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, NUMBERS 10-11, OCTOBER-NOVEMBER 1996
GLOBAL & REGIONAL MODELING
of Hydrologic Processes in AMIP [Atmospheric Model Intercomparison Project] GCMs,"
K.-M. Lau (Atmos. Lab., Code 913, NASA-Goddard, Greenbelt MD 20771; e-mail:
email@example.com), J.H. Kim, Y. Sud, Bull. Amer. Meteor. Soc., 77(10),
2209-2227, Oct. 1996.
Compares the current abilities of 29 GCMs to simulate regional and hydrologic processes
in response to observations of sea surface temperature and sea ice boundary forcings. Most
major features are reasonably well simulated, such as the global rainfall distribution,
heavy precipitation associated with deep convection, and rainfall associated with the
Southern Oscillation. Common problems include significant errors in the total global water
balance (in about a quarter of the models), poor simulation of some features of the Asian
monsoon, and underestimation of light rainfall. Validation of simulated discharge from the
Amazon and Mississippi Rivers shows that it is premature to use GCMs for climate studies
related to continental-scale water balance.
"Effects of Cloud-Radiation Schemes on Climate Model Results," R.C.J. Somerville
(Scripps Inst. Oceanog., La Jolla CA 92093), S.F. Iacobellis, W.-H. Lee, World Resource
Review, 8(3), 321-333, Sep. 1996.
Feedbacks due to cloud-radiation interactions are thought to be the largest source of
uncertainty in climate simulations. For too long there were too many plausible
cloud-radiation parameterizations and too little effort to test them empirically. The
effects on climate sensitivity of several cloud-radiation parameterizations were
investigated with the NCAR Community Climate Model and validated with observations from
field experiments. Schemes with explicit cloud water budgets and interactive radiative
properties may be capable of matching observations closely. Now that appropriate
observations and novel modeling tools are at last becoming available, we may anticipate
rapid progress in this critical area.
"The ISLSCP [Intl. Land Surface Climatology Project] Initiative I Global Datasets:
Surface Boundary Conditions and Atmospheric Forcings for Land-Atmosphere Studies,"
P.J. Sellers, B.W. Meeson (Goddard Space Flight Ctr., NASA, Bldg. 28, Code 902.2,
Greenbelt MD 20771; e-mail: firstname.lastname@example.org) et al., Bull. Amer. Meteor. Soc.,
77(9), 1987-2005, Sep. 1996.
Describes a comprehensive series of global data sets for land-atmosphere models that
has been formatted to a common grid and released on a set of CD-ROMs. All data sets cover
1987-88, most at a monthly interval. The headings for the data sets are: vegetation;
hydrology and soils; snow, ice, and oceans; radiation and clouds; and near-surface
"Polar Boundary Layer Plumes and Bottom Water Formation: A Missing Element in Ocean
General Circulation Models," L.D.D. Harvey (Dept. Geog., Univ. Toronto, 100 St.
George St., Toronto ON M5S 3G3, Can.; e-mail: email@example.com), J. Geophys.
Res., 101(C9), 20,799-20,808, Sep. 15, 1996.
Much of world's the deep water forms as relatively dense layer on shelves in polar
regions, and flows downslope as a boundary layer plume. This process, omitted from current
ocean GCMs, was investigated by coupling a 2-D plume model to a 2-D dynamical ocean model,
and sea ice and surface climate models, and examining response to a greenhouse gas
increase. Results indicate that polar plume processes should be incorporated in coupled
atmosphere-ocean GCMs, but that correct simulation of the ocean density field and the
surface forcing conditions are higher priorities. Incorporation of plumes could especially
lead to more accurate representation of regional climatic responses.
"Global Comparison of the Regional Rainfall Results of Enhanced Greenhouse Coupled
and Mixed Layer Ocean Experiments: Implications for Climate Change Scenario
Development," P.H. Whetton (Div. Atmos. Res., CSIRO, P.B. 1, Aspendale 3195,
Victoria, Australia), M.H. England et al., Clim. Change, 33(4), 497-519,
Compares rainfall results from five models, which use a simple mixed layer ocean
formulation, with results from five models which use a fully dynamic ocean model. For many
regions in the Northern Hemisphere, there is strong agreement on the sign of the simulated
rainfall change, but in the Southern Hemisphere there are large and apparently systematic
differences. Concludes that it may be too soon to base some regionally specific climate
change scenarios solely on the results of fully dynamic models.
