Roughly 30 percent of solar radiation directed toward earth is reflected directly back into outer space. The remaining 70 percent is absorbed by earth and re-emitted outward as long-wave--or infra-red--radiation. While transparent to incoming solar radiation, certain gases--notably carbon dioxide, nitrous oxide, methane, and chlorofluorocarbons--absorb, or trap, this outgoing infra-red radiation near earth's surface, producing an increase in temperature. This is so-called greenhouse effect. The greater concentration of these greenhouse gases, more pronounced will be effect. Despite uncertainties, scientific consensus recorded at Villach, Austria, in 1985 was that the understanding of greenhouse question is sufficiently developed that scientists and policy-makers should begin an active collaboration to explore effectiveness of alternatives and adjustments. The recent scientific assessment of climate change, conducted under auspices of UN Intergovernmental Panel on Climate Change, has only strengthened view that a concerted multilateral response is called for.

With the opening of the Berlin Wall and the emergence of democracy in Eastern Europe, there are widespread pressures-- including the domestic deficit-- for major conventional force reductions in Europe. Using a dynamic model of warfare he has developed, Joshua M. Epstein analyzes the current balance and demonstrates that NATO's security would progressively improve with the implementation of the Warsaw Treaty Organization's unilateral reductions, the Conventional Forces in Europe (CFE) agreement, and a CFE II agreement under which NATO and the WTO would reduce forces to equal levels 50 percent below the levels specified in CFE I. Epstein argues that the improvement under such a CFE II agreement would be sufficient to permit the United States to make further, unilateral, reductions without endangering NATO's security.

Agent-based computational modeling is changing the face of social science. In Generative Social Science , Joshua Epstein argues that this powerful, novel technique permits the social sciences to meet a fundamentally new standard of explanation, in which one "grows" the phenomenon of interest in an artificial society of interacting agents: heterogeneous, boundedly rational actors, represented as mathematical or software objects. After elaborating this notion of generative explanation in a pair of overarching foundational chapters, Epstein illustrates it with examples chosen from such far-flung fields as archaeology, civil conflict, the evolution of norms, epidemiology, retirement economics, spatial games, and organizational adaptation. In elegant chapter preludes, he explains how these widely diverse modeling studies support his sweeping case for generative explanation. This book represents a powerful consolidation of Epstein's interdisciplinary research activities in the decade since the publication of his and Robert Axtell's landmark volume, Growing Artificial Societies . Beautifully illustrated, Generative Social Science includes a CD that contains animated movies of core model runs, and programs allowing users to easily change assumptions and explore models, making it an invaluable text for courses in modeling at all levels.

How do social structures and group behaviors arise from the interaction of individuals? Growing Artificial Societies approaches this question with cutting-edge computer simulation techniques. Fundamental collective behaviors such as group formation, cultural transmission, combat, and trade are seen to "emerge" from the interaction of individual agents following a few simple rules. In their program, named Sugarscape, Epstein and Axtell begin the development of a "bottom up" social science that is capturing the attention of researchers and commentators alike. The study is part of the 2050 Project, a joint venture of the Santa Fe Institute, the World Resources Institute, and the Brookings Institution. The project is an international effort to identify conditions for a sustainable global system in the next century and to design policies to help achieve such a system. Copublished with the Brookings Institution Bradford Books imprint