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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 8, NUMBER 9, SEPTEMBER 1995

PROFESSIONAL PUBLICATIONS...
OF GENERAL INTEREST: CLOUDS AND AEROSOLS

Item #d95sep10

"Climate Response to Increasing Levels of Greenhouse Gases and Sulphate Aerosols," J.F.B. Mitchell, (Hadley Ctr., Meteor. Office, Bracknell RG12 2SY, UK), T.C. Johns et al., Nature, 376(6540), 501-504, Aug. 10, 1995.

Uses a coupled ocean-atmosphere GCM to simulate past and future climate since the beginning of the near-global instrumental temperature record, which includes the radiative effects of sulfate aerosols. The inclusion of aerosols significantly improves agreement with global mean and large-scale patterns of temperature in recent decades. Predicts a future warming of 0.2K per decade; global warming could accelerate as greenhouse-gas forcing begins to dominate over aerosol forcing. (See related News Note, this issue--Sep. 1995.)

Item #d95sep11

Two related items in Nature, 376(6540), Aug. 10, 1995:

"An Absorbing Mystery," W.J. Wiscombe (Lab. Atmos., NASA-Goddard, Greenbelt MD 20771), 466-467. Discusses the research context of the following paper. Cess et al. recently challenged the way climate models treat the radiative effects of clouds; the following paper shows that the effects proposed by Cess et al. have less impact than originally suggested. But much greater attention is needed to the basics of cloud radiative balance before such uncertainties of current models can be reduced.

"The Variable Effect of Clouds on Atmospheric Absorption of Solar Radiation," Z. Li (Canada Ctr. for Remote Sensing, 588 Booth St., Ottawa ON K1V 0J6, UK), H.W. Barker, L. Moreau, 486-490. Examines the effect of clouds using a four-year global record of solar flux observed from both space and the Earth's surface. The effect of clouds is highly variable and, contrary to some recent suggestions, present GCMs should be able to incorporate cloud absorption into climate simulations.

Item #d95sep12

"Climate Response to Indirect Anthropogenic Sulfate Forcing," D.J. Erickson III (Theoret. Studies & Modeling, NCAR, POB 3000, Boulder CO 80307), R.J. Oglesby, S. Marshall, Geophys. Res. Lett., 22(15), 2017-2020, Aug. 1, 1995.

Tests the climatic influence of a cloud albedo change hypothesized to result from anthropogenic increases in atmospheric sulfur, based on 30-year runs of the NCAR GCM. The response is strongest in the Northern Hemisphere winter, with cooling over the North Atlantic and North Pacific oceans on the order of 2-6° C. Due to changes in the hemispheric wave train, the equilibrium climate does not cool over central Europe, despite the region's high concentration of sulfate aerosol. These results may help explain the long-standing issue of what has caused the observed cooling over the North Atlantic and North Pacific over the last decades, a feature not explained by increases in greenhouse gases alone.