"Absorption of Solar Energy in the Atmosphere: Discrepancy Between Model and
Observations," A. Arking (Dept. Earth & Planetary Sci., Johns Hopkins Univ.,
Baltimore MD 21218; e-mail: firstname.lastname@example.org), Science, 273(5276),
779-782, Aug. 9, 1996.
Calculations made by an atmospheric general circulation model were compared with
observations of the flux of solar radiant energy based on a combination of ground-based
and satellite measurements. The model underestimated the amount of solar energy absorbed
by the Earth's atmosphere by 25 to 30 watts per square meter. Contrary to some recent
reports, clouds have little or no overall effect on atmospheric absorption; water vapor
seems to have the dominant influence.
"Implications of a New Eddy Parameterization for Ocean Models," T.J. McDougall
(Div. Oeanog., GPO Box 1538, Hobart 7001, Tasmania, Australia; e-mail:
email@example.com), A.C. Hirst et al., Geophys. Res. Lett., 23(16),
2085-2088, Aug. 1, 1996.
Demonstrates a new parameterization that yields deep ocean salinities and temperatures
closer to those observed. In addition, the depth to which surface-induced tracers
penetrate in the Southern Ocean is realistic. This depth is overestimated by previous
ocean models, including those that estimate global warming. The new parameterization is
expected to yield greater global warming.
"A Case Study of the Adequacy of GCM Simulations for Input to Regional Climate Change
Assessments," J.S. Risbey (129 Baker Hall, Carnegie Mellon Univ., Pittsburgh PA
15213; e-mail: firstname.lastname@example.org), P.H. Stone, J. Clim., 9(7),
1441-1467, July 1996.
The Sacramento Basin is the focus of a case study to test whether a variety of GCMs
from GISS and NCAR are capable of simulating the large-scale and synoptic-scale processes
important in studies of regional water resources. In all the models, the stationary waves,
jet streams, and storm tracks in the North Pacific-North America region show major
differences from observations. The larger-scale fields necessary for driving nested models
and impact models for the basin, or for western North America in general, are deficient,
probably because of inadequate parameterization of sub-grid scale processes.
Two related items in Nature, 382(6586), July 4, 1996:
"An Incriminating Fingerprint," N. Nicholls (Meteor. Bureau Res. Ctr., POB
1289K, Melbourne, Vic. 3001, Australia), 27-28. Gives a scientific perspective on the
following article, which, despite several caveats, provides the most convincing
demonstration yet that human actions may have contributed to global air temperature
changes in this century.
"A Search for Human Influences on the Thermal Structure of the Atmosphere,"
B.D. Santer (Clim. Model Diagnosis, Lawrence-Livermore Natl. Lab., POB 808, Livermore CA
94550), K.E. Taylor et al., 39-46. Uses climate model simulations to examine changes in
the vertical structure of atmospheric temperature as a "fingerprint" of human
influence on climate. The study differs from similar ones in four respects: (1) it
includes the combined influence of CO2 and anthropogenic sulfate aerosols on
the vertical pattern; (2) two different models are used, to examine model-dependent
uncertainties; (3) the possible effects of changes in stratospheric ozone are examined;
(4) control runs with coupled ocean-atmosphere models are used to estimate internally
generated natural climate variability. Simulations of the spatial patterns of temperature
change in the free atmosphere from 1963 to 1987 are similar to those observed, and the
degree of similarity increases through the period. The observed trend is probably partly
due to human activities, although many uncertainties remain, particularly relating to
estimates of natural variability. The investigation shows a clear need for modeling
experiments that combine simultaneous changes in CO2, O3 and anthropogenic
"Evaluation of Simulations of Terrestrial Precipitation in UK Met. Office/Hadley
Center Climate Change Experiments," M.H. Airey (Clim. Res. Unit., Univ. E. Anglia,
Norwich NR4 7TJ, UK), M. Hulm, T.C. Johns, Geophys. Res. Lett., 23(13),
1657-1660, June 15, 1996.
Evaluates four successive versions of the Hadley GCM by comparing precipitation fields
over land from the control integrations with observed precipitation. Globally,
improvements in simulating mean monthly precipitation patterns occur with successive
versions. The later versions show improvement in the South Asian summer monsoon, the
pattern of temporal variability, and the pattern of temporal correlation between the
Southern Oscillation Index and precipitation anomalies.
