Most scientists agree that the earth is heating up, but the cause of global warming is less certain. In this hour of To the Best of Our Knowledge, a climate model that "fingerprints" the possible suspects. From volcanoes, to El Nino, to human activity, find out which is the mostly likely culprit. Also, times when weather made history.

SEGMENT 1:

Michael Oppenheimer, Chief Scientist at the Environmental Defense Fund in New York, tells Jim Fleming what he and the other delegates are discussing at the gobal climate talks in Kyoto, Japan. Oppenheimer supports the proposals for a treaty limiting emissions of greenhouse gasses. Gail McDonald, President of the Global Climate Coalition, is also in Kyoto. She tells Steve Paulson that her organization represents energy producers who believe Draconian measures are unnecessary and not justified by our scientific understanding of the world's climate.

SEGMENT 2:

Steve Lerner is research director of Commonweal, a health and environmental research institute, and the author of "Eco-Pioneers: Practical Visionaries Solving Today's Environmental Problems." He tells Steve Paulson about an innovative project involving rooftop commercial produce gardening in New York, and says projects like this are economically viable when you factor in the environmental costs of existing practices.

SEGMENT 3:

David Laskin is the author of "Braving the Elements: The Stormy History of American Weather." He tells Jim Fleming that Americans have made the weather part of their national identity since Colonial days; recalls the great blizzards of the High Plains and the Black Blizzards of the Dust Bowl; and speculates on the reasons why some people are obsessed with extreme weather.

Distribution dates:

• week of 12/07/97 - hour 2