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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 2, NUMBER 11, NOVEMBER 1989

PROFESSIONAL PUBLICATIONS...
GLOBAL MODELING

Item #d89nov40

"Scandinavian, Siberian, and Arctic Ocean Glaciation: Effect of Holocene Atmospheric CO₂ Variations," D.R. Lindstrom (Dept. Geol. Sci., POB 4348, Univ. Ill., Chicago IL 60680), D.R. MacAyeal, Science, 245(4918), 628-631, Aug. 11, 1989.

Uses a computer model of coupled ice-sheet shelf behavior to evaluate whether observed changes in atmospheric CO₂ concentrations could have caused the advance and retreat of Pleistocene ice sheets in the Eurasian Arctic. In simulations, climatic warming associated with the Holocene rise of atmospheric CO₂ was sufficient to collapse the widespread glaciation and restore present-day ice conditions.

Item #d89nov41

"Diurnally Varying Regional Climatic Simulations," B.G. Hunt (CSIRO Div. Atmos. Res., Private Bag No. 1, Mordialloc, Vic. 3195, Australia), H.B. Gordon, Intl. J. Climatol., 9(4), 331-356, July-Aug. 1989.

Assesses a general circulation model's performance simulating diurnal and interdiurnal variability. Identifies critical features which should be monitored in climatic-change experiments. The unique diurnal variations simulated at individual geographical points suggest that systematic distortions must occur in most near-surface processes in non-diurnal models. The interdiurnal variability of the model is illustrated by a number of examples, one of which highlights the potential misrepresentation of air-sea exchanges in models employing fixed sea-surface temperatures.

Item #d89nov42

"Simulated Global Distribution and Deposition of Reactive Nitrogen Emitted by Fossil Fuel Combustion," H. Levy II (Geophys. Fluid Dynamics/NOAA, POB 308, Princeton Univ., Princeton NJ 08542), W.J. Moxim, Tellus, 41B(3), 256-271, July 1989.

Nitrogen oxides play a major role in the global reactivity of the troposphere and, in turn, control the levels of a number of greenhouse gases that influence the global environment. This study uses the medium resolution GFDL general circulation transport model to simulate the global spread and deposition of reactive nitrogen. Identifies a number of important source regions and long-range transport mechanisms. Suggests a major role for either stratospheric injection or an upper tropospheric source.

Item #d89nov43

"A Stochastic Lagrangian Atmospheric Transport Model to Determine Global CO₂ Sources and Sinks--A Preliminary Discussion," J.A. Taylor (Coop. Inst. Res. Environ. Sci., CB 449, Univ. Colorado, Boulder CO 80309), ibid., 272-285.

Model estimates of the yearly averaged latitudinal gradient of CO₂ concentration match the observed CO₂ observations (obtained from the National Oceanic and Atmospheric Administration Geophysical Monitoring for Climatic Change (GMCC) program), except over the southern oceans. A biospheric growing season net flux of 6.5 Gt C was found from model simulations,which explains the observed seasonal cycle in CO₂ concentrations. Suggests further study of the intensity of the biospheric fluxes above 60<198>N, oceanic fluxes below 45<198>S and model vertical transport.

Item #d89nov44

"Design and Critical Appraisal of an Accelerated Integration Procedure for Atmospheric GCM/Mixed-Layer Ocean Models," M.E. Schlesinger (Dept. Atmos. Sci., Strand Agric. Hall 326, Oregon State Univ., Corvallis OR 97331), Z.-C. Zhao, D. Vickers, J. Clim., 2(7), 641-655, July 1989.

The accelerated integration procedure (AIP) attained the equilibrium climates in these simulations with the computer-time equivalent of about 2.5 unaccelerated solar cycles (years) but, after the switch from the AIP to the unaccelerated normal integration procedure (NIP), the temperatures increased to new equilibrium values. Found that the increase in the amplitude of the annual cycle of atmospheric temperature from the AIP to the NIP, acting through the ice-albedo/temperature feedback mechanism, causes the change in the equilibrium climate following the AIP/NIP switch. Suggests caution in using the AIP.

Item #d89nov45

"The Dynamic Greenhouse: Feedback Processes that May Influence Future Concentrations of Atmospheric Trace Gases and Climatic Change," D.A. Lashof (U.S. EPA, Washington DC 20460), Clim. Change, 14(3), 213-242, June 1989.

Assesses the relative importance of a wide range of feedbacks by estimating the gain associated with each individual process. The gain from biogeochemical feedbacks is estimated to be 0.05-0.29, compared to 0.17-0.77 for geophysical climate feedbacks. While each of the biogeochemical feedbacks is modest compared to the vapor feedback, the biogeochemical feedbacks in combination have the potential to substantially increase the climate change associated with any given initial forcing.

Item #d89nov46

"The Role of Cloud Microphysical Processes in Climate: An Assessment From a One-Dimensional Perspective," K.-N. Liou (Dept. Meteor., Univ. Utah, Salt Lake City UT 84112), S.-C. Ou, J. Geophys. Res., 94(D6), 8599-8607, June 20, 1989.

Hypothesizes that there are uncertainties in cloud microphysical processes, and that a possible key to climate stability due to external radiative perturbations is the availability of larger or smaller cloud droplets. Smaller cloud droplets may be produced by additional condensation nuclei over the oceans as a result of greenhouse warming and pollution over land. Larger cloud droplets could be caused by the removal of cloud-forming nuclei, resulting from enhanced precipitation due to greenhouse perturbations. It is critically important to have a global climatology of the cloud particle radii for various cloud types in the investigation of the role of clouds in climate.

