In the Introduction we asked whether the absence of any significant warming could still be observed in the Arctic after 1975. An analysis of the data concerning T up to 1995 (Przybylak 2000a) provided no basis for a negative answer to this question. However, as far as temperature is concerned, the situation in the Arctic has changed significantly, particularly between 1996 and 2000, allowing us to conclude that the so-called second wave of contemporary warming came to the Arctic about twenty years later than to lower latitudes. After many years of the domination of slight changes in T in the Arctic in the last decade, particularly between 1996 and 2000, the rate of increase for mean TA was greater (1.5-2.5 times) than the rate of increase for Tnh (land and ocean) (see Figure 9.4). In the present book, as well as in another work by the same author (Przybylak 2000a), probable reasons for the lack of warming until 1990-1995 have been quoted. Does the significant warming in the period 1996-2000 mean that the factors which have so far caused cooling in the Arctic have weakened or have ceased to act? Such a thesis could be true if, for example, the inertia of the Arctic climatic system lasted about twenty years longer than in the climatic systems in lower latitudes, where there is the lack of a cryosphere to a greater or lesser degree. It is also possible that there was a significant decrease in the anti-greenhouse effect of sulphate aerosol in the Arctic and that it was connected with the decreasing sulphur emissions to the atmosphere in Europe and North America. In the
1990s there was no significant change in atmospheric circulation; similar to the 1980s, there was the predominance of zonal circulation (high values of NAO and AO indices) and thus, it may be concluded that this factor did not cause the sudden warming in the mid-1990s. Therefore, it seems that these changes were instigated by one of the first two factors, or by their mutual action. It also cannot be denied that this sudden warming is a result of interactions within the atmosphere-ocean-cryosphere system.
There was also a significant increase in P in the 1990s. In comparison to the period 1951-1990, the relations between T and P became much clearer. Apart from the Russian Arctic (in which there was only a slight warming in the 1990s and in which no increase in T was observed in the last five years of the said period) usually, an increase/decrease in T was accompanied by a similar increase/decrease in P. However, there are still regions where an increase/ decrease in T is accompanied by a reverse decrease/increase in P, especially when seasonal characteristics are taken into consideration.
It must be concluded that the direction of the changes of T and P in the Arctic occurring in the last decade is much more consistent with model projections of the expected changes in the climate of this region. However, some aspects of the changes in the meteorological elements which have been analysed are inconsistent with these prognoses. It seems that, in the case of T, the reasons for the significantly weaker winter warming in the 1990s should be explained as soon as possible. All climatic models indicate unanimously that, with the concentration of trace gases, the highest warming should occur in polar latitudes in winter (IPCC 1990, 1996, 2002). This discrepancy may be reduced when climatic models consider, in a significant and correct manner, changes in atmospheric circulation. As has been demonstrated by Przybylak (2000a), Rigor et al. (2000) and others, these changes explain as much as about 50% of the changes of T variance in the Arctic, many of them in the cool season. Therefore, it would be worth presenting future changes of atmospheric circulation in climatic models in a variant way, i.e. for several scenarios of changes. Undoubtedly, the consistency between the observed changes in T and P in the Arctic and their model prognoses will improve for one of these scenarios.
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