Two global climate models (HadCM2 and ECHAM) forced with the same greenhouse-gas scenario (IS92a) are found to disagree in their simulated long-term trends of the intensity of the Arctic Oscillation (AO), an atmospheric circulation pattern of the Northern Hemisphere. The simulated AO trends are strongly dependent on the model and on the initial conditions of the simulations. The simulated winter temperature increase averaged over the Northern hemisphere is very similar in both models. However, the effect of the different AO trends on temperature causes clear differences in the predicted regional warming, which are reduced if the effects of the AO is linearly discounted. The uncertainty in the predictions of circulation changes has impacts on the estimation of regional temperature changes. ¿ 2000 American Geophysical Union