Item #d89nov47

"Modeling Climate Change: An Assessment of Sea Ice and Surface Albedo Feedbacks," W.J. Ingram (Dynamical Climatol. Br., Met O 20, United Kingdom Meteor. Off., Bracknell, Berkshire RG12 2SZ, UK), C.A. Wilson, J.F.B. Mitchell, ibid., 94(D6), 8609-8622, June 20, 1989.

The net strength of these feedbacks in simulations of climate change has been estimated for GCMs using a variety of methods; several are applied in a single CO₂-doubling experiment with the U.K. Meteorological Office GCM. Different methods give values differing by up to a factor of 2 and are shown to be estimating different quantities. Results emphasize the importance of clouds, both in shielding surface albedo changes and so reducing their effect, and in contributing directly to planetary albedo changes. Concludes that care is needed in quantifying these feedbacks and that previously published numbers are not all comparable.

Item #d89nov48

"Climate Sensitivity Due to Increased CO₂: Experiments with a Coupled Atmosphere and Ocean General Circulation Model," W.M. Washington (NCAR, Boulder CO 80307), G.A. Meehl, Clim. Dynam., 4(1), 1-38, June 1989.

Three simulations were run on the coupled model: (1) instantaneous doubling of CO₂ (from 330 to 660 ppm), (2) CO₂ increasing linearly at a rate of 1% per year starting at 330 ppm, and (3) CO₂ held constant at 330 ppm. Results at the end of 30 years of simulation showed a globally averaged surface air temperature increase of 1.6<198>C for the instantaneous doubling and 0.7<198>C for the transient forcing case. Found that geographical plots of surface air temperature change in the transient case show patterns of regional climate anomalies that differ from those in the instantaneous doubling case, particularly in the North Atlantic and northern European regions. Suggests that differences in CO₂ forcing in the climate system are important in determining response to CO₂ change and time-dependent climate anomalies.

Item #d89nov49

"Seasonal Climatic Changes Induced by Doubled CO₂ as Simulated by the OSU Atmospheric GCM/Mixed-Layer Ocean Model," M.E. Schlesinger (Dept. Atmos. Sci., Oregon State Univ., Corvallis OR 97331), Z.-C. Zhao, J. Clim., 2(5), 459-495, May 1989.

Simulations with CO₂ concentrations of 326 ppmv (1xCO₂) and 625 ppmv (2xCO₂) were performed using an accelerated procedure for 45 solar cycles (years), followed by the normal unaccelerated integration procedure for 24 and 16 solar cycles, respectively. In comparison with CO₂-doubling simulations by other models, the OSU model simulates an annual and global mean surface air temperature warming of 2.8<198>C compared to 3.5-5.2<198>C, and an increase in the global-mean precipitation rate of 7.8% compared to 7.1-11.0%. The OSU model also simulates a dessication of the Northern Hemisphere continents almost everywhere in summer. This is in agreement with other models except the NCAR model results.

Item #d89nov50

"Analysis of Polar Clouds from Satellite Imagery Using Pattern Recognition and a Statistical Cloud Analysis Scheme," E.E. Ebert (Bureau Meteor., GPO Box 1289K, Melbourne, Vic. 3001, Australia), J. Appl. Meteor., 28(5), 382-399, May 1989.

Combines a pattern recognition algorithm with a hybrid histogram-spatial coherence scheme to derive cloud classification and fractional coverage, surface and cloud visible albedos, and infrared brightness temperatures from multispectral AVHRR satellite imagery. An important result is that the prior classification of a sample may significantly improve the accuracy of the analysis of cloud fraction, albedos and brightness temperatures over that of an unclassified sample. The automated classification and analysis for a set of AVHRR imagery from the summertime Arctic is in good agreement with manual interpretation of the satellite imagery.

Item #d89nov51

"A County-Level Approach to Regional Resource Analysis Based on Climatic Simulation," S.L. Schuhardt, R.M. Cushman (Carbon Dioxide Info. Anal. & Res. Prog., Oak Ridge Nat Lab., Oak Ridge TN 37831), T.A. Boden, J. Clim., 2(2), 113 ff., Feb. 1989.

Uses two simple approaches to demonstrate the effects on the production of soybeans of a possible climate change due to a doubling of atmospheric CO₂. The first approach assumes that future yields will be determined by current climate-yield relationships; the second uses a multiple regression equation that relates yield to simulated June and August temperature and July, August, and September-June precipitation. These two simple analyses show that soybean yields might decline in areas where the crop is now grown but could expand northwards and eastwards, and that it is possible to perform analyses of climate change effects using county-level data combined with additional information.

Item #d89nov52

"Modeling the Trends of the Variability Characteristics of the Thermodynamic Conditions of the Earth's Climatic System," A.A. Arskii (Inst. Atmos. Phys., Acad. Sci., Moscow 109017, USSR), I.I. Mokhov, V.K. Petukhov, Izvestiya, Atmos. and Ocean Phys., 25, 3-13, Jan. 1989. In Russian.

Uses a stochastic energy balance model to study the hemispheric surface temperature, equator-to-pole temperature difference and ice-snow cover as a function of the temperature variability trends of the earth's climate system. Examines the dependence of the trends on random-force parameterization and on the heat capacity of the system. Shows that the variance of the meridional gradient of the surface temperature tends to increase in the case of hemispheric warming.