Temperature Changes in the Last 100 Years

Abstract

The average annual surface air and free atmosphere temperatures in the northern middle and high latitudes peaked in the late 1930’s and decreased thereafter. This trend was also observed in the eastern Pacific and the North Atlantic. Over the last 40 years the strongest cooling was observed in the northern high latitudes in autumn, but warming was found for July and August. In the low northern latitudes and over most of the Southern Hemisphere insufficient station density prevents a reliable assessment of long terra trends. Secular variations in the extent of snow and ice fields are indirect indicators of climate fluctuations in the high and middle latitudes. Satellite observed winter and spring snow cover in the Northern Hemisphere appears to be more extensive during the late 1970’s than that charted in the late 1960’s. However, recent summer extent of Antarctic sea ice has decreased since 1975.