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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 6, NUMBER 6, JUNE 1993

PROFESSIONAL PUBLICATIONS...
GENERAL INTEREST--SCIENCE: CLIMATE CHANGE

Item #d93jun16

"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.

Item #d93jun17

"A 3620-Year 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.

Item #d93jun18

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.

Item #d93jun19

"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.

Item #d93jun20

"Palaeoclimate 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.

Item #d93jun21

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 climate mechanism.

Item #d93jun22

"Pliocene 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.

Item #d93jun23

"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.

Item #d93jun24

"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, 1992.

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 internal feedbacks.