We report results from the highest-resolution simulations of global warming yet performed with an Atmospheric General Circulation Model. We compare the climatic response to increased greenhouse gases of National Center for Atmospheric Research (NCAR) climate model, CCM3, at T42 and T170 resolutions (horizontal grid spacing of 300 and 75 km respectively). All simulations use prescribed sea surface temperatures (SST). Simulations of the climate of 2100 AD use SSTs based on those from NCAR's coupled model, Climate System Model (CSM). We find that the global climate sensitivity and large scale patterns of climate change are similar at T42 and T170. However, there are important regional scale differences that arise due to better representation of topography and other factors at high resolution. Caution should be exercised in interpreting specific features in our results because we have performed climate simulations using a single atmospheric general circulation model with prescribed sea surface temperatures.