Intensification of Compound Heat-Humidity Stress on Human Physiological Survivability Driven by Climate Change in Iran

Dadashi-Roudbari, Abbasali

doi:10.22111/jneh.2026.55020.2164

Intensification of Compound Heat-Humidity Stress on Human Physiological Survivability Driven by Climate Change in Iran

Articles in Press

Document Type : Research Article

Author

Abbasali Dadashi-Roudbari

Assistant Professor, Department of Geography, Faculty of Letters and Humanities, Ferdowsi University of Mashhad, Mashhad, Iran

10.22111/jneh.2026.55020.2164

Abstract

The interaction between dry-bulb temperature and relative humidity, exacerbated by global warming, profoundly impairs human thermoregulation by restricting latent heat dissipation. This study provides a comprehensive evaluation of heat stress dynamics across Iran using a bias-corrected CMIP6 multi-model ensemble under the SSP2-4.5 and SSP5-8.5 scenarios to calculate the NOAA Heat Index (NOAA-HI). Analysis of the ensemble outputs reveals substantial spatial heterogeneity in the climatological distribution of the NOAA-HI. High temperature and humidity levels are already triggering severe thermal stress, most notably along Iran’s northern coastlines and throughout its southern territories. In these high-impact zones, the combined effects of solar radiation and ambient humidity push the index beyond 30 ∘C, placing these environments firmly within established danger classifications. Conversely, the northwestern and mountainous regions currently remain within the caution category. Under the high-emission SSP5-8.5 scenario, anticipated shifts in the bioclimatic regime will systematically alter the frequency of heat stress thresholds, leading to an acute intensification of thermal stress along the eastern and southern coasts. Quantitatively, the proportion of days categorized as “danger” is projected to surge from a historical baseline of 1.4%to 12.8% in the far future. This escalation is accompanied by a massive expansion of the “extreme caution” category, projected to dominate 42.8 of the year, a level of prolonged exposure that will severely erode the adaptive capacity of local biological systems. Ultimately, the progression of the NOAA-HI beyond safe physiological thresholds (>26.7 ∘C) into critical territory represents an existential threat to outdoor survivability and habitability across Iran’s lower latitudes and lowland plains. These findings underscore the urgent need for targeted mitigation and adaptation policies in vulnerable regions, providing a vital strategic framework for regional policymakers and environmental managers.

Keywords

Main Subjects

Climate-Change

References

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