The past climate of the Indian region as seen from the modelling world

Abstract

Proxy-reconstruction studies suggest several waxing and waning epochs of the Indian summer monsoon (ISM) since Last Glacial Maximum (LGM; ≃21 kyr bp). These fluctuations in the ISM are attributed to several internal and external factors. The few available past climate modelling studies for various epochs also support the results from the reconstruction studies for India. Our results, based on an analysis of five CMIP5-PMIP3 simulations for the periods of LGM, Mid-Holocene (MH; ≃6 kyr bp), last-millennium and historical period (ce 1901–1999) indicate that the ISM rainfall was lowest during the LGM, and strongest during the MH. The simulations, relative to the historical time period, suggest highest low-level convergence over the Indian region during MH and lowest during LGM. These slow changes in large-scale circulation patterns resulted in relatively highest simulated ISM rainfall during the MH, and lowest in the LGM.