Most parts of India are going through a severe heatwave as temperatures soar. Over the last decade, the instances of heatwave days have increased resulting in increased deaths. However, different agencies of the government like the NDMA, NCRB, MoES have provided different data on mortality due to heatwaves.
According to the European Union’s Copernicus Climate Change Service (C3S), March 2024 marked the world’s hottest March on record, continuing a streak of 10 consecutive months of record-breaking temperatures. The past 12 months, ending in March 2024, also set a new record as the hottest 12-month period ever recorded. It was 0.70°C above the 1991-2020 average and 1.58°C above the 1850-1900 pre-industrial average. While Europe experienced its second warmest March, regions like eastern North America, Greenland, eastern Russia, Central America, parts of South America, Africa, southern Australia, and Antarctica saw temperatures well above average, it reported.
Even in India, the temperatures are soaring with heatwave warnings being issued by the Indian Meteorological Department (IMD). IMD’s forecast for summer 2024 was that except for some isolated places in the east, the Northeast and Northwest, the rest of India was likely to experience above-normal maximum temperatures in April, May and June. The maximum temperatures in some regions were in the range of 42-44°C in the third week of April 2024 around the time phase I of the Lok Sabha Elections took place.
According to IMD, a heat wave is a period of excessively high air temperatures that can be dangerous to human health when exposed. It is defined based on temperature thresholds, either in terms of actual temperature or its departure from normal. In some places, it is also determined by the heat index, which considers temperature and humidity or extreme percentiles of temperatures.
The criteria for declaring a heatwave include:
Based on Departure from Normal:
- Heat Wave: Departure from normal is between 4.5°C to 6.4°C
- Severe Heat Wave: Departure from normal is greater than 6.4°C
Based on Actual Maximum Temperature:
- Heat Wave: Actual maximum temperature is at least 45°C
- Severe Heat Wave: Actual maximum temperature is at least 47°C
A heatwave is officially declared if the criteria are met in at least two weather stations within a Meteorological sub-division for at least two consecutive days, with the declaration made on the second day.
Heat waves have dangerous consequences
Heat waves present serious dangers due to extreme heat, causing heat stress, dehydration, and straining the cardiovascular system. Vulnerable groups like the elderly face higher risks. Heat-related illnesses, including heatstroke, can be fatal. Considering heat waves’ impact on human lives, data on the number of fatalities due to the extreme event is crucial for public health planning, risk assessment, emergency response, evaluating interventions, and adapting to climate change among others.
However, significant discrepancies exist in the data presented by different government organizations. Dataful has a collection of datasets on the number of deaths reported due to heat waves captured by different organizations, which has been used in this story.
Significant discrepancies in data reported by MoES and NDMA
For instance, if one compares the number of deaths due to heatwaves for the period from 2009 to 2022 based on data published by the Ministry of Earth Sciences or MoES (same as that published by the Ministry of Statistics and Programme Implementation (MoSPI) in its Envistats report) and that published by the National Disaster Management Authority (NDMA), there are significant discrepancies. It is seen that MoES reported a total of 6,751 deaths during these 14 years (2009 to 2022) while NDMA reported almost twice the number of deaths – 11,090. Even though there are huge discrepancies in the figures reported, the overall trend suggests that the deaths due to heat waves peaked in 2015 and have declined considerably since then.
Further, according to the World Meteorological Organization (WMO), between 1992 and 2020 (in 28 years), 25,692 deaths occurred due to heatwaves in India. About one-third or 8,716 deaths took place between 2011 and 2021. However, during the same 28-year period, MoSPI reported 13,239 deaths, nearly half of that reported by WMO. Between 2011 and 2021, MoSPI reported 6,252 deaths.
NDMA and NCRB are both under MHA and yet the data published by both have been different since 2014
NDMA is an autonomous body under the Ministry of Home Affairs. Another agency that operates under the same ministry is the National Crime Records Bureau (NCRB). NCRB, in its annual Accidental Deaths and Suicides in India (ADSI) report publishes the number of deaths due to heat strokes. It is based on data furnished by state police departments. According to the NCRB report, a total of 15,020 deaths due to heat strokes took place between 2009 and 2022, about 4,000 deaths more than that reported by NDMA. Until 2013, the data produced by NCRB matches with the one published by NDMA. However, since 2014, the values reported by NCRB are very different from those reported by NDMA. NCRB has also not given the state-wise figures for 2015.
Huge disparity is observed in state-wise data reported by NDMA and NCRB
Between 2016 and 2022, a notable disparity is evident when one compares the state-wise total number of deaths from heatwaves reported by the NDMA and those due to heat strokes reported by the NCRB. Unlike the overall figures, which showed a pattern- a surge in 2015 followed by a decline across all reporting thereafter, the state-specific figures for heat-related deaths do not exhibit a consistent pattern or correlation in the figures reported by states. For example, 764 deaths were reported by NCRB in Uttar Pradesh, whereas NDMA reported only 2. While NCRB reported 664 deaths in Punjab, NDMA reported nil. The disparity has been mapped in the following graph.
Health Ministry started capturing data on heat-related illnesses from 2015
Heat-related illnesses are health conditions caused or exacerbated by exposure to high temperatures and excessive heat. These are preventable. Some examples include Heat Cramps, Heat Exhaustion, Heat Stroke, and Heat Rash. Heat-related deaths in India were significant but not fully tracked, unlike in other countries. Hence, since 2015, the Union Health Ministry started collecting data on morbidity and mortality due to Heat-related illness through the Integrated Disease Surveillance Programme (IDSP) from heat-vulnerable States/UTs.
A total of 277 deaths were reported by the States between 2018 and 2022 due to heat-related illnesses, as per IDSP’s data. About 123 were reported by Bihar while Telangana, Andhra Pradesh, and Maharashtra reported more than 35 each. Considering heat stroke is also a heat-related illness, these figures \also deviate from the ones presented by NCRB.
Data gaps must be addressed
The discrepancies in data reported by different agencies regarding heat wave-related deaths in India underscore the urgent need for standardized and accurate reporting mechanisms. Gaps in data collection, including specific types of heat-related illnesses, and standardization of definitions highlight the importance of enhancing surveillance and reporting systems. Improving data quality and consistency is essential for better understanding the true burden of heat-related illnesses and implementing effective preventive measures. Lancet reports have estimated that heat-related deaths of people over age 65 increased by 55% in India in 2018-2022 compared to 2000-2004. Considering that the frequency, duration, and intensity of heat waves are likely to rise in the coming years, these data gaps should be addressed immediately.
