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A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 10, NUMBER 11, NOVEMBER 1997

PROFESSIONAL PUBLICATIONS...
CARBON CYCLE

Item #d97nov5

Two related papers in Nature, 389(6654), Oct. 30, 1997:

"The Ocean's Productive Deserts," S.C. Doney (NCAR, POB 3000, Boulder CO 80307; e-mail: doney@ucar.edu), 905-906. Comments on the following paper, which shows, for perhaps the first time, that we can systematically close the carbon budget for the upper ocean.

"Experimental Determination of the Organic Carbon Flux from Open-Ocean Surface Waters," S. Emerson (Sch. Oceanog., Univ. Washington, Seattle WA 98195; e-mail: emerson@u.washington.edu), P. Quay et al., 951-954. Accurate determination of the flux of biologically produced organic carbon to deep waters is critical to understanding the global C cycle and its responses to climate change. This study compares results from three independent estimates, which show that the typical carbon export flux in the subtropical ocean, often considered to be a biological desert, may be responsible for up to half of the global-ocean biological organic carbon sink.

Item #d97nov6

"Carbon Balance of a Temperate Poor Fen," P. Carroll (Complex Systems Res. Ctr., Univ. New Hampshire, Durham NH 03824; e-mail: carroll@kaos.sr.unh.edu), P. Crill,Global Biogeochem. Cycles, 11(3), 349-356, Sep. 1997.

Field measurements and simple modeling of a Sphagnum dominated wetland in New Hampshire suggest that if future climate change brings warmer temperatures and lower water tables to peatland soils, positive climatic feedback leading to substantial releases of CO₂ from boreal and subarctic peatlands is probable.

Item #d97nov7

Two related papers in Nature, 388(6642), Aug. 7, 1997:

"Inside the Black Box," R. Norby (Environ. Sci. Div., Oak Ridge Natl. Lab., Bldg. 1059, POB 2008, Oak Ridge TN 37831), 522-523. Comments on the following research, which shows that exposure of grasslands to doubled CO₂ causes carbon to cycle through the systems faster but increases carbon accumulation little. Even so, a faster cycling rate could induce myriad changes in species diversity and functions, which in themselves could alter the carbon pool.

"The Fate of Carbon in Grasslands Under Carbon Dioxide Enrichment," B.A. Hungate (Smithsonian Environ Res. Ctr., Edgewater MD 21037), E.A. Holland et al., 576-579. Grassland ecosystems exposed to three years of doubled CO₂ show a greater increase in carbon cycling than in carbon storage.

Item #d97nov8

"Variations in the Predicted Spatial Distribution of Atmospheric Nitrogen Deposition and Their Impact on Carbon Uptake by Terrestrial Ecosystems," E.A. Holland (NCAR, POB 3000, Boulder CO 80307; e-mail: eholland@ncar.ucar.edu), B.H. Braswell et al.,J. Geophys. Res., 102(D13), 15,849-15,866, July 20, 1997.

Widespread deposition of atmospheric nitrogen from industry, agriculture, and biomass burning can alleviate the nitrogen limitation of productivity in terrestrial ecosystems, and may increase carbon uptake. This effect was evaluated with output from five different 3-D chemical models, used to drive a perturbation model of terrestrial carbon uptake. Global air pollution appears to be an important influence on the global carbon cycle, and if this fertilization effect accounts for the "missing" carbon sink, we would expect significant reductions in the magnitude of that sink over the next century as terrestrial ecosystems become nitrogen saturated.

Item #d97nov9

"Vulnerability of Russian Forests to Climate Changes. Model Estimation of CO₂ Fluxes," A.L. Lelyakin (Inst. Global Clim. & Ecol., Glebovskaya 20b, 107258 Moscow, Russia), A.O. Kokorin, I.M. Nazarov, Clim. Change, 36(1-2), 123-133, June 1997.

Uses a model that includes forest age distribution, various carbon reservoirs, and logging and fires, to estimate a current Russian forest sink of 160 MtC/yr, a number that will grow to 200-240 Mt/yr in 2010. The main future uncertainty is forest response to climate change.

Item #d97nov10

"Oceanic Dissolved Organic Carbon Is the Main Sink of Atmospheric CO₂," V.G. Gorshkov (Petersburg Nuclear Phys. Inst., Gatchina, 188350 Leningrad District, Russia), World Resource Review, 9(2), 153-169, June 1997.

