February 28, 2007
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 11, NUMBER 7, JULY 1998
"Deep-Sea Coral Evidence for Rapid Change in Ventilation of the Deep
North Atlantic 15,400 Years Ago," J.F. Adkins (Geochem. 62,
Lamont-Doherty Earth Observ., Rte. 9W, Palisades NY 10964),Science,
280(5364), 725-728, May 1, 1998.
Isotopic analysis of coral samples shows that the deep ocean changed on
decadal-centennial time scales during more rapid changes in the surface
ocean and the atmosphere.
Two related items in Science, 279(5355), Feb. 27, 1998:
"Sea Floor Records Reveal Interglacial Climate Cycles," R.A.
Kerr, 1304-1305. New ocean sediment records described in the next paper
show that the Earth's climate varies on regular cycles lasting from 1200
to 6000 years, in glacial and interglacial periods alike. This comment
explains why the finding offers a mixed message of reassurance and warning
about the future of our own climate.
"Abrupt Climate Events 500,000 to 340,000 Years Ago: Evidence from
Subpolar North Atlantic Sediments," D.W. Oppo (Dept. Geol. &
Geophys., Woods Hole Oceanog. Inst., Woods Hole MA 02543), J.F. McManus,
J.L. Cullen, 1335-1341.
"Timing of Abrupt Climate Change at the End of the Younger Dryas
Interval from Thermally Fractionated Gases in Polar Ice," J.P.
Severinghaus (Grad. Sch. Oceanog., Univ. Rhode Island, Narragansett RI
02882), T. Sowers et al.,Nature, 391(6663), 141-146, Jan.
The fractionation of nitrogen and argon isotopes in Greenland ice
indicates a rapid warming that coincides with the onset of a prominent
rise in atmospheric methane concentration. This indicates that the warming
was synchronous (within a few decades) over a region at least hemispheric
Two related items in Science, 278(5342), Nov. 21, 1997:
"Carbon Dioxide and Vegetation," G.D. Farquhar (Biolog. Sci.,
Australian Natl. Univ., Canberra 2601, Australia; e-mail:
email@example.com), 1411. Discusses the research implications of
the following paper.
"Impact of Lower Atmospheric Carbon Dioxide on Tropical Mountain
Ecosystems," F. A. Street-Perrott (Dept. Geog., Univ. Wales, Swansea
SA2 8PP, UK), Y. Huang et al., 1422-1426. Carbon isotope samples taken
over a range of altitudes in Africa show that carbon limitation due to
lower ambient CO2 had a significant impact on the distribution
of forest on the tropical mountains, in addition to climate. Tree line
elevation should not be used to infer paleotemperatures.
"A Pervasive Millennial-Scale Cycle in North Atlantic Holocene and
Glacial Climates," G. Bond (Lamont-Doherty Earth Observ., Rte. 9W,
Palisades NY 10964; e-mail: firstname.lastname@example.org), W. Showers et
al.,Science, 278(5341), 1257-1266, Nov. 14, 1997.
Evidence from North Atlantic deep sea cores reveals abrupt climatic
shifts during the Holocene, the period since the last ice age
conventionally thought to have been quiescent. These and similar but
stronger fluctuations that occurred during the last ice age have a
cyclicity of 1470 (plus or minus 500) years. The Little Ice age appears to
be the most recent cold phase in the series of such cycles. However,
whether the climatic amelioration since the Little Ice Age marks the onset
of a warming phase of this natural cycle is unclear; brief warmings often
punctuated the cold phases of the millenial-scale fluctuations.
Two related items in Nature, 390(6656), Nov. 13, 1997:
"Sudden end of an Interglacial," S. Lehman (INSTAAR, Campus
Box 450, Univ. Colorado, Boulder CO 80309; e-mail:
email@example.com), 117-119. Evidence in the following paper of
sudden climate shifts only adds to the concern about the potential impact
of increased greenhouse forcing on the oceans.
