Increase in Population Exposure Due to Dry and Wet Extremes in India Under a Warming Climate

Dry and wet extremes affect agricultural production, infrastructure, and socioeconomic well-being of about 1.4 billion people in India. Despite the profound implications of dry and wet extremes, their changes in the observed and projected climate in India are not well quantified. Here, using the observations from multiple sources, we show that the area affected by dry extremes during the monsoon season (June-September) and water-year (June-May) has significantly increased (similar to 1% per decade; p value < 0.05) over the last six decades (1951-2015) in India. On the other hand, the area affected by wet extremes does not exhibit any significant trend over the same time period. Dry and wet extremes in the monsoon season are corroborated with the positive phase and negative phase of the sea surface temperature (SST) anomalies in the tropical Pacific Ocean (Nino 3.4 region). Global climate models (GCMs) project an increase of more than 25-30% (+/- 3-6%) in the combined area affected by the dry and wet extremes in India by the end of the 21st century. The frequency of both dry and wet extreme years is also projected to increase in the majority of India (>80%) under a warmer world if the global mean temperature rises above 1.5 degrees C (or 2 degrees C) from a preindustrial level. Moreover, the population exposed to the dry and wet extremes is likely to increase threefold under the projected 2 degrees C warmer world. Therefore, limiting global mean temperature rise below 2 degrees C can substantially reduce the area and population exposure due to dry and wet extremes in India.