Analyzes data on the distribution of prebomb and postbomb 14C in the ocean, concluding that the production of oceanic dissolved organic carbon (DOC) has increased twenty-fold during the industrial era, while DOC destruction has remained unchanged. The resulting increase of DOC mass by 2 Gt/yr coincides with an estimate of carbon release by terrestrial biota based on land use, and resolves the problem of the "missing" carbon sink.

Item #d97nov11

"Accounting for Biological and Anthropogenic Factors in National Land-Base Carbon Budgets," D.P. Turner (Forest Sci. Dept., Oregon State Univ., Corvallis OR 97331), J.K. Winjum et al.,Ambio, 26(4), 220 ff., June 1997.

To compare net CO₂ fluxes and identify key research areas, analyzes data on current land use, rates of land-cover change, forest harvest levels, and wildfire extent under a common framework for three countries (the U.S., Former Soviet Union, and Brazil). Continued database development and close attention to methods of quantifying carbon flux will be necessary if carbon budget assessments are to be useful for policy makers.

Item #d97nov12

"Cold Season CO₂ Emissions from Arctic Soils," W.C. Oechel (Global Change Res. Group, San Diego State Univ., San Diego CA 92182; e-mail: oechel@sunstroke.sdsu.edu), G. Vourlitis, S.J. Hastings, Global Biogeochem. Cycles, 11(2), 163-172, June 1997.

Significant amounts of CO₂ loss were observed in Arctic tundra ecosystems of the Alaskan North Slope during the 1993-94 season. Estimates of annual net CO₂ exchange, based on warm season measurements alone, underestimate the actual magnitude of CO₂ efflux.

Item #d97nov13

"An Integrated Modeling Approach to Global Carbon and Nitrogen Cycles: Balancing Their Budgets," M.G.J. den Elzen (Global Dynamics & Sustainable Development, Natl. Inst. Public Health & Environ.-RIVM, POB 1, NL-3720 BA Bilthoven, Neth.), A.H.W. Beusen, J. Rotmans,Global Biogeochem. Cycles, 11(2), 191-215, June 1997.

Integrated but simple models of the coupled carbon-nitrogen cycle and climate show that N fertilization feedback may be important for balancing the past carbon budget, and that nutrient limitation can seriously limit CO₂ fertilization feedback. Both mechanisms should be examined in more detailed carbon cycle models, and if the results are confirmed, should be incorporated into IPCC projections.

Item #d97nov14

"The Decoupling of Terrestrial Carbon and Nitrogen Cycles," G.P. Asner (CIRES, Univ. Colorado, Boulder CO 80309),BioScience, 47(4), 226-232, Apr. 1997.

Reviews how human influences on land cover and nitrogen supply are altering natural biogeochemical links in the biosphere, and how the terrestrial carbon cycle will respond to and influence changes in atmospheric CO₂ and temperature. Although elevated levels of nitrogen and CO₂ are stimulating the uptake of anthropogenic CO₂, the effect is only temporary. The rapidly changing global nitrogen cycle, with its increasing nitrogen depositon, can also lead to increases in greenhouse gases such as methane, nitrous oxide, and tropospheric ozone, which counterbalance the uptake of CO₂. As natural linkages between the terrestrial carbon and nitrogen cycles continue to deteriorate in coming decades, such changes are likely to become even more pronounced.

Item #d97nov15

"Historical Variations in Terrestrial Biospheric Carbon Storage," W.M. Post (Environ. Scil Div., Oak Ridge Natl. Lab., POB 2008, Oak Ridge TN 37831; e-mail: wmp@ornl.gov), A.W. King, S.D. Wullschleger,Global Biogeochem. Cycles, 11(1), 99-109, Mar. 1997.

Investigates the source of the missing sink needed to balance the contemporary atmospheric CO₂ budget with anthropogenic emissions, by driving a high-resolution global terrestrial biosphere model with historical time series of temperature and precipitation and the historical record of changes in atmosphere CO₂. Results suggest that the temporal evolution of the missing sink over the period 1900-1988 could be a response of the terrestrial biosphere to changes in climate and CO₂ or perhaps changes in climate alone.

