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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 11, NUMBER 7, JULY 1998

PROFESSIONAL PUBLICATIONS...
CARBON CYCLE

Item #d98jul22

"In Balance, with a Little Help from the Plants," P.P. Tans (CMDL, NOAA, 325 S. Broadway, Boulder CO 80303; e-mail: ptans@cmdl.noaa.gov), J.W.C. White,Science, 281(5374), 183-184, July 10, 1998.

A research perspective, summarizing the state of knowledge of the global carbon cycle and key outstanding questions. A crucial test of hypotheses and process models of the carbon cycle is the prediction of regional fluxes.

Item #d98jul23

"Testing Global Ocean Carbon Cycle Models Using Measurements of Atmospheric O₂ and CO₂ Concentration," B.B. Stephens (Scripps Inst. Oceanog., La Jolla CA 92093; e-mail: britt@ucsd.edu), R.F. Keeling et al., Global Biogeochem. Cycles, 12(2), 213-230, June 1998.

Defines a new quantity, atmospheric potential oxygen (O₂ + CO₂), which is conservative with respect to terrestrial photosynthesis and respiration. Uses this to evaluate simulations of the global carbon cycle based on various global climate models.

Item #d98jul24

"The Terrestrial Carbon Cycle: Implications for the Kyoto Protocol," IGBP Terrestrial Carbon Working Group (Roy. Swed. Acad. Sci., Box 50005, S-10405, Stockholm, Swed.; Attn.: W. Steffen; e-mail: will@igbp.kva.se),Science, 280(5368), 1393-1394, May 29, 1998.

Annex 1 countries of the Kyoto Protocol can meet their commitments in part by increasing net carbon sequestration in terrestrial carbon sinks. This article discusses a number of problems relating to the carbon budget that will seriously limit the Protocol's effectiveness if not corrected. Terrestrial carbon sinks can offset fossil fuel emissions only temporarily (decades to a century), and are best viewed as buying valuable time to address the most significant anthropogenic perturbation of the carbon cycle—fossil fuel emissions.

Item #d98jul25

Three related items in Nature, 393(6682), May 21, 1998:

"The Carbon Equation," D.S. Schimel (NCAR, POB 3000, Boulder CO 80307; e-mail: schimel@cgd.ucar.edu), 208-209. Compares and contrasts the following two studies, which taken together, bring a renewed sense of urgency to research on the future behavior of the Earth system, especially the coupling of anthropogenic greenhouse gases to the climate and carbon systems.

"Dynamic Responses of Terrestrial Ecosystem Carbon Cycling to Global Climate Change," M. Cao (Dept. Environ. Sci., Univ. Virginia, Charlottesville VA 22903), F.I. Woodward, 249-252. Uses a terrestrial biogeochemical model, forced by simulations of transient climate change with a GCM, to quantify the dynamic variations in ecosystem carbon fluxes caused by fluctuations in CO₂ and climate from 1861 to 2070. Predicts that the global net ecosystem production will increase significantly, but this response will decline as the CO₂ fertilization effect becomes saturated and is diminished by climatic factors.

Item #d98jul26

"Evaluation of Terrestrial Carbon Cycle Models Through Simulations of the Seasonal Cycle of Atmospheric CO₂: First Results of a Model Intercomparison Study," M. Heimann (Max Planck Inst. Meteor., Bundesstr. 55, D-20146 Hamburg, Ger.; e-mail: martin.heimann@dkrz.de), G. Esser et al., Global Biogeochem. Cycles, 12(1), 1-24, Mar. 1998.

Reports an extensive international comparison of models (one diagnostic and five prognostic) that were run with the same long-term climate forcing, and compared to observations collected at 27 NOAA monitoring stations. Model performance generally differs between the tropics and the higher latitudes.

Item #d98jul27

"Missing Sinks, Feedbacks and Understanding the Role of Terrestrial Ecosystems in the Global Carbon Balance," R.A. Houghton (Woods Hole Res. Ctr., POB 296, Woods Hole MA 02543; e-mail: rhoughton@whrc.org), E.A. Davidson, G.M. Woodwell,Global Biogeochem. Cycles, 12(1), 25-34, Mar. 1998.

Data pertaining to temporal variability in the global carbon balance are conflicting with respect to the question of whether increasing temperatures cause a release or storage of terrestrial carbon; the answer seems to depend in part on time scale. However, a positive feedback between temperature and the release of CO₂ by terrestrial respiration seems likely to grow in importance, and could change significantly the role that terrestrial ecosystems play in the global carbon balance.

Item #d98jul28

"Carbon Cycling in Cultivated Land and Its Global Significance," G.A. Buyanovsky (Soil & Atmos. Sci. Dept., 144 Mumford Hall, Univ. Missouri, Columbia MO 65211), G.H. Wagner,Global Change Biology, 4(2), 131-141, Feb. 1998.

