Abstract
Studies which utilize a long-term temperature record in determining the possibility of a global warming have led to conflicting results. We suggest that a time-series evaluation of mean annual temperatures is not sufficiently robust to determine the existence of a long-term warming. We propose the utilization of an air mass-based synoptic climatological approach, as it is possible that local changes within particular air masses have been obscured by the gross scale of temperature time-series evaluations used in previous studies of this type. An automated synoptic index was constructed for the winter months in four western North American Arctic locations to determine if the frequency of occurrence of the coldest and mildest air masses has changed and if the physical character of these air masses has shown signs of modification over the past 40 years. It appears that the frequencies of the majority of the coldest air masses have tended to decrease, while those of the warmest air masses have increased. In addition, the very coldest air masses at each site have warmed between 1°C to almost 4°C over the same time interval. A technique is suggested to determine whether these changes are possibly attributable to anthropogenic influences.
