ABSTRACT
Palaeoclimatic studies help us to gain valuable perspectives and insights into the nature and possible origins of present-day climatic variations that are beyond the reach of instrumental weather observations and allow us to view the relatively short instrumental record in the context of longer-timescale variability. In view of the growing concern over a CO2 enhanced greenhouse effect, there is an urgent need to verify this anthropogenic signal projected by climate models as early as possible, by means of observational statistics (Schönwiese, 1990). This implies a better understanding of natural climatic variability and forcing on two fundamental timescales: decadal and secular. On the decadal timescale, there are natural climatic fluctuations that centrally involve air-sea-ice interactions, solar and volcanic forcing, as well as man-induced changes to the atmosphere and to the land surface. On the century timescale substantial global warming is likely to occur due to the cumulative effects of anthropogenic forcing (Stocker and Mysak, 1992). It is well known that the primary impacts of climate on society result from extreme events on short timescales from hours to years, such as storms, floods, killing frosts, heat and cold waves, and droughts, rather than from changes in the mean climate, and that the sensitivity is relatively greater the more extreme the event (Kates et al., 1985). Therefore, palaeoclimatic studies should also examine how changes in the frequency and severity of extreme events are related to changes in average conditions (Mitchell et al., 1990).
