Secular change in the variability of temperature

The mean temperatures for January, April, summer and October at New Haven, Connecticut, for 1781-1970 were analyzed for evidence of a secular change in several indices of variability. The January-July difference decreased significantly. Although the standard deviation (SD) of the summer temperature within decades decreased significantly, the SDs of January, April, and October did not, and none of the SDs were correlated with means. The SD about trends within decades was not correlated with the magnitude of the trends except in April. There was no significant trend in the January-to-January persistence during the 19 decades.