Polar regions play a very important role in shaping the global climate. Both empirical and modelling studies show that these are the most sensitive regions to climatic changes. As a consequence, warming and cooling epochs should be significantly more distinct here that in the lower latitudes. Climatic models indicate that they should also occur earlier. However, this is not always the case. It depends on the factor(s) causing the climate change (Przybylak 1996a, 2000a).
The Arctic climate system differs from the other climate systems situated in the lower latitudes firstly because it contains the cryosphere, which is present almost over the whole Arctic. The role of the cryosphere in determining climate is still not fully understood. Thus in March 2000 a new research project, within the World Climate Research Programme, called the Climate and Cryosphere (CL1C) was established (see http:/clic.npolar.no).
Future climatic change which may occur in the Arctic as a result of human activities is difficult to predict (see the next Chapter). This especially concerns its rate and magnitude. However, it is certain that man-made changes in climate will be superimposed on a background of natural climatic variations. Hence, in order to understand future climatic changes, it is necessary to have a knowledge of how and why climates have varied in the past (Bradley and Jones 1993). Therefore of particular relevance are climatic variations of the last 10-11 thousand years (the Holocenc period). The climatic changes which occurred in the past will be presented for three time scales (10-11 - 1 ka BP; 1.0-0.1 ka BP; and 0.1 BP - present). For the first period and for almost the entire second period there are no instrumental meteorological observations, and thus our knowledge is mostly based on the so-called "proxy data". Until recently, the majority of paleoclimatological information has come from geological, geomorphological, and botanical studies. Since the late 1960s a new powerful source of information has been available: the ice-core analyses. For details see, e.g. Bradley (1985, 1999).
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