It's a startlingly exact number that's going around this week, and it's one that nobody can yet measure: 15,800. India may see that many more heat-related deaths in the coming months due to the impending “super El Nino,” says a University of Chicago research outfit. On a global scale, the same study estimates that the death toll will be around 451,000, enough to grab the headlines in Delhi to Dhaka within hours of the release. Precision and accuracy are quite separate and it is in the difference between the two that this story actually resides.

The report is from the Climate Impact Lab (CIL) of the university's Energy Policy Institute, which hit headlines in Indian and international media midweek. It is based on the central prediction that the planet is likely to see the average level of El Nino conditions for the next few months that would normally not be seen until 20 years from now increase the average land temperatures by about 1.2 degrees Celsius. This kind of framing should alert readers to the fact that this is not a body count, but a projection based on assumptions piled on assumptions.

One of the study's authors, Emily Grover-Kopec, has been giving reporters the run down of the mechanics for the last two days, and her explanation is worth sitting with as it exposes the sophistication and fragility of the exercise. The estimate is based on two things which move, which change. The first is a seasonal temperature forecast extracted from the European Centre for Medium-Range Weather Forecasts' (ECMWF's) SEAS5 model, which the team says is one of the most widely used seasonal forecasting systems around the world and is based on an ensemble of 51 members to reflect the range of possible outcomes rather than a single forecast.

The latter is a temperature-mortality relationship, a formula that outlines the historical association between the movement of death rates and temperature, based on 30 years of data from 1996 to 2025. This long baseline was not taken by chance, Grover-Kopec explained, since the figures were linked to a time frame that the policy makers could relate to, and not to some distant time period of climate averages, which no longer aptly represents the functioning of cities, populations and health systems in India.

This has yet to be done, and it is extremely important, peer review. The methodology is published and explained, but has not been subjected to the same level of scrutiny that would be expected prior to claiming this to be "settled science". This is being sounded by independent voices already. Abhiyant Tiwari, head of climate resilience and health work at the Natural Resources Defense Council, India, says the study is an early warning that will likely prove useful, but "until the entire methodology has been subjected to that level of peer scrutiny, you should not compare the mortality figures against actual mortality statistics. Similar words of caution have come from public health researchers at AIIMS, who identified the same dichotomy: a prediction intended to spur action, rather than a prediction with certainty.

Then there's the time aspect to note. Nearly half of India's deaths (around 7,400) are projected to occur between Dec and Feb, a time when the heat wave crisis isn't really a crisis in India at all. The risk, however, doesn't stop there, the researchers point out, and heat mortality in India and Pakistan may continue to rise as the northern hemisphere heads into the summer of 2027. It's a long runway for such a projection to stick and long runways are where seasonal forecasts typically fail.

None of this equates to a lack of concern about the underlying concern. Regardless of the exact level of accuracy of any one prediction, the economic and human impact of heat in India is already well established and far less uncertain than a six-month mortality prediction. India could be losing about six per cent of its working hours every year by 2030 due to heat stress, according to the International Labour Organisation, which estimated that this would be the equivalent of losing approximately 34 million full-time jobs, mostly in agriculture and construction.

A comparable scenario has been given a price tag by McKinsey's Global Institute, which projects $150-$250 billion in losses per year by the end of this decade. A more recent field study of informal workers in the cities of Ajmer, Delhi and Agra revealed that heat-related kidney illness and lost working capacity was already costing the Indian economy at the time about 78 billion dollars, or nearly two percent of GDP in 2024 alone. Meanwhile, Lancet reports that the number of deaths due to heat in India has increased by 55 percent from the early 2000s to the 2017-2021 period and that in 2021, more than 167 billion potential hours of labour have been lost.

In the context of the above, the number 15,800 is not a scientific statement, but a marketing tool for urgency; the very kind of marketing tools their more careful defenders suggest it's effective as: a nudge towards preparedness, not a body count to be memorised. Climate scientists say the Heat Action Plans already in place in India, developed in Ahmedabad, and now rolled out in dozens of cities, are a template that other heat-stressed countries can use.

The better answer to this research is to debate the figure of 15,800 or 7,000 or 20,000 is incorrect. What would matter, irrespective of which number is nearer to being right, would be to treat the uncertainty itself as a warning, and to continue developing institutional muscle, early warning systems, and cooling access and healthcare surge capacities.