This NASA shuttle photograph (opposite page), taken on a March morning in 1994, and the explanatory diagram show a regional "haze" inland from the coast of California. While no chemical analysis is available, the haze is a widespread aerosol from sources that probably include smoke particles from biomass combustion and cities in the region. The enhanced albedo due to the haze causes sunlight to be reflected upward and thereby to fail to reach the ground. This constitutes a "direct climate forcing."

The aerosol cloud is visible from the northern extremity of the Sacramento Valley on the left to the Bakersfield area of the San Joaquin Valley on the right, a distance of about 600 kilometers. The Sierra Nevada mountains and the coastal range bound the aerosol-laden valley.

The photograph also shows coastal stratus clouds that extend along the coast and penetrate into the San Francisco Bay region. The albedo of these clouds, which can be influenced by anthropogenic aerosols, clearly controls the albedo of the oceanic portion of this view.

(Shuttle photograph SS062-86-066, courtesy of the Earth Science Branch, NASA/Johnson Space Center, Houston, Texas)

Cover art by Carrie Mallory. Ms. Mallory received her Bachelor of Fine Arts degree from the Cooper Union. She draws on the natural world and the effects of age on man-made objects for many of her themes. She has exhibited at a number of juried shows in the Northern Virginia area and has provided art for several NRC report covers. The art for this cover involved transferring an original photograph to an already cracked lithograph stone and adding texture with traditional litho crayons. As expected, the stone cracked further during the printing process, yielding only a few prints before disintegrating completely.

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