Of the 6,529 deaths reported due to heat wave between 2002 and 2014, 5,544 — or 85 per cent — have occurred in the states of (undivided) Andhra Pradesh and Odisha, according to data with the India Meteorological Department (IMD). As many as 4,769 people — 73 per cent of the total — have died in Andhra Pradesh and Telangana alone.
Summer temperatures in this region of eastern coastal India, though high, have not been the highest in the country. And yet, this year’s reported toll of nearly 2,000 fits into the general pattern of a disproportionately high heat-related death count in this region.
Arvind Kumar Srivastava, director of IMD’s National Climate Centre in Pune, put the disclaimer that the numbers of deaths are mostly estimations, and include figures reported in newspapers. But even then, the Odisha-Andhra skew is clear.
In 2003, the last time a heat wave of comparable severity prevailed in India, almost 1,300 people were reported to have been killed in Andhra Pradesh, according to the IMD database. More recently, in 2013, a total of 1,393 heat-related deaths were reported from Andhra Pradesh in six heat-wave stretches from April to June. Last year, 447 of the 535 deaths countrywide — 84 per cent — were reported from Andhra Pradesh and Telangana.
Curiously, despite the stark numbers, there is no authoritative study on the reasons. There could be a variety of them — climatic to socio-economic and cultural.
While the northern plains from Rajasthan to Bihar, and central Madhya Pradesh and Chhattisgarh, consistently see higher summer temperatures, they do not necessarily have the highest numbers of what are technically categorised as “heat waves”.
A heat wave is declared when the maximum temperature crosses 45 degrees Celsius, or if it rises more than 4 degrees Celsius above normal. If it rises more than 6 degrees above normal, a “severe” heat wave is declared.
The severity of a heat wave — the difference between actual and normal temperatures — and its length, that is the number of days for which it lasts, makes the threat worse.
In a paper published in 2013, Dr D Sivananda Pai of IMD showed that between 1964 and 2010, Nellore district of Andhra Pradesh faced 18 prolonged heat waves of more than 15 days — the most anywhere in India. Ramagundam, the worst affected this year, figured on the list, having seen a heat wave lasting 16 days in 1984.
And yet, not one station in Andhra Pradesh had a “severe” heat wave of more than seven days during 1964-2010.
“It is difficult to say why so many deaths have occurred in Andhra Pradesh. There could be many reasons but since we have not studied it from that angle, these can only be possibilities. Prolonged heat waves, which the state has faced many times, could be one reason, but there could be many more reasons, including the inability of people to adapt to sudden change in temperatures, lack of administrative preparedness to deal with heat waves, or socio-economic reasons relating to labour, employment, place of work and similar things,” Pai said.
Some climatic reasons probably make heat waves on the east coast deadlier. In May and June, the Bay of Bengal often witnesses anti-cyclonic circulations which work towards trapping the heat in the lower atmosphere. This kind of anti-cyclonic feature — seen this year from May 16 to May 28 — can explain frequent and prolonged heat waves in Andhra Pradesh, Telangana and Odisha, and also in West Bengal, which too has witnessed a significant number of heat-wave deaths in the past. However, Tamil Nadu, which too lies on the east coast, has never reported any deaths from heat.
Some experts attribute the high mortality to humidity in the coastal regions. “High temperatures are bearable. But when mixed with high humidity, they become suffocating,” IMD’s Srivastava said. Humidity, which is noticeably higher on the east coast — especially in the interior areas — than on the west, aggravates symptoms of heat retention in the body, according to medical specialists. Also, temperature data since 1901 show the average temperature for May on the east coast is almost three degrees higher than on the west.
A 2012 paper, co-authored by Saudamini Das of the Insitute of Economic Growth at Delhi University, linked some heat-wave deaths in Odisha to lack of awareness of ways to deal with excessive heat. The study did not probe why more deaths occurred in the study area than elsewhere.