February 28, 2007
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A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 6, NUMBER 6, JUNE 1993
GENERAL INTEREST--SCIENCE: CLIMATE CHANGE
"Net Exchange of CO2
in a Mid-Latitude Forest," S.C. Wofsy (Dept. Earth Sci., Harvard Univ.,
Cambridge MA 02138), M.L. Goulden et al., Science,
260(5112), 1314-1317, May 28, 1993.
Eddy correlation measurements spanning two growing seasons in a
Massachusetts forest indicate a gross ecosystem production of 11.1 metric tons
of carbon per hectare per year, reflecting recovery from agricultural
development in the 1800s. Carbon uptake rates are notably larger than those
assumed for temperate forests in global carbon studies, implying an important
role for temperate forests in determining future levels of carbon dioxide.
Temperature Record from Fitzroya cupressoides Tree Rings in Southern
South America," A. Lara (Inst. Silvicultura, Univ. Austral de Chile,
Casilla 567, Valdivia, Chile), R. Villalba, Science,
260(5111), 1104-1106, May 21, 1993.
Both proxy and instrumental climate records are scant for the Southern
Hemisphere compared to the Northern Hemisphere. This record shows a long
interval with above-average temperatures from 80 B.C. to A.D. 160; below-average
intervals occurred from A.D. 300 to 470 and A.D. 1490 to 1700. Neither this
record nor instrumental data for the middle southern latitudes provide evidence
of a warming trend during the past decades of this century that could be related
to anthropogenic causes.
Two related items from
Nature, 363(6426), May 20, 1993:
"Global Climate Change and Terrestrial Net Primary Production,"
J.M. Melillo (Marine Biolog. Lab., Woods Hole MA 02543), A.D. McGuire et al.,
234-240. Used a process-based model to estimate global patterns of net primary
production and soil nitrogen cycling for contemporary climate conditions and
atmospheric CO2 concentrations, as well as for a doubled CO2 climate. Responses
to the latter in tropical and dry temperate ecosystems were dominated by CO2,
but those in northern and moist temperate ecosystems reflected the effects of
temperature on nitrogen availability.
"Process and Production," I.C. Prentice (Dept. Ecol., Lund Univ., Östra
Vallgatan 14, S-223 61, Lund, Sweden), 209-210. Discusses implications of the
previous paper, the advantages of process-based models over simple regression
approaches, and how the biosphere can produce both positive and negative
feedbacks to CO2-induced warming.
"Coral Bleaching as
an Adaptive Mechanism: A Testable Hypothesis," R.W. Buddemeier (Kansas
Geolog. Surv., Lawrence KS 66047), D.G. Fautin, BioScience, 43(5),
320-326, May 1993.
Coral bleaching, suggested by some as a possible indication of climate
change, may be a basic physiological attribute that allows a host coral to adapt
to changed conditions by becoming repopulated with a different algal partner.
Discusses how to test the hypothesis, and implications for research.
Sensitivity," Nature, 363(6424), 25-26, May 6, 1993.
Comment by R. Lindzen on the technique used by Hoffert and Covey to infer
climate sensitivity to a doubling of CO2 from climatic trends.
Two related items from
Nature, 362(6420), Apr. 8, 1993:
"Flip-Flop End to Last Ice Age," R.G. Fairbanks (Lamont-Doherty
Earth Observ., Palisades NY 10964), 495. Discusses implications of the following
study, and their bearing on the politically charged question of whether an
abrupt climatic change is possible under present conditions.
"Abrupt Increase in Greenland Snow Accumulation at the End of the
Younger Dryas Event," R.B. Alley (Dept. Geosci., Pennsylvania State Univ.,
Univ. Pk. PA 16802), D.A. Meese et al., 527-529. Oxygen isotope data from a
Greenland ice core suggests that snow accumulation doubled rapidly during the
end of the last glaciation, possibly over one to three years. The extreme
rapidity of this and other changes that directly represent regional climate
imply the existence of some sort of threshold or trigger in the North Atlantic
Paleoclimate and East Antarctic Ice-Sheet History from Surficial Ash Deposits,"
D.R. Marchant (Inst. Quatern. Studies, Univ. Maine, Orono ME 04469), C.C.
Swisher III et al., Science, 260(5108), 667-670, Apr. 30, 1993.
Dating of geologic deposits in the Dry Valleys region of Antarctica indicate
that the present East Antarctic Ice Sheet has existed for the past 4.3 million
years, implying that the collapse of the sheet due to greenhouse warming is
unlikely, even if global atmospheric temperatures rise to levels last
experienced during mid-Pliocene times.
"The Relative Roles
of Sulfate Aerosols and Greenhouse Gases in Climate Forcing," J.T. Kiehl
(NCAR, POB 3000, Boulder CO 80307), B.P. Briegleb, Science, 260(5106),
311-314, Apr. 16, 1993.
Uses a simple two-layer radiation model to calculated the direct effects of
both natural and anthropogenic tropospheric sulfate aerosols, brought about by
reflecting solar radiation back to space. The globally averaged aerosol forcing
is -0.3 watts per square meter compared to +2.1 watts per square meter for
greenhouse gases, but summer aerosol forcing over the eastern U.S. and central
Europe completely offsets greenhouse forcing.
"Solar Forcing of
the Global Climate System," J.L. Jirikowic (Dept. Geosci., Univ. Arizona,
Tucson AZ 85721), P.E. Damon, World Resour. Rev., 4(1), 82-111,
Presents a review of solar forcing of terrestrial climate for the
non-specialist. The history of past solar variations does not support the recent
suggestion that decreasing solar activity during the next century will
ameliorate warming due to greenhouse gases. The greatest remaining uncertainties
are the sensitivity of the climate system to solar forcing and the nature of any
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