Heatwaves have now become second most disastrous event

New Delhi, Apr 30: The Indian Institute of Tropical Meteorology in a research published in the Weather and Climate Extremes journal of Elseiver last years said that the mortality rates for extreme weather events are on a decline but rising significantly for heatwaves and lightning events.

The mortality rate of tropical cyclones reduced by 94 per cent in the past 20 years but for heatwaves and lightning it increased by 62.2 per cent and 52.8 per cent respectively. The paper assessed the mortality rates between 1970 and 2019.

Heatwaves have now become the second most disastrous event according to the paper. The mortality rates increased by almost 27 per cent in 2010-2019 when compared to 2000-2009. In 2000 to 2019 period there have been 2,354 heatwave related deaths. "The warming of the tropical Indian Ocean and more frequent El-Nino events in the future may further lead to more frequent and longer heatwave episodes over India. Therefore, even though the mortality due to floods and tropical cyclones has declined, it has increased for heatwaves," the research paper read.

The data on deaths are recorded by the health department or even the revenue department in some states. As of now, we do not have a very systematic way of reporting heat-related deaths. For example, majority of heat-related deaths are not classified as heat deaths. They are mostly among older people with co-morbidities whose deaths may be reported as heart failure, stroke or kidney failure from dehydration. These are called indirect heat strokes. There are also sun strokes among people who are working outdoors and are exposed to sunshine. Almost 80 to 90% of heat-related deaths are indirect and may not be documented. They can happen at night or evening also but are mainly due to heat stress, the paper also added.

In Ahmedabad there were 800 excess deaths due to heat in May 2010 only in a week. Most of them were indirect heatstrokes. It also said that any temperature above 45 degree Celsius could be lethal.

Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology said that in some regions experiencing heatwaves, it is not just about the high temperatures but the accompanying rise in humidity too that matters. Sustained heatwaves can be dangerous, especially when combined with high levels of humidity. If the air has high levels of humidity along with the heat, the body stops sweating and becomes unable to regulate the internal temperature. This can result in a heat stroke leading to multiple organ failure and deaths.

He also said that both temperatures and humidity are increasing in India and all over the world. Air can hold more moisture with more heat, and the combined impact of heat and humidity hence becomes critical. However, our heatwave forecasts or policies do not factor in this aspect. With more warming under climate change impact, the combined impact of heat and humidity is set to rise. A recent report from the Ministry of Earth Sciences points out that the mortality rates per million for heatwaves have increased by 62.2% during the last four decades. Heatwaves affect work productivity, by reducing performance and increasing heat-related illness. A decline of 30-40% in the work performance is projected over India by the end of the century due to the elevated heat stress levels.

"The #heatwave in #India and #Pakistan is hitting many millions of people and the economy. Temps topped 45°C (113°F), will ease by 2 May. #Heatwaves are one of the signs of #climatechange," the World Meteorological Organisation(WMO) said in a tweet.