to denote climatic types as given above. Each type is further sub-divided into sub-types on the basis of seasonal variations in the distributional pattern of rainfall and temperature. He used S for semi-arid and W for arid and the following small letters to define sub-types: f (sufficient precipitation), m (rain forest despite a dry monsoon season), w (dry season in winter), h (dry and hot), c (less than four months with mean temperature over °C), and g (Gangetic plain). Accordingly, India can be divided into eight climatic regions (Table .
; Figure . ). Monsoons and the Economic Life in India (i) Monsoon is that axis around which revolves the entire agricultural cycle of India. It is because about per cent people of India depend on agriculture for their livelihood and agriculture itself is based on southwest monsoon.
(ii) Except Himalayas all the parts of the country have temperature above the threashold level to grow the crops or plants throughout the year.. (iii) Regional variations in monsoon climate help in growing various types of crops. (iv) Variability of rainfall brings droughts or floods every year in some parts of the country. (v) Agricultural prosperity of India depends very much on timely and adequately distributed rainfall.
If it fails, agriculture is adversely affected particularly in those regions where means of irrigation are not developed. (vi) Sudden monsoon burst creates problem of soil erosion over large areas in India. (vii) Winter rainfall by temperate cyclones in north India is highly beneficial for rabi crops. (viii) Regional climatic variation in India is reflected in the vast variety of food, clothes and house types.
G LOBAL W ARMING You know that change is the law of nature. Climate has also witnessed change in the past at the global as well as at local levels. It is changing even now but the change is imperceptible. A number of geological evidences suggest that once upon a time, (see geological time scale in Chapter of Fundamentals of Physical Geography, NCERT, ) large part of the earth was under ice cover.
Now you might have read or heard