Thanks to the assessments by the IPCC, the world recognizes that humans are contributing to a global climate change that is among the most important threats we face. The climate science community now taces a majornew challenge ofproviding society with reliable regional climate predictions. Adapting to climate change while pursuing sustainable development will require accurate and reliable predictions ot changes in regional weather systems, especially extremes. Investments ot trillions of dollars worldwide may be necessary to avoid the worst consequences of climate change. Yet, current climate models have serious limitations in simulating regional weather variations and therefore in generating the requisite information about regional changes with a level of confidence required by society. Use of high-resoluti on regional models to downscale regional climate change is questionable if the global models from which lateral boundary conditions are prescribed are not realistic. In short, the limitations of current modeling methods are forcing the climate