Observed changes in temperature and precipitation extremes for the latter half of the 20th century generally show increases in warm temperature extremes, decreases in cold extremes, and increases in heavy precipitation events (Alexander et al. 2006). Here we use daily values from a general circulation model simulation for the 20th century using observed greenhouse gas and other forcings produced for the IPCC Fourth Assessment Report and the definition of extremes found in Alexander et al. (2006) to compare how changes in the model-produced extremes compare to the changes in observed extremes. The model used is the NOAA Geophysical Fluid Dynamics Climate Model 2.1. We also examine how these temperature and precipitation extremes change in simulations produced using two 21st century forcing scenarios.