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FROM VOLUME 6, NUMBER 5, MAY 1993

PROFESSIONAL PUBLICATIONS...
GENERAL INTEREST--SCIENCE

Item #d93may6

Special section: "Evolution of Atmospheres," Science, 259(5097), Feb. 12, 1993. Contains the following research reviews, as well as several perspective articles.

"The Global Carbon Dioxide Budget," E.T. Sundquist (U.S. Geol. Surv., Quissett Campus, Woods Hole MA 02543), 934-941. Although the increase in atmospheric CO₂ during the last deglaciation was comparable in magnitude to the recent historical increase, mechanisms differ for the two intervals. For instance, the modern oceans are a rapid net CO₂ sink, while they were a gradual source during the deglaciation. Unidentified terrestrial CO₂ sinks are important uncertainties in both the deglacial and recent CO₂ budgets; the deglacial budget is inadequately addressed by current models used to forecast future atmospheric CO₂ levels.

"The Ice Record of Greenhouse Gases," D. Raynaud (Lab. Glac. & Geophys. de l'Environ., BP 96, F-38402 St.-Martin-d'Heres Cedex, France), J. Jouzel et al., 926-934. The best-documented trace-gas records from polar ice are for CO₂ and CH₄. Measurements corresponding to the industrial period document the recent changes in growth rate, and the variability observed over the last 1000 years constrains the possible feedbacks of a climate change on the trace gases under similar conditions as today's. Other characteristics of the ice record suggest that greenhouse gases are important in amplifying the initial orbital forcing of Earth's climate, and help to assess the feedbacks on the biogeochemical cycles in a climate system in which the components are changing at different rates.

"Earth's Early Atmosphere," J.F. Kasting (Dept. Geosci., Pennsylvania State Univ., Univ. Pk. PA 16802), 920-926.

"Atmospheric Evolution of the Terrestrial Planets," D.M. Hunten (Lunar & Planet. Lab., Univ. Arizona, Tuscon AZ 85721), 915-920.

Item #d93may7

"Global Warming from Chlorofluorocarbons and Their Alternatives: Time Scales of Chemistry and Climate," M.K.W. Ko (Atmos. & Environ. Res. Inc., 840 Memorial Dr., Cambridge MA 02139), N.D. Sze, G. Molnar, Atmos. Environ., 27A(4), 581-587, Mar. 1993.

Applies a simple model to illustrate a method for determining the time variations of the radiative forcing and temperature changes attributable to the direct greenhouse effect from potential emissions of halocarbons. Despite uncertainties inherent in the analysis, it illustrates an important aspect of the greenhouse warming issue beyond what is provided by various greenhouse warming indices. Calculations show that the warming due to halocarbons will correspond to 4-10% of the total expected greenhouse warming in the year 2100. However, uncontrolled growth of substitutes could cause an eight-fold increase in halocarbon production and a doubling of the halocarbon contribution by then.

Item #d93may8

"Large-Scale Dynamics and Global Warming," I.M. Held (GFDL, Princeton Univ., POB 308, Princeton NJ 08542), Bull. Amer. Meteor. Soc., 74(2), 228-241, Feb. 1993.

This review of a variety of issues in large-scale atmospheric and oceanic dynamics concludes that we cannot expect a theoretical (necessarily computational) approach to climate, in isolation, to yield a totally convincing prediction of climatic sensitivity in the near future.

Item #d93may9

"Using a Closed Ecological System to Study Earth's Biosphere: Initial Results from Biosphere 2," M. Nelson (Space Biosphere Ventures, Oracle AZ 85623), T.L. Burgess et al., BioScience, 43(4), 225-236, Apr. 1993.

Biosphere 2 has operated successfully since September 1991 as a closed microbiosphere including humans, maintaining the overall health of its diversity of internal ecosystems and a large proportion of its species. Biogeochemical cycles are operating, at least on the short term, with strong daily and seasonal fluxes of atmospheric CO₂, although oxygen concentration is declining. Overall system biomass continues to increase, with woodland canopies rapidly developing in rainforest, savannah, and marsh. Although there are, as yet, no other natural biospheres known for comparison to Earth, synthetic biospheres open prospects for comparative biospherics and better understanding of the Earth system. (See related item in Research News.)

Item #d93may10

"Velocity Structure of a Gas Hydrate Reflector," S.C. Singh (Bullard Labs., Madingley Rd., Cambridge CB3 0EZ, UK), T.A. Minshull, G.D. Spence, Science, 260(5105), 204-207, Apr. 9, 1993.

Presents a method for measuring the amount of methane trapped beneath methane hydrate layers along continental margins, using seismic reflection profiles. Results from a site of the Ocean Drilling Program suggest that methane hydrate and the underlying gas represent a large global reservoir of methane, which may have economic importance and may influence global climate.