Report on the CLIVAR (Climate Varibility and Predictability) Program

• To describe and understand the physical processes responsible for climate variability and predictability on seasonal, interannual, decadal, and centennial time scales, through the collection and analysis of observations and the development and applica tion of models of the coupled climate system, in co-operation with other relevant climate-research and observing programs.
• To extend the record of climate variability over the time scales of interest through the assembly of quality-controlled paleoclimatic and instrumental data sets.
• To extend the range and accuracy of seasonal to interannual climate predictions through the development of global coupled models.
• To understand and predict the response of the climate system to the growth of the radiatively active gases and aerosols and to compare these predictions to the observed climate record in order to detect the anthropogenic modification of the natural cl imate signal.

The CLIVAR program is initially organized into three component programs:

• CLIVAR-GOALS: A study of seasonal-to-interannual global variability and predictability,
• CLIVAR-DecCEN: A study of decadal-to-centennial global variability and predictability, and
• CLIVAR-ACC: A study of the response of the climate system to the addition of radiatively active gases and aerosols to the atmosphere.

CLIVAR-GOALS will examine the variability and predictability of the Global Ocean Atmosphere Land System on seasonal-to-interannual time scales. CLIVAR-GOALS will build on the successful TOGA program by:

• maintaining the TOGA Observing system in the tropical Pacific and further developing the predictive skill for SST and concomitant climate variables in the tropics;
• Expanding the study of seasonal-to-interannual variability into the global tropics, including tropical oceans and land masses;
• studying the interaction of monsoons with ENSO with a view towards improving the predictability of both;
• studying the interaction between the tropics and extratropics with the intention of understanding predictability and developing predictive skills for extratropical regions;
• studying the existence of seasonal-to-interannual variability and predictability in the extra tropics locally induced by the oceans, land surface processes, or sea-ice processes.

CLIVAR-DecCen will examine the mechanisms of variability and predictability of climate fluctuations on decadal-to-centennial time scales by:

• describing and under-standing the patterns of global decadal-to-centennial variability in the instrumental, paleoclimatic, and model records to the extent possible;
• extending the records of climatic variability by concerted efforts at data recovery, reanalysis of existing atmospheric and oceanic data, finding new paleoclimatic indices, and instituting new oceanographic monitoring sites;
• developing appropriate observing, computing, and data collection and dissemination systems needed to describe, understand, and predict global decadal variability.

It is expected that decadal-to-centennial climate variability arises from special regions of the world's oceans (water mass transformation regions and, strong boundary currents and return path "choke points") and efforts will be devoted to identifying these specific regions and understanding the mechanisms by which the ocean and atmosphere interact to give this variability.

CLIVER-ACC will examine the nature of Anthropogenic Climate Change in primarily a modeling context by:

• simulating the response of the climate system to the anthropogenic increases in radiatively active gases and aerosols using state-of-the-art coupled atmosphere-ocean-land-cryosphere models;
• identifying the patterns of anthropogenic modification of the natural climate system, both mean and variable;
• using these identifications for interpreting natural climate variability and for detecting the trends of greenhouse warming.

These component programs will be designed in a series of Implementation Meetings which will design and launch individual CLIVAR projects involving observations, modeling, the analysis of instrumental and paleoclimatic records, and process studies. As the CLIVAR program develops, it is intended that the component programs merge and projects be launched that cut across the time scales and component programs. Two CLIVAR Numerical Experimentation Groups will be formed to coordinate international modellin g studies. A number of panels will be transitioned from TOGA and WOCE to facilitate the implementation of the CLIVAR program. It is expected that CLIVAR can only accomplish its objectives in cooperation with other national and international climate rese arch programs, especially IGBP, GEWEX, WOCE and ACSYS as well as coordination with the monitoring programs, GCOS and GOOS.

Arnold Gordon
CLIVAR SSG Chair
Lamont-Doherty Earth Observatory
Palisades, New York 10964

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