"Variability of the North Atlantic Thermohaline Circulation During
the Last Interglacial Period," J.F. Adkins (Dept. Earth Sci., Mass.
Inst. Technol., Cambridge MA 02139), E.A. Boyl et al., 154-158.
High-resolution ocean sediment records from the Bermuda Rise indicate that
the last interglacial, like the present one, was relatively stable, but it
began and ended with abrupt changes in deep-water flow on a time scale of
less than 400 years.
"The Holocene-Younger Dryas Transition Recorded at Summit, Greenland,"
K.C. Taylor (Desert Res. Inst., Univ. Nevada, Reno NV 89506), P.A.
Mayewski et al.,Science, 278, 825-827, Oct. 31, 1997.
High-resolution analyses of ice cores shows that the transition occurred
over a 40-year period, mostly in a series of steps with duration of about
five years. Changes in atmospheric water vapor are likely to have played a
large role in the climate transition.
Two related items in Nature, 388(6645), Aug. 28, 1997:
"Influence of CO2 Emission Rates on the Stability of
the Thermohaline Circulation," T.F. Stocker (Phys. Inst., Univ. Bern,
Switz.; e-mail: firstname.lastname@example.org), A. Schmittner, 862-865. The
thermohaline circulation of the North Atlantic Ocean, which has a large
influence on climate and CO2 uptake, is sensitive to the level
of atmospheric CO2. This study uses a simple coupled
atmosphere-ocean model to show that the circulation also depends on the
rate of change of CO2. A modeled increase to 750 parts
per million by volume over the next 100 years, corresponding roughly to
today's growth rate, leads to a permanent shutdown of the thermohaline
circulation. But if CO2 increases more slowly, the circulation
merely slows down. This sensitivity to the rate of change of CO2
has potentially important implications for the choice of future CO2-emission
"Risk of Sea-Change in the Atlantic," S. Rahmstorf (Potsdam
Inst. for Clim. Impact Res. [PIK], POB 60 12 03, D-14412 Potsdam, Ger.;
e-mail: email@example.com), 825-826. A research comment on the
previous article, which serves as a reminder that swift action is needed
to reduce the risk of unwelcome climatic surprises.
"A Warm Future in the Past," W.R. Howard (Coop Res. Ctr.
Antarctic, Univ. Tasmania, GPO Box 252-80, Hobart, Tasmania 7001,
Australia),Nature, 388(6641), 418-419, July 31, 1997.
A period 423,000 to 362,000 years ago called stage 11 is a useful analog
for today's climate, because the Earth's orbital geometry was similar to
today's. This article discusses a recent symposium at the Spring 1997 AGU
meeting on that period, which may provide insight into the response of the
natural carbon cycle to future climate change.
"The International Tree-Ring Data Bank: An Enhanced Global Database
Serving the Global Scientific Community," H.D. Grissino-Mayer (Lab.
Tree-Ring Res., Univ. Arizona, Tucson AZ 85721), H.C. Fritts,The
Holocene, 7(2), 235-238, June 1997.
The data bank was created in 1974 and is housed in Boulder, Colorado. It
holds 3275 tree-ring chronologies and 2804 tree-ring measurement data sets
from over 1500 sites, contributed by 139 researchers worldwide. The data
are freely available to all scientists. Future efforts will focus on
increasing the worldwide coverage.
"Younger Dryas Research and Its Implications for Understanding Abrupt
Climate Change," D.E. Anderson (Sch. Geog., Univ. Oxford, Mansfield
Rd., Oxford OX1 3TB, UK),Prog. Phys. Geog., 21(2),
230-249, June 1997.
Reviews studies on the Younger Dryas, the final phase of cold, glacial
conditions preceding the Holocene, and on the North Atlantic thermohaline
circulation (THC). The sensitivity of the THC to changes in freshwater
flux is still unknown, and this poses problems for predicting future
responses. With predicted increases in freshwater input to the North
Atlantic resulting from increased CO2, a future shift in the
THC is a possibility; further research on this sensitivity is imperative.
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