The provided text accurately discusses the health impacts of extreme heat events and climate change. It highlights the challenges in accurately recording deaths attributed to heat stress, emphasizing the vulnerability of those exposed to heat due to their working conditions and lack of access to cooling devices. The article also sheds light on the dynamics of deadly heat, the importance of factoring in humidity and its effect on the body’s cooling mechanisms. The author draws a connection between climate change and human health, urging us to understand the existential crisis we face and take action to protect our planet and our well-being.The provided text accurately discusses the health impacts of extreme heat events and climate change. It highlights the challenges in accurately recording deaths attributed to heat stress, emphasizing the vulnerability of those exposed to heat due to their working conditions and lack of access to cooling devices. The article also sheds light on the dynamics of deadly heat, the importance of factoring in humidity and its effect on the body’s cooling mechanisms. The author draws a connection between climate change and human health, urging us to understand the existential crisis we face and take action to protect our planet and our well-being.
We know that climate change is changing the weather, which in turn is destroying lives and livelihoods. But what we don’t talk about enough is how these extreme weather events are affecting human health. In this season of desperation, when temperatures have risen beyond belief, we’ve learned how heat can kill. We’ve also learned how rising minimum temperatures — the nighttime heat — can be a killer. It’s critical that we connect the dots between what seems like a distant crisis of climate change and what it can do to our health.
This year, the world has seen scorching temperatures. And this heat has cost lives — in Delhi, it was estimated that around 270 people had died from extreme heat by the end of June. But I repeat this figure with caution. We don’t know how many people have died from heat alone, because heat is an exacerbating factor for existing health conditions such as heart disease or kidney disease. Many more may have succumbed to heat this summer, but doctors would have attributed it to underlying conditions. We know that the most vulnerable are those who are exposed to heat because of their working conditions — from construction workers to farmers. It is also the poor who have no access to electricity and cannot use devices to cool themselves down. But their deaths are not recorded as deaths from heat stress; only that they are poor or old and died from “unknown causes”. Heat is not on the country’s list of notifiable diseases, which also means that it does not have to be recorded or provided information for further action. So we have to acknowledge that we know little about the health burden and deaths from the severe fires we have seen recently.
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However, research is now pointing to the dynamics of deadly heat. First, it is understood that the rise in nighttime heat is driving the peak number of deaths. A 2022 article in The Lancet, a British medical journal, found “that the relative risk of death on days with warm nights may be 50 percent higher than on days with cooler nighttime temperatures.” The reason, the authors explain, is that heat interferes with sleep and does not allow the body to repair itself; and this in turn exacerbates health stress. Second, we know that evaporation is our body’s method of cooling; but this becomes ineffective when humidity rises above 75 percent—known as the wet-bulb phenomenon. So, thermal discomfort, not just temperatures, is what needs to be understood.
The concern is that we are seeing an upward trend in all three killers, particularly in urban centres. Here, temperatures are rising beyond human tolerance; humidity is increasing; and so is nighttime heat. A recent report by my colleagues at the Centre for Science and Environment tracked heat trends in major cities in India and found that ambient temperatures in cities have risen, compared with the national average. Hyderabad, Delhi, Mumbai, Kolkata and Chennai are seeing more humid summers — 5-10 per cent increases in the last decade (2014-23) compared with 2001-10. Only Bengaluru has not shown an increase in summer humidity, and this needs to be investigated further.
The report then concludes that cities do not cool down at night – across all climate zones. It notes that during the summers of the decade 2001-10, night temperatures fell by 6.2°-13.2° Celsius (across all cities) relative to the daytime peak. But in the last 10 summers, this difference between day and night temperatures (maximum and minimum) has narrowed. Hyderabad has fallen by 13 percent; Delhi by 9 percent; and Bengaluru by 15 percent. Kolkata, which already had the dubious distinction of a narrower difference between day and night temperatures, is now worse, due to higher humidity levels.
We know that this is all part of the double whammy we are seeing in our world. On the one hand, we have a warming planet — this year has broken all previous records for high temperatures. Worse, there are changes underway in the way the weather behaves in terms of erratic rainfall, intense heat, and shifts in wind patterns. All of which makes heat more stressful and deadly. On the other hand, our cities are seeing dramatic changes in their microclimates — the urban heat island effect is exacerbated as concrete takes over open and green spaces; and traffic and the use of energy for cooling add to the heat trapped in the air.
This summer has taught us new lessons about heat stress. The fact is that climate change will give us many such surprises in terms of impact on human health. Even now, this science is not understood. What climate change will do is bring the impact closer to our bodies and our health. Therefore, planetary health is about human health. It is time to make this connection. It is time to understand why climate change is an existential crisis; it is literally a matter of life and death.
The writer is at the Centre for Science and Environment [email protected], X: @sunitanar
