ABSTRACT
Along with the gravitational influences of crustal and eustatic changes (see chapters 1 and 3), a combination of climatic changes, dominated by solar energy, was to underlie much geomorphic thinking between the latter part of the nineteenth century and the middle of the twentieth. Chapter 12 of the present volume deals with the broad influences of climate on landforms (i.e. the study of morphogenetic landforms) and, specifically, the effects of former palaeoclimates and climatic changes on previous, now fossil, landforms (i.e. the study of climato-genetic landforms). It is the purpose of the present chapter to take up where volume 1 left off in the middle of the nineteenth century and to sketch the ways in which our understanding of the history of world climates developed during the ensuing century, so as to form a basis for the appreciation of the importance of past and present exogenetic processes in geomorphology. The study of past climates is complicated not only by possible variations in the emission of solar radiation but also by global influences which may have altered the relative receipt of solar radiation upon different parts of the earth, as well as by geographical changes which may have altered the absolute and relative positions of landmasses through geological time, the elevations and relief of continents, the disposition of ocean currents and many other factors having a profound influence on the regional climates of the globe. At the same time it must be remarked that our understanding of the nature and mechanisms of present world climates was revolutionized between the mid-nineteenth and the mid-twentieth centuries, such that accurate descriptions of the climates of the tropics were not available until the latter time.
