The evolution of Oriental Monsoon is a very complex phenomenon. Still more complex is the issue of climate change. It involves a whole range of climatic conditions which include solar radiation, temperature, pressure, wind, cloud and precipitation in a given period compared to the preceding periods and has a considerable impact on settled ecosystems.

Ample surplus rainwater is available in river basins of India. Any use and exploitation of this surplus rainwater must be based on an analysis of 4 to 10 times longer data of the past.

The analysis of changes in the moisture regions over the past hundred years indicate a net effect of drier all India moisture conditions in the recent decades.

Understanding climatic changes of the Holocene Period (past 11,000 years¬¬¬¬) is crucial to assess the impact of global warming on the Indian environment. In the following discourse we provide an overview of climatic changes over the Indian subcontinent based on instrumental records (1813-2008 AD) and as reported by historians (600 BC-1800 AD), archaeologists (3000–600 BC), mythologists (8,000-3,000 BC) and palaeo-climatologists (prior to 8,000 BC).