Heat events in the Indian subcontinent under a warming climate scenario: Detection and Implications on human health

Global temperatures have shown a warming trend over the last century, mainly as a result of anthropogenic activities. Rising temperatures are a potential cause for increase of extreme climate events, such as heat waves, both in severity and frequency. Under an increasing extreme event scenario, the world population of mid- and low-latitude countries is more vulnerable to heat related mortality and morbidity. In India, the events occurred in recent years have made this vulnerability clear, since the numbers of heat related deaths are on a rise.

Over India, the heat waves occur during the months of April to June and can impact various sectors including health, agriculture, ecosystems and the national economy. In May 2015, a severe heat wave due to the delayed onset of southwest monsoon affected parts of south-eastern India, which claimed more than 2500 lives. Preliminary results show the prevalence of Heat events in six different regions of India during the pre-monsoon (March, April, May) and transitional (May, June, July) months.

We consider daily maximum temperatures and NOAA’s Heat Index (HI), a combination of temperature and relative humidity (also known as apparent temperature) which gives an insight into the discomfort because of increment in humidity. It is important to take HI along with temperature anomalies, since humidity also plays a role in transitional period.

Heatwaves over India are known to be linked with mortality and have indirect impacts on human health. To evaluate the heat related risk of mortality on Indian population, indicators and clusters of heat events were computed by taking into account population weighted temperature exposure.