Mapping Hazard to Extreme Temperature Events Over the Indian Subcontinent

The recent AR6 report of the Intergovernmental Panel on Climate Change (IPCC) explicitly shows that the observed change in hot extremes (including heatwaves) with high confidence in human contribution to the observed changes has highly increased in the South Asian (SAS) domain which comprises the Indian subcontinent. Extreme heat events are more frequent and intense across the globe since the 1950s and have adverse societal and economic impacts. Considering current warming trends and projections, heatwaves are becoming a serious problem in India. Exposure to extreme heat in the population is increasing due to climate change. Also, observed temperatures are increasing globally as well as regionally as an effect of global warming. As heat stress occurs when the human body cannot get rid of the excess heat, it can be considered a good proxy for the heatwave hazard. Heat stress results in heat stroke, exhaustion, cramps, or rashes. Exposure to extreme heat can result in occupational illnesses and injuries. An agrarian country like India will have large economic damage when climate-related heat stress increases the occurrence of droughts and exacerbate water scarcity for irrigation. Hence the impact of the heat stress hazard is spotted and largely discussed both in the academic and political domains. In this study, Universal Thermal Climate Index (UTCI) based hazard map is developed for India with a non-parametric multivariate approach. The prominent heat stress hazard areas are identified and mapped with reference to the UTCI assessment scale which is categorized based on thermal stress. The probability of occurrence is also mapped using the exceedance probability with the UTCI reference. Heat stress hazard map provides the basis for a wide range of applications in public and individual precautionary planning such as heatwave action plans, urban and regional planning, the tourism industry, and climate research. Hence a country-level extreme temperature hazard map is of dire necessity.

Keywords: Exceedance probability, hazard map, heat stress, multivariate approach, non-parametric method