February 28, 2007
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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
"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
"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.
"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.
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.
"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
"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.
"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.
"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.
"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.
"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.
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
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