SUN, CLIMATE, HUNGER, AND MASS MIGRATION

Paleoclimatic studies indicate four epochs of global cooling during th e last 4 000 years, i.e, during the few centuries before and after 200 0 BC, 800 BC, 400 AD, and 1 600 AD; the quasiperiodicity corresponds t o cyclic variation of solar activity. Global temperature changes influ enced regional precipitation patterns: Northern Europe was wetter whil e the middle- and low-latitude lands were more aria during colder epoc hs. Both sets of cold climatical conditions were unfavorable for agric ultural production. Historical records show that large demographic mov ements in history took place because of crop failures and mass starvat ion, rather than escaping from war zones. The ''wandering'' of the Ger manic tribes during the first two or three centuries of the Christian Era is one example. Whereas the accelerated release of carbon dioxide from the burning of fossil fuels is ultimately to cause global warming , historical evidence indicates, however, that global warming has been on the whole a blessing to mankind. Global cooling, on the other hand , has curtailed agricultural production and has led to famines and mas s migrations of people. Perhaps the most important task at the present is not so much computer-modelling of greenhouse effect on global clim ate, but water-management and agricultural researches to insure food-s upply for an everincreasing world population.