CLIMATE VARIATIONS AND THE ENHANCED GREENHOUSE-EFFECT

Changes in the size of glaciers, in the altitude of the alpine tree-li mit, and variation in the width of tree-rings during the Holocene clea rly indicate that the average Scandinavian summer temperature has fluc tuated. During warm periods it has been about 2 degrees C warmer than at present; during cold periods it has been almost as cold as it was d uring the coldest decades of the previous centuries. Superimposed on t hese long-term variations, which have lasted from 100 to 200 years, ar e short fluctuations in temperature. The Scandinavian chronology, whic h is based on glacier and alpine tree-limit fluctuations as well as on dendrochronology, is well correlated with the changes in climate, whi ch studies of ice cores from central Greenland have revealed. It is th erefore believed that the Scandinavian climate chronology depicts cond itions typical of a large area. The Scandinavian record is compared wi th data concerning solar irradiation variations estimated as C-14 anom alies obtained from tree-rings. A correlation between major changes in climate and variations in solar irradiation points to a solar forcing of the climate. This means that there is no evidence of a human influ ence on climate so far.