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 10, NUMBER 5, MAY 1997
Two items in J.
Geophys. Res., 102(D5), Mar. 20, 1997:
"Evaluation and Intercomparison of Global Atmospheric Transport Models
Using 222Rn and Other Short-Lived Tracers," D.J. Jacob (Dept. Earth &
Planetary Sci., Harvard Univ., 29 Oxford St., Cambridge MA 02138; e-mail:
email@example.com), M.J. Prather et al., 5953-5970. Reports on an
intercomparison, sponsored by the World Climate Research Program in 1993, to
evaluate the capability of global models to capture the contributions of
convective and synoptic processes to transport on a global scale.
"Results from the Intergovernmental Panel on Climate Change
Photochemical Model Intercomparison (PhotoComp)," J. Olson (NASA-Langley
Res. Ctr., Hampton VA 23681; e-mail: firstname.lastname@example.org), M. Prather et
al., 5979-5991. PhotoComp was a tightly controlled model experiment intended to
determine the consistency among models used to predict changes in tropospheric
ozone. Calculated tropospheric photodissociation rates displayed significant
Forcing-Response Relationships for Greenhouse and Shortwave Radiative
Perturbations," V. Ramaswamy (NOAA/GFDL, POB 308, Princeton NJ 08542;
e-mail: email@example.com), C.T. Chen, Geophys. Res. Lett., 24(6),
667-670, Mar. 15, 1997.
Experiments with a general circulation model are used to compare the nature
of global radiative forcings (like CO2) and localized
forcings (like sulfate aerosols). The total climate feedback in the various
experiments did not differ significantly, and the global-mean climate
sensitivity was nearly the same for both global and spatially confined forcings.
However, forcings confined to the Northern Hemisphere midlatitudes exhibited a
steepening of the meridional gradient of temperature response.
Additivity of Climate Response for Combined Albedo and Greenhouse Perturbations,"
V. Ramaswamy (address above), C.T. Chen, ibid.,
24(5), 567-570, Mar. 1, 1997.
Uses model experiments to explore the extent to which the radiative effects
of globally distributed greenhouse gases and of regionally distributed sulfate
aerosols are linearly additive. Concludes that certain aspects of climate
responses are indeed additive, but there are several reservations.
Hadley Centre Coupled Ocean-Atmosphere GCM: Model Description, Spinup and
Validation," T.C. Johns (Hadley Ctr., Meteor. Off., London Rd., Bracknell,
Berkshire RG12 2SY, UK; e-mail: firstname.lastname@example.org), R.E. Carnell et al., Clim.
Dynamics, 13(2), 103-134, Feb. 1997.
Describes the new model and how its performance has improved over that of
the previous version. Verification runs emphasize the importance of including
forcing terms apart from greenhouse gases (such as sulfate aerosols) in climate
of Global Warming by Sulfate Aerosols," J.F.B. Mitchell (Hadley Ctr.,
Meteor. Off., London Rd., Bracknell, Berkshire RG12 2SY, UK; e-mail:
email@example.com), J. Clim., 10(2), 245-267, Feb. 1997.
Compares patterns of response in the surface climatology of a coupled
ocean-atmosphere general circulation model forced by increased CO2
alone, to patterns caused by forcing from both CO2 and aerosols,
from early industrial times to the end of the 21st century. Comparisons for
2030-2050, when the aerosol forcing is a maximum, showed that in summer, the
cooling due to aerosols weakens the monsoon circulations and reverses some of
the changes in the hydrologic cycle caused by greenhouse gases. Changes in
aerosol concentrations of the magnitude projected in the scenarios would have a
major effect on regional climate, especially over Europe and Southeast Asia.
"The Effect of
Greenhouse SSTs on ENSO Simulations with an AGCM," I.N. Smith (Div. Atmos.
