This presentation will provide an overview of the nature of the evidence and status of global climate change.  This evidence will include a review of the instrumental record and a number of proxy data records that provide an indication of how the record of the last century compares to other periods in Earth history.  The presentation will also provide a brief overview of the natural and anthropogenic processes that drive climate change.  How these drivers are linked to current global climate observations will be demonstrated from empirical and simulation studies.  The second half of the talk will focus on recent efforts to include in variety of human activities in global climate models, with an emphasis on how urban systems are simulated in the NCAR Community Climate System Model.  A brief overview of the urban model and the datasets required to drive the model will be provided.