While this is certainly good news, a new report released by the ministry of earth sciences indicates that climate-related deaths are still a cause for concern: Heatwaves have claimed more lives in India than other natural hazards, with the exception of tropical cyclones, the report ‘Heat and Cold Waves in India Processes and Predictability’ released in April, pointed out.

Let’s look at the data from IMD's ‘Statement on Climate of India in 2022’. The most deaths from extreme weather events were caused by lightning and thunderstorms—1,285 — followed by 835 due to heavy rains and flooding, 37 due to snowfall, 30 due to heat waves and 22 due to dust storms.

Lightning strikes on average have killed nearly 2,000 people every year in India since 2004, which is nearly twice the number of deaths recorded since the late 1960s, the IMD said in 2021 referring to their analysis.

Yet, heat wave-related deaths are a cause for concern, as it is difficult to put a number to the deaths due to heat stress because most are not even documented.

In June, for example, in the span of less than a week, over 100 deaths, directly and indirectly, linked to heat waves, were reported from Uttar Pradesh, Bihar and Odisha.

Ballia’s chief medical superintendent Dr Diwakar Singh who issued a statement on behalf of the Ballia hospital stating that the condition of those with critical illnesses aggravated due to heat stress was shunted out of the district by authorities.

Pratyaya Amrit, Bihar’s additional chief secretary of disaster management and health department, contradicted the reports, saying none of the deaths were related to the heatwave conditions in the state.

Heat wave-related data might be unavailable but heat waves are now a reality in India.

On July 2, HT reported that parts of Bihar and West Bengal experienced continuous heatwaves for 19 and 17 days, respectively, in June, according to the IMD.

Bihar recorded a heat index of 50 to 60 degree Celsius during this period. West Bengal would have seen similar counts on the heat index as meteorological factors in both places such as delayed monsoon and high humidity were similar. The conditions were deadly with the potential to kill thousands of vulnerable people, experts had warned.

Humidity, a vital factor

First, let’s understand the science behind this.

IMD considers only maximum temperature to declare heat wave over a region. A heat wave is considered if maximum temperature of a station reaches at least 40 degrees C or more for plains and at least 30 degrees C or more for hilly regions. When declared based on departure from normal—a heat wave is declared when departure from normal is 4.5 degrees C to 6.4 degrees C and a severe heat wave is declared when departure from normal is >6.4 degrees C

When a heat wave is declared based on actual maximum temperature—it is declared when actual maximum temperature is 45 degrees C or more and a severe heat wave is declared when actual maximum temperature is 47 degrees C or more. If the above criteria is met at least in 2 stations in a sub-division for at least two consecutive days then heat wave can be declared. For coastal areas, aheat wave may be declared when maximum temperature is 4.5 degrees C or more from normal or maximum temperature is 37 degrees C or more.

But, it is humidity along with heat that makes it more uncomfortable – and deadly.

The human body cools itself by sweating, and if the air is too humid, sweat cannot evaporate and the body keeps getting hotter.

This condition can quickly lead to fatal heat stroke for people who cannot get to a cooler place, states an explainer by the Massachusetts Institute of Technology.

With several research papers and IMD’s long-term data indicating that the severity, area and span of heatwaves are going up, by now states should have been better prepared to prevent deaths and handle heat-related complications.

Going unrecorded

However, a number of issues are slowing down action on heat stress-associated morbidity and mortality.

For one, hospitals are not actively tracking heat-related deaths: Only direct exertional heat strokes are documented. The National Crime Records Bureau puts heat stroke or sunstroke numbers in the category of accidental deaths. But 90% of heat-related deaths may be caused indirectly by what doctors call non-exertional heat stroke.

Those deaths can be documented by tracking daily excess deaths, Dileep Mavlankar, director at the Indian Institute of Public Health, Gandhinagar, had explained in HT’s July 2 report.

“First, we need to establish if there was excess mortality. For example, in Ahmedabad, we observed the average daily mortality is 100 in May. During heatwaves, we noticed excess mortality going up to 310 deaths which is 210 excess deaths. So, first, it's very important to track what is the mortality per 1,000 population and whether there are excess deaths. Even when there are no excess deaths, we should know what are the causes and track the impact of heat,” Mavlankar said.