Res., CSIRO, PMB 1, Mordialloc, Victoria 3195, Australia), M. Dix, R.J. Allan,
Model experiments with 2 X CO2 and prescribed sea surface
temperatures suggest that increased static stability may dampen the effects of
any nonlinear increase in evaporation and that any changes in the behavior of
ENSO due to predicted temperature increases in the tropics may not be
in a Global Coupled Ocean-Atmosphere Model: Multidecadal Amplitude Modulation
and CO2 Sensitivity," T.R. Knutson (NOAA/GFDL, POB 308,
Princeton NJ 08542; e-mail: firstname.lastname@example.org), S. Manabe, D. Gu,
ibid., 10(1), 138-161, Jan. 1997.
Results suggest that the impact of increased CO2 on ENSO is
unlikely to be clearly distinguishable from climatic variability in the near
future-unless ENSO is substantially more sensitive to increased CO2
than indicated in the present study.
Exchanges of Energy, Water, and Carbon Between Continents and the Atmosphere,"
P.J. Sellers (Johnson Space Flight Ctr., NASA, Mail Code CB, Houston TX 77058),
R.E. Dickinson et al., Science,
275(5299), 502-509, Jan. 24, 1997.
Reviews the past 20 years' development of land surface parameterization
resulting from advances in plant research, satellite data interpretation, and
large-scale field experiments. Schemes will soon be able to model the biological
and physical responses of the Earth system to future global change.
Biosphere Model of Land Surface Processes, Terrestrial Carbon Balance, and
Vegetation Dynamics," J.A. Foley (Inst. Environ. Studies, Univ. Wisconsin,
1225 S. Dayton, Madison WI 53706; e-mail: email@example.com), I.C.
Prentice et al., Global Biogeochem. Cycles,
10(4), 603-628, Dec. 1996.
Presents a new terrestrial biosphere model which incorporates land surface
biophysics, terrestrial carbon fluxes and global vegetation dynamics in a
single, physically consistent modeling framework. It provides a means of
simulating both rapid biophysical processes and long-term ecosystem dynamics in
from Increased CO2 and Direct and Indirect Effects of Sulfate
Aerosols," G.A. Meehl (Clim. & Global Dynamics Div., NCAR, POB 3000,
Boulder CO 80307; e-mail: firstname.lastname@example.org), W.M. Washington et al., Geophys.
Res. Lett., 23(25), 3755-3758, Dec. 15, 1996.
Gives preliminary results from the first climate sensitivity experiments
that included the indirect forcing effect of sulfate aerosols (through clouds),
in addition to the direct aerosol effect on albedo and the effect of transient
greenhouse gas forcing. Simulations corresponding to roughly 35 years into the
future indicate tropospheric warming almost everywhere, as the CO2
forcing overwhelms the negative radiative forcing from the sulfate aerosols.
There is also a general indication of weakening of the south Asian monsoon.
Time Series from Two Global Models with Tide Gauge Data," R. Tokmakian
(Dept. Oceanog., Naval Postgrad. Sch., 833 Dyer Rd., Rm. 328, Monterey CA 93943;
e-mail: email@example.com), Geophys. Res. Lett.,
23(25), 3759-3762, Dec. 15, 1996.
Demonstrates that two global ocean models, being used to understand ocean
dynamics by a large number of investigators, adequately represent local
instantaneous sea level. Discusses implications for global climate modeling.
Perspective on Global Climate Modeling," D.A. Randall (Dept. Atmos. Sci.,
Colorado State Univ., Fort Collins CO 80523), Bull. Amer. Meteor. Soc.,
77(11), 2685-2690, Nov. 1996.
Analyzes the roughly two dozen global modeling groups in the U.S., dividing
them into four categories: laboratories and universities, and development and
applications. Most groups are focusing on applications rather than development,
contrary to the early days of modeling, especially in universities. A key role
of university groups is to train new model developers. Outlines a simple but
functional conceptual organization of U.S. modeling groups to promote model
development and meet the needs of policy makers.
of Heating Rates Generated by Global Climate Model Longwave Radiation Codes,"
F. Baer (Dept. Meteor., Univ. Maryland, College Pk. MD 20742; e-mail:
firstname.lastname@example.org), N. Arsky et al., J. Geophys. Res.,
101(D21), 26,589-26,603, Nov. 27, 1996.
