Future climate change at local and regional scales will result from a combination of human and natural factors. In this talk, I show that unpredictable, internally-generated climate fluctuations make a substantial contribution to climate trends projected for the next fifty years over North America. My results are based on large ensembles of climate change integrations with two state-of-the-art coupled climate models. I will also show that the large-scale atmospheric circulation is responsible for much of the diversity in climate change projections across the individual ensemble members. I conclude by discussing some implications of the results for model validation, inter-model comparisons, and interpretation of observed climate trends.