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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 10, OCTOBER 1993

PROFESSIONAL PUBLICATIONS...
GLOBAL CARBON BUDGET

Item #d93oct29

"Rainforest Burning and the Global Carbon Budget: Biomass, Combustion Efficiency, and Charcoal Formation in the Brazilian Amazon," P.M. Fearnside (Dept. Ecol., Nat. Inst. Res. Amazon, CP 478, 69011-970, Manaus, Amazonas, Brazil), N. Leal Jr., F.M. Fernandes, J. Geophys. Res., 98(D9), 16,733-16,743, Sep. 20, 1993.

Biomass present before and after burning was measured in forest cleared for a cattle ranch. Only about 2.7% of the preburn aboveground carbon stock was converted to charcoal, substantially less than is generally assumed in global carbon models. The high values for biomass found suggest the significant potential contribution of forest burning to climate change from CO₂ and trace gases.

Item #d93oct30

"Atmospheric Carbon Dioxide and the Ocean," U. Siegenthaler (Phys. Inst., Univ. Bern, 3012 Bern, Switz.), J.L. Sarmiento, Nature, 365(6442), 119-125, Sep. 9, 1993.

Evaluates the various recent estimates of the carbon budget, concluding that the ocean takes up about a third of the CO₂ emissions arising from fossil-fuel use and tropical deforestation. This implies that there is a "missing sink" of carbon which may be located in the terrestrial biosphere. Details research needed on the carbon cycle if we are to predict future changes of atmospheric CO₂.

Item #d93oct31

Five items from Global Biogeochem. Cycles, 7(3), Sep. 1993:

"Carbon Remineralization in a North Florida Swamp Forest: Effects of Water Level on the Pathways and Rates of Soil Organic Matter Decomposition," J.D. Happell (Dept. Appl. Sci., Brookhaven Nat. Lab, Upton NY 11973), J.P. Chanton, 475-490. Extensive measurements describe how water level controls CO₂ and CH₄ emissions from North Florida swamp forests. Develops a carbon budget for the site under flooded and dry conditions.

"Can Climate Variability Contribute to the 'Missing' CO₂ Sink?" A. Dai (Dept. Geol. Sci., Columbia Univ., 2880 Broadway, New York NY 10025), I.Y. Fung, 599-610. A study involving empirical models and global temperature and precipitation data shows that climatic variability could have accounted for half the missing CO₂ sink for the period 1950-1984. Climate variations have unequal impacts on biospheric carbon fluxes, and caution is needed in generalizing in situ observations to the globe.

"Is Carbon Accumulating in the Northern Temperate Zone?" R.A. Houghton (Woods Hole Res. Ctr., POB 296, Woods Hole MA 02543), 611-618. Based on recent studies showing an accumulation of carbon in Northern Hemisphere temperate forests, one might conclude that the missing carbon sink has been explained. However, when the fate of wood previously removed from these regrowing forests is considered, the imbalance remains, and is apparently too large to be accommodated in aboveground vegetation anywhere.

"Evaluation of the 13C Constraint on the Uptake of Fossil Fuel CO₂ by the Ocean," W.S. Broecker (Lamont-Doherty Earth Observ., Palisades NY 10964), T.-H. Peng, 619-626. Examines this proposal by Quay et al. (1992) and finds that the data base is too inaccurate to permit a distinction to be made among the carbon budgets currently proposed by this method. Tracer-verified ocean GCMs offer much better estimates than those based on the 13C budget.

"Constraints on the Alkalinity and Circulation of Glacial Circumpolar Deep Water from Benthic Foramniferal Barium," D.W. Lea (Dept. Geol. Sci., Univ. California, Santa Barbara CA 93106), 695-710. Redistribution of ocean alkalinity has been suggested as a possible cause of glacial-to-interglacial CO₂ change. This analysis concludes that such redistribution could account for about a third of the observed p-CO₂ drop.

Item #d93oct32

Special Issue: "Ocean Carbon Cycle and Climate Change," Global & Planetary Change, H.J.W. de Baar, E. Suess, Eds., 8(1-2), July 1993 (Elsevier Sci. Publishers).

Contains a selection of eight papers presented at the Interdisciplinary Union Symposium during the April 1993 meeting of the European Union of Geosciences (Strasbourg). The papers provide a mix of original research findings with overviews of the topic, and deal with the carbon cycle on various time scales.

