Increase in Subdaily Precipitation Extremes in India Under 1.5 and 2.0 °C Warming Worlds

An increase in short duration precipitation extremes poses challenges for storm water design in rapidly urbanizing India. The recent Paris Agreement aims to limit the global mean temperature (GMT) below 1.5 degrees C (and possibly below 2.0 degrees C) from the preindustrial level. However, the changes in subdaily precipitation extremes in India remain unrecognized under the 1.5- and 2.0-degrees C temperature targets. Here using observations and projections of the subdaily precipitation, we show that a majority (11 out of 15) of General Circulation Models underestimate 3-hourly precipitation extremes and overestimate the relationship between 3-hourly precipitation extremes and GMT (scaling) in India. A rise of 1.5 (2.0 degrees C) in GMT from the preindustrial level is projected to cause 20% (25%) increase in 3-hourly precipitation maxima at 100-year return period under the stationary condition, which can further rise by 10% under the nonstationary condition. Projected warming results in a much faster (almost twice) increase in 3-hourly precipitation maxima than 24-hourly 100-year precipitation maxima. Moreover, 3-hourly 100-year precipitation maxima are projected to increase significantly at 78 locations (out of 89) if GMT increases from 1.5 to 2.0 degrees C from the preindustrial level. Our findings have implications for urban storm water designs in India.