CLIMATE AND THE DISTRIBUTION OF MARINE ANIMALS 



295 



trend in minimji lias been upward since about tlie 

 first third of the 19th century. 



Annual means may not indicate all of the 

 significant changes that may be occurring in an 

 area. Mild winters and cool summers may, for 

 example, result in tlic same annual means as 

 severe winters and very warm summers— the 

 climate in the two situations being quite different. 



In figures 2 and 3, curves for January and July 

 deviations from their respective means are shown 



for New Haven for the period 1780-1953. The 

 curves are smoothed by 15-year moving averages. 

 The January temperature deviations show a pro- 

 nounced trend from a low in the 1810's. The 

 mean for the period 1780-1900 is 26.72° F., while 

 that for the period 1901-53 is 29.66°, a difference 

 of nearly 3°. The mean since 1930 is 30.57°, an 

 increase of 3.85°, even tliough the trend was gen- 

 erally downward over the latter part of this period. 

 It will be observed, on the other hand, that aside 



> 



UJ 



laio 



1830 



1930 



1850 1870 



YEAR 



Figure 1. — Annual deviations from the mean air temperature, 1781 to 1950, at New Haven, Conn. The solid line is 



a 5-year moving average. 



1790 1810 1830 1880 1870 1890 1910 1930 



YEAR 



Fkure 2. — January air temperature deviations from the mean, 1780 to 1953, at New Haven, Conn. (Curve smoothed by 



15-year moving average.) 



