High-Emission Climate Scenario Could Drive Sharp Rise in Heat-Related Deaths Across Indian Cities: Study

Extreme heat events are increasingly recognized as "silent killers" that impose cumulative physiological stress on urban populations, yet previous research has frequently masked regional heterogeneity by focusing on short-term associations or relying on outdated single-model simulations. To address this critical gap, Ingita Dey Munshi from the School of Computational & Integrative Sciences at Jawaharlal Nehru University and her international colleagues aimed to quantify long-term mortality trajectories across 67 diverse cities using updated Coupled Model Intercomparison Project Phase 6 (CMIP6) climate projections.

Therefore, utilizing an Autoregressive Integrated Moving Average with exogenous regressors (ARIMAX) framework, the longitudinal analysis was trained on national health records from 1970 to 2023 to project mortality across 67 geographically diverse urban locations through the year 2100. The methodology compared intermediate mitigation and high-emission Shared Socioeconomic Pathways (SSPs) using Summer Mean Temperature (SMT) as the primary climate driver while excluding complex non-linear exposure-response relationships to ensure model interpretability.

Key Clinical Findings of the Study Include:

• Accelerated Fatality Rates: The analysis shows that under the high-emission scenario, mortality trajectories documented a dramatically steeper escalation that becomes markedly more accelerated after the mid-century mark.

• Pathway Sensitivity: Comparative analysis demonstrated a multi-fold surge in heat-related deaths for the high-emission pathway relative to the more moderate mitigation path, emphasizing the extreme sensitivity of health outcomes to carbon trajectories.

• Regional Vulnerability Hotspots: States within the Deccan Plateau and western India highlighted disproportionately higher mortality growth compared to high-altitude regions, reflecting amplified sensitivity in regions already operating near physiological thresholds.

• Structural Response Divergence: Multidimensional scaling analysis observed that extreme warming drives structurally different regional responses, leading to a significant reorganization of mortality behavior and widening spatial inequality.

• Mitigation Efficacy: Conversely, the intermediate mitigation scenario revealed significantly more moderate and spatially uniform mortality trends across the subcontinent by the end of the 21st century.

The results suggest that without substantial global mitigation efforts, India is likely to face a persistent escalation in heat-related deaths, transforming periodic extreme heat from an acute hazard into a chronic and unevenly distributed public health emergency.

Thus, the analysis concludes that healthcare providers and urban planners should collaborate to develop region-specific resilience strategies and integrate long-term thermal risk assessments into existing Heat Action Plans (HAPs) to protect vulnerable populations.

While the study's reliance on 1-degree resolution climate models may overlook localized microclimatic variations, future research integrating district-level socioeconomic vulnerability and compound heat stress metrics will be essential to further refine these public health projections.

Reference

Munshi, I. D., Kailasam, A. S., Shukla, S., Bakar, K. S., & Chakraborti, A. (2024). Heatwave-Related Mortality Across Indian Cities Under Future Climate Scenarios. arXiv preprint arXiv:2403.24244v1.