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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 5, NUMBER 8, AUGUST 1992

PROFESSIONAL PUBLICATIONS...
GLOBAL CARBON CYCLE

(See also: Prof. Pubs./Marine Biogeochemistry & Fertilization, this issue--Aug. 1992.)

Item #d92aug56

"Interactions between Carbon and Nitrogen Dynamics in Estimating Net Primary Productivity for Potential Vegetation in North America," A.D. McGuire (Marine Biol. Lab., Woods Hole MA 02543), J.M. Melillo et al., Global Biogeochem. Cycles, 6(2), 101-124, June 1992.

Describes various experiments using the process-based Terrestrial Ecosystem Model, including evaluation of the importance of interactions between C and N dynamics in the response of North American forest net primary productivity to an elevated temperature of 2° C. The linkages between C and N dynamics are shown to be important in several respects.

Item #d92aug57

"Temperate Forest Ecosystems in the Global Carbon Cycle," R.A. Sedjo (Resour. for the Future, 1616 P St. NW, Washington DC 20036), Ambio, 21(4), 274-277, June 1992.

Newly available data for all the forests of North America, Europe and the former USSR allow a reexamination of the recent conclusion that Northern Hemisphere temperate forests are roughly in carbon balance. Findings indicate that these forests account for a missing carbon sink of about 0.7 Gt annually, a size outside of the range of recent estimates that are commonly used for estimating the global carbon budget.

Item #d92aug58

Three items from Nature, 357(6378), June 11, 1992:

"Packing away Carbon Isotopes," R. Keir (GEOMAR, Christian-Albrechts Univ., 2300 Kiel 14, Ger.), 445-446. The two independent studies described in the following articles find that atmospheric _13C during glacial intervals was probably 0.3%-0.7% lower than in the modern, preindustrial period. Discusses implications for mechanisms determining CO₂ variations between glacial cycles.

"Glacial-to-Interglacial Variations in the Carbon Isotopic Composition of Atmospheric CO₂," B.D. Marino (Dept. Earth & Plan. Sci., Harvard Univ., Cambridge MA 02138), M.B. McElroy et al., 461-466. Samples of a C4 shrub recovered from packrat middens in the western U.S. show that during the last ice age CO₂ was isotopically light compared to interglacial periods. This result is attributed to a combination of factors including reduced terrestrial biomass and decreased productivity of the polar ocean.

"Carbon Isotope Composition of Atmospheric CO₂ during the Last Ice Age from an Antarctic Ice Core," M. Leuenberger (Phys. Inst., Univ. Bern, Sidlerstr. 5, 3012 Bern, Switz.), U. Siegenthaler, C.C. Langway, 488-490. Attempts to distinguish between two possible mechanisms which could have reduced atmospheric CO₂ during glacial intervals: more efficient "biological pumping" of carbon to deep ocean waters, or higher alkalinity in the glacial ocean as a consequence of changes in carbonate dissolution or sedimentation. Results are indefinite, but do indicate that changes in the strength of the biological pump cannot alone have been responsible.

Item #d92aug59

"Carbon Stores in Vegetation," R.A. Kern (Dept. Bot., Duke Univ., Durham NC 27706), W.H. Schlesinger, ibid., 447-448. Comment on the importance of soil carbonate in estimates of the global budget.

Item #d92aug60

"Northern Peatlands: Role in the Carbon Cycle and Probable Responses to Climatic Warming," E. Gorham (Dept. Ecol., Univ. Minnesota, Minneapolis MN 55455), Ecolog. Applic., 1(2), 182-195, May 1991.

Discusses various uncertainties in the carbon and methane budgets of boreal peatlands, particularly for the former USSR. Satellite monitoring of open water in the peatlands of the West Siberian Plain and the Hudson/James Bay Lowland may detect early effects of global warming on these regions.

Item #d92aug61

"Carbon Dioxide Budget in a Temperate Grassland Ecosystem," J. Kim (Dept. Agric. Meteor., Univ. Nebraska, Lincoln NE 65803), S.B. Verma, R.J. Clement, J. Geophys. Res., 97(D5), 6057-6063, Apr. 20, 1992.

