Near Future Projection of Indian Summer Monsoon Circulation under 1.5 °C and 2.0 °C Warming

Abstract

The Indian summer monsoon’s (ISM) response to low (1.5 °C) and medium (2.0 °C) warming scenarios are examined during the period 2021–2050 using 11 member ensembles of the state-of-the-art Community Earth System Model, version 1 (CESM1-CAM5) datasets. We find that in the near-term period an increase in warming by 0.5 °C will strengthen the monsoon circulation and precipitation over the Indian landmass and east Asia. Under the 1.5 °C warming scenario, the ISM circulation will weaken, and precipitation will exhibit a decreasing trend, while the ISM precipitation and circulation will strengthen under the 2.0 °C warming scenario. The strengthening of ISM under the 2.0 °C warming scenario is due to the strengthening of the South China Sea (SCS) anticyclone and a high-pressure center near the Philippine Island. This high-pressure center over the SCS will facilitate a cross-basin strengthening of the easterly wind from the western Pacific Ocean/SCS to the equatorial Indian Ocean, which will, in turn, strengthen the transport of the Pacific-origin moisture to the Indian subcontinent and East Asia. This increase in moisture content over the Indian subcontinent will strengthen the monsoonal circulation and precipitation under the 2.0 °C warming scenario.