decadal ENSO variability in the 1800s to the interannual variability of the
last century (Urban et al. 2000). Long coral based records also help to
quantify the significance of the 1976 ENSO shift by providing a longer term
record.

Unfortunately, many corals have been destroyed in recent years. Warming of
surface waters, often associated with El Nino events, has caused several
types of coral to bleach in the Indian and Pacific Oceans (Strong 1998).
Bleaching hurts coral reproduction in two ways: temperature damages
reproductive organs producing fewer, less fit sperm and less eggs and, when
a threshold temperature is crossed, the corals effectively starve themselves
by ridding themselves of zooxhanthellae, the cells they rely on to supply
their energy. Zooxhanthellae are photosynthetic and consume CO2 thereby
making it easier for the corals to calcify. Expulsion of these cells is
causing the white bleached color (Figures 1 and 2). Temperature is not the
only factor causing the bleaching of corals, low salinity events from
extreme episods of river runoff and diseases also contribute to the observed
pattern of increased coral bleaching. While some studies show that corals
can recover from bleaching, the repeated bleaching events forecast as a
consequence of global warming would prevent maturation and recovering
(Normile 2000). Death of corals being used to reconstruct paleoclimate is
not a theoretical problem it is real. As one example, the Urvina Bay coral
study site, the subject of published investigations, was wiped out by the
1982 El Nino and did not recover (T. Guilderson, personal communication).
Scientists predict that as much as 30% of the reefs around the world will
ecologically collapse within 10-20 years (Dawson et al. NOAA). The reefs at
greatest risk are those in Southeast Asia, East Africa, and the Caribbean.
An overview of areas susceptible to bleaching can be found on the internet
at: psbsgil.nesdis.noaa.gov:8080/PSB/EPS/SST/clim&hot.html.

      Not only are coral archives under severe threat: alpine glaciers in
both the tropics and temperate latitudes are melting. Ice cores from such
glaciers have been used to reconstruct temperature, precipitation and
atmospheric dust levels (Thompson 1998), and they provide information about
climate dynamics, including changes in the strength of the Asian monsoon
(Thompson et al. 2000) and ENSO frequency (Moore et al. in press). All
mountain glaciers in tropical and temperate latitudes, with the exception of
those in Scandinavia, are now rapidly retreating. As shown in figure 3, the
volume of the summit glacier on Kilimanjaro (figure 4) has decreased by 81%
between 1912 and 2000 (L. Thompson, personal communication). If this trend
continues, there will soon be no paleoclimatic information stored in ice at
high altitude, low-latitude sites. The only information will be what is left
of the cores extracted last year by Lonnie Thompson and his group and stored
in freezers at Ohio State University. Given the critical importance of the
low latitude regions as drivers of climate on Earth, this loss will
irreplaceably hobble our ability to use the past to predict the future. For
an extensive overview of the status of glaciers around the world, see the
world glacier monitoring service web site (http://www.geo.unizh.ch/wgms/).

Other sources of paleodata have been significantly altered in recent decades
and their integrity as archives is now threatened. The relationships between
tree-ring properties and regional climate parameters for example, are widely
used for reconstructing past climate. At high northern latitudes, tree-ring
densities show a strong correlation with summer temperature. Transfer
functions based estimates of temperature from tree rings in this region are
accurate through the first part of the twentieth century. But during the
second half of the twentieth century, tree width density was no longer
linked to temperature (Briffa et al. 1998). Changes in the reaction of tree
growth to temperature in subarctic Eurasia might be linked to an increase in
winter precipitation that delays the period of growth (Vaganov 1999). Other
possibilities include fertilization effects due to high atmospheric CO2
concentrations or nitrogen-bearing precipitation or the effects of acid rain
or enhanced ultraviolet radiation (Briffa 1998). Irrespective of the exact
cause, it is very possible that this recent significant perturbation in the
ecology of high latitude tree growth is related to human activities.

