Evidence for solar forcing on the Indian monsoon during the last millennium

Solar influence on the intensity of the Indian monsoon is demonstrated using a sediment core from the eastern Arabian Sea dating back to 1200 yr, through pattern matching as well as spectral analysis of proxy records of monsoon and solar activity. The intensity of the Indian monsoon is found to have decreased during periods of solar minima during the last millennium. Periodicities of 200±20, 105±15 and 60±10 yr are observed in the proxy records coinciding with those known for solar cycles. The ∼60-yr periodicity observed in the instrumental rainfall data appears to be of solar origin and supports the hypothesis of solar control on the Indian monsoon on a multi-decadal time scale. Evidence for the presence of a coupled atmospheric forcing for the Indian and East African monsoons on a centennial time scale is also seen.