Eddy correlation measurements of CO₂ flux combined with simulated data show that CO₂ exchange between the experimental ecosystem and the atmosphere is highly variable. Drought, a frequent occurrence in the region, can change the ecosystem from a source to a sink for CO₂. Results suggest the importance of below-ground biomass in estimating net primary productivity.

Item #d92aug62

"The Global Carbon Dioxide Flux in Soil Respiration and Its Relationship to Vegetation and Climate," J.W. Raich (Dept. Botany, Iowa State Univ., Ames IA 50011), W.H. Schlesinger, Tellus, 44B(2), 81-99, Apr. 1992.

Reviews measured rates of soil respiration from terrestrial and wetland ecosystems to define the annual global CO₂ flux from soils, to identify uncertainties, and to investigate influences on soil respiration rates. Evaluates human impacts on respiration rates, particularly land use, soil fertilization, irrigation and drainage, and climate changes. Increased soil respiration with global warming is likely to provide a positive feedback to the greenhouse effect.

Item #d92aug63

"Global Carbon Dioxide Emission to the Atmosphere by Volcanos," S.N. Williams (Dept. Geol., Arizona State Univ., Tempe AZ 85287), S.J. Schaefer et al., Geochim. Cosmochim. Acta, 56(4), 1765-1770, Apr. 1992.

Calculates emissions from subaerial volcanoes using CO₂/SO2 from volcanic gas analyses and SO2 flux. Volcanic CO₂ presently represents only 0.22% of anthropogenic emissions, but may have contributed to significant greenhouse effects at times in the Earth's history. Models of climate response to CO₂ increase may be tested against geological data.

Item #d92aug64

"Continuous Shipboard Measurement of the pH of Surface Seawaters, and Derivation of the Corresponding Record of pCO₂," E.C.V. Butler (Marine Labs., CSIRO, GPO Box 1538, Hobart, Tasmania 7001, Australia), D.J. Mackey, Sci. Tot. Environ., 112(2-3), 165-175, Mar. 1992. Explains the technique, and discusses measurements of pH and estimates of pCO₂ in the Tasman Sea that reveal regions where the two parameters are highly correlated with temperature and salinity.

Item #d92aug65

"Forest Biomass in Brazilian Amazonia--Comment," P.M. Fearnside (Inst. Nacl. Pesquisas, Caixa Postal 478, BR-69011 Manaus, Brazil), Interciencia, 17(1), 19-27, Jan.-Feb. 1992.

Describes a variety of adjustments that should be made to the estimates of biomass by Brown and Lugo using forest volume data collected by the RADAMBRASIL Project and the U.N. FAO. Revised estimates indicate a substantial contribution to greenhouse emissions from deforestation in Brazilian Amazonia.

Item #d92aug66

"Oceanic Sinks for Anthropogenic CO₂," C.L. Sabine (Dept. Oceanog., Univ. Hawaii, Honolulu HI 96822), F.T. Mackenzie, Intl. J. Energy, Environ., Econ., 1(2), 119-127, 1991.

Discusses the impact of human activities on the geological cycle of CO₂, quantifies the major oceanic sinks of anthropogenic CO₂, and reassesses the oceanic sink of CO₂ owing to dissolution of calcium carbonate, using data from the Hawaiian Archipelago. Fluxes associated with the last process may become greatly enhanced in the future if society continues its present practices.

Item #d92aug67

"A Simple Inverse Carbon Cycle Model," T.M.L. Wigley (Clim. Res. Unit, Univ. E. Anglia, Norwich NR4 7TJ, UK), Global Biogeochem. Cycles, 5(4), 373-382, Dec. 1991.

Derives a practical and efficient inverse model from the convolution integral form of a carbon cycle model. An example shows how modeled land-use-change emissions over 1765-1989 vary with assumptions made regarding the efficiency of oceanic uptake.