Long-Term Climate Simulations Using the IITM Earth System Model (IITM-ESMv2) With Focus on the South Asian Monsoon

Long-term climate simulations are performed using the IITM Earth System Model version 2 (IITM-ESMv2), a sequel to the earlier version (IITM-ESMv1), to assess climate variability and change with a special focus on the South Asian monsoon. Substantial improvements are incorporated in IITM-ESMv2 to obtain a radiatively balanced global climate modeling framework. The IITM-ESMv2 includes time-varying aerosol forcing and land-use land-cover changes. Multicentury simulations corresponding to preindustrial and present-day conditions show major improvements in capturing key aspects of time-mean atmosphere and ocean large-scale circulation. Representations of the Atlantic Meridional Overturning Circulation and poleward ocean heat transport, and major global climate drivers are superior to ESMv1. Teleconnections of the South Asian monsoon with climate drivers such as the El-Nino-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are found to be more robust in IITM-ESMv2, thus leading to improved simulation of South Asian monsoon and its variability. The IITM-ESMv2 takes a novel pursuit from India to contribute in the Intergovernmental Panel for Climate Change (IPCC) sixth assessment report (AR6). Plain Language Summary This study details the capabilities of the IITM Earth System Model version 2 (IITM-ESMv2), developed at the Indian Institute of Tropical Meteorology, Pune, India, for investigating long-term climate variability and change with special focus on the South Asian monsoon.