Item #d97nov16

"The Potential Response of Terrestrial Carbon Storage to Changes in Climate and Atmospheric CO₂," A.W. King (Environ. Sci. Div., Oak Ridge Natl. Lab., Oak Ridge TN 37831; e-mail: awk@ornl.gov), W.M. Post, S.D. Wullschleger, Clim. Change, 35(2), 199227, Feb. 1997.

Uses a georeferenced model of ecosystem dynamics to explore the sensitivity of terrestrial C storage to changes in atmospheric CO₂ and climate. With a doubling of CO₂, the model projects increases in NPP of 30-36%, and increases in terrestrial ecosystem carbon of 15-18%.

Item #d97nov17

"Survey of CO₂ in the Oceans Reveals Clues About Global Carbon Cycle," C.L. Sabine (Geosci. Dept., Guyot Hall, Princeton Univ., Princeton NJ 08544), D.W.R. Wallace, F.J. Millero, Eos, Trans. Amer. Geophys Union, 78(5), 49, 54-55, Feb. 4, 1997.

Describes a project involving 10 U.S. universities and national laboratories working since 1990 to develop a high-quality inorganic carbon data set for all the world's oceans. The survey, done in collaboration with the World Ocean Circulation Experiment, has been highly successful, and data are just starting to become available. (See this Web site: http://cdiac.esd.ornl.gov/cdiac/oceans/home.html.)

Item #d97nov18

"Potential for Carbon Sequestration in European Soils: Preliminary Estimates for Five Scenarios Using Results from Long-Term Experiments," P. Smith (Soil Sci. Dept., IACR-Rothamsted, Harpenden, Herts AL5 2JQ, UK; e-mail: pesmith@bbsrc.ac.uk), D.S. Powlson et al.,Global Change Biology, 3(1), 67-79, Feb. 1997.

Uses statistical relationships derived from long-term European experiments to explore the potential of five scenarios: amendment of arable soils with animal manure or sewage sludge; incorporation of cereal straw into soils; afforestation of surplus arable land through natural regeneration; and a shift to less-intensive use of agricultural land through increased animal grazing. Concludes that, although efforts in temperate agriculture can contribute to global carbon mitigation, the potential is small compared to that available through reducing anthropogenic CO₂ emissions by halting tropical and sub-tropical deforestation, or by reducing fossil fuel burning.

Item #d97nov19

"Influence of Nitrogen Loading and Species Composition on the Carbon Balance of Grasslands," D.A. Wedin (Dept. Bot., Univ. Toronto, Toronto M5S 3B2, Can.; e-mail: wedin@botany.utoronto.ca), D. Tilman,Science, 274(5293), 1720-1723, Dec. 6, 1996.

A 12-year experimental study of nitrogen deposition on Minnesota grasslands shows that in the short term, nitrogen stimulates growth and carbon storage in plant tissues. But added nitrogen also pushes the species mix toward fast-growing, invasive species that are inefficient at fixing carbon in the long term. (See news articles in Science, pp. 1610-1611, Dec. 6, 1996; New Scientist, p. 16, Dec. 14, 1996; The New York Times, pp. C1, C12, Dec. 10, 1996; also correspondence in Science, pp.739-741, Feb. 7, 1997.)

Item #d97nov20

"Two Decades of Carbon Flux from Forests of the Pacific Northwest--Estimates from a New Modeling Strategy," W.B. Cohen (Forestry Sci. Lab., USDA Forest Serv., 3200 SW Jefferson Way, Corvallis OR 97331), M.E. Harmon et al.,BioScience, 46(11), 836-843, Nov. 1996.

Describes a strategy being developed for estimating regional carbon fluxes using remotely sensed and spatial biogeoclimatic data, and a pilot study in the Pacific Northwest of the U.S. that demonstrates its value.

Item #d97nov21

"Temperate Forest Responses to Carbon Dioxide, Temperature and Nitrogen: A Model Analysis," J.H.M. Thornley (Inst. Terrestrial Ecol.-ITE, Bush Estate, Penicuik, Midlothian EH26 0QB, UK), M.G.R. Cannell,Plant, Cell & Environ., 19(12), 1331-1348, Dec. 1996.

