The changes in the atmosphere and ocean can be summarized by the NAO Index.  The index is based on the winter difference bewteen the pressure in Iceland and Portugal.
	When looking at the NAO time series, the most striking pattern is the tendency for the NAO to persist in one state or another for several years.  Prior to 1930, the Index was predominantely positive.  During the 50’s and 60’s, the index was negative, but over the last 30 years, the trend has been positive, and some of the highest readings have occurred in the ‘90s.