Heat wave magnitude over India under changing climate: Projections from CMIP5 and CMIP6 experiments

Atmospheric warming is expected to increase the magnitude and frequency of extreme climatic events namely floods, droughts, heat waves, and so on. Thus, the present study attempts to answer the following research questions; (i) What are the possible implications on future heat wave events due to the projected temperature? (ii) What are the expected changes in heat wave properties under different classifications of heat wave events under different climate scenarios? (iii) Whether the future projection of heat wave events differ significantly under CMIP5 and CMIP6 experiments over India? To answer the above questions, the present study uses the bias-corrected future projections of maximum temperature (Tmax) from 26 GCMs that is, 13 from CMIP5 and 13 from CMIP6 experiments. In addition, two RCPs (4.5 and 8.5) under CMIP5 and four SSPs (126, 245, 370, and 585) under CMIP6 scenarios are considered. The Heat Wave Magnitude Index (HWMI) is used to characterize the heat wave over India. The essential findings from the study indicate that the Tmax anomaly is likely to increase (SSP126 < SSP245 < SSP370 < SSP585 and RCP4.5 < RCP8.5) in future causing more intense, high frequency, and long duration heat wave events over India. Presently unaffected large regions of southern, northeast, and western parts are expected to be severely affected by heat wave events. More intense heat wave events are likely to occur under RCP8.5 scenario as compared to SSP585 scenario. The percentage of affected area is projected to increase significantly from SSP126 to SSP585 under extreme and very extreme heat wave events. Under RCP8.5 scenario, the average duration of heat wave events for very extreme, and super extreme classifications is significantly higher than SSP585 scenario. Our findings suggest the paramount necessity of adaptation strategies to address the adverse consequences of foreseen heat wave events.