Global environmental changes require a comprehensive understanding of the earth’s major systems and of the important ways in which these systems are linked. The major systems are the geosphere—processes of the Earth’s surface and interior; biosphere—life on land and in the sea; atmosphere—weather and climate; hydrosphere—water in the oceans, air, and on the continents; and cryosphere—snow and ice-covered regions, as well as the impact of human activities on these systems. The goal of earth system science is to obtain a scientific understanding of the entire earth system on a global scale. Recent studies of the continents, oceans, atmosphere, biosphere, and ice cover have revealed a far more complex and dynamic world than hitherto imagined.
In the past, diverse studies of volcanic activity, ocean chemistry, global climate, and biological processes would have been treated in isolation; we now recognize there are important links between them which themselves define new fields of study. Furthermore, the human population is no longer a passive spectator to earth processes, but an active participant on a worldwide scale. Human activity has become an agent of global change, depleting energy, mineral and water resources, altering rivers, coastlines and sedimentation patterns, polluting groundwater resources, and even changing the composition of the entire atmosphere, leading to climate changes with unforeseen and perhaps irreversible consequences. Distinguishing between natural changes and the results of large-scale economic and technological activity is a major challenge in earth system research.