Second, the IMD doesn’t yet take into account the role of humidity in declaring heat waves: It only focuses on maximum temperatures. Only this April, IMD for the first time started issuing a heat index or 'feels like' temperatures for the entire country. This is to make heat data more accessible to the public so that they can take heat-related precautions.

The heat index is based on a formulation by the US national weather service and National Oceanic and Atmospheric Administration.

More importantly, it's also not clear if heat index warnings are reaching the most vulnerable in the interior parts of the country who are exposed to both heat and humidity.

Thirdly, since heat deaths are not well documented yet in India and are not categorised as ‘disasters,’ there is no way to compensate victims for the loss of lives and productivity.

Cyclones, droughts, earthquakes, fires, floods, tsunamis, hailstorms, landslides, avalanches, cloudbursts, pest attacks, frosts and cold waves are eligible for relief assistance under the State and National Disaster Response Force.

Here to stay

Most parts of India, including those in peninsular India and the coasts will see 12-18 heatwave days by 2060, the MoES report referred to above had projected recommending a comprehensive response plan for heat waves which includes cultural, institutional, technological and ecosystem-based adaptation strategies.

With the increase in average temperatures globally, the moisture-holding capacity of the atmosphere is also going up.

The record-breaking humid heat wave that hit east and north India, as well as Bangladesh, Laos and Thailand in April, was made at least 30 times more likely by climate change, a rapid attribution analysis by an international team of scientists with the World Weather Attribution group said.

A highly vulnerable population was subjected to a deadly combination of high heat and humidity which amplified the impacts in early summer this year.

Large populations across South Asia during a 4-day period between April 17 and 20 were exposed to a heat index or ‘feels like’ temperature of over 41 degrees Celsius, and some areas, particularly in Laos, recorded a heat index of over 54 degrees Celsius, which can be deadly, scientists said.

“We know that with global warming, moisture holding capacity is going up globally. The oceans are also warming up leading to higher evaporation. To address the fact that high humidity and heat can affect people, IMD has introduced a heat index from this year,” said DS Pai, senior scientist at IMD.

The recommendations of the April report include improving India’s buildings through ventilation and insulation; raising awareness about heat stress; changing work schedules; providing early warning; and creating cool shelters.

On an average, more than two heatwave events occur over northern parts of the country and coastal Andhra Pradesh and Odisha. In some pockets, heatwave frequency even exceeds four in a season. Most IMD stations show increasing trends of heatwave events during the 60-year period in terms of heatwave duration; frequency and severity.

Studies referred to by the report suggest the frequency of severe heat waves will increase by 30 times the current climate by the end of the 21st century if the global average temperature rise is not limited to 2 degrees C above pre-industrial conditions.

“Based on an ensemble of high-resolution climate change simulations, the study found that wet bulb temperature (35 degrees C) extremes in South Asia are likely to approach and exceed this critical threshold in a few places by the end of the 21st century under the business-as-usual scenario of future greenhouse gas emissions. The greatest risk from extreme heat waves is in the densely populated agricultural regions of the Ganges and Indus River basins,” the report said.

El Nino effect

Earlier this week, World Meteorological Organisation said El Niño conditions have developed in the tropical Pacific for the first time in seven years, setting the stage for a likely surge in global temperatures and disruptive weather and climate patterns. This could mean extreme heat in India in the coming summer.

“The onset of El Niño will greatly increase the likelihood of breaking temperature records and triggering more extreme heat in many parts of the world and in the ocean,” said WMO Secretary-General Petteri Taalas.

“The declaration of an El Niño by WMO is the signal to governments around the world to mobilise preparations to limit the impacts on our health, our ecosystems and our economies,” he said. “Early warnings and anticipatory action of extreme weather events associated with this major climate phenomenon are vital to saving lives and livelihoods.”

El Nino is characterised by an unusual warming of waters in the eastern equatorial Pacific, which has a high correlation with warmer summers and weaker monsoon rains in India.