Future projection of Indian summer monsoon variability under climate change scenario: An assessment from CMIP5 climate models

Abstract

In this study, the impact of enhanced anthropogenic greenhouse gas emissions on the possible future changes in different aspects of daily-to-interannual variability of Indian summer monsoon (ISM) is systematically assessed using 20 coupled models participated in the Coupled Model Inter-comparison Project Phase 5. The historical (1951-1999) and future (2051-2099) simulations under the strongest Representative Concentration Pathway have been analyzed for this purpose. A few reliable models are selected based on their competence in simulating the basic features of present-climate ISM variability. The robust and consistent projections across the selected models suggest substantial changes in the ISM variability by the end of 21 st century indicating strong sensitivity of ISM to global warming. On the seasonal scale, the all-India summer monsoon mean rainfall is likely to increase moderately in future, primarily governed by enhanced thermodynamic conditions due to atmospheric warming, but slightly offset by weakened large scale monsoon circulation. It is projected that the rainfall magnitude will increase over core monsoon zone in future climate, along with lengthening of the season due to late withdrawal. On interannual timescales, it is speculated that severity and frequency of both strong monsoon (SM) and weak monsoon (WM) might increase noticeably in future climate. Substantial changes in the daily variability of ISM are also projected, which are largely associated with the increase in heavy rainfall events and decrease in both low rain-rate and number of wet days during future monsoon. On the subseasonal scale, the model projections depict considerable amplification of higher frequency (below 30day mode) components; although the dominant northward propagating 30-70 day mode of monsoon intraseasonal oscillations may not change appreciably in a warmer climate. It is speculated that the enhanced high frequency mode of monsoon ISOs due to increased GHG induced warming may notably modulate the ISM rainfall in future climate. Both extreme wet and dry episodes are likely to ACCEPTED MANUSCRIPT 3 intensify and regionally extend in future climate with enhanced propensity of short active and long break spells. The SM (WM) could also be more wet (dry) in future due to the increment in longer active (break) spells. However, future changes in the spatial pattern during active/break phase of SM and WM are geographically inconsistent among the models. The results point out the growing climate-related vulnerability over Indian subcontinent, and further suggest the requisite of profound adaptation measures and better policy making in future.

Multi-Basin Modelling of Future Hydrological Fluxes in the Indian Subcontinent

“…Overall our results support previous findings that climate projections reveal an increase in monsoon precipitation in the mid-century [54,55] and a possible extension of the monsoon period [56][57][58]. Our results over Northern and Western India and the southeastern coastline differ from previous projections based on the CGCM3.1-PRECIS model chain and the A1B emission scenario [31,59].…”

Drying of Indian subcontinent by rapid Indian Ocean warming and a weakening land-sea thermal gradient

“…Meanwhile, the CMIP5 future projections suggest an increase in rainfall over the central Indian subcontinent 26 , though one must note the ongoing debate about whether CMIP5 models are in fact capturing the historic monsoon trends accurately 4,11,12,24 and whether the monsoon projections are reliable in these models 25 . The overall weakening trend of monsoon rainfall over South Asia is a matter of grave concern since the socio-economic livelihood in this region, including agriculture, water resources and power generation are irrevocably dependent on it.…”

CMIP5 Projected Changes in the Annual Cycle of Indian Monsoon Rainfall

“…Many studies have been undertaken [4][5][6][7][8] to study the Indian monsoon rainfall variability in a warming climate. It has been found that all models simulate a stronger seasonal mean monsoon rainfall in the future as compared to the historic period under the strongest warming scenario of RCP 8.5.…”