The Scientific Committee on Problems of the Environment (SCOPE) was established in 1969 by the International Council of Scientific Unions (ICSU) to assemble, review, and assess information on man-made environmental changes and the effects of these changes on man. The work of this committee has already resulted in 17 books dealing with a wide range of environmental problems, with particular emphasis on the needs of developing countries. The global carbon cycle was described and analyzed in SCOPE Report 13, published in 1979. The volume under review, SCOPE Report 16, carries this analysis further. It presents the results of a workshop on carbon cycle modeling held at Scripps Institution of Oceanography in March 1979. The goal of the workshop was to assess the status of quantitative models of the global carbon cycle, to compare the predictions of different models, to develop methods for testing the reliability of these predictions, and to suggest how future models might be made more realistic.