Early treatments of global climate and its regional anomalies were limited to attempts to generalize the observed climatic features. The studies of W. Köppen (1931) based on temperature and precipitation classes sought to identify the hypothetical climate of an ideal continent, for example, but this approach was limited by the unavoidable inclusion of the large-scale effects of land-sea distribution and of major mountain barriers on the atmospheric circulation. In a review of G.T. Trewartha’s (1961) book The Earth’s Problem Climates, Tucker (1962) commented that adequate explanations of “normal” climatic patterns on the continents are for the most part lacking. This underlying framework is perhaps more problematic than the so-called anomalies. Climate modeling studies have clarified considerably the determinants of the background planetary climate, the contributory role of the Earth’s geography, and the feedbacks internal to the climate system. These are discussed in turn.