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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 3, MARCH 1993

PROFESSIONAL PUBLICATIONS...
GENERAL INTEREST--SCIENCE

Item #d93mar10

"Active Volcanism beneath the West Antarctic Ice Sheet and Implications for Ice-Sheet Stability," D.D. Blankenship (Inst. Geophys., Univ. Texas, Austin TX 78759), R.E. Bell et al., Nature, 361(6412), 526-529, Feb. 11, 1993.

The response of the West Antarctic ice sheet to climatic change is a concern because its collapse would cause a global sea level rise of 6 meters. This paper presents evidence for active volcanism and associated heat flow beneath the sheet where ice streaming begins, raising the possibility that the stability of the sheet is controlled by geological conditions independent of climate, and that penetration of ocean water sufficiently inland could trigger collapse. (See Res. News.)

Item #d93mar11

Three related items from Nature, 361(6412), Feb. 11, 1993:

"Carbon Reserves Released?" R.S. Webb (Nat. Geophys. Data Ctr., 325 Broadway, Boulder CO 80303), J.T. Overpeck, 497-498. Although in the long term it seems that increased atmospheric CO₂ will lead to increased terrestrial carbon storage, the following two studies show that global warming could add to the CO₂ burden over short durations (50-100 years).

"Recent Change of Arctic Tundra Ecosystems from a Net Carbon Dioxide Sink to a Source," W.C. Oechel (Dept. Biol., San Diego State Univ., San Diego CA 92182), S.J. Hastings et al., 520-523. Presents data indicating that the tundra on the North Slope of Alaska, a net carbon sink during historic and recent geologic times, has recently become a source of CO₂, coincident with recent warming in the Arctic. Regardless of the cause of the recent warming, results suggest that tundra ecosystems may exert a positive feedback on atmospheric CO₂ and any greenhouse warming.

"The Transient Response of Terrestrial Carbon Storage to a Perturbed Climate," T.M. Smith (Dept. Environ. Sci., Univ. Virginia, Charlottesville VA 22903), H.H. Shugart, 523-526. Results from two GCMs show that vegetation and soil changes could be significant sources of CO₂ following greenhouse warming, increasing atmospheric concentrations by up to a third of the present level.

Item #d93mar12

Two related items from Nature, 361(6411), Feb. 4, 1993:

"Flickers within Cycles," S. Lehman (Woods Hole Oceanog. Inst., Woods Hole MA 02543), 404-405. Results such as those in the following entry pose climatologists and policy makers with a dilemma: how long will we have to wait before we are convinced that we are seeing or not seeing a greenhouse signal?

"The `Flickering Switch' of Late Pleistocene Climate Change," K.C. Taylor (Desert Res. Inst., Univ. Nevada, Reno NV 89512), G.W. Lamorey et al., 432-436. Electrical conductivity measurements from a Greenland ice core reveal a previously unrecognized mode of rapid climate variation--fluctuations of the scales of <5-20 years, reflecting oscillations in the dust content of the atmosphere. This `flickering' between two climatic states would seem to require rapid reorganizations in atmospheric circulation.

Item #d93mar13

Two related items from ibid.:

"Learning from the Past," V. Baker (Dept. Geosci., Univ. Arizona, Tucson AZ 85721), 402-403. Comments on the science and policy implications of the following entry.

"Large Increases in Flood Magnitude in Response to Modest Changes in Climate," J.C. Knox (Dept. Geog., Univ. Wisconsin, Madison WI 53706), 430-432. A 7,000-year geological record of overbank floods for upper Mississippi river tributaries provides concrete evidence for a high sensitivity of flood occurrence to changing climate. Greatly differing flood magnitudes were associated with mean annual temperature changes of only 1·-2·C.

Item #d93mar14

Two related items from Nature, 361(6410), Jan. 28, 1993:

"The Elusive Arctic Warming," J.E. Walsh (Dept. Atmos. Sci., Univ. Illinois, Urbana IL 61801), 300-301. Although the findings of the following entry apparently run counter to model predictions of greenhouse warming, they are not necessarily at odds when viewed in a broader context.

"Absence of Evidence for Greenhouse Warming over the Arctic Ocean in the Past 40 Years," J.D. Kahl (Dept. Geosci., Univ. Wisconsin-Milwaukee, POB 413, Milwaukee WI 53201), D.J. Charlevoix et al., 335-337. Analysis of over 27,000 temperature profiles for the period 1950-1990 shows no evidence of the large surface warming trends predicted by models. The discrepancy suggests that present climate models do not adequately incorporate the physical processes important in the polar regions.

Item #d93mar15

Two related items from Nature, 361(6409), Jan. 21, 1993:

"Northward March of Spruce," J. Pastor (Natural Resour. Res. Inst., Univ. Minnesota, Duluth MN 55811), 208-209. Discusses the following entry, and some questions it raises.

"Rapid Response of Treeline Vegetation and Lakes to Past Climate Warming," G.M. MacDonald (Dept. Geog., McMaster Univ., Hamilton ON L8S 4K1, Can.), T.W.D. Edwards et al., 243-246. Presents paleoecological evidence for changes in terrestrial vegetation and lake characteristics during an episode of climate warming 4,000-5,000 years ago in Canada. The initial transformation--from tundra to forest-tundra--took only 150 years, roughly the time period used in modeling the response of boreal forests to greenhouse warming.

Item #d93mar16

"Long-Term Solar Brightness Changes Estimated from a Survey of Sun-Like Stars," G.W. Lockwood (Lowell Observ., 1400 W. Mars Hill Rd., Flagstaff AZ 86001), B.A. Skiff et al., Nature, 360(6405), 653-655, Dec. 17, 1992.

Presents a compilation of observations of 33 Sun-like stars, which show year-to-year brightness changes that greatly exceed analogous solar fluctuations. Results suggest that the Sun is in an unusually steady phase compared to similar stars, and that reconstructing the past historical brightness record from sunspot records (to interpret temperature trends) may be more risky than generally thought.

Item #d93mar17

"Marine Sciences in the Coming Decades," C. Wunsch (Dept. Earth Sci., Mass. Inst. Technol., Cambridge MA 02139), Science, 259(5093), 296-297, Jan. 15, 1993.

Discusses a trend toward steady or declining support for marine sciences and possible remedies, the subject of the recent National Academy of Sciences report Oceanography in the Next Decade.

Item #d93mar18

"Remote Sensing of Oceanic Biology in Relation to Global Climate Change," J. Aiken (NERC Plymouth Marine Lab., Prospect Pl. W. Hoe, Plymouth PL1 3DH, UK), G.F. Moore, P.M. Holligan, J. Phycol., 28(5), 579-590, Oct. 1992.

A review of the wealth of information that has been obtained from the Coastal Zone Color Scanner (CZCS) and from newer sensors such as SeaWiFS. Discusses information still needed for climate change research, such as fluxes of DMS relevant to cloud-climate interactions.