The reality of climate change has been accepted by the world. Thanks to the sustained, comprehensive and objective assessments by the Intergovernmental Panel on Climate Change (IPCC), a consensus, with a high degree of confidence, has emerged in the scientific community that human activities are contributing to climate change. A systematic program of numerical experimentation with climate models during the past 40 years has played a crucial role in creating this scientific consensus, and in its acceptance by the world.

The nations of the world have therefore begun, with great urgency, discussion about mitigation and adaptation to climate change, the inevitability of which is now beyond doubt. The climate models will, as in the past, play an important, and perhaps central, role in guiding the trillion dollar decisions that the peoples, governments and industries of the world will be making to cope with the consequences of changing climate.

The climate modeling community is therefore faced with a major new challenge: Is the current generation of climate models adequate to provide societies with accurate and reliable predictions of regional climate change, including the statistics of extreme events and high impact weather, which are required for global and local adaptation strategies? It is in this context that the World Climate Research Program (WCRP) and the World Weather Research Programme (WWRP) asked the WCRP Modelling Panel (WMP) and a small group of scientists to review the current state of modelling, and to suggest a strategy for seamless prediction of weather and climate from days to centuries for the benefit of and value to society.

A major conclusion of the group was that regional projections from the current generation of climate models were sufficiently uncertain to compromise this goal of providing society with reliable predictions of regional climate change. Therefore, a major recommendation by the group was that, to meet the expectations of society, it is both necessary and possible to revolutionize climate prediction. It is necessary because adaptation strategies require more accurate and reliable predictions of regional weather and climate extreme events than are possible with the current generation of climate models. It is possible firstly because of major advances in scientific understanding, secondly because of the development of seamless prediction systems which unify weather and climate prediction, thus bringing the insights and constraints of weather prediction into the climate change arena, and thirdly because of the ever-expanding power of computers.

Climate models are also useful tools for analyzing observations in a consistent physical framework. Analysis and prediction from past observations helps in interpreting the observed historical changes in the climate system and develop confidence in projections of future change.

The group further declared that the scientific expertise to realize this revolution resides in no single nation or scientific discipline, and therefore, a strong collaboration among the nations and among disciplines is required.

Realizing the profound and far-reaching implications of these suggestions, the WCRP, WWRP, and the International Geosphere Biosphere Program (IGBP) decided to organize a World Modelling Summit for Climate Prediction. It is expected that the Summit will provide valuable input to the World Climate Conference 3. The primary emphasis of the summit will be on simulating and predicting the physical climate system. Since the prediction of regional climate change is strongly influenced both by weather fluctuations on short time scales and bio-geo-chemical processes on long-time scales, the summit includes important elements of the WWRP and the IGBP.

The underlying goal of the summit is no less than to prepare a blueprint to launch a revolution in climate prediction.

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