Major scientific and technical discoveries are often followed by the creation of institutions that can take advantage of those discoveries for the betterment of society. Advances in our understanding of atmospheric dynamics, accompanied by the technological breakthrough of fast automatic computing devices led to the rapid development of numerical weather prediction, a capability that has been institutionalized by many governments around the world, for example NCEP (USA) and ECMWF (UK). A second example is the development of our scientific understanding of the potential for predictability at seasonal time scales in the midst of chaos. The application of that capability for seasonal climate prediction led to the creation of organizations like IRI (USA). Now we have before us, thanks to IPCC, a new major discovery: humans are affecting the Earth’s climate. This talk will describe the scientific and institutional challenges in producing accurate, reliable and quantitative predictions of regional variations in a changing climate for science based adaptation strategies.

It is argued that because of the complexity of the climate system, and because the regional manifestations of climate change are mainly through changes in the statistics of regional weather variations, the scientific and computational requirements to predict its behavior reliably are so enormous that the nations of the world should make the dual commitments of enhancing their national climate modeling efforts, and creating a small number of multi-national research and high performance computing facilities dedicated to the grand challenges of predicting climate change on both global and regional scales over the coming decades.

Motivated by the success of internationally-funded infrastructure in other areas of science, the paper recommends that a small number of highly connected multi-national facilities should have computer capability at each facility of about 20 petaflop in the near future and about 200 petaflop by the end of the next decade. Such facilities will enable future IPCC assessments to be made using about 10 km resolution climate models, and dynamical seasonal predictions using 3-5 km cloud system resolving atmosphere models and eddy revolving ocean models. This will also enable weather-climate modeling and prediction research using about 1 km resolution atmosphere models and about 5 km ocean models. Each facility should have enabling infrastructure including hardware, software and data analysis support, and scientific capacity to interact with the national centers and other visitors to the facility. Such facilities will play a key role in the development of next generation climate models, build global capacity, nurture a highly trained workforce, and engage the global user community, policymakers and stakeholders.