Variability in the earth climate system: Decadal and longer timescales

Abstract

Global change—the cumulative impact of anthropogenic changes to water, energy, and biogeochemical cycles—is one of the defining issues for the geophysical and life sciences in the 1990s and beyond. The increasing emphasis on understanding the potential future climatic consequences of anthropogenic interference in the global carbon and trace gas cycles has driven an increased effort to understand the behavior of the climate system on decadal‐to‐centennial and longer timescales. The issues related to the long‐term behavior of the climate system are both of fundamental scientific interest and of importance to society, as a reading of the Climate Convention [United Nations, 1992] will immediately reveal. Variability on long timescales is challenging and exciting because much of the climate system's low frequency behavior and many long‐term changes arise from the coupling of the atmosphere to the ocean, biogeochemical cycles, and the cryosphere, as well as from internal dynamics [Pielke and Zeng, 1994]. Variability on decadal and longer timescales must be studied in an interdisciplinary fashion and challenges existing models and data sets, which have typically been developed or collected to address more limited problems.