February 28, 2007
GCRIO Program Overview
Our extensive collection of documents.
Archives of the
Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 8, NUMBER 12, DECEMBER 1995
How Reliable Are Their Predictions?", E.J. Barron (Earth Systems Sci. Ctr.,
Deike Bldg., Pennsylvania State Univ., Univ. Pk. PA 16802), Consequences,
1(3), 16-27, Autumn 1995.
Computer-based general circulation models are modified versions of the
mathematical simulations that have been used for decades to forecast weather.
Many now in use around the world have been independently derived and are
continually compared and evaluated for their ability to reproduce documented
climate features of the past. However, because they are based on our present,
evolving knowledge of how the climate system operates and have coarse spatial
resolution, their projections of future climate are cast in terms of a range of
uncertainty. Nevertheless, they are our best and only hope of anticipating
future changes in climate, and we only lose if we dismiss their findings,
outright, as too equivocal or theoretical or incomplete. Choices of whether or
how to act on what is predicted are best made with a knowledge of both the
strengths of these tools and their weaknesses. We can count on continued
improvements in model reliability.
"Mapping the Land
Surface for Global Atmosphere-Biosphere Models: Toward Continuous Distributions
of Vegetation's Functional Properties," R.S. DeFries (Dept. Geog., Univ.
Maryland, College Pk. MD 20742), C.B. Field et al., J. Geophys. Res.,
100(D10), 20,867-20,882, Oct. 20, 1995.
Reviews several existing land surface classification schemes commonly used
as important boundary conditions in atmosphere-biosphere models. Considers the
functional properties of vegetation required to calculate parameter fields used
in global models, and suggests an approach for describing the land surface using
continuous distributions of these functional properties.
Budget of O3 in the Troposphere Calculated with a Chemistry General Circulation
Model," G.-J. Roelofs (POB 8129, 6700 EV, Wageningen, Neth.), J. Lelieveld,
Presents results of global tropospheric chemistry simulations with the
coupled chemistry-atmospheric general circulation model ECHAM, which will
eventually be used to study climate changes through anthropogenic influences on
the chemistry of the atmosphere. Comparisons of calculated O3 surface
concentrations and O3 profiles with data show that the model reproduces O3
distributions in remote tropical and midlatitude sites, but underestimates
concentrations at the poles and in relatively polluted areas. Discusses the
model deficiencies that are responsible and how they will be improved.
Temperature, Greenhouse Gases, and Aerosols: Models and Observations,"
J.F.B. Mitchell (Hadley Ctr., Meteor. Off., London Rd., Bracknell, Berkshire
RG12 2SY, UK), R.A. Davis et al., J. Clim., 8(10), 2364-2386,
Presents further results from the U.K. Meteorological Office GCM
incorporating the effects of sulfate (industrial) aerosol, which has already
been shown to improve model simulations of the observed temperature record. The
addition of aerosols has little impact on the reduction of diurnal range of
surface temperature that accompanies increased CO2. (This is a
sequel to the author's paper in the Aug. 10, 1995 issue of Nature,
listed in Prof. Pubs./Of Gen. Interest/CLouds and Aerosols, GLOBAL CLIMATE
CHANGE DIGEST, Sep. 1995.)
Process Models Discussed in Interdisciplinary Forum," A. Henderson-Sellers
(Clim. Impacts Ctr., Macquarie Univ., North Ryde, Sydney, SW 2109, Australia),
Eos, 76(38), 369, 379, Sep. 19, 1995.
Summarizes a joint symposium on the status of land surface process models
held during the IUGG 21st Assembly (Boulder, Colorado, July 1995).
Processes and Climate Modeling," R.E. Dickinson (Inst. Atmos. Phys., Univ.
Arizona, Tucson AZ 85721), Bull. Amer. Meteor. Soc., 76(8),
1445-1448, Aug. 1995.
