Spatial and Temporal Distribution of Air Temperature in the Northern Hemisphere

In the present study, the spatial and temporal surface air temperature variability for the Northern
Hemisphere has been examined, for the period 1900-1996. Factor Analysis has been applied to 5o
Latitude x 10o Longitude grid box data covering the area from almost the equator to 70o N. These data
are anomalies of the mean annual air temperature from the respective mean values of the period 1961-
1990.
The analysis showed that, mainly 20 regions were determined in the Northern Hemisphere with
significantly covariant air temperature time series. The comparison of the trends of the mean annual
surface air temperature time series of these regions, revealed such common characteristics as the
minimum of the first decade of the 20th century and the recent years warming. The results of this study
are also compared to the respective results of a former study in which data for the last half of the
century (1948-1996) have been analyzed. The findings extracted indicate the stability of climate
distribution in Northern Hemisphere during the 20th century.