Abstrakt:
A detailed analysis of the spatial and temporal changes in mean seasonal and annual daily maximum (Tmax) and minimum (Tmin) air temperatures and diurnal temperature range (DTR) in the Arctic over the period 1951–1990 is presented. This analysis is preceded by a description of the spatial distributions of the mean seasonal and annual 40-year extreme temperatures (i.e. Tmax and Tmin).
The rate of decrease of the mean Arctic Tmin is about twice as weak as the rate for Tmax in the period 1951–1990. As a result, a decrease in DTR is observed. Not all areas of the Arctic, however, show such tendency, e.g. large parts of the Canadian Arctic do not. The increases in DTR here are more common in summer than in winter.
The decrease in DTR is related partly to increases in cloud cover, especially in the warm half-year when solar radiation is present in the Arctic. On the contrary, in the cool half-year (mainly during polar night) the day-to-day changes of temperature, governed at this time by very variable atmospheric circulation, have a greater impact than the cloudiness.
The increase in variability of Tmax and Tmin has not occurred in the most recent decades.
No evidence of any greenhouse warming in the Arctic over the period 1951–1990 is seen. Most of the Tmax and Tmin trends are not statistically significant.
