Abstract
It has been suggested that previous results indicating an increase in surface temperatures over the past 40 years within the coldest air masses at four stations in the western North American Arctic may be attributed to the shorter residence lime of these air masses through the time period. If true, this contradicts the original contention that these air masses have undergone physical character changes, possibly attributed to anthropogenic sources, during the period. A reevaluation of the data at two of these stations indicates that a long-term warming is, in fact, taking place even when residence time is kept constant. Thus, it is suggested that changes in the physical character of these very cold air masses are due to factors other than residence time.