Long-term data from one of the oldest experimental fields in the U.S. were used to determine the direction of soil organic carbon dynamics in cultivated land. Results show that cultivated soils under proper management exercise a positive influence in the current imbalance in the global carbon budget.

Item #d98jul29

"The Global Carbon Sink: A Grassland Perspective," J.M.O. Scurlock (Environ. Sci. Div., Oak Ridge Natl. Lab., POB 2008, Oak Ridge TN 37831; e-mail: npq@ornl.gov), D.O. Hall,Global Change Biology, 4(2), 229-233, Feb. 1998.

The challenge to identify the biospheric sinks for about half the total fossil fuel carbon emissions must consider below-ground processes as well as those more easily measured above ground. The rapid increase in the availability of productivity data facilitated by the Internet will be important for future scaling-up of global change responses.

Item #d98jul30

"Estimating the Terrestrial Carbon Pools of the Former Soviet Union, Conterminous U.S., and Brazil," D.P. Turner (Dept. Forest Sci., Oregon State Univ., Corvallis OR 97331; e-mail: turnerd@fsl.orst.edu), J.K. Winjum et al.,Clim. Res., 9(3), 183-196, Feb. 27, 1998.

Estimates and contrasts the carbon pools in the three areas using various sources of data. The two largest pools isolated are potentially long-term sources of carbon to the atmosphere: peatland of the former Soviet Union, which could release carbon under climate change; and phytomass in the tropical-moist forests of Brazil, which may be lost via deforestation.

Item #d98jul31

"Reduced Sensitivity of Recent Tree-Growth to Temperature at High Northern Latitudes," K.R. Briffa (Clim. Res. Unit, Univ. E. Anglia, Norwich NR4 7TJ, UK; e-mail: k.briffa@uea.ac.uk), F.H. Schweingruber et al.,Nature, 391(6668), 678-682, Feb. 12, 1998.

Results indicate that estimates of future atmospheric CO₂ concentrations, based on carbon-cycle models that are uniformly sensitive to high-latitude warming, could be too low.

Item #d98jul32

"Phytoplankton Change in the North Atlantic," P.C. Reid (Sir Alister Hardy Foundation for Ocean Sci., The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK; e-mail: pcre@wpo.nerc.ac.uk), M. Edwards et al.,Nature, 391(6667), 546, Feb. 5, 1998.

Observations have implications for CO₂ fluxes and the productivity of the North Atlantic, and suggest the possible importance of shelf phytoplankton growth to the global carbon budget.

Item #d98jul33

"Net Primary and Ecosystem Production and Carbon Stocks of Terrestrial Ecosystems and Their Responses to Climate Change," M. Cao (Dept. Animal & Plant Sci., Univ. Sheffield, Sheffield S10 2TN, UK; e-mail: m.cao@sheffield.ac.uk), F.I. Woodward,Global Change Biology, 4(2), 185-198, Feb. 1998.

Describes a model for investigating terrestrial carbon exchange and its response to climatic variation, based on the processes of photosynthesis, carbon allocation, litter production and soil organic carbon decomposition. Predicts a strong enhancement in net primary production and carbon stocks of terrestrial ecosystems.

Item #d98jul34

"Sensitivity of Boreal Forest Carbon Balance to Soil Thaw," M.L. Goulden (Dept. Earth. Sys. Sci., Univ. California, Irvine CA 92697; e-mail: mgoulden@uci.edu), S.C. Wofsy et al.,Science, 279(5348), 214-217, Jan. 9, 1998.

Field and laboratory measurements show that decomposition of organic matter in the soil increased 10-fold upon thawing. The stability of the soil carbon pool appears sensitive to the depth and duration of thaw, and climatic changes that promote thaw are likely to cause a net efflux of CO₂ from the site.

Item #d98jul35

"The Effects of Water Table Manipulation and Elevated Temperature on the Net CO₂ Flux of Wet Sedge Tundra Ecosystems," W.C. Oechel (Global Change Res. Group, Dept. Biol., San Diego State Univ., San Diego CA 92182; e-mail: oechel@sunstroke.sdsu.edu), G.L. Vourlitis et al., Global Change Biology, 4(1), 77-90, Jan. 1998.

Field experiments suggest that many currently saturated or nearly saturated wet sedge ecosystems of the North slope of Alaska may become significant sources of CO₂ if climate change predictions are realized. There is ample evidence that this may already be occurring in arctic Alaska.

Item #d98jul36

"Carbon Budget Implications of the Transition from Natural to Managed Disturbance Regimes in Forest Landscapes," W.A. Kurz (ESSA Technol. Ltd., 1765 W. 8th Ave., Vancouver BC V6J 5C6, Can.; e-mail: wkurz@essa.com), S.J. Beukema, M.J. Apps,Mitigation & Adaptation Strategies for Global Change, 2(4), 405-421, 1997-1998.