Used the ITE Edinburgh Forest model, one of the most comprehensive models of its kind, which describes diurnal and seasonal changes of C, N, and H2O in a fully coupled forest-soil system. Simulated a managed conifer plantation in upland Britain to examine transient effects on forest growth of an IS92a scenario of increasing CO₂ and temperature over two future rotations, and the equilibrium effects of all combinations of increased CO₂, mean annual temperature and annual inputs of N. Details eight major conclusions, which may lead to decreases or increases of growth. Projected increases in CO₂ and temperature (IS92a) are likely to increase net ecosystem productivity and carbon sequestration in temperate forests.

Item #d97nov22

"Oceanic Carbon Dioxide Uptake in a Model of Century-Scale Global Warming," J.L. Sarmiento (Program in Atmos. & Oceanic Sci., Princeton Univ., Princeton NJ 08544),Science, 274(5291), 1346-1350, Nov. 22, 1996.

In a model of ocean-atmosphere interaction that excluded biological processes, global warming substantially reduced the oceanic uptake of atmospheric CO₂, primarily through the weakening or collapse of the ocean thermohaline circulation. Such a large reduction in uptake would have a major impact on the future growth rate of atmospheric CO₂. Simulations incorporating biological effects show that they could largely offset this reduction, but the magnitude of the offset is difficult to quantify with present knowledge.

Item #d97nov23

"Historical Biomass Burning: Late 19th Century Pioneer Agriculture Revolution in Northern Hemisphere Ice Core Data and Its Atmospheric Interpretation," G. Holdsworth (Arctic Inst. of North America, Univ. Calgary, Calgary AB T2N 1N4, Can.; e-mail gholdswo@acs. ucalgary.ca), K. Higuchi et al.,J. Geophys. Res., 101(D18), 23,317-23,334, Oct. 27, 1996.

Ice core data from Yukon and Greenland from about 1750 to 1950 show a clear atmospheric signal of an episode of biomass burning between about 1850 and 1910, which has been referred to elsewhere as the Pioneer Agriculture Revolution. The relationships of this finding to other types of climatic data are explored. It appears that factors associated with the burning, such as changes in surface albedo and atmospheric dust and smoke, caused local cooling and temporarily negated any radiative gas greenhouse warming.

Item #d97nov24

"Atmospheric Gas Concentrations over the Past Century Measured in Air from Firn at the South Pole," M. Battle (Grad. Sch. Oceanog., Univ. Rhode Island, Naragansett RI 02882), M. Bender et al.,Nature, 383(6597), 231-235, Sep. 19, 1996.

In contrast to the past few years, calculations based on the data indicate that, the terrestrial biosphere was neither a source nor sink of CO₂ between about 1977 and 1985. This implies that carbon losses from deforestation were approximately balanced by net CO₂ uptake elsewhere.

Item #d97nov25

"Late Pleistocene Charcoal in Tropical Atlantic Deep-Sea Sediments: Climatic and Geochemical Significance," D.J. Verardo (Dept. Environ. Sci., Univ. Virginia, Charlottesville VA 22903), W.F. Ruddiman,Geology, 24(9), 855-857, Sep. 1996.

Charcoal, presumably from forests, is a surprisingly significant component of the sampled sediment, and is linked to the growth and decay of high-latitude ice sheets. [The discovery may force scientists to revise models used to predict how the planet wi ll respond to climate change; see New Scientist, p. 15, Sep. 14, 1996.]

Item #d97nov26

Special issue. Tellus, 48B(4), ca. 180 pp., Sep. 1996. Contains 12 papers from the CO₂ symposium, The Breathing of the Earth-Observational Constraints for Models of the Terrestrial Biosphere (Boulder, Colorado, July 1995). Topics include observational networks, modeling, and observational analysis.

Item #d97nov27

"A Carbon Budget for Brazil: Influence of Future Land-Use Change," P. Schroeder (ManTech Environ. Res. Corp., US EPA, 200 SW 35th St., Corvallis OR 97333),Clim. Change, 33(3), 369-383, July 1996.

Develops an estimate of Brazil's biotic CO₂-C budget for the period 1990-2010, using a spreadsheet accounting model based on three major components: a conceptual model of ecosystem C cycling; a recently completed satellite-based vegetation classification; and published estimates of C density for each of the vegetation classes. Three alternative projections of land-use change through 2010 show Brazil to be a C source in the range of 3-5 ´ 10-9 MgC.