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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 9, NUMBER 5, MAY 1996

PROFESSIONAL PUBLICATIONS...

Item #d96may32

"Validating Models of Ecosystem Response to Global Change: How Can We Best Assess Models of Long-Term Global Change?" E.B. Rastetter (Ecosystem Ctr., Marine Biol. Lab., Woods Hole MA 02543), BioScience, 46(3), 190-197, Mar. 1996.

Examines four approaches to evaluating models of ecosystem response to changes in climate and CO₂ concentrations, finding all of them lacking. Because such models cannot be rigorously tested at present, the focus of both experiments and monitoring should be ecosystems that are expected to respond rapidly.

Item #d96may33

"Estimation of the Seasonal Cycle of Greenhouse Gas Fluxes from the Terrestrial Biosphere: Status and Challenges for More Mechanistic Understanding," C.S. Potter (Johnson Controls, NASA-Ames, MS 242-4, Moffett Field CA 94035), World Resour. Rev., 8(1), 36-60, Mar. 96.

Describes a new process-based model of terrestrial ecosystem biochemistry, CASA (Carnegie-Ames-Stanford Approach), that has high spatial (1° 1° ) and temporal (monthly) resolved inputs from satellite and other land surface data sets. Presents model estimates of major terrestrial greenhouse gas fluxes. The following needs for our ability to refine biosphere source/sink estimates remain: increased resolution and reliability of data on various types of land surface characteristics; and scaling up of sub-grid scale processes, with effective coupling of the atmosphere, biosphere and hydrosphere.

Item #d96may34

"Comparison of Radiative and Physiological Effects of Doubled Atmospheric CO₂ on Climate," P.J. Sellers, (Biospheric Sci., MC 923, NASA-Goddard, Greenbelt MD 20771), L. Bounoua et al., Science, 271(5254), 1402-1406, Mar. 8, 1996.

A coupled biosphere-atmosphere model indicates that under doubled CO₂, evapotranspiration will drop and air temperature will increase over the tropical continents, amplifying the changes resulting from atmospheric radiative effects.

Item #d96may35

Two items from J. Clim., 9(2), Feb. 1996:

"Low-Frequency Variability of Surface Air Temperature in a 1000-Year Integration of a Coupled Atmosphere-Ocean-Land Surface Model," S. Manabe (GFDL/NOAA, POB 308, Princeton NJ 08542), R.J. Stouffer, 376-393. Explores the low frequency fluctuations inherent in the coupled model and compares them with integrations of simplified models. The former can simulate the power spectrum of observed, global mean surface air temperature at decadal to interdecadal time scales, but does not generate a sustained, long-term warming trend of a magnitude observed since the end of the last century.

"Low-Frequency Variability in the Arctic Atmosphere Sea Ice, and Upper-Ocean Climate System," C.M. Bitz (Dept. Atmos. Sci., Box 351640, Univ. Washington, Seattle WA 98195), D.S. Battisti et al., 394-408. Uses a single-column, energy balance model of the atmosphere to identify the minimum model requirements to simulate the natural variability in the arctic climate. Discusses the implications of low-frequency, natural variability in sea ice volume for detecting a climate change.

Item #d96may36

"The Effect on Regional and Global Climate of Expansion of the World's Deserts," P.A. Dirmeyer (Ctr. for Ocean-Land-Atmos. Studies, 4041 Powder Mill Rd. (#302), Calverton MD 20705), J. Shukla, Quart. J. Royal Meteor. Soc., 122(530), 451-482, Jan. 1996 (Part B).

Investigates the effect of doubling the extent of the world's deserts, using 10-year integrations of an atmospheric GCM with realistic land-surface properties. Remote effects on the winter circulation include a pronounced trough over northern Europe. The climatic response in deforested areas varies among regions; the magnitude and seasonality of the changes, particularly in precipitation, seem to be functions of the monsoon regime. Northern Africa suffers a strong year-round drought, suggesting this area is most sensitive to desertification.

Item #d96may37

"Evaluating Climate Model Simulations of Precipitation: Methods, Problems and Performance," M. Airey (Clim. Res. Unit, Univ. E. Anglia, Norwich NR4 7TJ, UK), M. Hulme, Prog. Phys. Geog., 19(4), 427-448, Dec. 1995.

