No heat index: Delhi struggles to manage effects of extreme heat
Since March this year, parts of Delhi have witnessed 24 heatwaves, with the most intense, in terms of maximum temperature, between May 12 and May 22 — yet the city does not have a a heat action plan to prevent extreme heat related deaths, nor uses a heat index to assess the actual impact of extremely high temperatures and excess humidity on people’s health.
This, despite senior officials of the Delhi government admitting that they have been consulting with private and government agencies to formulate a comprehensive heat action plan for the city for several years.
An action plan would incorporate early warning systems for temperature, ways to prevent exposure of those in vulnerable population segments, and longterm mitigation strategies.
The officials also confirmed that while the state’s work-in-progress climate action plan has touched upon the impact of climate change on extreme weather events in the Capital, it does not currently include an early warning system, or an action plan on what to do when temperatures rise beyond a certain level – much like the plan that kicks in when AQI falls below a certain level for a certain duration.
An earlier plan did have details, one of the officials added on condition of anonymity.
“The earlier climate action plan for Delhi, which was released in 2019, was based on old data, which only incorporated temperature recordings. That plan suggested a colourcoded response system on what government agencies needed to do when temperatures reached a certain level. That plan, however, has expired,” said this person, who works in the environment department of Delhi government.
Delhi is among 23 states/union territories in the country identified by the India Meteorological Department and the National Disaster Management Authority (NDMA) as being prone to heatwaves and which need state-level heat action plans.
Climate experts have pointed out that in the coming decade the average increase in temperature recordings in the city could range anywhere between 1.5-2 degrees Celsius. Other states that face similar risks include Rajasthan, Punjab, Uttar Pradesh, Madhya Pradesh, Gujarat, Maharashtra and Jharkhand.
Since 2017, NDMA has been conducting regular workshops with representatives of states on ways to implement a holistic heat action plan. While IMD does issue forecasts on monthly, fortnightly, weekly and a three-day basis, these often remain just forecasts, and states do not use them as inputs in an action plan -- simply because none exist in most cases.
Heat action plans have to be created at the level of cities and one of the few cities in India to have on is Ahmedabad, Gujarat.
Last week World Weather Attribution network, a team of international climate scientists released a rapid attribution analysis of the spring heat wave in India and Pakistan this year, pointing out that while an unusually long and early onset heatwave spell like the one India and Pakistan just experienced was very rare, with a chance of occurring only once in 100 years, “human-caused climate change has made it about 30 times more likely to happen.”
The WWA Network in its guide for journalists on ‘Reporting extreme weather and climate change’ earlier this month cited an Intergovernmental Panel on Climate Change report in 2021 that said a heatwave that would have otherwise occurred once in 10 years in the pre-industrial climate will now occur 2.8 times over ten years and be 1.2ºC hotter.
Absence of heat index
Another aspect where Indian cities are struggling is to measure the actual impact of extreme temperatures on the human body. Climate experts said that with the gap between normal and actual temperature recordings increasing every season, it is imperative that the meteorological department come up with more accurate indicators of heat on the human body rather than just giving out the day’s maximum and minimum recording.
Experts said that measures such as the heat index and wet bulb temperatures will be better indicators of what people in a city are actually experiencing.
For instance, wet bulb globe temperature is a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, the sun angle and cloud cover (solar radiation). The heat index takes into consideration temperature and humidity . Both indices are better measures of how heat and other factors in the environment affect the human body.
IMD currently gives out maximum and minimum temperatures, along with relative humidity in its daily recordings but does not release wet bulb temperatures and also does not have a heat index.
Madhavan Rajeevan, former secretary, the union ministry of earth sciences, said that having a heat index will give a better picture of the actual health impacts of health and humidity. “It might be a good idea to start using a heat index and also teaching people and government agencies to interpret it. A heat index over 41 degrees Celsius is considered dangerous,” Rejeevan said.
Mahesh Palawat, vice president (meteorology and climate change), Skymet Weather Services, said that a heat index will especially help people get a better sense of the outside temperatures between May and July when humidity levels across India soar. “With climate change becoming a bigger reality in cities and extreme temperature recordings increasing every year, it is imperative that urban centres have systems in place to mitigate its damage,” he added.