Similar changes have occurred in chironomid communities in the lakes of
northern Sweden. Chironomid species assemblages recorded in lake sediments
are used to make quantitative reconstruction of mean July air temperature.
This method has been shown to reconstruct lake temperatures accurately
during the last Quaternary period. However, in some lakes there is no modern
analogue for the species assemblages in the most recent sediments (Figure 5,
Bigler Submitted). The absence of correspondence in modern assemblages of
this lake, compared to assemblages in a 100-lake training set in the area,
indicates that factors such as fish introduction or acidification has
modified the "natural" assemblages of this lake. For many
paleoreconstructions, as in both the tree ring and chironomid examples
above, quantification of past temperature changes is based on the concept of
a transfer function. When human influences become so strong that the
organisms used for such reconstruction are no longer reacting directly to
climate but responding instead to other anthropogenic factors, these
transfer functions cannot be applied. By changing biological assemblages or
biological responses of organisms, anthropogenic factors can lead to
potential misinterpretation of ecological responses to future climate change
scenarios.

A major obstacle standing in the way of producing reliable predictions of
climate change and its ecological impacts is a lack of data on timescales
longer than the short instrumental record. Recently initiated international
global climate observation programs will need to be continuously operated
for at least 50 years before they begin to provide information that is
relevant to this problem. Natural archives of past climate variability can
provide the same information now. Unfortunately, as we have argued above,
some of the most valuable paleoclimate archives are being rapidly destroyed,
largely due to human influences. We cannot afford such an irreversible loss.
The IGBP-PAGES Past Global Changes program therefore calls for scientists
and institutional partners to help establish immediately a coordinated
international Global Paleoclimate Observing System (GPOS) to complement the
recently established Global Climate Observing System (GCOS) that focus only
on contemporary observations. There is no time to lose .


Bigler, C., Larocque, I., Peglar, S., Birks, H.J.B., Hall, R.I. (Submitted).
"Holocene environmental change: A quantitative multi-proxy study from a
small lake in Abisko, Swedish Lapland." The Holocene.
Briffa, K. R., F. H. Schweingruber, P. D. Jones, T. J. Osborn, S. G.
Shiyatov and E. A. Vaganov (1998). "Reduced sensitivity of recent
tree-growth to temperature at high northern latitudes." Nature 391: 678-682.
Briffa, K. R., Schweingruber, F.H., Jones, P.D., Osborn, T.J., Harris, I.C.,
Shiyatov, S.G., Vaganov, E.A., Grudd, H. (1998). "Trees tell of past
climates: but are they speaking less clearly today?" Phil. Trans. R. Soc.
Lond. B 353: 65-73.
Gagan, M. K., L. K. Ayliffe, J. W. Beck, J. E. Cole, E. R. M. Druffel, R. B.
Dunbar and D. P. Schrag (2000). "New views of tropical paleoclimates from
corals." Quaternary Science Reviews 19: 45-64.
Moore, G. W. K., G. Holdsworth and K. Alverson (in press). "Extra-Tropical
Response to ENSO 1736-1985 As Expressed In An Ice Core From The Saint Elias
Mountain Range In Northwestern North America." Geophysical Research Letters.
Normile, D. (2000). "Ninth International coral reef symposium: Reef
migrations, bleaching effects stir the air in Bali." Science 290: 1282-1283.
Thompson, L. G., Davies, M.E., Mosley-Thompson, E., Sowers, T.A., Henderson,
K.A., Zagoronov, V.S., Lin, P.-N., Mikhalenko, V.N., Campen, R.K., Bolzan,
J.F., Cole-Dai, J., Francou, B. (1998). "A 25,000-year tropical climate
history from Bolivian ice cores." Science 282: 1858-1864.
Thompson, L. G., T. Yao, E. Mosley-Thompson, M. E. Davis, K. A. Henderson
and P.-N. Lin (2000). "A High-Resolution Millennial Record of the South
Asian Monsoon from Himalayan Ice Cores." Science 289(5486): 1916-1919.
Tudhope, A. W., C. P. Chilcott, M. T. McCulloch, E. R. Cook, J. Chappell, R.
M. Ellam, D. W. Lea, J. M. Lough and G. B. Shimmield (2001). "Variability in
the El Nino-Southern Oscillation Through a Glacial-Interglacial Cycle."
Science 291(5508): 1511-1517.
Urban, F. E., J. E. Cole and J. T. Overpeck (2000). "Influence of mean
climate change on climate variability from a 155-year tropical Pacific coral
record." Nature 407: 989-993.
Vaganov, E. A., Highes, M.K., Kidyanov, A.V., Schweingruber, F.H., Silkin,
P.P. (1999). "Influence of snowfall and meltiming on tree growth in
subarctic Eurasia." Nature 400: 149-151.