Reviews the methodology of model evaluation with examples from recent studies involving precipitation, a crucial climatic element which is difficult to model because of the wide range of spatial scales involved. No single, currently available global dataset of precipitation fulfills all the requirements of model evaluation. A number of recent precipitation evaluation projects are reviewed and a hierarchy of evaluation methods is provided based on spatial and temporal scale and whether tests for statistical significance are applied. The results of evaluation studies to date emphasize that model simulations of future changes to the magnitude, timing and spatial pattern of global precipitation must be viewed only as scenarios, and not as predictions.

Item #d96may38

"Vegetation/Ecosystem Modeling and Analysis Project: Comparing Biogeography and Biogeochemistry Models in a Continental-Scale Study of Terrestrial Ecosystem Responses to Climate Change and CO₂ Doubling," VEMAP Members (attn: J.M. Melillo, Ecosystem Ctr., Marine Biol. Lab., Woods Hole MA 02543), Global Biogeochem. Cycles, 9(4), 407-437, Dec. 1995.

Presents an overview of results of an international exercise involving investigators from 13 institutions, which compared simulations of three models of ecosystem structure (biogeography) and three models of ecosystem function (biogeochemistry). Our current understanding of the controls of ecosystem structure and function is currently insufficient to allow the identification of the "best" models, or accept as correct their predictions. Ultimately, the two types of model should be formally linked so that biogeography and biogeochemistry are truly interactive.

Item #d96may39

"Regional Statistical-Dynamical Climate Modelling: Tests," J. Egger (Meteor. Inst., Univ. München, Theresienstr. 37, 80333 München, Ger.), Beitr. Phys. Atmos. [Contributions to Atmos. Phys.], 68(4), 281-289, Nov. 1995.

The statistical-dynamical approach to regional climate modeling appears to be a cost effective alternative to the nesting technique. The power of the approach is tested by applying it to the climate of a highly simplified regional cliamte model where modified Eady waves propagate over a shallow mountain. The statistical-dynamical approach captures the basic features of this climate, but deviations from the test fields are considerable for both the climatic means and for the variances.

Item #d96may40

"Towards the Detection and Attribution of an Anthropogenic Effect on Climate," B.D. Santer (Clim. Model Diagnosis Prog., Lawrence-Livermore Natl. Lab., POB 808, Livermore CA 94550), K.E. Taylor et al., Clim. Dynamics, 12(2), 77-100, Dec. 1995.

Describes a further contribution toward distinguishing the climatic effects of sulfate particles from those of greenhouse gases. Recent progress on this topic was first announced at the Berlin climate treaty meeting last spring, and was a major factor in the latest IPCC assessment of the science of climate change. [See Global Climate Change Digest, Sep. 1995 for related paper by Mitchell et al. (Prof. Pubs./of General Interest/Clouds and aerosols), and related news note]. Results of model experiments in which sulfate and CO₂ were varied individually and in combination were analyzed using pattern similarity statistics, and compared with observed changes in patterns of surface temperature change. Provides the first evidence that both large scale (global mean) and smaller scale components of a combined CO₂/anthropogenic sulfate aerosol signal are identifiable in the temperature record.

Item #d96may41

"Sensitivity of Direct Global Warming Potentials to Key Uncertainties," D.J. Wuebbles (Dept. Atmos. Sci., Univ. Illinois, Urbana IL 61801), A.K. Jain et al., Clim. Change, 29(3), 265-297, Mar. 1995.

Examines several uncertainties in determining the potential effects on climate of greenhouse gases compared to that of CO₂ (GWPs), which are quite sensitive to the assumed background level of CO₂. Attempts to improve on the IPCC estimates of 1990 by using a balanced carbon cycle model, which produces up to 21% enhancement of the GWPs for most trace gases for time horizons up to 100 years, but a decreasing enhancement with longer time horizons. Uncertainty regarding the CO₂ fertilization effect contributes a 20% range in GWP values. Assumption that atmospheric levels of traces gases change with time gives GWPs that are 19 to 32% greater than if constant levels are assumed.