India will launch its own composite index next year to quantify the impact of heat on its population and generate impact-based heat wave alerts for specific locations, the India Meteorological Department (IMD) has said.
The IMD began issuing an experimental heat index for different parts of the country last week, taking into account air temperature and relative humidity to determine how hot it really feels.
"The heat index is an experimental product. It is not validated and we have mentioned that (on the IMD's website) too. We are coming up with our own system now, a multi-parameter product called 'heat hazard score'. We hope that it will be better than the others," Mrutyunjay Mohapatra, Director General of Meteorology, IMD, told PTI.
Along with temperature and humidity, it will integrate other parameters such as wind and duration of exposure. It will be an effective indicator of heat stress for people, he said.
The IMD chief said the hazard score will be ready in around two months and "it will be operational in the next summer season".
Asked if the IMD has incorporated health data into the product, he said the weather bureau will gradually do it. "We have been working on it but health data is not readily available in some places."
Mr. Mohapatra and his team conducted a heat wave hazard analysis for the entire country last year, taking into account maximum temperature, minimum temperature, humidity, wind and the duration of heat waves.
The analysis will help generate heat hazard scores which will be utilised as thresholds to issue impact-based heat wave alerts for specific locations.
"The heat index provides apparent temperature, factoring in temperature and humidity. Heat hazard score will depict the severity in terms of numbers, such as on a scale of 1 to 10," another official said.
The major difference between the heat index of the U.S. and India's heat hazard score is that the latter also considers other parameters that aggravate heat situations such as minimum temperature, wind and exposure duration, he added.
The IMD has predicted above-normal maximum temperature and more heatwave days in eastern and central-eastern parts of the country in May.
According to IMD data, there was a 24% increase in the number of heat waves during 2010-2019 compared to 2000-2009. However, there is a decreasing trend after 2015.
Between 2000 and 2019, the mortality rate for tropical cyclones decreased by 94%, whereas it increased by 62.2% for heat waves.
The Fifth Assessment Report of the Intergovernmental Panel on Climate Change said the major climate risk for south Asian countries will be the rising mortality rate due to heat waves.
A moderate increase in average temperatures or a slight increase in the duration of heat waves will lead to a significant increase in the mortality rate in India, unless remedial and response measures are taken, it said.
However, heat waves are yet to be notified as a natural disaster at the national level in the country.
Heat waves have an immense impact on human health, causing cramps, exhaustion, stress and heat stroke and very severe heat waves even lead to death. The elderly, children, and people with heart and respiratory problems, kidney diseases and psychiatric disorders are particularly affected.
Extreme periods of high temperatures can lead to a significant reduction in crop yields and cause reproductive failure in many crops.
This year, India experienced its hottest February since record-keeping began in 1901. However, above-normal rainfall in March kept temperatures in check.
March 2022 was the warmest ever and the third driest in 121 years. The year also saw the country's third-warmest April since 1901.
In India, about 75% of workers (around 380 million people) experience heat-related stress.
A report by the McKinsey Global Institute warns that if this continues, by 2030, the country could lose between 2.5% to 4.5% of its Gross Domestic Product per year.