Figure Captions:

Figure 1: Unbleached coral  take caption from slideset

Figure 2: Bleached coral  take caption from slideset

Figure 3: Total areal cover of the ice cap on Kilamanjaro from 1912 to
present. Should the measured rate of retreat continue unchanged the ice cap
will have vanished by around 2015. This figure is courtesy of Lonnie
Thompson, unpublished data.

Figure 4: Looking southeast over Kibo (5,895m) and Mawenzi (5,149m) Peaks of
the Kilimanjaro massif. The Northern Icefield is the ice body in the
foreground, draped over the crater rim, and the Western Breach is just to
the right. When Hans Meyer first climbed Kibo in 1889 the crater rim was
nearly encircled by ice, rendering entry to the crater difficult. Today only
a small fraction of this ice remains (~15%); virtually all of the white area
within the crater on this image is seasonal snowcover. Source: Douglas Hardy
(http://www.geo.umass.edu/climate/tanzania/aerial.html) Photo credit: Capt.
G. Mazula (fax +255-51-25551); date of photo unknown.

Figure 5: Mean July temperature reconstructed using chironomids (Diptera:
Chironomidae) in lake Vuoskkujavri, Northern Sweden. A decrease of 1.5 C is
observed through the last 10 000 years. The error bars represent the Root
Mean Square Error of Prediction (RMSEP) of 1.96C. The red  dots indicate
assemblages with no modern-analogues. The first two most recent samples have
no modern analogues, assemblages might have been altered by fish
introduction or acidification.

-- 
Keith Alverson
Executive Director
PAGES International Project Office
Brenplatz 2, 3011 Bern
Switzerland
http://www.pages-igbp.org
Tel: +41 31 312 31 33
Mobile: (+41) 079 641 9220
Fax: +41 31 312 31 68

> From: "Raymond S. Bradley" <rbradley@geo.umass.edu>
> Date: Thu, 10 May 2001 14:45:54 -0400
> To: Keith Alverson <keith.alverson@pages.unibe.ch>
> Cc: jcole@geo.Arizona.EDU, sandy.tudhope@ed.ac.uk, k.briffa@uea.ac.uk,
> mhughes@ltrr.arizona.edu
> Subject: Re: comments?
> 
> I suggest you get input from Julie Cole or Sandy Tudhope on the coral
> business, (what about blowing up reefs?) and Keith Briffa or Malcolm Hughes
> on the tree ring section.  I'm not sure that it is quite as you state, but
> better that they fix it. I'll cc this to all concerned for a hoefully)
> quick response.
> 
> Note I think it's cladocerans, and either speleothems or use stalactites
> --these are most often sampled.
> ray
> 
> At 02:31 PM 05/09/2001 +0200, you wrote:
>> Dear Ray and Tom,
>> 
>> Attached is the draft PAGES contribution to the next IGBP newsletter which
>> will highlight each of the core projects with a few pages. This issue will
>> appear shortly before the Amsterdam congress and will be stuffed in the
>> conference bags. Our submission is due Friday. If you have any comments they
>> would be appreciated.
>> 
>> Keith
>> 
>> -- 
>> Keith Alverson
>> Executive Director
>> PAGES International Project Office
>> Brenplatz 2, 3011 Bern
>> Switzerland
>> http://www.pages-igbp.org
>> Tel: +41 31 312 31 33
>> Mobile: (+41) 079 641 9220
>> Fax: +41 31 312 31 68
>> 
>> 
>> Attachment Converted: "C:\EUDORA\Attach\IGBPnews.doc"
>> 
> 
> 
> 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 Site:
> <http://www.geo.umass.edu/climate/climate.html
> Paleoclimatology Book Web Site (1999):
> http://www.geo.umass.edu/climate/paleo/html
> 



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