Seven frequently used algorithms were compared to assess their variability
to input data. Differences in algorithm output were pronounced when clouds were
present, particularly if clouds were thicker than one model level. For some
cloud configurations, the resulting heating rate profiles appear to have no
correspondence whatsoever to one another. The importance of these differences to
ultimate GCM climate predictions is currently under study.
"The Project for
Intercomparison of Land-Surface Parameterization Schemes (PILPS): 1992 to 1995,"
A. Henderson-Sellers, K. McGuffie, A.J. Pitman (Sch. Earth Sci., Macquarie
Univ., North Ryde, Sydney, 2109 NSW, Australia; e-mail:
email@example.com), Clim. Dynamics, 12(12), 849-859,
Describes the planned five phases of the PILPS of the World Climate Research
Program, and the status of each. The earlier phases show that individual
land-surface schemes capture specific components of land-surface interactions
with reasonable accuracy, but no one scheme captures the whole system
satisfactorily and accurately. The final phase will couple selected land-surface
schemes to the NCAR climate system model and to the Australian Bureau of
Meteorology limited area model.
Greenhouse-Gas-Induced Climate Change with an Optimal Fingerprint Method,"
G.C. Hegerl, (Max Planck Inst. Meteor., Bundestr. 55, D-21046 Hamburg, Ger.),
J. Clim., 9(10), 2281-2306, Oct. 1996.
This study attempts to detect anthropogenic climate change in the
observational record of near-surface temperatures by trying to identify as a "fingerprint"
the spatial and temporal changes in temperature that are expected to
characterize anthropogenic change, should it be present. A coupled
ocean-atmosphere general circulation model is used, both to estimate the
fingerprint and to estimate natural climatic variability. The estimate of
natural variability is then used to statistically modify (optimize) the
fingerprint to reduce the confounding influence of random fluctuations.
The null hypothesis, that the latest observed 20-year and 30-year trend of
near-surface temperature (ending in 1994) is part of natural climate
variability, is rejected with a risk of less than 2.5%-5%. However, to attribute
the observed warming uniquely to anthropogenic greenhouse gas forcing, more
information is needed on the climate's response to other forcing mechanisms
(e.g., changes in solar radiation, or volcanic or anthropogenic sulfate
aerosols) and their interactions. Furthermore, the estimate of internal
(natural) climate variability is still uncertain. With these caveats, the
conclusion remains that a statistically significant, externally induced warming
has been observed.
Parameterization of the Solar Radiative Properties of Cirrus Clouds for Climate
Models," Q. Fu (Dept. Oceanog., Dalhousie Univ., Halifax NS B3H 4J1, Can.;
e-mail: firstname.lastname@example.org), J. Clim., 9(9), 2058-2082, Sep. 1996.
The parameterization is based on improved light scattering calculations
using ice crystal size distortions measured by aircraft. Evaluation of the
parameterization demonstrates its reliability for climate model applications.
Dynamical Thermostat," A.C. Clement (Lamont-Doherty Earth Observ., Rte. 9W,
Palisades NY 10964; e-mail: email@example.com), R. Seager et al.,
Investigates the role of ocean dynamics in the regulation of tropical sea
surface temperature using a coupled ocean-atmosphere model. Results suggest that
ocean dynamics can be a complicating but essential element in climate change
Uptake of CO2: Interaction Between Ocean Circulation and Biology,"
E. Maier-Reimer (M. Planck Inst. Meteor., Bundesstr. 55, D-20146 Hamburg, Ger.),
U. Mikolajewicz, A. Winguth, Clim. Dynamics,
12(10), 711-721, Sep. 1996.
Experiments using an ocean GCM subjected to global warming coupled with a
model of ocean biogeochemical cycling. Results justify the practice of running
climate models and carbon cycle models independently, as feedbacks are slight.
Elements," J.A.T. Bye (Flinders Inst. for Atmos. & Marine Sci.,
Flinders Univ., GPO Box 2100, Adelaide 5001, Australia), R.A.D. Byron-Scott,
A.H. Gordon, J. Clim., 9(7), 1546-1560, July 1996.
Presents an analytical climate model and examines the statistics of
simulated climates generated by atmospheric random forcing.
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