Abstrakt:
A detailed analysis of the spatial and temporal changes in mean seasonal and annual surface air temperatures over the period of instrumental observations in the Arctic is presented. In addition, the role of atmospheric circulation in controlling the instrumental and decadal-scale changes of air temperature in the Arctic is investigated. Mean monthly temperature and temperature anomalies data from 37 Arctic, 7 sub-Arctic and 30 grid-boxes were used for analysis.
The presented analysis shows that the observed variations in air temperature in the real Arctic (defined on the basis of climatic as opposed to other criteria, e.g. astronomical or botanical) are in many aspects not consistent with the projected climatic changes computed by climatic models for the enhanced greenhouse effect. The highest temperatures since the beginning of instrumental observation occurred clearly in the 1930s and can be attributed to changes in atmospheric circulation. The second phase of contemporary global warming (after 1975) is, at most, weakly marked in the Arctic. For example, the mean rate of warming for the period 1991–1995 was 2–3 times lower in the Arctic than the global average. Temperature levels observed in Greenland in the last 10–20 years are similar to those observed in the 19th century.
Increases of temperature in the Arctic are more significant in the warm half-year than in the cold half-year. This seasonal pattern in temperature change confirms the view that positive feedback mechanisms (e.g. sea-ice–albedo– temperature) as yet play only a small role in enhancing temperature in the Arctic. Hypotheses are presented to explain the lack of warming in the Arctic after 1975.
It is shown that in some parts of the Arctic atmospheric circulation changes, in particular in the cold half-year, can explain up to 10–50% of the temperature variance. For Arctic temperature, the most important factor is a change in the atmospheric circulation over the North Atlantic. The influence of atmospheric circulation change over the Pacific (both in the northern and in the tropical parts) is significantly lower.
