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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 3, NUMBER 2, FEBRUARY 1990

PROFESSIONAL PUBLICATIONS...
EARTH SYSTEM SCIENCE

Item #d90feb23

"Global Climate Change and Intensification of Coastal Ocean Upwelling," A. Bakun (Nat. Marine Fisheries Serv., NOAA, POB 831, Monterey CA 93942), Science, 247(4939), 198-201, Jan. 12, 1990.

Evidence from several different regions suggests that the major coastal upwelling systems of the world have been growing in upwelling intensity, as greenhouse gases have accumulated in the earth's atmosphere. More pronounced cool, foggy summer conditions might typify the coastlands of northern California if upwelling intensifies from global warming. Effects of enhanced upwelling on the marine ecosystem are uncertain but potentially dramatic.

Item #d90feb24

"Sensitivity of the Earth's Radiation Budget to Changes in Low Clouds," A. Slingo (NCAR, POB 3000, Boulder CO 80307), Nature, 343(6253), 49-51, Jan. 4, 1990.

Using a 3-D general circulation model, the top-of-atmosphere radiative forcing by doubled CO₂ concentrations can be balanced by modest relative increases of about 15-20% in the amount of low clouds and of 20-35% in liquid-water path, and by decreases of 15-20% in mean drop radius (depending on the model version). This indicates that a minimum relative accuracy of about 5% is needed, both to simulate these quantities in climate models and to estimate climate response by monitoring the quantities over extended periods from satellite platforms.

Item #d90feb25

"Climate-Induced Changes in Forest Disturbance and Vegetation," J.T. Overpeck (Lamont-Doherty Geol. Observ., Columbia Univ., Palisades NY 10964), D. Rind, R. Goldberg, ibid., 51-53.

Climate model results indicate that global warming favors increased rates of forest disturbance (drought, wind, fire), and new sensitivity tests carried out with a vegetation model indicate that climate-induced increases in disturbance could alter the total biomass and compositional response of forests to future warming. Results reinforce the hypothesis that forests could be greatly altered by the first part of the next century, and also confirm the potential utility of selected time series of fossil pollen data for studying natural climate variability on the scale of centuries.

Item #d90feb26

"Growth of Greenland Ice Sheet: Interpretation," H.J. Zwally (Oceans and Ice Br., Code 671, NASA/GSFC, Greenbelt MD 20771), Science, 246(4937), 1589-1591, Dec. 22, 1989.

An observed 0.23 m yr-1 thickening of the Greenland ice sheet indicates a 25% to 45% excess ice accumulation over the amount required to balance the outward ice flow. Discusses how ice sheet mass, sea level, and climate are related: over the short term, global warming could produce more precipitation and greater ice accumulations at Greenland and Antarctica and thus a drop in sea level; over longer periods, however, the dynamic response of the glaciers to warmer temperatures and increased precipitation is less clear, and sea-level rise could occur if the glaciers started flowing faster. Increasing ice thickness suggests that the precipitation is higher than the long-term average; higher precipitation may be a characteristic of warmer climates in polar regions.

Item #d90feb27

"Growth of Greenland Ice Sheet: Measurement," H. J. Zwally (address immed. above), A.C. Brenner et al., ibid., 1587-1589.

Discusses technical details of satellite altimetry measurements of the previous paper.

Item #d90feb28

"Direct and Remote Sensing Observations of the Effects of Ships on Clouds," L.F. Radke (Dept. Atmos. Sci., Univ. Wash., Seattle WA 98195), J.A. Coakley Jr., M.D. King, Science, 246(4934), 1146-1149, Dec. 1, 1989.

Simultaneous observations of two ship tracks, in stratus clouds from a satellite and in situ from an aircraft, show that in the ship tracks the droplet sizes were reduced, and total concentrations of both droplets and particles were substantially increased from those in adjacent clouds. Cloud reflectivity along the tracks was enhanced at 0.63 and 3.7 micrometers. Results support the contention that ship track signatures in clouds are produced primarily by particles emitted from ships.

Item #d90feb29

"Carbon Redox and Climate Control Through Earth History: A Speculative Reconstruction," T.R. Worsley (Dept. Geol., Ohio Univ., Athens OH 45701), R.D. Nance, Palaeogeog., Palaeoclimatol., Palaeoecolog. (Global Plan. Change Sec.), 75, 259-282, Dec. 1989.

Attempts to show a pattern in earth systems evolution by reviewing the ways in which the earth's atmosphere, hydrosphere, biosphere and crust have interacted in response to continuously increasing solar intensity. Shows how these processes have been modulated by tectonic processes to produce a pattern consistent with the preserved geologic record. Relies on corroborating lines of evidence that suggest strong coupling among variables involved.

Item #d90feb30

"Simulation of the Regional Climatic Impact of Amazon Deforestation," J. Lean (Meteor. Off., Bracknell, Bershire RG12 2SZ, UK), D.A. Warrilow, Nature, 342(6248), 411-413, Nov. 23, 1989.

Results from a three-year simulation using a general circulation model, in which the Amazon tropical forest and savannah is replaced with pasture, showed that the simulated local climate response was dominated by a weakened hydrological cycle, with less precipitation and evaporation and an increase in surface temperature. Decreased surface roughness and increased albedo caused the reductions in precipitation and evaporation. (R.E. Dickinson discusses implications of this research on p. 343 of the same issue.)

Item #d90feb31

"Toward Estimation of Climatic Effects Due to Arctic Aerosols," J.-P. Blanchet (Can. Clim. Ctr., City of North York, Ont. M3H 5T4, Can.), Atmos. Environ., 23(11), 2609-2625, 1989.

Reviews estimated climatic implications of principal anthropogenic aerosols (soot and sulfates) obtained by observation and modeling at three scales of dimension: (1) the aerosol scale where optical properties are determined, (2) the kilometer scale, where the radiative fluxes and diabatic heating are felt, and (3) the regional and hemispheric scales where the climate questions pertain.

Item #d90feb32

"Holocene-Late Pleistocene Climatic Ice Core Records from Qinghai-Tibetan Plateau," L.G. Thompson (Byrd Polar Res. Ctr., Ohio State Univ., Columbus OH 43210), E. Mosley-Thompson et al., Science, 246(4929), 474-477, Oct. 27, 1989.

Analysis of three ice cores from the Dunde ice cap portray late glacial stage conditions, but also indicate that the very recent past (the last 60 years) was one of the warmest periods in the entire record, equaling levels of the Holocene maximum between 6000 and 8000 years ago. Climate model results of Hansen and others suggest that the central part of the Asian continent is likely to be one of the regions most strongly affected by the anticipated global warming caused by the greenhouse effect. This study suggests recent warming there has been substantial, but a connection with greenhouse warming has not been established.