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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 9, NUMBER 6, JUNE 1996

PROFESSIONAL PUBLICATIONS...
PALEOCLIMATOLOGY

Item #d96jun29

"A la Recherche du Temps Perdu," P. Jones, (Clim. Res. Unit, Univ. E. Anglia, Norwich NR4 7TJ, UK), Nature, 381(6581), 375-376, May 30, 1996.

Discusses recent workshops in Australia and New Zealand that have helped exploit a wealth of natural archives (tree rings, corals and ice records) to delineate the nature of climate change over the past 150 years in Oceania (Australia, New Zealand and the South Pacific).

Item #d96jun30

"Warm Climate Surprises," J.T. Overpeck (Paleoclim. Prog., NGDC, NOAA, 325 Broadway, Boulder CO 80303), Science, 271(5257), 1820-1821, Mar. 29, 1996.

Reviews growing paleoclimatic evidence that, even in the absence of human forcing, warm interglacial climates (such as the present Holocene) are capable of generating significant decade- to century-scale climatic surprises, which may be our biggest worry in the years to come. We are beginning to be able to map the patterns of these variations, but unraveling their causes remains a major challenge. If the climate system also turns out to be highly sensitive to elevated trace gas concentrations, we may be confronted with modes of climate variability without precedent.

Item #d96jun31

"Remembrance of Things Past: Greenhouse Lessons from the Geologic Record," T.J. Crowley (Dept. Oceanog., Texas A & M Univ., College Sta. TX 77843), ibid., 2-11.

A review for non-specialists. For most of the last two million years, there is little evidence for global temperatures more than one degree higher than those of the present warm interglacial period. The possibility of an enhanced greenhouse effect thus comes at a time of high temperatures that are rare in the span of human history. Moreover, the concentrations of carbon dioxide and other greenhouse gases are today as high as any that are known in the 200,000 years for which measurements are available, and we know that they played a significant role in climatic changes of the past. While questions remain regarding possible, ameliorating feedbacks from other elements of the climate system, all that is known from the record of the past confirms a direct connection between greenhouse gases and surface temperatures.

Item #d96jun32

"Temperature Depression in the Lowland Tropics in Glacial Times," P.A. Colinvaux (Smithsonian Tropical Res. Inst., POB 2072, Balboa, Panama), K.-B. Liu et al., Clim. Change, 32(1), 19-33, Jan. 1996.

Presents pollen and other data confirming the recently recognized existence of a general tropical cooling during the last ice age. Climate models used to predict future effects of greenhouse gases must also be able to simulate the significant cooling of the large tropical land masses at glacial times with reduced greenhouse gas concentrations.

Item #d96jun33

"Complexity of Holocene Climate as Reconstructed from a Greenland Ice Core," S.R. O'Brien (Paragon Environ. Services Inc., 153 Washington, E. Walpole MA 02032), P.A. Mayewski et al., Science, 270(5244), Dec. 22, 1995.

(See Research News, this Digest issue--June 1996.) Elevated concentrations of sea salt and terrestrial dusts detected in ice cores show that the chemical composition of the atmosphere was dynamic throughout the Holocene epoch. The most recent and abrupt increase coincides with the Little Ice Age. These changes imply that temperatures in the mid-to-high northern latitudes during those periods were potentially the coldest since the Younger Dryas event.

Item #d96jun34

"Profiles of the Past," D.A. Peel (Brit. Antarctic Survey, High Cross, Madingley Rd., Cambridge CB3 0ET, UK), Nature, 378(6554), 234-235, Nov. 16, 1995.

Discusses a joint GISP2-GRIP workshop (Sep. 1995, Wolfeboro, New Hampshire) involving the U.S. and European teams that have been drilling deep ice cores 30 km apart on the Greenland ice cap. Comparison of the two cores has been augmented by new high-resolution data on methane and oxygen, and this approach is helping to forge a long-awaited direct link between the Greenland, Antarctic and marine sediment paleoclimate records. One result suggests that high-latitude climate may be more sensitive than previously thought, and changes in global temperatures may be amplified in the polar regions. (Another account of the workshop appears in EOS, pp. 209, 213, May 28, 1996.)

Item #d96jun35

"Global Interdecadal and Century-Scale Climate Oscillations During the Past Five Centuries," M.E. Mann (Dept. Geol., Yale Univ., POB 208109, New Haven CT 06520), J. Park, R.S. Bradley, Nature, 378(6554), 266-270, Nov. 16, 1995.

Reports a multivariate statistical analysis of a small but global set of high-quality temperature proxy records, extending over several centuries. The results strengthen evidence for persistent, natural interdecadal and century-scale climate oscillations, and reveal both the spatial patterns and temporal histories of these signals.

Item #d96jun36

Two related items in Science, 270(5235), Oct. 20, 1995:

"Challenging an Ice-Core Paleothermometer," D. MacAyeal (Dept. Geophys. Sci., Univ. Chicago, Chicago IL 60637), 444-445. Discusses the following article, which uses temperature profile inversion analysis to challenge and refine the temperature history deduced from the GISP2 ice core. The outcome implies that past estimates of the amount of warming after the last glacial period have been too low, and confirms that polar amplification of climate change is a central characteristic of Earth's climate.

"Large Arctic Temperature Change at the Wisconsin-Holocene Glacial Transition," K.M. Cuffey (Dept. Geol. Sci., Box 351310, Univ. Washington, Seattle WA 98195), G.D. Clow et al., 455-458. Combined analysis of borehole temperature and oxygen isotope composition for the GISP2 Greenland ice core shows that the warming from the last glacial period was 15£ C, about three times the coincident temperature change in the tropics and mid-latitudes.

Item #d96jun37

"International Effort Helps Decipher Mysteries of Paleoclimate from Antarctic Ice Cores," Vostok Project Members (c/o J. Jouzel, Lab. Clim. & Environ. Modeling, Bâitment 709, Orme des Merisiers, CE Saclay, 91191 Gif-sur-Yvette Cedex, France), Eos, 76(17), 169, 179, Apr. 25, 1995.

Summarizes results of studies of ice cores drilled at Vostok Station, Antarctica, over the past ten years by Russia, France and the U.S., which are revealing a wealth of information about past climate and environmental changes over more than a full glacial-interglacial cycle. The data suggest that CO₂ and methane have amplified the initial orbital forcing and account for about half of the glacial-interglacial climate change. They also suggest that positive feedbacks operate in the climate system and support the idea that significant greenhouse warming will occur in the next century.