Page:Popular Science Monthly Volume 69.djvu/462

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.
458
POPULAR SCIENCE MONTHLY

CHANGES OF CLIMATE
By ROBERT DeC. WARD

HARVARD UNIVERSITY

Popular Belief in Climatic Change.—Belief in a change in the climate of one's place of residence, within a few generations, and even within the memory of living men, is widespread. It is confined to no special region or people. It finds support among the most intelligent as well as among the uneducated. Here it may be the view that the climate is growing milder; there, that the winters are becoming more severe; here, that there is increasing aridity; there, that the rainfall is greater. Whenever a season attracts attention because of weather conditions which seem in any way unusual, this belief is strengthened. This popular impression has often found support in the facts of distribution, or the dates of flowering or ripening of certain cereals or fruits. It is asserted that because grapes, or corn, or olives, for example, are now no longer grown in parts of Europe where their cultivation was once an important occupation, we must conclude that the climate has changed from a favorable to an unfavorable one.

Evidences of Climatic Changes within Historical Times.—Evidence is constantly being brought forward of apparent climatic variations of greater or less amount which are now going on. Such reports, largely those of travelers or explorers in little-known regions, are usually based on fluctuations in the extent of inland lakes; on the discovery of abandoned dwelling sites, the ruins of aqueducts and irrigating canals, and the like. Thus we have accounts of a gradual desiccation which seems to have been going on over a large region in Central Asia, during historical times. In eastern Turkestan the lakes have been reported as drying up, Lake Balkash falling one meter in about fifteen years, and Lake Alakul gradually becoming a salt deposit. In his work on Turkestan, Muschketoff gives numerous examples of progressive desiccation, and Bossikoff speaks of the drying up of the lakes on the northern side of the Caucasus. The same thing is reported of lakes in the Pamir. Prince Kropotkin believes that the desiccation of Central Asia in the past drove the inhabitants out on to the lowlands, producing a migration of the lowland peoples and thus bringing on the invasions of Europe during the first centuries of our era. In his recent work on the basin of eastern Persia and Sistan, Huntington believes that, so far as it can be made out, the history of Sistan also