Climate Through The Ages

Text extracted from opening pages of book: CLIMATE THROUGH THE AGES A STUDY OF THE CLIMATIC FACTORS AND THEIR VARIATIONS By C. E. P. BROOKS I. S. O., D. Sc., F. R. Met. Soc. ERNEST BENN LIMITED LONDON First published 1926 Revised edition 1949 Second impression 1950 PUBLISHED IN GREAT BRITAIN BY ERNEST BENN LIMITED, LONDON PRINTED IN GREAT BRITAIN BY HHADLEY BROTHERS IOQ KINGSWAY, LONDON, W. C. 2J AND ASH FORD, KENT PREFACE TO THE FIRST EDITION SOME years ago I had the privilege of laying before the public The Evolution of Climate. As its title implies, that book mainly consists of an account of the variations of climate during geological times, and it deals especially with the Quaternary Ice-Age and the Post-glacial period. The causes of the events described were touched on only very briefly, and chiefly for the purpose of emphasising the climatic importance of the period of continental emergence which intervened between the mild - climates of the Mesozoic and Tertiary periods and the beginnings of the Ice-Age. It was my intention then to write a companion volume dealing with the mechanism of climatic changes and drawing on the first volume for illustrations. But there were many problems requiring further investigation and much reading to be done before such a work could be approached with any confidence, and so for several years desire outran performance. Then came the work of Wegener on the theory of continental drift, and of Koppen and Wegener on the interpretation of the climatic record in terms of the travels of the continents across the parallels of latitude, and this stimulated me to complete the investigation in order to examine Wegener's theory from the climatic side. Climatethrough the Ages has not been altogether easy writing; the present is the key to the past, but there have been many strange meteorological situations for which we have no present parallel to guide us. Moreover, the meteorology of the present has still to solve many problems of its own, and I am even encouraged to hope that the meteorology of the past may at times help in the study of the present. The theory of the circulation of the earth's atmosphere, for instance, is not yet complete, and it may be that the modifications of the circulation during the varied climatic history of the globe, as deduced from the distribution of rainfall and temperature, will provide just the additional material required for a solution.* PREFACE The point of view being meteorological, it has not been considered necessary to keep to a strict chronological order in discussing the climates of different geological periods, as was done in The Evolution of Climate. For convenience* of reference, a list of the geological periods, with some idea of their duration and a brief note on the general type of climate, has been given in Appendix I. For the purposes of the discussion, geological climates are classed as warm or glacial. We are living now in a glacial period, though fortunately not at its maximum, and the meteorological conditions during the Quaternary Ice-Age are not really strange to us. The warm periods, in which a genial climate extended almost or quite to the poles, are meteoro logically much more remote. In the best developed warm periods it is probable that ice was unknown. This approach to uniformity of temperature was inevitably associated with very great changes in the winds, the ocean currents, andthe distribution of rainfall. The way in which this situation came about was not simple, and I have thought it best to open the book by setting out, in an Introduction, the geological evidence as to the existence and nature of these warm periods, and especially the extent to which climatic zones were developed. This greatly simplifies the subsequent meteorological discussion by allowing us to take the main facts for granted and to consider the variation of the individual factors of climate one by one, until the ground has been prepared for a more complete and log