Using the highest performance supercomputers available, the Department of Energy plans to build the most complete Earth climate model ever constructed. Eight DOE laboratories are teaming up with academic and private research centers and the National Center for Atmospheric Research on the project, called Accelerated Climate Modeling for Energy (ACME). Over the next decade, ACME’s goal is to use those computers, as they become available, for their models, eventually including exascale supercomputers. The project’s first experiments will run on computers at Oak Ridge and Argonne National Laboratories. The model will initially focus on simulating three important drivers of climate change: the water cycle, biogeochemistry, and the cryosphere. The water cycle work will examine changes in river flow and their impact on greenhouse gas emissions. The biogeochemistry models will investigate how nutrient cycles affect the carbon-climate system. And efforts involving the cryosphere will study the risks of climate instability due to rapid melting, including the possible collapse of the Antarctic ice sheet.