There is scientific consensus that 2023 was the hottest year ever in the planet’s recorded history. It will get progressively worse as this century sweats it out in a sauna of sweltering heat. Indeed, climate modellers forecasting the future say 2023 could be the coolest year in the memory of those born that year. As urbanisation increases, cities will grow at the expense of forests to become cauldrons of heat and humidity.

The consequences of climate change, mostly mediated through global warming, adversely affect human, animal and plant health in several ways: Direct effects of heat exposure on the body; extreme weather events; water scarcity; vector-borne and water-borne infections; non-communicable diseases (strokes; heart attacks; diabetes; respiratory disease; cancers); mental health disorders; food and nutrition insecurity due to reduced yield and nutrient quality of crops. Health systems, too, will face increased demand due to these and the movement of displaced climate refugees. They will also be affected by the adverse impact of extreme weather events on healthcare infrastructure, supply chains and personnel.

Of these myriad threats, heat waves are of immediate concern as summer advances across the Indian Subcontinent. While heat waves are defined both in terms of absolute temperatures recorded and relative rise in comparison to seasonal, “normal” values recorded in earlier years, it is not just the temperature that matters. A heat wave represents a combination of heat and humidity. At any level of heat, its impact on human body is amplified if humidity is high in the ambient air. The........

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