First, the official death toll is an undercount.
This was the interpretation presented to me in May by Dr. Friederike Otto of World Weather Attribution; by Kathy Baughman-McLeod, director of the Atlantic Council’s Arsht-Rockefeller Resilience Center, in June; and by Avikal Somvanshi, of the Indian Center for Science and the Environment, in July. In fact, it was the first thing mentioned by everyone I spoke to, in India and Pakistan and elsewhere, when I mentioned the toll of the heat wave.
Heat is kind of an epistemological and epidemiological challenge for doctors and coroners, even in places where data collection is most conscientious. That’s because few deaths, even under the most extreme temperature conditions, clearly present as heat stress; usually fatalities occur when underlying conditions are aggravated or exacerbated by the additional strain.
Aditya Valiathan Pillai, an associate fellow at India’s Center for Policy Research, went to the emergency room “to see if the fact that nothing appeared in the media about people dying was true or if it was some kind of mortality, the way we’ve seen with Covid,” he said. “And generally I went to government hospitals and they said: we saw a steady increase in the number of people showing up, but very few deaths. Then they all raised their hands and said: we don’t really know how to count a heat death. So we’re not quite sure.”
Complete accounting of the heat wave’s toll requires “excess death data” — general accounting of how many people died in a given time period above a baseline average — but compiling it can take months, wherever the extreme event strikes. Without it, Baughman-McLeod said, “we don’t know how many because we don’t count properly. The data collection is not there – be it in India or in the US”
For his part, Somvanshi estimates that the final toll from these heat waves “will be at least twice what has been officially reported. But based on the information available, it will most likely be much more than double.” A simple doubling of data still yields a relatively low estimate; to even hit the 2015 toll in India, something like a 20-fold adjustment would be needed. To get to the death rates of the European heat waves, an even bigger adjustment.
Second, for mortality, humidity is extremely important.
“Moist heat is more dangerous to human health and well-being than dry heat,” Somvanshi said. During much of the heat wave, temperatures were shockingly high, but humidity was relatively low — making true wet-bulb readings relatively rare and brief, even through the sweltering hot spring.