Applies the Carbon Budget Model of the Canadian Forest Sector to six representative landscapes undergoing transition from natural conditions to harvesting. After 200 years of forest management, the carbon stored in the landscape plus that retained in manufactured forest products was between 58% and 101% of the landscape carbon prior to the onset of harvesting.

Item #d98jul37

"Terrestrial Carbon Dynamics: Case studies in the Former Soviet Union, the Conterminous United States, Mexico and Brazil," M.A. Cairns (U.S. EPA, 200 SW 35th St., Corvallis OR 97333; e-mail: michael@heart.cor.epa.gov), J.K. Winjum et al.,ibid., 1(4), 363-383, 1997.

Assesses land-use impacts on carbon flux at a national level. Total flux from land use was negative (corresponding to emissions) in all four countries. The total net effect of biotic and land-use factors was a carbon sink in the FSU and the U.S., and a source in both Mexico and Brazil.

Item #d98jul38

"The Response of Global Terrestrial Ecosystems to Interannual Temperature Variability," B.H. Braswell (Inst. Study Earth, Oceans & Space, Univ. New Hampshire, Durham NH 03824; e-mail: rob.braswell@unh.edu), D.S. Schimel et al.,Science, 278(5339), 870-872, Oct. 31, 1997.

Measurements of CO₂ and satellite-derived measurements of temperature and vegetation index were used to investigate relationships among climate, CO₂, and ecosystems. Results imply that changes in global ecosystem distributions could indirectly alter the relationships between climate and carbon storage.

Item #d98jul39

"Simulating Effects of Fire on Gaseous Emissions and Atmospheric Carbon Fluxes from Coniferous Forest Landscapes," R.E. Keane (Intermountain Res. Sta., Fire Sci. Lab., USDA Forest Service, POB 8089, Missoula MT 59807), C.C. Hardy et al.,World Resource Review, 9(2), 177-205, June 1997.

Uses a mechanistic forest succession model to examine long-term trends in emissions of particles, methane, CO, and CO₂ under current, historical and future fire regimes in Glacier National Park. The model indicates that temperate and sub-boreal coniferous forest landscapes with fire tend to respire less carbon, even when carbon emissions from fire are included. Discusses potential implications for wildland fire management and the global carbon cycle.

Item #d98jul40

"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 #d98jul41

"Boreal Forest Carbon Stocks and Wood Supply: Past, Present and Future Responses to Changing Climate, Agriculture and Species Availability," A.M. Solomon (U.S. EPA, 200 SW 35th St., Corvallis OR 97333), R. Leemans,Agric. & Forest Meteor., 84(1-2), 137-151, Mar. 1997.

Calculations were based on a standard static vegetation model driven by the most recent climate change scenarios from three coupled ocean-atmosphere models. The lag in immigration of tree species suitable for a warmed climate temporarily reduced future wood supplies 4-6%; inclusion of present and future agricultural land uses permitted by a warming climate reduced carbon stocks and wood supplies 10-20%.

Item #d98jul42

"Forest Plantations of the World: Their Extent, Ecological Attributes, and Carbon Storage," J.K. Winjum (U.S. EPA, 200 SW 35th St., Corvallis OR 97333), P.E. Schroeder,ibid., 153-167.

New plantations are established each year by 124 countries throughout the high, middle, and low latitudes of the world. This study integrates information across latitudes to estimate world carbon storage in plantations to be 11.8 Pg C, with an annual increase of 0.178 Pg C per year.

Item #d98jul43

"State and Change in Carbon Pools in the Forests of Tropical Africa," G. Gaston, S. Brown (U.S. EPA, 200 SW 35th St., Corvallis OR 97333; e-mail: british@heart.cor.epa.gov) et al.,Global Change Biol., 4(1), 97-114, Jan. 1998.

Combines spatially explicit estimates of biomass C density, obtained by modeling in a geographical information system, with new data on the area of forests reported for 1980 and 1990 by the FAO. Estimates the total change in above-ground forest C pool for the decade 1980-1990, due to changes in land cover use, to be a decrease of 6.6Pg C. Of this, 43% was due to deforestation and 57% due to biomass reduction by other human activities.

Item #d98jul44

"Principles for a Climate Regulation Mechanism during the Late Phenerozoic Era, Based on Carbon Fixation in Peat-Forming Wetlands," L.G. Franzén (Dept. Phys. Geog., Göteborg Univ., S-413 81 Gothenburg, Sweden; e-mail: LARS@gig.gu.se), D. Chen, L.F. Klinger,Ambio, 25(7), 435-442, Nov. 1996.

Models the climate regulating effect of peat bogs, which act as carbon sinks. With present levels of CO₂, the model shows that the initiation of a new ice age could already have been delayed roughly 700-1000 years. Scenarios with further increases in CO₂ show a much longer delay.

Item #d98jul45

"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.

Results show that, in contrast to the past few years, the terrestrial biosphere was neither a source nor a sink of CO₂ between about 1977 and 1985.