Emerging Trends in Climate Change Impact on the Indian Summer Monsoon Rainfall

The socio-economic impact of climate change on low and medium-income tropical monsoonal countries is disproportionately high even when their historical contributions to greenhouse gas emissions is the least. Here, we address climate change impacts on few aspects of the South Asian Monsoon not adequately addressed in previous studies. The dual impact of the increasing trend of frequency and intensity of daily rainfall extremes and a rapidly increasing trend of frequency and intensity of daily humid heat-stress extremes in recent decades is one such aspect. The two types of extremes occurring in two different phases of monsoon intra-seasonal oscillations contribute to accelerating the socio-economic impacts in the region. India alone accounts for half of the global potential productivity loss due to increased extreme heat stress with ominous implications on the economic growth of the country. One of the two silver linings in the bleak prospects is a westward expansion of Indian monsoon due to the climate change. With the decreasing trend of mean rainfall over Northeast India stabilizing in coming decades, while that over the Northwest India continues to increase, the potential for food production and water resources in the country remains optimistic. The other silver lining is related to the predictability of the seasonal mean climate. We argue that a Global El Niño Southern Oscillation (ENSO) predictor is required to assess the true ENSO-monsoon relationship and unravel that it remains robust with the Indian monsoon remaining highly predictable even in the face of climate change, especially at longer lead times.