TOGA was a ten year programme to advance understanding between the atmosphere and ocean which influence climate over interannual time-scales. During its lifetime, a major observational system for the tropical Pacific Ocean was established, with measurements of surface air temperature, surface wind, sea surface temperature, upper ocean thermal structure, ocean currents and sea level being taken on a regular basis, and with trial deployments of instruments to measure surface pressure, rainfall and salinity under way. Armed with these data, oceanographers and meteorologists not only can analyse the present state of the ocean and atmosphere but even can predict climate change for several months ahead. Before TOGA, ideas of tropical atmosphere-ocean interaction were hazy. Ten years on, still no complete theory exists, but considerable progress has been made in modelling and in understanding some aspects of that interaction. In particular the largest climate signal on interannual time-scales, El Nino Southern Oscillation (ENSO), with its origins in the tropical Pacific is much better understood. TOGA also established a minimum observing system in the Atlantic and Indian Oceans. There are both interannual and decadal signals in these oceans which are related to climate variability, but the full role of these oceans in climate variability has yet to be clarified. The primary heat source for the atmosphere is located over the 'warm pool' of the western tropical Pacific. A major experiment, the coupled ocean atmosphere response experiment (COARE) was mounted to understand in some detail oceanic and atmospheric processes occurring in this region. It is not known how the tropical interaction processes such as ENSO will alter as a result of anthropogenic increase in the radiatively active gases carbon dioxide, methane and sulphur dioxide, but there is a hint that some of the global warming of the last decade may have an ENSO connection.
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