Item #d93oct33

"Response of the Biosphere to the Changing Global Environment: Evidence from Historic Record of Biotic Metabolism," C.A.S. Hall (Coll. Environ. Sci. Forestry, State Univ. N.Y., Syracuse NY 13210), World Resour. Rev., 5(2), 207-213, June 1993. (See Global Climate Change Digest, Sep. 1993.)

Item #d93oct34

Three items from Global Biogeochem. Cycles, 7(2), June 1993:

"Comparison of Carbon Dynamics in Tropical and Temperate Soils Using Radiocarbon Measurements," S.E. Trumbore (Dept. Geosci., Univ. California, Irvine CA 92717), 275-290. Based on modeling the observed increase of 14C in organic matter pools since atmospheric weapons testing ended, this analysis shows that carbon cycle models, which treat soil carbon dynamics as a single reservoir, underestimate the annual fluxes of organic matter, especially in the tropics.

"CO₂ and CH₄ Dynamics of a Spahghum-Dominated Peatland in West Virginia," J.B. Yavitt (Dept. Natural Resour., Fernow Hall, Cornell Univ., Ithaca NY 14853), R.K. Wieder, G.E. Lang, 259-274. Field measurements suggest that a temperate climate imposed on northern peatlands could mobilize stored carbon and increase CO₂ and CH₄ emission into the troposphere.

"Oceanic 13C/12C Observations: A New Window on Ocean CO₂ Uptake," P.P. Tans (CMDL, NOAA, 325 Broadway, Boulder CO 80303), J.A. Berry, R.F. Keeling, 353-368. Develops equations for the rate of change of carbon isotopic ratios in the atmosphere and ocean in terms of d13C quantities, as a means of estimating the fate of fossil fuel carbon. The isotopic ratio approach has advantages but demands extremely high accuracy in the measurements.

Item #d93oct35

Two items from Nature, 363(6428), June 3, 1993:

"Heavy Carbon Dioxide," R.F. Keeling (Scripps Inst. Oceanog., La Jolla CA 92093), 399-400. Discusses implications of the following paper, which contributes to understanding the behavior of oxygen isotopes in the atmosphere and eventually the "missing carbon sink."

"Vegetation Effects on the Isotope Composition of Oxygen in Atmospheric CO₂," G.D. Farquhar (Plant Environ. Biol. Group, Inst. Advanced Studies, Australian Nat. Univ., GPO Box 475, Canberra, ACT 2601, Australia), J. Lloyd et al., 439-443. Investigates how the fractionation of the oxygen isotopes of CO₂ that occurs in plants influences the global distribution of the isotopes. Results provide an explanation for the depletion of 18O in atmospheric CO₂ at high northern latitudes.

Item #d93oct36

"A New Optical Sensor for P-CO₂ Measurements in Sea Water," N. Lefèvre (Univ. Paris 7, Lab. Gèochim. des Eaux, URA 196 et IPGP, F-75251 Paris Cedex 05, France), J.P. Ciabrini et al., Marine Chem., 42(3-4), 189-198, June 1993. The sensor can remain unattended on an ocean buoy for a full year.

Item #d93oct37

Comment and reply on whether open ocean phytoplankton production has remained constant since the industrial revolution, Nature, 362(6423), 795-796, Apr. 29, 1993.

Item #d93oct38

"A Strategy for Estimating the Impact of CO₂ Fertilization on Soil Carbon Storage," K. Harrison (Lamont-Doherty Earth Observ., Palisades NY 10964), W. Broecker, G. Bonani, Global Biogeochem. Cycles, 7(1), 69-80, Mar. 1993. (See Global Climate Change Digest, Sep. 1993.)

Item #d93oct39

"Winter Biotic Activity and Production of CO₂ in Siberian Soils: A Factor in the Greenhouse Effect," S.A. Zimov (North-East Sci. Sta., Pacific Inst. Geog., Far East Branch, Russian Acad Sci., Vladivostok 690022, Russia), J. Geophys. Res., 98(D3), 5017-5023, Mar. 20, 1993.

Measurements made at 70·N in winter show that biological activity at the bottom of the active layer above the permafrost is sufficient to explain an observed winter maximum in atmospheric CO₂. Ecological and anthropogenic factors may play a role in stimulating this emission.