"Documentation of the AMIP [Atmospheric Model Intercomparison Project] Models on the
World Wide Web," T.J. Phillips (Clim. Model Diagnosis & Intercomparison, L-264,
Lawrence-Livermore Natl. Lab., POB 808, Livermore CA 94551; e-mail:
email@example.com), Bull. Amer. Meteor. Soc., 77(6), 1191-1196, June
Launched in 1991, AMIP led to a 1994 report documenting the summaries, dynamics, and
physics of 30 participating models in a common and reasonably comprehensive framework.
Now, constant updates of that information are available on the World Wide Web at http://www-pcmdi.llnl.gov/phillips/modldoc/amip/amip.html,
with hypertext links to more detailed information.
Two items in J. Geophys. Res., 101(D8), May 27, 1996:
"Cloud Feedback in Atmospheric General Circulation Models: An Update," R.D.
Cess (Inst. Terrestrial & Planetary Atmos., Marine Sci. Ctr., SUNY, Stony Brook NY
11794), M.H. Zhang et al., 12,791-12,794. A comparison of the climate sensitivity of 19
GCMs six years ago found a roughly threefold variation among the models, mostly attributed
to differences in depictions of cloud feedback. In an update of this comparison, current
models showed considerably smaller differences in net cloud feedback. However,
there are still substantial differences in the feedback components, showing that physical
"High Latitude Climate Change in a Global Coupled Ocean-Atmosphere-Sea Ice Model
with Increased Atmospheric CO2," W.M. Washington (NCAR, POB 3000, Boulder
CO 80307), G.A. Meehl, 12,795-12,801. Describes an increasing CO2 simulation
using improved versions of models from previous experiments, including a 1° by 1° ,
20-level ocean GCM. The models produce an anomalous warm layer of water at depths between
200 and 400 meters, which resembles an anomalous warm layer recently observed in the
Arctic. The ice albedo feedback is strong, leading to comparatively high climate
"A 3D Model Study of the Global Sulphur Cycle: Contributions of Anthropogenic and
Biogenic Sources," M. Pham (Service d'Aéronomie, 4 Pl. Jussieu, 75 252 Paris Cedex
05, France), J.F. Müller et al., Atmos. Environ., 30(10/11), 1815-1822, May
Compares simulations of the preindustrial and present-day atmospheres produced by the
IMAGES 3-D tropospheric chemistry-transport model. They show a large postindustrial
increase in the concentrations of SO2 and non-sea-salt sulfates, amounting to a factor of
2 or 3 on a global average, and reaching two orders of magnitude at the surface in some
parts of the Northern Hemisphere. Biogenic species such as DMS are also shown to be
influenced by industrialization through changes in the oxidizing capacity of the
"Parameterizations of Marine Stratus Microphysics Based on In Situ Observations:
Implications for GCMs," I. Gultepe (Cloud Phys. Res. Div., Atmos. Environ. Serv.,
4905 Dufferin St., Downsview ON M3H 5T4, Can.), G.A. Isaac et al., J. Clim., 9(2),
345-357, Feb. 1996.
Airborne observations conducted in marine stratus over the east coast of Canada are
used to develop cloud microphysical parameterizations schemes for general circulation
models. Results show that multiple relationships are present among various microphysical
properties, depending in part on variations in both aerosol concentrations and cloud
dynamic activity. Parameterized equations must be used in GCMs with caution.
"Temperature Depression in the Lowland Tropics in Glacial Times," P.A. Colinvaux
(Smithsonian Tropical Res. Inst., POB 2072, Balboa, Panama), K.-B. Liu et al., Clim.
Change, 32(1), 19-33, Jan. 1996.
Presents pollen and other data confirming the recently recognized existence of a
general tropical cooling during the last ice age. Climate models used to predict future
effects of greenhouse gases must also be able to simulate the significant cooling of the
large tropical land masses at glacial times with reduced greenhouse gas concentrations.
"Construction of a 1961-1990 European Climatology for Climate Change Modellng and
Impact Applications," M. Hulme (Clim. Res. Unit, Univ. E. Anglia, Norwich NR4 7TJ,
UK), D. Conway et al., Intl. J. Climatol., 15(12), 1333-1363, Dec. 1995.
A mean monthly climatology has been constructed at a resolution of 0.5° latitude by
0.5° longitude for nine surface climate variables. Details of construction and
interpolation to the grid points are discussed. This unique data base is being used by
researchers for ecosystem modeling, climate change impact assessment and climate model
validation; it is available from the authors.
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