It may not be overstating the facts to say that a revolution has occurred in the Earth sciences during the past twenty-five years. In 1975, forecasts of climate variability for the next year were not considered possible, and in fact, the term "climate variability" was viewed by some as an oxymoron. The phenomenon called El Niño, and its companion the Southern Oscillation, had barely begun to enter the consciousness of the scientific community. The public at large, except in a few regions, had no idea of the relevance that El Niño might have for them. Now, we feel that we have a reasonable understanding, both theoretical and pragmatic, of the coupled ocean-atmosphere processes that result in the El Niño-Southern Oscillation (ENSO) phenomenon and lead to its global impacts. We are beginning to take the first steps toward a regular, operational effort to predict ENSO and its consequences, and to develop projects that will lead to applications of such predictions in the global community.
In this issue of CONSEQUENCES, three of the leaders of the scientific effort that has brought about this revolution describe the nature of ENSO, the science underpinning the prediction efforts, and the problems and potential associated with applying climate information to real world problems. Steve Zebiak, who with Mark Cane developed the first numerical model capable of actually predicting an El Niño event, reviews the scientific understanding of ENSO and the future of dynamical climate prediction. Chet Ropelewski, who first described the full global impacts of El Niño, shows us the present understanding of the global impacts of ENSO, with an emphasis on the massive 1997-98 El Niño. Ed Sarachik, who has led many of the efforts to apply climate information to the real world, will explain the challenges facing our attempts to make climate forecasts more useful.
This revolution has been brought to fruition by a remarkable convergence of scientific energy and public support. A series of international research programs, including in particular the Tropical Oceans/Global Atmosphere (TOGA) program and its successor the Climate Variability and Predictability (CLIVAR) program, coordinated by the World Climate Research Programme and strongly supported by national research budgets throughout the world, have given us the theoretical support, the observing systems, and the predictive tools required to make usable forecasts. The scientific community involved in this effort began to understand during the 1980s that a new institutional framework would be needed to ensure that the forecasts that could be generated would actually be used appropriately. From that understanding developed a proposal for a new international organization, where improved predictive methods would be developed, forecasts would be made and disseminated, applications would be developed and implemented, and training in both climate science and applications would be provided.
Columbia University, in cooperation with NOAA, has recently established the International Research Institute for Climate Prediction (IRI) to accomplish these objectives. The IRI, currently housed at the Lamont-Doherty Earth Observatory in Palisades, NY, is still in its infancy, but is already providing important contributions to the global effort to make and use climate predictions. In the years to come, the IRI and its international partners will be a vital component of the global effort to build sustainable societies through optimal use of environmental information.