What was done
The authors analyzed the relationship between four solar indices (sunspot number index, group sunspot number, solar irradiance and sunspot area) and seven regional Indian monsoon rainfall time series (northeast India, northwest India, central northeast India, west central India, peninsular India, a so-called homogeneous Indian monsoon region, and an overall time series called the all India summer monsoon) over two distinct periods of low and high solar activity, each comprising three complete solar cycles, between 1871 and 1990.

What was learned
The results of the authors' statistical analyses led them to conclude that greater Indian monsoon rainfall was associated with greater solar activity.  In addition, wavelet analysis revealed "striking similarity" between coefficient maxima in the 8- to 16-year band of the precipitation and solar series, suggesting a strong link between Indian monsoon rainfall and solar activity over the 11-year solar cycle.

What it means
The results of this study reveal the existence of a strong correlative connection between solar activity and Indian monsoon rainfall, albeit a casual relationship describing how the former phenomenon may modulate the latter has yet to be established.  Nevertheless, the potential role of the sun on earth's climate would appear from this study to be of great importance, suggesting that it must be understood and accurately accounted for when attempting to separate natural and anthropogenic components of climate change.  The need to meet this requirement is especially important for the recent past, which has seen large increases in the time series of these solar indices since 1880.  It just may be that when all of these intriguing relationships are finally understood, the sun may be found to bear the largest climate fingerprint of all!