There is now unequivocal evidence for an anthropogenic forcing of climate change. Today our climate system is evolving principally, though not exclusively, as a result of human activities. Changes in the climate system on the global scale will inevitably have consequences that are regionally specific and provide opportunities for research into the impact of these changes. Understanding Climate Change focuses on the Midwestern United States -- a region that contains approximately one-fifth of the nation's population, plays a critical role in national agricultural productivity, and experiences a high frequency of extreme events. Employing observational data and model simulations, the research presented here provides detailed assessments of climate change, variability, and predictability over the past 100 years with predictions for the coming century.