The old pollen-analysis based picture of the climatic epoch Sub-Boreal in Europe, 3000 or 2500 to 800 BC, which embraces the second millenium, is in need of a thorough revision in light of the relatively recent researches in the Alps. The researches of concern are glacial-variation studies, mainly of the 1970s, and tree-ring density analyses of the subalpine zone of the late 1970s, reported in 1982. The results indicate that, after a warm and dry epoch ending about 1800 or 1700, a cold period set in in the Alps, lasting to about 1470 BC. (All dates below are BC unless otherwise stated, datings determined by radiocarbon analyses are subject to a maximum possible error of + or - 100 yrs.) This cold phase was followed by an approximately 70 yrs long warm phase. But the most pronounced change occurred about 1400, when rather abruptly a second cold phase was ushered in, continuing until about 1230. This second cold phase is often referred to under the name 'Lobben Phase', which is considered to have been the coldest and longest-sustained cold period of the past 8000 yrs, colder than the recent Little Ice Age of the CE (= Christian Era). Its temperature level is estimated (by G. Patzelt) to have been 0.7 to 1-degrees-C colder than the present level in the Alps. The rise of level of the Swiss lakes, including Lake Constance testify that the Lobben Phase was associated with an enhanced rainfall. In the 13th and the beginning of the 12th centuries major and violent migrations took place from central Europe, including Hungary, and the southeast of the continent toward the south and the southeast, including the Near East as far as the Nile Delta. In order to elucidate if the cold-wet phases of the Alps were cold-wet in central Europe, we have carried out air temperature correlations between an Alpine station Santis (2500 m MSL) and Budapest, for 1921-70. The correlation coefficient is 0.70 for the annual temperatures and 0.82 for July-September of the same years. Since glaciers grow in cold-wet summers, the high correlation for the summer months means that central Europe must have been cold in most of the cold summers of the Alps. But, cold, and especially cold-wet summers are detrimental to agriculture. Presumably, partial or total crop failures must have been relatively frequent in central Europe forcing the people to take to migration. Archeological evidence from Hungary indicates that there were hardly any settlements left, compared with the previous centuries. Finally, we quote evidence to show that some of the groups of the Sea Peoples, who tried to invade the Nile Delta about 1190, were of European origin. They abandoned their 'homeland', presumably because of a turn of the climate to cooler and wetter conditions. It is noted that our interpretation of the causes of migrations of the 13th century and beginning of the 12th, is different from that put forward by Weiss (1982).
