The Indian subcontinent has seen greater extremes in rainfall during the South Asian summer monsoon season over the past 30 years than before 1980.

Nearly 20% of the world's population is affected by this monsoon, which brings most of India's annual rainfall. Deepti Singh and her colleagues at Stanford University in California compared precipitation data during wet and dry spells in two time periods, 1951–80 and 1981–2011.

Statistical analyses revealed that wet spells have grown more intense during the recent period, and that dry spells have become more frequent. The authors also found increased variability in daily rainfall over the past half-century, and an overall drop in peak-season precipitation.

These changes were associated with shifts in atmospheric circulation patterns and increased moisture availability. The more intense wet spells increase the risk of floods and the more frequent dry spells could negatively affect agriculture, the authors say.

Nature Clim. Change http://dx.doi.org/10.1038/nclimate2208 (2014)