principal unanswered scientific questions about global environmental change. This goal demands that funding and efforts be directed toward a coherent and coordinated suite of research activities and supporting observational, data management, and modeling capabilities, all aimed at imperative research objectives and clearly defined scientific questions. A sharply focused scientific strategy and a coherent programmatic structure are both critically needed. This report seeks to provide a framework for such a strategy and structure. The elaboration and implementation of this scientific strategy and programmatic structure will be the principal challenge for global change research over the course of the next decade.
Long before the industrial revolution, human activity began to alter the Earth's environment. However, only in this century has the scale of such alterations become global in scope; moreover, the rate of these recent changes is enormously high compared with the historical record. Today, on the threshold of a new millennium, it is clear that humans are inducing environmental changes in the planet as a whole. In fact, the human fingerprint is abundantly seen on the global atmosphere, the world oceans, and the land of all continents. This insight has brought about profound changes in the goals, priorities, and processes of both science and government.
Recognition that humans are causing global changes in the biology, physics, and chemistry of the environment—changes with immense significance for human society and economy—has prompted the U.S. government, and other national governments, to act. In 1990, Congress established the USGCRP to carry out an organized, coherent attack on the scientific issues posed by global environmental change.
The USGCRP had its principal roots in the 1980s, as both scientists and the public became increasingly aware of the links among human activities, current and future states of the global environment, and human welfare. The most immediate concerns were human-induced climate change, stratospheric ozone depletion from industrial emissions, and emerging evidence that the Earth's biogeochemical system was being perturbed by a broad range of human actions.
Some of the many antecedents of the USGCRP were seen still earlier. In the 1970s a convergence of long-standing scientific concerns (see below) and a series of climatic events led to the first World Climate Conference and to the establishment of the U.S. National Climate Program and the World Climate Program.1 In parallel, beginning in the mid-1970s, the U.S. Department of Energy (DOE) organized a major research program to assess the consequences of fossil-based energy production. Workshops chaired by the late Roger Revelle outlined a broad