Researchers from the Indian Institute of Science, Bangalore; Indian Institute of Tropical Meteorology, Pune; and Florida State University, USA; have mathematically computed a multidecadal variability in the Indian summer monsoon rainfall and the global sea surface temperature. They have established that Indian monsoon rainfall exhibits a 67-year oscillation and is closely linked to the sea surface temperature cycle, which also shows a similar 67-year swing. The study also shows that 80% of all droughts have occurred in the rainfall cycle’s ‘negative phase’, associated with a below-average rainfall; whereas 60% of all floods have occurred in the positive phase, marked with above-average precipitation. Their findings have been published in the Quarterly Journal of the Royal Meteorological Society.

The Indian monsoon, which sees much variability, has been crucial to the country's economy. It affects 42% of employed individuals in the country — farmers and those working in the agricultural sector. At times, a 'normal' monsoon brings enough rain to keep everyone happy, but sometimes, there is either a deluge or a drought. With recent meteorological advances, these variations can be predicted and recorded. But, how do we go back hundreds of years in time to understand the historical variability in Indian monsoon? Corals in the Red Sea may have answers, says a study by American researchers.