This is a second edition of the book, revised and enlarged. It is a difficult and complex task to express our present conception of climate during the geological history of the earth for this includes an understanding of the means which have been available, the aims which have been pursued and the results obtained.
M. Schwarzbach, Professor of Geology at the University of Cologne, has accomplished this task admirably by reason of his mastery of the subject, his critical alertness and his clarity of expression.
This is not a popular book since it is intended for students at Universities. The ice ages play an important part in his account, because definite traces of these are more unmistakable with regard to their climatological evidence than other geological features.
The first part of the book deals with the principal climatological, oceanographical and general physical conditions which have to be considered. This is followed by an instructive account of the evidence we have today of hot, cold, dry and humid climates, of air-pressures, weather and seasons, as well as longer climatic changes. Schwarzbach then goes on to cite the palaeontological topography and stratigraphy as well as the flora and fauna then existing—evidence not only of the author’s wide reading, but also of his extensive personal knowledge.
The book next deals with climatic conditions and change, the greatest attention being paid to the ice ages for the reason already mentioned. This is scarcely a question of glaciology, but for all those who are interested in presentday ice caps and local glaciers, or in former ice ages, this summary is of great value. The perspective is thus broadened, and this provides a better understanding of both present-day and past issues.
Supported by the time-determinations introduced by H. C. Urey with his 18O/16O method, Schwarzbach considers that the oldest ice age in South Africa is about a thousand million years old, in North America probably even older. After that the ice ages stand out as milestones along the long road of development of the earth. Of the three most definite periods, the first occurred in pre-Cambrian time about 500–600 million years ago, and the second, during the Carboniferous period, about 325 million years later. The beginning of the latest Quaternary Ice Age is estimated at about 1 million years before the start of our chronology and is supposed to have finished, climatologically speaking, 15,000 years ago. It is necessary, however, to remember that it took about another 10,000 years until the North European inland ice had melted away in the Scandinavian mountains.
The latest Ice Age is surely of particular interest because “it is most intimately connected with the origin and development of Man”, as Schwarzbach expresses it. He considers that the present conditions are a phase of this Ice Age—a reasonable interpretation, taking into account the vastness of the present ice masses in the polar regions in comparison with past geological epochs.
Schwarzbach has not been able to include the latest very significant results of the Atlantic deep-sea sediment cores (Reference EricsonEricson and others, 1961), which have further confirmed the important part played by the investigations of these sediments for an understanding of the history of climate. Attention must also be paid to a recently published preliminary report by Reference ManleyManley (1961) of the weather conditions in the London area during the period 1680–1715. This shows that the climate up to the present has not been so favourable for the glaciers as it was around 1700. Since the glaciers in the Alps, in Iceland as in the Scandinavian peninsula during the first half of this century had a maximum extension obviously a causal connection exists. The conclusion can probably also be drawn that the glaciers during the latest thousand years in Europe have not had more favourable conditions than in about the year 1700.
The actual problem of the reasons both for the ice ages and the other climatic changes are treated in the third part of the book. No fewer than 50 theories have been advanced; discussions were liveliest during the turn of the last century when half of these were published. The presentation is as clear and instructive here as in the other parts. The author’s own opinion on this problem is that the changes in climate have mainly been caused by a combination of changes in solar radiation and continental topography. To the oldest epochs are added both the changes in the earth’s axis and continental drift. The latter is mainly applied to the change between the Carboniferous and the Permian periods, when Gondwanaland is said to have existed, covered with ice in different parts.
Finally what can be expected in the future? Is the earth at present in a milder period between the latest glacial period and a future one? Schwarzbach does not say much more about that problem than: Qui vivra, verra—provided that we survive the present time.
