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

The socioeconomic impact of climate change on low- and medium-income tropical monsoonal countries is disproportionately high even though their historical contributions to greenhouse gas emissions are the least. Here, we address the climate change impacts on a few aspects of the South Asian monsoon not adequately addressed in previous studies. The dual impact of the increasing trend in the frequency and intensity of daily rainfall extremes and a rapidly increasing trend in the 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 intraseasonal oscillations contribute to accelerating the socioeconomic impacts in the region. India alone accounts for half of the global potential productivity loss due to increased extreme heat stress, with ominous implications for the economic growth of the country. One of two silver linings in the bleak outlook is a westward expansion of the Indian monsoon due to climate change. With the decreasing trend in mean rainfall over Northeast India stabilizing in the coming decades, while that over 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.