Extreme Heat in India — Links to Climate Change and Health

In India, the highest temperatures occur before the monsoon starts, typically in May or the beginning of June. In the arid areas in the west temperatures often rise in the high 40s. On May 19th 2016 temperatures exceeded 50 °C in a region on the India Pakistan border and even reached 51.0 °C in Phalodi, which is India’s all time record. The question of whether human-induced climate change played a role in this record-breaking heat was investigated using observed temperature trends, global coupled climate models (CMIP5) and a large ensemble of SST-forced models. The study failed to find a significant trend for the highest temperature of the year, TXx, in much of India including the area with the record temperature.

In 2015, another heatwave resulted in thousands of deaths in Andhra Pradesh and surrounding states. A similar study also revealed no trend in extreme high temperatures. While some studies using different definitions of heatwaves have found an increase in the frequency, total duration and, maximum duration of heatwaves in a limited region in central and northwestern India, there is no significant trend in the rest of India. A plausible mechanism for the lack of significant trend is a masking due to a trend in aerosols i.e., worsening air pollution that causes less sunshine to reach the ground and thus a cooling influence, especially in dry seasons. 

Evidence from studies around the world suggests that aerosols also play a compounding role on mortality during heatwaves. Excessive heat can have a devastating impact on human health resulting in heat cramps, exhaustion, and life-threatening heat strokes. It can also aggravate pre-existing pulmonary conditions, cardiac conditions, kidney disorders and psychiatric illness. High air pollution can exacerbate many of these problems. As India begins to enact the necessary regulation of air quality, the required rapid cleaning of the city air may well lead to even higher maximum temperatures during heat waves. Given this possible future, the overall human health effects of cleaner air, but higher extreme temperatures must be considered in planning decisions.