Analysis of daily and monthly spatial variance components in historical temperature records

The purpose of this paper is to examine changes in the spatial variance of mean monthly and daily temperatures that may have occurred during the period of historical records. The northern hemispheric lower-tropospheric satellite-based temperature records from 1979 to 1996 and the near-surface air temperature records from either 1947 to 1996 or 1897 to 1996 show relatively consistent temporal patterns with respect to spatial variance. Overall, the spatial variance in temperature anomalies has declined during the period of historical records; the interannual spatial variance levels in temperature anomalies are negatively related to mean hemispheric temperature. Both of these fundamental findings are consistent with model simulations for increasing atmospheric concentrations of greenhouse gases. It is further argued that these findings from the historical temperature records are consistent with a growing body of literature on reductions in cyclone activity in the Northern Hemisphere.