The natural environment differs in various parts of the earth. But what determines whether a particular region would be grassland or a desert or a lush green forest? The answer is – differences in the climate of these regions. Climate is a critical factor in soil formation, food production and energy demand of any geographical region. Climatic variations can have profound effects on the environment and thus on humankind. To assess the effects of these variations we must first have some understanding or the factors that constitute climate. The earth is a mosaic of many types of climates and a variety of controls interact to shape the climate of any region. The controls that exert a regular and predictable influence on climate are latitude, altitude and proximity to large water bodies. In addition, the climate is strongly influenced by circulation pattern of the atmosphere and ocean currents. Circulation determines the types of air masses that regularly develop over a region or move across it from other regions. This affects the rainfall, while ocean currents affect the climate of large landmasses.