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Improving the capability to predict and respond to such changes, whether naturally-occuring or the result of man's activities, will provide a great benefit to our Nation. A well coordinated Federal global change research program will be critical to realizing these improvements.

The U.S. Global Change Research Program

Key Global Change Scientific Questions. A better predictive understanding of global change requires improved answers to the following four major questions that form the core of the U.S. Global Change Research Program research agenda:

1. What Forces Initiate Global Change? These forces include changes in solar irradiance, in the abundance of atmospheric trace gases and aerosols, in land use, in biota, and in the earth's orbit. 

2. How Does the Earth System Respond to Changes in Forcing Functions? These responses or "feedbacks" include interactions among the climate, the ocean, the land, the biota, and the atmosphere.

3. How Has the Earth's Environment Changed in the Past? Differentiating between natural and human-induced global change requires clear documentation of the history of earth system variations over long time scales, especially prior to the influence of human activity. This documentation is provided by fossils, tree rings, pollen, soil composition, and sediments from the ocean, land, and ice.

4. How Well Can Global Change be Predicted? These evaluations include the ability of models to simulate past and present global changes and the biological responses to these changes.