An overview of the current status of the representation of land surface
processes in climate models, originally presented as the 1995 AMS Walter Orr
Roberts Lecture. With the increasing complexity and importance of these
parameterizations and their detailed treatments of the roles of soils and
vegetation, have come greater demands for observational programs to evaluate
their success and to provide required parameters. Further improvement is most
needed in model treatments of precipitation, cloud effects on surface radiation,
and boundary layer processes.
"A Transient CO2
Experiment with the MRI CGCMQuick Report," T. Tokioka (Japan Meteor.
Agency, Tokyo 100, Japan), A. Noda et al., J. Meteor. Soc. Japan, 73(4),
817-826, Aug. 1995.
Demonstrates application of the Meteorological Research Institute (MRI)
coupled atmosphere-ocean GCM, which has an elaborate model of the seasonal
variation of sea ice coverage and thickness, and a high resolution ocean
component in the low latitudes for simulating El Niño behavior. In a
70-year time integration, atmospheric response to CO2 increase is
slower for the Southern Hemisphere and ocean areas, but the surface temperature
increase in the Northern Hemisphere does not dominate for the first 50 years.
Leads in sea ice act as a strong negative feedback on changes in sea ice volume,
influencing the timing of the warming.
Winter Climate Trends, Ozone Changes and Increased Greenhouse Gas Forcing,"
H.-F. Graf (M. Planck Inst. Meteor., Bundesstr. 55, 20146 Hamburg, Ger.), J.
Perlwitz et al., Beitr. Phys. Atmos., 68(3), 233-248, Aug. 1995.
Ozone data of the past 15-20 years show an increase in upper tropospheric O3
and a decrease in lower stratospheric O3. These changes are discussed against
the background of meteorological data and GCM simulations of the effects of
increased greenhouse gas concentration, aerosols, and the modified ozone profile
itself. Concludes that a comprehensive climate model, including atmospheric
chemistry and a good representation of the stratosphere, is needed to study
future climate scenarios, and that greenhouse gas effects and ozone
concentration are probably not independent.
of Climate Sensitivity on the Horizontal Resolution of a GCM," C.A. Senior
(Hadley Ctr., Meteor. Off., London Rd., Bracknell, Berkshire RG12 2SY, UK), J.
Clim., 8(11), 2860-2880, Nov. 1995.
The use of higher resolution in the Hadley Center model generally produces
favorable changes in present-day and doubled CO2 simulations. The
global mean annual-mean warming due to increased CO2 is very
similar, but there are differences in the latitudinal distribution of the
zonally averaged temperature response, which in winter is related to the
response of Northern Hemisphere storm tracks.
Sulfate-CCN-Cloud Albedo Effect: A Sensitivity Study with Two General
Circulation Models," O. Boucher (Lab. Météor. Dynamique,
CNRS, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris cedex 05,
France), U. Lohmann, Tellus, 47B(3), 281-300, July 1995.
Anthropogenic sulfate particles have an indirect cooling effect because they
induce the formation cloud droplets, which reflect sunlight. This study
estimates the magnitude of the effect by empirically relating the cloud droplet
number concentration to the sulfate aerosol mass concentration derived from a
chemical transport model. Experiments using this information in two GCMs
indicate a globally-averaged indirect forcing of about -1 W m-2. The value in
different experiments ranged from -0.5 to -1.5 W m-2, but the range of
uncertainty is certainly greater. The highest forcings occur in and off the
coasts of the polluted regions of the Northern Hemisphere.
"Analysis of Snow
Feedbacks in 14 General Circulation Models," D.A. Randall (Dept. Atmos.
Sci., Colorado State Univ., Fort Collins CO 80523), R.D. Cess et al., J.
Geophys. Res., 99(D10), 20,757-20,771, Oct. 20, 1994.
Results of 14 GCMs were compared through idealized numerical experiments in
which the surface energy budgets of the models were analyzed. The feedbacks were
negative or weakly positive in some of the models, but strongly positive in
others, and in each case were determined by a complex mix of factors.
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Index of Abbreviations