This article titled Indian Monsoon Cycles Through The Last Twelve Million Years written by Shyam Murti Gupta appears in Earth Science Dta eJournal for October 2010. He writes:
Although Indian monsoon mostly sets on in early June, it often deceives
us with droughts or floods causing hardship to millions in the Indian
subcontinent. Numerous physical forcing affect the monsoon at the same
time and their linear/non-linear responses are mostly cyclic in nature at
the intra-monsoonal, yearly, decadal, century to millennial scales in the
last 12 million years. However, they are not yet fully understood and
assimilated in the predictive models with high reliability at weekly level,
enabling farmers to plan their crops in better way. With such advance
knowledge, when monsoon casts flood/drought, it makes us to realize
that we do not know for sure, that how would be the next monsoon
within the reasonable uncertainties.
The article deals with long historical records and relates them to Milankovitch and other solar system fluctuations and so examines cycles from several years to several million years.